Science.gov

Sample records for low-mass protostellar systems

  1. The L723 Low-Mass Star Forming Protostellar System: Resolving a Double Core

    NASA Astrophysics Data System (ADS)

    Girart, J. M.; Rao, R.; Estalella, R.

    2009-03-01

    We present 1.35 mm Submillimeter Array (SMA) observations around the low-mass Class 0 source IRAS 19156+1906, at the center of the LDN 723 (L723) dark cloud. We detected emission from dust as well as emission from H2CO 30,3-20,2, DCN 3-2, and CN 2-1 lines, which arise from two cores, SMA 1 and SMA 2, separated by 2farcs9 (880 AU in projected distance). SMA 2 is associated with the previously detected source VLA 2. Weak SiO 5-4 emission is detected, possibly tracing a region of interaction between the dense envelope and the outflow. We modeled the dust and H2CO emission from the two cores. The results from the modeling show that the cores have similar physical properties (density and temperature distribution) but that SMA 2 has a larger p-H2CO abundance (by a factor of 3-10) than SMA 1. The p-H2CO abundances' findings are compatible with the value of the outer part of the circumstellar envelopes associated with Class 0 sources. SMA 2 is harboring an active multiple low-mass protostellar system and powering at least one molecular outflow. In contrast, there are no known signs of outflow activity toward SMA 1. This suggests that SMA 2 is more evolved than SMA 1. The kinematics of the two sources show marginal evidence of infall and rotation motions. The mass detected by the SMA observation, which trace scales of lsim1000 AU, is only a small fraction of the mass contained in the large-scale molecular envelope, which suggests that L723 is still in a very early phase of star formation. Despite the apparent quiescent nature of the L723, fragmentation is occurring at the center of the cloud at different scales. Thus, at sime1000 AU, the cloud has fragmented in two cores: SMA 1 and SMA 2. At the same time, at least one of these cores, SMA 2, has undergone additional fragmentation at scales of sime150 AU, forming a multiple stellar system.

  2. Methanol maps of low-mass protostellar systems. I. The Serpens molecular core

    NASA Astrophysics Data System (ADS)

    Kristensen, L. E.; van Dishoeck, E. F.; van Kempen, T. A.; Cuppen, H. M.; Brinch, C.; Jørgensen, J. K.; Hogerheijde, M. R.

    2010-06-01

    Context. Methanol has a rich rotational spectrum providing a large number of transitions at sub-millimetre wavelengths from a range of energy levels in one single telescope setting, thus making it a good tracer of physical conditions in star-forming regions. Furthermore, it is formed exclusively on grain surfaces and is therefore a clean tracer of surface chemistry. Aims: Determining the physical and chemical structure of low-mass, young stellar objects, in particular the abundance structure of CH3OH, to investigate where and how CH3OH forms and how it is eventually released back to the gas phase. Methods: Observations of the Serpens molecular core have been performed at the James Clerk Maxwell Telescope using the array receiver, Harp-B. Maps over a 4farcm5 × 5farcm4 region were made in a frequency window around 338 GHz, covering the 7K-6K transitions of methanol. Data are compared with physical models of each source based on existing sub-millimetre continuum data. Results: Methanol emission is extended over each source, following the column density of H2 but showing up also particularly strongly around outflows. The rotational temperature is low, 15-20 K, and does not vary with position within each source. None of the Serpens Class 0 sources show the high-K lines seen in several other Class 0 sources. The abundance is typically 10-9-10-8 with respect to H2 in the outer envelope, whereas “jumps” by factors of up to 102-103 inside the region where the dust temperature exceeds 100 K are not excluded. A factor of up to 103 enhancement is seen in outflow gas, consistent with previous studies. In one object, SMM4, the ice abundance has been measured to be 3 × 10-5 with respect to H2 in the outer envelope, i.e., a factor of 103 larger than the gas-phase abundance. Comparison with C18O J = 3-2 emission shows that strong CO depletion leads to a high gas-phase abundance of CH3OH not just for the Serpens sources, but also for a larger sample of deeply embedded

  3. VLA Ammonia Observations of IRAS 16253-2429: A Very Young and Low Mass Protostellar System

    NASA Technical Reports Server (NTRS)

    Wiseman, Jennifer J.

    2011-01-01

    IRAS l6253-2429. the source of the Wasp-Waist Nebula seen in Spitzer IRAC images, is an isolated very low luminosity ("VeLLO") Class 0 protostar in the nearby rho Ophiuchi cloud. We present VLA ammonia mapping observations of the dense gas envelope feeding the central core accreting system. We find a flattened envelope perpendicular to the outflow axis, and gas cavities that appear to cradle the outflow lobes as though carved out by the flow and associated (apparently precessing) jet. Based on the NH3 (1,1) and (2,2) emission distribution, we derive the mass, velocity fields and temperature distribution for the envelope. We discuss the combined evidence for this source as possibly one of the youngest and lowest mass sources in formation yet known.

  4. Chemistry in low-mass protostellar and protoplanetary regions.

    PubMed

    van Dishoeck, Ewine F

    2006-08-15

    When interstellar clouds collapse to form new stars and planets, the surrounding gas and dust become part of the infalling envelopes and rotating disks, thus providing the basic material from which new solar systems are formed. Instrumentation to probe the chemistry in low-mass star-forming regions has only recently become available. The results of a systematic program to study the abundances in solar-mass protostellar and protoplanetary regions are presented. Surveys at submillimeter and infrared wavelengths reveal a rich chemistry, including simple and complex (organic) gases, ices, polycyclic aromatic hydrocarbons, and silicates. Each of these species traces different aspects of the physical and chemical state of the objects as they evolve from deeply embedded protostars to pre-main sequence stars with planet-forming disks. Quantitative information on temperatures, densities, and abundances is obtained through molecular excitation and radiative transfer models as well as from analysis of solid-state line profiles. The chemical characteristics are dominated by freeze-out in the coldest regions and ice evaporation in the warmer zones. In the surface layers of disks, UV radiation controls the chemistry. The importance of complementary laboratory experiments and calculations to obtain basic molecular data is emphasized.

  5. Chemistry in low-mass protostellar and protoplanetary regions

    PubMed Central

    van Dishoeck, Ewine F.

    2006-01-01

    When interstellar clouds collapse to form new stars and planets, the surrounding gas and dust become part of the infalling envelopes and rotating disks, thus providing the basic material from which new solar systems are formed. Instrumentation to probe the chemistry in low-mass star-forming regions has only recently become available. The results of a systematic program to study the abundances in solar-mass protostellar and protoplanetary regions are presented. Surveys at submillimeter and infrared wavelengths reveal a rich chemistry, including simple and complex (organic) gases, ices, polycyclic aromatic hydrocarbons, and silicates. Each of these species traces different aspects of the physical and chemical state of the objects as they evolve from deeply embedded protostars to pre-main sequence stars with planet-forming disks. Quantitative information on temperatures, densities, and abundances is obtained through molecular excitation and radiative transfer models as well as from analysis of solid-state line profiles. The chemical characteristics are dominated by freeze-out in the coldest regions and ice evaporation in the warmer zones. In the surface layers of disks, UV radiation controls the chemistry. The importance of complementary laboratory experiments and calculations to obtain basic molecular data is emphasized. PMID:16894165

  6. Rotation and Outflow Motions in the Very Low-Mass Class 0 Protostellar System HH 211 at Subarcsecond Resolution

    NASA Astrophysics Data System (ADS)

    Lee, Chin-Fei; Hirano, Naomi; Palau, Aina; Ho, Paul T. P.; Bourke, Tyler L.; Zhang, Qizhou; Shang, Hsien

    2009-07-01

    HH 211 is a nearby young protostellar system with a highly collimated jet. We have mapped it in 352 GHz continuum, SiO (J = 8 - 7), and HCO+ (J = 4 - 3) emission at up to ~0farcs2 resolution with the Submillimeter Array (SMA). The continuum source is now resolved into two sources, SMM1 and SMM2, with a separation of ~ 84 AU. SMM1 is seen at the center of the jet, probably tracing a (inner) dusty disk around the protostar driving the jet. SMM2 is seen to the southwest of SMM1 and may trace an envelope-disk around a small binary companion. A flattened envelope-disk is seen in HCO+ around SMM1 with a radius of ~ 80 AU perpendicular to the jet axis. Its velocity structure is consistent with a rotation motion and can be fitted with a Keplerian law that yields a mass of ~50 ± 15 M Jup (a mass of a brown dwarf) for the protostar. Thus, the protostar could be the lowest mass source known to have a collimated jet and a rotating flattened envelope-disk. A small-scale (~200 AU) low-speed (~2 km s-1) outflow is seen in HCO+ around the jet axis extending from the envelope-disk. It seems to rotate in the same direction as the envelope-disk and may carry away part of the angular momentum from the envelope-disk. The jet is seen in SiO close to ~100 AU from SMM1. It is seen with a "C-shaped" bending. It has a transverse width of lsim 40 AU and a velocity of ~ 170 ± 60 km s-1. A possible velocity gradient is seen consistently across its innermost pair of knots, ~0.5 km s-1 at ~10 AU, consistent with the sense of rotation of the envelope-disk. If this gradient is an upper limit of the true rotational gradient of the jet, then the jet carries away a very small amount of angular momentum of lsim 5 AU km s-1 and thus must be launched from the very inner edge of the disk near the corotation radius.

  7. 2MASS J17112318-2724315: A DEEPLY EMBEDDED LOW-MASS PROTOSTELLAR SYSTEM IN THE B59 MOLECULAR CLOUD

    SciTech Connect

    Riaz, B.; Martin, E. L.; Bouy, H.; Tata, R.

    2009-08-01

    We present near-infrared observations of the low-mass deeply embedded Class 0/I system 2MASS J17112318-2724315 (2M171123) in the B59 molecular cloud. Bright scattered light nebulosity is observed toward this source in the K{sub s} images, that seems to trace the edges of an outflow cavity. We report the detection of a low-luminosity protostar 2M17112255-27243448 (2M17112255) that lies {approx}8'' ({approx}1000 AU) from 2M171123. This is a Class I system, as indicated by its 2-8 {mu}m slope and Infrared Array Camera colors, with an estimated internal luminosity of {approx}0.3 L{sub sun}. We estimate a mass of {approx}0.12-0.25 M{sub sun} for this source, at an age of 0.1-1 Myr. Also presented is detailed modeling of the 2M171123 system. The best-fit parameters indicate a large envelope density of the order of {approx}10{sup -13} g cm{sup -3}, and an intermediate inclination between 53 deg. and 59 deg. The observed K{sub s} -band variability for this system could be explained by slight variability in the mass infall rate between 2.5E-5 and 1.8E-5 M{sub sun} yr{sup -1}. The protostar 2M171123 exhibits a rarely observed absorption feature near 11.3 {mu}m within its 10 {mu}m silicate band. We find a strong correlation between the strength in this 11.3 {mu}m 'edge' and the H{sub 2}O-ice column density, indicating the origin of this feature in the thickness of the ice mantle over the silicate grains.

  8. Observations of Deuterated Species toward Low-Mass Prestellar and Protostellar Cores

    NASA Astrophysics Data System (ADS)

    Nishimura, Y.; Sakai, N.; Watanabe, Y.; Sakai, T.; Hirota, T.; Yamamoto, S.

    2013-10-01

    We have conducted observations of the ground-state transition lines (J = 1-0) of the fundamental deuterated species DCO+, DNC, DCN, CCD and N2D+ as well as those of H13CO+, HN13C, H13CN, CCH and N2H+ with the Nobeyama 45 m telescope. The target sources are the cold starless cores, TMC-1 and Lupus-1A, and the low-mass star forming cores, L1527 and IRAS15398-3359. The excitation temperatures derived from intensities of resolved hyperfine components are systematically different between DNC and HN13C. On the other hand, the excitation temperatures of DCN and H13CN are comparable to each other. Although the origin of these results is puzzling, the present result indicates that accurate evaluation of the excitation temperature is essential for deriving deuterium fractionation ratios accurately.

  9. The Herschel HIFI water line survey in the low-mass proto-stellar outflow L1448

    NASA Astrophysics Data System (ADS)

    Santangelo, G.; Nisini, B.; Giannini, T.; Antoniucci, S.; Vasta, M.; Codella, C.; Lorenzani, A.; Tafalla, M.; Liseau, R.; van Dishoeck, E. F.; Kristensen, L. E.

    2012-02-01

    Aims: As part of the WISH (Water In Star-forming regions with Herschel) key project, systematic observations of H2O transitions in young outflows are being carried out with the aim of understanding the role of water in shock chemistry and its physical and dynamical properties. We report on the observations of several ortho- and para-H2O lines performed with the HIFI instrument toward two bright shock spots (R4 and B2) along the outflow driven by the L1448 low-mass proto-stellar system, located in the Perseus cloud. These data are used to identify the physical conditions giving rise to the H2O emission and to infer any dependence on velocity. Methods: We used a large velocity gradient (LVG) analysis to derive the main physical parameters of the emitting regions, namely n(H2), Tkin, N(H2O) and emitting-region size. We compared these with other main shock tracers, such as CO, SiO and H2 and with shock models available in the literature. Results: These observations provide evidence that the observed water lines probe a warm (Tkin ~ 400-600 K) and very dense (n ~ 106-107 cm-3) gas that is not traced by other molecules, such as low-J CO and SiO, but is traced by mid-IR H2 emission. In particular, H2O shows strong differences with SiO in the excitation conditions and in the line profiles in the two observed shocked positions, pointing to chemical variations across the various velocity regimes and chemical evolution in the different shock spots. Physical and kinematical differences can be seen at the two shocked positions. At the R4 position, two velocity components with different excitation can be distinguished, of which the component at higher velocity (R4-HV) is less extended and less dense than the low velocity component (R4-LV). H2O column densities of about 2 × 1013 and 4 × 1014 cm-2 were derived for the R4-LV and the R4-HV components, respectively. The conditions inferred for the B2 position are similar to those of the R4-HV component, with H2O column density in

  10. Orbital Motions in Binary Protostellar Systems

    NASA Astrophysics Data System (ADS)

    Rodríguez, L. F.

    2004-08-01

    Using high-resolution ( ˜ 0to z @. hss ''1), multi-epoch Very Large Array observations, we have detected orbital motions in several low-luminosity protobinary systems in the Taurus and ρ Ophiuchus molecular complexes. The masses obtained from Kepler's third law are of the order of 0.5 to 2 M⊙, as expected for such low-mass protostars. The relatively large bolometric luminosities of these young systems corroborates the notion that protostars obtain most of their luminosity from accretion and not from nuclear reactions. In addition, in one of the sources studied (a multiple system in Taurus), a low-mass young star has shown a drastic change in its orbit after a close approach with another component of the system, presumed to be a double star. The large proper motion achieved by this low mass protostar (20 km s-1), suggests an ejection from the system.

  11. Water and methanol in low-mass protostellar outflows: gas-phase synthesis, ice sputtering and destruction

    NASA Astrophysics Data System (ADS)

    Suutarinen, A. N.; Kristensen, L. E.; Mottram, J. C.; Fraser, H. J.; van Dishoeck, E. F.

    2014-05-01

    Water in outflows from protostars originates either as a result of gas-phase synthesis from atomic oxygen at T ≳ 200 K, or from sputtered ice mantles containing water ice. We aim to quantify the contribution of the two mechanisms that lead to water in outflows, by comparing observations of gas-phase water to methanol (a grain surface product) towards three low-mass protostars in NGC 1333. In doing so, we also quantify the amount of methanol destroyed in outflows. To do this, we make use of James Clerk Maxwell Telescope and Herschel-Heterodyne Instrument for the Far-Infrared data of H2O, CH3OH and CO emission lines and compare them to RADEX non-local thermodynamic equilibrium excitation simulations. We find up to one order of magnitude decrease in the column density ratio of CH3OH over H2O as the velocity increases in the line wings up to ˜15 km s-1. An independent decrease in X(CH3OH) with respect to CO of up to one order of magnitude is also found in these objects. We conclude that gas-phase formation of H2O must be active at high velocities (above 10 km s-1 relative to the source velocity) to re-form the water destroyed during sputtering. In addition, the transition from sputtered water at low velocities to form water at high velocities must be gradual. We place an upper limit of two orders of magnitude on the destruction of methanol by sputtering effects.

  12. Low-Mass, Low-Power Hall Thruster System

    NASA Technical Reports Server (NTRS)

    Pote, Bruce

    2015-01-01

    NASA is developing an electric propulsion system capable of producing 20 mN thrust with input power up to 1,000 W and specific impulse ranging from 1,600 to 3,500 seconds. The key technical challenge is the target mass of 1 kg for the thruster and 2 kg for the power processing unit (PPU). In Phase I, Busek Company, Inc., developed an overall subsystem design for the thruster/cathode, PPU, and xenon feed system. This project demonstrated the feasibility of a low-mass power processing architecture that replaces four of the DC-DC converters of a typical PPU with a single multifunctional converter and a low-mass Hall thruster design employing permanent magnets. In Phase II, the team developed an engineering prototype model of its low-mass BHT-600 Hall thruster system, with the primary focus on the low-mass PPU and thruster. The goal was to develop an electric propulsion thruster with the appropriate specific impulse and propellant throughput to enable radioisotope electric propulsion (REP). This is important because REP offers the benefits of nuclear electric propulsion without the need for an excessively large spacecraft and power system.

  13. ENVIRONMENT AND PROTOSTELLAR EVOLUTION

    SciTech Connect

    Zhang, Yichen; Tan, Jonathan C.

    2015-04-01

    Even today in our Galaxy, stars form from gas cores in a variety of environments, which may affect the properties of the resulting star and planetary systems. Here, we study the role of pressure, parameterized via ambient clump mass surface density, on protostellar evolution and appearance, focusing on low-mass Sun-like stars and considering a range of conditions from relatively low pressure filaments in Taurus, to intermediate pressures of cluster-forming clumps like the Orion Nebula Cluster, to very high pressures that may be found in the densest infrared dark clouds or in the Galactic center. We present unified analytic and numerical models for the collapse of prestellar cores, accretion disks, protostellar evolution, and bipolar outflows, coupled with radiative transfer calculations and a simple astrochemical model to predict CO gas-phase abundances. Prestellar cores in high-pressure environments are smaller and denser and thus collapse with higher accretion rates and efficiencies, resulting in higher luminosity protostars with more powerful outflows. The protostellar envelope is heated to warmer temperatures, affecting infrared morphologies (and thus classification) and astrochemical processes like CO depletion onto dust grain ice mantles (and thus CO morphologies). These results have general implications for star and planet formation, especially via their effect on astrochemical and dust grain evolution during infall to and through protostellar accretion disks.

  14. Low-Mass Inflation Systems for Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Thunnissen, Daniel P.; Webster, Mark S.; Engelbrecht, Carl S.

    1995-01-01

    The use of inflatable space structures has often been proposed for aerospace and planetary applications. Communication, power generation, and very-long-baseline interferometry are just three potential applications of inflatable technology. The success of inflatable structures depends on the development of an applications of inflatable technology. This paper describes two design studies performed to develop a low mass inflation system. The first study takes advantage of existing onboard propulsion gases to reduce the overall system mass. The second study assumes that there is no onboard propulsion system. Both studies employ advanced components developed for the Pluto fast flyby spacecraft to further reduce mass. The study examined four different types of systems: hydrazine, nitrogen and water, nitrogen, and xenon. This study shows that all of these systems can be built for a small space structure with masses lower than 0.5 kilograms.

  15. The low mass ratio contact binary system V728 Herculis

    NASA Astrophysics Data System (ADS)

    Erkan, N.; Ulaş, B.

    2016-07-01

    We present the orbital period study and the photometric analysis of the contact binary system V728 Her. Our orbital period analysis shows that the period of the system increases (dP / dt = 1.92 ×10-7 dyr-1) and the mass transfer rate from the less massive component to more massive one is 2.51 ×10-8 M⊙y-1 . In addition, an advanced sinusoidal variation in period can be attributed to the light-time effect by a tertiary component or the Applegate mechanism triggered by the secondary component. The simultaneous multicolor BVR light and radial velocity curves solution indicates that the physical parameters of the system are M1 = 1.8M⊙ , M2 = 0.28M⊙ , R1 = 1.87R⊙ , R2 = 0.82R⊙ , L1 = 5.9L⊙ , and L2 = 1.2L⊙ . We discuss the evolutionary status and conclude that V728 Her is a deep (f = 81%), low mass ratio (q = 0.16) contact binary system.

  16. Water in star-forming regions with Herschel (WISH). V. The physical conditions in low-mass protostellar outflows revealed by multi-transition water observations

    NASA Astrophysics Data System (ADS)

    Mottram, J. C.; Kristensen, L. E.; van Dishoeck, E. F.; Bruderer, S.; San José-García, I.; Karska, A.; Visser, R.; Santangelo, G.; Benz, A. O.; Bergin, E. A.; Caselli, P.; Herpin, F.; Hogerheijde, M. R.; Johnstone, D.; van Kempen, T. A.; Liseau, R.; Nisini, B.; Tafalla, M.; van der Tak, F. F. S.; Wyrowski, F.

    2014-12-01

    Context. Outflows are an important part of the star formation process as both the result of ongoing active accretion and one of the main sources of mechanical feedback on small scales. Water is the ideal tracer of these effects because it is present in high abundance for the conditions expected in various parts of the protostar, particularly the outflow. Aims: We constrain and quantify the physical conditions probed by water in the outflow-jet system for Class 0 and I sources. Methods: We present velocity-resolved Herschel HIFI spectra of multiple water-transitions observed towards 29 nearby Class 0/I protostars as part of the WISH guaranteed time key programme. The lines are decomposed into different Gaussian components, with each component related to one of three parts of the protostellar system; quiescent envelope, cavity shock and spot shocks in the jet and at the base of the outflow. We then use non-LTE radex models to constrain the excitation conditions present in the two outflow-related components. Results: Water emission at the source position is optically thick but effectively thin, with line ratios that do not vary with velocity, in contrast to CO. The physical conditions of the cavity and spot shocks are similar, with post-shock H2 densities of order 105 - 108 cm-3 and H2O column densities of order 1016 - 1018 cm-2. H2O emission originates in compact emitting regions: for the spot shocks these correspond to point sources with radii of order 10-200 AU, while for the cavity shocks these come from a thin layer along the outflow cavity wall with thickness of order 1-30 AU. Conclusions: Water emission at the source position traces two distinct kinematic components in the outflow; J shocks at the base of the outflow or in the jet, and C shocks in a thin layer in the cavity wall. The similarity of the physical conditions is in contrast to off-source determinations which show similar densities but lower column densities and larger filling factors. We propose

  17. Low-Mass Materials and Vertex Detector Systems

    SciTech Connect

    Cooper, William E.

    2014-01-01

    Physics requirements set the material budget and the precision and sta bility necessary in low - mass vertex detector sy s tems . Operational considerations, along with physics requirements , set the operating environment to be provided and determine the heat to be removed. Representative materials for fulfilling those requirements are described and properties of the materials are tabulated. A figure of merit is proposed to aid in material selection. Multi - layer structures are examined as a method to allow material to be used effectively, thereby reducing material contributions. Fin ally, comments are made on future directions to be considered in using present materials effectively and in developing new materials.

  18. Low Mass Ratio Contact Binary Systems HN UMa and II UMa - III

    NASA Astrophysics Data System (ADS)

    Lee, Woo-Baik; Kim, Ho-Il; Kang, Young Woon; Oh, Kyu-Dong

    2006-09-01

    We present newly observed BVRI CCD light curves for low mass ratio contact binaries, HN UMa and II UMa. The absolute dimensions of these objects were obtained by applying the Wilson-Devinney program to previously published spectroscopic analysis and to our observed photometric data. The evolutionary status of all 21 low mass ratio contact binary system including HN UMa and II UMa was then considered. The secondaries of all low mass ratio contact binaries are located below the zero age main sequence in HR diagram. This phenomenon could be explained by mass loss from the secondary component in the low mass contact binary system because even small mass loss affects luminosity decrease in the low mass stars.

  19. AGC 226067: A possible interacting low-mass system

    NASA Astrophysics Data System (ADS)

    Adams, E. A. K.; Cannon, J. M.; Rhode, K. L.; Janesh, W. F.; Janowiecki, S.; Leisman, L.; Giovanelli, R.; Haynes, M. P.; Oosterloo, T. A.; Salzer, J. J.; Zaidi, T.

    2015-08-01

    We present Arecibo, GBT, VLA, and WIYN/pODI observations of the ALFALFA source AGC 226067. Originally identified as an ultra-compact high velocity cloud and candidate Local Group galaxy, AGC 226067 is spatially and kinematically coincident with the Virgo cluster, and the identification by multiple groups of an optical counterpart with no resolved stars supports the interpretation that this systems lies at the Virgo distance (D = 17 Mpc). The combined observations reveal that the system consists of multiple components: a central H i source associated with the optical counterpart (AGC 226067), a smaller H i-only component (AGC 229490), a second optical component (AGC 229491), and extended low-surface brightness H i. Only ~1/4 of the single-dish H i emission is associated with AGC 226067; as a result, we find MHI/Lg ~ 6M⊙/L⊙ which is lower than previous work. At D = 17 Mpc, AGC 226067 has an H i mass of 1.5 × 107M⊙ and Lg = 2.4 × 106L⊙, AGC 229490 (the H i-only component) has MHI = 3.6 × 106M⊙, and AGC 229491 (the second optical component) has Lg = 3.6 × 105L⊙. The nature of this system of three sources is uncertain: AGC 226067 and AGC 229490 may be connected by an H i bridge, and AGC 229490 and AGC 229491 are separated by only 0.5'. The current data do not resolve the H i in AGC 229490 and its origin is unclear. We discuss possible scenarios for this system of objects: an interacting system of dwarf galaxies, accretion of material onto AGC 226067, or stripping of material from AGC 226067.

  20. Do siblings always form and evolve simultaneously? Testing the coevality of multiple protostellar systems through SEDs

    NASA Astrophysics Data System (ADS)

    Murillo, N. M.; van Dishoeck, E. F.; Tobin, J. J.; Fedele, D.

    2016-07-01

    Context. Multiplicity is common in field stars and among protostellar systems. Models suggest two paths of formation: turbulent fragmentation and protostellar disk fragmentation. Aims: We attempt to find whether or not the coevality frequency of multiple protostellar systems can help to better understand their formation mechanism. The coevality frequency is determined by constraining the relative evolutionary stages of the components in a multiple system. Methods: Spectral energy distributions (SEDs) for known multiple protostars in Perseus were constructed from literature data. Herschel PACS photometric maps were used to sample the peak of the SED for systems with separations ≥7″, a crucial aspect in determining the evolutionary stage of a protostellar system. Inclination effects and the surrounding envelope and outflows were considered to decouple source geometry from evolution. This together with the shape and derived properties from the SED was used to determine each system's coevality as accurately as possible. SED models were used to examine the frequency of non-coevality that is due to geometry. Results: We find a non-coevality frequency of 33 ± 10% from the comparison of SED shapes of resolved multiple systems. Other source parameters suggest a somewhat lower frequency of non-coevality. The frequency of apparent non-coevality that is due to random inclination angle pairings of model SEDs is 17 ± 0.5%. Observations of the outflow of resolved multiple systems do not suggest significant misalignments within multiple systems. Effects of unresolved multiples on the SED shape are also investigated. Conclusions: We find that one-third of the multiple protostellar systems sampled here are non-coeval, which is more than expected from random geometric orientations. The other two-thirds are found to be coeval. Higher order multiples show a tendency to be non-coeval. The frequency of non-coevality found here is most likely due to formation and enhanced by

  1. Southern Very Low Mass Stars and Brown Dwarfs in Wide Binary and Multiple Systems

    NASA Astrophysics Data System (ADS)

    Caballero, José Antonio

    2007-09-01

    The results of the Königstuhl survey in the Southern Hemisphere are presented. I have searched for common proper motion companions to 173 field very low mass stars and brown dwarfs with spectral types >M5.0 V and magnitudes J<~14.5 mag. I have measured for the first time the common proper motion of two new wide systems containing very low mass components, Königstuhl 2 AB and 3 A-BC. Together with Königstuhl 1 AB and 2M 0126-50 AB, they are among the widest systems in their respective classes (r=450-11,900 AU). I have determined the minimum frequency of field wide multiples (r>100 AU) with late-type components at 5.0%+/-1.8% and the frequency of field wide late-type binaries with mass ratios q>0.5 at 1.2%+/-0.9%. These values represent a key diagnostic of evolution history and low-mass star and brown dwarf formation scenarios. In addition, the proper motions of 62 field very low mass dwarfs are measured here for the first time.

  2. Using K2 to Investigate Planetary Systems Orbiting Low-Mass Stars

    NASA Astrophysics Data System (ADS)

    Dressing, Courtney D.; Newton, Elisabeth R.; Charbonneau, David; Schlieder, Joshua E.; K2 CHAI Consortium

    2016-10-01

    The NASA K2 mission is using the repurposed Kepler spacecraft to search for transiting planets in multiple fields along the ecliptic plane. Unlike the original Kepler mission, which stared at a single region of the sky for four years, K2 observes each field for a much shorter timespan of roughly 80 days. While planets in the habitable zones of Sun-like stars would be unlikely to transit even once during an 80-day interval, planets in the habitable zones of faint low-mass stars have much shorter orbital periods and may even transit multiple times during a single K2 campaign. Accordingly, M and K dwarfs are frequently nominated as K2 Guest Observer targets and K2 has already observed significantly more low-mass stars than the original Kepler mission. While the K2 data are therefore an enticing resource for studying the properties and frequency of planetary systems orbiting low-mass stars, many K2 target stars are not well-characterized and some candidate low-mass stars are actually giants or reddened Sun-like stars. We are improving the characterization of K2 planetary systems orbiting low-mass stars by using SpeX on the NASA Infrared Telescope Facility and TripleSpec on the 200-inch Hale Telescope at Palomar Observatory to acquire near-infrared spectra of K2 target stars. We then employ empirically-based relations to determine the temperatures, radii, luminosities, and metallicities of K2 planet candidate host stars. Refining the stellar parameters allows us to identify astrophysical false positives and better constrain the radii and insolation flux environments of bona fide transiting planets. I will present our resulting catalog of stellar properties and discuss the prospects for using K2 data to investigate whether planet occurrence rates for mid-M dwarfs are similar to those for early-M and late-K dwarfs.

  3. The Wasp-Waist Nebula: VLA Ammonia Observations of the Molecular Core Envelope In a Unique Class 0 Protostellar System

    NASA Technical Reports Server (NTRS)

    Wiseman, Jennifer

    2010-01-01

    The Wasp-Waist Nebula was discovered in the IRAC c2d survey of the Ophiuchus starforming clouds. It is powered by a well-isolated, low-luminosity, low-mass Class 0 object. Its weak outflow has been mapped in the CO (3-2) transition with the JCMT, in 2.12 micron H2 emission with WIRC (the Wide-Field Infrared Camera) on the Hale 5-meter, and, most recently, in six H2 mid-infrared lines with the IRS (InfraRed Spectrograph) on-board the Spitzer Space Telescope; possible jet twisting structure may be evidence of unique core dynamics. Here, we report results of recent VLA ammonia mapping observations of the dense gas envelope feeding the central core protostellar system. We describe the morphology, kinematics, and angular momentum characteristics of this unique system. The results are compared with the envelope structure deduced from IRAC 8-micron absorption of the PAH (polycyclic aromatic hydrocarbon) background emission from the cloud.

  4. The Infrared Reflection Nebula Around the Protostellar System in S140

    NASA Technical Reports Server (NTRS)

    Harker, D.; Bregman, J.; Tielens, A. G. G. M.; Temi, P.; Rank, D.; Morrison, David (Technical Monitor)

    1994-01-01

    We have studied the protostellar system in S140 at 2.2, 3.1 and 3.45 microns using a 128x128 InSb array at the Lick Observatory 3m telescope. Besides the protostellar sources, the data reveal a bright infrared reflection nebula. We have developed a simple model of this region and derived the physical conditions. IRSI is surrounded by a dense dusty disk viewed almost edge-on. Photons leaking out through the poles illuminate almost directly north and south the inner edge of a surrounding shell of molecular gas, Analysis of the observed colors and intensities of the NIR light, using Mie scattering theory, reveal that the dust grains in the molecular cloud are somewhat larger than in the general diffuse interstellar medium. Moreover, the incident light has a "cool" color temperature, approximately equals 800K, and likely originates from a dust photosphere close to the protostar. Finally, we find little H2O ice associated with the dusty disk around IRSI. Most of the 3.1 micron ice extinction arises instead from cool intervening molecular cloud material. We have compared our infrared dust observations with millimeter and radio observations of molecular gas associated with this region. The large scale structure observable in the molecular gas is indicative of the interaction between the protostellar wind and the surrounding molecular cloud rather than the geometry of the protostellar disk. We conclude that S140 is a young blister formed by this outflow on the side of a molecular cloud and viewed edge-on.

  5. Keplerian Circumbinary Disk and Accretion Streams around the Protostellar Binary System L1551 NE

    NASA Astrophysics Data System (ADS)

    Takakuwa, S.; Saito, M.; Lim, J.; Saigo, K.; Hanawa, T.; Matsumoto, T.

    2013-10-01

    We show our recent observational results of L1551 NE, an archetypal binary protostellar system, in the 0.9-mm dust continuum emission and the C18O (J=3-2) emission with the SubMillimeter Array (SMA). The SMA results show firm evidence for a Keplerian circumbinary disk, circumstellar disks, and an inner clearing in the circumbinary disk, in L1551 NE. We demonstrate that future observations of L1551 NE with Atacama Large Millimeter and submillimeter Array (ALMA) have the potential to unveil the theoretically-predicted “accretion streams” that channel material from the circumbinary disk to the individual circumstellar disks.

  6. Protostellar Outflows

    NASA Astrophysics Data System (ADS)

    Bally, John

    2016-09-01

    Outflows from accreting, rotating, and magnetized systems are ubiquitous. Protostellar outflows can be observed from radio to X-ray wavelengths in the continuum and a multitude of spectral lines that probe a wide range of physical conditions, chemical phases, radial velocities, and proper motions. Wide-field visual and near-IR data, mid-IR observations from space, and aperture synthesis with centimeter- and millimeterwave interferometers are revolutionizing outflow studies. Many outflows originate in multiple systems and clusters. Although most flows are bipolar and some contain highly collimated jets, others are wide-angle winds, and a few are nearly isotropic and exhibit explosive behavior. Morphologies and velocity fields indicate variations in ejection velocity, mass-loss rate, and in some cases, flow orientation and degree of collimation. These trends indicate that stellar accretion is episodic and often occurs in a complex dynamical environment. Outflow power increases with source luminosity but decreases with evolutionary stage. The youngest outflows are small and best traced by molecules such as CO, SiO, H2O, and H2. Older outflows can grow to parsec scales and are best traced by shock-excited atoms and ions such as hydrogen-recombination lines, [Sii], and [Oii]. Outflows inject momentum and energy into their surroundings and provide an important mechanism in the self-regulation of star formation. However, momentum injection rates remain uncertain with estimates providing lower bounds.

  7. The physical parameters of the low-mass multiple system LHS1070 from Spectral synthesis analysis

    NASA Astrophysics Data System (ADS)

    Rajpurohit, A. S.; Reylé, C.; Schultheis, M.; Leinert, C.; Allard, F.

    2011-12-01

    LHS1070 is a nearby multiple systems of low mass stars. It is an important source of information for probing the low mass end of the main sequence, down to the hydrogen-burning limit. The primary of the system consist of a mid-M dwarf and two components are late-M to L dwarf, at the star-brown dwarf transition. It makes it even more valuable to understand the formation of dust in cool stellar atmospheres.This work aims to determine the fundamental parameters of LHS1070 and to test recent model atmospheres.We compared the well calibrated data in the optical and infra-red with synthetic spectra computed from recent cool stars atmosphere models. We derived the physical parameters T_{eff}, radius and log g for three components of LHS1070. The models which include the formation and settle of dust are able to reproduce and describe the main features of the visible to IR spectra of the components.

  8. DISCOVERY OF A BRIGHT, EXTREMELY LOW MASS WHITE DWARF IN A CLOSE DOUBLE DEGENERATE SYSTEM

    SciTech Connect

    Vennes, S.; Kawka, A.; Nemeth, P.; Thorstensen, J. R.; Skinner, J. N.; Pigulski, A.; Steslicki, M.; Kolaczkowski, Z.; Srodka, P.

    2011-08-10

    We report the discovery of a bright (V {approx} 13.7), extremely low mass white dwarf in a close double degenerate system. We originally selected GALEX J171708.5+675712 for spectroscopic follow-up among a group of white dwarf candidates in an ultraviolet-optical reduced proper-motion diagram. The new white dwarf has a mass of 0.18 M{sub sun} and is the primary component of a close double degenerate system (P = 0.246137 days, K{sub 1} = 288 km s{sup -1}) comprising a fainter white dwarf secondary with M{sub 2} {approx} 0.9 M{sub sun}. Light curves phased with the orbital ephemeris show evidence of relativistic beaming and weaker ellipsoidal variations. The light curves also reveal secondary eclipses (depth {approx}8 mmag) while the primary eclipses appear partially compensated by the secondary gravitational deflection and are below detection limits. Photospheric abundance measurements show a nearly solar composition of Si, Ca, and Fe (0.1-1 sun), while the normal kinematics suggest a relatively recent formation history. Close binary evolutionary scenarios suggest that extremely low mass white dwarfs form via a common-envelope phase and possible Roche lobe overflow.

  9. Formation of Black Hole Low-mass X-Ray Binaries in Hierarchical Triple Systems

    NASA Astrophysics Data System (ADS)

    Naoz, Smadar; Fragos, Tassos; Geller, Aaron; Stephan, Alexander P.; Rasio, Frederic A.

    2016-05-01

    The formation of black hole (BH) low-mass X-ray binaries (LMXB) poses a theoretical challenge, as low-mass companions are not expected to survive the common-envelope scenario with the BH progenitor. Here we propose a formation mechanism that skips the common-envelope scenario and relies on triple-body dynamics. We study the evolution of hierarchical triples following the secular dynamical evolution up to the octupole-level of approximation, including general relativity, tidal effects, and post-main-sequence evolution such as mass loss, changes to stellar radii, and supernovae. During the dynamical evolution of the triple system the “eccentric Kozai-Lidov” mechanism can cause large eccentricity excitations in the LMXB progenitor, resulting in three main BH-LMXB formation channels. Here we define BH-LMXB candidates as systems where the inner BH-companion star crosses its Roche limit. In the “eccentric” channel (˜81% of the LMXBs in our simulations) the donor star crosses its Roche limit during an extreme eccentricity excitation while still on a wide orbit. Second, we find a “giant” LMXB channel (˜11%), where a system undergoes only moderate eccentricity excitations but the donor star fills its Roche-lobe after evolving toward the giant branch. Third, we identify a “classical” channel (˜8%), where tidal forces and magnetic braking shrink and circularize the orbit to short periods, triggering mass-transfer. Finally, for the giant channel we predict an eccentric (˜0.3-0.6) preferably inclined (˜40°, ˜140°) tertiary, typically on a wide enough orbit (˜104 au) to potentially become unbound later in the triple evolution. While this initial study considers only one representative system and neglects BH natal kicks, we expect our scenario to apply across a broad region of parameter space for triple-star systems.

  10. Deep, Low Mass Ratio Overcontact Binary Systems. XI. V1191 Cygni

    NASA Astrophysics Data System (ADS)

    Zhu, L. Y.; Qian, S. B.; Soonthornthum, B.; He, J. J.; Liu, L.

    2011-10-01

    Complete CCD photometric light curves in BV(RI) c bands obtained on one night in 2009 for the short-period close-binary system V1191 Cygni are presented. A new photometric analysis with the 2003 version of the Wilson-Van Hamme code shows that V1191 Cyg is a W-type overcontact binary system and suggests that it has a high degree of overcontact (f = 68.6%) with very low mass ratio, implying that it is at the late stage of overcontact evolution. The absolute parameters of V1191 Cyg are derived using spectroscopic and photometric solutions. Combining new determined times of light minimum with others published in the literature, the period change of the binary star is investigated. A periodic variation, with a period of 26.7 years and an amplitude of 0.023 days, was discovered to be superimposed on a long-term period increase (dP/dt = +4.5(± 0.1) × 10-7 days yr-1). The cyclic period oscillation may be caused by the magnetic activity cycles of either of the components or the light-time effect due to the presence of a third body with a mass of m 3 = 0.77 M sun and an orbital radius of a 3 = 7.6 AU, when this body is coplanar to the orbit of the eclipsing pair. The secular orbital period increase can be interpreted as a mass transfer from the less massive component to the more massive one. With the period increases, V1191 Cyg will evolve from its present low mass ratio, high filled overcontact state to a rapidly rotating single star when its orbital angular momentum is less than three times the total spin angular momentum. V1191 Cyg is too blue for its orbital period and it is an unusual W-type overcontact system with such a low mass ratio and high fill-out overcontact configuration, which is worth monitoring continuously in the future.

  11. ASAS J083241+2332.4: A New Extreme Low Mass Ratio Overcontact Binary System

    NASA Astrophysics Data System (ADS)

    Sriram, K.; Malu, S.; Choi, C. S.; Vivekananda Rao, P.

    2016-03-01

    We present the R- and V-band CCD photometry and Hα line studies of an overcontact binary ASAS J083241+2332.4. The light curves exhibit totality along with a trace of the O’Connell effect. The photometric solution indicates that this system falls into the category of extreme low-mass ratio overcontact binaries with a mass ratio, q ˜ 0.06. Although a trace of the O’ Connell effect is observed, constancy of the Hα line along various phases suggest that a relatively higher magnetic activity is needed for it to show a prominent fill-in effect. The study of O-C variations reveals that the period of the binary shows a secular increase at the rate of dP/dt ˜ 0.0765 s years-1, which is superimposed by a low, but significant, sinusoidal modulation with a period of ˜8.25 years. Assuming that the sinusoidal variation is due to the presence of a third body, orbital elements have been derived. There exist three other similar systems, SX Crv, V857 Her, and E53, which have extremely low mass ratios and we conclude that ASAS J083241+2332.4 resembles SX Crv in many respects. Theoretical studies indicate that at a critical mass ratio range, qcritical = 0.07-0.09, overcontact binaries should merge and form a fast rotating star, but it has been suggested that qcritical can continue to fall up to 0.05 depending on the primary's mass and structure. Moreover, the obtained fill-out factors (50%-70%) indicate that mass loss is considerable and hydrodynamical simulations advocate that mass loss from L2 is mandatory for a successful merging process. Comprehensively, the results indicate that ASAS J083241+2332.4 is at a stage of merger. The pivotal role played by the subtle nature of the derived mass ratio in forming a rapidly rotating star has been discussed.

  12. Discovery and Characterization of Wide Binary Systems with a Very Low Mass Component

    NASA Astrophysics Data System (ADS)

    Baron, Frédérique; Lafrenière, David; Artigau, Étienne; Doyon, René; Gagné, Jonathan; Davison, Cassy L.; Malo, Lison; Robert, Jasmin; Nadeau, Daniel; Reylé, Céline

    2015-03-01

    We report the discovery of 14 low-mass binary systems containing mid-M to mid-L dwarf companions with separations larger than 250 AU. We also report the independent discovery of nine other systems with similar characteristics that were recently discovered in other studies. We have identified these systems by searching for common proper motion sources in the vicinity of known high proper motion stars, based on a cross-correlation of wide area near-infrared surveys (2MASS, SDSS, and SIMP). An astrometric follow-up, for common proper motion confirmation, was made with SIMON and/or CPAPIR at the Observatoire du Mont Mégantic 1.6 m and CTIO 1.5 m telescopes for all the candidates identified. A spectroscopic follow-up was also made with GMOS or GNIRS at Gemini to determine the spectral types of 11 of our newly identified companions and 10 of our primaries. Statistical arguments are provided to show that all of the systems we report here are very likely to be physical binaries. One of the new systems reported features a brown dwarf companion: LSPM J1259+1001 (M5) has an L4.5 (2M1259+1001) companion at ˜340 AU. This brown dwarf was previously unknown. Seven other systems have a companion of spectral type L0-L1 at a separation in the 250-7500 AU range. Our sample includes 14 systems with a mass ratio below 0.3.

  13. Characterization of the Very-low-mass Secondary in the GJ 660.1AB System

    NASA Astrophysics Data System (ADS)

    Aganze, Christian; Burgasser, Adam J.; Faherty, Jacqueline K.; Choban, Caleb; Escala, Ivanna; Lopez, Mike A.; Jin, Yuhui; Tamiya, Tomoki; Tallis, Melisa; Rockward, Willie

    2016-02-01

    We present a spectroscopic analysis of the low-mass binary star system GJ 660.1AB, a pair of nearby M dwarfs for which we have obtained separated near-infrared spectra (0.9-2.5 μm) with the SpeX spectrograph. The spectrum of GJ 660.1B is distinctly peculiar, with a triangular-shaped 1.7 μm peak that initially suggests that it is a low-surface-gravity, young brown dwarf. However, we rule out this hypothesis and determine instead that this companion is a mild subdwarf (d/sdM7) based on the subsolar metallicity of the primary, [Fe/H] = -0.63 ± 0.06. Comparison of the near-infrared spectrum of GJ 660.1B to two sets of spectral models yields conflicting results, with a common effective temperature of Teff = 2550-2650 K, but alternately low surface gravity ({log}g = {4.4}-0.5+0.5) and very low metallicity ([M/H] = -{0.96}-0.24+0.19), or high surface gravity ({log}g = 5.0-5.5) and slightly subsolar metallicity ([M/H] = -{0.20}-0.19+0.13). We conjecture that insufficient condensate opacity and excessive collision-induced H2 absorption in the models bias them toward low surface gravities and a metallicity that is inconsistent with the primary and points toward improvements needed in the spectral modeling of metal-poor, very-low-mass dwarfs. The peculiar spectral characteristics of GJ 660.1B emphasize that care is needed when interpreting surface gravity features in the spectra of ultracool dwarfs.

  14. Outflows from Thick, Turbulent Accretion in High Accretion-Rate Protostellar Systems

    NASA Astrophysics Data System (ADS)

    Williams, Peter T.

    2012-01-01

    In previous work we argued that jets might not be produced through magnetocentrifugal acceleration, but rather through the toroidal stresses of magnetorotational instability (MRI)-driven turbulent magnetohydrodynamic (MHD) accretion in a geometrically thick disk or flow. High accretion-rate protostars are among the best candidates for this process because a geometrically thick accretion disk that extends down to the central star is more plausible in this context than in other protostellar systems. These systems are also cleaner objects to study than active galactic nuclei (AGN), microquasars, and the like, which necessarily involve more exotic relativistic physics. Here we present a novel in-depth analysis of the laboratory analog that inspired our work on this topic. This analog consists of the meridional flow around a rotating sphere in a viscoelastic fluid. We examine in detail the fluxes of mass, angular momentum, linear momentum, and energy, and how these depend upon system parameters. We find that the presence of an axial outflow depends critically upon the ratio of the analogous turbulent magnetic stress to turbulent Reynolds stress, which must be roughly equal to or larger than unity to drive an outflow. We also find that the flux of angular momentum can actually be opposed to the flow of matter within the outflow, despite the fact that the outflow is ultimately powered by the radial transport of angular momentum from the central object. In particular we show that, in contrast with magnetocentrifugal acceleration, the angular momentum of the outflow actually decreases even while the material is being axially accelerated. This translates to observational tests in protostellar jets. There are some obvious enormous differences between compressible flow in a gravitational field and incompressible flow in a laboratory. We address this and we and argue why, despite these differences, there is much to learn from this laboratory system.

  15. DISENTANGLING THE ENTANGLED: OBSERVATIONS AND ANALYSIS OF THE TRIPLE NON-COEVAL PROTOSTELLAR SYSTEM VLA1623

    SciTech Connect

    Murillo, Nadia M.; Lai, Shih-Ping E-mail: slai@phys.nthu.edu.tw

    2013-02-10

    Commonplace at every evolutionary stage, multiple protostellar systems (MPSs) are thought to be formed through fragmentation, but it is unclear when and how. The youngest MPSs, which have not yet undergone much evolution, provide important constraints to this question. It is then of interest to disentangle early stage MPSs. In this Letter we present the results of our work on VLA1623 using our observations and archival data from the Submillimeter Array. Our continuum and line observations trace VLA1623's components, outflow, and envelope, revealing unexpected characteristics. We construct the spectral energy distribution (SED) for each component using the results of our work and data from literature, as well as derive physical parameters from continuum and perform a simple kinematical analysis of the circumstellar material. Our results show VLA1623 to be a triple non-coeval system composed of VLA1623A, B, and W, with each source driving its own outflow and unevenly distributed circumstellar material. From the SED, physical parameters, and IR emission we conclude that VLA1623A and W are Class 0 and Class I protostars, respectively, and together drive the bulk of the observed outflow. Furthermore, we find two surprising results, first the presence of a rotating disk-like structure about VLA1623A with indications of pure Keplerian rotation, which, if real, would make it one of the first evidence of Keplerian disk structures around Class 0 protostars. Second, we find VLA1623B to be a bona fide extremely young protostellar object between the starless core and Class 0 stages.

  16. GJ 3236: A NEW BRIGHT, VERY LOW MASS ECLIPSING BINARY SYSTEM DISCOVERED BY THE MEARTH OBSERVATORY

    SciTech Connect

    Irwin, Jonathan; Charbonneau, David; Berta, Zachory K.; Quinn, Samuel N.; Latham, David W.; Torres, Guillermo; Blake, Cullen H.; Burke, Christopher J.; Esquerdo, Gilbert A.; Fueresz, Gabor; Mink, Douglas J.; Nutzman, Philip; Szentgyorgyi, Andrew H.; Calkins, Michael L.; Falco, Emilio E.; Bloom, Joshua S.; Starr, Dan L.

    2009-08-20

    We report the detection of eclipses in GJ 3236, a bright (I = 11.6), very low mass binary system with an orbital period of 0.77 days. Analysis of light and radial velocity curves of the system yielded component masses of 0.38 {+-} 0.02 M{sub sun} and 0.28 {+-} 0.02 M{sub sun}. The central values for the stellar radii are larger than the theoretical models predict for these masses, in agreement with the results for existing eclipsing binaries, although the present 5% observational uncertainties limit the significance of the larger radii to approximately 1{sigma}. Degeneracies in the light curve models resulting from the unknown configuration of surface spots on the components of GJ 3236 currently dominate the uncertainties in the radii, and could be reduced by obtaining precise, multiband photometry covering the full orbital period. The system appears to be tidally synchronized and shows signs of high activity levels as expected for such a short orbital period, evidenced by strong H{alpha} emission lines in the spectra of both components. These observations probe an important region of mass-radius parameter space around the predicted transition to fully convective stellar interiors, where there are a limited number of precise measurements available in the literature.

  17. DISCOVERY AND CHARACTERIZATION OF WIDE BINARY SYSTEMS WITH A VERY LOW MASS COMPONENT

    SciTech Connect

    Baron, Frédérique; Lafrenière, David; Artigau, Étienne; Doyon, René; Gagné, Jonathan; Robert, Jasmin; Nadeau, Daniel; Davison, Cassy L.; Malo, Lison; Reylé, Céline

    2015-03-20

    We report the discovery of 14 low-mass binary systems containing mid-M to mid-L dwarf companions with separations larger than 250 AU. We also report the independent discovery of nine other systems with similar characteristics that were recently discovered in other studies. We have identified these systems by searching for common proper motion sources in the vicinity of known high proper motion stars, based on a cross-correlation of wide area near-infrared surveys (2MASS, SDSS, and SIMP). An astrometric follow-up, for common proper motion confirmation, was made with SIMON and/or CPAPIR at the Observatoire du Mont Mégantic 1.6 m and CTIO 1.5 m telescopes for all the candidates identified. A spectroscopic follow-up was also made with GMOS or GNIRS at Gemini to determine the spectral types of 11 of our newly identified companions and 10 of our primaries. Statistical arguments are provided to show that all of the systems we report here are very likely to be physical binaries. One of the new systems reported features a brown dwarf companion: LSPM J1259+1001 (M5) has an L4.5 (2M1259+1001) companion at ∼340 AU. This brown dwarf was previously unknown. Seven other systems have a companion of spectral type L0–L1 at a separation in the 250–7500 AU range. Our sample includes 14 systems with a mass ratio below 0.3.

  18. Deep, Low Mass Ratio Overcontact Binary Systems. IX. V345 Geminorum with a Bright Visual Pair

    NASA Astrophysics Data System (ADS)

    Yang, Y.-G.; Qian, S.-B.; Zhu, L.-Y.; He, J.-J.

    2009-08-01

    CCD photometric observations of the visual binary, V345 Geminorum, obtained from 2007 January 24 to 2009 March 22, are presented. When comparing the light curves in 2007 and 2008, it is found that there appears to be an O'Connell effect in the light curves of 2008. From those observations, two sets of photometric solutions were deduced using the 2003 version of the W-D program. The results indicated that V345 Gem is a low mass ratio overcontact binary with f = 72.9%(±3.1%). The asymmetric light curves in 2008 may be attributed to the activity of starspot, whose area is up to 1.55% of the area of the more massive component. The contributions of the third light to the total light are approximately 20% in the BVR bands. The absolute physical parameters for V345 Gem were obtained first. From the log L-log M diagram of the binary-star evolution, the primary component is an evolved star. From the O-C curve for V345 Gem, it is discovered that there exists a long-term period increase with a cyclic variation. The period and amplitude of the cyclic variation are P 3 = 646.7(±0.7) day and A = 0fd0019(±0fd0002), which may be caused by the light-time effect via the assumed third body. If it is true, the visual binary V345 Gem may be a quadruple star. The kind of additional component may remove angular momentum from the central system, which may play an important role for the formation and evolution of the binary. The secular period increases at a rate of dP/dt = +5.88 × 10-8 d yr-1, indicating that the mass transfers from the less massive component to the more massive component. With mass transferring, the orbital angular momentum decreases while the spin angular momentum increases. When J spin/J orb > 1/3, this kind of deep, low mass ratio overcontact binary with secular period increase may evolve into a rapid-rotating single star.

  19. Deep, Low Mass Ratio Overcontact Binary Systems. XIV. A Statistical Analysis of 46 Sample Binaries

    NASA Astrophysics Data System (ADS)

    Yang, Yuan-Gui; Qian, Sheng-Bang

    2015-09-01

    A sample of 46 deep, low mass ratio (DLMR) overcontact binaries (i.e., q≤slant 0.25 and f≥slant 50%) is statistically analyzed in this paper. It is found that five relations possibly exist among some physical parameters. The primary components are little-evolved main sequence stars that lie between the zero-age main sequence line and the terminal-age main sequence (TAMS) line. Meanwhile, the secondary components may be evolved stars above the TAMS line. The super-luminosities and large radii may result from energy transfer, which causes their volumes to expand. The equations of M-L and M-R for the components are also determined. The relation of P-Mtotal implies that mass may escape from the central system when the orbital period decreases. The minimum mass ratio may preliminarily be {q}{min}=0.044(+/- 0.007) from the relations of q-f and q-Jspin/Jorb. With mass and angular momentum loss, the orbital period decreases, which finally causes this kind of DLMR overcontact binary to merge into a rapid-rotating single star.

  20. Possible planet formation in the young, low-mass, multiple stellar system GG Tau A.

    PubMed

    Dutrey, Anne; Di Folco, Emmanuel; Guilloteau, Stéphane; Boehler, Yann; Bary, Jeff; Beck, Tracy; Beust, Hervé; Chapillon, Edwige; Gueth, Fredéric; Huré, Jean-Marc; Pierens, Arnaud; Piétu, Vincent; Simon, Michal; Tang, Ya-Wen

    2014-10-30

    The formation of planets around binary stars may be more difficult than around single stars. In a close binary star (with a separation of less than a hundred astronomical units), theory predicts the presence of circumstellar disks around each star, and an outer circumbinary disk surrounding a gravitationally cleared inner cavity around the stars. Given that the inner disks are depleted by accretion onto the stars on timescales of a few thousand years, any replenishing material must be transferred from the outer reservoir to fuel planet formation (which occurs on timescales of about one million years). Gas flowing through disk cavities has been detected in single star systems. A circumbinary disk was discovered around the young low-mass binary system GG Tau A (ref. 7), which has recently been shown to be a hierarchical triple system. It has one large inner disk around the single star, GG Tau Aa, and shows small amounts of shocked hydrogen gas residing within the central cavity, but other than a single weak detection, the distribution of cold gas in this cavity or in any other binary or multiple star system has not hitherto been determined. Here we report imaging of gas fragments emitting radiation characteristic of carbon monoxide within the GG Tau A cavity. From the kinematics we conclude that the flow appears capable of sustaining the inner disk (around GG Tau Aa) beyond the accretion lifetime, leaving time for planet formation to occur there. These results show the complexity of planet formation around multiple stars and confirm the general picture predicted by numerical simulations.

  1. Possible planet formation in the young, low-mass, multiple stellar system GG Tau A

    NASA Astrophysics Data System (ADS)

    Dutrey, Anne; di Folco, Emmanuel; Guilloteau, Stéphane; Boehler, Yann; Bary, Jeff; Beck, Tracy; Beust, Hervé; Chapillon, Edwige; Gueth, Fredéric; Huré, Jean-Marc; Pierens, Arnaud; Piétu, Vincent; Simon, Michal; Tang, Ya-Wen

    2014-10-01

    The formation of planets around binary stars may be more difficult than around single stars. In a close binary star (with a separation of less than a hundred astronomical units), theory predicts the presence of circumstellar disks around each star, and an outer circumbinary disk surrounding a gravitationally cleared inner cavity around the stars. Given that the inner disks are depleted by accretion onto the stars on timescales of a few thousand years, any replenishing material must be transferred from the outer reservoir to fuel planet formation (which occurs on timescales of about one million years). Gas flowing through disk cavities has been detected in single star systems. A circumbinary disk was discovered around the young low-mass binary system GG Tau A (ref. 7), which has recently been shown to be a hierarchical triple system. It has one large inner disk around the single star, GG Tau Aa, and shows small amounts of shocked hydrogen gas residing within the central cavity, but other than a single weak detection, the distribution of cold gas in this cavity or in any other binary or multiple star system has not hitherto been determined. Here we report imaging of gas fragments emitting radiation characteristic of carbon monoxide within the GG Tau A cavity. From the kinematics we conclude that the flow appears capable of sustaining the inner disk (around GG Tau Aa) beyond the accretion lifetime, leaving time for planet formation to occur there. These results show the complexity of planet formation around multiple stars and confirm the general picture predicted by numerical simulations.

  2. Detection of a very low mass star in an eclipsing binary system

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Priyanka; Chakraborty, Abhijit; Anandarao, B. G.; Roy, Arpita; Mahadevan, Suvrath

    2016-10-01

    We report the detection of a very low mass star (VLMS) companion to the primary star 1SWASP J234318.41+295556.5A (J2343+29A), using radial velocity (RV) measurements from the PARAS (PRL Advanced Radial-velocity Abu-sky Search) high-resolution echelle spectrograph. The periodicity of the single-lined eclipsing binary (SB1) system, as determined from 20 sets of RV observations from PARAS and 6 supporting sets of observations from SOPHIE data, is found to be 16.953 d as against the 4.24 d period reported from SuperWASP photometry. It is likely that inadequate phase coverage of the transit with SuperWASP photometry led to the incorrect determination of the period for this system. We derive the spectral properties of the primary star from the observed stellar spectra: Teff = 5125 ± 67 K, [Fe/H] = 0.1 ± 0.14 and logg = 4.6 ± 0.14, indicating a K1V primary. Applying the Torres relation to the derived stellar parameters, we estimate a primary mass 0.864_{-0.098}^{+0.097} M⊙ and a radius of 0.854_{-0.060}^{+0.050} R⊙. We combine RV data with SuperWASP photometry to estimate the mass of the secondary, MB = 0.098 ± 0.007 M⊙, and its radius, RB = 0.127 ± 0.007 R⊙, with an accuracy of ˜7 per cent. Although the observed radius is found to be consistent with the Baraffe's theoretical models, the uncertainties on the mass and radius of the secondary reported here are model dependent and should be used with discretion. Here, we establish this system as a potential benchmark for the study of VLMS objects, worthy of both photometric follow-up and the investment of time on high-resolution spectrographs paired with large-aperture telescopes.

  3. SMA OBSERVATIONS OF CLASS 0 PROTOSTARS: A HIGH ANGULAR RESOLUTION SURVEY OF PROTOSTELLAR BINARY SYSTEMS

    SciTech Connect

    Chen Xuepeng; Arce, Hector G.; Dunham, Michael M.; Zhang Qizhou; Bourke, Tyler L.; Launhardt, Ralf; Henning, Thomas; Jorgensen, Jes K.; Lee, Chin-Fei; Foster, Jonathan B.; Pineda, Jaime E. E-mail: xuepeng.chen@yale.edu

    2013-05-10

    We present high angular resolution 1.3 mm and 850 {mu}m dust continuum data obtained with the Submillimeter Array toward 33 Class 0 protostars in nearby clouds (distance < 500 pc), which represents so far the largest survey toward protostellar binary/multiple systems. The median angular resolution in the survey is 2.''5, while the median linear resolution is approximately 600 AU. Compact dust continuum emission is observed from all sources in the sample. Twenty-one sources in the sample show signatures of binarity/multiplicity, with separations ranging from 50 AU to 5000 AU. The numbers of singles, binaries, triples, and quadruples in the sample are 12, 14, 5, and 2, respectively. The derived multiplicity frequency (MF) and companion star fraction (CSF) for Class 0 protostars are 0.64 {+-} 0.08 and 0.91 {+-} 0.05, respectively, with no correction for completeness. The derived MF and CSF in this survey are approximately two times higher than the values found in the binary surveys toward Class I young stellar objects, and approximately three (for MF) and four (for CSF) times larger than the values found among main-sequence stars, with a similar range of separations. Furthermore, the observed fraction of high-order multiple systems to binary systems in Class 0 protostars (0.50 {+-} 0.09) is also larger than the fractions found in Class I young stellar objects (0.31 {+-} 0.07) and main-sequence stars ({<=}0.2). These results suggest that binary properties evolve as protostars evolve, as predicted by numerical simulations. The distribution of separations for Class 0 protostellar binary/multiple systems shows a general trend in which CSF increases with decreasing companion separation. We find that 67% {+-} 8% of the protobinary systems have circumstellar mass ratios below 0.5, implying that unequal-mass systems are preferred in the process of binary star formation. We suggest an empirical sequential fragmentation picture for binary star formation, based on this work and

  4. Rotationally driven Fragmentation in the Formation of the Binary Protostellar System L1551 IRS 5

    NASA Astrophysics Data System (ADS)

    Lim, Jeremy; Yeung, Paul K. H.; Hanawa, Tomoyuki; Takakuwa, Shigehisa; Matsumoto, Tomoaki; Saigo, Kazuya

    2016-08-01

    Both bulk rotation and local turbulence have been widely suggested to drive the fragmentation in collapsing cores that produces multiple star systems. Even when the two mechanisms predict different alignments for stellar spins and orbits, subsequent internal or external interactions can drive multiple systems toward or away from alignment, thus masking their formation processes. Here, we demonstrate that the geometrical and dynamical relationship between a binary system and its surrounding bulk envelope provide the crucial distinction between fragmentation models. We find that the circumstellar disks of the binary protostellar system L1551 IRS 5 are closely parallel, not just with each other but also with their surrounding flattened envelope. Measurements of the relative proper motion of the binary components spanning nearly 30 years indicate an orbital motion related to that of the envelope rotation. Eliminating orbital solutions whereby the circumstellar disks would be tidally truncated to sizes smaller than observed, the remaining solutions favor a circular or low-eccentricity orbit tilted by up to ˜25° from the circumstellar disks. Turbulence-driven fragmentation can generate local angular momentum to produce a coplanar binary system, but this would have no particular relationship to the system’s surrounding envelope. Instead, the observed properties conform with predictions for rotationally driven fragmentation. If the fragments were produced at different heights or on opposite sides of the mid-plane in the flattened central region of a rotating core, the resulting protostars would then exhibit circumstellar disks parallel with the surrounding envelope but tilted from the orbital plane, as is observed.

  5. Planets around Low-mass Stars (PALMS). IV. The Outer Architecture of M Dwarf Planetary Systems

    NASA Astrophysics Data System (ADS)

    Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Tamura, Motohide

    2015-01-01

    We present results from a high-contrast adaptive optics imaging search for giant planets and brown dwarfs (gsim1 M Jup) around 122 newly identified nearby (lsim40 pc) young M dwarfs. Half of our targets are younger than 135 Myr and 90% are younger than the Hyades (620 Myr). After removing 44 close stellar binaries (implying a stellar companion fraction of >35.4% ± 4.3% within 100 AU), 27 of which are new or spatially resolved for the first time, our remaining sample of 78 single M dwarfs makes this the largest imaging search for planets around young low-mass stars (0.1-0.6 M ⊙) to date. Our H- and K-band coronagraphic observations with Keck/NIRC2 and Subaru/HiCIAO achieve typical contrasts of 12-14 mag and 9-13 mag at 1'', respectively, which correspond to limiting planet masses of 0.5-10 M Jup at 5-33 AU for 85% of our sample. We discovered four young brown dwarf companions: 1RXS J235133.3+312720 B (32 ± 6 M Jup; L0+2-1; 120 ± 20 AU), GJ 3629 B (64+30-23 M Jup; M7.5 ± 0.5; 6.5 ± 0.5 AU), 1RXS J034231.8+121622 B (35 ± 8 M Jup; L0 ± 1; 19.8 ± 0.9 AU), and 2MASS J15594729+4403595 B (43 ± 9 M Jup; M8.0 ± 0.5; 190 ± 20 AU). Over 150 candidate planets were identified; we obtained follow-up imaging for 56% of these but all are consistent with background stars. Our null detection of planets enables strong statistical constraints on the occurrence rate of long-period giant planets around single M dwarfs. We infer an upper limit (at the 95% confidence level) of 10.3% and 16.0% for 1-13 M Jup planets between 10-100 AU for hot-start and cold-start (Fortney) evolutionary models, respectively. Fewer than 6.0% (9.9%) of M dwarfs harbor massive gas giants in the 5-13 M Jup range like those orbiting HR 8799 and β Pictoris between 10-100 AU for a hot-start (cold-start) formation scenario. The frequency of brown dwarf (13-75 M Jup) companions to single M dwarfs between 10-100 AU is 2.8+2.4-1.5%. Altogether we find that giant planets, especially massive ones, are rare

  6. PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS

    SciTech Connect

    Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Tamura, Motohide

    2015-01-01

    We present results from a high-contrast adaptive optics imaging search for giant planets and brown dwarfs (≳1 M {sub Jup}) around 122 newly identified nearby (≲40 pc) young M dwarfs. Half of our targets are younger than 135 Myr and 90% are younger than the Hyades (620 Myr). After removing 44 close stellar binaries (implying a stellar companion fraction of >35.4% ± 4.3% within 100 AU), 27 of which are new or spatially resolved for the first time, our remaining sample of 78 single M dwarfs makes this the largest imaging search for planets around young low-mass stars (0.1-0.6 M {sub ☉}) to date. Our H- and K-band coronagraphic observations with Keck/NIRC2 and Subaru/HiCIAO achieve typical contrasts of 12-14 mag and 9-13 mag at 1'', respectively, which correspond to limiting planet masses of 0.5-10 M {sub Jup} at 5-33 AU for 85% of our sample. We discovered four young brown dwarf companions: 1RXS J235133.3+312720 B (32 ± 6 M {sub Jup}; L0{sub −1}{sup +2}; 120 ± 20 AU), GJ 3629 B (64{sub −23}{sup +30} M {sub Jup}; M7.5 ± 0.5; 6.5 ± 0.5 AU), 1RXS J034231.8+121622 B (35 ± 8 M {sub Jup}; L0 ± 1; 19.8 ± 0.9 AU), and 2MASS J15594729+4403595 B (43 ± 9 M {sub Jup}; M8.0 ± 0.5; 190 ± 20 AU). Over 150 candidate planets were identified; we obtained follow-up imaging for 56% of these but all are consistent with background stars. Our null detection of planets enables strong statistical constraints on the occurrence rate of long-period giant planets around single M dwarfs. We infer an upper limit (at the 95% confidence level) of 10.3% and 16.0% for 1-13 M {sub Jup} planets between 10-100 AU for hot-start and cold-start (Fortney) evolutionary models, respectively. Fewer than 6.0% (9.9%) of M dwarfs harbor massive gas giants in the 5-13 M {sub Jup} range like those orbiting HR 8799 and β Pictoris between 10-100 AU for a hot-start (cold-start) formation scenario. The frequency of brown dwarf (13-75 M {sub Jup}) companions to single

  7. Disentangling the jet emission from protostellar systems. The ALMA view of VLA1623

    NASA Astrophysics Data System (ADS)

    Santangelo, G.; Murillo, N. M.; Nisini, B.; Codella, C.; Bruderer, S.; Lai, S.-P.; van Dishoeck, E. F.

    2015-09-01

    Context. High-resolution studies of class 0 protostars represent the key to constraining protostar formation models. VLA16234-2417 represents the prototype of class 0 protostars, and it has been recently identified as a triple non-coeval system. Aims: We aim at deriving the physical properties of the jets in VLA16234-2417 using tracers of shocked gas. Methods: ALMA Cycle 0 Early Science observations of CO(2-1) in the extended configuration are presented in comparison with previous SMA CO(3-2) and Herschel-PACS [Oi] 63 μm observations. Gas morphology and kinematics were analysed to constrain the physical structure and origin of the protostellar outflows. Results: We reveal a collimated jet component associated with the [Oi] 63 μm emission at about 8'' (~960 AU) from source B. This newly detected jet component is inversely oriented with respect to the large-scale outflow driven by source A, and it is aligned with compact and fast jet emission very close to source B (about 0''&dotbelow;3) rather than with the direction perpendicular to the A disk. We also detect a cavity-like structure at low projected velocities, which surrounds the [Oi] 63 μm emission and is possibly associated with the outflow driven by source A. Finally, no compact outflow emission is associated with source W. Conclusions: Our high-resolution ALMA observations seem to suggest there is a fast and collimated jet component associated with source B. This scenario would confirm that source B is younger than A, that it is in a very early stage of evolution, and that it drives a faster, more collimated, and more compact jet with respect to the large-scale slower outflow driven by A. However, a different scenario of a precessing jet driven by A cannot be firmly excluded from the present observations. Appendix A is available in electronic form at http://www.aanda.org

  8. Deep, Low Mass Ratio Overcontact Binary Systems. XIII. DZ Piscium with Intrinsic Light Variability

    NASA Astrophysics Data System (ADS)

    Yang, Y.-G.; Qian, S.-B.; Zhang, L.-Y.; Dai, H.-F.; Soonthornthum, B.

    2013-08-01

    New multi-color photometry for the eclipsing binary DZ Psc was performed in 2011 and 2012 using the 85 cm telescope at the Xinglong Station of the National Astronomical Observatories of China. Using the updated Wilson-Devinney (W-D) code, we deduced two sets of photometric solutions. The overcontact degree is f = 89.7(± 1.0)%, identifying DZ Psc as a deep, low mass ratio overcontact binary. The asymmetric light curves (i.e., LC2 in 2012) were modeled by a hot spot on the primary star. Based on all of the available light minimum times, we discovered that the orbital period of DZ Psc may be undergoing a secular period increase with a cyclic variation. The modulated period and semi-amplitude of this oscillation are P mod = 11.89(± 0.19) yr and A = 0.0064(± 0.0006) days, which may be possibly attributed to either cyclic magnetic activity or light-time effect due to the third body. The long-term period increases at a rate of dP/dt=+7.43(+/- 0.17)\\times 10^{-7}{\\,days\\, yr^{-1}}, which may be interpreted as conserved mass transfer from the less massive component to the more massive one. With mass transferring, DZ Psc will finally merge into a rapid-rotation single star when J spin/J orb > 1/3.

  9. HIGH RESOLUTION H{alpha} IMAGES OF THE BINARY LOW-MASS PROPLYD LV 1 WITH THE MAGELLAN AO SYSTEM

    SciTech Connect

    Wu, Y.-L.; Close, L. M.; Males, J. R.; Follette, K.; Morzinski, K.; Kopon, D.; Rodigas, T. J.; Hinz, P.; Puglisi, A.; Esposito, S.; Pinna, E.; Riccardi, A.; Xompero, M.; Briguglio, R.

    2013-09-01

    We utilize the new Magellan adaptive optics system (MagAO) to image the binary proplyd LV 1 in the Orion Trapezium at H{alpha}. This is among the first AO results in visible wavelengths. The H{alpha} image clearly shows the ionization fronts, the interproplyd shell, and the cometary tails. Our astrometric measurements find no significant relative motion between components over {approx}18 yr, implying that LV 1 is a low-mass system. We also analyze Large Binocular Telescope AO observations, and find a point source which may be the embedded protostar's photosphere in the continuum. Converting the H magnitudes to mass, we show that the LV 1 binary may consist of one very-low-mass star with a likely brown dwarf secondary, or even plausibly a double brown dwarf. Finally, the magnetopause of the minor proplyd is estimated to have a radius of 110 AU, consistent with the location of the bow shock seen in H{alpha}.

  10. KIC 1571511B: a benchmark low-mass star in an eclipsing binary system in the Kepler field

    NASA Astrophysics Data System (ADS)

    Ofir, A.; Gandolfi, D.; Buchhave, Lars; Lacy, C. H. S.; Hatzes, A. P.; Fridlund, Malcolm

    2012-06-01

    KIC 1571511 is a 14-d eclipsing binary (EB) in the Kepler data set. The secondary of this EB is a very low mass star with a mass of ? and a radius of ? (statistical errors only). The overall system parameters make KIC 1571511B an ideal 'benchmark object': among the smallest, lightest and best-described stars known, smaller even than some known exoplanet. Currently available photometry encompasses only a small part of the total: future Kepler data releases promise to constrain many of the properties of KIC 1571511B to unprecedented level. However, as in many spectroscopic single-lined systems, the current error budget is dominated by the modelling errors of the primary and not by the above statistical errors. We conclude that detecting the RV signal of the secondary component is crucial to achieving the full potential of this possible benchmark object for the study of low-mass stars. Footnotes<label>1</label>Kepler Data Processing Handbook section 9.3, document number KSCI-19081-001 of 2011 April 1.<label>2</label>See Kepler Instrument Handbook, document KSCI-19033, for full description.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22016329','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22016329"><span id="translatedtitle">FEEDBACK EFFECTS ON <span class="hlt">LOW-MASS</span> STAR FORMATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hansen, Charles E.; Klein, Richard I.; McKee, Christopher F.; Fisher, Robert T.</p> <p>2012-03-01</p> <p><span class="hlt">Protostellar</span> feedback, both radiation and bipolar outflows, dramatically affects the fragmentation and mass accretion from star-forming cores. We use ORION, an adaptive mesh refinement gravito-radiation-hydrodynamics code, to simulate <span class="hlt">low-mass</span> star formation in a turbulent molecular cloud in the presence of <span class="hlt">protostellar</span> feedback. We present results of the first simulations of a star-forming cluster that include both radiative transfer and <span class="hlt">protostellar</span> outflows. We run four simulations to isolate the individual effects of radiation feedback and outflow feedback as well as the combination of the two. We find that outflows reduce <span class="hlt">protostellar</span> masses and accretion rates each by a factor of three and therefore reduce <span class="hlt">protostellar</span> luminosities by an order of magnitude. This means that, while radiation feedback suppresses fragmentation, outflows render <span class="hlt">protostellar</span> radiation largely irrelevant for <span class="hlt">low-mass</span> star formation above a mass scale of 0.05 M{sub Sun }. We find initial fragmentation of our cloud at half the global Jeans length, around 0.1 pc. With insufficient <span class="hlt">protostellar</span> radiation to stop it, these 0.1 pc cores fragment repeatedly, forming typically 10 stars each. The accretion rate in these stars scales with mass as predicted from core accretion models that include both thermal and turbulent motions; the accretion rate does not appear to be consistent with either competitive accretion or accretion from an isothermal sphere. We find that <span class="hlt">protostellar</span> outflows do not significantly affect the overall cloud dynamics, in the absence of magnetic fields, due to their small opening angles and poor coupling to the dense gas. The outflows reduce the mass from the cores by 2/3, giving a core to star efficiency, {epsilon}{sub core} {approx_equal} 1/3. The simulations are also able to reproduce many observation of local star-forming regions. Our simulation with radiation and outflows reproduces the observed <span class="hlt">protostellar</span> luminosity function. All of the simulations can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AAS...21934518D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AAS...21934518D&link_type=ABSTRACT"><span id="translatedtitle">Wide <span class="hlt">Low-Mass</span> Tertiary Companions of Binary Star <span class="hlt">Systems</span> as a Test of Star Formation Theories</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Douglas, Stephanie; Allen, P.</p> <p>2012-01-01</p> <p>We will present the status of a common proper motion search for wide <span class="hlt">low-mass</span> stellar and sub-stellar companions to known white dwarf-M dwarf binary <span class="hlt">systems</span>. I-band observations were made using the 31" NURO telescope at Lowell Observatory. Candidate companions are selected using astrometry from our own data and 2MASS photometry. We have begun to spectroscopically confirm candidates that pass our selection criteria. The ultimate goal of the search is to test star formation theories which predict that close binary <span class="hlt">systems</span> form by transferring angular momentum to a third companion. To this end, we will model the physical companion population and perform Bayesian statistical analysis to determine the best-fit population model to our data. Here we will present our spectroscopically confirmed companions as well as the preliminary results of our population models and statistical analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21574853','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21574853"><span id="translatedtitle">RESOLVING THE sin(I) DEGENERACY IN <span class="hlt">LOW-MASS</span> MULTI-PLANET <span class="hlt">SYSTEMS</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Batygin, Konstantin; Laughlin, Gregory</p> <p>2011-04-01</p> <p>Long-term orbital evolution of multi-planet <span class="hlt">systems</span> under tidal dissipation often converges to a stationary state, known as the tidal fixed point. The fixed point is characterized by a lack of oscillations in the eccentricities and apsidal alignment among the orbits. Quantitatively, the nature of the fixed point is dictated by mutual interactions among the planets as well as non-Keplerian effects. We show that if a roughly coplanar <span class="hlt">system</span> hosts a hot, sub-Saturn mass planet, and is tidally relaxed, separation of planet-planet interactions and non-Keplerian effects in the equations of motion leads to a direct determination of the true masses of the planets. Consequently, a 'snap-shot' observational determination of the orbital state resolves the sin(I) degeneracy and opens up a direct avenue toward identification of the true lowest-mass exoplanets detected. We present an approximate, as well as a general, mathematical framework for computation of the line-of-sight inclination of secular <span class="hlt">systems</span>, and apply our models illustratively to the 61 Vir <span class="hlt">system</span>. We conclude by discussing the observability of planetary <span class="hlt">systems</span> to which our method is applicable and we set our analysis into a broader context by presenting a current summary of the various possibilities for determining the physical properties of planets from observations of their orbital states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AJ....130.1206Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AJ....130.1206Q"><span id="translatedtitle">Deep, <span class="hlt">Low</span> <span class="hlt">Mass</span> Ratio Overcontact Binary <span class="hlt">Systems</span>. V. The Lowest Mass Ratio Binary V857 Herculis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qian, S.-B.; Zhu, L.-Y.; Soonthornthum, B.; Yuan, J.-Z.; Yang, Y.-G.; He, J.-J.</p> <p>2005-09-01</p> <p>Charge-coupled device (CCD) photometric light curves in the B, V, and R bands of the complete eclipsing binary star V857 Her are presented. It is shown that the light curves of the W UMa-type binary are symmetric and of A type according to Binnendijk's classification. Our four epochs of light minimum along with others compiled from the literature were used to revise the period and study the period change. Weak evidence indicates that the orbital period of V857 Her may show a continuous increase at a rate of dP/dt=+2.90×10-7 days yr-1. The photometric parameters of the <span class="hlt">system</span> were determined with the 2003 version of the Wilson-Devinney code. It is shown that V857 Her is a deep overcontact binary <span class="hlt">system</span> with f=83.8%+/-5.1%. The derived mass ratio of q=0.06532+/-0.0002 suggests that it has the lowest mass ratio among overcontact binary <span class="hlt">systems</span>. As the orbital period increases, the decrease of the mass ratio will cause it to evolve into a single rapidly rotating star when it meets the more familiar criterion that the orbital angular momentum be less than 3 times the total spin angular momentum. To understand the evolutionary state of the <span class="hlt">system</span>, long-term photometric monitoring and spectroscopic observations will be required.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011RAA....11..843A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011RAA....11..843A"><span id="translatedtitle">Photometric study and preliminary elements of the <span class="hlt">low-mass</span> ratio W UMa <span class="hlt">system</span> ASAS 021209+2708.3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Acerbi, Francesco; Barani, Carlo; Martignoni, Massimiliano</p> <p>2011-07-01</p> <p>We present CCD B and V light curves, obtained in the year 2006, and a photometric solution of the <span class="hlt">low-mass</span> ratio contact binary ASAS 021209+2708.3. With our data we were able to determine six new times of minimum light and refine the orbital period of the <span class="hlt">system</span> to 0.3181963 days. The light curves are analyzed using the 2003 version of the Wilson-Devinney program and the analysis was performed with and without adding a spot on the surface of one star because the light curves appear to exhibit a typical O'Connell effect, with Maximum I brighter than Maximum II. The results show that ASAS 021209+2708.3 may be classified as an A-subtype W Ursae Majoris <span class="hlt">system</span> with a small mass ratio q = 0.1889, a large over-contact degree of f = 0.587, a very small difference between the component temperatures of ΔT = 53 K and an orbital inclination of i = 81°. It is known that deep (f > 50%), <span class="hlt">low-mass</span> ratio (q < 0.25) overcontact binary stars are a very important resource for understanding the phenomena of Blue Straggler/FK Com-type stars. The formations of Blue Straggler stars and FK Com-type stars are unsolved problems in stellar astrophysics. One of the possible explanations for their formation is from the coalescence of W UMa-type overcontact binary <span class="hlt">systems</span>. The absolute dimensions of ASAS 021209+2708.3 are estimated and its dynamical evolution is inferred.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2254993K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2254993K"><span id="translatedtitle">Water in embedded <span class="hlt">low-mass</span> protostars: cold envelopes and warm outflows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristensen, Lars E.; van Dishoeck, Ewine; Mottram, Joseph; Schmalzl, Markus; Visser, Ruud</p> <p>2015-08-01</p> <p>As stars form, gas from the parental cloud is transported through the molecular envelope to the <span class="hlt">protostellar</span> disk from which planets eventually form. Water plays a crucial role in such <span class="hlt">systems</span>: it forms the backbone of the oxygen chemistry, it is a unique probe of warm and hot gas, and it provides a unique link between the grain surface and gas-phase chemistries. The distribution of water, both as ice and gas, is a fundamental question to our understanding of how planetary <span class="hlt">systems</span>, such as the Solar <span class="hlt">System</span>, form.The Herschel Space Observatory observed many tens of embedded <span class="hlt">low-mass</span> protostars in a suite of gas-phase water transitions in several programs (e.g. Water in Star-forming regions with Herschel, WISH, and the William Herschel Line Legacy Survey, WILL), and related species (e.g. CO in Protostars with HIFI, COPS-HIFI). I will summarize what Herschel has revealed about the water distribution in the cold outer molecular envelope of <span class="hlt">low-mass</span> protostars, and the warm gas in outflows, the two components predominantly traced by Herschel observations. I will present our current understanding of where the water vapor is in <span class="hlt">protostellar</span> <span class="hlt">systems</span> and the underlying physical and chemical processes leading to this distribution. Through these dedicated observational surveys and complementary modeling efforts, we are now at a stage where we can quantify where the water is during the early stages of star formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22034618','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22034618"><span id="translatedtitle">A HYBRID SCENARIO FOR THE FORMATION OF BROWN DWARFS AND VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> STARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Basu, Shantanu; Vorobyov, Eduard I. E-mail: eduard.vorobiev@univie.ac.at</p> <p>2012-05-01</p> <p>We present a calculation of <span class="hlt">protostellar</span> disk formation and evolution in which gaseous clumps (essentially, the first Larson cores formed via disk fragmentation) are ejected from the disk during the early stage of evolution. This is a universal process related to the phenomenon of ejection in multiple <span class="hlt">systems</span> of point masses. However, it occurs in our model entirely due to the interaction of compact, gravitationally bound gaseous clumps and is free from the smoothing-length uncertainty that is characteristic of models using sink particles. Clumps that survive ejection span a mass range of 0.08-0.35 M{sub Sun }, and have ejection velocities 0.8 {+-} 0.35 km s{sup -1}, which are several times greater than the escape speed. We suggest that, upon contraction, these clumps can form substellar or <span class="hlt">low-mass</span> stellar objects with notable disks, or even close-separation very <span class="hlt">low</span> <span class="hlt">mass</span> binaries. In this hybrid scenario, allowing for ejection of clumps rather than finished protostars/proto-brown-dwarfs, disk formation and the low velocity dispersion of <span class="hlt">low-mass</span> objects are naturally explained, while it is also consistent with the observation of isolated <span class="hlt">low-mass</span> clumps that are ejection products. We conclude that clump ejection and the formation of isolated <span class="hlt">low-mass</span> stellar and substellar objects is a common occurrence, with important implications for understanding the initial mass function, the brown dwarf desert, and the formation of stars in all environments and epochs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22364529','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22364529"><span id="translatedtitle">FORMATION OF MULTIPLE-SATELLITE <span class="hlt">SYSTEMS</span> FROM <span class="hlt">LOW-MASS</span> CIRCUMPLANETARY PARTICLE DISKS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hyodo, Ryuki; Ohtsuki, Keiji; Takeda, Takaaki E-mail: ohtsuki@tiger.kobe-u.ac.jp</p> <p>2015-01-20</p> <p>Circumplanetary particle disks would be created in the late stage of planetary formation either by impacts of planetary bodies or disruption of satellites or passing bodies, and satellites can be formed by accretion of disk particles spreading across the Roche limit. Previous N-body simulation of lunar accretion focused on the formation of single-satellite <span class="hlt">systems</span> from disks with large disk-to-planet mass ratios, while recent models of the formation of multiple-satellite <span class="hlt">systems</span> from disks with smaller mass ratios do not take account of gravitational interaction between formed satellites. In the present work, we investigate satellite accretion from particle disks with various masses, using N-body simulation. In the case of accretion from somewhat less massive disks than the case of lunar accretion, formed satellites are not massive enough to clear out the disk, but can become massive enough to gravitationally shepherd the disk outer edge and start outward migration due to gravitational interaction with the disk. When the radial location of the 2:1 mean motion resonance of the satellite reaches outside the Roche limit, the second satellite can be formed near the disk outer edge, and then the two satellites continue outward migration while being locked in the resonance. Co-orbital satellites are found to be occasionally formed on the orbit of the first satellite. Our simulations also show that stochastic nature involved in gravitational interaction and collision between aggregates in the tidal environment can lead to diversity in the final mass and orbital architecture, which would be expected in satellite <span class="hlt">systems</span> of exoplanets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...799...40H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...799...40H"><span id="translatedtitle">Formation of Multiple-satellite <span class="hlt">Systems</span> From <span class="hlt">Low-mass</span> Circumplanetary Particle Disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hyodo, Ryuki; Ohtsuki, Keiji; Takeda, Takaaki</p> <p>2015-01-01</p> <p>Circumplanetary particle disks would be created in the late stage of planetary formation either by impacts of planetary bodies or disruption of satellites or passing bodies, and satellites can be formed by accretion of disk particles spreading across the Roche limit. Previous N-body simulation of lunar accretion focused on the formation of single-satellite <span class="hlt">systems</span> from disks with large disk-to-planet mass ratios, while recent models of the formation of multiple-satellite <span class="hlt">systems</span> from disks with smaller mass ratios do not take account of gravitational interaction between formed satellites. In the present work, we investigate satellite accretion from particle disks with various masses, using N-body simulation. In the case of accretion from somewhat less massive disks than the case of lunar accretion, formed satellites are not massive enough to clear out the disk, but can become massive enough to gravitationally shepherd the disk outer edge and start outward migration due to gravitational interaction with the disk. When the radial location of the 2:1 mean motion resonance of the satellite reaches outside the Roche limit, the second satellite can be formed near the disk outer edge, and then the two satellites continue outward migration while being locked in the resonance. Co-orbital satellites are found to be occasionally formed on the orbit of the first satellite. Our simulations also show that stochastic nature involved in gravitational interaction and collision between aggregates in the tidal environment can lead to diversity in the final mass and orbital architecture, which would be expected in satellite <span class="hlt">systems</span> of exoplanets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NIMPA.735..366S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NIMPA.735..366S"><span id="translatedtitle">Finite element simulations of <span class="hlt">low-mass</span> readout cables for the CBM Silicon Tracking <span class="hlt">System</span> using RAPHAEL</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singla, M.; Chatterji, S.; Müller, W. F. J.; Kleipa, V.; Heuser, J. M.</p> <p>2014-01-01</p> <p>The first three-dimensional simulation study of thin multi-line readout cables using finite element simulation tool RAPHAEL is being reported. The application is the Silicon Tracking <span class="hlt">System</span> (STS) of the fixed-target heavy-ion experiment Compressed Baryonic Matter (CBM), under design at the forthcoming accelerator center FAIR in Germany. RAPHAEL has been used to design <span class="hlt">low-mass</span> analog readout cables with minimum possible Equivalent Noise Charge (ENC). Various trace geometries and trace materials have been explored in detail for this optimization study. These cables will bridge the distance between the microstrip detectors and the signal processing electronics placed at the periphery of the silicon tracking stations. SPICE modeling has been implemented in Sentaurus Device to study the transmission loss (dB loss) in cables and simulation has been validated with measurements. An optimized design having minimum possible ENC, material budget and transmission loss for the readout cables has been proposed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014hwat.confE..14F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014hwat.confE..14F"><span id="translatedtitle">MUSCLES: Measurements of the Ultraviolet Spectral Characteristics of <span class="hlt">Low-Mass</span> Exoplanetary <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>France, K.</p> <p>2014-04-01</p> <p>The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. Ultraviolet photons influence the atmospheric temperature profiles and production of potential biomarkers on Earth-like planets around these stars. In this talk, I will present results from a recent study of the UV radiation fields around nearby M dwarf planet hosts that covers both FUV and NUV wavelengths. We find that all six exoplanet host stars in our sample (GJ 581, GJ 876, GJ 436, GJ 832, GJ 667C, and GJ 1214) exhibit some level of chromospheric and transition region UV emission. No 'UV quiet' M dwarfs are observed. The bright stellar Lyman-alpha emission lines are reconstructed, and we find that the Lyman-alpha line fluxes comprise ~37 - 75% of the total 1150 - 3100 A flux from most M dwarfs; > 1000 times the solar value. The F(FUV)/F(NUV) flux ratio, a driver for possible abiotic production of the suggested biomarkers O2 and O3, is shown to be ~ 0.5 - 3 for all M dwarfs in our sample, > 1000 times the solar ratio. For the four stars with moderate signal-to-noise COS time-resolved spectra, we find UV emission line variability with amplitudes of 50 - 500% on 100 - 1000 second timescales. Finally, we observe relatively bright H2 fluorescent emission from four of the M dwarf exoplanetary <span class="hlt">systems</span> (GJ 581, GJ 876, GJ 436, and GJ 832). I will describe the possible origins of the hot (T (H2) ~ 2000 - 4000 K) molecular gas observed in these <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2230558T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2230558T"><span id="translatedtitle">SMA and ALMA Studies of Protoplanetary-Disk Formation around <span class="hlt">Low-mass</span> Protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takakuwa, Shigehisa; Yen, Hsi-Wei; Ohashi, Nagayoshi; Chou, Ti-Lin; Aso, Yusuke; Saigo, Kazuya; Saito, Masao; Machida, Masahiro N.; Tomida, Kengo; Aikawa, Yuri; Tomisaka, Kohji; Koyamatsu, Shin; Takahashi, Sanemichi Z.</p> <p>2015-08-01</p> <p>In this presentation, we will report our systematic observational studies of protoplanetary-disk formation around <span class="hlt">low-mass</span> protostars with the SMA and ALMA. We have identified five Class 0-I <span class="hlt">protostellar</span> <span class="hlt">systems</span> (L1551 IRS 5, L1551 NE, L1489 IRS, L1527 IRS, and TMC-1A) associated with the r~100 - 300 AU scale Keplerian disks and the outer infalling envelopes. The infalling velocities of the envelope gas onto the Keplerian disks are found to be a factor ~3 smaller than the free-fall velocities of the central <span class="hlt">protostellar</span> masses inferred from the inner Keplerian rotation. On the other hand, the rotational angular momenta in the infalling envelopes appear to smoothly connect to those of the inner Keplerian disks. Including the other disk sources found by previous observations, we have also found a growth of the disk radii as a function of the <span class="hlt">protostellar</span> evolution. These results demonstrate how the central Keplerian disks around protostars, precursors of the protoplanetary disks, grow and evolve. We will compile these observational results in the context of an unified picture of protoplanetary-disk formation, and compare them to the latest theoretical predictions of protoplanetary-disk formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...826..213L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...826..213L"><span id="translatedtitle">Angular Momentum Loss in the Envelope–Disk Transition Region of the HH 111 <span class="hlt">Protostellar</span> <span class="hlt">System</span>: Evidence for Magnetic Braking?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Chin-Fei; Hwang, Hsiang-Chih; Li, Zhi-Yun</p> <p>2016-08-01</p> <p>HH 111 is a Class I <span class="hlt">protostellar</span> <span class="hlt">system</span> at a distance of ˜400 pc, with the central source VLA 1 associated with a rotating disk deeply embedded in a flattened envelope. Here we present the observations of this <span class="hlt">system</span> at ˜0.″6 (240 au) resolution in C18O (J = 2 — 1) and a 230 GHz continuum obtained with the Atacama Large Millimeter/Submillimeter Array, and in SO ({N}J = {5}6-{4}5) obtained with the Submillimeter Array. The observations show for the first time how a Keplerian rotating disk can be formed inside a flattened envelope. The flattened envelope is detected in C18O, extending out to ≳2400 au from the VLA 1 source. It has a differential rotation, with the outer part (≳2000 au) better described by a rotation that has constant specific angular momentum, and the innermost part (≲160 au) by a Keplerian rotation. The rotationally supported disk is therefore relatively compact in this <span class="hlt">system</span>, which is consistent with the dust continuum observations. Most interestingly, if the flow is in steady state, there is a substantial drop in specific angular momentum in the envelope–disk transition region from 2000 to 160 au, by a factor of ˜3. Such a decrease is not expected outside a disk formed from simple hydrodynamic core collapse, but can happen naturally if the core is significantly magnetized, because magnetic fields can be trapped in the transition region outside the disk by the ram pressure of the <span class="hlt">protostellar</span> accretion flow, which can lead to efficient magnetic braking. In addition, SO shock emission is detected around the outer radius of the disk and could trace an accretion shock around the disk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21293371','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21293371"><span id="translatedtitle">A closely packed <span class="hlt">system</span> of <span class="hlt">low-mass</span>, low-density planets transiting Kepler-11.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lissauer, Jack J; Fabrycky, Daniel C; Ford, Eric B; Borucki, William J; Fressin, Francois; Marcy, Geoffrey W; Orosz, Jerome A; Rowe, Jason F; Torres, Guillermo; Welsh, William F; Batalha, Natalie M; Bryson, Stephen T; Buchhave, Lars A; Caldwell, Douglas A; Carter, Joshua A; Charbonneau, David; Christiansen, Jessie L; Cochran, William D; Desert, Jean-Michel; Dunham, Edward W; Fanelli, Michael N; Fortney, Jonathan J; Gautier, Thomas N; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer R; Holman, Matthew J; Koch, David G; Latham, David W; Lopez, Eric; McCauliff, Sean; Miller, Neil; Morehead, Robert C; Quintana, Elisa V; Ragozzine, Darin; Sasselov, Dimitar; Short, Donald R; Steffen, Jason H</p> <p>2011-02-01</p> <p>When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary <span class="hlt">systems</span>. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47 days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21293371','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21293371"><span id="translatedtitle">A closely packed <span class="hlt">system</span> of <span class="hlt">low-mass</span>, low-density planets transiting Kepler-11.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lissauer, Jack J; Fabrycky, Daniel C; Ford, Eric B; Borucki, William J; Fressin, Francois; Marcy, Geoffrey W; Orosz, Jerome A; Rowe, Jason F; Torres, Guillermo; Welsh, William F; Batalha, Natalie M; Bryson, Stephen T; Buchhave, Lars A; Caldwell, Douglas A; Carter, Joshua A; Charbonneau, David; Christiansen, Jessie L; Cochran, William D; Desert, Jean-Michel; Dunham, Edward W; Fanelli, Michael N; Fortney, Jonathan J; Gautier, Thomas N; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer R; Holman, Matthew J; Koch, David G; Latham, David W; Lopez, Eric; McCauliff, Sean; Miller, Neil; Morehead, Robert C; Quintana, Elisa V; Ragozzine, Darin; Sasselov, Dimitar; Short, Donald R; Steffen, Jason H</p> <p>2011-02-01</p> <p>When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary <span class="hlt">systems</span>. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47 days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation. PMID:21293371</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940026635','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940026635"><span id="translatedtitle">Gravitational instabilities in <span class="hlt">protostellar</span> disks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tohline, J. E.</p> <p>1994-01-01</p> <p>The nonaxisymmetric stability of self-gravitating, geometrically thick accretion disks has been studied for <span class="hlt">protostellar</span> <span class="hlt">systems</span> having a wide range of disk-to-central object mass ratios. Global eigenmodes with four distinctly different characters were identified using numerical, nonlinear hydrodynamic techniques. The mode that appears most likely to arise in normal star formation settings, however, resembles the 'eccentric instability' that was identified earlier in thin, nearly Keplerian disks: It presents an open, one-armed spiral pattern that sweeps continuously in a trailing direction through more than 2-pi radians, smoothly connecting the inner and outer edges of the disk, and requires cooperative motion of the point mass for effective amplification. This particular instability promotes the development of a single, self-gravitating clump of material in orbit about the point mass, so its routine appearance in our simulations supports the conjecture that the eccentric instability provides a primary route to the formation of short-period binaries in <span class="hlt">protostellar</span> <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010084309','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010084309"><span id="translatedtitle">The Discovery of a Second Luminous <span class="hlt">Low</span> <span class="hlt">Mass</span> X-Ray Binary <span class="hlt">System</span> in the Globular Cluster M15</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>White, Nicholas E.; Angelini, Lorella</p> <p>2001-01-01</p> <p>Using the Chandra X-ray Observatory we have discovered a second bright X-ray source in the globular cluster M15 that is 2.7" to the west of AC211, the previously known <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binary (LMXB) in this <span class="hlt">system</span>. Prior to the 0.5" imaging capability of Chandra this second source could not have been resolved from AC211. The luminosity and spectrum of this new source, which we call M15-X2, are consistent with it also being a LMXB <span class="hlt">system</span>. This is the first time that two LMXBs have been seen to be simultaneously active in a globular cluster. The new source, M15-X2, is coincident with a 18th U magnitude very blue star. The discovery of a second LMXB in M15 clears up a long standing puzzle where the X-ray and optical properties of AC211 appear consistent with the central source being hidden behind an accretion disk corona, and yet also showed a luminous X-ray burst suggesting the neutron star is directly visible. This discovery suggests instead that the X-ray burst did not come from AC211, but rather from the newly discovered X-ray source. We discuss the implications of this discovery for X-ray observations of globular clusters in nearby galaxies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999AJ....118.1784H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999AJ....118.1784H"><span id="translatedtitle">The Complex <span class="hlt">Protostellar</span> Source IRAS 04325+2402</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, Lee; Calvet, Nuria; Allen, Lori; Chen, Hua; Jayawardhana, Ray</p> <p>1999-10-01</p> <p>We report Hubble Space Telescope near-infrared NICMOS observations of a remarkable low-luminosity Class I (<span class="hlt">protostellar</span>) source in the Taurus Molecular Cloud. IRAS 04325+2402 exhibits a complex bipolar scattered light nebula. The central continuum source is resolved and may be multiple, or it may be crossed by a small dust lane. Complex arcs seen in scattered light surround the central source; the physical nature of these structures is not clear, but they may reflect perturbations from multiple stellar sources or from time-dependent mass ejection. A second, resolved continuum source is found at a projected distance of approximately 1150 AU from the central region, near the edge of a nebular lobe probably produced by outflow. The images indicate that this second source is another low-luminosity young stellar object, seen nearly edge-on through a dusty disk and envelope <span class="hlt">system</span> with disk diameter of about 60 AU. We suggest that the scattered light ``streaks'' associated with this second source are limb-brightened outflow cavities in the dusty envelope, possibly perturbed by interaction with the outflow lobes of the main source. The nature of the companion is uncertain, since it is observed mostly in scattered light. But it is most probably a very <span class="hlt">low</span> <span class="hlt">mass</span> star or brown dwarf, with a minimum luminosity of approximately 10^-2 L_solar. Our results show that <span class="hlt">protostellar</span> sources may have multiple centers of infall and nonaligned disks and outflows, even on relatively small scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.460.2223R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.460.2223R"><span id="translatedtitle">Gravitoturbulence in magnetized <span class="hlt">protostellar</span> discs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riols, A.; Latter, H.</p> <p>2016-08-01</p> <p>Gravitational instability (GI) features in several aspects of <span class="hlt">protostellar</span> disc evolution, most notably in angular momentum transport, fragmentation, and the outbursts exemplified by FU Ori and EX Lupi <span class="hlt">systems</span>. The outer regions of <span class="hlt">protostellar</span> discs may also be coupled to magnetic fields, which could then modify the development of GI. To understand the basic elements of their interaction, we perform local 2D ideal and resistive magnetohydrodynamics simulations with an imposed toroidal field. In the regime of moderate plasma beta, we find that the <span class="hlt">system</span> supports a hot gravitoturbulent state, characterized by considerable magnetic energy and stress and a surprisingly large Toomre parameter Q ≳ 10. This result has potential implications for disc structure, vertical thickness, ionization, etc. Our simulations also reveal the existence of long-lived and dense `magnetic islands' or plasmoids. Lastly, we find that the presence of a magnetic field has little impact on the fragmentation criterion of the disc. Though our focus is on <span class="hlt">protostellar</span> discs, some of our results may be relevant for the outer radii of AGN.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AJ....143..122Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AJ....143..122Y"><span id="translatedtitle">Deep, <span class="hlt">Low-mass</span> Ratio Overcontact Binary <span class="hlt">Systems</span>. XII. CK Bootis with Possible Cyclic Magnetic Activity and Additional Companion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Y.-G.; Qian, S.-B.; Soonthornthum, B.</p> <p>2012-05-01</p> <p>We present precision CCD photometry, a period study, and a two-color simultaneous Wilson code solution of the short-period contact binary CK Bootis. The asymmetric light curves were modeled by a dark spot on the primary component. The result identifies that CK Boo is an A-type W UMa binary with a high fillout of f = 71.7(± 4.4)%. From the O - C curve, it is found that the orbital period changes in a complicated mode, i.e., a long-term increase with two sinusoidal variations. One cyclic oscillation with a period of 10.67(± 0.20) yr may result from magnetic activity cycles, which are identified by the variability of Max. I - Max. II. Another sinusoidal variation (i.e., A = 0.0131 days(± 0.0009 days) and P 3 = 24.16(± 0.64) yr) may be attributed to the light-time effect due to a third body. This kind of additional companion can extract angular momentum from the central binary <span class="hlt">system</span>. The orbital period secularly increases at a rate of dP/dt = +9.79 (±0.80) × 10-8 days yr-1, which may be interpreted by conservative mass transfer from the secondary to the primary. This kind of deep, <span class="hlt">low-mass</span> ratio overcontact binaries may evolve into a rapid-rotating single star, only if the contact configuration do not break down at J spin > (1/3)J orb.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...567A..54R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...567A..54R"><span id="translatedtitle">Diversity of planetary <span class="hlt">systems</span> in <span class="hlt">low-mass</span> disks. Terrestrial-type planet formation and water delivery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ronco, M. P.; de Elía, G. C.</p> <p>2014-07-01</p> <p>Context. Several studies, observational and theoretical, suggest that planetary <span class="hlt">systems</span> with only rocky planets are the most common in the Universe. Aims: We study the diversity of planetary <span class="hlt">systems</span> that might form around Sun-like stars in <span class="hlt">low-mass</span> disks without gas-giant planets. We focus especially on the formation process of terrestrial planets in the habitable zone (HZ) and analyze their water contents with the goal to determine <span class="hlt">systems</span> of astrobiological interest. In addition, we study the formation of planets on wide orbits because they can be detected with the microlensing technique. Methods: N-body simulations of high resolution were developed for a wide range of surface density profiles. A bimodal distribution of planetesimals and planetary embryos with different physical and orbital configurations was used to simulate the planetary accretion process. The surface density profile combines a power law for the inside of the disk of the form r-γ, with an exponential decay to the outside. We performed simulations adopting a disk of 0.03 M⊙ and values of γ = 0.5, 1 and 1.5. Results: All our simulations form planets in the HZ with different masses and final water contents depending on the three different profiles. For γ = 0.5, our simulations produce three planets in the HZ with masses ranging from 0.03 M⊕ to 0.1 M⊕ and water contents between 0.2 and 16 Earth oceans (1 Earth ocean =2.8 × 10-4 M⊕). For γ = 1, three planets form in the HZ with masses between 0.18 M⊕ and 0.52 M⊕ and water contents from 34 to 167 Earth oceans. Finally, for γ = 1.5, we find four planets in the HZ with masses ranging from 0.66 M⊕ to 2.21 M⊕ and water contents between 192 and 2326 Earth oceans. This profile shows distinctive results because it is the only one of those studied here that leads to the formation of water worlds. Conclusions: Since planetary <span class="hlt">systems</span> with γ = 1 and 1.5 present planets in the HZ with suitable masses to retain a long-lived atmosphere and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...567A...2D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...567A...2D"><span id="translatedtitle">Luminosity function of <span class="hlt">low-mass</span> X-ray binaries in the globular cluster <span class="hlt">system</span> of NGC 1399</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Ago, G.; Paolillo, M.; Fabbiano, G.; Puzia, T. H.; Maccarone, T. J.; Kundu, A.; Goudfrooij, P.; Zepf, S. E.</p> <p>2014-07-01</p> <p>Aims: We present a study of the faint end of the X-ray luminosity function (XLF) of <span class="hlt">low-mass</span> X-ray binaries (LMXBs) in the Globular Cluster (GC) <span class="hlt">system</span> of the cD galaxy NGC 1399. Methods: We performed a stacking experiment on 618 X-ray undetected GCs, in order to verify the presence of faint LMXBs and to constrain the faint-end slope of the GC-LMXBs XLF below the individual detection threshold of 8 × 1037 erg s-1 in the 0.5 - 8 keV band. Results: We obtain a significant X-ray detection for the whole GC sample, as well as for the red and blue GC subpopulations, corresponding to an average luminosity per GC ⟨ LX ⟩ GC of (3.6 ± 1.0) × 1036 erg s-1, (6.9 ± 2.1) × 1036 erg s-1, and (1.7 ± 0.9) × 1036 erg s-1, respectively, for all GCs, red GCs, and blue GCs. If LMXBs in red and blue GCs have the same average intrinsic luminosity, we derive a red/blue ratio ≃3 of GCs hosting LMXBs (2.5 ± 1.0 or 4.1 ± 2.5 depending on the surveyed region); alternatively, assuming the fractions observed for brighter sources, we measure an average X-ray luminosity of LX = (4.3 ± 1.3) × 1037 erg s-1 and LX = (3.4 ± 1.7) × 1037 erg s-1 per red and blue GC-LMXBs, respectively. In the assumption that the XLF follows a power-law distribution, we find that a low-luminosity break is required at LX ≤ 8 × 1037 erg s-1 both in the whole, as well as in the color-selected (red and blue) subsamples. Given the bright-end slopes measured above the X-ray completeness limit, this result is significant at >3σ level. Our best estimates for the faint-end slope are βL = -1.39/-1.38/-1.36 for all/red/blue GC-LMXBs. We also find evidence that the luminosity function becomes steeper at luminosities LX ≳ 3 × 1039 erg s-1, as observed in old ellipticals. Conclusions: If most GCs host a single X-ray binary, we conclude that in NGC 1399 the XLF flattens at low luminosities as observed in other nearer galaxies, and we discuss some consequences of this flattening on LMXBs formation scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22370208','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22370208"><span id="translatedtitle">Angular momentum exchange by gravitational torques and infall in the circumbinary disk of the <span class="hlt">protostellar</span> <span class="hlt">system</span> L1551 NE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Takakuwa, Shigehisa; Ho, Paul T. P.; Saito, Masao; Saigo, Kazuya; Matsumoto, Tomoaki; Lim, Jeremy; Hanawa, Tomoyuki</p> <p>2014-11-20</p> <p>We report an ALMA observation of the Class I binary <span class="hlt">protostellar</span> <span class="hlt">system</span> L1551 NE in the 0.9 mm continuum, C{sup 18}O (3-2), and {sup 13}CO (3-2) lines at a ∼1.6 times higher resolution and a ∼6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ∼ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the <span class="hlt">systemic</span> velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary <span class="hlt">system</span> are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms. The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ApJ...796....1T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014ApJ...796....1T&link_type=ABSTRACT"><span id="translatedtitle">Angular Momentum Exchange by Gravitational Torques and Infall in the Circumbinary Disk of the <span class="hlt">Protostellar</span> <span class="hlt">System</span> L1551 NE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takakuwa, Shigehisa; Saito, Masao; Saigo, Kazuya; Matsumoto, Tomoaki; Lim, Jeremy; Hanawa, Tomoyuki; Ho, Paul T. P.</p> <p>2014-11-01</p> <p>We report an ALMA observation of the Class I binary <span class="hlt">protostellar</span> <span class="hlt">system</span> L1551 NE in the 0.9 mm continuum, C18O (3-2), and 13CO (3-2) lines at a ~1.6 times higher resolution and a ~6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ~ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the <span class="hlt">systemic</span> velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary <span class="hlt">system</span> are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms. The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014sofi.prop..140K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014sofi.prop..140K"><span id="translatedtitle">Where is the oxygen in <span class="hlt">protostellar</span> outflows?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristensen, Lars</p> <p>2014-10-01</p> <p>Oxygen (O) is the third-most abundant element in the Universe after hydrogen and helium. Despite its high elemental abundance, a good picture of where oxygen is located in <span class="hlt">low-mass</span> <span class="hlt">protostellar</span> outflows and jets is missing: we cannot account for > 60% of the oxygen budget in these objects. This hole in our picture means that we currently do not have a good understanding of the dominant cooling processes in outflows jets, despite the fact that [O I] emission at 63 micron is one of the dominant cooling lines, nor how cooling processes evolve with <span class="hlt">protostellar</span> evolution. To shed light on these processes, we propose to observe the [O I] 63 micron line with SOFIA-GREAT toward five <span class="hlt">low-mass</span> protostars. As a first step, the velocity-resolved line profile will be decomposed into its constituent components to isolate the relative contributions from the jet and the irradiated outflow. Second, the [O I] line profile will be compared to those of H2O, OH and CO to obtain the relative atomic O abundance with respect to CO, H2O, and OH. Third, the effects of evolution will be examined by observing protostars at different evolutionary stages. These three approaches will allow us to quantify: the oxygen chemistry in warm and hot gas, the relative amounts of material in the outflow and the jet, and finally to start tracing the evolutionary sequence of how feedback evolves with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013prpl.conf1B066C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013prpl.conf1B066C&link_type=ABSTRACT"><span id="translatedtitle">Deuterated water in <span class="hlt">low-mass</span> protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coutens, Audrey; Vastel, Charlotte; Chess Collaboration; Wish Collaboration; Hexos Collaboration</p> <p>2013-07-01</p> <p>In addition to its dominant role in the cooling of warm gas and in the oxygen chemistry, water is a primordial species in the emergence of life, and comets may have brought a large fraction to Earth to form the oceans. Observations of deuterated water are an important complement for studies of H2O to understand how water forms and how it has evolved from cold prestellar cores to protoplanetary disks and consequently oceans for the Earth's specific, but probably not isolated, case. Several deuterated water transitions were observed with the Herschel/HIFI (Heterodyne Instrument for Far Infrared) instrument towards three <span class="hlt">low-mass</span> protostars: IRAS 16293-2422, NGC1333 IRAS4A and NGC1333 IRAS4B. In the first source, both HDO and D2O lines are detected, thanks to the unbiased spectral survey carried out by the CHESS key program (Vastel et al. 2010, Coutens et al. 2013a). In the framework of a collaboration between the CHESS, WISH and HEXOS programs, two HDO key lines were observed towards the two other protostars. In addition, complementary observations were carried out with several ground-based single-dish telescopes (IRAM-30m, JCMT, APEX). We used the non-LTE RATRAN spherical model (Hogerheijde & van der Tak 2000) to determine the HDO abundance distribution throughout the <span class="hlt">protostellar</span> envelope. An abundance jump at 100 K is required to reproduce the line profiles. Indeed, water molecules trapped in the icy grain mantles thermally desorb in the hot corinos, the inner warm regions of the <span class="hlt">protostellar</span> envelopes. We also obtain that it is necessary to add a water-rich external absorbing layer to reproduce the absorbing components of the HDO and D2O fundamental transitions in all sources (Coutens et al. 2012, 2013a,b). The results derived for the different sources will be then presented and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990047717','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990047717"><span id="translatedtitle">Planet Forming <span class="hlt">Protostellar</span> Disks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lubow, Stephen</p> <p>1998-01-01</p> <p>The project achieved many of its objectives. The main area of investigation was the interaction of young binary stars with surrounding <span class="hlt">protostellar</span> disks. A secondary objective was the interaction of young planets with their central stars and surrounding disks. The grant funds were used to support visits by coinvestigators and visitors: Pawel Artymowicz, James Pringle, and Gordon Ogilvie. Funds were also used to support travel to meetings by Lubow and to provide partial salary support.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998larm.confE..61V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998larm.confE..61V"><span id="translatedtitle"><span class="hlt">Protostellar</span> Jets: Numerical Simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vitorino, B. F.; Jatenco-Pereira, V.; Opher, R.</p> <p>1998-11-01</p> <p>Numerical simulations of astrophysical jets have been made in order to study their collimation and internal structure. Recently Ouyed & Pudritz (1997) did numerical simulations of axi-simetric magnetocentrifugal jets from a keplerian acretion disk employing the eulerian finite difference code Zeus-2D. During their simulation, it was raised a steady state jet confirming a lot of results of the MHD winds steady state theory. Following this scenario we did tridimensional numerial simulations of this model allowing the jet, after a perturbation, evolve into a not steady state producing the helical features observed in some <span class="hlt">protostellar</span> jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22340299','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22340299"><span id="translatedtitle">The solar neighborhood. XXXIII. Parallax results from the CTIOPI 0.9 m program: trigonometric parallaxes of Nearby <span class="hlt">low-mass</span> active and young <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Riedel, Adric R.; Cruz, Kelle L.; Finch, Charlie T.; Henry, Todd J.; Jao, Wei-Chun; White, Russel J.; Gies, Douglas R.; Dieterich, Sergio B.; Winters, Jennifer G.; Davison, Cassy L.; Subasavage, John P.; Malo, Lison; Rodriguez, David R.; Nelan, Edmund P.; Blunt, Sarah C.; Rice, Emily L.; Ianna, Philip A.</p> <p>2014-04-01</p> <p>We present basic observational data and association membership analysis for 45 young and active <span class="hlt">low-mass</span> stellar <span class="hlt">systems</span> from the ongoing Research Consortium On Nearby Stars photometry and astrometry program at the Cerro Tololo Inter-American Observatory. Most of these <span class="hlt">systems</span> have saturated X-ray emission (log (L{sub X} /L {sub bol}) > –3.5) based on X-ray fluxes from the ROSAT All-Sky Survey, and many are significantly more luminous than main-sequence stars of comparable color. We present parallaxes and proper motions, Johnson-Kron-Cousins VRI photometry, and multiplicity observations from the CTIOPI program on the CTIO 0.9 m telescope. To this we add low-resolution optical spectroscopy and line measurements from the CTIO 1.5 m telescope, and interferometric binary measurements from the Hubble Space Telescope Fine Guidance Sensors. We also incorporate data from published sources: JHK{sub S} photometry from the Two Micron All Sky Survey point source catalog, X-ray data from the ROSAT All-Sky Survey, and radial velocities from literature sources. Within the sample of 45 <span class="hlt">systems</span>, we identify 21 candidate <span class="hlt">low-mass</span> pre-main-sequence members of nearby associations, including members of β Pictoris, TW Hydrae, Argus, AB Doradus, two ambiguous ≈30 Myr old <span class="hlt">systems</span>, and one object that may be a member of the Ursa Major moving group. Of the 21 candidate young <span class="hlt">systems</span>, 14 are newly identified as a result of this work, and six of those are within 25 pc of the Sun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21583226','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21583226"><span id="translatedtitle">IDENTIFICATION OF A WIDE, <span class="hlt">LOW-MASS</span> MULTIPLE <span class="hlt">SYSTEM</span> CONTAINING THE BROWN DWARF 2MASS J0850359+105716</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Faherty, Jacqueline K.; Burgasser, Adam J.; Bochanski, John J.; Looper, Dagny L.; West, Andrew A.; Van der Bliek, Nicole S.</p> <p>2011-03-15</p> <p>We report our discovery of NLTT 20346 as an M5+M6 companion <span class="hlt">system</span> to the tight binary (or triple) L dwarf 2MASS J0850359+105716. This nearby ({approx}31 pc), widely separated ({approx}7700 AU) quadruple <span class="hlt">system</span> was identified through a cross-match of proper motion catalogs. Follow-up imaging and spectroscopy of NLTT 20346 revealed it to be a magnetically active M5+M6 binary with components separated by {approx}2'' (50-80 AU). Optical spectroscopy of the components shows only moderate H{alpha} emission corresponding to a statistical age of {approx}5-7 Gyr for both M dwarfs. However, NLTT 20346 is associated with the XMM-Newton source J085018.9+105644, and based on X-ray activity the age of NLTT 20346 is between 250 and 450 Myr. Strong Li absorption in the optical spectrum of 2MASS J0850+1057 indicates an upper age limit of 0.8-1.5 Gyr, favoring the younger age for the primary. Using evolutionary models in combination with an adopted <span class="hlt">system</span> age of 0.25-1.5 Gyr indicates a total mass for 2MASS J0850+1057 of 0.07 {+-} 0.02 M{sub sun}, if it is a binary. NLTT 20346/2MASS J0850+1057 joins a growing list of hierarchical <span class="hlt">systems</span> containing brown dwarf binaries and is among the lowest binding energy associations found in the field. Formation simulations via gravitational fragmentation of massive extended disks have successfully produced a specific analog to this <span class="hlt">system</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...806..148B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...806..148B"><span id="translatedtitle">Coordinated X-Ray, Ultraviolet, Optical, and Radio Observations of the PSR J1023+0038 <span class="hlt">System</span> in a <span class="hlt">Low-mass</span> X-Ray Binary State</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bogdanov, Slavko; Archibald, Anne M.; Bassa, Cees; Deller, Adam T.; Halpern, Jules P.; Heald, George; Hessels, Jason W. T.; Janssen, Gemma H.; Lyne, Andrew G.; Moldón, Javier; Paragi, Zsolt; Patruno, Alessandro; Perera, Benetge B. P.; Stappers, Ben W.; Tendulkar, Shriharsh P.; D'Angelo, Caroline R.; Wijnands, Rudy</p> <p>2015-06-01</p> <p>The PSR J1023+0038 binary <span class="hlt">system</span> hosts a neutron star and a <span class="hlt">low-mass</span>, main-sequence-like star. It switches on year timescales between states as an eclipsing radio millisecond pulsar and a <span class="hlt">low-mass</span> X-ray binary (LMXB). We present a multi-wavelength observational campaign of PSR J1023+0038 in its most recent LMXB state. Two long XMM-Newton observations reveal that the <span class="hlt">system</span> spends ˜70% of the time in a ≈3 × 1033 erg s-1 X-ray luminosity mode, which, as shown in Archibald et al., exhibits coherent X-ray pulsations. This emission is interspersed with frequent lower flux mode intervals with ≈ 5× {10}32 erg s-1 and sporadic flares reaching up to ≈1034 erg s-1, with neither mode showing significant X-ray pulsations. The switches between the three flux modes occur on timescales of order 10 s. In the UV and optical, we observe occasional intense flares coincident with those observed in X-rays. Our radio timing observations reveal no pulsations at the pulsar period during any of the three X-ray modes, presumably due to complete quenching of the radio emission mechanism by the accretion flow. Radio imaging detects highly variable, flat-spectrum continuum radiation from PSR J1023+0038, consistent with an origin in a weak jet-like outflow. Our concurrent X-ray and radio continuum data sets do not exhibit any correlated behavior. The observational evidence we present bears qualitative resemblance to the behavior predicted by some existing “propeller” and “trapped” disk accretion models although none can account for key aspects of the rich phenomenology of this <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000057044','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000057044"><span id="translatedtitle">Chemical Evolution of <span class="hlt">Protostellar</span> Matter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Langer, William D.; vanDishoeck, Ewine F.; Bergin, Edwin A.; Blake, Geoffrey A.; Tielens, Alexander G. G. M.; Velusamy, Thangasamy; Whittet, Douglas C. B.</p> <p>2000-01-01</p> <p>We review the chemical processes that are important in the evolution from a molecular cloud core to a <span class="hlt">protostellar</span> disk. These cover both gas phase and gas grain interactions. The current observational and theoretical state of this field are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009A%26A...503..873H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009A%26A...503..873H"><span id="translatedtitle">The triple <span class="hlt">system</span> HIP 96515: a <span class="hlt">low-mass</span> eclipsing binary with a DB white dwarf companion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huélamo, N.; Vaz, L. P. R.; Torres, C. A. O.; Bergeron, P.; Melo, C. H. F.; Quast, G. R.; Barrado y Navascués, D.; Sterzik, M. F.; Chauvin, G.; Bouy, H.; Landin, N. R.</p> <p>2009-09-01</p> <p>Context: HIP 96515 A is a double-lined spectroscopic binary included in the SACY catalog as a potential young star. It has a visual companion (CCDM 19371-5134 B, HIP 96515 B) at 8.6 arcsec. If bound to the primary, the optical and infrared colors of this wide companion are consistent with those of a white dwarf. Aims: We attempt to characterize the <span class="hlt">system</span> HIP 96515 A&B by studying each of its components. Methods: We analyzed spectroscopic and photometric observations of HIP 96515 A and its visual companion, HIP 96515 B. To confirm the <span class="hlt">system</span> as a common proper-motion pair, we analyzed the astrometry of the components using high-angular resolution infrared observations obtained within a time span of two years, and archival astrometry. Results: The high-resolution optical spectrum of HIP 96515 A was used to derive a mass ratio, M_2/M_1, close to 0.9. The optical lightcurve of HIP 96515 A shows periodic variations with P_orbital = 2.3456 days, revealing that HIP 96515 A is an eclipsing binary with preliminary orbital parameters of i = 89.0° ± 0.2°, and M1 = 0.59 ± 0.03 M⊙ and M2 = 0.54 ± 0.03 M⊙, for the primary and secondary, respectively, at an estimated distance of 42 ± 3 pc. This is a new eclipsing binary with component masses below 0.6 M⊙. Multi-epoch observations of HIP 96515 A&B show that the <span class="hlt">system</span> is a common proper-motion pair. The optical spectrum of HIP 96515 B is consistent with a pure helium atmosphere (DB) white dwarf. The comparison with evolutionary cooling sequence models provides Teff,WD = 19 126 ± 195 K, log gWD = 8.08, MWD/M⊙ = 0.6, and a distance of ~46 pc. The estimated WD cooling age is ~100 Myr and the total age of the object (including the main-sequence phase) is ~400 Myr. Finally, if HIP 96515 A&B are coeval, and assuming a common age of ~400 Myr, the comparison of the masses of the eclipsing binary members with evolutionary tracks shows that they are underestimated by ~15% and 10%, for the primary and secondary, respectively</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E2187Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E2187Z"><span id="translatedtitle">On the evolutionary status of the donors in the <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binary <span class="hlt">systems</span> containing black holes or neutron stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ziolkowski, Janusz</p> <p>2016-07-01</p> <p>We consider donors (optical components) in four <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binaries: two black hole <span class="hlt">systems</span> (GRS1915+105/V1387 Aql and GS 2023+338/V404 Cyg) and two neutron star <span class="hlt">systems</span> (X2127+119 and IGR J17451-3022). In all four cases we found that donors are most likely so called "stripped" giants. Such star consists of a degenerate, nearly isothermal helium core and a more or less depleted hydrogen rich envelope. Both parts are separated by a hydrogen burning shell. The structure of such an object is relatively simple and easy to model. In all four <span class="hlt">systems</span> we can estimate relatively precisely the radii of the donors (which depend almost exclusively on the orbital periods). In two black hole <span class="hlt">systems</span> we can additionally estimate their luminosities. Analysing the internal structure of the donors, we found that they could be "stripped" giants in all four <span class="hlt">systems</span>. The likely masses are ~ 0.28 Msun for V1387 Aql, ~ 0.54 Msun for V404 Cyg, ~ 0.16-0.17 Msun for the companion of X2127+119 and ~ 0.15-0.2 Msun for the companion of IGR J17451-3022. For the last <span class="hlt">system</span> another possible solution is a MS star of ~ 0.75 Msun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100010918','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100010918"><span id="translatedtitle">Modeling of Radiative Transfer in <span class="hlt">Protostellar</span> Disks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>VonAllmen, Paul; Turner, Neal</p> <p>2007-01-01</p> <p>This program implements a spectral line, radiative transfer tool for interpreting Spitzer Space Telescope observations by matching them with models of <span class="hlt">protostellar</span> disks for improved understanding of planet and star formation. The Spitzer Space Telescope detects gas phase molecules in the infrared spectra of <span class="hlt">protostellar</span> disks, with spectral lines carrying information on the chemical composition of the material from which planets form. Input to the software includes chemical models developed at JPL. The products are synthetic images and spectra for comparison with Spitzer measurements. Radiative transfer in a <span class="hlt">protostellar</span> disk is primarily affected by absorption and emission processes in the dust and in molecular gases such as H2, CO, and HCO. The magnitude of the optical absorption and emission is determined by the population of the electronic, vibrational, and rotational energy levels. The population of the molecular level is in turn determined by the intensity of the radiation field. Therefore, the intensity of the radiation field and the population of the molecular levels are inter-dependent quantities. To meet the computational challenges of solving for the coupled radiation field and electronic level populations in disks having wide ranges of optical depths and spatial scales, the tool runs in parallel on the JPL Dell Cluster supercomputer with C++ and Fortran compiler with a Message Passing Interface. Because this software has been developed on a distributed computing platform, the modeling of <span class="hlt">systems</span> previously beyond the reach of available computational resources is possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840024258','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840024258"><span id="translatedtitle">Studies of <span class="hlt">low-mass</span> star formation with the large deployable reflector</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hollenbach, D. J.; Tielens, Alexander G. G. M.</p> <p>1984-01-01</p> <p>Estimates are made of the far-infrared and submillimeter continuum and line emission from regions of <span class="hlt">low</span> <span class="hlt">mass</span> star formation. The intensity of this emission is compared with the sensitivity of the large deployable reflector (LDR), a large space telescope designed for this wavelength range. The proposed LDR is designed to probe the temperature, density, chemical structure, and the velocity field of the collapsing envelopes of these protostars. The LDR is also designed to study the accretion shocks on the cores and circumstellar disks of <span class="hlt">low-mass</span> protostars, and to detect shock waves driven by <span class="hlt">protostellar</span> winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21452902','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21452902"><span id="translatedtitle">THIRTY NEW <span class="hlt">LOW-MASS</span> SPECTROSCOPIC BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shkolnik, Evgenya L.; Hebb, Leslie; Cameron, Andrew C.; Liu, Michael C.; Neill Reid, I. E-mail: Andrew.Cameron@st-and.ac.u E-mail: mliu@ifa.hawaii.ed</p> <p>2010-06-20</p> <p>As part of our search for young M dwarfs within 25 pc, we acquired high-resolution spectra of 185 <span class="hlt">low-mass</span> stars compiled by the NStars project that have strong X-ray emission. By cross-correlating these spectra with radial velocity standard stars, we are sensitive to finding multi-lined spectroscopic binaries. We find a <span class="hlt">low-mass</span> spectroscopic binary fraction of 16% consisting of 27 SB2s, 2 SB3s, and 1 SB4, increasing the number of known <span class="hlt">low-mass</span> spectroscopic binaries (SBs) by 50% and proving that strong X-ray emission is an extremely efficient way to find M-dwarf SBs. WASP photometry of 23 of these <span class="hlt">systems</span> revealed two <span class="hlt">low-mass</span> eclipsing binaries (EBs), bringing the count of known M-dwarf EBs to 15. BD-22 5866, the ESB4, was fully described in 2008 by Shkolnik et al. and CCDM J04404+3127 B consists of two mid-M stars orbiting each other every 2.048 days. WASP also provided rotation periods for 12 <span class="hlt">systems</span>, and in the cases where the synchronization time scales are short, we used P{sub rot} to determine the true orbital parameters. For those with no P{sub rot}, we used differential radial velocities to set upper limits on orbital periods and semimajor axes. More than half of our sample has near-equal-mass components (q > 0.8). This is expected since our sample is biased toward tight orbits where saturated X-ray emission is due to tidal spin-up rather than stellar youth. Increasing the samples of M-dwarf SBs and EBs is extremely valuable in setting constraints on current theories of stellar multiplicity and evolution scenarios for <span class="hlt">low-mass</span> multiple <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...582A..41H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...582A..41H"><span id="translatedtitle">Volatile snowlines in embedded disks around <span class="hlt">low-mass</span> protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harsono, D.; Bruderer, S.; van Dishoeck, E. F.</p> <p>2015-10-01</p> <p>Context. Models of the young solar nebula assume a hot initial disk in which most volatiles are in the gas phase. Water emission arising from within 50 AU radius has been detected around <span class="hlt">low-mass</span> embedded young stellar objects. The question remains whether an actively accreting disk is warm enough to have gas-phase water up to 50 AU radius. No detailed studies have yet been performed on the extent of snowlines in an accreting disk embedded in a dense envelope (stage 0). Aims: We aim to quantify the location of gas-phase volatiles in the inner envelope and disk <span class="hlt">system</span> for an actively accreting embedded disk. Methods: Two-dimensional physical and radiative transfer models were used to calculate the temperature structure of embedded <span class="hlt">protostellar</span> <span class="hlt">systems</span>. Heating due to viscous accretion was added through the diffusion approximation. Gas and ice abundances of H2O, CO2, and CO were calculated using the density-dependent thermal desorption formulation. Results: The midplane water snowline increases from 3 to ~55 AU for accretion rates through the disk onto the star between 10-9-10-4M⊙ yr-1. CO2 can remain in the solid phase within the disk for Ṁ ≤ 10-5M⊙ yr-1 down to ~20 AU. Most of the CO is in the gas phase within an actively accreting disk independent of disk properties and accretion rate. The predicted optically thin water isotopolog emission is consistent with the detected H218O emission toward the stage 0 embedded young stellar objects, originating from both the disk and the warm inner envelope (hot core). An accreting embedded disk can only account for water emission arising from R< 50 AU, however, and the extent rapidly decreases for Ṁ ≤ 10-5M⊙ yr-1. Thus, the radial extent of the emission can be measured with future ALMA observations and compared to this 50 AU limit. Conclusions: Volatiles such as H2O, CO2, CO, and the associated complex organics sublimate out to 50 AU in the midplane of young disks and, thus, can reset the chemical content</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17280269','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17280269"><span id="translatedtitle">Study of decay mechanisms in B--->Lambdac+ppi- decays and observation of <span class="hlt">low-mass</span> structure in the Lambdac+p <span class="hlt">system</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gabyshev, N; Abe, K; Abe, K; Adachi, I; Aihara, H; Asano, Y; Aulchenko, V; Aushev, T; Bakich, A M; Bitenc, U; Bizjak, I; Blyth, S; Bondar, A; Bozek, A; Bracko, M; Brodzicka, J; Browder, T E; Chang, P; Chao, Y; Chen, A; Chen, W T; Cheon, B G; Chistov, R; Choi, S-K; Choi, Y; Chuvikov, A; Cole, S; Dalseno, J; Danilov, M; Dash, M; Drutskoy, A; Eidelman, S; Enari, Y; Fratina, S; Gershon, T; Gokhroo, G; Golob, B; Gorisek, A; Hara, T; Hayashii, H; Hazumi, M; Hokuue, T; Hoshi, Y; Hou, S; Hou, W-S; Hsiung, Y B; Iijima, T; Imoto, A; Inami, K; Ishikawa, A; Itoh, R; Iwasaki, M; Iwasaki, Y; Kang, J H; Kang, J S; Kataoka, S U; Katayama, N; Kawai, H; Kawasaki, T; Khan, H R; Kichimi, H; Kim, H J; Kim, H O; Kim, S K; Kim, S M; Kinoshita, K; Korpar, S; Krokovny, P; Kumar, S; Kuo, C C; Kuzmin, A; Kwon, Y-J; Lange, J S; Leder, G; Lesiak, T; Lin, S-W; Mandl, F; Matsumoto, T; Mikami, Y; Mitaroff, W; Miyake, H; Miyata, H; Mizuk, R; Nagamine, T; Nagasaka, Y; Nakano, E; Nakao, M; Nakazawa, H; Natkaniec, Z; Nishida, S; Nitoh, O; Ogawa, S; Ohshima, T; Okabe, T; Okuno, S; Olsen, S L; Onuki, Y; Ozaki, H; Palka, H; Park, C W; Park, H; Parslow, N; Peak, L S; Pestotnik, R; Piilonen, L E; Rozanska, M; Sagawa, H; Sakai, Y; Sato, N; Schietinger, T; Schneider, O; Schwartz, A J; Senyo, K; Seuster, R; Sevior, M E; Shibuya, H; Sidorov, V; Singh, J B; Somov, A; Stamen, R; Stanic, S; Staric, M; Sumiyoshi, T; Suzuki, S Y; Tajima, O; Takasaki, F; Tamai, K; Tamura, N; Tanaka, M; Teramoto, Y; Tian, X C; Tsuboyama, T; Tsukamoto, T; Uehara, S; Uglov, T; Ueno, K; Uno, S; Urquijo, P; Varner, G; Varvell, K E; Villa, S; Wang, C H; Wang, M-Z; Xie, Q L; Yabsley, B D; Yamaguchi, A; Yamamoto, H; Yamashita, Y; Yamauchi, M; Yang, Heyoung; Zhang, C C; Zhang, J; Zhang, L M; Zhang, Z P; Zhilich, V; Zontar, D</p> <p>2006-12-15</p> <p>Using a sample of 152 x 10(6) BB pairs accumulated with the Belle detector at the KEKB e+e- collider, we study the decay mechanism of three-body charmed decay B- --> Lambdac+ ppi-. The intermediate two-body decay B--->Sigmac (2455)0 p is observed for the first time with a branching fraction of (3.7 +/- 0.7 +/- 0.4 +/- 1.0) x 10(-5) and a statistical significance of 8.4sigma. We also observe a <span class="hlt">low-mass</span> enhancement in the (Lambdac+p) <span class="hlt">system</span>, which can be parametrized as a Breit-Wigner function with a mass of (3.35(-0.02)(+0.01) +/-0.02) GeV/c2 and a width of (0.07(-0.03)(+0.04) +/-0.04) GeV/c2. We measure its branching fraction to be (3.9(-0.7)(+0.8) +/- 0.4 +/- 1.0) x 10(-5) with a statistical significance of 6.2sigma. The errors are statistical, systematic, and that of the Lambdac+-->pK- pi+ decay branching fraction. PMID:17280269</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22522052','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22522052"><span id="translatedtitle">NEW EXTINCTION AND MASS ESTIMATES FROM OPTICAL PHOTOMETRY OF THE VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> BROWN DWARF COMPANION CT CHAMAELEONTIS B WITH THE MAGELLAN AO <span class="hlt">SYSTEM</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, Ya-Lin; Close, Laird M.; Males, Jared R.; Morzinski, Katie M.; Follette, Katherine B.; Bailey, Vanessa; Rodigas, Timothy J.; Hinz, Philip; Barman, Travis S.; Puglisi, Alfio; Xompero, Marco; Briguglio, Runa</p> <p>2015-03-01</p> <p>We used the Magellan adaptive optics <span class="hlt">system</span> and its VisAO CCD camera to image the young <span class="hlt">low</span> <span class="hlt">mass</span> brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r', i', z', and Y{sub S}. With our new photometry and T {sub eff} ∼ 2500 K derived from the shape of its K-band spectrum, we find that CT Cha B has A{sub V} = 3.4 ± 1.1 mag, and a mass of 14-24 M{sub J} according to the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r' detection indicates that the companion has significant Hα emission and a mass accretion rate ∼6 × 10{sup –10} M {sub ☉} yr{sup –1}, similar to some substellar companions. Proper motion analysis shows that another point source within 2'' of CT Cha A is not physical. This paper demonstrates how visible wavelength adaptive optics photometry (r', i', z', Y{sub S}) allows for a better estimate of extinction, luminosity, and mass accretion rate of young substellar companions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988ASSL..148..105S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988ASSL..148..105S"><span id="translatedtitle">Winds from <span class="hlt">Low</span> <span class="hlt">Mass</span> Protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shu, Frank H.; Lizano, Susana; Adams, Fred C.; Ruden, Steven P.</p> <p></p> <p>In its last stages, star formation in molecular clouds includes the onset of a stellar wind that helps to clear away the surrounding placenta of gas and dust, thereby making the young stellar object optically visible. The authors discuss new observational evidence that the emerging wind is largely neutral and atomic in <span class="hlt">low-mass</span> protostars. They then suggest a simple theoretical mechanism for the generation of such powerful neutral winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...590A.115V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...590A.115V"><span id="translatedtitle">Ejection of gaseous clumps from gravitationally unstable <span class="hlt">protostellar</span> disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vorobyov, E. I.</p> <p>2016-05-01</p> <p>Aims: We investigate the dynamics of gaseous clumps formed via gravitational fragmentation in young <span class="hlt">protostellar</span> disks, focusing on the fragments that are ejected from the disk via many-body gravitational interaction. Methods: Numerical hydrodynamics simulations were employed to study the evolution of young <span class="hlt">protostellar</span> disks that were formed from the collapse of rotating pre-stellar cores. Results: The <span class="hlt">protostellar</span> disks that formed in our models undergo gravitational fragmentation driven by continuing mass-loading from parental collapsing cores. Several fragments can be ejected from the disk during the early evolution, but the <span class="hlt">low-mass</span> fragments (<15 MJup) disperse, which creates spectacular bow-type structures while passing through the disk and collapsing core. The least massive fragment that survived the ejection (21 MJup) straddles the planetary-mass limit, while the most massive ejected fragments (145 MJup) can break up into several pieces, leading to the ejection of wide separation binary clumps in the brown-dwarf mass range. About half of the ejected fragments are gravitationally bound, the majority are supported by rotation against gravity, and all fragments have the specific angular momentum that is much higher than that expected for brown dwarfs. We found that the internal structure of the ejected fragments is distinct from what would be expected for gravitationally contracting clumps formed via molecular cloud fragmentation, which can help in differentiating their origin. Conclusions: The ejection of fragments is an important process, which is inherent to massive <span class="hlt">protostellar</span> disks, and which produces freely floating pre-brown dwarf cores, regulates the disk and stellar masses and, potentially, enriches the intracluster medium with processed dust and complex organics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011A%26A...527A..14H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011A%26A...527A..14H"><span id="translatedtitle">Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue. III. Two new <span class="hlt">low-mass</span> <span class="hlt">systems</span> with rapidly evolving spots</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hełminiak, K. G.; Konacki, M.; Złoczewski, K.; Ratajczak, M.; Reichart, D. E.; Ivarsen, K. M.; Haislip, J. B.; Crain, J. A.; Foster, A. C.; Nysewander, M. C.; Lacluyze, A. P.</p> <p>2011-03-01</p> <p>Aims: We present the results of our spectroscopic and photometric analysis of two newly discovered <span class="hlt">low-mass</span> detached eclipsing binaries found in the All-Sky Automated Survey (ASAS) catalogue: ASAS J093814-0104.4 and ASAS J212954-5620.1. Methods: Using the Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) on the 1.9-m Radcliffe telescope at the South African Astronomical Observatory (SAAO) and the University College London Echelle Spectrograph (UCLES) on the 3.9-m Anglo-Australian Telescope, we obtained high-resolution spectra of both objects and derived their radial velocities (RVs) at various orbital phases. The RVs of both objects were measured with the two-dimensional cross-correlation technique (TODCOR) using synthetic template spectra as references. We also obtained V and I band photometry using the 1.0-m Elizabeth telescope at SAAO and the 0.4-m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) located at the Cerro Tololo Inter-American Observatory (CTIO). The orbital and physical parameters of the <span class="hlt">systems</span> were derived with PHOEBE and JKTEBOP codes. We compared our results with several sets of widely-used isochrones. Results: Our multi-epoch photometric observations demonstrate that both objects show significant out-of-eclipse modulations, which vary in time. We believe that this effect is caused by stellar spots, which evolve on time scales of tens of days. For this reason, we constructed our models on the basis of photometric observations spanning short time scales (less than a month). Our modeling indicates that (1) ASAS J093814-0104.04 is a main sequence active <span class="hlt">system</span> with nearly-twin components with masses of M1 = 0.771 ± 0.033 M⊙, M2 = 0.768 ± 0.021 M⊙ and radii of R1 = 0.772 ± 0.012 R⊙ and R2 = 0.769 ± 0.013 R⊙. (2) ASAS J212954-5620.1 is a main sequence active binary with component masses of M1 = 0.833 ± 0.017 M⊙, M2 = 0.703 ± 0.013 M⊙ and radii of R1 = 0.845 ± 0.012 R⊙ and R2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22356924','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22356924"><span id="translatedtitle">ALMA results of the pseudodisk, rotating disk, and jet in the continuum and HCO{sup +} in the <span class="hlt">protostellar</span> <span class="hlt">system</span> HH 212</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lee, Chin-Fei; Hirano, Naomi; Shang, Hsien; Ho, Paul T. P.; Krasnopolsky, Ruben; Zhang, Qizhou</p> <p>2014-05-10</p> <p>HH 212 is a nearby (400 pc) Class 0 <span class="hlt">protostellar</span> <span class="hlt">system</span> showing several components that can be compared with theoretical models of core collapse. We have mapped it in the 350 GHz continuum and HCO{sup +} J = 4-3 emission with ALMA at up to ∼0.''4 resolution. A flattened envelope and a compact disk are seen in the continuum around the central source, as seen before. The HCO{sup +} kinematics shows that the flattened envelope is infalling with small rotation (i.e., spiraling) into the central source, and thus can be identified as a pseudodisk in the models of magnetized core collapse. Also, the HCO{sup +} kinematics shows that the disk is rotating and can be rotationally supported. In addition, to account for the missing HCO{sup +} emission at low-redshifted velocity, an extended infalling envelope is required, with its material flowing roughly parallel to the jet axis toward the pseudodisk. This is expected if it is magnetized with an hourglass B-field morphology. We have modeled the continuum and HCO{sup +} emission of the flattened envelope and disk simultaneously. We find that a jump in density is required across the interface between the pseudodisk and the disk. A jet is seen in HCO{sup +} extending out to ∼500 AU away from the central source, with the peaks upstream of those seen before in SiO. The broad velocity range and high HCO{sup +} abundance indicate that the HCO{sup +} emission traces internal shocks in the jet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999ARep...43..521G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999ARep...43..521G"><span id="translatedtitle">Empirical L-M, R-M, and M-Teff relations for main-sequence stars: Components of close binary <span class="hlt">systems</span> and <span class="hlt">low-mass</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gorda, S. Yu.; Svechnikov, M. A.</p> <p>1999-08-01</p> <p>A new catalog of photometric, geometric, and absolute elements of 112 detached main-sequence eclipsing variables with known photometric and spectroscopic orbital elements has been combined with speckle-interferometry data for <span class="hlt">low-mass</span> stars to yield new mass-luminosity, mass-radius, and mass-spectrum relations: M_bol = 4.46 - 9.52 - (lg M > -0.4), M_bol = 6.18 - 5.91 lg M (lg M <= -0.4); lg R = 0.096 + 0.652 lg M (lg M > 0.14), lg R = 0.10 + 1.03 lg M (lg M <= 0.14); lg M = - 5.60 + 1.504 lg T_eff (lg T_eff > 3.6), and lg M = - 29.4 + 8.2 lg T_eff (lg T_eff <= 3.6). In most cases, the component masses and radii used are accurate to 2-3 and 2-4%, respectively; the errors for <span class="hlt">low-mass</span> stars are larger by factors of 3-4. The coefficients in the relations were derived using linear least squares fitting with corrections for noise in the independent variable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930058960&hterms=tidal+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtidal%2Benergy','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930058960&hterms=tidal+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtidal%2Benergy"><span id="translatedtitle">On the tidal interaction between <span class="hlt">protostellar</span> disks and companions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lin, D. N. C.; Papaloizou, J. C. B.</p> <p>1993-01-01</p> <p>Formation of protoplanets and binary stars in a <span class="hlt">protostellar</span> disk modifies the structure of the disk. Through tidal interactions, energy and angular momentum are transferred between the disk and <span class="hlt">protostellar</span> or protoplanetary companion. We summarize recent progress in theoretical investigations of the disk-companion tidal interaction. We show that <span class="hlt">low-mass</span> protoplanets excite density waves at their Lindblad resonances and that these waves are likely to be dissipated locally. When a protoplanet acquires sufficient mass, its tidal torque induces the formation of a gap in the vicinity of its orbit. Gap formation leads to the termination of protoplanetary growth by accretion. For proto-Jupiter to attain its present mass, we require that (1) the primordial solar nebula is heated by viscous dissipation; (2) the viscous evolution time scale of the nebula is comparable to the age of typical T Tauri stars with circumstellar disks; and (3) the mass distribution in the nebula is comparable to that estimated from a minimum-mass nebula model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.......100T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.......100T"><span id="translatedtitle">Morphologically complex <span class="hlt">protostellar</span> envelopes : structure and kinematics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tobin, John J.</p> <p></p> <p>I present an in-depth study of protostars and their surrounding envelopes of dense gas and dust, using a multitude of observational methods to reveal new details of the star formation process. I use mid-infrared imaging from the Spitzer Space Telescope, combined with photometry spanning the near-infrared to millimeter wavelengths, to construct a model of the L1527 <span class="hlt">protostellar</span> <span class="hlt">system</span>. I modeled both the spectral energy distribution and resolved scattered light images to determine physical properties of the <span class="hlt">protostellar</span> <span class="hlt">system</span>. The nature of the apparent central point source in the Spitzer images was uncertain until high-resolution L-band imaging from the Gemini observatory resolved the point source into a disk in scattered light, having a radius of 200 AU. <span class="hlt">Protostellar</span> envelopes are also often found to cast shadows against the 8 micron Galactic background in Spitzer imaging, enabling direct probes of envelope structure. The shadow images show that the dense envelopes around twenty-two Class 0 protostars are generally morphologically complex from 0.1 pc scales down to ˜1000 AU; they are often filamentary, and frequently non-axisymmetric. The observed envelope structure indicates a likely origin in turbulent cloud structure rather than a quasi-static/equilibrium formation. The complex envelope structure also may indicate an increased likelihood of fragmentation during collapse, forming close binaries. To further characterize these envelopes, I have observed them in the dense molecular gas tracers nthp and nht, both of which closely follow the 8 micron extinction morphology. The magnitude of the velocity gradients and envelope complexity on ˜10000 AU scales indicates that the velocity structure may reflect large-scale infall in addition to the often assumed rotation. Comparisons with three-dimensional filamentary and symmetric rotating collapse models reinforce the interpretation of velocities reflecting large-scale infall, showing that the structure of the envelope</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AAS...21116220V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AAS...21116220V"><span id="translatedtitle">The Warm And Dense Gas In Embedded <span class="hlt">Low-mass</span> Protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Kempen, Tim; van Dishoeck, E. F.; Hogerheijde, M. R.; Joergensen, J. K.; Guesten, R.; Schilke, P.</p> <p>2008-03-01</p> <p>The central regions of embedded <span class="hlt">low-mass</span> protostars is characterized by warm (T K) and dense (10^6 cm-3) gas. Although short (10^5 years), these stages are critical for the subsequent evolution of the <span class="hlt">system</span>. The total mass of the <span class="hlt">system</span> and the initial conditions for (massive) planet formation are determined. Outflows, disks and envelopes all exist on scales of a few hundred to thousand AU, but except for a few cases, the physical structure has mainly been constrained on scales of a few thousand AU through observations of the cold, quiescent gas and dust. We present recent observations of observations using newly commisioned array receivers HARP-B on the JCMT and CHAMP+ on APEX of rotational emission lines of CO, HCO+ and their isotopologues ranging in frequency from 230 to 900 GHz for to probe the warm and dense gas, both close to the star and within the immedeate surroundings of the <span class="hlt">protostellar</span> <span class="hlt">system</span>. Observations were supplemented with continuum data ranging from the near-IR to radio. Special emphasis was put on the results obtained by the c2d program carried out on Spitzer. A large number of sources was observed, ranging from luminous, deeply embedded sources to weak sources where most of the envelope has accreted onto the central star/disk <span class="hlt">system</span>. Initial results show that the amount of warm and dense gas is not necessarily related. Warm gas seems to be more present at more evolved sources, even at low luminosities, while dense gas is more present in the massive envelopes surrounding the deeply embedded Class 0 protostars. It is also shown that the warm (T 100 K) gas is mostly quiescent and not related to outflow activity. It is likely that the gas is thermally heated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003IAUS..221P..60K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003IAUS..221P..60K"><span id="translatedtitle">Star Formation Triggered by <span class="hlt">Low-Mass</span> Clump Collisions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kitsionas, Spyridon; Whitworth, Anthony P.</p> <p></p> <p>We investigate by means of high-resolution numerical simulations the phenomenology of star formation triggered by low-velocity collisions between <span class="hlt">low-mass</span> molecular clumps. The simulations are performed using an SPH code which satisfies the Jeans condition by invoking On-the-Fly Particle Splitting (Kitsionas & Whitworth 2002). The efficiency of star formation appears to increase with increasing clump mass and/or decreasing impact parameter b and/or increasing clump velocity. For b<0.5 the collisions produce shock-compressed layers which fragment into filaments that break up into cores. <span class="hlt">Protostellar</span> objects then condense out of the cores and accrete from them. The resulting accretion rates are comparable to those of Class 0 objects. The densities in the filaments are sufficient that they could be mapped in ammonia or CS line radiation in nearby star formation regions. The phenomenology of star formation observed in our simulations compares rather well with the observed filamentary distribution of young stars in Taurus (Hartmann 2002).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21371914','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21371914"><span id="translatedtitle">DIAGNOSTIC LINE EMISSION FROM EXTREME ULTRAVIOLET AND X-RAY-ILLUMINATED DISKS AND SHOCKS AROUND <span class="hlt">LOW-MASS</span> STARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hollenbach, David; Gorti, U.</p> <p>2009-10-01</p> <p>Extreme ultraviolet (EUV; 13.6 eV <h{nu} {approx}< 100 eV) and X-rays in the 0.1-2 keV band can heat the surfaces of disks around young, <span class="hlt">low-mass</span> stars to thousands of degrees and ionize species with ionization potentials greater than 13.6 eV. Shocks generated by <span class="hlt">protostellar</span> winds can also heat and ionize the same species close to the star/disk <span class="hlt">system</span>. These processes produce diagnostic lines (e.g., [Ne II] 12.8 {mu}m and [O I] 6300 A) that we model as functions of key parameters such as EUV luminosity and spectral shape, X-ray luminosity and spectral shape, and wind mass loss rate and shock speed. Comparing our models with observations, we conclude that either internal shocks in the winds or X-rays incident on the disk surfaces often produce the observed [Ne II] line, although there are cases where EUV may dominate. Shocks created by the oblique interaction of winds with disks are unlikely [Ne II] sources because these shocks are too weak to ionize Ne. Even if [Ne II] is mainly produced by X-rays or internal wind shocks, the neon observations typically place upper limits of {approx}<10{sup 42} s{sup -1} on the EUV photon luminosity of these young <span class="hlt">low-mass</span> stars. The observed [O I] 6300 A line has both a low velocity component (LVC) and a high velocity component. The latter likely arises in internal wind shocks. For the former we find that X-rays likely produce more [O I] luminosity than either the EUV layer, the transition layer between the EUV and X-ray layer, or the shear layer where the <span class="hlt">protostellar</span> wind shocks and entrains disk material in a radial flow across the surface of the disk. Our soft X-ray models produce [O I] LVCs with luminosities up to 10{sup -4} L{sub sun}, but may not be able to explain the most luminous LVCs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011A%26A...527A..19L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011A%26A...527A..19L"><span id="translatedtitle">Water deuterium fractionation in the <span class="hlt">low-mass</span> protostar NGC1333-IRAS2A</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, F.-C.; Parise, B.; Kristensen, L.; Visser, R.; van Dishoeck, E. F.; Güsten, R.</p> <p>2011-03-01</p> <p>Context. Although deuterium enrichment of water may provide an essential piece of information in the understanding of the formation of comets and protoplanetary <span class="hlt">systems</span>, only a few studies up to now have aimed at deriving the HDO/H2O ratio in <span class="hlt">low-mass</span> star forming regions. Previous studies of the molecular deuteration toward the solar-type class 0 protostar, IRAS 16293-2422, have shown that the D/H ratio of water is significantly lower than other grain-surface-formed molecules. It is not clear if this property is general or particular to this source. Aims: In order to see if the results toward IRAS 16293-2422 are particular, we aimed at studying water deuterium fractionation in a second <span class="hlt">low-mass</span> solar-type protostar, NGC1333-IRAS2A. Methods: Using the 1-D radiative transfer code RATRAN, we analyzed five HDO transitions observed with the IRAM 30 m, JCMT, and APEX telescopes. We assumed that the abundance profile of HDO in the envelope is a step function, with two different values in the inner warm (T > 100 K) and outer cold (T < 100 K) regions of the <span class="hlt">protostellar</span> envelope. Results: The inner and outer abundance of HDO is found to be well constrained at the 3σ level. The obtained HDO inner and outer fractional abundances are xHDO_in = 6.6 × 10-8-1.0 × 10-7(3σ) and x^{HDO}out=9×10-11= 9 × 10-11-1.0-1.8 × 10-9(3σ). These values are close to those in IRAS 16293-2422, which suggests that HDO may be formed by the same mechanisms in these two solar-type protostars. Taking into account the (rather poorly onstrained) H2O abundance profile deduced from Herschel observations, the derived HDO/H2O in the inner envelope is ≥1% and in the outer envelope it is 0.9%-18%. These values are more than one order of magnitude higher than what is measured in comets. If the same ratios apply to the protosolar nebula, this would imply that there is some efficient reprocessing of the material between the <span class="hlt">protostellar</span> and cometary phases. Conclusions: The H2O inner fractional</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...797...32P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...797...32P"><span id="translatedtitle">Infall-driven <span class="hlt">Protostellar</span> Accretion and the Solution to the Luminosity Problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Padoan, Paolo; Haugbølle, Troels; Nordlund, Åke</p> <p>2014-12-01</p> <p>We investigate the role of mass infall in the formation and evolution of protostars. To avoid ad hoc initial and boundary conditions, we consider the infall resulting self-consistently from modeling the formation of stellar clusters in turbulent molecular clouds. We show that infall rates in turbulent clouds are comparable to accretion rates inferred from <span class="hlt">protostellar</span> luminosities or measured in pre-main-sequence stars. They should not be neglected in modeling the luminosity of protostars and the evolution of disks, even after the embedded <span class="hlt">protostellar</span> phase. We find large variations of infall rates from protostar to protostar, and large fluctuations during the evolution of individual protostars. In most cases, the infall rate is initially of order 10-5 M ⊙ yr-1, and may either decay rapidly in the formation of <span class="hlt">low-mass</span> stars, or remain relatively large when more massive stars are formed. The simulation reproduces well the observed characteristic values and scatter of <span class="hlt">protostellar</span> luminosities and matches the observed <span class="hlt">protostellar</span> luminosity function. The luminosity problem is therefore solved once realistic <span class="hlt">protostellar</span> infall histories are accounted for, with no need for extreme accretion episodes. These results are based on a simulation of randomly driven magnetohydrodynamic turbulence on a scale of 4 pc, including self-gravity, adaptive-mesh refinement to a resolution of 50 AU, and accreting sink particles. The simulation yields a low star formation rate, consistent with the observations, and a mass distribution of sink particles consistent with the observed stellar initial mass function during the whole duration of the simulation, forming nearly 1300 sink particles over 3.2 Myr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22370082','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22370082"><span id="translatedtitle">Infall-driven <span class="hlt">protostellar</span> accretion and the solution to the luminosity problem</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Padoan, Paolo; Haugbølle, Troels; Nordlund, Åke</p> <p>2014-12-10</p> <p>We investigate the role of mass infall in the formation and evolution of protostars. To avoid ad hoc initial and boundary conditions, we consider the infall resulting self-consistently from modeling the formation of stellar clusters in turbulent molecular clouds. We show that infall rates in turbulent clouds are comparable to accretion rates inferred from <span class="hlt">protostellar</span> luminosities or measured in pre-main-sequence stars. They should not be neglected in modeling the luminosity of protostars and the evolution of disks, even after the embedded <span class="hlt">protostellar</span> phase. We find large variations of infall rates from protostar to protostar, and large fluctuations during the evolution of individual protostars. In most cases, the infall rate is initially of order 10{sup –5} M {sub ☉} yr{sup –1}, and may either decay rapidly in the formation of <span class="hlt">low-mass</span> stars, or remain relatively large when more massive stars are formed. The simulation reproduces well the observed characteristic values and scatter of <span class="hlt">protostellar</span> luminosities and matches the observed <span class="hlt">protostellar</span> luminosity function. The luminosity problem is therefore solved once realistic <span class="hlt">protostellar</span> infall histories are accounted for, with no need for extreme accretion episodes. These results are based on a simulation of randomly driven magnetohydrodynamic turbulence on a scale of 4 pc, including self-gravity, adaptive-mesh refinement to a resolution of 50 AU, and accreting sink particles. The simulation yields a low star formation rate, consistent with the observations, and a mass distribution of sink particles consistent with the observed stellar initial mass function during the whole duration of the simulation, forming nearly 1300 sink particles over 3.2 Myr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21260265','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21260265"><span id="translatedtitle">Fundamental Properties of <span class="hlt">Low-Mass</span> Stars and Brown Dwarfs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu, Michael C.; Dupuy, Trent J.; Stassun, Keivan G.; Allard, France; Blake, Cullen H.; Bonnefoy, M.; Cody, Ann Marie; Kraus, Adam; Day-Jones, A. C.; Lopez-Morales, Mercedes</p> <p>2009-02-16</p> <p>Precise measurements of the fundamental properties of <span class="hlt">low-mass</span> stars and brown dwarfs are key to understanding the physics underlying their formation and evolution. While there has been great progress over the last decade in studying the bulk spectrophotometric properties of <span class="hlt">low-mass</span> objects, direct determination of their masses, radii, and temperatures have been very sparse. Thus, theoretical predictions of <span class="hlt">low-mass</span> evolution and ultracool atmospheres remain to be rigorously tested. The situation is alarming given that such models are widely used, from the determination of the <span class="hlt">low-mass</span> end of the initial mass function to the characterization of exoplanets.An increasing number of mass, radius, and age determinations are placing critical constraints on the physics of <span class="hlt">low-mass</span> objects. A wide variety of approaches are being pursued, including eclipsing binary studies, astrometric-spectroscopic orbital solutions, interferometry, and characterization of benchmark <span class="hlt">systems</span>. In parallel, many more <span class="hlt">systems</span> suitable for concerted study are now being found, thanks to new capabilities spanning both the very widest (all-sky surveys) and very narrowest (diffraction-limited adaptive optics) areas of the sky. This Cool Stars 15 splinter session highlighted the current successes and limitations of this rapidly growing area of precision astrophysics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22365438','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22365438"><span id="translatedtitle">Multilayer formation and evaporation of deuterated ices in prestellar and <span class="hlt">protostellar</span> cores</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Taquet, Vianney; Charnley, Steven B.; Sipilä, Olli</p> <p>2014-08-10</p> <p>Extremely large deuteration of several molecules has been observed toward prestellar cores and <span class="hlt">low-mass</span> protostars for a decade. New observations performed toward <span class="hlt">low-mass</span> protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimensional model of a collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the <span class="hlt">low-mass</span> <span class="hlt">protostellar</span> envelopes with the aim of interpreting the spatial and temporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of ices with a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin states of H{sub 2} and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous and show an increase of their deuterium fractionation toward the surface. The differentiation of the deuteration in ices induces an evolution of the deuteration within <span class="hlt">protostellar</span> envelopes. The warm inner region is poorly deuterated because it includes the whole molecular content of ices, while the deuteration predicted in the cold external envelope scales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuteration within <span class="hlt">protostellar</span> envelopes, but we are still unable to predict the super-high deuteration observed for formaldehyde and methanol. Finally, the extension of this study to the deuteration of complex organics, important for the prebiotic chemistry, shows good agreement with the observations, suggesting that we can use the deuteration to retrace their mechanisms and their moments of formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NewA...36...56T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NewA...36...56T"><span id="translatedtitle">Cyclic period changes and the light-time effect in eclipsing binaries: A <span class="hlt">low-mass</span> companion around the <span class="hlt">system</span> VV Ursae Majoris</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanrıver, Mehmet</p> <p>2015-04-01</p> <p>In this article, a period analysis of the late-type eclipsing binary VV UMa is presented. This work is based on the periodic variation of eclipse timings of the VV UMa binary. We determined the orbital properties and mass of a third orbiting body in the <span class="hlt">system</span> by analyzing the light-travel time effect. The O-C diagram constructed for all available minima times of VV UMa exhibits a cyclic character superimposed on a linear variation. This variation includes three maxima and two minima within approximately 28,240 orbital periods of the <span class="hlt">system</span>, which can be explained as the light-travel time effect (LITE) because of an unseen third body in a triple <span class="hlt">system</span> that causes variations of the eclipse arrival times. New parameter values of the light-time travel effect because of the third body were computed with a period of 23.22 ± 0.17 years in the <span class="hlt">system</span>. The cyclic-variation analysis produces a value of 0.0139 day as the semi-amplitude of the light-travel time effect and 0.35 as the orbital eccentricity of the third body. The mass of the third body that orbits the eclipsing binary stars is 0.787 ± 0.02 M⊙, and the semi-major axis of its orbit is 10.75 AU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011sf2a.conf..423L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011sf2a.conf..423L&link_type=ABSTRACT"><span id="translatedtitle">Molecular emission in chemically active <span class="hlt">protostellar</span> outflows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lefloch, B.</p> <p>2011-12-01</p> <p><span class="hlt">Protostellar</span> outflows play an important role in the dynamical and chemical evolution of cloud through shocks. The Herschel Space Observatory (HSO) brings new insight both on the molecular content and the physical conditions in <span class="hlt">protostellar</span> shocks through high spectral and angular resolution studies of the emission of major gas cooling agents and hydrides. The Herschel/CHESS key-program is carrying out an in depth study of the prototypical shock region L1157-B1. Analysis of the line profiles detected allows to constrain the formation/destruction route of various molecular species, in relation with the predictions of MHD shock models. The Herschel/WISH key-program investigates the properties and origin of water emission in a broad sample of <span class="hlt">protostellar</span> outflows and envelopes. Implications of the first results for future studies on mass-loss phenomena are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013prpl.conf1B090K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013prpl.conf1B090K"><span id="translatedtitle">Dissociative shocks in the inner 100 AU of <span class="hlt">low-mass</span> protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristensen, L. E.</p> <p>2013-07-01</p> <p>Even for <span class="hlt">low-mass</span> protostars (Lbol < 100 Lsun) star formation is a violent process. The inner dense envelope is illuminated by X-rays and UV radiation from the accreting protostar, while the same inner envelope is exposed to the <span class="hlt">protostellar</span> jet and wind, both causing shocks in the dense gas. Thus, the chemical and physical conditions along the outflow cavities are significantly different from the conditions in the bulk of the cold envelope. The hot gas (T > 500 K) remains largely uncharacterized in spite of the fact that it is observed toward nearly every <span class="hlt">low-mass</span> protostar with Herschel-PACS. Recent observations obtained with Herschel-HIFI as part of the "Water in star-forming regions with Herschel" program (WISH) will be presented. The velocity-resolved line profiles of water and related hydrides (OH+, OH, CH+) point to a physical origin of the hot gas to be in dissociative shocks located in the inner few 100 AU of the protostar. Complementary SubMillimeter Array (SMA) data shed further light on both the spatial location and excitation conditions in these shocks. Finally, ALMA Science Verification data show how and where gas is put in motion on small scales (~ 100 AU). All of these observations pave the way for future studies of shocks and entrainment in <span class="hlt">low-mass</span> protostars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013ApJ...776...52C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013ApJ...776...52C&link_type=ABSTRACT"><span id="translatedtitle">Broad N2H+ Emission toward the <span class="hlt">Protostellar</span> Shock L1157-B1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Codella, C.; Viti, S.; Ceccarelli, C.; Lefloch, B.; Benedettini, M.; Busquet, G.; Caselli, P.; Fontani, F.; Gómez-Ruiz, A.; Podio, L.; Vasta, M.</p> <p>2013-10-01</p> <p>We present the first detection of N2H+ toward a <span class="hlt">low-mass</span> <span class="hlt">protostellar</span> outflow, namely, the L1157-B1 shock, at ~0.1 pc from the <span class="hlt">protostellar</span> cocoon. The detection was obtained with the IRAM 30 m antenna. We observed emission at 93 GHz due to the J = 1-0 hyperfine lines. Analysis of this emission coupled with HIFI CHESS multiline CO observations leads to the conclusion that the observed N2H+(1-0) line originated from the dense (>=105 cm-3) gas associated with the large (20''-25'') cavities opened by the <span class="hlt">protostellar</span> wind. We find an N2H+ column density of a few 1012 cm-2 corresponding to an abundance of (2-8) × 10-9. The N2H+ abundance can be matched by a model of quiescent gas evolved for more than 104 yr, i.e., for more than the shock kinematical age (sime2000 yr). Modeling of C-shocks confirms that the abundance of N2H+ is not increased by the passage of the shock. In summary, N2H+ is a fossil record of the pre-shock gas, formed when the density of the gas was around 104 cm-3, and then further compressed and accelerated by the shock.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22039097','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22039097"><span id="translatedtitle">EFFECTS OF ROTATIONALLY INDUCED MIXING IN COMPACT BINARY <span class="hlt">SYSTEMS</span> WITH <span class="hlt">LOW-MASS</span> SECONDARIES AND IN SINGLE SOLAR-TYPE STARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chatzopoulos, E.; Robinson, Edward L.; Wheeler, J. Craig</p> <p>2012-08-20</p> <p>Many population synthesis and stellar evolution studies have addressed the evolution of close binary <span class="hlt">systems</span> in which the primary is a compact remnant and the secondary is filling its Roche lobe, thus triggering mass transfer. Although tidal locking is expected in such <span class="hlt">systems</span>, most studies have neglected the rotationally induced mixing that may occur. Here we study the possible effects of mixing in mass-losing stars for a range of secondary star masses and metallicities. We find that tidal locking can induce rotational mixing prior to contact and thus affect the evolution of the secondary star if the effects of the Spruit-Tayler dynamo are included both for angular momentum and chemical transport. Once contact is made, the effect of mass transfer tends to be more rapid than the evolutionary timescale, so the effects of mixing are no longer directly important, but the mass-transfer strips matter to inner layers that may have been affected by the mixing. These effects are enhanced for secondaries of 1-1.2 M{sub Sun} and for lower metallicities. We discuss the possible implications for the paucity of carbon in the secondaries of the cataclysmic variable SS Cyg and the black hole candidate XTE J1118+480 and for the progenitor evolution of Type Ia supernovae. We also address the issue of the origin of blue straggler stars in globular and open clusters. We find that for models that include rotation consistent with that observed for some blue straggler stars, evolution is chemically homogeneous. This leads to tracks in the H-R diagram that are brighter and bluer than the non-rotating main-sequence turn-off point. Rotational mixing could thus be one of the factors that contribute to the formation of blue stragglers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...732L..30H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...732L..30H"><span id="translatedtitle">Heating and Cooling <span class="hlt">Protostellar</span> Disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirose, S.; Turner, N. J.</p> <p>2011-05-01</p> <p>We examine heating and cooling in <span class="hlt">protostellar</span> disks using three-dimensional radiation-MHD calculations of a patch of the Solar nebula at 1 AU, employing the shearing-box and flux-limited radiation diffusion approximations. The disk atmosphere is ionized by stellar X-rays, well coupled to magnetic fields, and sustains a turbulent accretion flow driven by magnetorotational instability, while the interior is resistive and magnetically dead. The turbulent layers are heated by absorbing the light from the central star and by dissipating the magnetic fields. They are optically thin to their own radiation and cool inefficiently. The optically thick interior in contrast is heated only weakly, by re-emission from the atmosphere. The interior is colder than a classical viscous model and isothermal. The magnetic fields support an extended atmosphere that absorbs the starlight 1.5 times higher than the hydrostatic viscous model. The disk thickness thus measures not the internal temperature, but the magnetic field strength. Fluctuations in the fields move the starlight-absorbing surface up and down. The height ranges between 13% and 24% of the radius over timescales of several orbits, with implications for infrared variability. The fields are buoyant, so the accretion heating occurs higher in the atmosphere than the stresses. The heating is localized around current sheets, caused by magnetorotational instability at lower elevations and by Parker instability at higher elevations. Gas in the sheets is heated above the stellar irradiation temperature, even though accretion is much less than irradiation power when volume averaged. The hot optically thin current sheets might be detectable through their line emission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012cosp...39...29A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012cosp...39...29A&link_type=ABSTRACT"><span id="translatedtitle">From Prestellar to <span class="hlt">Protostellar</span> Cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aikawa, Yuri; Wakelam, Valentine; Hersant, Franck; Garrod, Robin; Herbst, Eric</p> <p>2012-07-01</p> <p>We investigate the molecular evolution and D/H abundance ratios that develop as star formation proceeds from dense cloud cores to <span class="hlt">protostellar</span> cores. We solve a gas-grain reaction network, which is extended to include multi-deuterated species, using a 1-D radiative hydrodynamic model with infalling fluid parcels to derive molecular distribution in assorted evolutionary stages. We find that the abundances of large organic species in the central region increase with time. The duration of the warm-up phase, in which large organic species are efficiently formed, is longer in infalling fluid parcels at later stages. Formation of unsaturated carbon chains in the CH4 sublimation zone (warm carbon chain chemistry) is more effective in later stage. The carbon ion, which reacts with CH4 to form carbon chains, increases in abundance as the envelope density decreases. The large organic molecules and carbon chains are both heavily deuterated, mainly because their mother molecules have high D/H ratios, which are set in the cold phase. The observed CH2DOH/CH3OH ratio towards protostars is reproduced if we assume that the grain-surface exchange and abstraction reactions of CH3OH + D occurs efficiently. In our 1-D collapse model, the fluid parcels directly fall into the protostar, and the warm-up phase in the fluid parcels is rather short. But, in reality, a circumstellar disk is formed, and fluid parcels will stay there for a longer timescale than a free-fall time. We investigate the molecular evolution in such a disk by assuming that a fluid parcel stays at a constant temperature (i.e. a fixed disk radius) after the infall. The species CH3OCH3 and HCOOCH3 become more abundant in the disk than in the envelope. Both have high D/H abundance ratios as well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21319535','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21319535"><span id="translatedtitle">THE FREQUENCY OF <span class="hlt">LOW-MASS</span> EXOPLANETS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>O'Toole, S. J.; Jones, H. R. A.; Tinney, C. G.; Bailey, J.; Wittenmyer, R. A.; Butler, R. P.; Marcy, G. W.; Carter, B.</p> <p>2009-08-20</p> <p>We report first results from the Anglo-Australian Telescope Rocky Planet Search-an intensive, high-precision Doppler planet search targeting <span class="hlt">low-mass</span> exoplanets in contiguous 48 night observing blocks. On this run, we targeted 24 bright, nearby and intrinsically stable Sun-like stars selected from the Anglo-Australian Planet Search's main sample. These observations have already detected one <span class="hlt">low-mass</span> planet reported elsewhere (HD 16417b), and here we reconfirm the detection of HD 4308b. Further, we have Monte Carlo simulated data from this run on a star-by-star basis to produce robust detection constraints. These simulations demonstrate clear differences in the exoplanet detectability functions from star to star due to differences in sampling, data quality and intrinsic stellar stability. They reinforce the importance of star-by-star simulation when interpreting the data from Doppler planet searches. These simulations indicate that for some of our target stars we are sensitive to close-orbiting planets as small as a few Earth masses. The two <span class="hlt">low-mass</span> planets present in our 24-star sample indicate that the exoplanet minimum mass function at <span class="hlt">low</span> <span class="hlt">masses</span> is likely to be a flat {alpha} {approx} -1 (for dN/dM {proportional_to} M {sup {alpha}}) and that between 15% {+-} 10% (at {alpha} = -0.3) and 48% {+-} 34% (at {alpha} = -1.3) of stars host planets with orbital periods of less than 16 days and minimum masses greater than 3 M {sub +}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AAS...20718416J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AAS...20718416J"><span id="translatedtitle">Probing the Inner 200 AU of <span class="hlt">Low-Mass</span> Protostars with the Submillimeter Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jorgensen, J. K.; Bourke, T. L.; Di Francesco, J.; Lee, C.-F.; Myers, P. C.; Ohashi, N.; Schoeier, F. L.; Takakuwa, S.; van Dishoeck, E. F.; Wilner, D. J.; Zhang, Q.</p> <p>2005-12-01</p> <p>We present high angular resolution (1"; 200 AU) observations from a large program studying deeply embedded <span class="hlt">low-mass</span> protostars (class 0 objects) with the Submillimeter Array. In total 9 different sources have been observed in a wide variety of lines of common molecular species together with continuum. The observations are interpreted on basis of detailed dust and line radiative transfer models. The continuum observations resolve the innermost regions of the <span class="hlt">protostellar</span> envelopes and place strong constraints on the presence and properties of their circumstellar disks. The line observations reveal the complex structure of these sources, for example, the chemical and dynamical variations throughout the envelopes and the importance of the outflows on both. The research of JKJ was supported by NASA Origins Grant NAG5-13050. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006A%26A...450..833C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006A%26A...450..833C"><span id="translatedtitle">On the evolution of multiple protoplanets embedded in a <span class="hlt">protostellar</span> disc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cresswell, P.; Nelson, R. P.</p> <p>2006-05-01</p> <p>Context: .Theory predicts that <span class="hlt">low</span> <span class="hlt">mass</span> protoplanets in a laminar <span class="hlt">protostellar</span> disc will migrate into the central star prior to disc dispersal. It is known that protoplanets on orbits with eccentricity e ⪆ H/r, where H is the disc scale height and r is the radius, can halt or reverse their migration. Aims: .We examine whether a <span class="hlt">system</span> of interacting protoplanetary cores can excite and sustain significant eccentricity of the population, allowing some planetary cores to survive in the disc over its lifetime. Methods: .We employ two distinct numerical schemes: an N-body code, adapted to include migration and eccentricity damping due to the gas disc via analytic prescriptions, and a hydrodynamics code that explicitly evolves a 2D protoplanetary disc model with embedded protoplanets. The former allows us to study the long term evolution, the latter to model the <span class="hlt">systems</span> with greater fidelity but for shorter times. Results: .After a brief period of chaotic interaction between the protoplanets that involves scattering, orbital exchange, collisions and the formation of co-orbital planets, we find that the <span class="hlt">system</span> settles into a quiescent state of inward migration. Differential migration causes the protoplanets to form a series of mean motion resonances, such that a planet is often in resonance with both its interior and exterior neighbours. This helps prevent close encounters and leads to the protoplanetary swarm, or subgroups within it, migrating inward at a uniform rate. In about 2 % of runs a single planet is scattered onto a distant orbit with significant eccentricity, allowing it to survive in the disc for ˜ 106 years. Over 20 % of runs produce co-orbital planets that survive for the duration of the simulation, occupying mutual horseshoe or tadpole orbits. Conclusions: .Disc-induced damping overwhelms eccentricity growth through planet-planet interactions, such that a protoplanetary swarm migrates inward. We suggest co-orbital planets may be observed in future</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22016328','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22016328"><span id="translatedtitle">THE ROLE OF TURBULENT MAGNETIC RECONNECTION IN THE FORMATION OF ROTATIONALLY SUPPORTED <span class="hlt">PROTOSTELLAR</span> DISKS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Santos-Lima, R.; De Gouveia Dal Pino, E. M.; Lazarian, A.</p> <p>2012-03-01</p> <p>The formation of <span class="hlt">protostellar</span> disks out of molecular cloud cores is still not fully understood. Under ideal MHD conditions, the removal of angular momentum from the disk progenitor by the typically embedded magnetic field may prevent the formation of a rotationally supported disk during the main <span class="hlt">protostellar</span> accretion phase of <span class="hlt">low-mass</span> stars. This has been known as the magnetic braking problem and the most investigated mechanism to alleviate this problem and help remove the excess of magnetic flux during the star formation process, the so-called ambipolar diffusion (AD), has been shown to be not sufficient to weaken the magnetic braking at least at this stage of the disk formation. In this work, motivated by recent progress in the understanding of magnetic reconnection in turbulent environments, we appeal to the diffusion of magnetic field mediated by magnetic reconnection as an alternative mechanism for removing magnetic flux. We investigate numerically this mechanism during the later phases of the <span class="hlt">protostellar</span> disk formation and show its high efficiency. By means of fully three-dimensional MHD simulations, we show that the diffusivity arising from turbulent magnetic reconnection is able to transport magnetic flux to the outskirts of the disk progenitor at timescales compatible with the collapse, allowing the formation of a rotationally supported disk around the protostar of dimensions {approx}100 AU, with a nearly Keplerian profile in the early accretion phase. Since MHD turbulence is expected to be present in <span class="hlt">protostellar</span> disks, this is a natural mechanism for removing magnetic flux excess and allowing the formation of these disks. This mechanism dismisses the necessity of postulating a hypothetical increase of the ohmic resistivity as discussed in the literature. Together with our earlier work which showed that magnetic flux removal from molecular cloud cores is very efficient, this work calls for reconsidering the relative role of AD in the processes of star</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997IAUS..182P.181S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997IAUS..182P.181S&link_type=ABSTRACT"><span id="translatedtitle">Numerical simulations of <span class="hlt">protostellar</span> jets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suttner, Gerhard; Smith, Michael D.; Yorke, Harold W.; Zinnecker, Hans</p> <p></p> <p>Molecular jets announce the successful birth of a protostar. We develop here a model for the jets and their environments, adapting a multi-dimensional hydrocode to follow the molecular-atomic transitions of hydrogen. We examine powerful outflows into dense gas. The cocoon which forms around a jet is a very low density cavity of atomic gas. These atoms originate from strong shocks which dissociate the molecules. The rest of the molecules are either within the jet or swept up into very thin layers. Pulsed jets produce wider cavities and molecular layers which can grow onto resolvable jet knots. Three-dimensional simulations produce shocked molecular knots, distorted and multiple bow shocks and arclike structures. Spectroscopic and excitation properties of the hydrogen molecules are calculated. In the infrared, strong emission is seen from shocks within the jet (when pulsed) as well as from discrete regions along the cavity walls. Excitation, as measured by line ratios, is not generally constant. Broad double-peaked, shifted emission lines are predicted. The jet model for <span class="hlt">protostellar</span> outflows is confronted with the constraints imposed by CO spectroscopic observations. From the three dimensional simulations we calculate line profiles and construct position-velocity diagrams for the (low-J) CO transitions. We find (1) the profiles imply power law variation of integrated brightness with velocity over a wide range of velocities, (2) the velocity field resembles a `Hubble Law' and (3) a hollow-shell structure at low velocities becomes an elongated lobe at high velocities. Deviations from the simple power law dependence of integrated brightness versus velocity occur at high velocities in our simulations. The curve first dips to a shallow minimum and then rises rapidly and peaks sharply. Reanalysis of the NGC 2264G and Cepheus E data confirm these predictions. We identify these two features with a jet-ambient shear layer and the jet itself. A deeper analysis reveals that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...585A..74Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...585A..74Y"><span id="translatedtitle">Molecule survival in magnetized <span class="hlt">protostellar</span> disk winds. II. Predicted H2O line profiles versus Herschel/HIFI observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yvart, W.; Cabrit, S.; Pineau des Forêts, G.; Ferreira, J.</p> <p>2016-01-01</p> <p>Context. The origin of molecular <span class="hlt">protostellar</span> jets and their role in extracting angular momentum from the accreting <span class="hlt">system</span> are important open questions in star formation research. In the first paper of this series we showed that a dusty magneto-hydrodynamic (MHD) disk wind appeared promising to explain the pattern of H2 temperature and collimation in the youngest jets. Aims: We wish to see whether the high-quality H2O emission profiles of <span class="hlt">low-mass</span> protostars, observed for the first time by the HIFI spectrograph on board the Herschel satellite, remain consistent with the MHD disk wind hypothesis, and which constraints they would set on the underlying disk properties. Methods: We present synthetic H2O line profiles predictions for a typical MHD disk wind solution with various values of disk accretion rate, stellar mass, extension of the launching area, and view angle. We compare them in terms of line shapes and intensities with the HIFI profiles observed by the WISH key program towards a sample of 29 <span class="hlt">low-mass</span> Class 0 and Class 1 protostars. Results: A dusty MHD disk wind launched from 0.2-0.6 AU AU to 3-25 AU can reproduce to a remarkable degree the observed shapes and intensities of the broad H2O component observed in <span class="hlt">low-mass</span> protostars, both in the fundamental 557 GHz line and in more excited lines. Such a model also readily reproduces the observed correlation of 557 GHz line luminosity with envelope density, if the infall rate at 1000 AU is 1-3 times the disk accretion rate in the wind ejection region. It is also compatible with the typical disk size and bolometric luminosity in the observed targets. However, the narrower line profiles in Class 1 sources suggest that MHD disk winds in these sources, if present, would have to be slower and/or less water rich than in Class 0 sources. Conclusions: MHD disk winds appear as a valid (though not unique) option to consider for the origin of the broad H2O component in <span class="hlt">low-mass</span> protostars. ALMA appears ideally suited to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008A%26A...482..677C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008A%26A...482..677C"><span id="translatedtitle">Three-dimensional simulations of multiple protoplanets embedded in a <span class="hlt">protostellar</span> disc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cresswell, P.; Nelson, R. P.</p> <p>2008-05-01</p> <p>Context: Theory predicts that <span class="hlt">low-mass</span> protoplanets in a <span class="hlt">protostellar</span> disc migrate into the central star on a time scale that is short compared with the disc lifetime or the giant planet formation time scale. Protoplanet eccentricities of e⪆ H/r can slow or reverse migration, but previous 2D studies of multiple protoplanets embedded in a protoplanetary disc have shown that gravitational scattering cannot maintain significant planet eccentricities against disc-induced damping. The eventual fate of these <span class="hlt">systems</span> was migration into the central star. Aims: Here we simulate the evolution of <span class="hlt">low-mass</span> protoplanetary swarms in three dimensions. The aim is to examine both protoplanet survival rates and the dynamical structure of the resulting planetary <span class="hlt">systems</span>, and to compare them with 2D simulations. Methods: We present results from a 3D hydrodynamic simulation of eight protoplanets embedded in a protoplanetary disc. We also present a suite of simulations performed using an N-body code, modified to include prescriptions for planetary migration and for eccentricity and inclination damping. These prescriptions were obtained by fitting analytic formulae to hydrodynamic simulations of planets embedded in discs with initially eccentric and/or inclined orbits. Results: As was found in two dimensions, differential migration produces groups of protoplanets in stable, multiple mean-motion resonances that migrate in lockstep, preventing prolonged periods of gravitational scattering. In almost all simulations, this leads to large-scale migration of the protoplanet swarm into the central star in the absence of a viable stopping mechanism. The evolution involves mutual collisions, occasional instances of large-scale scattering, and the frequent formation of the long-lived, co-orbital planet <span class="hlt">systems</span> that arise in >30% of all runs. Conclusions: Disc-induced damping overwhelms eccentricity and inclination growth due to planet-planet interactions, leading to large-scale migration of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900012013','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900012013"><span id="translatedtitle">Discovery of <span class="hlt">low</span> <span class="hlt">mass</span> objects in Taurus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Forrest, W. J.; Ninkov, Z.; Garnett, J. D.; Skrutskie, M. F.; Shure, M.</p> <p>1989-01-01</p> <p>In infrared (2.2 micron, K-band) search of small regions (25 in square) near 26 members of the Taurus star-forming association has revealed 20 dim (K = 13-16 mag) stellar objects near 13 of them. Of these 20 objects, 9 are exceptionally red. It is argued that these 9 are probably also Taurus members. From the luminosities (0.4 to 4 times 10 the -3 power luminosity) and ages (estimated at 10(exp 6) years), masses can be determined by reference to theoretical <span class="hlt">low-mass</span> cooling curves. The masses are in the range 0.005 to 0.015 solar mass, i.e., <span class="hlt">low-mass</span> brown dwarfs. Proper motion studies of 7 of the objects visible on the POSS plates conducted by Burton Jones establish that 4 are highly probable Taurus members while 1 is a possible member.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1014455','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1014455"><span id="translatedtitle">Calorimetry of <span class="hlt">low</span> <span class="hlt">mass</span> Pu239 items</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cremers, Teresa L; Sampson, Thomas E</p> <p>2010-01-01</p> <p>Calorimetric assay has the reputation of providing the highest precision and accuracy of all nondestructive assay measurements. Unfortunately, non-destructive assay practitioners and measurement consumers often extend, inappropriately, the high precision and accuracy of calorimetric assay to very <span class="hlt">low</span> <span class="hlt">mass</span> items. One purpose of this document is to present more realistic expectations for the random uncertainties associated with calorimetric assay for weapons grade plutonium items with masses of 200 grams or less.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011IAUS..280...53J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011IAUS..280...53J"><span id="translatedtitle">Interferometric Studies of <span class="hlt">Low-Mass</span> Protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jørgensen, Jes K.</p> <p>2011-12-01</p> <p>With the advances in high angular resolution (sub)millimeter observations of <span class="hlt">low-mass</span> protostars, windows of opportunities are opening up for very detailed studies of the molecular structure of star forming regions on wide range of spatial scales. Deeply embedded protostars provide an important laboratory to study the chemistry of star formation - providing the link between dense regions in molecular clouds from which stars are formed, i.e., the initial conditions and the end product in terms of, e.g., disk and planet formation. High angular resolution observations at (sub)millimeter wavelengths provide an important tool for studying the chemical composition of such <span class="hlt">low-mass</span> protostars. They for example constrain the spatial molecular abundance variations - and can thereby identify which species are useful tracers of different components of the protostars at different evolutionary stages. In this review I discuss the possibilities and limitations of using high angular resolution (sub)millimeter interferometric observations for studying the chemical evolution of <span class="hlt">low-mass</span> protostars - with a particular keen eye toward near-future ALMA observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9150571','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9150571"><span id="translatedtitle">The origin of <span class="hlt">low</span> <span class="hlt">mass</span> stars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wilking, B A</p> <p>1997-06-01</p> <p>Recent evidence indicates that most <span class="hlt">low</span> <span class="hlt">mass</span> stars in the Galaxy (< 5 M [symbol: see text]) form alongside massive stars in clusters embedded in giant molecular clouds. Once their parental gas is removed, the fate of these clusters is to disperse and blend into the field population of the galactic disk. The distribution of stellar masses in the solar neighborhood, called the Initial Mass Function, is discussed in the context of the origin of <span class="hlt">low</span> <span class="hlt">mass</span> stars. Arguments based on the production rate of field stars are presented that point to giant molecular clouds as the primary birth sites for <span class="hlt">low</span> <span class="hlt">mass</span> stars. The role of observations of molecular clouds at millimeter and infrared wavelengths in confirming this picture is reviewed. Millimeter-wave observations have revealed that molecular clouds consist of low-density gas interspersed with high-density cores. Near-infrared images of these clouds indicate that stars form preferentially in these cores, with the number of young stars roughly scaling with the mass of the core. Molecular-line and near-infrared observations which characterize star formation in the nearest giant molecular cloud complex in Orion are presented. The implications for the Sun forming in a cluster environment are briefly discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...740L..25F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...740L..25F"><span id="translatedtitle">Accurate <span class="hlt">Low-mass</span> Stellar Models of KOI-126</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feiden, Gregory A.; Chaboyer, Brian; Dotter, Aaron</p> <p>2011-10-01</p> <p>The recent discovery of an eclipsing hierarchical triple <span class="hlt">system</span> with two <span class="hlt">low-mass</span> stars in a close orbit (KOI-126) by Carter et al. appeared to reinforce the evidence that theoretical stellar evolution models are not able to reproduce the observational mass-radius relation for <span class="hlt">low-mass</span> stars. We present a set of stellar models for the three stars in the KOI-126 <span class="hlt">system</span> that show excellent agreement with the observed radii. This agreement appears to be due to the equation of state implemented by our code. A significant dispersion in the observed mass-radius relation for fully convective stars is demonstrated; indicative of the influence of physics currently not incorporated in standard stellar evolution models. We also predict apsidal motion constants for the two M dwarf companions. These values should be observationally determined to within 1% by the end of the Kepler mission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...572A...9K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...572A...9K"><span id="translatedtitle">Shockingly low water abundances in Herschel/PACS observations of <span class="hlt">low-mass</span> protostars in Perseus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karska, A.; Kristensen, L. E.; van Dishoeck, E. F.; Drozdovskaya, M. N.; Mottram, J. C.; Herczeg, G. J.; Bruderer, S.; Cabrit, S.; Evans, N. J.; Fedele, D.; Gusdorf, A.; Jørgensen, J. K.; Kaufman, M. J.; Melnick, G. J.; Neufeld, D. A.; Nisini, B.; Santangelo, G.; Tafalla, M.; Wampfler, S. F.</p> <p>2014-12-01</p> <p>Context. Protostars interact with their surroundings through jets and winds impinging on the envelope and creating shocks, but the nature of these shocks is still poorly understood. Aims: Our aim is to survey far-infrared molecular line emission from a uniform and significant sample of deeply-embedded <span class="hlt">low-mass</span> young stellar objects (YSOs) in order to characterize shocks and the possible role of ultraviolet radiation in the immediate <span class="hlt">protostellar</span> environment. Methods: Herschel/PACS spectral maps of 22 objects in the Perseus molecular cloud were obtained as part of the William Herschel Line Legacy (WILL) survey. Line emission from H2O, CO, and OH is tested against shock models from the literature. Results: Observed line ratios are remarkably similar and do not show variations with physical parameters of the sources (luminosity, envelope mass). Most ratios are also comparable to those found at off-source outflow positions. Observations show good agreement with the shock models when line ratios of the same species are compared. Ratios of various H2O lines provide a particularly good diagnostic of pre-shock gas densities, nH ~ 105 cm-3, in agreement with typical densities obtained from observations of the post-shock gas when a compression factor on the order of 10 is applied (for non-dissociative shocks). The corresponding shock velocities, obtained from comparison with CO line ratios, are above 20 km s-1. However, the observations consistently show H2O-to-CO and H2O-to-OH line ratios that are one to two orders of magnitude lower than predicted by the existing shock models. Conclusions: The overestimated model H2O fluxes are most likely caused by an overabundance of H2O in the models since the excitation is well-reproduced. Illumination of the shocked material by ultraviolet photons produced either in the star-disk <span class="hlt">system</span> or, more locally, in the shock, would decrease the H2O abundances and reconcile the models with observations. Detections of hot H2O and strong OH</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhRvL..97x2001G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhRvL..97x2001G"><span id="translatedtitle">Study of Decay Mechanisms in B-→Λc+p¯π- Decays and Observation of <span class="hlt">Low-Mass</span> Structure in the Λc+p¯ <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gabyshev, N.; Abe, K.; Abe, K.; Adachi, I.; Aihara, H.; Asano, Y.; Aulchenko, V.; Aushev, T.; Bakich, A. M.; Bitenc, U.; Bizjak, I.; Blyth, S.; Bondar, A.; Bozek, A.; Bračko, M.; Brodzicka, J.; Browder, T. E.; Chang, P.; Chao, Y.; Chen, A.; Chen, W. T.; Cheon, B. G.; Chistov, R.; Choi, S.-K.; Choi, Y.; Chuvikov, A.; Cole, S.; Dalseno, J.; Danilov, M.; Dash, M.; Drutskoy, A.; Eidelman, S.; Enari, Y.; Fratina, S.; Gershon, T.; Gokhroo, G.; Golob, B.; Gorišek, A.; Hara, T.; Hayashii, H.; Hazumi, M.; Hokuue, T.; Hoshi, Y.; Hou, S.; Hou, W.-S.; Hsiung, Y. B.; Iijima, T.; Imoto, A.; Inami, K.; Ishikawa, A.; Itoh, R.; Iwasaki, M.; Iwasaki, Y.; Kang, J. H.; Kang, J. S.; Kataoka, S. U.; Katayama, N.; Kawai, H.; Kawasaki, T.; Khan, H. R.; Kichimi, H.; Kim, H. J.; Kim, H. O.; Kim, S. K.; Kim, S. M.; Kinoshita, K.; Korpar, S.; Krokovny, P.; Kumar, S.; Kuo, C. C.; Kuzmin, A.; Kwon, Y.-J.; Lange, J. S.; Leder, G.; Lesiak, T.; Lin, S.-W.; Mandl, F.; Matsumoto, T.; Mikami, Y.; Mitaroff, W.; Miyake, H.; Miyata, H.; Mizuk, R.; Nagamine, T.; Nagasaka, Y.; Nakano, E.; Nakao, M.; Nakazawa, H.; Natkaniec, Z.; Nishida, S.; Nitoh, O.; Ogawa, S.; Ohshima, T.; Okabe, T.; Okuno, S.; Olsen, S. L.; Onuki, Y.; Ozaki, H.; Palka, H.; Park, C. W.; Park, H.; Parslow, N.; Peak, L. S.; Pestotnik, R.; Piilonen, L. E.; Rozanska, M.; Sagawa, H.; Sakai, Y.; Sato, N.; Schietinger, T.; Schneider, O.; Schwartz, A. J.; Senyo, K.; Seuster, R.; Sevior, M. E.; Shibuya, H.; Sidorov, V.; Singh, J. B.; Somov, A.; Stamen, R.; Stanič, S.; Starič, M.; Sumiyoshi, T.; Suzuki, S. Y.; Tajima, O.; Takasaki, F.; Tamai, K.; Tamura, N.; Tanaka, M.; Teramoto, Y.; Tian, X. C.; Tsuboyama, T.; Tsukamoto, T.; Uehara, S.; Uglov, T.; Ueno, K.; Uno, S.; Urquijo, P.; Varner, G.; Varvell, K. E.; Villa, S.; Wang, C. H.; Wang, M.-Z.; Xie, Q. L.; Yabsley, B. D.; Yamaguchi, A.; Yamamoto, H.; Yamashita, Y.; Yamauchi, M.; Yang, Heyoung; Zhang, C. C.; Zhang, J.; Zhang, L. M.; Zhang, Z. P.; Zhilich, V.; Žontar, D.</p> <p>2006-12-01</p> <p>Using a sample of 152×106 BB¯ pairs accumulated with the Belle detector at the KEKB e+e- collider, we study the decay mechanism of three-body charmed decay B-→Λc+p¯π-. The intermediate two-body decay B-→Σc(2455)0p¯ is observed for the first time with a branching fraction of (3.7±0.7±0.4±1.0)×10-5 and a statistical significance of 8.4σ. We also observe a <span class="hlt">low-mass</span> enhancement in the (Λc+p¯) <span class="hlt">system</span>, which can be parametrized as a Breit-Wigner function with a mass of (3.35-0.02+0.01±0.02)GeV/c2 and a width of (0.07-0.03+0.04±0.04)GeV/c2. We measure its branching fraction to be (3.9-0.7+0.8±0.4±1.0)×10-5 with a statistical significance of 6.2σ. The errors are statistical, systematic, and that of the Λc+→pK-π+ decay branching fraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/885394','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/885394"><span id="translatedtitle">Current Advances in the Computational Simulation of the Formation of <span class="hlt">Low-Mass</span> Stars</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Klein, R I; Inutsuka, S; Padoan, P; Tomisaka, K</p> <p>2005-10-24</p> <p>Developing a theory of <span class="hlt">low-mass</span> star formation ({approx} 0.1 to 3 M{sub {circle_dot}}) remains one of the most elusive and important goals of theoretical astrophysics. The star-formation process is the outcome of the complex dynamics of interstellar gas involving non-linear interactions of turbulence, gravity, magnetic field and radiation. The evolution of <span class="hlt">protostellar</span> condensations, from the moment they are assembled by turbulent flows to the time they reach stellar densities, spans an enormous range of scales, resulting in a major computational challenge for simulations. Since the previous Protostars and Planets conference, dramatic advances in the development of new numerical algorithmic techniques have been successfully implemented on large scale parallel supercomputers. Among such techniques, Adaptive Mesh Refinement and Smooth Particle Hydrodynamics have provided frameworks to simulate the process of <span class="hlt">low-mass</span> star formation with a very large dynamic range. It is now feasible to explore the turbulent fragmentation of molecular clouds and the gravitational collapse of cores into stars self-consistently within the same calculation. The increased sophistication of these powerful methods comes with substantial caveats associated with the use of the techniques and the interpretation of the numerical results. In this review, we examine what has been accomplished in the field and present a critique of both numerical methods and scientific results. We stress that computational simulations should obey the available observational constraints and demonstrate numerical convergence. Failing this, results of large scale simulations do not advance our understanding of <span class="hlt">low-mass</span> star formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NewA...31....1A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NewA...31....1A"><span id="translatedtitle">First multi-color photometric study and preliminary elements for the <span class="hlt">low-mass</span> ratio, possible progenitors of merging stars, W UMa <span class="hlt">systems</span> TYC 3836-0854-1 and TYC 4157-0683-1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Acerbi, F.; Barani, C.; Martignoni, M.</p> <p>2014-08-01</p> <p>Here we present the first CCD multi-color B, V and Ic light curves of the eclipsing binary stars TYC 3836-0854-1 and TYC 4157-0683-1, the data were obtained in four nights in the year 2010 and three nights in the year 2012 for the first one and in four nights in the year 2010 for the second one. Based on our data the short orbital periods of the <span class="hlt">systems</span> are confirmed and revised to P = 0.4155590 days for TYC 3836-0854-1 and P = 0.3960676 days for TYC 4157-0683-1. Our observations of TYC 3836-0854-1 show symmetric light curves in all passbands with brightness in both maxima at the same level, while the light curve of TYC 4157-0683-1 appear to exhibit the typical O’Connell effect, with Maximum I brighter than Maximum II. By analyzing simultaneously the complete light curves with the 2003 version of the Wilson-Devinney code (2005 revision), photometric solutions were determined. Both the <span class="hlt">systems</span> shows a small difference between the components temperatures of ΔT = 14 K for TYC 3836-0854-1 and ΔT = 149 K for TYC 4157-0683-1. The orbital inclination is i = 78°.6 and i = 79°.7 respectively. The <span class="hlt">systems</span> are found to be a high fill-out, extreme mass ratio overcontact binary with a mass ratio of q = 0.206 and a fill-out factor of f = 59.2% for TYC 3836-0854-1 and q = 0.150 and a fill-out factor of f = 76.3% for TYC 4157-0683-1, suggesting that both the <span class="hlt">systems</span> are in the late stage of overcontact evolution. It is known that deep (f>50%), <span class="hlt">low-mass</span> ratio (q<0.25) overcontact binary stars (DLMR) are a very important resource for understanding the phenomena of Blue Straggler/FK Com-type stars that is an unsolved problem in stellar astrophysics. One of the possible explanations for their formation is from the coalescence of W UMa-type overcontact binary <span class="hlt">systems</span>. The absolute dimensions of both the <span class="hlt">systems</span> are estimated from the logTeff - logL diagram and their dynamical evolution is inferred.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985ASSL..113...61M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985ASSL..113...61M"><span id="translatedtitle"><span class="hlt">Low-mass</span> X-ray binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McClintock, J. E.; Rappaport, S. A.</p> <p></p> <p>A review is given of current understanding of <span class="hlt">low-mass</span> X-ray binaries (LMXBs), which are luminous X-ray sources composed of a late-type optical companion (mass less than about 1 solar mass) and a neutron star (or possibly a black hole). Thirty-two LMXBs have been identified with optical counterparts in the Galaxy and one in the Large Magellanic Cloud (Brad and McClintock, 1983). It is unlikely that there are more than about 100 active LMXBs in the Galaxy, compared with about 200,000 cataclysmic variables. Topics covered in the review are: typical X-ray and optical properties; orbital periods; the nature of the compact source; accretion disks; formation; mass transfer mechanisms; and globular clusters and bright bulge X-ray sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvD..94e5001S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvD..94e5001S"><span id="translatedtitle">Boosting <span class="hlt">low-mass</span> hadronic resonances</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shimmin, Chase; Whiteson, Daniel</p> <p>2016-09-01</p> <p>Searches for new hadronic resonances typically focus on high-mass spectra due to overwhelming QCD backgrounds and detector trigger rates. We present a study of searches for relatively <span class="hlt">low-mass</span> hadronic resonances at the LHC in the case that the resonance is boosted by recoiling against a well-measured high-pT probe such as a muon, photon or jet. The hadronic decay of the resonance is then reconstructed either as a single large-radius jet or as a resolved pair of standard narrow-radius jets, balanced in transverse momentum to the probe. We show that the existing 2015 LHC data set of p p collisions with ∫L d t =4 fb-1 should already have powerful sensitivity to a generic Z' model which couples only to quarks, for Z' masses ranging from 20 - 500 GeV /c2 .</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EAS....71....5L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EAS....71....5L"><span id="translatedtitle">Olivier Chesneau's Work on <span class="hlt">Low</span> <span class="hlt">Mass</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lagadec, E.</p> <p>2015-12-01</p> <p>During his too short career, Olivier Chesneau pioneered the study of the circumstellar environments of <span class="hlt">low</span> <span class="hlt">mass</span> evolved stars using very high angular resolution techniques. He applied state of the art high angular resolution techniques, such as optical interferometry and adaptive optics imaging, to the the study of a variety of objects, from AGB stars to Planetary Nebulae, via e.g. Born Again stars, RCB stars and Novae. I present here an overview of this work and most important results by focusing on the paths he followed and key encounters he made to reach these results. Olivier liked to work in teams and was very strong at linking people with complementary expertises to whom he would communicate his enthusiasm and sharp ideas. His legacy will live on through the many people he inspired.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110013405','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110013405"><span id="translatedtitle">Signatures of Chemical Evolution in <span class="hlt">Protostellar</span> Nebulae</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nuth, Joseph A., III; Johnson, Natasha</p> <p>2011-01-01</p> <p>A decade ago observers began to take serious notice of the presence of crystalline silicate grains in the dust flowing away from some comets. While crystallinity had been seen in such objects previously, starting with the recognitions by Campins and Ryan (1990) that the 10 micron feature of Comet Halley resembled that of the mineral forsterite, most such observations were either ignored or dismissed as no path to explain such crystalline grains was available in the literature. When it was first suggested that an outward flow must be present to carry annealed silicate grains from the innermost regions of the Solar Nebula out to the regions where comets could form (Nuth, 1999; 2001) this suggestion was also dismissed because no such transport mechanism was known at the time. Since then not only have new models of nebular dynamics demonstrated the reality of long distance outward transport (Ciesla, 2007; 2008; 2009) but examination of older models (Boss, 2004) showed that such transport had been present but had gone unrecognized for many years. The most unassailable evidence for outward nebular transport came with the return of the Stardust samples from Comet Wild2, a Kuiper-belt comet that contained micron-scale grains of high temperature minerals resembling the Calcium-Aluminum Inclusions found in primitive meteorites (Zolensky et aI., 2006) that formed at T > 1400K. Now that outward transport in <span class="hlt">protostellar</span> nebulae has been firmly established, a re-examination of its consequences for nebular gas is in order that takes into account both the factors that regulate both the outward flow as well as those that likely control the chemical composition of the gas. Laboratory studies of surface catalyzed reactions suggest that a trend toward more highly reduced carbon and nitrogen compounds in the gas phase should be correlated with a general increase in the crystallinity of the dust (Nuth et aI., 2000), but is such a trend actually observable? Unlike the Fischer-Tropsch or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22039430','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22039430"><span id="translatedtitle">OBSERVING SIMULATED PROTOSTARS WITH OUTFLOWS: HOW ACCURATE ARE <span class="hlt">PROTOSTELLAR</span> PROPERTIES INFERRED FROM SEDs?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Offner, Stella S. R.; Robitaille, Thomas P.; Hansen, Charles E.; Klein, Richard I.; McKee, Christopher F.</p> <p>2012-07-10</p> <p>The properties of unresolved protostars and their local environment are frequently inferred from spectral energy distributions (SEDs) using radiative transfer modeling. In this paper, we use synthetic observations of realistic star formation simulations to evaluate the accuracy of properties inferred from fitting model SEDs to observations. We use ORION, an adaptive mesh refinement (AMR) three-dimensional gravito-radiation-hydrodynamics code, to simulate <span class="hlt">low-mass</span> star formation in a turbulent molecular cloud including the effects of <span class="hlt">protostellar</span> outflows. To obtain the dust temperature distribution and SEDs of the forming protostars, we post-process the simulations using HYPERION, a state-of-the-art Monte Carlo radiative transfer code. We find that the ORION and HYPERION dust temperatures typically agree within a factor of two. We compare synthetic SEDs of embedded protostars for a range of evolutionary times, simulation resolutions, aperture sizes, and viewing angles. We demonstrate that complex, asymmetric gas morphology leads to a variety of classifications for individual objects as a function of viewing angle. We derive best-fit source parameters for each SED through comparison with a pre-computed grid of radiative transfer models. While the SED models correctly identify the evolutionary stage of the synthetic sources as embedded protostars, we show that the disk and stellar parameters can be very discrepant from the simulated values, which is expected since the disk and central source are obscured by the <span class="hlt">protostellar</span> envelope. Parameters such as the stellar accretion rate, stellar mass, and disk mass show better agreement, but can still deviate significantly, and the agreement may in some cases be artificially good due to the limited range of parameters in the set of model SEDs. Lack of correlation between the model and simulation properties in many individual instances cautions against overinterpreting properties inferred from SEDs for unresolved <span class="hlt">protostellar</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22167475','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22167475"><span id="translatedtitle">ANOMALOUS CO{sub 2} ICE TOWARD HOPS-68: A TRACER OF <span class="hlt">PROTOSTELLAR</span> FEEDBACK</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Poteet, Charles A.; Megeath, S. Thomas; Bjorkman, Jon E.; Pontoppidan, Klaus M.; Watson, Dan M.; Sheehan, Patrick D.; Isokoski, Karoliina; Linnartz, Harold</p> <p>2013-04-01</p> <p>We report the detection of a unique CO{sub 2} ice band toward the deeply embedded, <span class="hlt">low-mass</span> protostar HOPS-68. Our spectrum, obtained with the Infrared Spectrograph on board the Spitzer Space Telescope, reveals a 15.2 {mu}m CO{sub 2} ice bending mode profile that cannot be modeled with the same ice structure typically found toward other protostars. We develop a modified CO{sub 2} ice profile decomposition, including the addition of new high-quality laboratory spectra of pure, crystalline CO{sub 2} ice. Using this model, we find that 87%-92% of the CO{sub 2} is sequestered as spherical, CO{sub 2}-rich mantles, while typical interstellar ices show evidence of irregularly shaped, hydrogen-rich mantles. We propose that (1) the nearly complete absence of unprocessed ices along the line of sight is due to the flattened envelope structure of HOPS-68, which lacks cold absorbing material in its outer envelope, and possesses an extreme concentration of material within its inner (10 AU) envelope region and (2) an energetic event led to the evaporation of inner envelope ices, followed by cooling and re-condensation, explaining the sequestration of spherical, CO{sub 2} ice mantles in a hydrogen-poor mixture. The mechanism responsible for the sublimation could be either a transient accretion event or shocks in the interaction region between the <span class="hlt">protostellar</span> outflow and envelope. The proposed scenario is consistent with the rarity of the observed CO{sub 2} ice profile, the formation of nearly pure CO{sub 2} ice, and the production of spherical ice mantles. HOPS-68 may therefore provide a unique window into the <span class="hlt">protostellar</span> feedback process, as outflows and heating shape the physical and chemical structure of <span class="hlt">protostellar</span> envelopes and molecular clouds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...826..208G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...826..208G"><span id="translatedtitle">A <span class="hlt">Protostellar</span> Jet Emanating from a Hypercompact H ii Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guzmán, Andrés E.; Garay, Guido; Rodríguez, Luis F.; Contreras, Yanett; Dougados, Catherine; Cabrit, Sylvie</p> <p>2016-08-01</p> <p>We present radio continuum observations of the high-mass young stellar object (HMYSO) G345.4938+01.4677 obtained using the Australia Telescope Compact Array (ATCA) at 5, 9, 17, and 19 GHz. These observations provide definite evidence that the outer and inner pairs of radio lobes consist of shock-ionized material being excited by an underlying collimated and fast <span class="hlt">protostellar</span> jet emanating from a hypercompact H ii region. By comparing with images taken 6 years earlier at 5 and 9 GHz using the same telescope, we assess the proper motions (PMs) of the radio sources. The outer west and east lobes exhibit PMs of 64 ± 12 and 48 ± 13 mas yr-1, indicating velocities projected in the plane of the sky and receding from G345.4938+01.4677 of 520 and 390 {\\text{km s}}-1, respectively. The internal radio lobes also display PM signals consistently receding from the HMYSO with magnitudes of 17 ± 11 and 35 ± 10 mas yr-1 for the inner west and east lobes, respectively. The morphology of the outer west lobe is that of a detached bow shock. At 17 and 19 GHz, the outer east lobe displays an arcuate morphology also suggesting a bow shock. These results show that disk accretion and jet acceleration—possibly occurring in a very similar way compared with <span class="hlt">low-mass</span> protostars—is taking place in G345.4938+01.4677 despite the presence of ionizing radiation and the associated hypercompact H ii region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApJ...826..208G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApJ...826..208G&link_type=ABSTRACT"><span id="translatedtitle">A <span class="hlt">Protostellar</span> Jet Emanating from a Hypercompact H ii Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guzmán, Andrés E.; Garay, Guido; Rodríguez, Luis F.; Contreras, Yanett; Dougados, Catherine; Cabrit, Sylvie</p> <p>2016-08-01</p> <p>We present radio continuum observations of the high-mass young stellar object (HMYSO) G345.4938+01.4677 obtained using the Australia Telescope Compact Array (ATCA) at 5, 9, 17, and 19 GHz. These observations provide definite evidence that the outer and inner pairs of radio lobes consist of shock-ionized material being excited by an underlying collimated and fast <span class="hlt">protostellar</span> jet emanating from a hypercompact H ii region. By comparing with images taken 6 years earlier at 5 and 9 GHz using the same telescope, we assess the proper motions (PMs) of the radio sources. The outer west and east lobes exhibit PMs of 64 ± 12 and 48 ± 13 mas yr‑1, indicating velocities projected in the plane of the sky and receding from G345.4938+01.4677 of 520 and 390 {\\text{km s}}-1, respectively. The internal radio lobes also display PM signals consistently receding from the HMYSO with magnitudes of 17 ± 11 and 35 ± 10 mas yr‑1 for the inner west and east lobes, respectively. The morphology of the outer west lobe is that of a detached bow shock. At 17 and 19 GHz, the outer east lobe displays an arcuate morphology also suggesting a bow shock. These results show that disk accretion and jet acceleration—possibly occurring in a very similar way compared with <span class="hlt">low-mass</span> protostars—is taking place in G345.4938+01.4677 despite the presence of ionizing radiation and the associated hypercompact H ii region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994AIPC..301.1085L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994AIPC..301.1085L"><span id="translatedtitle">Small <span class="hlt">Low</span> <span class="hlt">Mass</span> Advanced PBR's for Bi-Modal Operation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ludewig, Hans; Todosow, Michael; Powell, James R.</p> <p>1994-07-01</p> <p>A preliminary assessment is made of a <span class="hlt">low</span> <span class="hlt">mass</span> bi-modal reactor for use as a propulsion unit and as a heat source for generating electricity. This reactor is based on the particle bed reactor (PBR) concept. It will be able to generate both thrust and electricity simultaneously. This assessment indicates that the reactor can generate approximately 6.8 (4) N of thrust using hydrogen as a coolant, and 100 KWe using a closed Brayton cycle (CBC) power conversion <span class="hlt">system</span>. Two cooling paths pass through the reactor allowing simultaneous operation of both modes. The development of all the components for this reactor are within the experience base of the NTP project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993snps.sympR...9L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993snps.sympR...9L"><span id="translatedtitle">Small <span class="hlt">low</span> <span class="hlt">mass</span> advanced PBR's for bi-modal operation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ludewig, H.; Todosow, M.; Powell, J. R.</p> <p>1993-10-01</p> <p>A preliminary assessment is made of a <span class="hlt">low</span> <span class="hlt">mass</span> bimodal reactor for use as a propulsion unit and as a heat source for generating electricity. This reactor is based on the particle bed reactor (PBR) concept. It will be able to generate both thrust and electricity simultaneously. This assessment indicates that the reactor can generate approximately 6.8 (4) N of thrust using hydrogen as a coolant and 100 KWe using a closed Brayton cycle (CBC) power conversion <span class="hlt">system</span>. Two cooling paths pass through the reactor allowing a simultaneous operation of both modes. The development of all the components for this reactor are within the experience base of the NTP project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22351469','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22351469"><span id="translatedtitle">Investigations of <span class="hlt">protostellar</span> outflow launching and gas entrainment: Hydrodynamic simulations and molecular emission</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Offner, Stella S. R.; Arce, Héctor G.</p> <p>2014-03-20</p> <p>We investigate <span class="hlt">protostellar</span> outflow evolution, gas entrainment, and star formation efficiency using radiation-hydrodynamic simulations of isolated, turbulent <span class="hlt">low-mass</span> cores. We adopt an X-wind launching model, in which the outflow rate is coupled to the instantaneous <span class="hlt">protostellar</span> accretion rate and evolution. We vary the outflow collimation angle from θ = 0.01-0.1 and find that even well-collimated outflows effectively sweep up and entrain significant core mass. The Stage 0 lifetime ranges from 0.14-0.19 Myr, which is similar to the observed Class 0 lifetime. The star formation efficiency of the cores spans 0.41-0.51. In all cases, the outflows drive strong turbulence in the surrounding material. Although the initial core turbulence is purely solenoidal by construction, the simulations converge to approximate equipartition between solenoidal and compressive motions due to a combination of outflow driving and collapse. When compared to simulation of a cluster of protostars, which is not gravitationally centrally condensed, we find that the outflows drive motions that are mainly solenoidal. The final turbulent velocity dispersion is about twice the initial value of the cores, indicating that an individual outflow is easily able to replenish turbulent motions on sub-parsec scales. We post-process the simulations to produce synthetic molecular line emission maps of {sup 12}CO, {sup 13}CO, and C{sup 18}O and evaluate how well these tracers reproduce the underlying mass and velocity structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22004518','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22004518"><span id="translatedtitle">CORRELATING THE INTERSTELLAR MAGNETIC FIELD WITH <span class="hlt">PROTOSTELLAR</span> JETS AND ITS SOURCES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Targon, C. G.; Rodrigues, C. V.</p> <p>2011-12-10</p> <p>This paper combines new CCD polarimetric data with previous information about <span class="hlt">protostellar</span> objects in a search for correlations involving the interstellar magnetic field (ISMF). Specifically, we carried out an optical polarimetric study of a sample of 28 fields of 10' Multiplication-Sign 10' located in the neighborhood of <span class="hlt">protostellar</span> jets and randomly spread over the Galaxy. The polarimetry of a large number of field stars is used to estimate both the average and dispersion of the ISMF direction in each region. The results of the applied statistical tests are as follows. Concerning the alignment between the jet direction and the ISMF, the whole sample does not show alignment. There is, however, a statistically significant alignment for objects of Classes 0 and I. Regarding the ISMF dispersion, our sample presents values slightly larger for regions containing T Tauri objects than for those harboring younger protostars. Moreover, the ISMF dispersion in regions containing high-mass objects tends to be larger than in those including only <span class="hlt">low-mass</span> protostars. In our sample, the mean interstellar polarization as a function of the average interstellar extinction in a region reaches a maximum value around 3% for A(V) = 5, after which it decreases. Our data also show a clear correlation of the mean value of the interstellar polarization with the dispersion of the ISMF: the larger the dispersion, the smaller the polarization. Based on a comparison of our and previous results, we suggest that the dispersion in regions forming stars is larger than in quiescent regions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ASSP...36..101B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ASSP...36..101B"><span id="translatedtitle">Modelling Magnetised <span class="hlt">Protostellar</span> Jets with SPH</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bate, Matthew R.; Price, Daniel J.; Tricco, Terrence S.</p> <p></p> <p>We present results from the first smoothed particle hydrodynamics (SPH) simulations to produce stable long-lived magnetised <span class="hlt">protostellar</span> jets. We briefly discuss the problems that have arisen in modelling magnetic fields within the SPH formalism in the past, and describe our new method for satisfying the magnetic divergence constraint. We then present results from calculations that follow the collapse of molecular cloud cores to the formation of the first hydrostatic core and follow the magnetised jets launched from the vicinity of the core to distances in excess of 2,000 AU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhDT.........4S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhDT.........4S"><span id="translatedtitle">The rotation of very <span class="hlt">low</span> <span class="hlt">mass</span> objects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scholz, Alexander</p> <p>2004-10-01</p> <p>This dissertation contains an investigation of the rotation of very <span class="hlt">low</span> <span class="hlt">mass</span> objects, i.e. Brown Dwarfs and stars with masses <0.4 MS. Today, it is well-established that there are large populations of such VLM objects in open clusters and in the field, but our knowledge about their physical properties and evolution is still very limited. Contrary to their solar-mass siblings, VLM objects are fully convective throughout their evolution. Thus, they are not able to form a large-scale magnetic field like for example the sun. The magnetic field, in turn, is crucial for the regulation of rotation: Magnetic interaction between star and circumstellar disk ("disk-locking") and angular momentum losses through stellar winds have dominant influence on the rotational evolution. Thus, we can expect major differences in the rotational behaviour of VLM objects and solar-mass stars. The best method to investigate stellar rotation is to measure rotation periods. If a star exhibits surface features which are asymmetrically distributed, its brightness may be modulated with the rotation period. Thus, this dissertation is based on the analysis of photometric time series. Open clusters are an ideal environment for such a project, since they enable one to follow many objects at the same time. Additionally, they allow one to investigate the age and mass dependence of rotation, because distance and age of the clusters are known in good approximation. For this thesis, five open clusters were observed, which span an age range from 3 to 750 Myr. In three of them (SigmaOri, EpsilonOri, IC4665), VLM objects were identified by means of colour magnitude diagrams. The candidate lists for these three regions comprise at least 100 objects, for which photometry in at least three wavelength bands is available. About a fifth to a third of these candidates could be contaminating field stars in the fore- or background of the clusters. For the remaining two clusters (Pleiades and Praesepe), objects from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AJ....129.2806Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AJ....129.2806Z"><span id="translatedtitle">Deep, <span class="hlt">Low</span> <span class="hlt">Mass</span> Ratio Overcontact Binaries. II. IK Persei</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, L.-Y.; Qian, S.-B.; Soonthornthum, B.; Yang, Y.-G.</p> <p>2005-06-01</p> <p>BV photometric light curves of the eclipsing binary IK Per were obtained during three nights in 2002 December. The photometric elements were computed using the Wilson-Devinney code. The results reveal that IK Per is an A-type overcontact binary <span class="hlt">system</span> with a <span class="hlt">low</span> <span class="hlt">mass</span> ratio of q=0.17 and a large degree of overcontact of 60%. The asymmetry of the light curves (i.e., the O'Connell effect) is explained by spot models. The observed long-term orbital period decrease [dP/dt=-(2.5+/-0.09)×10-7 days yr-1] is probably influenced by the presence of a third body in the <span class="hlt">system</span>. The <span class="hlt">low</span> <span class="hlt">mass</span> ratio, high degree of overcontact, and secular orbital decrease all indicate that the situation of IK Per resembles those of FG Hya, GR Vir, and AW UMa. Because of the decrease of their orbital periods, the shrinking of the inner and outer critical Roche lobes will lead the common envelopes to overlap more, and finally the <span class="hlt">systems</span> will evolve into single rapid-rotation stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/950078','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/950078"><span id="translatedtitle"><span class="hlt">Protostellar</span> Outflow Evolution in Turbulent Environments</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cunningham, A; Frank, A; Carroll, J; Blackman, E; Quillen, A</p> <p>2008-04-11</p> <p>The link between turbulence in star formatting environments and <span class="hlt">protostellar</span> jets remains controversial. To explore issues of turbulence and fossil cavities driven by young stellar outflows we present a series of numerical simulations tracking the evolution of transient <span class="hlt">protostellar</span> jets driven into a turbulent medium. Our simulations show both the effect of turbulence on outflow structures and, conversely, the effect of outflows on the ambient turbulence. We demonstrate how turbulence will lead to strong modifications in jet morphology. More importantly, we demonstrate that individual transient outflows have the capacity to re-energize decaying turbulence. Our simulations support a scenario in which the directed energy/momentum associated with cavities is randomized as the cavities are disrupted by dynamical instabilities seeded by the ambient turbulence. Consideration of the energy power spectra of the simulations reveals that the disruption of the cavities powers an energy cascade consistent with Burgers-type turbulence and produces a driving scale-length associated with the cavity propagation length. We conclude that fossil cavities interacting either with a turbulent medium or with other cavities have the capacity to sustain or create turbulent flows in star forming environments. In the last section we contrast our work and its conclusions with previous studies which claim that jets can not be the source of turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999IAUS..190..222Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999IAUS..190..222Z"><span id="translatedtitle">30 Doradus: The <span class="hlt">Low-Mass</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zinnecker, H.; Brandl, B.; Brandner, W.; Moneti, A.; Hunter, D.</p> <p></p> <p>We have obtained HST/NICMOS H-band images of the central 1'x1' field around the R136 starburst cluster in the 30 Doradus HII region, in an attempt to reveal the presence (or absence) of a <span class="hlt">low-mass</span> stellar population (M < 1 Mo). We will discuss the fascinating prospect of 30 Dor/R136 being a proto-globular cluster and a template starburst unit. At the time of writing, we are still working to determine which method and photometry package is best suited to our 0.15" NICMOS images, which are characterised by extreme crowding in the cluster center and a peculiar and slightly undersampled NICMOS PSF. The main difficulty with the PSF is identifying the many "dots" that appear outside the Airy ring as PSF features and not as faint stars. Prelimininary analysis suggests that the H-band luminosity function rises at least until H = 20 (2 Mo). We have detected numerous stars with 20.0 < H < 22.5 (the latter corresponding to 0.4 Mo) beyond about 7" from the cluster centre, but we have not yet determined the completeness in that magnitude range, and we are not yet in a position to make a statement about the shape of the H-band luminosity function there. We have combined our infrared data with the optical WFPC2 images of Hunter et al. (1995) to produce a VIH 3-colour image of the central 30" x 30" area. The result clearly shows unexpected patches of extinction, with one patch only about 5" from the cluster core.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21394314','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21394314"><span id="translatedtitle">HIGH-PRECISION DYNAMICAL MASSES OF VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Konopacky, Q. M.; Ghez, A. M.; McLean, I. S.; Barman, T. S.; Rice, E. L.; Bailey, J. I.; White, R. J.; Duchene, G. E-mail: ghez@astro.ucla.ed E-mail: barman@lowell.ed E-mail: white@chara.gsu.ed</p> <p>2010-03-10</p> <p>We present the results of a three year monitoring program of a sample of very <span class="hlt">low</span> <span class="hlt">mass</span> (VLM) field binaries using both astrometric and spectroscopic data obtained in conjunction with the laser guide star adaptive optics <span class="hlt">system</span> on the W. M. Keck II 10 m telescope. Among the 24 <span class="hlt">systems</span> studied, 15 have undergone sufficient orbital motion, allowing us to derive their relative orbital parameters and hence their total <span class="hlt">system</span> mass. These measurements more than double the number of mass measurements for VLM objects, and include the most precise mass measurement to date (<2%). Among the 11 <span class="hlt">systems</span> with both astrometric and spectroscopic measurements, six have sufficient radial velocity variations to allow us to obtain individual component masses. This is the first derivation of the component masses for five of these <span class="hlt">systems</span>. Altogether, the orbital solutions of these <span class="hlt">low</span> <span class="hlt">mass</span> <span class="hlt">systems</span> show a correlation between eccentricity and orbital period, consistent with their higher mass counterparts. In our primary analysis, we find that there are systematic discrepancies between our dynamical mass measurements and the predictions of theoretical evolutionary models (TUCSON and LYON) with both models either underpredicting or overpredicting the most precisely determined dynamical masses. These discrepancies are a function of spectral type, with late-M through mid-L <span class="hlt">systems</span> tending to have their masses underpredicted, while one T-type <span class="hlt">system</span> has its mass overpredicted. These discrepancies imply that either the temperatures predicted by evolutionary and atmosphere models are inconsistent for an object of a given mass, or the mass-radius relationship or cooling timescales predicted by the evolutionary models are incorrect. If these spectral-type trends are correct and hold into the planetary mass regime, the implication is that the masses of directly imaged extrasolar planets are overpredicted by the evolutionary models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000STIN...0074265V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000STIN...0074265V"><span id="translatedtitle">First Detection of Methanol in a Class O <span class="hlt">Protostellar</span> Disk</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velusamy, T.; Langer, William D.; Goldsmith, Paul F.</p> <p>2000-01-01</p> <p>We report the detection of emission from methanol in a compact source coincident with the position of the L1157 infrared source, which we attribute to molecules in the disk surrounding this young, Class O <span class="hlt">protostellar</span> object. In addition, we identify a spectral feature in the outflow corresponding to an ethanol transition. Using the Caltech Owens Valley Millimeter Array with a synthesized beam size of 2", we detect spatially unresolved methanol in the 2k - 1k transitions at 3mm, which is coincident in position with the peak of the continuum emission. The gas phase methanol could be located in the central region (< 100 AU radius) of a flat disk, or in an extended heated surface layer (approx. 200 AU radius) of a flared disk. The fractional abundance of methanol X(CH3OH) is approx. 2 x l0-8 in the flat disk model, and 3 x l0-7 for the flared disk. The fractional abundance is small in the disk as a whole, but considerably larger in the warm portions. This difference indicates that substantial chemical processing probably takes place in the disk via depletion and desorption. The methanol desorbed from the grains in the warm surface layers returns to the icy grain mantles in the cooler interior of the disk, where it is available to become part of the composition of solar <span class="hlt">system</span>-like bodies, such as comets, formed in the outer circumstellar region. This first millimeter-wavelength detection of a complex organic molecule in a young <span class="hlt">protostellar</span> disk has implications for disk structure and chemical evolution and for potential use as a temperature probe. The research of TV and WL was conducted at the Jet Propulsion Laboratory, California Institute of Technology with support from the National Aeronautics and Space Administration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...823..141D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...823..141D"><span id="translatedtitle">Signatures of Gravitational Instability in Resolved Images of <span class="hlt">Protostellar</span> Disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Ruobing; Vorobyov, Eduard; Pavlyuchenkov, Yaroslav; Chiang, Eugene; Liu, Hauyu Baobab</p> <p>2016-06-01</p> <p><span class="hlt">Protostellar</span> (class 0/I) disks, which have masses comparable to those of their nascent host stars and are fed continuously from their natal infalling envelopes, are prone to gravitational instability (GI). Motivated by advances in near-infrared (NIR) adaptive optics imaging and millimeter-wave interferometry, we explore the observational signatures of GI in disks using hydrodynamical and Monte Carlo radiative transfer simulations to synthesize NIR scattered light images and millimeter dust continuum maps. Spiral arms induced by GI, located at disk radii of hundreds of astronomical units, are local overdensities and have their photospheres displaced to higher altitudes above the disk midplane; therefore, arms scatter more NIR light from their central stars than inter-arm regions, and are detectable at distances up to 1 kpc by Gemini/GPI, VLT/SPHERE, and Subaru/HiCIAO/SCExAO. In contrast, collapsed clumps formed by disk fragmentation have such strong local gravitational fields that their scattering photospheres are at lower altitudes; such fragments appear fainter than their surroundings in NIR scattered light. Spiral arms and streamers recently imaged in four FU Ori <span class="hlt">systems</span> at NIR wavelengths resemble GI-induced structures and support the interpretation that FUors are gravitationally unstable <span class="hlt">protostellar</span> disks. At millimeter wavelengths, both spirals and clumps appear brighter in thermal emission than the ambient disk and can be detected by ALMA at distances up to 0.4 kpc with one hour integration times at ˜0.″1 resolution. Collapsed fragments having masses ≳1 M J can be detected by ALMA within ˜10 minutes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22130651','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22130651"><span id="translatedtitle">MASS-RADIUS RELATIONSHIPS FOR VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> GASEOUS PLANETS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Batygin, Konstantin; Stevenson, David J.</p> <p>2013-05-20</p> <p>Recently, the Kepler spacecraft has detected a sizable aggregate of objects, characterized by giant-planet-like radii and modest levels of stellar irradiation. With the exception of a handful of objects, the physical nature, and specifically the average densities, of these bodies remain unknown. Here, we propose that the detected giant planet radii may partially belong to planets somewhat less massive than Uranus and Neptune. Accordingly, in this work, we seek to identify a physically sound upper limit to planetary radii at <span class="hlt">low</span> <span class="hlt">masses</span> and moderate equilibrium temperatures. As a guiding example, we analyze the interior structure of the Neptune-mass planet Kepler-30d and show that it is acutely deficient in heavy elements, especially compared with its solar <span class="hlt">system</span> counterparts. Subsequently, we perform numerical simulations of planetary thermal evolution and in agreement with previous studies, show that generally, 10-20 M{sub Circled-Plus }, multi-billion year old planets, composed of high density cores and extended H/He envelopes can have radii that firmly reside in the giant planet range. We subject our results to stability criteria based on extreme ultraviolet radiation, as well as Roche-lobe overflow driven mass-loss and construct mass-radius relationships for the considered objects. We conclude by discussing observational avenues that may be used to confirm or repudiate the existence of putative <span class="hlt">low</span> <span class="hlt">mass</span>, gas-dominated planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20090004436&hterms=dead+zones&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddead%2Bzones','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20090004436&hterms=dead+zones&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddead%2Bzones"><span id="translatedtitle">Dead Zone Accretion Flows in <span class="hlt">Protostellar</span> Disks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Turner, Neal; Sano, T.</p> <p>2008-01-01</p> <p>Planets form inside <span class="hlt">protostellar</span> disks in a dead zone where the electrical resistivity of the gas is too high for magnetic forces to drive turbulence. We show that much of the dead zone nevertheless is active and flows toward the star while smooth, large-scale magnetic fields transfer the orbital angular momentum radially outward. Stellar X-ray and radionuclide ionization sustain a weak coupling of the dead zone gas to the magnetic fields, despite the rapid recombination of free charges on dust grains. Net radial magnetic fields are generated in the magnetorotational turbulence in the electrically conducting top and bottom surface layers of the disk, and reach the midplane by ohmic diffusion. A toroidal component to the fields is produced near the midplane by the orbital shear. The process is similar to the magnetization of the solar tachocline. The result is a laminar, magnetically driven accretion flow in the region where the planets form.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ASPC..498..133V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ASPC..498..133V"><span id="translatedtitle"><span class="hlt">Protostellar</span> Collapse Using Multigroup Radiation Hydrodynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vaytet, N.; Chabrier, G.; Audit, E.; Commerçon, B.; Masson, J.; González, M.; Ferguson, J.; Delahaye, F.</p> <p>2015-10-01</p> <p>Many simulations of <span class="hlt">protostellar</span> collapse make use of a grey treatment of radiative transfer coupled to the hydrodynamics. However, interstellar gas and dust opacities present large variations as a function of frequency. In this paper, we present multigroup radiation hydrodynamics simulations of the collapse of a spherically symmetric cloud and the formation of the first and second Larson cores. We have used a non-ideal gas equation of state as well as an extensive set of spectral opacities. Small differences between grey and multigroup simulations were observed. The first and second core accretion shocks were found to be super- and sub-critical, respectively. Varying the initial size and mass of the parent cloud had little impact on the core properties (especially for the second core). We finally present early results from 3D simulations that were performed using the RAMSES code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2253308L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2253308L"><span id="translatedtitle"><span class="hlt">Protostellar</span> chemistry dominated by external irradiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lindberg, Johan E.; Charnley, Steven B.; Jørgensen, Jes K.; Watanabe, Yoshimasa; Bisschop, Suzanne E.; Sakai, Nami; Yamamoto, Satoshi</p> <p>2015-08-01</p> <p>In their youngest stages, protostars are deeply enshrouded in envelopes of gas and dust, material that later accretes onto the central object and the protoplanetary disc. The chemical composition and excitation properties measured towards these envelopes provide valuable information about the current and previous irradiation environment of the forming protostar.We demonstrate the strengths of unbiased single-dish line surveys, which we use to study the chemical and physical properties of <span class="hlt">protostellar</span> envelopes. We have performed line surveys of more than 50 sources in the nearby Corona Australis and Ophiuchus star-forming regions using the APEX telescope. Many of the Corona Australis sources are located near the intermediate-mass Herbig Be star R CrA, and we find that despite its moderate luminosity, the irradiation from this star enhances the H2CO temperatures of the nearby <span class="hlt">protostellar</span> envelopes from 10 K to at least 30-40 K. This drastically elevated temperature should be of crucial importance to the chemistry of these envelopes, due to thermal evaporation of many key species from the dust grain surfaces.Towards R CrA-IRS7B, the most thoroughly investigated object in our study, we find that the chemistry differs greatly from other thoroughly investigated deeply embedded protostars (hot corinos and warm carbon-chain chemistry sources, WCCC). We find low abundances of complex organic molecules such as CH3OCH3 and CH3CN, but instead elevated abundances of CN and some carbon-chain species like HC3N and C2H, although not to the same level as towards typical WCCC sources. We interpret the observed chemical properties as a result of thermal evaporation of CO from the grain mantles and photo-dissociation reactions in the IRS7B envelope, both initiated by the irradiation from R CrA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014mysc.conf...17R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014mysc.conf...17R"><span id="translatedtitle">Tracing Massive <span class="hlt">Protostellar</span> Jets from Intermediate-Mass Protostars in the Carina Nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reiter, A.</p> <p>2014-09-01</p> <p>We present new spectroscopy and imaging of four <span class="hlt">protostellar</span> jets in the Carina nebula. Near-IR [Fe II] emission traces dense gas in the jet that is self-shielded from Lyman continuum photons from nearby O-type stars. New near-IR [Fe II] images reveal a substantial mass of dense, neutral gas that is not seen in the Halpha emission from these jets, leading to densities and mass-loss rate estimates an order of magnitude larger than those derived from the Halpha emission measure. Higher jet mass-loss rates require higher accretion rates, implying that these jets are driven by intermediate-mass (around 2 - 8 solar masses) protostars. Velocities from new proper motion and spectroscopic measurements fall among the velocities typically measured in lower-luminosity sources (100 - 200 km/s). We propose that these jets reflect essentially the same outflow phenomenon seen in <span class="hlt">low-mass</span> protostars, but that the collimated atomic jet core is irradiated and rendered observable. Thus, the jets in Carina constitute a new view of collimated jets from intermediate-mass protostars that exist in a feedback-dominated environment, and offer strong additional evidence that stars up to 8 solar masses form by the same accretion mechanisms as <span class="hlt">low-mass</span> stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.454.2003P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.454.2003P"><span id="translatedtitle">Fast migration of <span class="hlt">low-mass</span> planets in radiative discs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pierens, A.</p> <p>2015-12-01</p> <p><span class="hlt">Low-mass</span> planets are known to undergo Type I migration and this process must have played a key role during the evolution of planetary <span class="hlt">systems</span>. Analytical formulae for the disc torque have been derived assuming that the planet evolves on a fixed circular orbit. However, recent work has shown that in isothermal discs, a migrating protoplanet may also experience dynamical corotation torques that scale with the planet drift rate. The aim of this study is to examine whether dynamical corotation torques can also affect the migration of <span class="hlt">low-mass</span> planets in non-isothermal discs. We performed 2D radiative hydrodynamical simulations to examine the orbital evolution outcome of migrating protoplanets as a function of disc mass. We find that a protoplanet can enter a fast migration regime when it migrates in the direction set by the entropy-related horseshoe drag and when the Toomre stability parameter is less than a threshold value below which the horseshoe region contracts into a tadpole-like region. In that case, an underdense trapped region appears near the planet, with an entropy excess compared to the ambient disc. If the viscosity and thermal diffusivity are small enough so that the entropy excess is conserved during migration, the planet then experiences strong corotation torques arising from the material flowing across the planet orbit. During fast migration, we observe that a protoplanet can pass through the zero-torque line predicted by static torques. We also find that fast migration may help in disrupting the mean-motion resonances that are formed by convergent migration of embryos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100032978','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100032978"><span id="translatedtitle"><span class="hlt">Low</span> <span class="hlt">Mass</span> Printable Devices for Energy Capture, Storage, and Use</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frazier, Donald O.; Singer, Christopher E.; Rogers, Jan R.; Schramm, Harry F.; Fabisinski, Leo L.; Lowenthal, Mark; Ray, William J.; Fuller, Kirk A.</p> <p>2010-01-01</p> <p>The energy-efficient, environmentally friendly technology that will be presented is the result of a Space Act Agreement between NthDegree Technologies Worldwide, Inc., and the National Aeronautics and Space Administration's (NASA's) Marshall Space Flight Center (MSFC). The work combines semiconductor and printing technologies to advance lightweight electronic and photonic devices having excellent potential for commercial and exploration applications. Device development involves three projects that relate to energy generation and consumption: (1) a <span class="hlt">low-mass</span> efficient (low power, low heat emission) micro light-emitting diode (LED) area lighting device; (2) a <span class="hlt">low-mass</span> omni-directional efficient photovoltaic (PV) device with significantly improved energy capture; and (3) a new approach to building super-capacitors. These three technologies, energy capture, storage, and usage (e.g., lighting), represent a systematic approach for building efficient local micro-grids that are commercially feasible; furthermore, these same technologies, appropriately replacing lighting with lightweight power generation, will be useful for enabling inner planetary missions using smaller launch vehicles and to facilitate surface operations during lunar and planetary surface missions. The PV device model is a two sphere, light trapped sheet approximately 2-mm thick. The model suggests a significant improvement over current thin film <span class="hlt">systems</span>. For lighting applications, all three technology components are printable in-line by printing sequential layers on a standard screen or flexographic direct impact press using the three-dimensional printing technique (3DFM) patented by NthDegree. One primary contribution to this work in the near term by the MSFC is to test the robustness of prototype devices in the harsh environments that prevail in space and on the lunar surface. It is anticipated that this composite device, of which the lighting component has passed off-gassing testing, will function</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2255134G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2255134G"><span id="translatedtitle">Star Formation in <span class="hlt">Low-Mass</span> Star-Forming Galaxies at intermediate redshifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Gomez-Guijarro, Carlos</p> <p>2015-08-01</p> <p>Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that <span class="hlt">low-mass</span> <span class="hlt">systems</span> merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf <span class="hlt">systems</span> might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of <span class="hlt">low-mass</span> <span class="hlt">systems</span> at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of <span class="hlt">low-mass</span> dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present Star Formation properties of a sample of <span class="hlt">low-mass</span> Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFRs and overall properties were obtained through the analysis of their spectral energy distributions based on (1) HST and ground-based multi-broadband photometry and (2) deep spectroscopy from VLT and GTC telescopes.The SFRs and stellar masses derived for both samples place our targets on the standard main sequence of star-forming galaxies, but extending the sequence at least one dex to <span class="hlt">low</span> <span class="hlt">mass</span> <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060002654','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060002654"><span id="translatedtitle">IRAS 16293-2422: Evidence for Infall onto a Counter-Rotating <span class="hlt">Protostellar</span> Accretion Disk</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Remijan, Anthony J.; Hollis, J. M.</p> <p>2005-01-01</p> <p>We report high spatial resolution VLA observations of the <span class="hlt">low-mass</span> star-forming region IRAS 16293-2422 using four molecular probes: ethyl cyanide (CH3CH2CN)) methyl formate (CH3OCHO), formic acid (HCOOH), and the ground vibrational state of silicon monoxide (SiO). Ethyl cyanide emission has a spatial scale of approx. 20" and encompasses binary cores A and B as determined by continuum emission peaks. Surrounded by formic acid emission, methyl formate emission has a spatial scale of approx. 6" and is confined to core B. SiO emission shows two velocity components with spatial scales less than 2" that map approx. 2" northeast of the A and B symmetry axis. The redshifted SiO is approx. 2" northwest of blueshifted SiO along a position angle of approx. 135deg which is approximately parallel to the A and B symmetry axis. We interpret the spatial position offset in red and blueshifted SiO emission as due to rotation of a <span class="hlt">protostellar</span> accretion disk and we derive approx. 1.4 Solar Mass, interior to the SiO emission. In the same vicinity, Mundy et al. (1986) also concluded rotation of a nearly edge-on disk from OVRO observations of much stronger and ubiquitous CO-13 emission but the direction of rotation is opposite to the SiO emission findings. Taken together, SiO and CO-13 data suggest evidence for a counter-rotating disk. Moreover, archival BIMA array CO-12C data show an inverse P Cygni profile with the strongest absorption in close proximity to the SiO emission, indicating unambiguous material infall toward the counter-rotating <span class="hlt">protostellar</span> disk at a new source location within the IRAS 16293-2422 complex. The details of these observations and our interpretations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22167721','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22167721"><span id="translatedtitle">VARIABLE ACCRETION OUTBURSTS IN <span class="hlt">PROTOSTELLAR</span> EVOLUTION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan; Gammie, Charles E-mail: lhartm@umich.edu E-mail: gammie@illinois.edu</p> <p>2013-02-20</p> <p>We extend the one-dimensional, two-zone models of long-term <span class="hlt">protostellar</span> disk evolution with infall of Zhu et al. to consider the potential effects of a finite viscosity in regions where the ionization is too low for the magnetorotational instability (MRI) to operate (the {sup d}ead zone{sup )}. We find that the presence of a small but finite dead zone viscosity, as suggested by simulations of stratified disks with MRI-active outer layers, can trigger inside-out bursts of accretion, starting at or near the inner edge of the disk, instead of the previously found outside-in bursts with zero dead zone viscosity, which originate at a few AU in radius. These inside-out bursts of accretion bear a qualitative resemblance to the outburst behavior of one FU Ori object, V1515 Cyg, in contrast to the outside-in burst models, which more closely resemble the accretion events in FU Ori and V1057 Cyg. Our results suggest that the type and frequency of outbursts are potentially a probe of transport efficiency in the dead zone. Simulations must treat the inner disk regions, R {approx}< 0.5 AU, to show the detailed time evolution of accretion outbursts in general and to observe the inside-out bursts in particular.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993snps.sympQ...9P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993snps.sympQ...9P"><span id="translatedtitle">Small <span class="hlt">low</span> <span class="hlt">mass</span> advanced PBR's for propulsion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Powell, J. R.; Todosow, M.; Ludewig, H.</p> <p>1993-10-01</p> <p>The advanced Particle Bed Reactor (PBR) to be described in this paper is characterized by relatively low power, and low cost, while still maintaining competition values for thrust/weight, specific impulse and operating times. In order to retain competitive values for the thrust/weight ratio while reducing the reactor size, it is necessary to change the basic reactor layout, by incorporating new concepts. The new reactor design concept is termed SIRIUS (Small Lightweight Reactor Integral Propulsion <span class="hlt">System</span>). The following modifications are proposed for the reactor design to be discussed in this paper: Pre-heater (U-235 included in Moderator); Hy-C (Hydride/De-hydride for Reactor Control); Afterburner (U-235 impregnated into Hot Frit); and Hy-S (Hydride Spike Inside Hot Frit). Each of the modifications will be briefly discussed below, with benefits, technical issues, design approach, and risk levels addressed. The paper discusses conceptual assumptions, feasibility analysis, mass estimates, and information needs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1020309-direct-search-low-mass-dark-matter-particles-ccds','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1020309-direct-search-low-mass-dark-matter-particles-ccds"><span id="translatedtitle">Direct Search for <span class="hlt">Low</span> <span class="hlt">Mass</span> Dark Matter Particles with CCDs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Barreto, J.; Cease, H.; Diehl, H. T.; Estrada, J.; Flaugher, B.; Harrison, N.; Jones, J.; Kilminster, B.; Molina, J.; Smith, J.; et al</p> <p>2012-05-15</p> <p>A direct dark matter search is performed using fully-depleted high-resistivity CCD detectors. Due to their low electronic readout noise (RMS ~7 eV) these devices operate with a very low detection threshold of 40 eV, making the search for dark matter particles with <span class="hlt">low</span> <span class="hlt">masses</span> (~5 GeV) possible. The results of an engineering run performed in a shallow underground site are presented, demonstrating the potential of this technology in the <span class="hlt">low</span> <span class="hlt">mass</span> region.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21506938','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21506938"><span id="translatedtitle">The origin of <span class="hlt">low-mass</span> white dwarfs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rebassa-Mansergas, A.; Schreiber, M. R.; Gaensicke, B. T.; Girven, J.; Gomez-Moran, A. Nebot</p> <p>2010-11-23</p> <p>We present white dwarf mass distributions of a large sample of post common-envelope binaries and wide white dwarf main sequence binaries and demonstrate that these distributions are statistically independent. While the former contains a much larger fraction of <span class="hlt">low-mass</span> white dwarfs, the latter is similar to single white dwarf mass distributions. Taking into account observational biases we also show that the majority of <span class="hlt">low-mass</span> white dwarfs are formed in close binaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22270736','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22270736"><span id="translatedtitle">BROAD N{sub 2}H{sup +} EMISSION TOWARD THE <span class="hlt">PROTOSTELLAR</span> SHOCK L1157-B1</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Codella, C.; Fontani, F.; Gómez-Ruiz, A.; Vasta, M.; Viti, S.; Ceccarelli, C.; Lefloch, B.; Podio, L.; Caselli, P.</p> <p>2013-10-10</p> <p>We present the first detection of N{sub 2}H{sup +} toward a <span class="hlt">low-mass</span> <span class="hlt">protostellar</span> outflow, namely, the L1157-B1 shock, at ∼0.1 pc from the <span class="hlt">protostellar</span> cocoon. The detection was obtained with the IRAM 30 m antenna. We observed emission at 93 GHz due to the J = 1-0 hyperfine lines. Analysis of this emission coupled with HIFI CHESS multiline CO observations leads to the conclusion that the observed N{sub 2}H{sup +}(1-0) line originated from the dense (≥10{sup 5} cm{sup –3}) gas associated with the large (20''-25'') cavities opened by the <span class="hlt">protostellar</span> wind. We find an N{sub 2}H{sup +} column density of a few 10{sup 12} cm{sup –2} corresponding to an abundance of (2-8) × 10{sup –9}. The N{sub 2}H{sup +} abundance can be matched by a model of quiescent gas evolved for more than 10{sup 4} yr, i.e., for more than the shock kinematical age (≅2000 yr). Modeling of C-shocks confirms that the abundance of N{sub 2}H{sup +} is not increased by the passage of the shock. In summary, N{sub 2}H{sup +} is a fossil record of the pre-shock gas, formed when the density of the gas was around 10{sup 4} cm{sup –3}, and then further compressed and accelerated by the shock.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015A%26A...574A.107K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015A%26A...574A.107K&link_type=ABSTRACT"><span id="translatedtitle">Depletion of chlorine into HCl ice in a <span class="hlt">protostellar</span> core. The CHESS spectral survey of OMC-2 FIR 4</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kama, M.; Caux, E.; López-Sepulcre, A.; Wakelam, V.; Dominik, C.; Ceccarelli, C.; Lanza, M.; Lique, F.; Ochsendorf, B. B.; Lis, D. C.; Caballero, R. N.; Tielens, A. G. G. M.</p> <p>2015-02-01</p> <p>Context. The freezeout of gas-phase species onto cold dust grains can drastically alter the chemistry and the heating-cooling balance of <span class="hlt">protostellar</span> material. In contrast to well-known species such as carbon monoxide (CO), the freezeout of various carriers of elements with abundances <10-5 has not yet been well studied. Aims: Our aim here is to study the depletion of chlorine in the <span class="hlt">protostellar</span> core, OMC-2 FIR 4. Methods: We observed transitions of HCl and H2Cl+ towards OMC-2 FIR 4 using the Herschel Space Observatory and Caltech Submillimeter Observatory facilities. Our analysis makes use of state of the art chlorine gas-grain chemical models and newly calculated HCl-H2 hyperfine collisional excitation rate coefficients. Results: A narrow emission component in the HCl lines traces the extended envelope, and a broad one traces a more compact central region. The gas-phase HCl abundance in FIR 4 is 9 × 10-11, a factor of only 10-3 that of volatile elemental chlorine. The H2Cl+ lines are detected in absorption and trace a tenuous foreground cloud, where we find no depletion of volatile chlorine. Conclusions: Gas-phase HCl is the tip of the chlorine iceberg in <span class="hlt">protostellar</span> cores. Using a gas-grain chemical model, we show that the hydrogenation of atomic chlorine on grain surfaces in the dark cloud stage sequesters at least 90% of the volatile chlorine into HCl ice, where it remains in the <span class="hlt">protostellar</span> stage. About 10% of chlorine is in gaseous atomic form. Gas-phase HCl is a minor, but diagnostically key reservoir, with an abundance of ≲10-10 in most of the <span class="hlt">protostellar</span> core. We find the [35Cl]/[37Cl] ratio in OMC-2 FIR 4 to be 3.2 ± 0.1, consistent with the solar <span class="hlt">system</span> value. Appendices are available in electronic form at http://www.aanda.org</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013A%26A...556A..89Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013A%26A...556A..89Y"><span id="translatedtitle">High-J CO survey of <span class="hlt">low-mass</span> protostars observed with Herschel-HIFI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yıldız, U. A.; Kristensen, L. E.; van Dishoeck, E. F.; San José-García, I.; Karska, A.; Harsono, D.; Tafalla, M.; Fuente, A.; Visser, R.; Jørgensen, J. K.; Hogerheijde, M. R.</p> <p>2013-08-01</p> <p>Context. In the deeply embedded stage of star formation, protostars start to heat and disperse their surrounding cloud cores. The evolution of these sources has traditionally been traced through dust continuum spectral energy distributions (SEDs), but the use of CO excitation as an evolutionary probe has not yet been explored due to the lack of high-J CO observations. Aims: The aim is to constrain the physical characteristics (excitation, kinematics, column density) of the warm gas in <span class="hlt">low-mass</span> <span class="hlt">protostellar</span> envelopes using spectrally resolved Herschel data of CO and compare those with the colder gas traced by lower excitation lines. Methods: Herschel-HIFI observations of high-J lines of 12CO, 13CO, and C18O (up to Ju = 10, Eu up to 300 K) are presented toward 26 deeply embedded <span class="hlt">low-mass</span> Class 0 and Class I young stellar objects, obtained as part of the Water In Star-forming regions with Herschel (WISH) key program. This is the first large spectrally resolved high-J CO survey conducted for these types of sources. Complementary lower J CO maps were observed using ground-based telescopes, such as the JCMT and APEX and convolved to matching beam sizes. Results: The 12CO 10-9 line is detected for all objects and can generally be decomposed into a narrow and a broad component owing to the quiescent envelope and entrained outflow material, respectively. The 12CO excitation temperature increases with velocity from ~60 K up to ~130 K. The median excitation temperatures for 12CO, 13CO, and C18O derived from single-temperature fits to the Ju = 2-10 integrated intensities are ~70 K, 48 K and 37 K, respectively, with no significant difference between Class 0 and Class I sources and no trend with Menv or Lbol. Thus, in contrast to the continuum SEDs, the spectral line energy distributions (SLEDs) do not show any evolution during the embedded stage. In contrast, the integrated line intensities of all CO isotopologs show a clear decrease with evolutionary stage as the envelope is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApJ...819...96G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApJ...819...96G&link_type=ABSTRACT"><span id="translatedtitle">Magnetic Fields in Early <span class="hlt">Protostellar</span> Disk Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>González-Casanova, Diego F.; Lazarian, Alexander; Santos-Lima, Reinaldo</p> <p>2016-03-01</p> <p>We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables <span class="hlt">protostellar</span> disk formation resolving the so-called “magnetic braking catastrophe.” In particular, we provide a detailed study of the dynamics of a 0.5 M⊙ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, “reconnection diffusion,” removes the magnetic flux from the disk; the other involves the change of the magnetic field's topology, but does not change the absolute value of the magnetic flux through the disk. We demonstrate that for the first mechanism, turbulence causes a magnetic flux transport outward from the inner disk to the ambient medium, thus decreasing the coupling of the disk to the ambient material. A similar effect is achieved through the change of the magnetic field's topology from a split monopole configuration to a dipole configuration. We explore how both mechanisms prevent the catastrophic loss of disk angular momentum and compare both above turbulent reconnection mechanisms with alternative mechanisms from the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006sfgb.conf...86Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006sfgb.conf...86Z"><span id="translatedtitle">The one dimensional collapse models of turbulent <span class="hlt">protostellar</span> clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zamozdra, S. N.</p> <p></p> <p>The spherically-symmetric numerical modelling of the gravitational collapse of <span class="hlt">protostellar</span> clouds is carried out, taking ambipolar diffusion and the pressure of Alfvenic turbulence into account. It is shown that the dependency of protostar formation time on ekg (the initial turbulent-to-gravitational energies ratio) is non-monotonic because it is determined by the complex interaction of large scale magnetosonic waves with the waves of turbulence amplification. <span class="hlt">Protostellar</span> mass is almost independent on ekg while accretion rate variations with ekg can be of order of 10%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...811..103M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...811..103M"><span id="translatedtitle">Discovery of a <span class="hlt">Low-mass</span> Companion Around HR 3549</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mawet, D.; David, T.; Bottom, M.; Hinkley, S.; Stapelfeldt, K.; Padgett, D.; Mennesson, B.; Serabyn, E.; Morales, F.; Kuhn, J.</p> <p>2015-10-01</p> <p>We report the discovery of a <span class="hlt">low-mass</span> companion to HR 3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 μm (10σ significance). We imaged HR 3549 B in the L band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in 2015 January. The companion is at a projected separation of ≃80 AU and position angle of ≃157°, so it is orbiting well beyond the warm disk inner edge of r > 10 AU. Our age estimate for this <span class="hlt">system</span> corresponds to a companion mass in the range 15–80 MJ, spanning the brown dwarf regime, and so HR 3549 B is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios. The simultaneous presence of a warm disk and a brown dwarf around HR 3549 provides interesting empirical constraints on models of the formation of substellar companions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22525339','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22525339"><span id="translatedtitle">DISCOVERY OF A <span class="hlt">LOW-MASS</span> COMPANION AROUND HR 3549</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mawet, D.; David, T.; Bottom, M.; Hinkley, S.; Stapelfeldt, K.; Padgett, D.; Mennesson, B.; Serabyn, E.; Morales, F.; Kuhn, J.</p> <p>2015-10-01</p> <p>We report the discovery of a <span class="hlt">low-mass</span> companion to HR 3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 μm (10σ significance). We imaged HR 3549 B in the L band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in 2015 January. The companion is at a projected separation of ≃80 AU and position angle of ≃157°, so it is orbiting well beyond the warm disk inner edge of r > 10 AU. Our age estimate for this <span class="hlt">system</span> corresponds to a companion mass in the range 15–80 M{sub J}, spanning the brown dwarf regime, and so HR 3549 B is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios. The simultaneous presence of a warm disk and a brown dwarf around HR 3549 provides interesting empirical constraints on models of the formation of substellar companions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22520226','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22520226"><span id="translatedtitle">INFRARED AND RADIO OBSERVATIONS OF A SMALL GROUP OF <span class="hlt">PROTOSTELLAR</span> OBJECTS IN THE MOLECULAR CORE, L1251-C</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kim, Jungha; Lee, Jeong-Eun; Choi, Minho; Kang, Miju; Bourke, Tyler L.; II, Neal J. Evans; Francesco, James Di; Cieza, Lucas A.; Dunham, Michael M.</p> <p>2015-05-15</p> <p>We present a multi-wavelength observational study of a <span class="hlt">low-mass</span> star-forming region, L1251-C, with observational results at wavelengths from the near-infrared to the millimeter. Spitzer Space Telescope observations confirmed that IRAS 22343+7501 is a small group of <span class="hlt">protostellar</span> objects. The extended emission in the east–west direction with its intensity peak at the center of L1251A has been detected at 350 and 850 μm with the Caltech Submillimeter Observatory and James Clerk Maxwell telescopes, tracing dense envelope material around L1251A. The single-dish data from the Korean VLBI Network and TRAO telescopes show inconsistencies between the intensity peaks of several molecular emission lines and that of the continuum emission, suggesting complex distributions of molecular abundances around L1251A. The Submillimeter Array interferometer data, however, show intensity peaks of CO 2–1 and {sup 13}CO 2–1 located at the position of IRS 1, which is both the brightest source in the Infrared Array Camera image and the weakest source in the 1.3 mm dust-continuum map. IRS 1 is the strongest candidate for the driving source of the newly detected compact CO 2–1 outflow. Over the entire region (14′ × 14′) of L125l-C, 3 Class I and 16 Class II sources have been detected, including three young stellar objects (YSOs) in L1251A. A comparison between the average projected distance among the 19 YSOs in L1251-C and that among the 3 YSOs in L1251A suggests that L1251-C is an example of <span class="hlt">low-mass</span> cluster formation where <span class="hlt">protostellar</span> objects form in a small group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJS..218....5K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJS..218....5K"><span id="translatedtitle">Infrared and Radio Observations of a Small Group of <span class="hlt">Protostellar</span> Objects in the Molecular Core, L1251-C</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Jungha; Lee, Jeong-Eun; Choi, Minho; Bourke, Tyler L.; Evans, Neal J., II; Di Francesco, James; Cieza, Lucas A.; Dunham, Michael M.; Kang, Miju</p> <p>2015-05-01</p> <p>We present a multi-wavelength observational study of a <span class="hlt">low-mass</span> star-forming region, L1251-C, with observational results at wavelengths from the near-infrared to the millimeter. Spitzer Space Telescope observations confirmed that IRAS 22343+7501 is a small group of <span class="hlt">protostellar</span> objects. The extended emission in the east-west direction with its intensity peak at the center of L1251A has been detected at 350 and 850 μm with the Caltech Submillimeter Observatory and James Clerk Maxwell telescopes, tracing dense envelope material around L1251A. The single-dish data from the Korean VLBI Network and TRAO telescopes show inconsistencies between the intensity peaks of several molecular emission lines and that of the continuum emission, suggesting complex distributions of molecular abundances around L1251A. The Submillimeter Array interferometer data, however, show intensity peaks of CO 2-1 and 13CO 2-1 located at the position of IRS 1, which is both the brightest source in the Infrared Array Camera image and the weakest source in the 1.3 mm dust-continuum map. IRS 1 is the strongest candidate for the driving source of the newly detected compact CO 2-1 outflow. Over the entire region (14‧ × 14‧) of L125l-C, 3 Class I and 16 Class II sources have been detected, including three young stellar objects (YSOs) in L1251A. A comparison between the average projected distance among the 19 YSOs in L1251-C and that among the 3 YSOs in L1251A suggests that L1251-C is an example of <span class="hlt">low-mass</span> cluster formation where <span class="hlt">protostellar</span> objects form in a small group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22034561','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22034561"><span id="translatedtitle">ROTATIONAL VELOCITIES OF INDIVIDUAL COMPONENTS IN VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Konopacky, Q. M.; Macintosh, B. A.; Ghez, A. M.; Fabrycky, D. C.; White, R. J.; Barman, T. S.; Rice, E. L.; Hallinan, G.; Duchene, G. E-mail: konopacky@di.utoronto.ca E-mail: fabrycky@ucolick.org E-mail: barman@lowell.edu E-mail: gh@astro.caltech.edu</p> <p>2012-05-01</p> <p>We present rotational velocities for individual components of 11 very <span class="hlt">low</span> <span class="hlt">mass</span> (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics <span class="hlt">system</span>. We find that the observed sources tend to be rapid rotators (v sin i > 10 km s{sup -1}), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest v sin i, LP 349-25B and HD 130948C, are rotating at {approx}30% of their break-up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary <span class="hlt">systems</span>, all with orbital semimajor axes {approx}<3.5 AU, have component v sin i values that differ by greater than 3{sigma}. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have implications for binary star formation and evolution. We also investigate possible dynamical evolution in the triple <span class="hlt">system</span> HD 130948A-BC. The close binary brown dwarfs B and C have significantly different v sin i values. We demonstrate that components B and C could have been torqued into misalignment by the primary star, A, via orbital precession. Such a scenario can also be applied to another triple <span class="hlt">system</span> in our sample, GJ 569A-Bab. Interactions such as these may play an important role in the dynamical evolution of VLM binaries. Finally, we note that two of the binaries with large differences in component v sin i, LP 349-25AB and 2MASS 0746+20AB, are also known radio sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AJ....139.2566D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AJ....139.2566D"><span id="translatedtitle">Sloan <span class="hlt">Low-mass</span> Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES): A Catalog of Very Wide, <span class="hlt">Low-mass</span> Pairs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dhital, Saurav; West, Andrew A.; Stassun, Keivan G.; Bochanski, John J.</p> <p>2010-06-01</p> <p>We present the Sloan <span class="hlt">Low-mass</span> Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES), a catalog of 1342 very-wide (projected separation gsim500 AU), <span class="hlt">low-mass</span> (at least one mid-K to mid-M dwarf component) common proper motion pairs identified from astrometry, photometry, and proper motions in the Sloan Digital Sky Survey. A Monte Carlo-based Galactic model is constructed to assess the probability of chance alignment for each pair; only pairs with a probability of chance alignment <=0.05 are included in the catalog. The overall fidelity of the catalog is expected to be 98.35%. The selection algorithm is purposely exclusive to ensure that the resulting catalog is efficient for follow-up studies of <span class="hlt">low-mass</span> pairs. The SLoWPoKES catalog is the largest sample of wide, <span class="hlt">low-mass</span> pairs to date and is intended as an ongoing community resource for detailed study of bona fide <span class="hlt">systems</span>. Here, we summarize the general characteristics of the SLoWPoKES sample and present preliminary results describing the properties of wide, <span class="hlt">low-mass</span> pairs. While the majority of the identified pairs are disk dwarfs, there are 70 halo subdwarf (SD) pairs and 21 white dwarf-disk dwarf pairs, as well as four triples. Most SLoWPoKES pairs violate the previously defined empirical limits for maximum angular separation or binding energies. However, they are well within the theoretical limits and should prove very useful in putting firm constraints on the maximum size of binary <span class="hlt">systems</span> and on different formation scenarios. We find a lower limit to the wide binary frequency (WBF) for the mid-K to mid-M spectral types that constitute our sample to be 1.1%. This frequency decreases as a function of Galactic height, indicating a time evolution of the WBF. In addition, the semi-major axes of the SLoWPoKES <span class="hlt">systems</span> exhibit a distinctly bimodal distribution, with a break at separations around 0.1 pc that is also manifested in the <span class="hlt">system</span> binding energy. Compared with theoretical predictions for the disruption of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990034131&hterms=extinction+consequences&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dextinction%2Bconsequences','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990034131&hterms=extinction+consequences&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dextinction%2Bconsequences"><span id="translatedtitle">X-Ray Emission from <span class="hlt">Protostellar</span> Jets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Morse, Jon A.; McCray, Dick; Bally, John; Devine, David</p> <p>1998-01-01</p> <p>The goals of this program were to identify the termination shocks in several parsec-scale <span class="hlt">protostellar</span> jets through the thermal soft X-rays emitted by the high-velocity terminal shock waves, and to assess the impact these outflows have on the surrounding interstellar and intercloud medium. The terminal shock waves that plow into the undisturbed interstellar medium may have shock velocities commensurate with the observed space motions of several hundred km s(exp -1). Such shocks will heat and ionize the interstellar medium, perhaps creating large ovoid bubbles of hot gas. Identifying the location of the terminal shocks in these outflows would also allow us to place constraints on the ages of these outflows, and hence the duration of the mass-loss phase that accompanies the formation of a star. We targeted four outflows where the outer optical shock waves are projected against low-extinction backgrounds. From the two dozen or so parsec-scale flows known, we chose those that have the highest velocities, brightest optical counterparts, and/or the richest concentration of shock waves in a small area on the sky. Four giant HH flows have been observed with the ROSAT HRI at Priority A for 30 ksec each. Results: Unfortunately, we failed to detect X-ray emission from the terminal bow shocks of the giant HH flows using the ROSAT HRI. The reasons are likely to be: (1) The shock velocities may be too low to emit in the soft X-rays. (2) The sensitivity of the HRI is too low to detect the diffuse emission. The fields that we observed were chosen to be low extinction sight-lines, with the consequence that the tenuous media into which the outer bow shocks are propagating produce low fluxes. Despite the failure to achieve the primary science goals, we have identified in each image a half a dozen or so point-source young stellar objects. The HRI images have been very useful for discerning potential outflow sources and are being combined with optical, near-IR, and radio imaging data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000ApJ...540L..95P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000ApJ...540L..95P"><span id="translatedtitle"><span class="hlt">Protostellar</span> Disk Instabilities and the Formation of Substellar Companions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pickett, Brian K.; Durisen, Richard H.; Cassen, Patrick; Mejia, Annie C.</p> <p>2000-09-01</p> <p>Recent numerical simulations of self-gravitating <span class="hlt">protostellar</span> disks have suggested that gravitational instabilities can lead to the production of substellar companions. In these simulations, the disk is typically assumed to be locally isothermal; i.e., the initial, axisymmetric temperature in the disk remains everywhere unchanged. Such an idealized condition implies extremely efficient cooling for outwardly moving parcels of gas. While we have seen disk disruption in our own locally isothermal simulations of a small, massive <span class="hlt">protostellar</span> disk, no long-lived companions formed as a result of the instabilities. Instead, thermal and tidal effects and the complex interactions of the disk material prevented permanent condensations from forming, despite the vigorous growth of spiral instabilities. In order to compare our results more directly with those of other authors, we here present three-dimensional evolutions of an older, larger, but less massive <span class="hlt">protostellar</span> disk. We show that potentially long-lived condensations form only for the extreme of local isothermality, and then only when severe restrictions are placed on the natural tendency of the <span class="hlt">protostellar</span> disk to expand in response to gravitational instabilities. A more realistic adiabatic evolution leads to vertical and radial expansion of the disk but no clump formation. We conclude that isothermal disk calculations cannot demonstrate companion formation by disk fragmentation but only suggest it at best. It will be necessary in future numerical work on this problem to treat the disk thermodynamics more realistically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22365252','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22365252"><span id="translatedtitle">A CHEMICAL VIEW OF <span class="hlt">PROTOSTELLAR</span>-DISK FORMATION IN L1527</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sakai, Nami; Oya, Yoko; Watanabe, Yoshimasa; Yamamoto, Satoshi; Sakai, Takeshi; Hirota, Tomoya; Ceccarelli, Cecilia; Kahane, Claudine; Lopez-Sepulcre, Ana; Lefloch, Bertrand; Vastel, Charlotte; Bottinelli, Sandrine; Caux, Emmanuel; Coutens, Audrey; Aikawa, Yuri; Takakuwa, Shigehisa; Yen, Hsi-Wei; Ohashi, Nagayoshi</p> <p>2014-08-20</p> <p>Subarcsecond images of the rotational line emissions of CCH, CS, H{sub 2}CO, and CH{sub 3}OH have been obtained toward the <span class="hlt">low-mass</span> protostar IRAS 04368+2557 in L1527 as one of the early science projects of the Atacama Large Millimeter/submillimeter Array. The intensity distributions of CCH and CS show a double-peaked structure along the edge-on envelope with a dip toward the protostar position, whereas those of H{sub 2}CO and CH{sub 3}OH are centrally peaked. By analyzing the position-velocity diagrams along the envelope, CCH and CS are found to reside mainly in the envelope, where the gas is infalling with conservation of its angular momentum. They are almost absent inward of the centrifugal barrier (a half of the centrifugal radius). Although H{sub 2}CO exists in the infalling rotating envelope, it also resides in the disk component inside the centrifugal barrier to some extent. On the other hand, CH{sub 3}OH seems to exist around the centrifugal barrier and in the disk component. Hence, the drastic chemical change occurs at the centrifugal barrier. A discontinuous infalling motion as well as the gas-grain interaction would be responsible for the chemical change. This result will put an important constraint on initial chemical compositions for chemical evolution of <span class="hlt">protostellar</span> disks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22720503T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22720503T"><span id="translatedtitle"><span class="hlt">Protostellar</span> Multiplicity in Perseus Characterized by the VLA Nascent Disk and Multiplicity (VANDAM) Survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tobin, John J.; Looney, Leslie; Li, Zhi-Yun; Chandler, Claire J.; Dunham, Michael; Segura-Cox, Dominique; Sadavoy, Sarah; Melis, Carl; Harris, Robert J.; Kratter, Kaitlin M.; Perez, Laura M.</p> <p>2016-01-01</p> <p>The formation of multiple star <span class="hlt">systems</span> is thought to begin early in the star formation process. However, there have not been sufficient numbers of young protostars observed with high enough resolution to determine when and where most multiple <span class="hlt">systems</span> form. To significantly improve our knowledge of <span class="hlt">protostellar</span> multiplicity, we have carried out the VLA Nascent Disk and Multiplicity (VANDAM) survey, a 264 hour Jansky VLA program at wavelengths of 8 mm, 1 cm, 4 cm, and 6 cm toward all known Perseus protostars (N ~ 80) down to 15 AU (0.065") resolution. The unbiased nature of the survey has enabled us to conduct the most complete characterization of <span class="hlt">protostellar</span> multiplicity to date, finding evidence for a bi-modal distribution of multiple protostar <span class="hlt">system</span> separations. The bi-modal distribution may be evidence for multiple processes contributing to the formation of multiple <span class="hlt">systems</span>. The inner peak at ~75 AU could be produced from disk fragmentation, while the outer peak at ~3000 AU could be produced by turbulent and/or rotational fragmentation Moreover, three <span class="hlt">systems</span> are found to reside within larger, disk-like structures suggesting that they may be the product of disk fragmentation via gravitational instability. The results of this survey demonstrate the power and utility of unbiased surveys toward young stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930039981&hterms=mass+luminosity+relation+main+sequence+stars&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmass%2Bluminosity%2Brelation%2Bmain%2Bsequence%2Bstars','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930039981&hterms=mass+luminosity+relation+main+sequence+stars&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmass%2Bluminosity%2Brelation%2Bmain%2Bsequence%2Bstars"><span id="translatedtitle">Luminosity functions for very <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Laughlin, Gregory; Bodenheimer, Peter</p> <p>1993-01-01</p> <p>A theoretical investigation of the luminosity function for <span class="hlt">low-mass</span> objects to constrain the stellar initial mass function at the <span class="hlt">low-mass</span> end is reported. The ways in which luminosity functions for <span class="hlt">low-mass</span> stars are affected by star formation histories, brown dwarf and premain-sequence cooling rates and main-sequence mass luminosity relations, and the IMF are examined. Cooling rates and the mass-luminosity relation are determined through a new series of evolutionary calculations for very <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs in the range 0.05-0.50 solar mass. Model luminosity functions are constructed for specific comparison with the results of four recent observational surveys. The likelihood that the stellar mass function in the solar neighborhood is increasing at masses near the bottom of the main sequence and perhaps at lower masses is confirmed. In the most optimistic case, brown dwarfs contribute half of the local missing disk mass. The actual contribution is likely to be considerably less.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.437...96F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.437...96F"><span id="translatedtitle">On the corotation torque for <span class="hlt">low-mass</span> eccentric planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fendyke, Stephen M.; Nelson, Richard P.</p> <p>2014-01-01</p> <p>We present the results of high-resolution 2D simulations of <span class="hlt">low-mass</span> planets on fixed eccentric orbits embedded in protoplanetary discs. The aim of this study is to determine how the strength of the sustained, non-linear corotation torque experienced by embedded planets varies as a function of orbital eccentricity, disc parameters and planetary mass. In agreement with previous work we find that the corotation torque diminishes as orbital eccentricity, e, increases. Analysis of the time-averaged streamlines in the disc demonstrates that the width of the horseshoe region narrows as the eccentricity increases, and we suggest that this narrowing largely explains the observed decrease in the corotation torque. We employ three distinct methods for estimating the strength of the unsaturated corotation torque from our simulations, and provide an empirical fit to these results. We find that a simple model where the corotation torque, ΓC, decreases exponentially with increasing eccentricity [i.e. ΓC ∝ exp (-e/ef)] provides a good global fit to the data with an e-folding eccentricity, ef, that scales linearly with the disc scale height at the planet location. We confirm that this model provides a good fit for planet masses of 5 and 10 M⊕ in our simulations. The formation of planetary <span class="hlt">systems</span> is likely to involve significant planet-planet interactions that will excite eccentric orbits, and this is likely to influence disc-driven planetary migration through modification of the corotation torque. Our results suggest that high fidelity models of planetary formation should account for these effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994hst..prop.5469B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994hst..prop.5469B"><span id="translatedtitle">Externally Illuminated <span class="hlt">Proto-Stellar</span> Disks and Naked Jets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bally, John</p> <p>1994-01-01</p> <p>We propose to use HST to study <span class="hlt">low-mass</span> young stellar objects (YSOs) embedded in the Orion Nebula HII region. Radio, infrared, optical, and X-ray observations have identified a category of compact high density objects containing stellar cores. These objects are believed to be recently formed <span class="hlt">low</span> <span class="hlt">mass</span> stars that have become exposed by the intense UV radiation field of the hot stars responsible for excitation of the HII region. We propose to target 3 disk/YSO <span class="hlt">systems</span>, identified from recent HST observations, for detailed high-resolution imaging and low-resolution spectroscopy. Since these objects are externally illuminated by the light of nearby massive stars, they provide a unique opportunity to investigate the structure and kinematics of the circumstellar environment of a YSO at optical and UV wavelengths. Our data will be used to search for evidence of boundary layer accretion onto the YSO, to search for structure in the protoplanetary disk, and to investigate the nature of the externally induced disk ablation flow. The high spatial and spectral resolution of HST may lead to insights into the formation of proto-planetary disks, the birth of planets, and other Solar-<span class="hlt">system</span> type objects. We will use parallel observations with WFPC2 to serendipitously search for Herbig-Haro objects and visible YSO/disks in the surrounding Orion molecular cloud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...806L..29S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...806L..29S"><span id="translatedtitle">Lost in Secular Evolution: The Case of a <span class="hlt">Low-mass</span> Classical Bulge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saha, Kanak</p> <p>2015-06-01</p> <p>The existence of a classical bulge in disk galaxies holds an important clue to the assembly history of galaxies. Finding observational evidence of very <span class="hlt">low</span> <span class="hlt">mass</span> classical bulges, particularly in barred galaxies, including our Milky Way, is a challenging task as the bar-driven secular evolution might bring significant dynamical change to these bulges alongside the stellar disk. Using high-resolution N-body simulation, we show that if a cool stellar disk is assembled around a non-rotating <span class="hlt">low-mass</span> classical bulge, the disk rapidly grows a strong bar within a few rotation timescales. Later, the bar-driven secular process transforms the initial classical bulge into a flattened rotating stellar <span class="hlt">system</span> whose central part also has grown a barlike component rotating in sync with the disk bar. During this time, a boxy/peanut (hereafter B/P) bulge is formed via the buckling instability of the disk bar, and the vertical extent of this B/P bulge being slightly higher than that of the classical bulge, it encompasses the whole classical bulge. The resulting composite bulge appears to be both photometrically and kinematically identical to a B/P bulge without any obvious signature of the classical component. Our analysis suggests that many barred galaxies in the local universe might be hiding such <span class="hlt">low-mass</span> classical bulges. We suggest that stellar population and chemodynamical analysis might be required in establishing evidence for such <span class="hlt">low-mass</span> classical bulges.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AJ....152..112M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AJ....152..112M"><span id="translatedtitle">Very <span class="hlt">Low-mass</span> Stellar and Substellar Companions to Solar-like Stars from MARVELS. VI. A Giant Planet and a Brown Dwarf Candidate in a Close Binary <span class="hlt">System</span> HD 87646</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Bo; Ge, Jian; Wolszczan, Alex; Muterspaugh, Matthew W.; Lee, Brian; Henry, Gregory W.; Schneider, Donald P.; Martín, Eduardo L.; Niedzielski, Andrzej; Xie, Jiwei; Fleming, Scott W.; Thomas, Neil; Williamson, Michael; Zhu, Zhaohuan; Agol, Eric; Bizyaev, Dmitry; Nicolaci da Costa, Luiz; Jiang, Peng; Martinez Fiorenzano, A. F.; González Hernández, Jonay I.; Guo, Pengcheng; Grieves, Nolan; Li, Rui; Liu, Jane; Mahadevan, Suvrath; Mazeh, Tsevi; Nguyen, Duy Cuong; Paegert, Martin; Sithajan, Sirinrat; Stassun, Keivan; Thirupathi, Sivarani; van Eyken, Julian C.; Wan, Xiaoke; Wang, Ji; Wisniewski, John P.; Zhao, Bo; Zucker, Shay</p> <p>2016-11-01</p> <p>We report the detections of a giant planet (MARVELS-7b) and a brown dwarf (BD) candidate (MARVELS-7c) around the primary star in the close binary <span class="hlt">system</span>, HD 87646. To the best of our knowledge, it is the first close binary <span class="hlt">system</span> with more than one substellar circumprimary companion that has been discovered. The detection of this giant planet was accomplished using the first multi-object Doppler instrument (KeckET) at the Sloan Digital Sky Survey (SDSS) telescope. Subsequent radial velocity observations using the Exoplanet Tracker at the Kitt Peak National Observatory, the High Resolution Spectrograph at the Hobby Eberley telescope, the “Classic” spectrograph at the Automatic Spectroscopic Telescope at the Fairborn Observatory, and MARVELS from SDSS-III confirmed this giant planet discovery and revealed the existence of a long-period BD in this binary. HD 87646 is a close binary with a separation of ∼22 au between the two stars, estimated using the Hipparcos catalog and our newly acquired AO image from PALAO on the 200 inch Hale Telescope at Palomar. The primary star in the binary, HD 87646A, has {T}{eff} = 5770 ± 80 K, log g = 4.1 ± 0.1, and [Fe/H] = ‑0.17 ± 0.08. The derived minimum masses of the two substellar companions of HD 87646A are 12.4 ± 0.7 {M}{Jup} and 57.0 ± 3.7 {M}{Jup}. The periods are 13.481 ± 0.001 days and 674 ± 4 days and the measured eccentricities are 0.05 ± 0.02 and 0.50 ± 0.02 respectively. Our dynamical simulations show that the <span class="hlt">system</span> is stable if the binary orbit has a large semimajor axis and a low eccentricity, which can be verified with future astrometry observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2257335D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2257335D"><span id="translatedtitle">A Complex Organic Slushy Bathing <span class="hlt">Low-Mass</span> Protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drozdovskaya, Maria; Walsh, Catherine; Visser, Ruud; Harsono, Daniel; van Dishoeck, Ewine</p> <p>2015-08-01</p> <p>Complex organic molecules are ubiquitous companions of young forming stars. They were first observed in hot cores surrounding high-mass protostars [e.g., 1], but have since also been detected in the environs of several <span class="hlt">low-mass</span> counterparts [e.g., 2]. Recent studies have shown that colder envelopes and positions with impinging outflows may also glow with emission from complex organic species [e.g., 3, 4]. For this meeting, I would like to present physicochemical modeling results on the synthesis of complex organics in an envelope-cavity <span class="hlt">system</span> that is subject to non-thermal processing. This includes wavelength-dependent radiative transfer calculations with RADMC [5] and a comprehensive gas-grain chemical network [6]. The results show that the morphology of such a <span class="hlt">system</span> delineates three distinct regions: the cavity wall layer with time-dependent and species-variant enhancements; a torus rich in complex organic ices, but not reflected in gas-phase abundances; and the remaining outer envelope abundant in simpler solid and gaseous molecules. Within the adopted paradigm, complex organic molecules are demonstrated to have unique lifetimes and be grouped into early and late species [7]. Key chemical processes for forming and destroying complex organic molecules will be discussed. In addition, the results of adding newly experimentally verified routes [8] into the existing chemical networks will be shown.[1] Blake G. A., Sutton E. C., Masson C. R., Phillips T. G., 1987, ApJ, 315, 621[2] Jørgensen J. K., Favre C., Bisschop S. E., Bourke T. L., van Dishoeck E. F., Schmalzl M., 2012, ApJ, 757, L4[3] Arce H. G., Santiago-García J., Jørgensen J. K., Tafalla M., Bachiller R., 2008, ApJ, 681, L21[4] Öberg K. I., Bottinelli S., Jørgensen J. K., van Dishoeck E. F., 2010, ApJ, 716, 825[5] Dullemond C. P., Dominik C., 2004, A&A, 417, 159[6] Walsh C., Millar T. J., Nomura H., Herbst E., Widicus Weaver S., Aikawa Y., Laas J. C., Vasyunin A. I., 2014, A&A, 563, A33[7] Drozdovskaya</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22126742','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22126742"><span id="translatedtitle">MICROLENSING DISCOVERY OF A POPULATION OF VERY TIGHT, VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> BINARY BROWN DWARFS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Choi, J.-Y.; Han, C.; Udalski, A.; Sumi, T.; Gaudi, B. S.; Gould, A.; Bennett, D. P.; Dominik, M.; Beaulieu, J.-P.; Tsapras, Y.; Bozza, V.; Abe, F.; Furusawa, K.; Itow, Y.; Bond, I. A.; Ling, C. H.; Botzler, C. S.; Freeman, M.; Chote, P.; Fukui, A.; Collaboration: MOA Collaboration; OGLE Collaboration; muFUN Collaboration; MiNDSTEp Consortium; PLANET Collaboration; RoboNet Collaboration; and others</p> <p>2013-05-10</p> <p>Although many models have been proposed, the physical mechanisms responsible for the formation of <span class="hlt">low-mass</span> brown dwarfs (BDs) are poorly understood. The multiplicity properties and minimum mass of the BD mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very <span class="hlt">low</span> <span class="hlt">mass</span>, very tight binary <span class="hlt">systems</span>. These binaries have directly and precisely measured total <span class="hlt">system</span> masses of 0.025 M{sub Sun} and 0.034 M{sub Sun }, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field BD binaries known. The discovery of a population of such binaries indicates that BD binaries can robustly form at least down to masses of {approx}0.02 M{sub Sun }. Future microlensing surveys will measure a mass-selected sample of BD binary <span class="hlt">systems</span>, which can then be directly compared to similar samples of stellar binaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3382494','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3382494"><span id="translatedtitle">Mosquitoes survive raindrop collisions by virtue of their <span class="hlt">low</span> <span class="hlt">mass</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dickerson, Andrew K.; Shankles, Peter G.; Madhavan, Nihar M.; Hu, David L.</p> <p>2012-01-01</p> <p>In the study of insect flight, adaptations to complex flight conditions such as wind and rain are poorly understood. Mosquitoes thrive in areas of high humidity and rainfall, in which raindrops can weigh more than 50 times a mosquito. In this combined experimental and theoretical study, we here show that free-flying mosquitoes can survive the high-speed impact of falling raindrops. High-speed videography of those impacts reveals a mechanism for survival: A mosquito’s strong exoskeleton and <span class="hlt">low</span> <span class="hlt">mass</span> renders it impervious to falling drops. The mosquito’s <span class="hlt">low</span> <span class="hlt">mass</span> causes raindrops to lose little momentum upon impact and so impart correspondingly low forces to the mosquitoes. Our findings demonstrate that small fliers are robust to in-flight perturbations. PMID:22665779</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22665779','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22665779"><span id="translatedtitle">Mosquitoes survive raindrop collisions by virtue of their <span class="hlt">low</span> <span class="hlt">mass</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dickerson, Andrew K; Shankles, Peter G; Madhavan, Nihar M; Hu, David L</p> <p>2012-06-19</p> <p>In the study of insect flight, adaptations to complex flight conditions such as wind and rain are poorly understood. Mosquitoes thrive in areas of high humidity and rainfall, in which raindrops can weigh more than 50 times a mosquito. In this combined experimental and theoretical study, we here show that free-flying mosquitoes can survive the high-speed impact of falling raindrops. High-speed videography of those impacts reveals a mechanism for survival: A mosquito's strong exoskeleton and <span class="hlt">low</span> <span class="hlt">mass</span> renders it impervious to falling drops. The mosquito's <span class="hlt">low</span> <span class="hlt">mass</span> causes raindrops to lose little momentum upon impact and so impart correspondingly low forces to the mosquitoes. Our findings demonstrate that small fliers are robust to in-flight perturbations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.459..638B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.459..638B&link_type=ABSTRACT"><span id="translatedtitle">The different baryonic Tully-Fisher relations at <span class="hlt">low</span> <span class="hlt">masses</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brook, Chris B.; Santos-Santos, Isabel; Stinson, Greg</p> <p>2016-06-01</p> <p>We compare the Baryonic Tully-Fisher relation (BTFR) of simulations and observations of galaxies ranging from dwarfs to spirals, using various measures of rotational velocity Vrot. We explore the BTFR when measuring Vrot at the flat part of the rotation curve, Vflat, at the extent of H I gas, Vlast, and using 20 per cent (W20) and 50 per cent (W50) of the width of H I line profiles. We also compare with the maximum circular velocity of the parent halo, V_max^DM, within dark matter only simulations. The different BTFRs increasingly diverge as galaxy mass decreases. Using Vlast one obtains a power law over four orders of magnitude in baryonic mass, with slope similar to the observed BTFR. Measuring Vflat gives similar results as Vlast when galaxies with rising rotation curves are excluded. However, higher rotation velocities would be found for <span class="hlt">low-mass</span> galaxies if the cold gas extended far enough for Vrot to reach a maximum. W20 gives a similar slope as Vlast but with slightly lower values of Vrot for <span class="hlt">low-mass</span> galaxies, although this may depend on the extent of the gas in your galaxy sample. W50 bends away from these other relations towards low velocities at <span class="hlt">low</span> <span class="hlt">masses</span>. By contrast, V_max^DM bends towards high velocities for <span class="hlt">low-mass</span> galaxies, as cold gas does not extend out to the radius at which haloes reach V_max^DM. Our study highlights the need for careful comparisons between observations and models: one needs to be consistent about the particular method of measuring Vrot, and precise about the radius at which velocities are measured.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900026004&hterms=Inner+core&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DInner%2Bcore','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900026004&hterms=Inner+core&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DInner%2Bcore"><span id="translatedtitle"><span class="hlt">Protostellar</span> formation in rotating interstellar clouds. VIII - Inner core formation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boss, Alan P.</p> <p>1989-01-01</p> <p>The results are presented of a variety of spherically symmetric one-dimensional (1D) calculations intended to determine the robustness of the dynamical hiccup phenomenon in <span class="hlt">protostellar</span> cores. The 1D models show that the phenomenon is relatively insensitive to changes in the equations of state, numerical resolution, initial density and temperature, and the radiative transfer approximation. In 1D, the hiccup results in an explosive destruction of the entire inner <span class="hlt">protostellar</span> core. Inner core formation is studied with a sequence of three-dimensional models which show that rapid inner core rotation stabilizes the hiccup instability. Instead, the inner core becomes quite flat and undergoes a cycle of binary fragmentation, binary decay into a single object surrounded by a bar, breakup of the bar into a binary, etc. When lesser amounts of rotation are involved, the inner core does hiccup somewhat, but mass is ejected in only a few directions, leading to several broad streams of ejecta.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21560505','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21560505"><span id="translatedtitle">SIMULATING <span class="hlt">PROTOSTELLAR</span> JETS SIMULTANEOUSLY AT LAUNCHING AND OBSERVATIONAL SCALES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ramsey, Jon P.; Clarke, David A.</p> <p>2011-02-10</p> <p>We present the first 2.5-dimensional magnetohydrodynamic (MHD) simulations of <span class="hlt">protostellar</span> jets that include both the region in which the jet is launched magnetocentrifugally at scale lengths <0.1 AU and where the propagating jet is observed at scale lengths >10{sup 3} AU. These simulations, performed with the new adaptive mesh refinement MHD code AZEuS, reveal interesting relationships between conditions at the disk surface, such as the magnetic field strength, and direct observables such as proper motion, jet rotation, jet radius, and mass flux. By comparing these quantities with observed values, we present direct numerical evidence that the magnetocentrifugal launching mechanism is capable, by itself, of launching realistic <span class="hlt">protostellar</span> jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ApJS..174..202S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ApJS..174..202S"><span id="translatedtitle">A Case Study of <span class="hlt">Low-Mass</span> Star Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swift, Jonathan J.; Welch, William J.</p> <p>2008-01-01</p> <p>This article synthesizes observational data from an extensive program aimed toward a comprehensive understanding of star formation in a <span class="hlt">low-mass</span> star-forming molecular cloud. New observations and published data spanning from the centimeter wave band to the near-infrared reveal the high- and low-density molecular gas, dust, and pre-main-sequence stars in L1551. The total cloud mass of ~160 M⊙ contained within 0.9 pc has a dynamical timescale, tdyn = 1.1 Myr. Thirty-five pre-main-sequence stars with masses from ~0.1 to 1.5 M⊙ are selected to be members of the L1551 association constituting a total of 22 +/- 5 M⊙ of stellar mass. The observed star formation efficiency, SFE = 12% , while the total efficiency, SFEtot, is estimated to fall between 9% and 15%. L1551 appears to have been forming stars for several tdyn, with the rate of star formation increasing with time. Star formation has likely progressed from east to west, and there is clear evidence that another star or stellar <span class="hlt">system</span> will form in the high column density region to the northwest of L1551 IRS 5. High-resolution, wide-field maps of L1551 in CO isotopologue emission display the structure of the molecular cloud at 1600 AU physical resolution. The 13CO emission clearly reveals the disruption of the ambient cloud by outflows in the line core and traces the interface between regions of outflow and quiescent gas in the line wings. Kinetic energy from outflows is being deposited back into the cloud on a physical scale λpeak ≈ 0.05 pc at a rate, Ėinput ≈ 0.05 L⊙. The remaining energy afforded by the full mechanical luminosity of outflow in L1551 destroys the cloud or is otherwise lost to the greater interstellar medium. The C18O emission is optically thin and traces well the turbulent velocity structure of the cloud. The total turbulent energy is close to what is expected from virial equilibrium. The turbulent velocities exist primarily on small scales in the cloud, and the energy spectrum of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.459.1892S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.459.1892S&link_type=ABSTRACT"><span id="translatedtitle">Revealing the dynamics of Class 0 <span class="hlt">protostellar</span> discs with ALMA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seifried, D.; Sánchez-Monge, Á.; Walch, S.; Banerjee, R.</p> <p>2016-06-01</p> <p>We present synthetic ALMA observations of Keplerian, <span class="hlt">protostellar</span> discs in the Class 0 stage studying the emission of molecular tracers like 13CO, C18O, HCO+, H13CO+, N2H+, and H2CO. We model the emission of discs around low- and intermediate-mass protostars. We show that under optimal observing conditions ALMA is able to detect the discs already in the earliest stage of <span class="hlt">protostellar</span> evolution, although the emission is often concentrated to the innermost 50 au. Therefore, a resolution of a few 0.1 arcsec might be too low to detect Keplerian discs around Class 0 objects. We also demonstrate that under optimal conditions for edge-on discs Keplerian rotation signatures are recognisable, from which <span class="hlt">protostellar</span> masses can be inferred. For this we here introduce a new approach, which allows us to determine <span class="hlt">protostellar</span> masses with higher fidelity than before. Furthermore, we show that it is possible to reveal Keplerian rotation even for strongly inclined discs and that ALMA should be able to detect possible signs of fragmentation in face-on discs. In order to give some guidance for future ALMA observations, we investigate the influence of varying observing conditions and source distances. We show that it is possible to probe Keplerian rotation in inclined discs with an observing time of 2 h and a resolution of 0.1 arcsec, even in the case of moderate weather conditions. Furthermore, we demonstrate that under optimal conditions, Keplerian discs around intermediate-mass protostars should be detectable up to kpc distances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NewA...44...12K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NewA...44...12K"><span id="translatedtitle">Period change investigation of the <span class="hlt">low</span> <span class="hlt">mass</span> ratio contact binary BO Ari</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kriwattanawong, W.; Tasuya, O.; Poojon, P.</p> <p>2016-04-01</p> <p>A photometric study and period change analysis for the A-type <span class="hlt">low</span> <span class="hlt">mass</span> ratio contact binary BO Ari is presented. The BVR light curves were fitted by using the Wilson-Devinney method. The photometric solution yields a <span class="hlt">low</span> <span class="hlt">mass</span> ratio of q = 0.1754(±0.0016) with a contact degree of f = 27.72%(±2.37%). We found a long-term orbital period decrease at a rate of dPdt = - 3.49 ×10-7 d yr-1. This result indicates that the <span class="hlt">system</span> is undergoing mass transfer from the primary component to the secondary with a mass transfer rate of m˙1m1 = - 7.77 ×10-8 yr-1. With the period decrease, the inner and outer critical Roche surfaces will tighten and cause the degree of contact to increase. Therefore, BO Ari may evolve into a deeper contact <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22365202','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22365202"><span id="translatedtitle">Radius constraints from high-speed photometry of 20 <span class="hlt">low-mass</span> white dwarf binaries</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hermes, J. J.; Brown, Warren R.; Kilic, Mukremin; Gianninas, A.; Chote, Paul; Sullivan, D. J.; Winget, D. E.; Bell, Keaton J.; Falcon, R. E.; Winget, K. I.; Harrold, Samuel T.; Montgomery, M. H.; Mason, Paul A.</p> <p>2014-09-01</p> <p>We carry out high-speed photometry on 20 of the shortest-period, detached white dwarf binaries known and discover <span class="hlt">systems</span> with eclipses, ellipsoidal variations (due to tidal deformations of the visible white dwarf), and Doppler beaming. All of the binaries contain <span class="hlt">low-mass</span> white dwarfs with orbital periods of less than four hr. Our observations identify the first eight tidally distorted white dwarfs, four of which are reported for the first time here. We use these observations to place empirical constraints on the mass-radius relationship for extremely <span class="hlt">low-mass</span> (≤0.30 M {sub ☉}) white dwarfs. We also detect Doppler beaming in several of these binaries, which confirms their high-amplitude radial-velocity variability. All of these <span class="hlt">systems</span> are strong sources of gravitational radiation, and long-term monitoring of those that display ellipsoidal variations can be used to detect spin-up of the tidal bulge due to orbital decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ESS.....310202F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ESS.....310202F"><span id="translatedtitle">Securing the Extremely Low-Densities of <span class="hlt">Low-Mass</span> Planets Characterized by Transit Timing Variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ford, Eric B.</p> <p>2015-12-01</p> <p>Transit timing variations (TTVs) provide an excellent tool to characterize the masses and orbits of dozens of small planets, including many at orbital periods beyond the reach of both Doppler surveys and photoevaporation-induced atmospheric loss. Dynamical modeling of these <span class="hlt">systems</span> has identified <span class="hlt">low-mass</span> planets with surprisingly large radii and low densities (e.g., Kepler-79d, Jontof-Hutter et al. 2014; Kepler-51, Masuda 2014; Kepler-87c, Ofir et al. 2014). Additional low-density, <span class="hlt">low-mass</span> planets will likely become public before ESS III (Jontof-Hutter et al. in prep). Collectively, these results suggest that very low density planets with masses of 2-6 MEarth are not uncommon in compact multiple planet <span class="hlt">systems</span>. Some astronomers have questioned whether there could be an alternative interpretation of the TTV observations. Indeed, extraordinary claims require extraordinary evidence. While the physics of TTVs is rock solid, the statistical analysis of Kepler observations can be challenging, due to the complex interactions between model parameters and high-dimensional parameter spaces that must be explored. We summarize recent advances in computational statistics that enable robust characterization of planetary <span class="hlt">systems</span> using TTVs. We present updated analyses of a few particularly interesting <span class="hlt">systems</span> and discuss the implications for the robustness of extremely low densities for <span class="hlt">low-mass</span> planets. Such planets pose an interesting challenge for planet formation theory and are motivating detailed theoretical studies (e.g., Lee & Chiang 2015 and associated ESS III abstracts).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22734707W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22734707W"><span id="translatedtitle">Spatial Distribution of Small Organics in Prestellar and <span class="hlt">Protostellar</span> Cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waalkes, William; Guzman, Viviana; Oberg, Karin I.</p> <p>2016-01-01</p> <p>In the interstellar medium, formaldehyde (H2CO) has efficient formation pathways in both the gas-phase and on the surfaces of dust grains. Methanol (CH3OH), on the other hand, is believed to form exclusively on grains as there are no efficient gas-phase reactions leading to CH3OH. We present observations taken with the IRAM 30m telescope of several H2CO and CH3OH lines in a prestellar and <span class="hlt">protostellar</span> core. We investigated the formation pathways of H2CO and CH3OH by comparing their spatial distributions. We find that in the prestellar core, the two species are anti-correlated in the densest region, while their emission is correlated in the low-density region. In contrast, for the <span class="hlt">protostellar</span> core we find a correlation in the distribution of both species. We conclude that in the <span class="hlt">protostellar</span> source, H2CO and CH3OH form together on grains and have been thermally desorbed due to the central newly formed star. In the prestellar core, however, CH3OH forms on the ices and remains depleted in the coldest regions, while H2CO can form efficiently in the gas-phase. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22364166','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22364166"><span id="translatedtitle"><span class="hlt">PROTOSTELLAR</span> OUTFLOWS AND RADIATIVE FEEDBACK FROM MASSIVE STARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kuiper, Rolf; Yorke, Harold W.; Turner, Neal J. E-mail: Harold.W.Yorke@jpl.nasa.gov</p> <p>2015-02-20</p> <p>We carry out radiation hydrodynamical simulations of the formation of massive stars in the super-Eddington regime including both their radiative feedback and <span class="hlt">protostellar</span> outflows. The calculations start from a prestellar core of dusty gas and continue until the star stops growing. The accretion ends when the remnants of the core are ejected, mostly by the force of the direct stellar radiation in the polar direction and elsewhere by the reradiated thermal infrared radiation. How long the accretion persists depends on whether the <span class="hlt">protostellar</span> outflows are present. We set the mass outflow rate to 1% of the stellar sink particle's accretion rate. The outflows open a bipolar cavity extending to the core's outer edge, through which the thermal radiation readily escapes. The radiative flux is funneled into the polar directions while the core's collapse proceeds near the equator. The outflow thus extends the ''flashlight effect'', or anisotropic radiation field, found in previous studies from the few hundred AU scale of the circumstellar disk up to the 0.1 parsec scale of the core. The core's flashlight effect allows core gas to accrete on the disk for longer, in the same way that the disk's flashlight effect allows disk gas to accrete on the star for longer. Thus although the <span class="hlt">protostellar</span> outflows remove material near the core's poles, causing slower stellar growth over the first few free-fall times, they also enable accretion to go on longer in our calculations. The outflows ultimately lead to stars of somewhat higher mass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21565456','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21565456"><span id="translatedtitle">THE SURVEY OF H I IN EXTREMELY <span class="hlt">LOW-MASS</span> DWARFS (SHIELD)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cannon, John M.; Engstrom, Eric; Allan, John; Erny, Grace; Fliss, Palmer; Smith, AnnaLeigh</p> <p>2011-09-20</p> <p>We present first results from the Survey of H I in Extremely <span class="hlt">Low-mass</span> Dwarfs (SHIELD), a multi-configuration Expanded Very Large Array (EVLA) study of the neutral gas contents and dynamics of galaxies with H I masses in the 10{sup 6}-10{sup 7} M{sub sun} range detected by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We describe the survey motivation and concept demonstration using Very Large Array imaging of six <span class="hlt">low-mass</span> galaxies detected in early ALFALFA data products. We then describe the primary scientific goals of SHIELD and present preliminary EVLA and WIYN 3.5 m imaging of the 12 SHIELD galaxies. With only a few exceptions, the neutral gas distributions of these extremely <span class="hlt">low-mass</span> galaxies are centrally concentrated. In only one <span class="hlt">system</span> have we detected H I column densities higher than 10{sup 21} cm{sup -2}. Despite this, the stellar populations of all of these <span class="hlt">systems</span> are dominated by blue stars. Further, we find ongoing star formation as traced by H{alpha} emission in 10 of the 11 galaxies with H{alpha} imaging obtained to date. Taken together these results suggest that extremely <span class="hlt">low-mass</span> galaxies are forming stars in conditions different from those found in more massive <span class="hlt">systems</span>. While detailed dynamical analysis requires the completion of data acquisition, the most well-resolved <span class="hlt">system</span> is amenable to meaningful position-velocity analysis. For AGC 749237, we find well-ordered rotation of 30 km s{sup -1} at {approx}40'' distance from the dynamical center. At the adopted distance of 3.2 Mpc, this implies the presence of a {approx}>1 x 10{sup 8} M{sub sun} dark matter halo and a baryon fraction {approx}<0.1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/886668','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/886668"><span id="translatedtitle">Evolution of Intermediate and <span class="hlt">Low</span> <span class="hlt">Mass</span> Binary <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Eggleton, P P</p> <p>2005-10-25</p> <p>There are a number of binaries, fairly wide and with one or even two evolved giant components, that do not agree very well with conventional stellar evolution: the secondaries are substantially larger (oversized) than they should be because their masses are quite low compared with the primaries. I discuss the possibility that these binaries are former triples, in which a merger has occurred fairly recently in a short-period binary sub-component. Some mergers are expected, and may follow a phase of contact evolution. I suggest that in contact there is substantial transfer of luminosity between the components due to differential rotation, of the character observed by helioseismology in the Sun's surface convection zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.......361B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.......361B"><span id="translatedtitle">Observational Constraints on <span class="hlt">Low-Mass</span> Stellar Evolution and Planet Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Birkby, Jayne Louise</p> <p>2011-07-01</p> <p><span class="hlt">Low-mass</span> stars (? < 1.0M⊙) account for more than 70% of the galactic stellar population yet models describing the evolution of their fundamental properties lack stringent observational constraints, especially at early ages. Furthermore, recent observations indicate a significant discrepancy between model predictions and the precise (2 - 3%) observed, dynamical masses and radii measured using <span class="hlt">low-mass</span> eclipsing binary <span class="hlt">systems</span> (EBs). Additionally, the theory of planet formation via core accretion predicts notably less hot-Jupiter formation around M-dwarfs (Mdot ? ≤ 0.6M⊙), but as yet, no large enough study exists to robustly test it. Further still, it is predicted that the dynamic environment of stellar clusters, in which most stars are believed to form, hampers planet formation, but again, current null detections of planets in stellar clusters are not statistically significant to test the theory. More observations are required to cement both the theory of <span class="hlt">low-mass</span> stellar evolution and planet formation. This thesis aims to provide the necessary constraints by uncovering new <span class="hlt">low-mass</span> EBs and transiting exoplanets in time-series photometry and follow-up spectroscopy from the Monitor project, a photometric monitoring campaign of <span class="hlt">low-mass</span> stars in nine young open clusters, and in the WFCAM Transit Survey (WTS), a photometric monitoring campaign of ∼10,000 field M-dwarfs. Chapters 3 and 4 present my study of the young (130 Myr) cluster, M 50. I confirm three EB candidates as cluster members, including evidence that one of these is in a triple <span class="hlt">system</span> with a wide-separation, <span class="hlt">low-mass</span> tertiary component. The derived masses and radii for this <span class="hlt">system</span> and one further double-lined, non-cluster member are presented, but these objects required dedicated, single-slit spectroscopic follow-up to yield the accuracy required to test pre-main sequence models. My non-detection of planets in this cluster is consistent with the results of all other cluster transit surveys. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2254897G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2254897G"><span id="translatedtitle">Age-dating <span class="hlt">Low-Mass</span> Star-Forming Galaxies at intermediate redshifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Barro, Guillermo; Gomez-Guijarro, Carlos; Villar, Víctor</p> <p>2015-08-01</p> <p>Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that <span class="hlt">low-mass</span> <span class="hlt">systems</span> merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf <span class="hlt">systems</span> might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of <span class="hlt">low-mass</span> <span class="hlt">systems</span> at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of <span class="hlt">low-mass</span> dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present physical properties and constraints on the star formation histories (SFHs) of a sample of <span class="hlt">low-mass</span> Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFHs were obtained through the analysis of their spectral energy distributions using a novel approach (Pacifici et al. 2012) that (1) consistently combines photometric (HST and ground-based multi-broadband) and spectroscopic (equivalent widths of emission lines from VLT and GTC spectroscopy) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time.The median SFH of our LMSFGs appears to form 90% of the median stellar mass inferred for the sample in the ˜0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for dwarf SFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for a slightly more massive secondary sample 8.0 < log M∗/Mo < 9.1).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2254872G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2254872G"><span id="translatedtitle">On the formation redshift of <span class="hlt">Low-Mass</span> Star-Forming Galaxies at intermediate redshifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Barro, Guillermo; Gomez-Guijarro, Carlos; Villar, Víctor</p> <p>2015-08-01</p> <p>Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that <span class="hlt">low-mass</span> <span class="hlt">systems</span> merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf <span class="hlt">systems</span> might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of <span class="hlt">low-mass</span> <span class="hlt">systems</span> at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of <span class="hlt">low-mass</span> dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present constraints on the star formation histories (SFHs) of a sample of <span class="hlt">low-mass</span> Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFHs were obtained through the analysis of their spectral energy distributions using a novel approach (Pacifici et al. 2012) that (1) consistently combines photometric (HST and ground-based multi-broadband) and spectroscopic (equivalent widths of emission lines from VLT and GTC spectroscopy) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time.The median SFH of our LMSFGs appears to form 90% of the median stellar mass inferred for the sample in the ˜0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for dwarf SFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for a slightly more massive secondary sample 8.0 < log M∗/Mo < 9.1).This is a pilot study for future surveys on dwarf galaxies at high redshift.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22130971','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22130971"><span id="translatedtitle">UNVEILING A POPULATION OF GALAXIES HARBORING <span class="hlt">LOW-MASS</span> BLACK HOLES WITH X-RAYS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schramm, M.; Silverman, J. D.; Greene, J. E.; Brandt, W. N.; Luo, B.; Xue, Y. Q.; Capak, P.; Kakazu, Y.; Kartaltepe, J.; Mainieri, V.</p> <p>2013-08-20</p> <p>We report the discovery of three <span class="hlt">low-mass</span> black hole (BH) candidates residing in the centers of <span class="hlt">low-mass</span> galaxies at z < 0.3 in the Chandra Deep Field-South Survey. These BHs are initially identified as candidate active galactic nuclei based on their X-ray emission in deep Chandra observations. Multi-wavelength observations are used to strengthen our claim that such emission is powered by an accreting supermassive BH. While the X-ray luminosities are low at L{sub X} {approx} 10{sup 40} erg s{sup -1} (and variable in one case), we argue that they are unlikely to be attributed to star formation based on H{alpha} or UV fluxes. Optical spectroscopy from Keck and the VLT allows us to (1) measure accurate redshifts, (2) confirm their low stellar host mass, (3) investigate the source(s) of photo-ionization, and (4) estimate extinction. With stellar masses of M{sub *} < 3 Multiplication-Sign 10{sup 9} M{sub Sun} determined from Hubble Space Telescope/Advanced Camera for Surveys imaging, the host galaxies are among the lowest mass <span class="hlt">systems</span> known to host actively accreting BHs. We estimate BH masses M{sub BH} {approx} 2 Multiplication-Sign 10{sup 5} M{sub Sun} based on scaling relations between BH mass and host properties for more luminous <span class="hlt">systems</span>. In one case, a broad component of the H{alpha} emission-line profile is detected, thus providing a virial mass estimate. BHs in such <span class="hlt">low-mass</span> galaxies are of considerable interest as the low-redshift analogs to the seeds of the most massive BHs at high redshift which have remained largely elusive to date. Our study highlights the power of deep X-ray surveys to uncover such <span class="hlt">low-mass</span> <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010A%26A...519A...3L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010A%26A...519A...3L"><span id="translatedtitle">c2d Spitzer IRS spectra of embedded <span class="hlt">low-mass</span> young stars: gas-phase emission lines</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lahuis, F.; van Dishoeck, E. F.; Jørgensen, J. K.; Blake, G. A.; Evans, N. J.</p> <p>2010-09-01</p> <p>Context. A survey of mid-infrared gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded <span class="hlt">low-mass</span> young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer “Cores to Disks” (c2d) legacy program. Aims: The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, <span class="hlt">protostellar</span> disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. The mid-IR spectral range hosts a suite of diagnostic lines which can distinguish them. A key point is to spatially resolve the emission in the Spitzer-IRS spectra to separate extended PDR and shock emission from compact source emission associated with the circumstellar disk and jets. Methods: An optimal extraction method is used to separate both spatially unresolved (compact, up to a few hundred AU) and spatially resolved (extended, thousand AU or more) emission from the IRS spectra. The results are compared with the c2d disk sample and literature PDR and shock models to address the physical nature of the sources. Results: Both compact and extended emission features are observed. Warm (T_ex few hundred K) H2, observed through the pure rotational H2 S(0), S(1) and S(2) lines, and [S i] 25 μm emission is observed primarily in the extended component. [S i] is observed uniquely toward truly embedded sources and not toward disks. On the other hand hot (T_ex ⪆ 700 K) H2, observed primarily through the S(4) line, and [Ne ii] emission is seen mostly in the spatially unresolved component. [Fe ii] and [Si ii] lines are observed in both spatial components. Hot H2O emission is found in the spatially unresolved component of some sources. Conclusions: The observed emission on ≥1000 AU scales is characteristic of PDR emission and likely originates in the outflow cavities in the remnant envelope created by the stellar wind and jets from the embedded</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...826....9I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...826....9I"><span id="translatedtitle">Where are the <span class="hlt">Low-mass</span> Population III Stars?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ishiyama, Tomoaki; Sudo, Kae; Yokoi, Shingo; Hasegawa, Kenji; Tominaga, Nozomu; Susa, Hajime</p> <p>2016-07-01</p> <p>We study the number and the distribution of <span class="hlt">low-mass</span> Population III (Pop III) stars in the Milky Way. In our numerical model, hierarchical formation of dark matter minihalos and Milky-Way-sized halos are followed by a high-resolution cosmological simulation. We model the Pop III formation in H2 cooling minihalos without metal under UV radiation of the Lyman-Werner bands. Assuming a Kroupa initial mass function (IMF) from 0.15 to 1.0 M ⊙ for <span class="hlt">low-mass</span> Pop III stars, as a working hypothesis, we try to constrain the theoretical models in reverse by current and future observations. We find that the survivors tend to concentrate on the center of halo and subhalos. We also evaluate the observability of Pop III survivors in the Milky Way and dwarf galaxies, and constraints on the number of Pop III survivors per minihalo. The higher latitude fields require lower sample sizes because of the high number density of stars in the galactic disk, the required sample sizes are comparable in the high- and middle-latitude fields by photometrically selecting low-metallicity stars with optimized narrow-band filters, and the required number of dwarf galaxies to find one Pop III survivor is less than 10 at <100 kpc for the tip of red giant stars. Provided that available observations have not detected any survivors, the formation models of <span class="hlt">low-mass</span> Pop III stars with more than 10 stars per minihalo are already excluded. Furthermore, we discuss the way to constrain the IMF of Pop III stars at a high mass range of ≳10 M ⊙.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22713605N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22713605N"><span id="translatedtitle">SHIELD II: AGC 198507 - An Extremely Rare <span class="hlt">Low-Mass</span> Galaxy Interaction?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikolina Borg Stevens, Karin; Cannon, John M.; McNichols, Andrew; McQuinn, Kristen B.; Teich, Yaron; SHIELD II Team</p> <p>2016-01-01</p> <p>The "Survey of HI in Extremely <span class="hlt">Low-mass</span> Dwarfs II" ("SHIELD II") is a multiwavelength, legacy-class observational campaign that is facilitating the study of both internal and global evolutionary processes in <span class="hlt">low-mass</span> dwarf galaxies discovered by the Arecibo Legacy Fast ALFA (ALFALFA) survey. New HST imaging of one of these sample galaxies, AGC 198507, has revealed it to be a very rare interacting <span class="hlt">system</span>; to our knowledge this is one of only a few known interactions in this extreme mass range. WSRT imaging indicates that the bulk of the HI is associated with the more luminous AGC 198507, while low surface brightness gas extends toward and coincides with the less luminous companion, which is separated by roughly 1.5 kpc from AGC 198507. Here we present new VLA B configuration HI imaging that allows us to localize the HI gas, to examine the rotational dynamics of AGC 198507, and to study the nature of star formation in this unique <span class="hlt">low-mass</span> interacting <span class="hlt">system</span>.Support for this work was provided by NSF grant AST-1211683 to JMC at Macalester College, and by NASA through grant GO-13750 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110020761','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110020761"><span id="translatedtitle">Extremely <span class="hlt">Low</span> <span class="hlt">Mass</span>: The Circumstellar Envelope of a Potential Proto-Brown Dwarf</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wiseman, Jennifer</p> <p>2011-01-01</p> <p>What is the environment for planet formation around extremely <span class="hlt">low</span> <span class="hlt">mass</span> stars? Is the environment around brown dwarfs and extremely <span class="hlt">low</span> <span class="hlt">mass</span> stars conducive and sufficiently massive for planet production? The determining conditions may be set very early in the process of the host object's formation. IRAS 16253-2429, the source of the Wasp-Waist Nebula seen in Spitzer IRAC images, is an isolated, very low luminosity ("VeLLO") Class 0 protostar in the nearby rho Ophiuchi cloud. We present VLA ammonia mapping observations of the dense gas envelope feeding the central core accreting <span class="hlt">system</span>. We find a flattened envelope perpendicular to the outflow axis, and gas cavities that appear to cradle the outflow lobes as though carved out by the flow and associated (apparently precessing) jet, indicating environmental disruption. Based on the NH3 (1,1) and (2,2) emission distribution, we derive the mass, velocity fields and temperature distribution for the envelope. We discuss the combined evidence for this source to be one of the youngest and lowest mass sources in formation yet known, and discuss the ramifications for planet formation potential in this extremely <span class="hlt">low</span> <span class="hlt">mass</span> <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ASPC..472..231L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ASPC..472..231L"><span id="translatedtitle">Outer Atmospheres of <span class="hlt">Low</span> <span class="hlt">Mass</span> Stars — Flare Characteristics.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lalitha, S.; Schmitt, J. H. M. M.</p> <p>2013-04-01</p> <p>We compare the coronal properties during flares on active <span class="hlt">low</span> <span class="hlt">mass</span> stars CN Leonis, AB Doradus A and Proxima Centauri observed with XMM-Newton. From the X-ray data we analyze the temporal evolution of temperature, emission measure and coronal abundance. The nature of these flares are with secondary events following the first flare peak in the light curve, raising the question regarding the involved magnetic structure. We infer from the plasma properties and the geometry of the flaring structure that the flare originates from a compact arcade rather than in a single loop.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22714204T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22714204T"><span id="translatedtitle">The Motion Verified Red Stars (MoVeRS) Catalog and <span class="hlt">Low-Mass</span> Field Stars with Warm Dust</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Theissen, Christopher; West, Andrew A.; Dhital, Saurav</p> <p>2016-01-01</p> <p>We present the Motion Verified Red Stars (MoVeRS) catalog of proper motion selected <span class="hlt">low-mass</span> stars from SDSS, 2MASS, and WISE. These surveys provide a time baseline of ~12 years for sources found in all three surveys, and a precision better than 10 mas/year.The MoVeRS catalog is augmented with proper motions from SDSS+USNO-B and the full sample contains 8,735,004 photometric point-sources selected based on colors and their significant (2σ) proper motions. This catalog will be useful for finding new <span class="hlt">low-mass</span> common proper motion <span class="hlt">systems</span>, along with providing a large input catalog for numerous studies of <span class="hlt">low-mass</span> stars. In addition, we use the MoVeRS catalog to present a preliminary sample of <span class="hlt">low-mass</span> field stars exhibiting signatures of warm dust (mid-infrared excesses). Such <span class="hlt">systems</span> are thought to originate from collisions of terrestrial planets, raising even more questions about the habitability of planetary <span class="hlt">systems</span> around <span class="hlt">low-mass</span> stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/374932','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/374932"><span id="translatedtitle"><span class="hlt">Low</span> <span class="hlt">mass</span> large aperture vacuum window development at CEBAF</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Keppel, C.</p> <p>1995-04-01</p> <p>Large aperture <span class="hlt">low</span> <span class="hlt">mass</span> vacuum windows are being developed for the HMS (High Momentum Spectrometer) and SOS (Short Orbit Spectrometer) spectrometers in Hall C at CEBAF. Because multiple scattering degrades the performance of a spectrometer it is important that the volume be evacuated and that the entrance and exit windows be as <span class="hlt">low</span> <span class="hlt">mass</span> as possible. The material used for such windows must be thin and light enough so as to have minimum effect of the beam, and at the same time, be thick and strong enough to operate reliably and safely. To achieve these goals, composite vacuum windows have been constructed of a thin sheet of Mylar with a reinforcing fabric. Reinforcing fabrics such as Kevlar and Spectra are available with tensile strengths significantly greater than that of Mylar. A thin layer of Myler remains necessary since the fabrics cannot achieve any sort of vacuum seal. The design, fabrication, testing, and operating experience with such composite windows for the Hall C spectrometers will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22356634','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22356634"><span id="translatedtitle">Angular momentum transport within evolved <span class="hlt">low-mass</span> stars</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cantiello, Matteo; Bildsten, Lars; Paxton, Bill; Mankovich, Christopher; Christensen-Dalsgaard, Jørgen</p> <p>2014-06-10</p> <p>Asteroseismology of 1.0-2.0 M {sub ☉} red giants by the Kepler satellite has enabled the first definitive measurements of interior rotation in both first ascent red giant branch (RGB) stars and those on the helium burning clump. The inferred rotation rates are 10-30 days for the ≈0.2 M {sub ☉} He degenerate cores on the RGB and 30-100 days for the He burning core in a clump star. Using the Modules for Experiments in Stellar Evolution code, we calculate state-of-the-art stellar evolution models of <span class="hlt">low</span> <span class="hlt">mass</span> rotating stars from the zero-age main sequence to the cooling white dwarf (WD) stage. We include transport of angular momentum due to rotationally induced instabilities and circulations, as well as magnetic fields in radiative zones (generated by the Tayler-Spruit dynamo). We find that all models fail to predict core rotation as slow as observed on the RGB and during core He burning, implying that an unmodeled angular momentum transport process must be operating on the early RGB of <span class="hlt">low</span> <span class="hlt">mass</span> stars. Later evolution of the star from the He burning clump to the cooling WD phase appears to be at nearly constant core angular momentum. We also incorporate the adiabatic pulsation code, ADIPLS, to explicitly highlight this shortfall when applied to a specific Kepler asteroseismic target, KIC8366239.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012noao.prop..222S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012noao.prop..222S"><span id="translatedtitle">New <span class="hlt">Low-Mass</span> Members of Nearby Young Moving Groups</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlieder, Joshua; Simon, Michal; Rice, Emily; Lepine, Sebastien</p> <p>2012-08-01</p> <p>We are now ready to expand our program to identify new <span class="hlt">low-mass</span> members of nearby young moving groups (NYMGs) to stars of mass ≤0.3 M_⊙. This is important to: (1) complete the census of <span class="hlt">low-mass</span> stars near the Sun, (2) provide high priority targets for disk and exoplanet studies by direct imaging, and (3) provide a well- characterized sample of nearby, young stars for detailed study of their physical and kinematic properties. Our proven technique starts with a proper motion selection algorithm, proceeds to vet the sample for indicators of youth, and requires as its last step the measurement of candidate member radial velocities (RVs). So far, we have measured more than 100 candidate RVs using CSHELL on the NASA-IRTF and PHOENIX on Gemini-South, yielding more than 50 likely new moving group members. Here we propose to continue our RV follow-up of candidate NYMG members using PHOENIX on the KPNO 4m. We aim to measure RVs and determine spectral types of 23 faint (V≥15, H≥9), late-type (≥M4) candidates of the (beta) Pic (10 Myrs), AB Dor (70 Myrs), Tuc/Hor (30 Myrs), and TW Hydrae (8 Myrs) moving groups.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EAS....57...91H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EAS....57...91H"><span id="translatedtitle">Formation of <span class="hlt">Low-Mass</span> Stars and Brown Dwarfs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hennebelle, P.</p> <p>2012-11-01</p> <p>These lectures attempt to expose the most important ideas, which have been proposed to explain the formation of stars with particular emphasis on the formation of brown dwarfs and <span class="hlt">low-mass</span> stars. We first describe the important physical processes which trigger the collapse of a self-gravitating piece of fluid and regulate the star formation rate in molecular clouds. Then we review the various theories which have been proposed along the years to explain the origin of the stellar initial mass function paying particular attention to four models, namely the competitive accretion and the theories based respectively on stopped accretion, MHD shocks and turbulent dispersion. As it is yet unsettled whether the brown dwarfs form as <span class="hlt">low-mass</span> stars, we present the theory of brown dwarfs based on disk fragmentation stressing all the uncertainties due to the radiative feedback and magnetic field. Finally, we describe the results of large scale simulations performed to explain the collapse and fragmentation of molecular clouds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21499359','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21499359"><span id="translatedtitle"><span class="hlt">Low-mass</span> dilepton rate from the deconfined phase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Greiner, Carsten; Haque, Najmul</p> <p>2011-01-15</p> <p>We discuss <span class="hlt">low-mass</span> dilepton rates ({<=}1 GeV) from the deconfined phase of QCD using both perturbative and nonperturbative models and compare them with those from lattice gauge theory and in-medium hadron gas. Our analysis suggests that the rate at very low invariant mass (M{<=}200 MeV) using the nonperturbative gluon condensate in a semiempirical way within the Green function approach dominates over the Born rate, independent of any uncertainty associated with the choice of the strong coupling in perturbation theory. On the other hand, the rate from {rho}-q interaction in the deconfined phase is important at 200 MeV {<=}M{<=} 1 GeV as it is almost of same order as the Born rate as well as the in-medium hadron gas rate. Also, the higher order perturbative rate, leaving aside its various uncertainties, from the hard-thermal-loop approximation becomes reliable at M{>=}200 MeV and also becomes comparable with the Born rate and the lattice rate for M{>=}500 MeV, constraining on the broad resonance structures in the dilepton rate at large invariant mass. We also discuss the lattice constraints on the <span class="hlt">low-mass</span> dilepton rate. Furthermore, we discuss a realistic way to advocate the quark-hadron duality hypothesis based on the dilepton rates from quark-gluon plasma and hadron gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21583218','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21583218"><span id="translatedtitle"><span class="hlt">LOW-MASS</span> ECLIPSING BINARIES IN THE INITIAL KEPLER DATA RELEASE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Coughlin, J. L.; Harrison, T. E.; Ule, N.; Lopez-Morales, M.; Hoffman, D. I.</p> <p>2011-03-15</p> <p>We identify 231 objects in the newly released Cycle 0 data set from the Kepler Mission as double-eclipse, detached eclipsing binary <span class="hlt">systems</span> with T{sub eff} < 5500 K and orbital periods shorter than {approx}32 days. We model each light curve using the JKTEBOP code with a genetic algorithm to obtain precise values for each <span class="hlt">system</span>. We identify 95 new <span class="hlt">systems</span> with both components below 1.0 M{sub sun} and eclipses of at least 0.1 mag, suitable for ground-based follow-up. Of these, 14 have periods less than 1.0 day, 52 have periods between 1.0 and 10.0 days, and 29 have periods greater than 10.0 days. This new sample of main-sequence, <span class="hlt">low-mass</span>, double-eclipse, detached eclipsing binary candidates more than doubles the number of previously known <span class="hlt">systems</span> and extends the sample into the completely heretofore unexplored P > 10.0 day period regime. We find preliminary evidence from these <span class="hlt">systems</span> that the radii of <span class="hlt">low-mass</span> stars in binary <span class="hlt">systems</span> decrease with period. This supports the theory that binary spin-up is the primary cause of inflated radii in <span class="hlt">low-mass</span> binary <span class="hlt">systems</span>, although a full analysis of each <span class="hlt">system</span> with radial-velocity and multi-color light curves is needed to fully explore this hypothesis. Also, we present seven new transiting planet candidates that do not appear among the list of 706 candidates recently released by the Kepler team, or in the Kepler False Positive Catalog, along with several other new and interesting <span class="hlt">systems</span>. We also present novel techniques for the identification, period analysis, and modeling of eclipsing binaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...809..146B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...809..146B"><span id="translatedtitle">A Study in Blue: The Baryon Content of Isolated <span class="hlt">Low-mass</span> Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bradford, Jeremy D.; Geha, Marla C.; Blanton, Michael R.</p> <p>2015-08-01</p> <p>We study the baryon content of <span class="hlt">low-mass</span> galaxies selected from the Sloan Digital Sky Survey (SDSS DR8), focusing on galaxies in isolated environments where the complicating physics of galaxy–galaxy interactions are minimized. We measure neutral hydrogen (HI) gas masses and line widths for 148 isolated galaxies with stellar mass between 107 and {10}9.5{M}ȯ . We compare isolated <span class="hlt">low-mass</span> galaxies to more massive galaxies and galaxies in denser environments by remeasuring HI emission lines from the Arecibo Legacy Fast ALFA survey 40% data release. All isolated <span class="hlt">low-mass</span> galaxies either have large atomic gas fractions or large atomic gas fractions cannot be ruled out via their upper limits. We measure a median atomic gas fraction of {f}{gas}=0.81+/- 0.13 for our isolated <span class="hlt">low-mass</span> sample with no <span class="hlt">systems</span> below 0.30. At all stellar masses, the correlations between galaxy radius, baryonic mass, and velocity width are not significantly affected by environment. Finally, we estimate a median baryon to total dynamical mass fraction of {f}{baryon,{disk}}=0.15+/- 0.17. We also estimate two different median baryon to halo mass fractions using the results of semi-analytic models ({f}{baryon,{halo}}=0.04+/- 0.06) and abundance matching ({f}{baryon,{halo}}=0.04+/- 0.02). Baryon fractions estimated directly using HI observations appear independent of environment and maximum circular velocity, while baryon fractions estimated using abundance matching show a significant depletion of baryons at low maximum circular velocities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009A%26A...507.1617D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009A%26A...507.1617D"><span id="translatedtitle">Evolutionary implications of the new triple-α nuclear reaction rate for <span class="hlt">low</span> <span class="hlt">mass</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dotter, A.; Paxton, B.</p> <p>2009-12-01</p> <p>Context: Ogata et al. (2009, Progr. Theor. Phys., 122, 1055) presented a theoretical determination of the ^4He(αα,γ)12C, or triple-α, nuclear reaction rate. Their rate differs from the NACRE rate by many orders of magnitude at temperatures relevant for <span class="hlt">low</span> <span class="hlt">mass</span> stars. Aims: We explore the evolutionary implications of adopting the OKK triple-α reaction rate in <span class="hlt">low</span> <span class="hlt">mass</span> stars and compare the results with those obtained using the NACRE rate. Methods: The triple-α reaction rates are compared by following the evolution of stellar models at 1 and 1.5 M⊙ with Z = 0.0002 and Z = 0.02. Results: Results show that the OKK rate has severe consequences for the late stages of stellar evolution in <span class="hlt">low</span> <span class="hlt">mass</span> stars. Most notable is the shortening-or disappearance-of the red giant phase. Conclusions: The OKK triple-α reaction rate is incompatible with observations of extended red giant branches and He burning stars in old stellar <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22821704T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22821704T"><span id="translatedtitle">A Systematic Search for <span class="hlt">Low-mass</span> Field Stars with Large Infrared Excesses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Theissen, Christopher; West, Andrew A.</p> <p>2016-06-01</p> <p>We present a systematic search for <span class="hlt">low-mass</span> field stars exhibiting extreme infrared (IR) excesses. One potential cause of the IR excess is the collision of terrestrial worlds. Our input stars are from the Motion Verified Red Stars (MoVeRS) catalog. Candidate stars are then selected based on large deviations (3σ) between their measured Wide-field Infrared Survey Explorer (WISE) 12 μm flux and their expected flux (as estimated from stellar models). We investigate the stellar mass and time dependence for stars showing extreme IR excesses, using photometric colors from the Sloan Digital Sky Survey (SDSS) and Galactic height as proxies for mass and time, respectively. Using a Galactic kinematic model, we estimate the completeness for our sample as a function of line-of-sight through the Galaxy, estimating the number of <span class="hlt">low-mass</span> stars that should exhibit extreme IR excesses within a local volume. The potential for planetary collisions to occur over a large range of stellar masses and ages has serious implications for the habitability of planetary <span class="hlt">systems</span> around <span class="hlt">low-mass</span> stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999AAS...194.6805W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999AAS...194.6805W"><span id="translatedtitle">SCUBA and HIRES Results for <span class="hlt">Protostellar</span> Cores in the MON OB1 Dark Cloud</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolf-Chase, G.; Moriarty-Schieven, G.; Fich, M.; Barsony, M.</p> <p>1999-05-01</p> <p>We have used HIRES-processing of IRAS data and point-source modelling techniques (Hurt & Barsony 1996; O'Linger 1997; Barsony et al. 1998), together with submillimeter continuum imaging using the Submillimeter Common-User Bolometer Array (SCUBA) on the 15-meter James Clerk Maxwell Telescope (JCMT), to search CS cores in the Mon OB1 dark cloud (Wolf-Chase, Walker, & Lada 1995; Wolf-Chase & Walker 1995) for deeply embedded sources. These observations, as well as follow-up millimeter photometry at the National Radio Astronomy Observatory (NRAO) 12-meter telescope on Kitt Peak, have lead to the identification of two Class 0 <span class="hlt">protostellar</span> candidates, which were previously unresolved from two brighter IRAS point sources (IRAS 06382+0939 & IRAS 06381+1039) in this cloud. Until now, only one Class 0 object had been confirmed in Mon OB1; the driving source of the highly-collimated outflow NGC 2264 G (Ward-Thompson, Eiroa, & Casali 1995; Margulis et al. 1990; Lada & Fich 1996), which lies well outside the extended CS cores. One of the new Class 0 candidates may be an intermediate-mass source associated with an H_2O maser, and the other object is a <span class="hlt">low-mass</span> source which may be associated with a near-infrared jet, and possibly with a molecular outflow. We report accurate positions for the new Class 0 candidates, based on the SCUBA images, and present new SEDs for these sources, as well as for the brighter IRAS point sources. A portion of this work was performed while GWC held a President's Fellowship from the University of California. MB and GWC gratefully acknowledge financial support from MB's NSF CAREER Grant, AST97-9753229.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApJ...765...85K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApJ...765...85K"><span id="translatedtitle">Unveiling the Detailed Density and Velocity Structures of the <span class="hlt">Protostellar</span> Core B335</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kurono, Yasutaka; Saito, Masao; Kamazaki, Takeshi; Morita, Koh-Ichiro; Kawabe, Ryohei</p> <p>2013-03-01</p> <p>We present an observational study of the <span class="hlt">protostellar</span> core B335 harboring a <span class="hlt">low-mass</span> Class 0 source. The observations of the H13CO+(J = 1-0) line emission were carried out using the Nobeyama 45 m telescope and Nobeyama Millimeter Array. Our combined image of the interferometer and single-dish data depicts detailed structures of the dense envelope within the core. We found that the core has a radial density profile of n(r)vpropr -p and a reliable difference in the power-law indices between the outer and inner regions of the core: p ≈ 2 for r >~ 4000 AU and p ≈ 1.5 for r <~ 4000 AU. The dense core shows a slight overall velocity gradient of ~1.0 km s-1 over the scale of 20, 000 AU across the outflow axis. We believe that this velocity gradient represents a solid-body-like rotation of the core. The dense envelope has a quite symmetrical velocity structure with a remarkable line broadening toward the core center, which is especially prominent in the position-velocity diagram across the outflow axis. The model calculations of position-velocity diagrams do a good job of reproducing observational results using the collapse model of an isothermal sphere in which the core has an inner free-fall region and an outer region conserving the conditions at the formation stage of a central stellar object. We derived a central stellar mass of ~0.1 M ⊙, and suggest a small inward velocity, v_{r ≥ r_inf}˜ 0 km s^{-1} in the outer core at >~ 4000 AU. We concluded that our data can be well explained by gravitational collapse with a quasi-static initial condition, such as Shu's model, or by the isothermal collapse of a marginally critical Bonnor-Ebert sphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011IAUS..280E...8L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011IAUS..280E...8L&link_type=ABSTRACT"><span id="translatedtitle">Molecules in <span class="hlt">protostellar</span> shocks: the CHESS view on L1157-B1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lefloch, B.; Benedettini, M.; Cabrit, S.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Codella, C.; Giannini, T.; Nisini, B.; Parise, B.; Salez, M.; Vasta, M.; Viti, S.; CHESS Team</p> <p>2011-05-01</p> <p>Shocks driven by <span class="hlt">protostellar</span> outflows play an important role in the chemical evolution of molecular gas through temperature and density changes resulting from the activation of endothermic reactions, ionization, and dust destruction. These various processes lead to molecular abundance enhancements up to several orders of magnitude, as reported for various molecular species in "chemically active" outflows, whose archetype is the outflow of the <span class="hlt">low</span> <span class="hlt">mass</span> Class 0 protostar L1157. The opening up of the full far-infrared and submillimeter wavelength domains by Herschel has deep impact in the field by providing access to key spectral diagnostics of shock dynamics and chemistry at very high spectral resolution with HIFI and permitting to map the brightest features with the PACS and SPIRE multi-pixel spectrometers. We present the results of the spectral survey of the shock region L1157-B1 from 3.75mm up to 60 μm, carried out with the instruments onboard Herschel and with the IRAM 30m telescope, as part of the CHESS key project. The unprecedented sensitivity of these instruments brings new insight both on the molecular content and the physical conditions of this long studied region, thanks to the detection of hydrides (H2O, NH, HCl, ..) and of the high-excitation lines of heavy molecules (CO, CS, HCO+, HCN, ..). We will discuss the molecular content and the properties of the warm chemically enriched gas (abundance, excitation conditions). We will show how multi-transition analysis of the line profiles allows to constrain the shock physical conditions, the formation scenarios of various molecular species, including water, in relation with the predictions of MHD shock models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22092271','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22092271"><span id="translatedtitle"><span class="hlt">PROTOSTELLAR</span> ACCRETION FLOWS DESTABILIZED BY MAGNETIC FLUX REDISTRIBUTION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krasnopolsky, Ruben; Shang, Hsien; Li Zhiyun; Zhao Bo</p> <p>2012-09-20</p> <p>Magnetic flux redistribution lies at the heart of the problem of star formation in dense cores of molecular clouds that are magnetized to a realistic level. If all of the magnetic flux of a typical core were to be dragged into the central star, the stellar field strength would be orders of magnitude higher than the observed values. This well-known magnetic flux problem can in principle be resolved through non-ideal MHD effects. Two-dimensional (axisymmetric) calculations have shown that ambipolar diffusion, in particular, can transport magnetic flux outward relative to matter, allowing material to enter the central object without dragging the field lines along. We show through simulations that such axisymmetric <span class="hlt">protostellar</span> accretion flows are unstable in three dimensions to magnetic interchange instability in the azimuthal direction. The instability is driven by the magnetic flux redistributed from the matter that enters the central object. It typically starts to develop during the transition from the prestellar phase of star formation to the <span class="hlt">protostellar</span> mass accretion phase. In the latter phase, the magnetic flux is transported outward mainly through advection by strongly magnetized low-density regions that expand against the collapsing inflow. The tussle between the gravity-driven infall and magnetically driven expansion leads to a highly filamentary inner accretion flow that is more disordered than previously envisioned. The efficient outward transport of magnetic flux by advection lowers the field strength at small radii, making the magnetic braking less efficient and the formation of rotationally supported disks easier in principle. However, we find no evidence for such disks in any of our rotating collapse simulations. We conclude that the inner <span class="hlt">protostellar</span> accretion flow is shaped to a large extent by the flux redistribution-driven magnetic interchange instability. How disks form in such an environment is unclear.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApJ...757...77K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApJ...757...77K"><span id="translatedtitle"><span class="hlt">Protostellar</span> Accretion Flows Destabilized by Magnetic Flux Redistribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krasnopolsky, Ruben; Li, Zhi-Yun; Shang, Hsien; Zhao, Bo</p> <p>2012-09-01</p> <p>Magnetic flux redistribution lies at the heart of the problem of star formation in dense cores of molecular clouds that are magnetized to a realistic level. If all of the magnetic flux of a typical core were to be dragged into the central star, the stellar field strength would be orders of magnitude higher than the observed values. This well-known magnetic flux problem can in principle be resolved through non-ideal MHD effects. Two-dimensional (axisymmetric) calculations have shown that ambipolar diffusion, in particular, can transport magnetic flux outward relative to matter, allowing material to enter the central object without dragging the field lines along. We show through simulations that such axisymmetric <span class="hlt">protostellar</span> accretion flows are unstable in three dimensions to magnetic interchange instability in the azimuthal direction. The instability is driven by the magnetic flux redistributed from the matter that enters the central object. It typically starts to develop during the transition from the prestellar phase of star formation to the <span class="hlt">protostellar</span> mass accretion phase. In the latter phase, the magnetic flux is transported outward mainly through advection by strongly magnetized low-density regions that expand against the collapsing inflow. The tussle between the gravity-driven infall and magnetically driven expansion leads to a highly filamentary inner accretion flow that is more disordered than previously envisioned. The efficient outward transport of magnetic flux by advection lowers the field strength at small radii, making the magnetic braking less efficient and the formation of rotationally supported disks easier in principle. However, we find no evidence for such disks in any of our rotating collapse simulations. We conclude that the inner <span class="hlt">protostellar</span> accretion flow is shaped to a large extent by the flux redistribution-driven magnetic interchange instability. How disks form in such an environment is unclear.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950030905&hterms=astronomia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dastronomia','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950030905&hterms=astronomia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dastronomia"><span id="translatedtitle"><span class="hlt">Protostellar</span> collapse in a self-gravitating sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hartmann, Lee; Boss, Alan; Calvet, Nuria; Whitney, Barbara</p> <p>1994-01-01</p> <p>We present preliminary calculations of <span class="hlt">protostellar</span> cloud collapse starting from an isothermal, self-gravitating gaseous layer in hydrostatic equilibrium. This gravitationally unstable layer collapses into a flattened or toroidal density distribution, even in the absence of rotation or magnetic fields. We suggest that the flat infalling envelope recently observed in HL Tau by Hayashi et al.is the result of collapse from an initially nonspherical layer. We also speculate that the later evolution of such a flattened, collapsing envelope can produce a structure similar to the 'flared disk' invoked by Kenyon and Hartmann to explain the infrared excesses of many T Tauri stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22037286','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22037286"><span id="translatedtitle">THE ANATOMY OF THE YOUNG <span class="hlt">PROTOSTELLAR</span> OUTFLOW HH 211</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tappe, A.; Forbrich, J.; Lada, C. J.; Martin, S.; Yuan, Y.</p> <p>2012-05-20</p> <p>We present Spitzer Space Telescope 5-36 {mu}m mapping observations toward the southeastern lobe of the young <span class="hlt">protostellar</span> outflow HH 211. The southeastern terminal shock of the outflow shows a rich mid-infrared spectrum including molecular emission lines from OH, H{sub 2}O, HCO{sup +}, CO{sub 2}, H{sub 2}, and HD. The spectrum also shows a rising infrared continuum toward 5 {mu}m, which we interpret as unresolved emission lines from highly excited rotational levels of the CO v = 1-0 fundamental band. This interpretation is supported by a strong excess flux observed in the Spitzer/IRAC 4-5 {mu}m channel 2 image compared to the other IRAC channels. The extremely high critical densities of the CO v = 1-0 ro-vibrational lines and a comparison to H{sub 2} and CO excitation models suggest jet densities larger than 10{sup 6} cm{sup -3} in the terminal shock. We also observed the southeastern terminal outflow shock with the Submillimeter Array and detected pure rotational emission from CO 2-1, HCO{sup +} 3-2, and HCN 3-2. The rotationally excited CO traces the collimated outflow backbone as well as the terminal shock. HCN traces individual dense knots along the outflow and in the terminal shock, whereas HCO{sup +} solely appears in the terminal shock. The unique combination of our mid-infrared and submillimeter observations with previously published near-infrared observations allow us to study the interaction of one of the youngest known <span class="hlt">protostellar</span> outflows with its surrounding molecular cloud. Our results help us to understand the nature of some of the so-called green fuzzies (Extended Green Objects), and elucidate the physical conditions that cause high OH excitation and affect the chemical OH/H{sub 2}O balance in <span class="hlt">protostellar</span> outflows and young stellar objects. In an appendix to this paper, we summarize our Spitzer follow-up survey of <span class="hlt">protostellar</span> outflow shocks to find further examples of highly excited OH occurring together with H{sub 2}O and H{sub 2}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26156371','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26156371"><span id="translatedtitle">Feedback in <span class="hlt">low-mass</span> galaxies in the early Universe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Erb, Dawn K</p> <p>2015-07-01</p> <p>The formation, evolution and death of massive stars release large quantities of energy and momentum into the gas surrounding the sites of star formation. This process, generically termed 'feedback', inhibits further star formation either by removing gas from the galaxy, or by heating it to temperatures that are too high to form new stars. Observations reveal feedback in the form of galactic-scale outflows of gas in galaxies with high rates of star formation, especially in the early Universe. Feedback in faint, <span class="hlt">low-mass</span> galaxies probably facilitated the escape of ionizing radiation from galaxies when the Universe was about 500 million years old, so that the hydrogen between galaxies changed from neutral to ionized-the last major phase transition in the Universe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890049438&hterms=1587&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231587','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890049438&hterms=1587&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231587"><span id="translatedtitle">Dust discs around <span class="hlt">low-mass</span> main-sequence stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wolstencroft, R. D.; Walker, Helen J.</p> <p>1988-01-01</p> <p>The current understanding of the formation of circumstellar disks as a natural accompaniment to the process of <span class="hlt">low-mass</span> star formation is examined. Models of the thermal emission from the dust disks around the prototype stars Alpha Lyr, Alpha PsA, Beta Pic, and Epsilon Eri are discussed, which indicate that the central regions of three of these disks are almost devoid of dust within radii ranging between 17 and 26 AU, with the temperature of the hottest zone lying between about 115 and 210 K. One possible explanation of the dust-free zones is the presence of a planet at the inner boundary of each cloud which sweeps up grains crossing its orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JLTP..184..308A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JLTP..184..308A"><span id="translatedtitle">Optimizing Cryogenic Detectors for <span class="hlt">Low-Mass</span> WIMP Searches</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arnaud, Q.; Billard, J.; Juillard, A.</p> <p>2016-07-01</p> <p>This paper describes the methodology and results from a study dedicated to the optimization of cryogenic detectors for <span class="hlt">low-mass</span> WIMP searches. Considering a data-driven background model from the EDELWEISS-III experiment, and two analysis methods, namely profile likelihood and boosted decision tree, we indentify the main experimental constraints and performances that have to be improved. We found that there is a clear difference in how to optimize the detector setup whether focusing on WIMPs with masses below 5 GeV or above. Finally, in the case of a hundred-kg scale experiment, we discuss the requirements to probe most of the parameter space region delimited by the ultimate neutrino bound below 6 GeV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JLTP..184..866S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JLTP..184..866S"><span id="translatedtitle">Exploring <span class="hlt">Low-Mass</span> Dark Matter with CRESST</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strauss, R.; Angloher, G.; Bento, A.; Bucci, C.; Canonica, L.; Defay, X.; Erb, A.; Feilitzsch, F. v.; Ferreiro Iachellini, N.; Gorla, P.; Gütlein, A.; Hauff, D.; Jochum, J.; Kiefer, M.; Kluck, H.; Kraus, H.; Lanfranchi, J. C.; Loebell, J.; Münster, A.; Pagliarone, C.; Petricca, F.; Potzel, W.; Pröbst, F.; Reindl, F.; Schäffner, K.; Schieck, J.; Schönert, S.; Seidel, W.; Stodolsky, L.; Strandhagen, C.; Tanzke, A.; Trinh Thi, H. H.; Türkoglu, C.; Uffinger, M.; Ulrich, A.; Usherov, I.; Wawoczny, S.; Willers, M.; Wüstrich, M.; Zöller, A.</p> <p>2016-08-01</p> <p>The CRESST-II (Cryogenic Rare Event Search with Superconducting Thermometers) experiment, whose second phase has been successfully finished in summer 2015, aims at the direct detection of dark matter particles. The intrinsic radiopurity of CaWO_4 crystals, the capability to reject recoil events from alpha-surface contamination, and the energy threshold were significantly improved compared to previous runs of the experiment. A moderate exposure of 29 kg-days acquired by one ˜ 250 g CaWO_4 detector provides competitive limits on the spin-independent dark matter particle-nucleon cross section and probes a new region of parameter space for dark matter particle masses below 3 GeV/c^2. The potential for <span class="hlt">low-mass</span> dark matter particle search can be further exploited by a new detector design planned for CRESST-III. We describe the experimental strategy for the near future and give projections for the sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015MNRAS.453..408C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015MNRAS.453..408C&link_type=ABSTRACT"><span id="translatedtitle">Formation of elongated galaxies with <span class="hlt">low</span> <span class="hlt">masses</span> at high redshift</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ceverino, Daniel; Primack, Joel; Dekel, Avishai</p> <p>2015-10-01</p> <p>We report the identification of elongated (triaxial or prolate) galaxies in cosmological simulations at z ≃ 2. These are preferentially <span class="hlt">low-mass</span> galaxies (M* ≤ 109.5 M⊙), residing in dark matter (DM) haloes with strongly elongated inner parts, a common feature of high-redshift DM haloes in the Λ cold dark matter cosmology. Feedback slows formation of stars at the centres of these haloes, so that a dominant and prolate DM distribution gives rise to galaxies elongated along the DM major axis. As galaxies grow in stellar mass, stars dominate the total mass within the galaxy half-mass radius, making stars and DM rounder and more oblate. A large population of elongated galaxies produces a very asymmetric distribution of projected axis ratios, as observed in high-z galaxy surveys. This indicates that the majority of the galaxies at high redshifts are not discs or spheroids but rather galaxies with elongated morphologies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26156371','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26156371"><span id="translatedtitle">Feedback in <span class="hlt">low-mass</span> galaxies in the early Universe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Erb, Dawn K</p> <p>2015-07-01</p> <p>The formation, evolution and death of massive stars release large quantities of energy and momentum into the gas surrounding the sites of star formation. This process, generically termed 'feedback', inhibits further star formation either by removing gas from the galaxy, or by heating it to temperatures that are too high to form new stars. Observations reveal feedback in the form of galactic-scale outflows of gas in galaxies with high rates of star formation, especially in the early Universe. Feedback in faint, <span class="hlt">low-mass</span> galaxies probably facilitated the escape of ionizing radiation from galaxies when the Universe was about 500 million years old, so that the hydrogen between galaxies changed from neutral to ionized-the last major phase transition in the Universe. PMID:26156371</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.444.2525C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.444.2525C"><span id="translatedtitle">Improving PARSEC models for very <span class="hlt">low</span> <span class="hlt">mass</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Yang; Girardi, Léo; Bressan, Alessandro; Marigo, Paola; Barbieri, Mauro; Kong, Xu</p> <p>2014-11-01</p> <p>Many stellar models present difficulties in reproducing basic observational relations of very <span class="hlt">low</span> <span class="hlt">mass</span> stars (VLMS), including the mass-radius relation and the optical colour-magnitudes of cool dwarfs. Here, we improve PARSEC (PAdova-TRieste Stellar Evolution Code) models on these points. We implement the T- τ relations from PHOENIX BT-Settl model atmospheres as the outer boundary conditions in the PARSEC code, finding that this change alone reduces the discrepancy in the mass-radius relation from 8 to 5 per cent. We compare the models with multiband photometry of clusters Praesepe and M67, showing that the use of T- τ relations clearly improves the description of the optical colours and magnitudes. But anyway, using both Kurucz and PHOENIX model spectra, model colours are still systematically fainter and bluer than the observations. We then apply a shift to the above T- τ relations, increasing from 0 at Teff = 4730 K to ˜14 per cent at Teff = 3160 K, to reproduce the observed mass-radius relation of dwarf stars. Taking this experiment as a calibration of the T- τ relations, we can reproduce the optical and near-infrared colour-magnitude diagrams of <span class="hlt">low-mass</span> stars in the old metal-poor globular clusters NGC 6397 and 47 Tuc, and in the intermediate-age and young solar-metallicity open clusters M67 and Praesepe. Thus, we extend PARSEC models using this calibration, providing VLMS models more suitable for the lower main-sequence stars over a wide range of metallicities and wavelengths. Both sets of models are available on PARSEC webpage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...571A..45I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...571A..45I"><span id="translatedtitle">The formation of <span class="hlt">low-mass</span> helium white dwarfs orbiting pulsars . Evolution of <span class="hlt">low-mass</span> X-ray binaries below the bifurcation period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Istrate, A. G.; Tauris, T. M.; Langer, N.</p> <p>2014-11-01</p> <p>Context. Millisecond pulsars (MSPs) are generally believed to be old neutron stars (NSs) that have been spun up to high rotation rates via accretion of matter from a companion star in a <span class="hlt">low-mass</span> X-ray binary (LMXB). This scenario has been strongly supported by various pieces of observational evidence. However, many details of this recycling scenario remain to be understood. Aims: Here we investigate binary evolution in close LMXBs to study the formation of radio MSPs with <span class="hlt">low-mass</span> helium white dwarf companions (He WDs) in tight binaries with orbital periods Porb ≃ 2-9h. In particular, we examine i) if the observed <span class="hlt">systems</span> can be reproduced by theoretical modelling using standard prescriptions of orbital angular momentum losses (i.e. with respect to the nature and the strength of magnetic braking), ii) if our computations of the Roche-lobe detachments can match the observed orbital periods, and iii) if the correlation between WD mass and orbital period (MWD, Porb) is valid for <span class="hlt">systems</span> with Porb< 2 days. Methods: Numerical calculations with a detailed stellar evolution code were used to trace the mass-transfer phase in ~400 close LMXB <span class="hlt">systems</span> with different initial values of donor star mass, NS mass, orbital period, and the so-called γ-index of magnetic braking. Subsequently, we followed the orbital and the interior evolution of the detached <span class="hlt">low-mass</span> (proto) He WDs, including stages with residual shell hydrogen burning. Results: We find that severe fine-tuning is necessary to reproduce the observed MSPs in tight binaries with He WD companions of mass <0.20 M⊙, which suggests that something needs to be modified or is missing in the standard input physics of LMXB modelling. Results from previous independent studies support this conclusion. We demonstrate that the theoretically calculated (MWD, Porb)-relation is in general also valid for <span class="hlt">systems</span> with Porb< 2 days, although with a large scatter in He WD masses between 0.15-0.20 M⊙. The results of the thermal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.451.1460K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.451.1460K"><span id="translatedtitle">CFHTLenS: weak lensing calibrated scaling relations for <span class="hlt">low-mass</span> clusters of galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kettula, K.; Giodini, S.; van Uitert, E.; Hoekstra, H.; Finoguenov, A.; Lerchster, M.; Erben, T.; Heymans, C.; Hildebrandt, H.; Kitching, T. D.; Mahdavi, A.; Mellier, Y.; Miller, L.; Mirkazemi, M.; Van Waerbeke, L.; Coupon, J.; Egami, E.; Fu, L.; Hudson, M. J.; Kneib, J. P.; Kuijken, K.; McCracken, H. J.; Pereira, M. J.; Rowe, B.; Schrabback, T.; Tanaka, M.; Velander, M.</p> <p>2015-08-01</p> <p>We present weak lensing and X-ray analysis of 12 <span class="hlt">low-mass</span> clusters from the Canada-France-Hawaii Telescope Lensing Survey and XMM-CFHTLS surveys. We combine these <span class="hlt">systems</span> with high-mass <span class="hlt">systems</span> from Canadian Cluster Comparison Project and <span class="hlt">low-mass</span> <span class="hlt">systems</span> from Cosmic Evolution Survey to obtain a sample of 70 <span class="hlt">systems</span>, spanning over two orders of magnitude in mass. We measure core-excised LX-TX, M-LX and M-TX scaling relations and include corrections for observational biases. By providing fully bias-corrected relations, we give the current limitations for LX and TX as cluster mass proxies. We demonstrate that TX benefits from a significantly lower intrinsic scatter at fixed mass than LX. By studying the residuals of the bias-corrected relations, we show for the first time using weak lensing masses that galaxy groups seem more luminous and warmer for their mass than clusters. This implies a steepening of the M-LX and M-TX relations at <span class="hlt">low</span> <span class="hlt">masses</span>. We verify the inferred steepening using a different high-mass sample from the literature and show that variance between samples is the dominant effect leading to discrepant scaling relations. We divide our sample into subsamples of merging and relaxed <span class="hlt">systems</span>, and find that mergers may have enhanced scatter in lensing measurements, most likely due to stronger triaxiality and more substructure. For the LX-TX relation, which is unaffected by lensing measurements, we find the opposite trend in scatter. We also explore the effects of X-ray cross-calibration and find that Chandra calibration leads to flatter LX-TX and M-TX relations than XMM-Newton.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.444.1793D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.444.1793D"><span id="translatedtitle">The <span class="hlt">low-mass</span> star and sub-stellar populations of the 25 Orionis group</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Downes, Juan José; Briceño, César; Mateu, Cecilia; Hernández, Jesús; Vivas, Anna Katherina; Calvet, Nuria; Hartmann, Lee; Petr-Gotzens, Monika G.; Allen, Lori</p> <p>2014-10-01</p> <p>We present the results of a survey of the <span class="hlt">low-mass</span> star and brown dwarf population of the 25 Orionis group. Using optical photometry from the CIDA (Centro de Investigaciones de Astronomía `Francisco J. Duarte', Mérida, Venezuela) Deep Survey of Orion, near-IR photometry from the Visible and Infrared Survey Telescope for Astronomy and low-resolution spectroscopy obtained with Hectospec at the MMT telescope, we selected 1246 photometric candidates to <span class="hlt">low-mass</span> stars and brown dwarfs with estimated masses within 0.02 ≲ M/M⊙ ≲ 0.8 and spectroscopically confirmed a sample of 77 <span class="hlt">low-mass</span> stars as new members of the cluster with a mean age of ˜7 Myr. We have obtained a <span class="hlt">system</span> initial mass function of the group that can be well described by either a Kroupa power-law function with indices α3 = -1.73 ± 0.31 and α2 = 0.68 ± 0.41 in the mass ranges 0.03 ≤ M/M⊙ ≤ 0.08 and 0.08 ≤ M/M⊙ ≤ 0.5, respectively, or a Scalo lognormal function with coefficients m_c=0.21^{+0.02}_{-0.02} and σ = 0.36 ± 0.03 in the mass range 0.03 ≤ M/M⊙ ≤ 0.8. From the analysis of the spatial distribution of this numerous candidate sample, we have confirmed the east-west elongation of the 25 Orionis group observed in previous works, and rule out a possible southern extension of the group. We find that the spatial distributions of <span class="hlt">low-mass</span> stars and brown dwarfs in 25 Orionis are statistically indistinguishable. Finally, we found that the fraction of brown dwarfs showing IR excesses is higher than for <span class="hlt">low-mass</span> stars, supporting the scenario in which the evolution of circumstellar discs around the least massive objects could be more prolonged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015adap.prop..193W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015adap.prop..193W"><span id="translatedtitle"><span class="hlt">Low-Mass</span> Field Stars with Infrared Excesses: Potential Signatures of Planetary Collisions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>West, Andrew</p> <p></p> <p>This proposed study will investigate the occurrence of mid-infrared (MIR) excesses—found in WISE data—in <span class="hlt">low-mass</span> field stars. These MIR excesses are interpreted as dust reprocessed star-light, occurring when terrestrial planetary bodies collide. These <span class="hlt">systems</span> serve as an important signatures of terrestrial planet formation and evolution (or destruction). This proposal builds off the results of a pilot study (Theissen & West 2014) conducted using WISE, 2MASS, and SDSS observations. This study used MIR observations from WISE to identify 175 spectroscopically confirmed <span class="hlt">low-mass</span> stars exhibiting excess MIR flux over expected stellar photospheric levels. Theissen & West (2014) investigated other explanations for stars exhibiting excess MIR flux. Accounting for any possible contaminants, 175 stars were found with MIR excesses, and a low probability of MIR excesses being attributable to a contaminating source. Through investigation of the disk luminosities and approximate stellar ages estimated from spectroscopic tracers, it was determined the most likely cause of the excess MIR flux is a large abundance of circumstellar material, likely caused by collisions between planetary bodies. The pilot study was limited by its small sample size (175 stars) and incompleteness due to the SDSS spectroscopic target selection. Our proposed study will use a photometrically selected sample to create a more complete and statistically significant sample of <span class="hlt">low-mass</span> stars exhibiting MIR excesses. The first objective of this proposal will be to construct a photometric catalog of <span class="hlt">low-mass</span> stars, combining WISE, 2MASS, and SDSS photometry. To differentiate stars from other point-like sources of similar color (e.g. red galaxies), we will use proper motions. The large time baselines between WISE, 2MASS, and SDSS observations (~9-12 years) allow us to compute reliable proper motions for millions of photometric <span class="hlt">low-mass</span> stars contained within the combined WISE+2MASS+SDSS dataset (estimated to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25324383','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25324383"><span id="translatedtitle">Laboratory formation of a scaled <span class="hlt">protostellar</span> jet by coaligned poloidal magnetic field.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Albertazzi, B; Ciardi, A; Nakatsutsumi, M; Vinci, T; Béard, J; Bonito, R; Billette, J; Borghesi, M; Burkley, Z; Chen, S N; Cowan, T E; Herrmannsdörfer, T; Higginson, D P; Kroll, F; Pikuz, S A; Naughton, K; Romagnani, L; Riconda, C; Revet, G; Riquier, R; Schlenvoigt, H-P; Skobelev, I Yu; Faenov, A Ya; Soloviev, A; Huarte-Espinosa, M; Frank, A; Portugall, O; Pépin, H; Fuchs, J</p> <p>2014-10-17</p> <p>Although bipolar jets are seen emerging from a wide variety of astrophysical <span class="hlt">systems</span>, the issue of their formation and morphology beyond their launching is still under study. Our scaled laboratory experiments, representative of young stellar object outflows, reveal that stable and narrow collimation of the entire flow can result from the presence of a poloidal magnetic field whose strength is consistent with observations. The laboratory plasma becomes focused with an interior cavity. This gives rise to a standing conical shock from which the jet emerges. Following simulations of the process at the full astrophysical scale, we conclude that it can also explain recently discovered x-ray emission features observed in low-density regions at the base of <span class="hlt">protostellar</span> jets, such as the well-studied jet HH 154. PMID:25324383</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25324383','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25324383"><span id="translatedtitle">Laboratory formation of a scaled <span class="hlt">protostellar</span> jet by coaligned poloidal magnetic field.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Albertazzi, B; Ciardi, A; Nakatsutsumi, M; Vinci, T; Béard, J; Bonito, R; Billette, J; Borghesi, M; Burkley, Z; Chen, S N; Cowan, T E; Herrmannsdörfer, T; Higginson, D P; Kroll, F; Pikuz, S A; Naughton, K; Romagnani, L; Riconda, C; Revet, G; Riquier, R; Schlenvoigt, H-P; Skobelev, I Yu; Faenov, A Ya; Soloviev, A; Huarte-Espinosa, M; Frank, A; Portugall, O; Pépin, H; Fuchs, J</p> <p>2014-10-17</p> <p>Although bipolar jets are seen emerging from a wide variety of astrophysical <span class="hlt">systems</span>, the issue of their formation and morphology beyond their launching is still under study. Our scaled laboratory experiments, representative of young stellar object outflows, reveal that stable and narrow collimation of the entire flow can result from the presence of a poloidal magnetic field whose strength is consistent with observations. The laboratory plasma becomes focused with an interior cavity. This gives rise to a standing conical shock from which the jet emerges. Following simulations of the process at the full astrophysical scale, we conclude that it can also explain recently discovered x-ray emission features observed in low-density regions at the base of <span class="hlt">protostellar</span> jets, such as the well-studied jet HH 154.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20120013634&hterms=organic+chemistry&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2528organic%2Bchemistry%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20120013634&hterms=organic+chemistry&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2528organic%2Bchemistry%2529"><span id="translatedtitle">Organic Chemistry of <span class="hlt">Low-Mass</span> Star-Forming Cores. I. 7 mm Spectroscopy of Chamaeleon MMSl</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cordiner, Martn A.; Charnley, Steven B.; Wirtstroem, Eva S.; Smith, Robert G.</p> <p>2012-01-01</p> <p>Observations are presented of emission lines from organic molecules at frequencies 32-50 GHz in the vicinity of Chamaeleon MMS1. This chemically rich dense cloud core harbors an extremely young, very low luminosity <span class="hlt">protostellar</span> object and is a candidate first hydrostatic core. Column densities are derived and emission maps are presented for species including polyynes, cyanopolyynes, sulphuretted carbon chains, and methanol. The polyyne emission peak lies about 5000 AU from the protostar, whereas methanol peaks about 15,000 AU away. Averaged over the telescope beam, the molecular hydrogen number density is calculated to be 10(exp 6) / cubic cm and the gas kinetic temperature is in the range 5-7 K. The abundances of long carbon chains are very large and are indicative of a nonequilibrium carbon chemistry; C6H and HC7N column densities are 5.9(sup +2.9) (sub -1.3) x 10(exp 11) /cubic cm and 3.3 (sup +8.0)(sub -1.5) x 10(exp 12)/sq cm, respectively, which are similar to the values found in the most carbon-chain-rich protostars and prestellar cores known, and are unusually large for star-forming gas. Column density upper limits were obtained for the carbon chain anions C4H(-) and C6H(-), with anion-to-neutral ratios [C4H(-)]/[C4H] < 0.02% and [C6H(-l)]/[C6H] < 10%, consistent with previous observations in interstellar clouds and <span class="hlt">low-mass</span> protostars. Deuterated HC,3 and c-C3H2 were detected. The [DC3N]/[HC,N] ratio of approximately 4% is consistent with the value typically found in cold interstellar gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040112455&hterms=organic+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528organic%2Bchemistry%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040112455&hterms=organic+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528organic%2Bchemistry%2529"><span id="translatedtitle">Spectroscopic diagnostics of organic chemistry in the <span class="hlt">protostellar</span> environment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Charnley, S. B.; Ehrenfreund, P.; Kuan, Y. J.</p> <p>2001-01-01</p> <p>A combination of astronomical observations, laboratory studies, and theoretical modelling is necessary to determine the organic chemistry of dense molecular clouds. We present spectroscopic evidence for the composition and evolution of organic molecules in <span class="hlt">protostellar</span> environments. The principal reaction pathways to complex molecule formation by catalysis on dust grains and by reactions in the interstellar gas are described. <span class="hlt">Protostellar</span> cores, where warming of dust has induced evaporation of icy grain mantles, are excellent sites in which to study the interaction between gas phase and grain-surface chemistries. We investigate the link between organics that are observed as direct products of grain surface reactions and those which are formed by secondary gas phase reactions of evaporated surface products. Theory predicts observable correlations between specific interstellar molecules, and also which new organics are viable for detection. We discuss recent infrared observations obtained with the Infrared Space Observatory, laboratory studies of organic molecules, theories of molecule formation, and summarise recent radioastronomical searches for various complex molecules such as ethers, azaheterocyclic compounds, and amino acids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22048068','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22048068"><span id="translatedtitle"><span class="hlt">PROTOSTELLAR</span> OUTFLOW HEATING IN A GROWING MASSIVE PROTOCLUSTER</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang Ke; Wu Yuefang; Zhang Huawei; Zhang Qizhou; Li Huabai</p> <p>2012-02-15</p> <p>The dense molecular clump P1 in the infrared dark cloud complex G28.34+0.06 harbors a massive <span class="hlt">protostellar</span> cluster at its extreme youth. Our previous Submillimeter Array observations revealed several jet-like CO outflows emanating from the protostars, indicative of intense accretion and potential interaction with ambient natal materials. Here, we present the Expanded Very Large Array spectral line observations toward P1 in the NH{sub 3} (J,K) = (1,1), (2,2), (3,3) lines, as well as H{sub 2}O and class I CH{sub 3}OH masers. Multiple NH{sub 3} transitions reveal the heated gas widely spread in the 1 pc clump. The temperature distribution is highly structured; the heated gas is offset from the protostars, and morphologically matches the outflows very well. Hot spots of spatially compact, spectrally broad NH{sub 3} (3,3) emission features are also found coincident with the outflows. A weak NH{sub 3} (3,3) maser is discovered at the interface between an outflow jet and the ambient gas. These findings suggest that <span class="hlt">protostellar</span> heating may not be effective in suppressing fragmentation during the formation of massive cores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930057629&hterms=off+grid+solar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Doff%2Bgrid%252C%2Bsolar','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930057629&hterms=off+grid+solar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Doff%2Bgrid%252C%2Bsolar"><span id="translatedtitle">The formation of <span class="hlt">protostellar</span> disks. I - 1 M(solar)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yorke, Harold W.; Bodenheimer, Peter; Laughlin, Gregory</p> <p>1993-01-01</p> <p>Hydrodynamical calculations of the collapse of an axisymmetric, rotating one solar mass <span class="hlt">protostellar</span> cloud, including the effects of radiative transfer and radiative acceleration but without magnetic fields, are presented. The results include calculations of infrared <span class="hlt">protostellar</span> spectra as a function of time and viewing angle. A numerical algorithm involving explicit nested grids is used to resolve the region of initial disk formation and at the same time to include the outer regions in the calculation. The central part of the protostar is modeled approximately. Initial conditions are systematically varied to investigate their influence on the evolution and final configuration of central star plus circumstellar disk. The initial state for the standard case is a centrally condensed molecular cloud core of one solar mass with a mean density of 8 x 10 exp -18 g/cu cm and a specific angular momentum at the outer edge of 7 x 10 exp 20 sq cm/s. The collapse is followed for 8 x 10 exp 4 yr, at which point 0.45 solar mass is contained in a rapidly rotating central object and most of the remainder in a surrounding equilibrium disk. The stability of this final structure is qualitatively analyzed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11345247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11345247"><span id="translatedtitle">Spectroscopic diagnostics of organic chemistry in the <span class="hlt">protostellar</span> environment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Charnley, S B; Ehrenfreund, P; Kuan, Y J</p> <p>2001-03-15</p> <p>A combination of astronomical observations, laboratory studies, and theoretical modelling is necessary to determine the organic chemistry of dense molecular clouds. We present spectroscopic evidence for the composition and evolution of organic molecules in <span class="hlt">protostellar</span> environments. The principal reaction pathways to complex molecule formation by catalysis on dust grains and by reactions in the interstellar gas are described. <span class="hlt">Protostellar</span> cores, where warming of dust has induced evaporation of icy grain mantles, are excellent sites in which to study the interaction between gas phase and grain-surface chemistries. We investigate the link between organics that are observed as direct products of grain surface reactions and those which are formed by secondary gas phase reactions of evaporated surface products. Theory predicts observable correlations between specific interstellar molecules, and also which new organics are viable for detection. We discuss recent infrared observations obtained with the Infrared Space Observatory, laboratory studies of organic molecules, theories of molecule formation, and summarise recent radioastronomical searches for various complex molecules such as ethers, azaheterocyclic compounds, and amino acids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22356960','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22356960"><span id="translatedtitle">Radiation magnetohydrodynamic simulations of <span class="hlt">protostellar</span> collapse: Low-metallicity environments</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tomida, Kengo</p> <p>2014-05-10</p> <p>Among many physical processes involved in star formation, radiation transfer is one of the key processes because it dominantly controls the thermodynamics. Because metallicities control opacities, they are one of the important environmental parameters that affect star formation processes. In this work, I investigate <span class="hlt">protostellar</span> collapse in solar-metallicity and low-metallicity (Z = 0.1 Z {sub ☉}) environments using three-dimensional radiation hydrodynamic and magnetohydrodynamic simulations. Because radiation cooling in high-density gas is more effective in low-metallicity environments, first cores are colder and have lower entropies. As a result, first cores are smaller, less massive, and have shorter lifetimes in low-metallicity clouds. Therefore, first cores would be less likely to be found in low-metallicity star forming clouds. This also implies that first cores tend to be more gravitationally unstable and susceptible to fragmentation. The evolution and structure of <span class="hlt">protostellar</span> cores formed after the second collapse weakly depend on metallicities in the spherical and magnetized models, despite the large difference in the metallicities. Because this is due to the change of the heat capacity by dissociation and ionization of hydrogen, it is a general consequence of the second collapse as long as the effects of radiation cooling are not very large during the second collapse. On the other hand, the effects of different metallicities are more significant in the rotating models without magnetic fields, because they evolve slower than other models and therefore are more affected by radiation cooling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.441.1825B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.441.1825B"><span id="translatedtitle">A state change in the <span class="hlt">low-mass</span> X-ray binary XSS J12270-4859</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bassa, C. G.; Patruno, A.; Hessels, J. W. T.; Keane, E. F.; Monard, B.; Mahony, E. K.; Bogdanov, S.; Corbel, S.; Edwards, P. G.; Archibald, A. M.; Janssen, G. H.; Stappers, B. W.; Tendulkar, S.</p> <p>2014-06-01</p> <p>Millisecond radio pulsars acquire their rapid rotation rates through mass and angular momentum transfer in a <span class="hlt">low-mass</span> X-ray binary <span class="hlt">system</span>. Recent studies of PSR J1824-2452I and PSR J1023+0038 have observationally demonstrated this link, and they have also shown that such <span class="hlt">systems</span> can repeatedly transition back-and-forth between the radio millisecond pulsar and <span class="hlt">low-mass</span> X-ray binary states. This also suggests that a fraction of such <span class="hlt">systems</span> are not newly born radio millisecond pulsars but are rather suspended in a back-and-forth, state-switching phase, perhaps for gigayears. XSS J12270-4859 has been previously suggested to be a <span class="hlt">low-mass</span> X-ray binary, and until recently the only such <span class="hlt">system</span> to be seen at MeV-GeV energies. We present radio, optical and X-ray observations that offer compelling evidence that XSS J12270-4859 is a <span class="hlt">low-mass</span> X-ray binary which transitioned to a radio millisecond pulsar state between 2012 November 14 and December 21. We use optical and X-ray photometry/spectroscopy to show that the <span class="hlt">system</span> has undergone a sudden dimming and no longer shows evidence for an accretion disc. The optical observations constrain the orbital period to 6.913 ± 0.002 h.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...830..153J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...830..153J"><span id="translatedtitle">Evolution of <span class="hlt">Low-mass</span> X-Ray Binaries: The Effect of Donor Evaporation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jia, Kun; Li, Xiang-Dong</p> <p>2016-10-01</p> <p>Millisecond pulsars (MSPs) are thought to originate from <span class="hlt">low-mass</span> X-ray binaries (LMXBs). The discovery of eclipsing radio MSPs, including redbacks and black widows, indicates that evaporation of the donor star by the MSP’s irradiation takes place during the LMXB evolution. In this work, we investigate the effect of donor evaporation on the secular evolution of LMXBs, considering different evaporation efficiencies and related angular momentum loss. We find that for widening LMXBs, the donor star leaves a less massive white dwarf than without evaporation; for contracting <span class="hlt">systems</span>, evaporation can speed up the evolution, resulting in dynamically unstable mass transfer and possibly the formation of isolated MSPs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5147813','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5147813"><span id="translatedtitle">Neutron star formation in theoretical supernovae. <span class="hlt">Low</span> <span class="hlt">mass</span> stars and white dwarfs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nomoto, K.</p> <p>1986-01-01</p> <p>The presupernova evolution of stars that form semi-degenerate or strongly degenerate O + Ne + Mg cores is discussed. For the 10 to 13 Msub solar stars, behavior of off-center neon flashes is crucial. The 8 to 10 m/sub solar stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these <span class="hlt">low</span> <span class="hlt">mass</span> progenitors are compared with the Crab nebula. The conditions for which neutron stars form from accretion-induced collapse of white dwarfs in clsoe binary <span class="hlt">systems</span> is also examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22518749','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22518749"><span id="translatedtitle">LEO P: AN UNQUENCHED VERY <span class="hlt">LOW-MASS</span> GALAXY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle; Dolphin, Andrew; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P.; Girardi, Léo</p> <p>2015-10-20</p> <p>Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ∼0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M{sub ⊙}. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ∼10{sup −5} M{sub ⊙} yr{sup −1}. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a <span class="hlt">low-mass</span> dSph would look like if it evolved in isolation and retained its gas. Despite the very <span class="hlt">low</span> <span class="hlt">mass</span> of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...812..158M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...812..158M"><span id="translatedtitle">Leo P: An Unquenched Very <span class="hlt">Low-mass</span> Galaxy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McQuinn, Kristen B. W.; Skillman, Evan D.; Dolphin, Andrew; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Berg, Danielle; Giovanelli, Riccardo; Girardi, Léo; Haynes, Martha P.</p> <p>2015-10-01</p> <p>Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ˜0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M⊙. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ˜10-5 M⊙ yr-1. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a <span class="hlt">low-mass</span> dSph would look like if it evolved in isolation and retained its gas. Despite the very <span class="hlt">low</span> <span class="hlt">mass</span> of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites. Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22713601T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22713601T"><span id="translatedtitle">SHIELD: The Star Formation Law in Extremely <span class="hlt">Low-mass</span> Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Teich, Yaron; McNichols, Andrew; Cannon, John M.; SHIELD Team</p> <p>2016-01-01</p> <p>The "Survey of HI in Extremely <span class="hlt">Low-mass</span> Dwarfs" (SHIELD) is a multiwavelength, legacy-class observational study of 12 <span class="hlt">low-mass</span> dwarf galaxies discovered in Arecibo Legacy Fast ALFA (ALFALFA) survey data products. Here we analyze the relationships between HI and star formation in these <span class="hlt">systems</span> using multi-configuration, high spatial (~300 pc) and spectral (0.82 - 2.46 km s-1 ch-1) resolution HI observations from the Karl G. Jansky Very Large Array, Hα imaging from the WIYN 3.5m telescope, and archival GALEX far-ultraviolet imaging. We compare the locations and intensities of star formation with the properties of the neutral ISM. We quantify the degree of local co-spatiality between star forming regions and regions of high HI column densities using the Kennicutt-Schmidt (K-S) relation. The values of the K-S index N vary considerably from <span class="hlt">system</span> to <span class="hlt">system</span>; because no single galaxy is representative of the sample, we instead focus on the narratives of the individual galaxies and their complex distribution of gaseous and stellar components. At the extremely faint end of the HI mass function, these <span class="hlt">systems</span> are dominated by stochastic fluctuations in their interstellar media, which governs whether or not they show signs of recent star formation.Support for this work was provided by NSF grant AST-1211683 to JMC at Macalester College.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...565A..64P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...565A..64P"><span id="translatedtitle">Molecular ions in the <span class="hlt">protostellar</span> shock L1157-B1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Podio, L.; Lefloch, B.; Ceccarelli, C.; Codella, C.; Bachiller, R.</p> <p>2014-05-01</p> <p>Aims: We perform a complete census of molecular ions with an abundance greater than ~10-10 in the <span class="hlt">protostellar</span> shock L1157-B1. This allows us to study the ionisation structure and chemistry of the shock. Methods: An unbiased high-sensitivity survey of L1157-B1 performed with the IRAM-30 m and Herschel/HIFI as part of the CHESS and ASAI large programmes allows searching for molecular ions emission. Then, by means of a radiative transfer code in the large velocity gradient approximation, the gas physical conditions and fractional abundances of molecular ions are derived. The latter are compared with estimates of steady-state abundances in the cloud and their evolution in the shock calculated with the chemical model Astrochem. Results: We detect emission from HCO+, H13CO+, N2H+, HCS+, and for the first time in a shock, from HOCO+ and SO+. The bulk of the emission peaks at blue-shifted velocity, ~0.5-3 km s -1 with respect to <span class="hlt">systemic</span>, has a width of ~3-7 km s-1 and is associated with the outflow cavities (Tkin ~ 20-70 K, nH2 ~ 105 cm-3). A high-velocity component up to -40 km s-1, associated with the primary jet, is detected in the HCO+ 1-0 line. Observed HCO+ and N2H+ abundances (XHCO+ ~ 0.7-3 × 10-8, XN2H+ ~ 0.4-8 × 10-9) agree with steady-state abundances in the cloud and with their evolution in the compressed and heated gas in the shock for cosmic rays ionisation rate ζ = 3 × 10-16 s-1. HOCO+, SO+, and HCS+ observed abundances (XHOCO+ ~ 10-9, XSO+ ~ 8 × 10-10, XHCS+ ~ 3-7 × 10-10), instead, are 1-2 orders of magnitude larger than predicted in the cloud; on the other hand, they are strongly enhanced on timescales shorter than the shock age (~2000 years) if CO2, S or H2S, and OCS are sputtered off the dust grains in the shock. Conclusions: The performed analysis indicates that HCO+ and N2H+ are a fossil record of pre-shock gas in the outflow cavity, whilst HOCO+, SO+, and HCS+ are effective shock tracers that can be used to infer the amount of CO2 and sulphur</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.453.3720B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.453.3720B"><span id="translatedtitle"><span class="hlt">Protostellar</span> spin-down: a planetary lift?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bouvier, J.; Cébron, D.</p> <p>2015-11-01</p> <p>When they first appear in the HR diagram, young stars rotate at a mere 10 per cent of their break-up velocity. They must have lost most of the angular momentum initially contained in the parental cloud, the so-called angular momentum problem. We investigate here a new mechanism by which large amounts of angular momentum might be shed from young stellar <span class="hlt">systems</span>, thus yielding slowly rotating young stars. Assuming that planets promptly form in circumstellar discs and rapidly migrate close to the central star, we investigate how the tidal and magnetic interactions between the protostar, its close-in planet(s), and the inner circumstellar disc can efficiently remove angular momentum from the central object. We find that neither the tidal torque nor the variety of magnetic torques acting between the star and the embedded planet are able to counteract the spin-up torques due to accretion and contraction. Indeed, the former are orders of magnitude weaker than the latter beyond the corotation radius and are thus unable to prevent the young star from spinning up. We conclude that star-planet interaction in the early phases of stellar evolution does not appear as a viable alternative to magnetic star-disc coupling to understand the origin of the low angular momentum content of young stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014xru..confE.227B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014xru..confE.227B"><span id="translatedtitle">A Unified Model of <span class="hlt">Low</span> <span class="hlt">Mass</span> X-ray Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balucinska-Church, M.; Church, M.</p> <p>2014-07-01</p> <p>We present a unified physical model of <span class="hlt">Low</span> <span class="hlt">Mass</span> X-ray Binaries explaining the basic Atoll and Z-track types of source. In all LMXB with luminosity above 1-2.10^{37} erg/s, we have a new fundamental result that the temperature of the Comptonizing ADC corona equals that of the neutron star, i.e. there is thermal equilibrium. This equilibrium explains the properties of the basic Banana State of Atoll sources. Below this luminosity, equilibrium breaks down, T_ADC rising towards 100 keV by an unknown heating mechanism, explaining the Island State. Above 5.10^{37} erg/s flaring begins in the GX-Atolls which we show is unstable nuclear burning. Above 1.10^{38} erg/s, LMXB are seen as Z-track sources. Flaring in these and the GX-Atolls occurs when the mass accretion rate to the neutron star falls to the critical value for unstable nuclear burning on the star. Below 2.10^{37} erg/s, a different unstable burning: X-ray bursting, takes over. We show that the Normal Branch of the Z-track consists simply of increasing mass accretion rate, as is the Banana State in Atolls. In the Horizontal Branch, a measured, strongly increasing radiation pressure of the neutron star disrupts the inner disk launching the relativistic jets seen on this branch.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000A%26A...360..935M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000A%26A...360..935M"><span id="translatedtitle">Structure and evolution of <span class="hlt">low-mass</span> Population II stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montalbán, J.; D'Antona, F.; Mazzitelli, I.</p> <p>2000-08-01</p> <p>The focus of the present paper is on the detailed description of the internal structures of <span class="hlt">low</span> <span class="hlt">mass</span>, population II stars, to clarify some issues about these stellar models and, mainly, their present reliability for observational comparisons. We then explore 1) the role of the local convective model; 2) the differences between "grey" and "non grey" models, and between models in which the photospheric boundary conditions are set at different optical depths (τph = 3 or 100); 3) the role of the equation of state (EoS), both in the atmospheric models and in the interior. One of the major conclusions of the paper is a cautionary note about the usage of the additive volume law in EoS calculations. The dependence of the HR diagram locations and mass luminosity relations on metal and helium content are also discussed. A few comparisons with globular cluster stars show that: 1) general consistency of distance scales and morphologies in the HR diagram is found, when comparing ground based measurements in the Johnson B and V bands and observations in the HST bands; 2) a discrepancy between models and observations may exist for more metal rich clusters; 3) the plausible hypothesis that the mass function in the globular cluster NGC 6397 behaves smoothly until the lower limit of the main sequence poses constraints on the mass-luminosity relation at the lowest end of the main sequence. The evolutionary tracks are available at the WEB location http://www.mporzio.astro.it.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22711002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22711002S"><span id="translatedtitle">Formation and Asteroseismology of Extremely <span class="hlt">Low-mass</span> White Dwarfs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Meng; Arras, Phil</p> <p>2016-01-01</p> <p>A handful of extremely <span class="hlt">low-mass</span> white dwarfs (ELM WD, M<0.2M⊙) have been discovered recently to exhibit g-mode pulsations, extending the classic DA instability strip to much smaller mass. One particular ELM WD (SDSS J111215.82+111745.0) has been observed to pulsate at periods so short that the pulsations may be p-modes, making this star unique among all WD pulsators. Since the ELM WDs are thought to be formed only through binary, and not single star evolution, the observed periods give the opportunity to constrain the interiors of these post-common-envelope or post-Roche-lobe-overflow WD through asteroseismology. I will discuss our recent efforts to construct models of these these ELM WD pulsators using the MESA stellar evolution code to carry out binary evolution. The relative size of the solar-composition envelope to helium core is expected to vary significantly with stellar mass and orbital period. This variation in structure is reflected in the oscillation mode periods for the models. Lastly, I will discuss constraints on the interior structure of J1112 from seismology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvD..94d2001M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvD..94d2001M"><span id="translatedtitle">3D lumped LC resonators as <span class="hlt">low</span> <span class="hlt">mass</span> axion haloscopes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McAllister, Ben T.; Parker, Stephen R.; Tobar, Michael E.</p> <p>2016-08-01</p> <p>The axion is a hypothetical particle considered to be the most economical solution to the strong C P problem. It can also be formulated as a compelling component of dark matter. The haloscope, a leading axion detection scheme, relies on the conversion of galactic halo axions into real photons inside a resonant cavity structure in the presence of a static magnetic field, where the generated photon frequency corresponds to the mass of the axion. For maximum sensitivity it is key that the central frequency of the cavity mode structure coincides with the frequency of the generated photon. As the mass of the axion is unknown, it is necessary to perform searches over a wide range of frequencies. Currently there are substantial regions of the promising preinflationary <span class="hlt">low-mass</span> axion range without any viable proposals for experimental searches. We show that three-dimensional resonant LC circuits with separated magnetic and electric fields, commonly known as reentrant cavities, can be sensitive dark matter haloscopes in this region, with frequencies inherently lower than those achievable in the equivalent size of empty resonant cavity. We calculate the sensitivity and accessible axion mass range of these experiments, designing geometries to exploit and maximize the separated magnetic and electric coupling of the axion to the cavity mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010noao.prop..148S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010noao.prop..148S"><span id="translatedtitle"><span class="hlt">Low</span> <span class="hlt">Mass</span> Members in Nearby Young Moving Groups Revealed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlieder, Joshua; Simon, Michal; Rice, Emily; Lepine, Sebastien</p> <p>2010-08-01</p> <p>We are now ready to expand our program that identifies highly probable <span class="hlt">low-mass</span> members of the nearby young moving groups (NYMGs) to stars of mass ~ 0.1 Msun. This is important 1) To provide high priority targets for exoplanet searches by direct imaging, 2) To complete the census of the membership in the NYMGs, and 3) To provide a well-characterized sample of nearby young stars for detailed study of their physical properties and multiplicity (the median distances of the (beta) Pic and AB Dor groups are ~ 35 pc with ages ~ 12 and 50 Myr respectively). Our proven technique starts with a proper motion selection algorithm, proceeds to vet the sample for indicators of youth, and requires as its last step the measurement of candidate member radial velocities (RVs). So far, we have obtained all RV measurements with the high resolution IR spectrometer at the NASA-IRTF and have reached the limits of its applicability. To identify probable new members in the south, and also those of the lowest mass, we need the sensitivity of PHOENIX at Gemini-S and NIRSPEC at Keck-II.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Ap%26SS.361..248M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Ap%26SS.361..248M"><span id="translatedtitle">Characterising the physical and chemical properties of a young Class 0 <span class="hlt">protostellar</span> core embedded in the Orion B9 filament</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miettinen, O.</p> <p>2016-08-01</p> <p>Deeply embedded <span class="hlt">low-mass</span> protostars can be used as testbeds to study the early formation stages of solar-type stars, and the prevailing chemistry before the formation of a planetary <span class="hlt">system</span>. The present study aims to characterise further the physical and chemical properties of the <span class="hlt">protostellar</span> core Orion B9-SMM3. The Atacama Pathfinder EXperiment (APEX) telescope was used to perform a follow-up molecular line survey of SMM3. The observations were done using the single pointing (frequency range 218.2-222.2 GHz) and on-the-fly mapping methods (215.1-219.1 GHz). These new data were used in conjunction with our previous data taken by the APEX and Effelsberg 100 m telescopes. The following species were identified from the frequency range 218.2-222.2 GHz: ^{13}CO, C^{18}O, SO, para-H2CO, and E1-type CH3OH. The mapping observations revealed that SMM3 is associated with a dense gas core as traced by DCO+ and p-H2CO. Altogether three different p-H2CO transitions were detected with clearly broadened linewidths (Δ v˜8.2-11 km s^{-1} in FWHM). The derived p-H2CO rotational temperature, 64±15 K, indicates the presence of warm gas. We also detected a narrow p-H2CO line (Δ v=0.42 km s^{-1}) at the <span class="hlt">systemic</span> velocity. The p-H2CO abundance for the broad component appears to be enhanced by two orders of magnitude with respect to the narrow line value ({˜}3×10^{-9} versus {˜}2×10^{-11}). The detected methanol line shows a linewidth similar to those of the broad p-H2CO lines, which indicates their coexistence. The CO isotopologue data suggest that the CO depletion factor decreases from {˜}27±2 towards the core centre to a value of {˜}8±1 towards the core edge. In the latter position, the N2D+/N2H+ ratio is revised down to 0.14±0.06. The origin of the subfragments inside the SMM3 core we found previously can be understood in terms of the Jeans instability if non-thermal motions are taken into account. The estimated fragmentation timescale, and the derived chemical abundances</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AJ....146...65J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AJ....146...65J"><span id="translatedtitle">Very <span class="hlt">Low</span> <span class="hlt">Mass</span> Stellar and Substellar Companions to Solar-like Stars from MARVELS. IV. A Candidate Brown Dwarf or <span class="hlt">Low-mass</span> Stellar Companion to HIP 67526</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Peng; Ge, Jian; Cargile, Phillip; Crepp, Justin R.; De Lee, Nathan; Porto de Mello, Gustavo F.; Esposito, Massimiliano; Ferreira, Letícia D.; Femenia, Bruno; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; González Hernández, Jonay I.; Hebb, Leslie; Lee, Brian L.; Ma, Bo; Stassun, Keivan G.; Wang, Ji; Wisniewski, John P.; Agol, Eric; Bizyaev, Dmitry; Brewington, Howard; Chang, Liang; Nicolaci da Costa, Luiz; Eastman, Jason D.; Ebelke, Garrett; Gary, Bruce; Kane, Stephen R.; Li, Rui; Liu, Jian; Mahadevan, Suvrath; Maia, Marcio A. G.; Malanushenko, Viktor; Malanushenko, Elena; Muna, Demitri; Nguyen, Duy Cuong; Ogando, Ricardo L. C.; Oravetz, Audrey; Oravetz, Daniel; Pan, Kaike; Pepper, Joshua; Paegert, Martin; Allende Prieto, Carlos; Rebolo, Rafael; Santiago, Basilio X.; Schneider, Donald P.; Shelden Bradley, Alaina C.; Sivarani, Thirupathi; Snedden, Stephanie; van Eyken, J. C.; Wan, Xiaoke; Weaver, Benjamin A.; Zhao, Bo</p> <p>2013-09-01</p> <p>We report the discovery of a candidate brown dwarf (BD) or a very <span class="hlt">low</span> <span class="hlt">mass</span> stellar companion (MARVELS-5b) to the star HIP 67526 from the Multi-object Apache point observatory Radial Velocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for this object contains 31 epochs spread over 2.5 yr. Our Keplerian fit, using a Markov Chain Monte Carlo approach, reveals that the companion has an orbital period of 90.2695^{+0.0188}_{-0.0187} days, an eccentricity of 0.4375 ± 0.0040, and a semi-amplitude of 2948.14^{+16.65}_{-16.55} m s-1. Using additional high-resolution spectroscopy, we find the host star has an effective temperature T eff = 6004 ± 34 K, a surface gravity log g (cgs) =4.55 ± 0.17, and a metallicity [Fe/H] =+0.04 ± 0.06. The stellar mass and radius determined through the empirical relationship of Torres et al. yields 1.10 ± 0.09 M ⊙ and 0.92 ± 0.19 R ⊙. The minimum mass of MARVELS-5b is 65.0 ± 2.9M Jup, indicating that it is likely to be either a BD or a very <span class="hlt">low</span> <span class="hlt">mass</span> star, thus occupying a relatively sparsely populated region of the mass function of companions to solar-type stars. The distance to this <span class="hlt">system</span> is 101 ± 10 pc from the astrometric measurements of Hipparcos. No stellar tertiary is detected in the high-contrast images taken by either FastCam lucky imaging or Keck adaptive optics imaging, ruling out any star with mass greater than 0.2 M ⊙ at a separation larger than 40 AU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22136553','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22136553"><span id="translatedtitle">VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. IV. A CANDIDATE BROWN DWARF OR <span class="hlt">LOW-MASS</span> STELLAR COMPANION TO HIP 67526</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jiang Peng; Ge Jian; De Lee, Nathan; Fleming, Scott W.; Lee, Brian L.; Ma Bo; Wang, Ji; Cargile, Phillip; Hebb, Leslie; Stassun, Keivan G.; Crepp, Justin R.; Porto de Mello, Gustavo F.; Ferreira, Leticia D.; Esposito, Massimiliano; Femenia, Bruno; Gonzalez Hernandez, Jonay I.; Ghezzi, Luan; Wisniewski, John P.; Agol, Eric; and others</p> <p>2013-09-15</p> <p>We report the discovery of a candidate brown dwarf (BD) or a very <span class="hlt">low</span> <span class="hlt">mass</span> stellar companion (MARVELS-5b) to the star HIP 67526 from the Multi-object Apache point observatory Radial Velocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for this object contains 31 epochs spread over 2.5 yr. Our Keplerian fit, using a Markov Chain Monte Carlo approach, reveals that the companion has an orbital period of 90.2695{sup +0.0188}{sub -0.0187} days, an eccentricity of 0.4375 {+-} 0.0040, and a semi-amplitude of 2948.14{sup +16.65}{sub -16.55} m s{sup -1}. Using additional high-resolution spectroscopy, we find the host star has an effective temperature T{sub eff} = 6004 {+-} 34 K, a surface gravity log g (cgs) =4.55 {+-} 0.17, and a metallicity [Fe/H] =+0.04 {+-} 0.06. The stellar mass and radius determined through the empirical relationship of Torres et al. yields 1.10 {+-} 0.09 M{sub Sun} and 0.92 {+-} 0.19 R{sub Sun }. The minimum mass of MARVELS-5b is 65.0 {+-} 2.9M{sub Jup}, indicating that it is likely to be either a BD or a very <span class="hlt">low</span> <span class="hlt">mass</span> star, thus occupying a relatively sparsely populated region of the mass function of companions to solar-type stars. The distance to this <span class="hlt">system</span> is 101 {+-} 10 pc from the astrometric measurements of Hipparcos. No stellar tertiary is detected in the high-contrast images taken by either FastCam lucky imaging or Keck adaptive optics imaging, ruling out any star with mass greater than 0.2 M{sub Sun} at a separation larger than 40 AU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22522528','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22522528"><span id="translatedtitle">CHARACTERIZING THE STAR FORMATION OF THE <span class="hlt">LOW-MASS</span> SHIELD GALAXIES FROM HUBBLE SPACE TELESCOPE IMAGING</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McQuinn, Kristen B. W.; Skillman, Evan D.; Simones, Jacob E.; Cannon, John M.; Dolphin, Andrew E.; Haynes, Martha P.; Giovanelli, Riccardo; Salzer, John J.; Adams, Elizabeth A. K.; Elson, Ed C.; Ott, Jürgen</p> <p>2015-03-20</p> <p>The Survey of Hi in Extremely <span class="hlt">Low-mass</span> Dwarfs is an on-going multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very <span class="hlt">low-mass</span> galaxies that populate the faint end of the galaxy luminosity function. The galaxies were selected from the first ∼10% of the Hi Arecibo Legacy Fast ALFA survey based on their low Hi mass and low baryonic mass. Here, we measure the star formation properties from optically resolved stellar populations for 12 galaxies using a color–magnitude diagram fitting technique. We derive lifetime average star formation rates (SFRs), recent SFRs, stellar masses, and gas fractions. Overall, the recent SFRs are comparable to the lifetime SFRs with mean birthrate parameter of 1.4, with a surprisingly narrow standard deviation of 0.7. Two galaxies are classified as dwarf transition galaxies (dTrans). These dTrans <span class="hlt">systems</span> have star formation and gas properties consistent with the rest of the sample, in agreement with previous results that some dTrans galaxies may simply be low-luminosity dwarf irregulars. We do not find a correlation between the recent star formation activity and the distance to the nearest neighboring galaxy, suggesting that the star formation process is not driven by gravitational interactions, but regulated internally. Further, we find a broadening in the star formation and gas properties (i.e., specific SFRs, stellar masses, and gas fractions) compared to the generally tight correlation found in more massive galaxies. Overall, the star formation and gas properties indicate these very <span class="hlt">low-mass</span> galaxies host a fluctuating, non-deterministic, and inefficient star formation process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22270771','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22270771"><span id="translatedtitle">THE RADIUS DISCREPANCY IN <span class="hlt">LOW-MASS</span> STARS: SINGLE VERSUS BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Spada, F.; Demarque, P.; Kim, Y.-C.; Sills, A.</p> <p>2013-10-20</p> <p>A long-standing issue in the theory of <span class="hlt">low-mass</span> stars is the discrepancy between predicted and observed radii and effective temperatures. In spite of the increasing availability of very precise radius determinations from eclipsing binaries and interferometric measurements of radii of single stars, there is no unanimous consensus on the extent (or even the existence) of the discrepancy and on its connection with other stellar properties (e.g., metallicity, magnetic activity). We investigate the radius discrepancy phenomenon using the best data currently available (accuracy ∼< 5%). We have constructed a grid of stellar models covering the entire range of <span class="hlt">low-mass</span> stars (0.1-1.25 M{sub ☉}) and various choices of the metallicity and mixing length parameter, α. We used an improved version of the Yale Rotational stellar Evolution Code, implementing surface boundary conditions based on the most up-to-date PHOENIX atmosphere models. Our models are in good agreement with others in the literature and improve and extend the <span class="hlt">low</span> <span class="hlt">mass</span> end of the Yale-Yonsei isochrones. Our calculations include rotation-related quantities, such as moments of inertia and convective turnover timescales, useful in studies of magnetic activity and rotational evolution of solar-like stars. Consistent with previous works, we find that both binaries and single stars have radii inflated by about 3% with respect to the theoretical models; among binaries, the components of short orbital period <span class="hlt">systems</span> are found to be the most deviant. We conclude that both binaries and single stars are comparably affected by the radius discrepancy phenomenon.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...592A..32L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...592A..32L"><span id="translatedtitle">Search for light curve modulations among Kepler candidates. Three very <span class="hlt">low-mass</span> transiting companions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lillo-Box, J.; Ribas, A.; Barrado, D.; Merín, B.; Bouy, H.</p> <p>2016-07-01</p> <p>Context. Light curve modulations in the sample of Kepler planet candidates allows the disentangling of the nature of the transiting object by photometrically measuring its mass. This is possible by detecting the effects of the gravitational pull of the companion (ellipsoidal modulations) and in some cases, the photometric imprints of the Doppler effect when observing in a broad band (Doppler beaming). Aims: We aim to photometrically unveil the nature of some transiting objects showing clear light curve modulations in the phase-folded Kepler light curve. Methods: We selected a subsample among the large crop of Kepler objects of interest (KOIs) based on their chances to show detectable light curve modulations, i.e., close (a< 12 R⋆) and large (in terms of radius, according to their transit signal) candidates. We modeled their phase-folded light curves with consistent equations for the three effects, namely, reflection, ellipsoidal and beaming (known as REB modulations). Results: We provide detailed general equations for the fit of the REB modulations for the case of eccentric orbits. These equations are accurate to the photometric precisions achievable by current and forthcoming instruments and space missions. By using this mathematical apparatus, we find three close-in very <span class="hlt">low-mass</span> companions (two of them in the brown dwarf mass domain) orbiting main-sequence stars (KOI-554, KOI-1074, and KOI-3728), and reject the planetary nature of the transiting objects (thus classifying them as false positives). In contrast, the detection of the REB modulations and transit/eclipse signal allows the measurement of their mass and radius that can provide important constraints for modeling their interiors since just a few cases of <span class="hlt">low-mass</span> eclipsing binaries are known. Additionally, these new <span class="hlt">systems</span> can help to constrain the similarities in the formation process of the more massive and close-in planets (hot Jupiters), brown dwarfs, and very <span class="hlt">low-mass</span> companions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012A%26A...543A..65M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012A%26A...543A..65M"><span id="translatedtitle">A spectral line survey of the starless and <span class="hlt">proto-stellar</span> cores detected by BLAST toward the Vela-D molecular cloud</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morales Ortiz, J. L.; Olmi, L.; Burton, M.; De Luca, M.; Elia, D.; Giannini, T.; Lorenzetti, D.; Massi, F.; Strafella, F.</p> <p>2012-07-01</p> <p>Context. Starless cores represent a very early stage of the star formation process, before collapse results in the formation of a central protostar or a multiple <span class="hlt">system</span> of protostars. Aims: We use spectral line observations of a sample of cold dust cores, previously detected with the BLAST telescope in the Vela-D molecular cloud, to perform a more accurate physical and kinematical analysis of the sources. Methods: We present a 3-mm and 1.3-cm survey conducted with the Mopra 22-m and Parkes 64-m radio telescopes of a sample of 40 cold dust cores, including both starless and <span class="hlt">proto-stellar</span> sources. 20 objects were also mapped using molecular tracers of dense gas. To trace the dense gas we used the molecular species NH3, N2H+, HNC, HCO+, H13CO+, HCN and H13CN, where some of them trace the more quiescent gas, while others are sensitive to more dynamical processes. Results: The selected cores have a wide variety of morphological types and also show physical and chemical variations, which may be associated to different evolutionary phases. We find evidence of systematic motions in both starless and <span class="hlt">proto-stellar</span> cores and we detect line wings in many of the <span class="hlt">proto-stellar</span> cores. Our observations probe linear distances in the sources ≳ 0.1 pc, and are thus sensitive mainly to molecular gas in the envelope of the cores. In this region we do find that, for example, the radial profile of the N2H+(1-0) emission falls off more quickly than that of C-bearing molecules such as HNC(1-0), HCO+(1-0) and HCN(1-0). We also analyze the correlation between several physical and chemical parameters and the dynamics of the cores. Conclusions: Depending on the assumptions made to estimate the virial mass, we find that many starless cores have masses below the self-gravitating threshold, whereas most of the <span class="hlt">proto-stellar</span> cores have masses which are near or above the self-gravitating critical value. An analysis of the median properties of the starless and <span class="hlt">proto-stellar</span> cores suggests that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EAS....75..273T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EAS....75..273T"><span id="translatedtitle">Revolutionizing our View of <span class="hlt">Protostellar</span> Multiplicity and Disks: The VLA Nascent Disk and Multiplicity (VANDAM) Survey of the Perseus Molecular Cloud</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tobin, J. J.; Looney, L. W.; Li, Z.-Y.; Chandler, C. J.; Dunham, M. M.; Segura-Cox, D.; Cox, E. G.; Harris, R. J.; Melis, C.; Sadavoy, S. I.; Pérez, L.; Kratter, K.</p> <p>2016-05-01</p> <p>There is substantial evidence for disk formation taking place during the early stages of star formation and for most stars being born in multiple <span class="hlt">systems</span>; however, <span class="hlt">protostellar</span> multiplicity and disk searches have been hampered by low resolution, sample bias, and variable sensitivity. We have conducted an unbiased, high-sensitivity Karl G. Jansky Very Large Array (VLA) survey toward all known protostars (n = 94) in the Perseus molecular cloud (d ˜ 230 pc), with a resolution of ˜ 15 AU (0.06'') at λ = 8 mm. We have detected candidate <span class="hlt">protostellar</span> disks toward 17 sources (with 12 of those in the Class 0 stage) and we have found substructure on < 50 AU scales for three Class 0 disk candidates, possibly evidence for disk fragmentation. We have discovered 16 new multiple <span class="hlt">systems</span> (or new components) in this survey; the new <span class="hlt">systems</span> have separations < 500 AU and 3 by < 30 AU. We also found a bi-modal distribution of separations, with peaks at ˜ 75 AU and ˜ 3000 AU, suggestive of formation through two distinct mechanisms: disk and turbulent fragmentation. The results from this survey demonstrate the necessity and utility of uniform, unbiased surveys of <span class="hlt">protostellar</span> <span class="hlt">systems</span> at millimeter and centimeter wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011MNRAS.413.2595S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011MNRAS.413.2595S"><span id="translatedtitle">Rotation periods for very <span class="hlt">low</span> <span class="hlt">mass</span> stars in Praesepe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scholz, Alexander; Irwin, Jonathan; Bouvier, Jerome; Sipőcz, Brigitta M.; Hodgkin, Simon; Eislöffel, Jochen</p> <p>2011-06-01</p> <p>We investigate the rotation periods of fully convective very <span class="hlt">low</span> <span class="hlt">mass</span> (VLM, M < 0.3 M⊙) stars, with the aim to derive empirical constraints for the spin-down due to magnetically driven stellar winds. Our analysis is based on a new sample of rotation periods in the main-sequence cluster Praesepe (age 600 Myr). From photometric light curves obtained with the Isaac Newton Telescope, we measure rotation periods for 49 objects, among them 26 in the VLM domain. This enlarges the period sample in this mass and age regime by a factor of 6. Almost all VLM objects in our sample are fast rotators with periods <2.5 d, in contrast to the stars with M > 0.6 M⊙ in this cluster which have periods of 7-14 d. Thus, we confirm that the period-mass distribution in Praesepe exhibits a radical break at M˜ 0.3-0.6 M⊙. Our data indicate a positive period-mass trend in the VLM regime, similar to younger clusters. In addition, the scatter of the periods increases with mass. For the M > 0.3 M⊙ objects in our sample, the period distribution is probably affected by binarity. By comparing the Praesepe periods with literature samples in the cluster NGC 2516 (age ˜ 150 Myr) we constrain the spin-down in the VLM regime. An exponential rotational braking law P∝ exp (t/τ) with a mass-dependent τ is required to reproduce the data. The spin-down time-scale τ increases steeply towards lower masses; we derive τ˜ 0.5 Gyr for 0.3 M⊙ and >1 Gyr for 0.1 M⊙. These constraints are consistent with the current paradigm of the spin-down due to wind braking. We discuss possible physical origins of this behaviour and prospects for future work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999hst..prop.8334S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999hst..prop.8334S"><span id="translatedtitle">HD 98800: An Opportunity to Measure True Masses for <span class="hlt">Low-Mass</span> PMS Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soderblom, David</p> <p>1999-07-01</p> <p>HD 98800 became interesting when IRAS found it to have a large infrared excess, indicating a substantial dust disk. But ``HD 98800'' is, in fact, a quadruple <span class="hlt">system</span> consisting of four K and M stars, and its Hipparcos parallax has now shown that this is a pre-main sequence <span class="hlt">system</span>. The four stars are in two visible objects, each of which is a spectroscopic binary with a period of about one year. In particular, the Ba-Bb pair is an SB2 with an estimated semi-major axis of about 20 milliarcsec. In TRANS mode, FGS1R can cleanly resolve the Ba-Bb pair and can determine the relative orbit and luminosities for the two components. POS mode observations lead to an absolute orbit and a more precise parallax than is currently available. In this program we propose to follow the HD 98800 Ba-Bb pair over the course of a full orbit during Cycle 8. The combination of FGS1R-TRANS and FGS1R-POS observations will provide gravitational masses for two <span class="hlt">low-mass</span> PMS stars. In addition, the co nstraints of coevality and knowled ge of the astrophysical properties of the components {temperatures, luminosities, composition} make these observations a crucial test of our models of pre-main sequence evolution. These may be the first true masses determined for <span class="hlt">low-mass</span> PMS objects, and so can provide a fundamental test of PMS evolutionary tracks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E1155L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E1155L"><span id="translatedtitle">Formation of Galactic Black Hole <span class="hlt">Low-Mass</span> X-ray Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Xiangdong</p> <p>2016-07-01</p> <p>Most of the Galactic black hole (BH) X-ray binary <span class="hlt">systems</span> are <span class="hlt">low-mass</span> X-ray binaries (LMXBs). Although the formation of these <span class="hlt">systems</span> has been extensively investigated, some crucial issues remain unresolved. The most noticeable one is that, the <span class="hlt">low-mass</span> companion has difficulties in ejecting the tightly bound envelope of the massive primary during the spiral-in process. While initially intermediate-mass binaries are more likely to survive the common envelope (CE) evolution, the resultant BH LMXBs mismatch the observations. Here we use both stellar evolution and binary population synthesis to study the evolutionary history of BH LMXBs. We test various assumptions and prescriptions for the supernova mechanisms that produce BHs, the binding energy parameter, the CE efficiency, and the initial mass distributions of the companion stars. We obtain the birthrate and the distributions of the donor mass, effective temperature and orbital period for the BH LMXBs in each case. By comparing the calculated results with the observations, we put useful constraints on the aforementioned parameters. In particular, we show that it is possible to form BH LMXBs with the standard CE scenario if most BHs are born through failed supernovae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EAS....75..123N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EAS....75..123N"><span id="translatedtitle">Observations of <span class="hlt">Protostellar</span> Outflow Feedback in Clustered Star Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, F.</p> <p>2016-05-01</p> <p>We discuss the role of <span class="hlt">protostellar</span> outflow feedback in clustered star formation using the observational data of recent molecular outflow surveys toward nearby cluster-forming clumps. We found that for almost all clumps, the outflow momentum injection rate is significantly larger than the turbulence dissipation rate. Therefore, the outflow feedback is likely to maintain supersonic turbulence in the clumps. For less massive clumps such as B59, L1551, and L1641N, the outflow kinetic energy is comparable to the clump gravitational energy. In such clumps, the outflow feedback probably affects significantly the clump dynamics. On the other hand, for clumps with masses larger than about 200 M⊙, the outflow kinetic energy is significantly smaller than the clump gravitational energy. Since the majority of stars form in such clumps, we conclude that outflow feedback cannot destroy the whole parent clump. These characteristics of the outflow feedback support the scenario of slow star formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...587A..32M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...587A..32M"><span id="translatedtitle">Ambipolar diffusion in <span class="hlt">low-mass</span> star formation. I. General comparison with the ideal magnetohydrodynamic case</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masson, J.; Chabrier, G.; Hennebelle, P.; Vaytet, N.; Commerçon, B.</p> <p>2016-03-01</p> <p> results for a given magnetisation, showing that the physical dissipation processes truly dominate numerical diffusion. We demonstrate severe limits of the ideal MHD formalism; it yields unphysical behaviours in the long-term evolution of the <span class="hlt">system</span>. This includes counter-rotation inside the outflow or magnetic tower, interchange instabilities, and flux redistribution triggered by numerical diffusion. These effects are not observed in non-ideal MHD. Disks with Keplerian velocity profiles are found to form around the protostar in all our non-ideal MHD simulations, with a final mass and size that strongly depend on the initial magnetisation. This ranges from a few 10-2M⊙ and ~20-30 au for the most magnetised case (μ = 2) to ~2 × 10-1M⊙ and ~40-80 au for a lower magnetisation (μ = 5). In all cases, these disks remain significantly smaller than disks found in pure hydrodynamical simulations. Ambipolar diffusion thus bears a crucial impact on the regulation of magnetic flux and angular momentum transport during the collapse of a prestellar core and the formation of the resulting <span class="hlt">protostellar</span> core-disk <span class="hlt">system</span>, enabling the formation and growth of rotationally supported structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ApJ...681.1356M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ApJ...681.1356M"><span id="translatedtitle">Magnetic Braking and <span class="hlt">Protostellar</span> Disk Formation: The Ideal MHD Limit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mellon, Richard R.; Li, Zhi-Yun</p> <p>2008-07-01</p> <p>Magnetic fields are usually considered dynamically important in star formation when the dimensionless mass-to-flux ratio is close to, or less than, unity (λ lesssim 1). We show that, in disk formation, the requirement is far less stringent. This conclusion is drawn from a set of 2D (axisymmetric) simulations of the collapse of rotating, singular isothermal cores magnetized to different degrees. We find that a weak field corresponding to λ ~ 100 can begin to disrupt the rotationally supported disk through magnetic braking, by creating regions of rapid, supersonic collapse in the disk. These regions are separated by one or more centrifugal barriers, where the rapid infall is temporarily halted. The number of centrifugal barriers increases with the mass-to-flux ratio λ. When λ gtrsim 100, they merge together to form a more or less contiguous, rotationally supported disk. Even though the magnetic field in such a case is extremely weak on the scale of dense cores, it is amplified by collapse and differential rotation, to the extent that its pressure dominates the thermal pressure in both the disk and its surrounding region. For relatively strongly magnetized cores with λ lesssim 10, the disk formation is suppressed completely, as found previously. A new feature is that the mass accretion is highly episodic, due to reconnection of the magnetic field lines accumulated near the center. For rotationally supported disks to appear during the <span class="hlt">protostellar</span> mass accretion phase of star formation in dense cores with realistic field strengths, the powerful magnetic brake must be weakened, perhaps through nonideal MHD effects. Another possibility is to remove, through <span class="hlt">protostellar</span> winds, the material that acts to brake the disk rotation. We discuss the possibility of observing a generic product of the magnetic braking, an extended circumstellar region that is supported by a combination of toroidal magnetic field and rotation—a "magnetogyrosphere"—interferometrically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22126998','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22126998"><span id="translatedtitle">MAGNETIZED ACCRETION AND DEAD ZONES IN <span class="hlt">PROTOSTELLAR</span> DISKS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dzyurkevich, Natalia; Henning, Thomas; Turner, Neal J.; Kley, Wilhelm</p> <p>2013-03-10</p> <p>The edges of magnetically dead zones in <span class="hlt">protostellar</span> disks have been proposed as locations where density bumps may arise, trapping planetesimals and helping form planets. Magneto-rotational turbulence in magnetically active zones provides both accretion of gas on the star and transport of mass to the dead zone. We investigate the location of the magnetically active regions in a <span class="hlt">protostellar</span> disk around a solar-type star, varying the disk temperature, surface density profile, and dust-to-gas ratio. We also consider stellar masses between 0.4 and 2 M{sub Sun }, with corresponding adjustments in the disk mass and temperature. The dead zone's size and shape are found using the Elsasser number criterion with conductivities including the contributions from ions, electrons, and charged fractal dust aggregates. The charged species' abundances are found using the approach proposed by Okuzumi. The dead zone is in most cases defined by the ambipolar diffusion. In our maps, the dead zone takes a variety of shapes, including a fish tail pointing away from the star and islands located on and off the midplane. The corresponding accretion rates vary with radius, indicating locations where the surface density will increase over time, and others where it will decrease. We show that density bumps do not readily grow near the dead zone's outer edge, independently of the disk parameters and the dust properties. Instead, the accretion rate peaks at the radius where the gas-phase metals freeze out. This could lead to clearing a valley in the surface density, and to a trap for pebbles located just outside the metal freezeout line.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22348143','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22348143"><span id="translatedtitle">One hundred first stars: <span class="hlt">Protostellar</span> evolution and the final masses</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hirano, Shingo; Umeda, Hideyuki; Hosokawa, Takashi; Yoshida, Naoki; Chiaki, Gen; Omukai, Kazuyuki; Yorke, Harold W.</p> <p>2014-02-01</p> <p>We perform a large set of radiation hydrodynamic simulations of primordial star formation in a fully cosmological context. Our statistical sample of 100 First Stars shows that the first generation of stars has a wide mass distribution M {sub popIII} = 10 ∼ 1000 M {sub ☉}. We first run cosmological simulations to generate a set of primordial star-forming gas clouds. We then follow protostar formation in each gas cloud and the subsequent <span class="hlt">protostellar</span> evolution until the gas mass accretion onto the protostar is halted by stellar radiative feedback. The accretion rates differ significantly among the primordial gas clouds that largely determine the final stellar masses. For low accretion rates, the growth of a protostar is self-regulated by radiative feedback effects, and the final mass is limited to several tens of solar masses. At high accretion rates the protostar's outer envelope continues to expand, and the effective surface temperature remains low; such protostars do not exert strong radiative feedback and can grow in excess of 100 solar masses. The obtained wide mass range suggests that the first stars play a variety of roles in the early universe, by triggering both core-collapse supernovae and pair-instability supernovae as well as by leaving stellar mass black holes. We find certain correlations between the final stellar mass and the physical properties of the star-forming cloud. These correlations can be used to estimate the mass of the first star from the properties of the parent cloud or of the host halo without following the detailed <span class="hlt">protostellar</span> evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Ap%26SS.357...81J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Ap%26SS.357...81J"><span id="translatedtitle">The dead zone size limits in a <span class="hlt">proto-stellar</span> accretion disc model heated by the damping of Alfvén waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jatenco-Pereira, V.</p> <p>2015-05-01</p> <p>Heating of <span class="hlt">proto-stellar</span> accretion discs has been studied by several authors. Jatenco-Pereira (Mon. Not. R. Astron. Soc. 431:3150, 2013) proposed a disc model with two heating mechanisms: the "anomalous" viscosity considered in terms of the α-prescription and the damping of Alfvén waves. As the discs are composed of dust, it was considered that when charged dust particles acquire the same (cyclotron) frequency as the waves, a resonance occurs that leads to the damping of the waves. Here we show that the increase in the temperature of the disc midplane implies in the reduction of the size of the quiescent region in <span class="hlt">proto-stellar</span> discs and compare it with the actual position of the solar <span class="hlt">system</span> planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060037445&hterms=ccs&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dccs','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060037445&hterms=ccs&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dccs"><span id="translatedtitle">CCS Observations of the <span class="hlt">Protostellar</span> Envelope of B335</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Velusamy, T.; Kuiper, T. B. H.; Langer, W. D.</p> <p>1995-01-01</p> <p>Knowledge of the density, velocity and chemical profiles around protostars is of fundamental importance for testing dynamical models of protostar evolution and understanding the nature of the material falling onto circumstellar disks. Presented are single dish and interferometric spectral line observations of CCS towards the core of B335, a classic example of a young, <span class="hlt">low</span> <span class="hlt">mass</span> stellar object.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19830060416&hterms=Source+Status&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DSource%2BStatus','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19830060416&hterms=Source+Status&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DSource%2BStatus"><span id="translatedtitle">On the evolutionary status of bright, <span class="hlt">low-mass</span> X-ray sources</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Webbink, R. F.; Rappaport, S.; Savonije, G. J.</p> <p>1983-01-01</p> <p>A model of bright, <span class="hlt">low-mass</span> X-ray binaries is proposed which features a lower giant-branch star losing mass on a nuclear time scale to an accreting compact companion. Simple numerical models show that mass transfer rates equal to or greater than 10 to the -9th solar masses per yr are sustained at very nearly a constant rate until the envelope of the donor star is exhausted. The model predicts orbital periods in the range 1-200 days and X-ray to optical luminosity ratios Lx/Lopt = 200-1000 for these sources. It accounts in a natural way for the large fraction of the total galactic bulge luminosity emitted by a few bright (10 to the 37th erg/s or greater) sources. It also accords very well with the observed X-ray and optical properties of the halo source Cyg X-2 and also with those of 2S 0921-63, provided this latter <span class="hlt">system</span> contains a massive accreting white dwarf rather than a neutron star. Problems of the prior evolution of <span class="hlt">low-mass</span> X-ray sources are also briefly delineated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.tmp.1245F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.tmp.1245F"><span id="translatedtitle">Under Pressure: Quenching Star Formation in <span class="hlt">Low-Mass</span> Satellite Galaxies via Stripping</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fillingham, Sean P.; Cooper, Michael C.; Pace, Andrew B.; Boylan-Kolchin, Michael; Bullock, James S.; Garrison-Kimmel, Shea; Wheeler, Coral</p> <p>2016-08-01</p> <p>Recent studies of galaxies in the local Universe, including those in the Local Group, find that the efficiency of environmental (or satellite) quenching increases dramatically at satellite stellar masses below ˜108~M⊙. This suggest a physical scale where quenching transitions from a slow "starvation" mode to a rapid "stripping" mode at <span class="hlt">low</span> <span class="hlt">masses</span>. We investigate the plausibility of this scenario using observed HI surface density profiles for a sample of 66 nearby galaxies as inputs to analytic calculations of ram-pressure and turbulent viscous stripping. Across a broad range of host properties, we find that stripping becomes increasingly effective at M★ ≲ 108 - 9~M⊙, reproducing the critical mass scale observed. However, for canonical values of the circumgalactic medium density (nhalo < 10-3.5 cm-3), we find that stripping is not fully effective; infalling satellites are, on average, stripped of only ≲ 40 - 60% of their cold gas reservoir, which is insufficient to match observations. By including a host halo gas distribution that is clumpy and therefore contains regions of higher density, we are able to reproduce the observed HI gas fractions (and thus the high quenched fraction and short quenching timescale) of Local Group satellites, suggesting that a host halo with clumpy gas may be crucial for quenching <span class="hlt">low-mass</span> <span class="hlt">systems</span> in Local Group-like (and more massive) host halos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22724101K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22724101K"><span id="translatedtitle">Atmospheres of Quiescent <span class="hlt">Low-Mass</span> Neutron Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karpov, Platon; Medin, Zachary; Calder, Alan; Lattimer, James M.</p> <p>2016-01-01</p> <p>Observations of the neutron stars in quiescent <span class="hlt">low-mass</span> X-ray binaries are important for determining their masses and radii which can lead to powerful constraints on the dense matter nuclear equation of state. The interpretation of these sources is complex and their spectra differ appreciably from blackbodies. Further progress hinges on reducing the uncertainties stemming from models of neutron star atmospheres. We present a suite of low-temperature neutron star atmospheres of different chemical compositions (pure H and He). Our models are constructed over a range of temperatures [log(T/1 K)=5.3, 5.6, 5.9, 6.2, 6.5] and surface gravities [log(g/1 cm/s2)=14.0, 14.2, 14.4, 14.6]. We generated model atmospheres using zcode - a radiation transfer code developed at Los Alamos National Laboratory. In order to facilitate analytic studies, we developed three-parameter fits to our models, and also compared them to diluted blackbodies in the energy range of 0.4-5 keV (CXO/MGE). From the latter, we extract color-correction factors (fc), which represent the shift of the spectra as compared to a blackbody with the same effective temperature. These diluted blackbodies are also useful for studies of photspheric expansion X-ray bursts. We provide a comparison of our models to previous calculations using the McGill Planar Hydrogen Atmosphere Code (McPHAC). These results enhance our ability to interpret thermal emission from neutron stars and to constrain the mass-radius relationship of these exotic objects.This research was supported in part by the U.S. Department of Energy under grant DE-FG02-87ER40317 and by resources at the Institute for Advanced Computational Science at Stony Brook University. This research was carried out in part under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory and supported by Contract No. DE-AC52-06NA25396.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950041415&hterms=stars+lifetime&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dstars%2Blifetime','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950041415&hterms=stars+lifetime&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dstars%2Blifetime"><span id="translatedtitle">Very <span class="hlt">low</span> <span class="hlt">mass</span> stars and white dwarfs in NGC 6397</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paresce, Francesco; De Marchi, Guido; Romaniello, Martino</p> <p>1995-01-01</p> <p>Deep Wide Field/Planetary Camera 2 (WFPC2) images in wide bands centered at 606 and 802 nm were taken with the Hubble Space Telescope (HST) 4.6 min from the center of the galactic globular cluster NGC 6397. The images were used to accurately position approximately 2120 stars detected in the field on a color magnitude diagram down to a limiting magnitude m(sub 814) approximately = m(sub I) approximately = 26 determined reliably and solely by counting statistics. A white dwarf sequence and a rich, narrow cluster main sequence are detected for the first time, the latter stretching from m(sub 814) = 18.5 to m(sub 814) = 24.0 where it becomes indistinguishable from the field population. Two changes of slope of the main sequence at m(sub 814) approximately = 20 and m(sub 814) approximately = 22.5 are evident. The corresponding luminosity function increases slowly from M(sub 814) approximately = 6.5 to 8.5 are expected from ground-based observations but then drops sharply from there dwon to the measurement limit. The corresponding mass function obtained bu using the only presently available mass-luminosity function for the cluster's metallicity rises to a plateau between approximately 0.25 and approximately 0.15 solar mass, but drops toward the expected mass limit of the normal hydrogen burning main sequence at approximately 0.1 solar mass. This result is in clear contrast to that obtained from the ground and implies either a substantial modification of the cluster's initial mass function due to dynamical evolution in its lifetime, or that very <span class="hlt">low</span> <span class="hlt">mass</span> stars are not produced in any dynamically significant amount by clusters of this type. The white dwarf sequence is in reasonable agreement with a cooling sequence of models of mass 0.5 solar mass at the canonical distance of NGC 6397 with a scatter that is most likely due to photometric errors, but may also reflect real differences in mass or chemical composition. Contamination from unresolved galaxies, which cannot be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100028886','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100028886"><span id="translatedtitle">Miniature <span class="hlt">Low-Mass</span> Drill Actuated by Flextensional Piezo Stack</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph</p> <p>2010-01-01</p> <p> characteristics of <span class="hlt">low</span> <span class="hlt">mass</span>, small size, low power, and low axial loads for sampling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013A%26A...553A..75C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013A%26A...553A..75C&link_type=ABSTRACT"><span id="translatedtitle">Heavy water stratification in a <span class="hlt">low-mass</span> protostar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coutens, A.; Vastel, C.; Cazaux, S.; Bottinelli, S.; Caux, E.; Ceccarelli, C.; Demyk, K.; Taquet, V.; Wakelam, V.</p> <p>2013-05-01</p> <p>Context. Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular deuterium fractionation has been found in the environments of <span class="hlt">low-mass</span> star-forming regions and, in particular, the Class 0 protostar IRAS 16293-2422. Aims: The key program Chemical HErschel Surveys of Star forming regions (CHESS) aims at studying the molecular complexity of the interstellar medium. The high sensitivity and spectral resolution of the Herschel/HIFI (Heterodyne Instrument for Far-Infrared) instrument provide a unique opportunity to observe the fundamental 11,1-00,0 transition of ortho-D2O at 607 GHz and the higher energy 21,2-10,1 transition of para-D2O at 898 GHz, both of which are inaccessible from the ground. Methods: The ortho-D2O transition at 607 GHz was previously detected. We present in this paper the first tentative detection for the para-D2O transition at 898 GHz. The spherical Monte Carlo radiative transfer code RATRAN was used to reproduce the observed line profiles of D2O with the same method that was used to reproduce the HDO and H218O line profiles in IRAS 16293-2422. Results: As for HDO, the absorption component seen on the D2O lines can only be reproduced by adding an external absorbing layer, possibly created by the photodesorption of the ices at the edges of the molecular cloud. The D2O column density is found to be about 2.5 × 1012 cm-2 in this added layer, leading to a D2O/H2O ratio of about 0.5%. At a 3σ uncertainty, upper limits of 0.03% and 0.2% are obtained for this ratio in the hot corino and the colder envelope of IRAS 16293-2422, respectively. Conclusions: The deuterium fractionation derived in our study suggests that the ices present in IRAS 16293-2422 formed on warm dust grains (~15-20 K) in dense (~104-5 × 104 cm-3) translucent clouds. These results allow us to address the earliest phases of star formation and the conditions in which ices form. Based on Herschel/HIFI observations. Herschel is an ESA space observatory with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.........3M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.........3M"><span id="translatedtitle">Revealing the Chamaeleon: Young, <span class="hlt">low-mass</span> stars surrounding eta and epsilon Chamaeleontis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murphy, S. J.</p> <p>2012-01-01</p> <p>The deep southern sky surrounding the Chamaeleon dark clouds is abundant with pre-main sequence stars of various ages. Because of their youth (5-10 Myr) and proximity (d~100 pc), members of the open cluster eta Chamaeleontis and the nearby epsilon Chamaeleontis Association are ideal laboratories to study the formation and evolution of extrasolar planetary <span class="hlt">systems</span>. To better understand their role as potential planet hosts, this thesis explores the formation, dynamical evolution, accretion and disk properties of both groups' <span class="hlt">low-mass</span> members. The notable lack of <span class="hlt">low-mass</span> stars in the young open cluster eta Cha has long been puzzling. Two possible explanations have been suggested; a top-heavy initial mass function or dynamical evolution, which preferentially ejected the <span class="hlt">low-mass</span> members. Previous efforts to find these stars several degrees from the cluster core have been unsuccessful. By undertaking a wider (95 sq deg) photometric and proper motion survey with extensive follow-up spectroscopy, we have identified eight <span class="hlt">low-mass</span> stars that were ejected from eta Cha over the past 5-10 Myr. Comparison with recent simulations shows our results are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an initial mass function deficient in <span class="hlt">low-mass</span> objects. Two of the dispersed members exhibited strong, variable H-alpha emission during our observations, including a star which had an event suggestive of accretion from a circumstellar disk. New infrared photometry confirms the presence of the disk. This star demonstrates that infrequent, episodic accretion can continue at low levels long after most disks around `old' pre-main sequence stars have dissipated. Another two confirmed non-members are slightly older than the cluster, but are only 42 arcseconds apart and share similar kinematics and distances. We show that they almost certainly form a wide (4000-6000 AU) ~10 Myr-old binary at 100-150 pc. The <span class="hlt">system</span> is one of the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003ApJ...583..809H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003ApJ...583..809H"><span id="translatedtitle">Inner Structure of <span class="hlt">Protostellar</span> Collapse Candidate B335 Derived from Millimeter-Wave Interferometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harvey, Daniel W. A.; Wilner, David J.; Myers, Philip C.; Tafalla, Mario; Mardones, Diego</p> <p>2003-02-01</p> <p>We present a study of the density structure of the <span class="hlt">protostellar</span> collapse candidate B335 using continuum observations from the IRAM Plateau de Bure Interferometer made at wavelengths of 1.2 and 3.0 mm. We analyze these data, which probe spatial scales from 5000 to 500 AU, directly in the visibility domain by comparison with synthetic observations constructed from models that assume different physical conditions. This approach allows for much more stringent constraints to be derived from the data than from analysis of images. A single radial power law in density provides a good description of the data, with a best-fit power-law density index p=1.65+/-0.05. Through simulations, we quantify the sensitivity of this result to various model uncertainties, including assumptions of temperature distribution, outer boundary, dust opacity spectral index, and an unresolved central component. The largest uncertainty comes from the unknown presence of a centralized point source. The maximal point source, with 1.2 mm flux of F=12+/-7 mJy, reduces the power-law density index to p=1.47+/-0.07. The remaining sources of systematic uncertainty, of which the most important is the radial dependence of the temperature distribution, likely contribute a total uncertainty at the level of δp<~0.2. Taking into account the uncertainties, we find strong evidence that the power-law index of the density distribution within 5000 AU is significantly less than the value at larger radii, close to 2.0, from previous studies of dust emission and extinction. Images made from the data show clear departures from spherical symmetry, with the globule being slightly extended perpendicular to the outflow axis. The inclusion of a crude model of the outflow as a hollow bipolar cone of constant opening angle improves the fit and leaves the resulting density power-law index unchanged. These results conform well to the generic paradigm of isolated, <span class="hlt">low-mass</span> star formation, which predicts a power-law density index</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22127016','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22127016"><span id="translatedtitle">UNVEILING THE DETAILED DENSITY AND VELOCITY STRUCTURES OF THE <span class="hlt">PROTOSTELLAR</span> CORE B335</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kurono, Yasutaka; Saito, Masao; Kamazaki, Takeshi; Morita, Koh-Ichiro; Kawabe, Ryohei</p> <p>2013-03-10</p> <p>We present an observational study of the <span class="hlt">protostellar</span> core B335 harboring a <span class="hlt">low-mass</span> Class 0 source. The observations of the H{sup 13}CO{sup +}(J = 1-0) line emission were carried out using the Nobeyama 45 m telescope and Nobeyama Millimeter Array. Our combined image of the interferometer and single-dish data depicts detailed structures of the dense envelope within the core. We found that the core has a radial density profile of n(r){proportional_to}r {sup -p} and a reliable difference in the power-law indices between the outer and inner regions of the core: p Almost-Equal-To 2 for r {approx}> 4000 AU and p Almost-Equal-To 1.5 for r {approx}< 4000 AU. The dense core shows a slight overall velocity gradient of {approx}1.0 km s{sup -1} over the scale of 20, 000 AU across the outflow axis. We believe that this velocity gradient represents a solid-body-like rotation of the core. The dense envelope has a quite symmetrical velocity structure with a remarkable line broadening toward the core center, which is especially prominent in the position-velocity diagram across the outflow axis. The model calculations of position-velocity diagrams do a good job of reproducing observational results using the collapse model of an isothermal sphere in which the core has an inner free-fall region and an outer region conserving the conditions at the formation stage of a central stellar object. We derived a central stellar mass of {approx}0.1 M{sub Sun }, and suggest a small inward velocity, v{sub r{>=}r{sub i{sub n{sub f}}}}{approx}0 km s{sup -1} in the outer core at {approx}> 4000 AU. We concluded that our data can be well explained by gravitational collapse with a quasi-static initial condition, such as Shu's model, or by the isothermal collapse of a marginally critical Bonnor-Ebert sphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22140172','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22140172"><span id="translatedtitle"><span class="hlt">PROTOSTELLAR</span> DISK EVOLUTION OVER MILLION-YEAR TIMESCALES WITH A PRESCRIPTION FOR MAGNETIZED TURBULENCE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Landry, Russell; Dodson-Robinson, Sarah E.; Turner, Neal J.</p> <p>2013-07-10</p> <p>Magnetorotational instability (MRI) is the most promising mechanism behind accretion in <span class="hlt">low-mass</span> <span class="hlt">protostellar</span> disks. Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulence activity criteria to determine thermal structure and accretion rate without resorting to a three-dimensional magnetohydrodynamical (MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times the minimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositional gradients. Second, the surface density of the active layer is nearly constant in time at roughly 10 g cm{sup -2}, which we use to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHD computations. Furthermore, unlike a standard disk with constant-{alpha} viscosity, the disk midplane does not cool off over time, though the surface cools as the star evolves along the Hayashi track. Instead, the MRI may pile material in the dead zone, causing it to heat up over time. The ice line is firmly in the terrestrial planet-forming region throughout disk evolution and can move either inward or outward with time, depending on whether pileups form near the star. Finally, steady-state mass transport is an extremely poor description of flow through an MRI-active disk, as we see both the turnaround in the accretion flow required by conservation of angular momentum and peaks in M-dot (R) bracketing each side of the dead zone. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grain size, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameter study here. Our 1+1D model also does not include azimuthal information, which prevents</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013cxo..prop.3759B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013cxo..prop.3759B"><span id="translatedtitle">Measuring the X-ray Emission Impacting the Planets Orbiting Nearby <span class="hlt">Low-mass</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Alexander</p> <p>2013-09-01</p> <p>M dwarf planetary <span class="hlt">systems</span> present a truly exciting opportunity to discover and study the first habitable extrasolar planets in the next 5-10 years. As part of our larger HST MUSCLES project, we propose ACIS-S observations of 4 <span class="hlt">low-mass</span> exoplanet hosts (3 M dwarfs -- GJ581, GJ1214, GJ849, and 1 K dwarf -- HD97658) that have no existing measurements of their coronal X-ray emission. We will measure their X-ray luminosities and coronal temperatures, and derive the high energy radiation field to facilitate exoplanet atmospheric modeling. These planetary <span class="hlt">systems</span> allow study of exoplanet atmospheric chemistry and evolution under a wide diversity of physical situations. X-ray heating enhances evaporation and atmospheric escape, which can impact the long-term stability of exoplanetary atmospheres.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25278637','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25278637"><span id="translatedtitle"><span class="hlt">Low</span> <span class="hlt">Mass</span>-Damping Vortex-Induced Vibrations of a Single Cylinder at Moderate Reynolds Number.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jus, Y; Longatte, E; Chassaing, J-C; Sagaut, P</p> <p>2014-10-01</p> <p>The feasibility and accuracy of large eddy simulation is investigated for the case of three-dimensional unsteady flows past an elastically mounted cylinder at moderate Reynolds number. Although these flow problems are unconfined, complex wake flow patterns may be observed depending on the elastic properties of the structure. An iterative procedure is used to solve the structural dynamic equation to be coupled with the Navier-Stokes <span class="hlt">system</span> formulated in a pseudo-Eulerian way. A moving mesh method is involved to deform the computational domain according to the motion of the fluid structure interface. Numerical simulations of vortex-induced vibrations are performed for a freely vibrating cylinder at Reynolds number 3900 in the subcritical regime under two <span class="hlt">low</span> <span class="hlt">mass</span>-damping conditions. A detailed physical analysis is provided for a wide range of reduced velocities, and the typical three-branch response of the amplitude behavior usually reported in the experiments is exhibited and reproduced by numerical simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015sptz.prop11183F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015sptz.prop11183F"><span id="translatedtitle">V404 Cyg - an Interacting Black-Hole <span class="hlt">Low-Mass</span> X-ray Binary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fox, Ori; Mauerhan, Jon; Graham, Melissa</p> <p>2015-07-01</p> <p>This DDT proposal is prompted by the June 15, 2015 outburst of V404 Cyg, a black-hole (BH) <span class="hlt">low-mass</span> X-ray binary (LMXB). This outburst stands out since it is the first black hole <span class="hlt">system</span> with a measured parallax, lying at a distance of only 2.39+/-0.14 kpc. An extensive and loosely organized multi-wavelength campaign is already underway by the astronomical community. One of the missing pieces of the puzzle is the mid-infrared (IR). Combined with radio, optical, and X-ray data, the mid-IR will help to discriminate discriminate between an accretion disk, jet emission, or circumstellar dust scenarios. Spitzer offers a unique opportunity to observe at these wavelengths. Here we propose 4 very short (5-minutes at 3.6 and 4.5 micron) observations of IRAC hotometry to search for the presence of warm dust and, if present, constrain the heating mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014hst..prop13642D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014hst..prop13642D"><span id="translatedtitle">The evolutionary link between <span class="hlt">low-mass</span> X-ray binaries and millisecond radio pulsars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Degenaar, Nathalie</p> <p>2014-10-01</p> <p><span class="hlt">Low-mass</span> X-ray binaries (LMXBs) and millisecond radio pulsars (MSRPs) are two different manifestations of neutron stars in binary <span class="hlt">systems</span>. They are thought to be evolutionary linked, but many questions about their connection remain. Recent discoveries have opened up a new vista to investigate the LMXB/MSRP link. The neutron star XSS J12270-4859 was recently observed to switch between the two different manifestations. Here, we propose to exploit the unique UV capabilities of the HST to search for the presence of a quiescent accretion disk and to test if the neutron star is hot. This will give insight into its accretion history and the mechanism driving its metamorphosis, which will have direct implications for our understanding of the LMXB/MSRP evolutionary link.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22092436','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22092436"><span id="translatedtitle">PLANETS AROUND <span class="hlt">LOW-MASS</span> STARS (PALMS). II. A <span class="hlt">LOW-MASS</span> COMPANION TO THE YOUNG M DWARF GJ 3629 SEPARATED BY 0.''2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Tamura, Motohide</p> <p>2012-09-01</p> <p>We present the discovery of a 0.''2 companion to the young M dwarf GJ 3629 as part of our high-contrast adaptive optics imaging search for giant planets around <span class="hlt">low-mass</span> stars with the Keck-II and Subaru telescopes. Two epochs of imaging confirm that the pair is comoving and reveal signs of orbital motion. The primary exhibits saturated X-ray emission which, together with its UV photometry from GALEX, points to an age younger than {approx}300 Myr. At these ages the companion lies below the hydrogen burning limit with a model-dependent mass of 46 {+-} 16 M{sub Jup} based on the <span class="hlt">system</span>'s photometric distance of 22 {+-} 3 pc. Resolved YJHK photometry of the pair indicates a spectral type of M7 {+-} 2 for GJ 3629 B. With a projected separation of 4.4 {+-} 0.6 AU and an estimated orbital period of 21 {+-} 5 yr, GJ 3629 AB is likely to yield a dynamical mass in the next several years, making it one of only a handful of brown dwarfs to have a measured mass and an age constrained from the stellar primary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...583A.125O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...583A.125O"><span id="translatedtitle">Herschel-HIFI observations of H2O, NH3, and N2H+ toward high-mass starless and <span class="hlt">protostellar</span> clumps identified by the Hi-GAL survey⋆</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olmi, L.; Persson, C. M.; Codella, C.</p> <p>2015-11-01</p> <p>Context. Our present understanding of high-mass star formation still remains very schematic. In particular, it is not yet clear how much of the difference between <span class="hlt">low-mass</span> and high-mass star formation occurs during the earliest star formation phases. Aims: The chemical characteristics of massive cold clumps, and the comparison with those of their <span class="hlt">low-mass</span> counterparts, could provide crucial clues about the exact role that chemistry plays in differentiating the early phases of <span class="hlt">low-mass</span> and high-mass star formation. Water, in particular, is a unique probe of physical and chemical conditions in star-forming regions. Methods: Using the HIFI instrument of Herschel, we have observed the ortho-NH3 (10-00) (572 GHz), ortho-H2O (110-101) (557 GHz), and N2H+ (6-5) (559 GHz) lines toward a sample of high-mass starless and <span class="hlt">protostellar</span> clumps selected from the Herschel Infrared Galactic Plane Survey (Hi-GAL). We compare our results to previous studies of <span class="hlt">low-mass</span> and high-mass <span class="hlt">protostellar</span> objects. Results: At least one of the three molecular lines was detected in 4 (out of 35) and 7 (out of 17) objects in the ℓ = 59° and ℓ = 30° galactic regions, respectively. All detected sources are <span class="hlt">protostellar</span>. The water spectra are complex and consist of several kinematic components, identified through a Gaussian decomposition, and we detected inverse and regular P-Cygni profiles in a few sources. All water line profiles of the ℓ = 59° region are dominated by a broad Gaussian emission feature, indicating that the bulk of the water emission arises in outflows. No such broad emission is detected toward the ℓ = 30° objects. The ammonia line in some cases also shows line wings and an inverse P-Cygni profile, thus confirming that NH3 rotational transitions can be used to probe the dynamics of high-mass, star-forming regions. Both bolometric and water line luminosity increase with the continuum temperature. Conclusions: The higher water abundance toward the ℓ = 59° sources</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012noao.prop..400G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012noao.prop..400G"><span id="translatedtitle">A SuperWASP Benchmark Eclipsing Binary with a Very <span class="hlt">Low-Mass</span> Secondary in the Brown Dwarf Desert</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gomez Maqueo Chew, Yilen; Garcia-Melendo, Enrique; Hebb, Leslie; Faedi, Francesca; Lopez-Morales, Mercedes; Pollacco, Don</p> <p>2012-08-01</p> <p>We will obtain eclipse light curves of a newly discovered eclipsing binary composed of a Sun-like primary with a secondary companion which can be either a very <span class="hlt">low</span> <span class="hlt">mass</span> M-dwarf (less than ~0.15 Msun) or a brown dwarf. The objects orbit each other with a period of ~14.3 days in an eccentric orbit, which as been confirmed with a high- precision radial velocity curve for the <span class="hlt">system</span>. Therefore, these eclipse light curves will allow us to constrain the radii of the eclipsing components and orbital inclination of the <span class="hlt">system</span>. Furthermore, the depth of the secondary eclipse which can only be observed in the near-infrared, directly constrains the temperature ratio between the components. In combination with the the masses derived from the radial velocity curve, our light curve analysis will unveil the true nature of the secondary. Whether it is a very-<span class="hlt">low</span> <span class="hlt">mass</span> star or a brown dwarf, direct measurements of the fundamental properties (masses, radii and temperatures) of such objects are very scarce and will provide key tests to current evolutionary models. Thus, we request two nights with FLAMINGOS at the KPNO 2.1m to observe a complete secondary eclipse of the <span class="hlt">system</span> at near-infrared wavelengths in order to fully characterize the very <span class="hlt">low-mass</span> component of the <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.........7D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.........7D"><span id="translatedtitle">Constraining the coevolution of galaxies and black holes at <span class="hlt">low</span> <span class="hlt">mass</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Desroches, Louis-Benoit</p> <p>2009-06-01</p> <p> present results from reverberation mapping, a technique that is used to estimate the mass of the central BH ( M BH ). We estimate M BH [approximate] 3 × 10^5 [Special characters omitted.] , consistent with another reverberation result based on simultaneous UV observations. In Chapter 4, we present an archival study of Chandra X-ray Telescope data, in which we search for AGN signatures in a population of bulgeless or nearly- bulgeless late-type spiral galaxies. Motivated by the case of NGC 4395, it is unclear how many BHs exist in bulgeless <span class="hlt">systems</span>. Optical studies are notoriously poorly suited for this task, since BHs in such late-type spirals are likely of <span class="hlt">low</span> <span class="hlt">mass</span> (since the host galaxy is equally of <span class="hlt">low</span> <span class="hlt">mass</span>) and thus have very weak AGN signatures. In addition, late-type spirals have relatively large amounts of circumnuclear gas and dust, which easily obscures optical radiation. X-ray photons are largely unaffected (excluding exceptionally large columns of gas) and are therefore a more reliable indicator of central AGN activity (even weak, radiatively inefficient accretion). Unfortunately, stellar-mass BH binaries are equally capable of producing such X-ray emission, and we lack the depth, spacial resolution, and sensitivity to make a definitive identification. Based on nuclear stellar densities and the probability of finding an X-ray binary, we still conclude that roughly ~20-25% of bulgeless galaxies host an AGN, implying that objects such as NGC 4395 are not as rare as once thought. Finally, in Chapter 5, we present a comprehensive X-ray study of a large sample of intermediate-mass BHs discovered in SDSS via optical identification of broad emission lines. Such BHs, while sampling a mass regime that is poorly understood, are biased toward high accretion rates to make them optically identifiable. Interestingly, such high-accretion, <span class="hlt">low-mass</span> BHs behave in many ways like narrow-line Seyfert 1 nuclei (a higher-mass cousin), except that in general the <span class="hlt">low-mass</span> sample is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22004186','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22004186"><span id="translatedtitle">ORGANIC CHEMISTRY OF <span class="hlt">LOW-MASS</span> STAR-FORMING CORES. I. 7 mm SPECTROSCOPY OF CHAMAELEON MMS1</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cordiner, Martin A.; Charnley, Steven B.; Wirstroem, Eva S.; Smith, Robert G.</p> <p>2012-01-10</p> <p>Observations are presented of emission lines from organic molecules at frequencies 32-50 GHz in the vicinity of Chamaeleon MMS1. This chemically rich dense cloud core harbors an extremely young, very low luminosity <span class="hlt">protostellar</span> object and is a candidate first hydrostatic core. Column densities are derived and emission maps are presented for species including polyynes, cyanopolyynes, sulphuretted carbon chains, and methanol. The polyyne emission peak lies about 5000 AU from the protostar, whereas methanol peaks about 15,000 AU away. Averaged over the telescope beam, the molecular hydrogen number density is calculated to be 10{sup 6} cm{sup -3} and the gas kinetic temperature is in the range 5-7 K. The abundances of long carbon chains are very large and are indicative of a non-equilibrium carbon chemistry; C{sub 6}H and HC{sub 7}N column densities are 5.9{sup +2.9}{sub -1.3} Multiplication-Sign 10{sup 11} cm{sup -2} and 3.3{sup +8.0}{sub -1.5} Multiplication-Sign 10{sup 12} cm{sup -2}, respectively, which are similar to the values found in the most carbon-chain-rich protostars and prestellar cores known, and are unusually large for star-forming gas. Column density upper limits were obtained for the carbon-chain anions C{sub 4}H{sup -} and C{sub 6}H{sup -}, with anion-to-neutral ratios [C{sub 4}H{sup -}]/[C{sub 4}H] < 0.02% and [C{sub 6}H{sup -}]/[C{sub 6}H] < 10%, consistent with previous observations in interstellar clouds and <span class="hlt">low-mass</span> protostars. Deuterated HC{sub 3}N and c-C{sub 3}H{sub 2} were detected. The [DC{sub 3}N]/[HC{sub 3}N] ratio of approximately 4% is consistent with the value typically found in cold interstellar gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ATel.5647....1B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ATel.5647....1B"><span id="translatedtitle">A possible state transition in the <span class="hlt">low-mass</span> X-ray binary XSS J12270-4859</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bassa, C. G.; Patruno, A.; Hessels, J. W. T.; Archibald, A. M.; Mahony, E. K.; Monard, B.; Keane, E. F.; Bogdanov, S.; Stappers, B. W.; Janssen, G. H.; Tendulkar, S.</p> <p>2013-12-01</p> <p>Spurred by the recent state change in the "missing link" pulsar binary <span class="hlt">system</span> PSR J1023+0038 (ATel #5513, #5514, #5515, #5516; Stappers et al. 2013, arXiv:1311.7506; Patruno et al. 2013, arXiv:1310.7549) we report on optical, radio, X-ray and gamma-ray observations of the <span class="hlt">low-mass</span> X-ray binary XSS J12270-4859, conducted between 2012 March 29 and 2013 December 10.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AJ....145...16L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AJ....145...16L"><span id="translatedtitle">Physical Properties of the <span class="hlt">Low-mass</span> Eclipsing Binary NSVS 02502726</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Jae Woo; Youn, Jae-Hyuck; Kim, Seung-Lee; Lee, Chung-Uk</p> <p>2013-01-01</p> <p>NSVS 02502726 has been known as a double-lined, detached eclipsing binary that consists of two <span class="hlt">low-mass</span> stars. We obtained BVRI photometric follow-up observations in 2009 and 2011 to measure improved physical properties of the binary star. Each set of light curves, including the 2008 data given by Çakirli et al., was simultaneously analyzed with the previously published radial velocity curves using the Wilson-Devinney binary code. The conspicuous seasonal light variations of the <span class="hlt">system</span> are satisfactorily modeled by a two-spot model with one starspot on each component and by changes of the spot parameters with time. Based on 23 eclipse timings calculated from the synthetic model and one ephemeris epoch, an orbital period study of NSVS 02502726 reveals that the period has experienced a continuous decrease of -5.9 × 10-7 day yr-1 or a sinusoidal variation with a period and semi-amplitude of 2.51 yr and 0.0011 days, respectively. The timing variations could be interpreted as either the light-travel-time effect due to the presence of an unseen third body, or as the combination of this effect and angular momentum loss via magnetic stellar wind braking. Individual masses and radii of both components are determined to be M 1 = 0.689 ± 0.016 M ⊙, M 2 = 0.341 ± 0.009 M ⊙, R 1 = 0.707 ± 0.007 R ⊙, and R 2 = 0.657 ± 0.008 R ⊙. The results are very different from those of Çakirli et al. with the primary's radius (0.674 ± 0.006 R ⊙) smaller the secondary's (0.763 ± 0.007 R ⊙). We compared the physical parameters presented in this paper with current <span class="hlt">low-mass</span> stellar models and found that the measured values of the primary star are best fitted to a 79 Myr isochrone. The primary is in good agreement with the empirical mass-radius relation from <span class="hlt">low-mass</span> binaries, but the secondary is oversized by about 85%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009PhDT.........7D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009PhDT.........7D&link_type=ABSTRACT"><span id="translatedtitle">Constraining the coevolution of galaxies and black holes at <span class="hlt">low</span> <span class="hlt">mass</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Desroches, Louis-Benoit</p> <p>2009-06-01</p> <p> present results from reverberation mapping, a technique that is used to estimate the mass of the central BH ( M BH ). We estimate M BH [approximate] 3 × 10^5 [Special characters omitted.] , consistent with another reverberation result based on simultaneous UV observations. In Chapter 4, we present an archival study of Chandra X-ray Telescope data, in which we search for AGN signatures in a population of bulgeless or nearly- bulgeless late-type spiral galaxies. Motivated by the case of NGC 4395, it is unclear how many BHs exist in bulgeless <span class="hlt">systems</span>. Optical studies are notoriously poorly suited for this task, since BHs in such late-type spirals are likely of <span class="hlt">low</span> <span class="hlt">mass</span> (since the host galaxy is equally of <span class="hlt">low</span> <span class="hlt">mass</span>) and thus have very weak AGN signatures. In addition, late-type spirals have relatively large amounts of circumnuclear gas and dust, which easily obscures optical radiation. X-ray photons are largely unaffected (excluding exceptionally large columns of gas) and are therefore a more reliable indicator of central AGN activity (even weak, radiatively inefficient accretion). Unfortunately, stellar-mass BH binaries are equally capable of producing such X-ray emission, and we lack the depth, spacial resolution, and sensitivity to make a definitive identification. Based on nuclear stellar densities and the probability of finding an X-ray binary, we still conclude that roughly ~20-25% of bulgeless galaxies host an AGN, implying that objects such as NGC 4395 are not as rare as once thought. Finally, in Chapter 5, we present a comprehensive X-ray study of a large sample of intermediate-mass BHs discovered in SDSS via optical identification of broad emission lines. Such BHs, while sampling a mass regime that is poorly understood, are biased toward high accretion rates to make them optically identifiable. Interestingly, such high-accretion, <span class="hlt">low-mass</span> BHs behave in many ways like narrow-line Seyfert 1 nuclei (a higher-mass cousin), except that in general the <span class="hlt">low-mass</span> sample is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22364906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22364906"><span id="translatedtitle"><span class="hlt">PROTOSTELLAR</span> JETS ENCLOSED BY LOW-VELOCITY OUTFLOWS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Machida, Masahiro N.</p> <p>2014-11-20</p> <p>A <span class="hlt">protostellar</span> jet and outflow are calculated for ∼270 yr following the protostar formation using a three-dimensional magnetohydrodynamics simulation, in which both the protostar and its parent cloud are spatially resolved. A high-velocity (∼100 km s{sup –1}) jet with good collimation is driven near the disk's inner edge, while a low-velocity (≲ 10 km s{sup –1}) outflow with a wide opening angle appears in the outer-disk region. The high-velocity jet propagates into the low-velocity outflow, forming a nested velocity structure in which a narrow high-velocity flow is enclosed by a wide low-velocity flow. The low-velocity outflow is in a nearly steady state, while the high-velocity jet appears intermittently. The time-variability of the jet is related to the episodic accretion from the disk onto the protostar, which is caused by gravitational instability and magnetic effects such as magnetic braking and magnetorotational instability. Although the high-velocity jet has a large kinetic energy, the mass and momentum of the jet are much smaller than those of the low-velocity outflow. A large fraction of the infalling gas is ejected by the low-velocity outflow. Thus, the low-velocity outflow actually has a more significant effect than the high-velocity jet in the very early phase of the star formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2256706G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2256706G"><span id="translatedtitle">A project to unveil the population of <span class="hlt">Low-Mass</span> Star-Forming Galaxies of the Universe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, Jesus; Rodriguez-Muñoz, Lucía; Tresse, Laurence; Pacifici, Camilla; Charlot, Stéphane; Gil de Paz, Armando; Gomez-Guijarro, Carlos; Villar, Víctor; Barro, Guillermo</p> <p>2015-08-01</p> <p>Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that <span class="hlt">low-mass</span> <span class="hlt">systems</span> merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf <span class="hlt">systems</span> might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of <span class="hlt">low-mass</span> <span class="hlt">systems</span> at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of <span class="hlt">low-mass</span> dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present constraints on the star formation histories (SFHs) of a sample of <span class="hlt">low-mass</span> Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFHs were obtained through the analysis of their spectral energy distributions using a novel approach (Pacifici et al. 2012) that (1) consistently combines photometric (HST and ground-based multi-broadband) and spectroscopic (equivalent widths of emission lines from VLT and GTC spectroscopy) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time.The median SFH of our LMSFGs appears to form 90% of the median stellar mass inferred for the sample in the ˜0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for dwarf SFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for a slightly more massive secondary sample 8.0 < log M∗/Mo < 9.1).This is a pilot study for future surveys on dwarf galaxies at high redshift.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.443.3033R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.443.3033R"><span id="translatedtitle">Champagne flutes and brandy snifters: modelling <span class="hlt">protostellar</span> outflow-cloud chemical interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rollins, R. P.; Rawlings, J. M. C.; Williams, D. A.; Redman, M. P.</p> <p>2014-10-01</p> <p>A rich variety of molecular species has now been observed towards hot cores in star-forming regions and in the interstellar medium. An increasing body of evidence from millimetre interferometers suggests that many of these form at the interfaces between <span class="hlt">protostellar</span> outflows and their natal molecular clouds. However, current models have remained unable to explain the origin of the observational bias towards wide-angled `brandy snifter' shaped outflows over narrower `champagne flute' shapes in carbon monoxide imaging. Furthermore, these wide-angled <span class="hlt">systems</span> exhibit unusually high abundances of the molecular ion HCO+. We present results from a chemodynamic model of such regions where a rich chemistry arises naturally as a result of turbulent mixing between cold, dense molecular gas and the hot, ionized outflow material. The injecta drives a rich and rapid ion-neutral chemistry in qualitative and quantitative agreement with the observations. The observational bias towards wide-angled outflows is explained naturally by the geometry-dependent ion injection rate causing rapid dissociation of CO in the younger <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22721001M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22721001M"><span id="translatedtitle">Fundmental Parameters of <span class="hlt">Low-Mass</span> Stars, Brown Dwarfs, and Planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montet, Benjamin; Johnson, John A.; Bowler, Brendan; Shkolnik, Evgenya</p> <p>2016-01-01</p> <p>Despite advances in evolutionary models of <span class="hlt">low-mass</span> stars and brown dwarfs, these models remain poorly constrained by observations. In order to test these predictions directly, masses of individual stars must be measured and combined with broadband photometry and medium-resolution spectroscopy to probe stellar atmospheres. I will present results from an astrometric and spectroscopic survey of <span class="hlt">low-mass</span> pre-main sequence binary stars to measure individual dynamical masses and compare to model predictions. This is the first systematic test of a large number of stellar <span class="hlt">systems</span> of intermediate age between young star-forming regions and old field stars. Stars in our sample are members of the Tuc-Hor, AB Doradus, and beta Pictoris moving groups, the last of which includes GJ 3305 AB, the wide binary companion to the imaged exoplanet host 51 Eri. I will also present results of Spitzer observations of secondary eclipses of LHS 6343 C, a T dwarf transiting one member of an M+M binary in the Kepler field. By combining these data with Kepler photometry and radial velocity observations, we can measure the luminosity, mass, and radius of the brown dwarf. This is the first non-inflated brown dwarf for which all three of these parameters have been measured, providing the first benchmark to test model predictions of the masses and radii of field T dwarfs. I will discuss these results in the context of K2 and TESS, which will find additional benchmark transiting brown dwarfs over the course of their missions, including a description of the first planet catalog developed from K2 data and a program to search for transiting planets around mid-M dwarfs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........56M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........56M"><span id="translatedtitle">Investigating <span class="hlt">Low-Mass</span> Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mace, Gregory Nathan</p> <p></p> <p>The mass of a star at formation determines its subsequent evolution and demise. <span class="hlt">Low-mass</span> stars are the most common products of star formation and their long main-sequence lifetimes cause them to accumulate over time. Star formation also produces many substellar-mass objects known as brown dwarfs, which emerge from their natal molecular clouds and continually cool as they age, pervading the Milky Way. <span class="hlt">Low-mass</span> stars and brown dwarfs exhibit a wide range of physical characteristics and their abundance make them ideal subjects for testing formation and evolution models. I have examined a pair of pre-main sequence spectroscopic binaries and used radial velocity variations to determine orbital solutions and mass ratios. Additionally, I have employed synthetic spectra to estimate their effective temperatures and place them on theoretical Hertzsprung-Russell diagrams. From this analysis I discuss the formation and evolution of young binary <span class="hlt">systems</span> and place bounds on absolute masses and radii. I have also studied the late-type T dwarfs revealed by the Wide-field Infrared Survey Explorer (WISE). This includes the exemplar T8 subdwarf Wolf 1130C, which has the lowest inferred metallicity in the literature and spectroscopic traits consistent with old age. Comparison to synthetic spectra implies that the dispersion in near-infrared colors of late-type T dwarfs is a result of age and/or thin sulfide clouds. With the updated census of the L, T, and Y dwarfs we can now study specific brown dwarf subpopulations. Finally, I present a number of future studies that would develop our understanding of the physical qualities of T dwarf color outliers and disentangle the tracers of age and atmospheric properties.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100033065','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100033065"><span id="translatedtitle"><span class="hlt">Low</span> <span class="hlt">Mass</span> Printable Devices for Energy Capture, Storage, and Use for Space Exploration Missions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frazier, Donald O.; Singer, Christopher E.; Ray, William J.; Fuller, Kirk A.</p> <p>2010-01-01</p> <p>The energy-efficient, environmentally friendly technology that will be presented is the result of a Space Act Agreement between -Technologies Worldwide, Inc., and the National Aeronautics and Space Administration s (NASA s) Marshall Space Flight Center (MSFC). This work combines semiconductor and printing technologies to advance lightweight electronic and photonic devices having excellent potential for commercial and exploration applications, and is an example of industry and government cooperation that leads to novel inventions. Device development involves three energy generation and consumption projects: 1) a <span class="hlt">low</span> <span class="hlt">mass</span> efficient (low power, low heat emission) micro light-emitting diode (LED) area lighting device; 2) a <span class="hlt">low-mass</span> omni-directional efficient photovoltaic (PV) device with significantly improved energy capture; and 3) a new approach to building supercapacitors. These three technologies - energy capture, storage, and usage (e.g., lighting) - represent a systematic approach for building efficient local micro-grids that are commercially feasible; furthermore, these same technologies will be useful for lightweight power generation that enables inner planetary missions using smaller launch vehicles and facilitates surface operations. The PV device model is a two-sphere, light-trapped sheet approximately 2-mm thick. The model suggests a significant improvement over current thin film <span class="hlt">systems</span>. All three components may be printed in line by printing sequential layers on a standard screen or flexographic direct impact press using the threedimensional printing technique (3DFM) patented by NthDegree. MSFC is testing the robustness of prototype devices in the harsh space and lunar surface environments, and available results will be reported. Unlike many traditional light sources, this device does not contain toxic compounds, and the LED component has passed stringent off-gassing tests required for potential manifesting on spacecraft such as the International Space</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012A%26A...542L...5P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012A%26A...542L...5P"><span id="translatedtitle">Detection of OD towards the <span class="hlt">low-mass</span> protostar IRAS 16293-2422</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parise, B.; Du, F.; Liu, F.-C.; Belloche, A.; Wiesemeyer, H.; Güsten, R.; Menten, K. M.; Hübers, H.-W.; Klein, B.</p> <p>2012-06-01</p> <p>Context. Although water is an essential and widespread molecule in star-forming regions, its chemical formation pathways are still not very well constrained. Observing the level of deuterium fractionation of OH, a radical involved in the water chemical network, is a promising way to infer its chemical origin. Aims: We aim at understanding the formation mechanisms of water by investigating the origin of its deuterium fractionation. This can be achieved by observing the abundance of OD towards the <span class="hlt">low-mass</span> protostar IRAS 16293-2422, where the HDO distribution is already known. Methods: Using the GREAT receiver on board SOFIA, we observed the ground-state OD transition at 1391.5 GHz towards the <span class="hlt">low-mass</span> protostar IRAS 16293-2422. We also present the detection of the HDO 111-000 line using the APEX telescope. We compare the OD/HDO abundance ratio inferred from these observations with the predictions of chemical models. Results: The OD line is detected in absorption towards the source continuum. This is the first detection of OD outside the solar <span class="hlt">system</span>. The SOFIA observation, coupled to the observation of the HDO 111-000 line, provides an estimate of the abundance ratio OD/HDO ~ 17-90 in the gas where the absorption takes place. This value is fairly high compared with model predictions. This may be reconciled if reprocessing in the gas by means of the dissociative recombination of H2DO+ further fractionates OH with respect to water. Conclusions: The present observation demonstrates the capability of the SOFIA/GREAT instrument to detect the ground transition of OD towards star-forming regions in a frequency range that was not accessible before. Dissociative recombination of H2DO+ may play an important role in setting a high OD abundance. Measuring the branching ratios of this reaction in the laboratory will be of great value for chemical models. Figure 5 is available in electronic form at http://www.aanda.org</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.453.2378M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.453.2378M"><span id="translatedtitle">Discovery of a <span class="hlt">low-mass</span> companion to the F7V star HD 984</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meshkat, T.; Bonnefoy, M.; Mamajek, E. E.; Quanz, S. P.; Chauvin, G.; Kenworthy, M. A.; Rameau, J.; Meyer, M. R.; Lagrange, A.-M.; Lannier, J.; Delorme, P.</p> <p>2015-11-01</p> <p>We report the discovery of a <span class="hlt">low-mass</span> companion to the nearby (d = 47 pc) F7V star HD 984. The companion is detected 0.19 arcsec away from its host star in the L' band with the Apodized Phase Plate on NaCo/Very Large Telescope and was recovered by L'-band non-coronagraphic imaging data taken a few days later. We confirm the companion is comoving with the star with SINFONI integral field spectrograph H + K data. We present the first published data obtained with SINFONI in pupil-tracking mode. HD 984 has been argued to be a kinematic member of the 30 Myr-old Columba group, and its HR diagram position is not altogether inconsistent with being a zero-age main sequence star of this age. By consolidating different age indicators, including isochronal age, coronal X-ray emission, and stellar rotation, we independently estimate a main-sequence age of 115 ± 85 Myr (95 per cent CL) which does not rely on this kinematic association. The mass of directly imaged companions are usually inferred from theoretical evolutionary tracks, which are highly dependent on the age of the star. Based on the age extrema, we demonstrate that with our photometric data alone, the companion's mass is highly uncertain: between 33 and 96 MJup (0.03-0.09 M⊙) using the COND evolutionary models. We compare the companion's SINFONI spectrum with field dwarf spectra to break this degeneracy. Based on the slope and shape of the spectrum in the H band, we conclude that the companion is an M6.0 ± 0.5 dwarf. The age of the <span class="hlt">system</span> is not further constrained by the companion, as M dwarfs are poorly fit on <span class="hlt">low-mass</span> evolutionary tracks. This discovery emphasizes the importance of obtaining a spectrum to spectral type companions around F-stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015hsa8.conf..370G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015hsa8.conf..370G&link_type=ABSTRACT"><span id="translatedtitle">Physical properties of <span class="hlt">low-mass</span> star-forming galaxies at intermediate redshifts (z <1)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, J.; Rodríguez-Muñoz, L.; Pacifici, C.; Tresse, L.; Charlot, S.; Gil de Paz, A.; Barro, G.; Villar, V.</p> <p>2015-05-01</p> <p>In this poster we present the physical properties of a sample of <span class="hlt">low-mass</span> star-forming galaxies at intermediate redshifts (z<1). We selected a population of dwarf galaxies because dwarf galaxies play a key role in galaxy formation and evolution: (1) they resemble the first structures that hierarchical models predict to form first in the Universe (Dekel & Silk 1986) and that are responsible for the reionization process (Bouwens et al. 2012); and (2) the way or epoch they form and how they evolve are still open questions of modern astrophysics. We selected the sample on the CDFS field. Photometry (40 bands, from UV to far-IR) and preliminary photometric redshifts and stellar masses were obtained from RAINBOW database (Pérez-González et al. 2008). Morphology fom Griffith et al. (2012). Main selection was done by stellar mass, selecting those galaxies with stellar mass M_*<10^8 {M}_⊙. Spectroscopic redshifts were obtained from deep (4 h) MOS spectroscopy with the VIMOS spectrograph at VLT. The average spectrum is characterized by a faint, blue and flat continuum and strong emission lines, revealing that the <span class="hlt">systems</span> are dominated by an undergoing star formation burst. SFRs and stellar masses are consistent with the SF main-squence over a 2 dex range. More massive objects show higher SFRs than <span class="hlt">low-mass</span> objects, following the SF main sequence. Distant dwarfs and BCDs follow the overall star-forming sequence in the excitation-luminosity diagram, populating the high excitation, low metallicity and high strength region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ApJ...757L...9C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ApJ...757L...9C&link_type=ABSTRACT"><span id="translatedtitle">The Herschel and IRAM CHESS Spectral Surveys of the <span class="hlt">Protostellar</span> Shock L1157-B1: Fossil Deuteration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Codella, C.; Ceccarelli, C.; Lefloch, B.; Fontani, F.; Busquet, G.; Caselli, P.; Kahane, C.; Lis, D.; Taquet, V.; Vasta, M.; Viti, S.; Wiesenfeld, L.</p> <p>2012-09-01</p> <p>We present the first study of deuteration toward the <span class="hlt">protostellar</span> shock L1157-B1, based on spectral surveys performed with the Herschel-HIFI and IRAM 30 m telescopes. The L1157 outflow is driven by a <span class="hlt">low-mass</span> Class 0 protostar and is considered the prototype of the so-called chemically active outflows. The young (2000 yr), bright blueshifted bow shock, B1, is an ideal laboratory for studying the gas chemically enriched by the release of dust mantles due to the passage of a shock. A total of 12 emission lines (up to E u = 63 K) of CH2DOH, HDCO, and DCN are detected. In addition, two lines of NH2D and HDO are tentatively reported. To estimate the deuteration, we also extracted from our spectral survey emission lines of non-deuterated isotopologues (13CH3OH, H2 13CO, H13CN, H2 13CO, and NH3). We infer higher deuteration fractions for CH3OH (D/H = 0.2-2 × 10-2) and H2CO (5-8 × 10-3) than for H2O (0.4-2 × 10-3), HCN (~10-3), and ammonia (<=3 × 10-2). The measurement of deuteration of water, formaldehyde, and methanol in L1157-B1 provides a fossil record of the gas before it was shocked by the jet driven by the protostar. A comparison with gas-grain models indicates that the gas passed through a low-density (<=103 cm-3) phase, during which the bulk of water ices formed, followed by a phase of increasing density, up to 3 × 104 cm-3, during which formaldehyde and methanol ices formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997A%26A...319..547S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997A%26A...319..547S"><span id="translatedtitle"><span class="hlt">Protostellar</span> binary fragmentation: a comparison of results from two distinct second-order hydrodynamic codes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigalotti, L. Di G.; Klapp, J.</p> <p>1997-03-01</p> <p>A new second-order Eulerian code is compared with a version of the TREESPH code formulated by Hernquist and Katz (1989) for the standard isothermal collapse test. The results indicate that both codes produce a very similar evolution ending with the formation of a <span class="hlt">protostellar</span> binary <span class="hlt">system</span>. Contrary to previous first-order calculations, the binary forms by direct fragmentation, i.e. without the occurrence of an intermediate bar configuration. A similar trend was also found in second-order Eulerian calculations (Myhill and Boss 1993), suggesting that it is a result of the decreased numerical diffusion associated with the new second-order schemes. The results have also implications on the differences between the finite difference methods and the particle method SPH, raised by Monaghan and Lattanzio (1986) for this problem. In particular, the Eulerian calculation does not result in a run-away collapse of the fragments, and as found in the TREESPH evolution, they also show a clear tendency to get closer together. In agreement with previous SPH calculations (Monaghan and Lattanzio 1986), the results of the long term evolution with code TREESPH show that the gravitational interaction between the two fragments may become important, and eventually induce the binary to coalesce. However, SPH calculations by Bate, Bonnell and Price (1995) indicate that the two fragments, after having reached a minimum separation distance, do not merge but continue to orbit each other.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007075','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007075"><span id="translatedtitle">A Self-Perpetuating Catalyst for the Production of Complex Organic Molecules in <span class="hlt">Protostellar</span> Nebulae</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nuth, Joseph A.; Johnson, N. M.</p> <p>2010-01-01</p> <p>The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar <span class="hlt">systems</span>. Many mechanisms may contribute to the total organic content in <span class="hlt">protostellar</span> nebulae, ranging from organics formed via ion-molecule and atom-molecule reactions in the cold dark clouds from which such nebulae collapse, to similar ion-molecule and atom-molecule reactions in the dark regions of the nebula far from the proto star, to gas phase reactions in sub-nebulae around growing giant planets and in the nebulae themselves. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. The Haber-Bosch catalytic reduction of N2 by hydrogen was thought to produce the reduced nitrogen found in meteorites. However, the clean iron metal surfaces that catalyze these reactions are easily poisoned via reaction with any number of molecules, including the very same complex organics that they produce and both reactions work more efficiently in the hot regions of the nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Although none work as well as pure iron grains, and all produce a wide range of organic products rather than just pure methane, these materials are not truly catalysts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AAS...22324417S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AAS...22324417S"><span id="translatedtitle">The First Stars: A <span class="hlt">Low-Mass</span> Formation Mode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stacy, Athena</p> <p>2014-01-01</p> <p>We perform numerical simulations of the growth of a Population III stellar <span class="hlt">system</span> under photodissociating feedback. We start from cosmological initial conditions at z=100, self-consistently following the formation of a minihalo at z=15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as ~ 1 AU, corresponding to gas densities of 10^16 cm^-3. Using sink particles to represent the growing protostars, we evolve the stellar <span class="hlt">system</span> for the next 5000 years. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z=20-30), or with lower baryonic angular momentum. The stars in this unusual <span class="hlt">system</span> will likely reach masses ranging from < 1 M_sol to ~ 5 M_sol by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the existence of Populatio III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...785...73S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...785...73S"><span id="translatedtitle">The First Stars: A <span class="hlt">Low-mass</span> Formation Mode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stacy, Athena; Bromm, Volker</p> <p>2014-04-01</p> <p>We perform numerical simulations of the growth of a Population III stellar <span class="hlt">system</span> under photodissociating feedback. We start from cosmological initial conditions at z = 100, self-consistently following the formation of a minihalo at z = 15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as ~1 AU, corresponding to gas densities of 1016 cm-3. Using sink particles to represent the growing protostars, we evolve the stellar <span class="hlt">system</span> for the next 5000 yr. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z = 20-30), or with lower baryonic angular momentum. The stars in this unusual <span class="hlt">system</span> will likely reach masses ranging from <1 M ⊙ to ~5 M ⊙ by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the rare existence of Population III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140016977','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140016977"><span id="translatedtitle">The First Stars: A <span class="hlt">Low-Mass</span> Formation Mode</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stacy, Athena; Bromm, Volker</p> <p>2014-01-01</p> <p>We perform numerical simulations of the growth of a Population III stellar <span class="hlt">system</span> under photodissociating feedback. We start from cosmological initial conditions at z = 100, self-consistently following the formation of a minihalo at z = 15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as approx. 1 AU, corresponding to gas densities of 10(exp 16)/cu cm. Using sink particles to represent the growing protostars, we evolve the stellar <span class="hlt">system</span> for the next 5000 yr. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z = 20-30), or with lower baryonic angular momentum. The stars in this unusual <span class="hlt">system</span> will likely reach masses ranging from <1Stellar Mass to approx. 5 Stellar Mass by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the rare existence of Population III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22357137','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22357137"><span id="translatedtitle">The first stars: A <span class="hlt">low-mass</span> formation mode</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stacy, Athena; Bromm, Volker</p> <p>2014-04-10</p> <p>We perform numerical simulations of the growth of a Population III stellar <span class="hlt">system</span> under photodissociating feedback. We start from cosmological initial conditions at z = 100, self-consistently following the formation of a minihalo at z = 15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as ∼1 AU, corresponding to gas densities of 10{sup 16} cm{sup –3}. Using sink particles to represent the growing protostars, we evolve the stellar <span class="hlt">system</span> for the next 5000 yr. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z = 20-30), or with lower baryonic angular momentum. The stars in this unusual <span class="hlt">system</span> will likely reach masses ranging from <1 M {sub ☉} to ∼5 M {sub ☉} by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the rare existence of Population III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...587A..75D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...587A..75D"><span id="translatedtitle">Proper motions of embedded <span class="hlt">protostellar</span> jets in Serpens</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Djupvik, A. A.; Liimets, T.; Zinnecker, H.; Barzdis, A.; Rastorgueva-Foi, E. A.; Petersen, L. R.</p> <p>2016-03-01</p> <p>Aims: We determine the proper motion of <span class="hlt">protostellar</span> jets around Class 0 and Class I sources in an active star forming region in Serpens. Methods: Multi-epoch deep images in the 2.122 μm line of molecular hydrogen, v = 1-0 S(1), obtained with the near-infrared instrument NOTCam on a timescale of 10 years, are used to determine the proper motion of knots and jets. K-band spectroscopy of the brighter knots is used to supply radial velocities, estimate extinction, excitation temperature, and H2 column densities towards these knots. Results: We measure the proper motion of 31 knots on different timescales (2, 4, 6, 8, and 10 years). The typical tangential velocity is around 50 km s-1 for the 10-year baseline, but for shorter timescales, a maximum tangential velocity up to 300 km s-1 is found for a few knots. Based on morphology, velocity information, and the locations of known protostars, we argue for the existence of at least three partly overlapping and deeply embedded flows, one Class 0 flow and two Class I flows. The multi-epoch proper motion results indicate time-variable velocities of the knots, for the first time directly measured for a Class 0 jet. We find in general higher velocities for the Class 0 jet than for the two Class I jets. While the bolometric luminosites of the three driving sources are about equal, the derived mass flow rate Ṁout is two orders of magnitude higher in the Class 0 flow than in the two Class I flows. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22011958','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22011958"><span id="translatedtitle">RAPID MID-INFRARED VARIABILITY IN <span class="hlt">PROTOSTELLAR</span> DISKS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ke, T. T.; Huang, H.; Lin, D. N. C.</p> <p>2012-01-20</p> <p>Spectral energy distribution (SED) in <span class="hlt">protostellar</span> disks is determined by the disks' internal dissipation and reprocessing of irradiation from their host stars. Around T Tauri stars, most mid-infrared (MIR) radiation (in a wavelength range from a few to a few tens of {mu}m) emerges from regions around a fraction to a few AU. This region is interesting because it contains both the habitable zone and the snow line. Recent observations reveal SED variations in the MIR wavelength range. These variations are puzzling because they occur on a timescale (a few days) which is much shorter than the dynamical (months to years) timescale from 1 AU to a few AU. They are probably caused by shadows cast by inner onto outer disk regions. Interaction between disks and their misaligned magnetized host stars can lead to warped structure and periodic SED modulations. Rapid aperiodic SED variations may also be induced by observed X-ray flares from T Tauri stars. These flares can significantly modulate the ionization fraction of the gas and the net charge carried by the grains near the surface of the inner disk. The newly charged grains may be accelerated by the stellar or disk magnetic field and adjust their distances from the midplane. Shadows cast by these grains attenuate the flux of stellar photons irradiated onto regions at several AU from the central stars. We use this model to account for the observed rapid aperiodic SED variabilities. We suggest that regular monitoring of SED variations will not only provide valuable information on the distribution of the disk aspect ratio near the habitable zone but also provide a probe of the interaction between the inner regions of the disk with the magnetosphere of their host stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22004218','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22004218"><span id="translatedtitle">FIRST DETECTION OF HYDROGEN CHLORIDE TOWARD <span class="hlt">PROTOSTELLAR</span> SHOCKS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Codella, C.; Vasta, M.; Ceccarelli, C.; Lefloch, B.; Faure, A.; Wiesenfeld, L.; Salez, M.; Cabrit, S.; Viti, S.</p> <p>2012-01-10</p> <p>We present the first detection of hydrogen chloride in a <span class="hlt">protostellar</span> shock by observing the fundamental transition at 626 GHz with the HIFI spectrometer. We detected two of the three hyperfine lines from which we derived a line opacity {<=}1. Using a non-local thermodynamic equilibrium large velocity gradient code, we constrained the HCl column density, temperature, and density of the emitting gas. The hypothesis that the emission originates in the molecular cloud is ruled out because it would imply a very dense gas. Conversely, assuming that the emission originates in the 10''-15'' size shocked gas previously observed at the IRAM Plateau de Bure Interferometer, we obtain N(HCl) = 0.7-2 Multiplication-Sign 10{sup 13} cm{sup -2}, temperature >15 K, and density >3 Multiplication-Sign 10{sup 5} cm{sup -3}. Combining these with the Herschel HIFI CO(5-4) observations allows us to further constrain the gas density and temperature, 10{sup 5}-10{sup 6} cm{sup -3} and 120-250 K, respectively, as well as the HCl column density, 2 Multiplication-Sign 10{sup 13} cm{sup -2}, and, finally, the abundance {approx}3-6 Multiplication-Sign 10{sup -9}. The estimated HCl abundance is consistent with that previously observed in low- and high-mass protostars. This puzzling result in the L1157-B1 shock, where species from volatile and refractory grain components are enhanced, suggests either that HCl is not the main reservoir of chlorine in the gas phase, which goes against previous chemical model predictions, or that the elemental chlorine abundance is low in L1157-B1. Astrochemical modeling suggests that HCl is in fact formed in the gas phase at low temperatures prior to the occurrence of the shock; the latter does not enhance its abundance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17833316','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17833316"><span id="translatedtitle">A carbonate-rich, hydrated, interplanetary dust particle: possible residue from <span class="hlt">protostellar</span> clouds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tomeoka, K; Buseck, P R</p> <p>1986-03-28</p> <p>Transmission electron microscopy of a hydrated interplanetary dust particle (IDP) indicates that it contains abundant magnesium-iron carbonates, primarily breunnerite and magnesian siderite. This IDP displays a strong absorption band at 6.8 micrometers in its infrared spectrum, similar to that in certain <span class="hlt">protostellar</span> spectra. The carbonates probably account for the 6.8-micrometer band in the IDP spectrum, suggesting that carbonate also may occur in interstellar dust and be the source of the controversial 6.8-micrometer feature from the <span class="hlt">protostellar</span> spectra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22521834','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22521834"><span id="translatedtitle">FRIENDS OF HOT JUPITERS. III. AN INFRARED SPECTROSCOPIC SEARCH FOR <span class="hlt">LOW-MASS</span> STELLAR COMPANIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Piskorz, Danielle; Knutson, Heather A.; Ngo, Henry; Batygin, Konstantin; Muirhead, Philip S.; Crepp, Justin R.; Hinkley, Sasha; Morton, Timothy D.</p> <p>2015-12-01</p> <p>Surveys of nearby field stars indicate that stellar binaries are common, yet little is known about the effects that these companions may have on planet formation and evolution. The Friends of Hot Jupiters project uses three complementary techniques to search for stellar companions to known planet-hosting stars: radial velocity monitoring, adaptive optics imaging, and near-infrared spectroscopy. In this paper, we examine high-resolution K band infrared spectra of fifty stars hosting gas giant planets on short-period orbits. We use spectral fitting to search for blended lines due to the presence of cool stellar companions in the spectra of our target stars, where we are sensitive to companions with temperatures between 3500 and 5000 K and projected separations less than 100 AU in most <span class="hlt">systems</span>. We identify eight <span class="hlt">systems</span> with candidate <span class="hlt">low-mass</span> companions, including one companion that was independently detected in our AO imaging survey. For <span class="hlt">systems</span> with radial velocity accelerations, a spectroscopic non-detection rules out scenarios involving a stellar companion in a high inclination orbit. We use these data to place an upper limit on the stellar binary fraction at small projected separations, and show that the observed population of candidate companions is consistent with that of field stars and also with the population of wide-separation companions detected in our previous AO survey. We find no evidence that spectroscopic stellar companions are preferentially located in <span class="hlt">systems</span> with short-period gas giant planets on eccentric and/or misaligned orbits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21367475','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21367475"><span id="translatedtitle">STATE TRANSITIONS IN <span class="hlt">LOW-MASS</span> X-RAY BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bradley, Charles K.; Frank, Juhan</p> <p>2009-10-10</p> <p>We investigate the model of disk/coronal accretion into a black hole. We show that the inner regions of an accretion disk in X-ray binaries can transform from a cool standard disk to an advection-dominated flow through the known properties of Coulomb interaction in a two-temperature plasma, viscous heating, radiative processes, and thermal conduction. A hot, diffuse corona covering the disk is powered by accretion, but it exchanges mass with the underlying cold disk. If the accretion rate in the <span class="hlt">system</span> is low enough, we show that the corona evaporates the disk away, leaving an advective flow to continue toward the hole. In the soft/hard transition commonly seen in X-ray binaries, we show that this advective flow can recondense back onto the underlying disk if the change in the <span class="hlt">system</span>'s accretion rate is slow enough due to thermal conduction. Unabsorbed spectra are produced to test against observations as well as prediction of the location of truncation radii of the accretion disk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22121879','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22121879"><span id="translatedtitle">UNVEILING THE EVOLUTIONARY SEQUENCE FROM INFALLING ENVELOPES TO KEPLERIAN DISKS AROUND <span class="hlt">LOW-MASS</span> PROTOSTARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yen, Hsi-Wei; Takakuwa, Shigehisa; Ohashi, Nagayoshi; Ho, Paul T. P.</p> <p>2013-07-20</p> <p>We performed Submillimeter Array observations in the C{sup 18}O (2-1) emission line toward six Class 0 and I protostars to study rotational motions of their surrounding envelopes and circumstellar material on 100-1000 AU scales. C{sup 18}O (2-1) emission with intensity peaks located at the <span class="hlt">protostellar</span> positions is detected toward all six sources. The rotational velocities of the <span class="hlt">protostellar</span> envelopes as a function of radius were measured from the position-velocity diagrams perpendicular to the outflow directions passing through the <span class="hlt">protostellar</span> positions. Two Class 0 sources, B335 and NGC 1333 IRAS 4B, show no detectable rotational motion, while L1527 IRS (Class 0/I) and L1448-mm (Class 0) exhibit rotational motions with radial profiles of V{sub rot}{proportional_to}r {sup -1.0{+-}0.2} and {proportional_to}r {sup -1.0{+-}0.1}, respectively. The other Class I sources, TMC-1A and L1489 IRS, exhibit the fastest rotational motions among the sample, and their rotational motions have flatter radial profiles of V{sub rot}{proportional_to}r {sup -0.6{+-}0.1} and {proportional_to}r {sup -0.5{+-}0.1}, respectively. The rotational motions with the radial dependence of {approx}r {sup -1} can be interpreted as rotation with a conserved angular momentum in a dynamically infalling envelope, while those with the radial dependence of {approx}r {sup -0.5} can be interpreted as Keplerian rotation. These observational results demonstrate categorization of rotational motions from infalling envelopes to Keplerian-disk formation. Models of the inside-out collapse where the angular momentum is conserved are discussed and compared with our observational results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013A%26A...551A..98L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013A%26A...551A..98L&link_type=ABSTRACT"><span id="translatedtitle">The Earliest Phases of Star Formation (EPoS): a Herschel key project. The thermal structure of <span class="hlt">low-mass</span> molecular cloud cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Launhardt, R.; Stutz, A. M.; Schmiedeke, A.; Henning, Th.; Krause, O.; Balog, Z.; Beuther, H.; Birkmann, S.; Hennemann, M.; Kainulainen, J.; Khanzadyan, T.; Linz, H.; Lippok, N.; Nielbock, M.; Pitann, J.; Ragan, S.; Risacher, C.; Schmalzl, M.; Shirley, Y. L.; Stecklum, B.; Steinacker, J.; Tackenberg, J.</p> <p>2013-03-01</p> <p>Context. The temperature and density structure of molecular cloud cores are the most important physical quantities that determine the course of the <span class="hlt">protostellar</span> collapse and the properties of the stars they form. Nevertheless, density profiles often rely either on the simplifying assumption of isothermality or on observationally poorly constrained model temperature profiles. The instruments of the Herschel satellite provide us for the first time with both the spectral coverage and the spatial resolution that is needed to directly measure the dust temperature structure of nearby molecular cloud cores. Aims: With the aim of better constraining the initial physical conditions in molecular cloud cores at the onset of <span class="hlt">protostellar</span> collapse, in particular of measuring their temperature structure, we initiated the guaranteed time key project (GTKP) "The Earliest Phases of Star Formation" (EPoS) with the Herschel satellite. This paper gives an overview of the <span class="hlt">low-mass</span> sources in the EPoS project, the Herschel and complementary ground-based observations, our analysis method, and the initial results of the survey. Methods: We study the thermal dust emission of 12 previously well-characterized, isolated, nearby globules using FIR and submm continuum maps at up to eight wavelengths between 100 μm and 1.2 mm. Our sample contains both globules with starless cores and embedded protostars at different early evolutionary stages. The dust emission maps are used to extract spatially resolved SEDs, which are then fit independently with modified blackbody curves to obtain line-of-sight-averaged dust temperature and column density maps. Results: We find that the thermal structure of all globules (mean mass 7 M⊙) is dominated by external heating from the interstellar radiation field and moderate shielding by thin extended halos. All globules have warm outer envelopes (14-20 K) and colder dense interiors (8-12 K) with column densities of a few 1022 cm-2. The protostars embedded in some</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AN....337..512P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AN....337..512P"><span id="translatedtitle">High ionisation absorption in <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ponti, G.; Bianchi, S.; Muñoz-Darias, T.; De, K.; Fender, R.; Merloni, A.</p> <p>2016-05-01</p> <p>The advent of the new generation of X-ray telescopes yielded a significant step forward in our understanding of ionised absorption generated in the accretion discs of X-ray binaries. It has become evident that these relatively weak and narrow absorption features, sporadically present in the X-ray spectra of some <span class="hlt">systems</span>, are actually the signature of equatorial outflows, which might carry away more matter than that being accreted. Therefore, they play a major role in the accretion phenomenon. These outflows (or ionised atmospheres) are ubiquitous during the softer states but absent during the power-law dominated, hard states, suggesting a strong link with the state of the inner accretion disc, presence of the radio-jet and the properties of the central source. Here, we discuss the current understanding of this field.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5824488','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5824488"><span id="translatedtitle">344 cm x 86 cm <span class="hlt">low</span> <span class="hlt">mass</span> vacuum window</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reimers, R.M.; Porter, J.; Meneghetti, J.; Wilde, S.; Miller, R.</p> <p>1983-08-01</p> <p>The LBL Heavy Ion Spectrometer <span class="hlt">System</span> (HISS) superconducting magnet contains a 1 m x 3.45 m x 2 m vacuum tank in its gap. A full aperture thin window was needed to minimize background as the products of nuclear collisions move from upstream targets to downstream detectors. Six windows were built and tested in the development process. The final window's unsupported area is 3m/sup 2/ with a 25 cm inward deflection. The design consists of a .11 mm Nylon/aluminum/polypropylene laminate as a gas seal and .55 mm woven aramid fiber for strength. Total mass is 80 milligrams per cm/sup 2/. Development depended heavily on past experience and testing. Safety considerations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/964527','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/964527"><span id="translatedtitle">Evolution of Very Close Binaries of <span class="hlt">Low</span> <span class="hlt">Mass</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Eggleton, P</p> <p>2009-07-17</p> <p>Binaries of low total mass (say 1-3 M{sub {circle_dot}}) and very short period (say {approx}< 4 d) are subject to a number of evolutionary processes, such as nuclear evolution, Roche-Lobe overflow, mass loss by stellar wind enhanced by rapid rotation, angular momentum loss by stellar wind with magnetic braking and tidal friction, mass transfer in contact (potentially in either direction), and heat transport from one component to the other during contact. Unfortunately all of these phenomena can be expected to occur on something like the same timescale. This makes it especially difficult to tie a particular <span class="hlt">system</span> to a particular set of evolutionary processes. Theory suggests that very close binaries should appear in four morphological forms: detached binaries, semidetached binaries in which the more massive component is the one that fills its Roche lobe (reverse Algols), semidetached binaries in which the less massive component is the one that fills its Roche lobe (normal Algols), and contact, or, as some would say, overcontact binaries, where both components overfill their Roche lobes up to the same equipotential surface. This is not to say that perhaps some other configuration may be important, but I am not sure that any has yet been put forward that is incontrovertible. I have developed an evolutionary code in which the two components are solved simultaneously, and subject in principle to all six of the processes in the first paragraph. All four morphological forms are achievable by the code, as the physics demands. The code is still preliminary, partly at least because of the difficulty of quantifying all six processes. I will illustrate some possibly peculiar evolutionary scenarios that can emerge; but I will mainly argue, on the basis of observed data from a variety of <span class="hlt">systems</span>, that it is indeed necessary to include all these processes, and not, for example, to ignore mass loss by stellar wind by claiming that it cannot be strong enough to be significant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19870044856&hterms=naked&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnaked','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19870044856&hterms=naked&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnaked"><span id="translatedtitle">The naked T Tauri stars - The <span class="hlt">low-mass</span> pre-main sequence unveiled</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Walter, Frederick M.</p> <p>1987-01-01</p> <p>The search for <span class="hlt">low-mass</span> premain-sequence (PMS) stars associated with X-ray sources in regions of star formation is discussed. The survey to date has revealed at least 30 <span class="hlt">low-mass</span> PMS stars in the Tau-Aur region, and a comparable number in Oph. These stars are the naked T Tau stars, unveiled versions of the well-known classical T Tau stars. The properties of these newly discovered PMS stars and their relation to the classical T Tau stars are discussed, and it is concluded that the naked T Tau stars are the true <span class="hlt">low-mass</span> PMS stars, and that the observable characteristics defining the classical T Tau stars are due to the interaction of an underlying, fairly normal star with a dominant circumstellar environment. The impact the naked T Tau stars are likely to have on models of the PMS evolution of <span class="hlt">low-mass</span> stars is considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22340051','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22340051"><span id="translatedtitle">The formation of Pluto's <span class="hlt">low-mass</span> satellites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kenyon, Scott J.; Bromley, Benjamin C. E-mail: bromley@physics.utah.edu</p> <p>2014-01-01</p> <p>Motivated by the New Horizons mission, we consider how Pluto's small satellites—currently Styx, Nix, Kerberos, and Hydra—grow in debris from the giant impact that forms the Pluto-Charon binary. After the impact, Pluto and Charon accrete some of the debris and eject the rest from the binary orbit. During the ejection, high-velocity collisions among debris particles produce a collisional cascade, leading to the ejection of some debris from the <span class="hlt">system</span> and enabling the remaining debris particles to find stable orbits around the binary. Our numerical simulations of coagulation and migration show that collisional evolution within a ring or a disk of debris leads to a few small satellites orbiting Pluto-Charon. These simulations are the first to demonstrate migration-induced mergers within a particle disk. The final satellite masses correlate with the initial disk mass. More massive disks tend to produce fewer satellites. For the current properties of the satellites, our results strongly favor initial debris masses of 3-10 × 10{sup 19} g and current satellite albedos A ≈ 0.4-1. We also predict an ensemble of smaller satellites, R ≲ 1-3 km, and very small particles, R ≈ 1-100 cm and optical depth τ ≲ 10{sup –10}. These objects should have semimajor axes outside the current orbit of Hydra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014bsee.confP..25S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014bsee.confP..25S"><span id="translatedtitle">Hot subdwarfs in (eclipsing) binaries with brown dwarf or <span class="hlt">low-mass</span> main-sequence companions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schaffenroth, Veronika; Geier, Stephan; Heber, Uli</p> <p>2014-09-01</p> <p>The formation of hot subdwarf stars (sdBs), which are core helium-burning stars located on the extended horizontal branch, is not yet understood. Many of the known hot subdwarf stars reside in close binary <span class="hlt">systems</span> with short orbital periods of between a few hours and a few days, with either M-star or white-dwarf companions. Common-envelope ejection is the most probable formation channel. Among these, eclipsing <span class="hlt">systems</span> are of special importance because it is possible to constrain the parameters of both components tightly by combining spectroscopic and light-curve analyses. They are called HW Virginis <span class="hlt">systems</span>. Soker (1998) proposed that planetary or brown-dwarf companions could cause the mass loss necessary to form an sdB. Substellar objects with masses greater than >10 M_J were predicted to survive the common-envelope phase and end up in a close orbit around the stellar remnant, while planets with lower masses would entirely evaporate. This raises the question if planets can affect stellar evolution. Here we report on newly discovered eclipsing or not eclipsing hot subdwarf binaries with brown-dwarf or <span class="hlt">low-mass</span> main-sequence companions and their spectral and photometric analysis to determine the fundamental parameters of both components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005A%26A...430..987S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005A%26A...430..987S"><span id="translatedtitle">Photometric and spectroscopic study of <span class="hlt">low</span> <span class="hlt">mass</span> embedded star clusters in reflection nebulae</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soares, J. B.; Bica, E.; Ahumada, A. V.; Clariá, J. J.</p> <p>2005-02-01</p> <p>An analysis of the candidate embedded stellar <span class="hlt">systems</span> in the reflection nebulae vdBH-RN 26, vdBH-RN} 38, vdBH-RN} 53a, GGD 20, ESO 95-RN 18 and NGC 6595 is presented. Optical spectroscopic data from CASLEO (Argentina) in conjunction with near infrared photometry from the 2MASS Point Source Catalogue were employed. The analysis is based on source surface density, colour-colour and colour-magnitude diagrams together with theoretical pre-main sequence isochrones. We take into account the field population affecting the analysis by carrying out a statistical subtraction. The fundamental parameters for the stellar <span class="hlt">systems</span> were derived. The resulting ages are in the range 1-4 Myr and the objects are dominated by pre-main sequence stars. The observed masses locked in the clusters are less than 25 M⊙. The studied <span class="hlt">systems</span> have no stars of spectral types earlier than B, indicating that star clusters do not necessarily evolve through an HII region phase. The relatively small locked mass combined with the fact that they are not numerous in catalogues suggests that these <span class="hlt">low</span> <span class="hlt">mass</span> clusters are not important donors of stars to the field populations. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008A%26A...478..419S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008A%26A...478..419S"><span id="translatedtitle">Near infrared photometric and optical spectroscopic study of 22 <span class="hlt">low</span> <span class="hlt">mass</span> star clusters embedded in nebulae</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soares, J. B.; Bica, E.; Ahumada, A. V.; Clariá, J. J.</p> <p>2008-02-01</p> <p>Aims:Among the star clusters in the Galaxy, those embedded in nebulae represent the youngest group, which has only recently been explored. The analysis of a sample of 22 candidate embedded stellar <span class="hlt">systems</span> in reflection nebulae and/or HII environments is presented. Methods: We employed optical spectroscopic observations of stars in the directions of the clusters carried out at CASLEO (Argentina) together with near infrared photometry from the 2MASS catalogue. Our analysis is based on source surface density, colour-colour diagrams and on theoretical pre-main sequence isochrones. We take into account the field star contamination by carrying out a statistical subtraction. Results: The studied objects have the characteristics of <span class="hlt">low</span> <span class="hlt">mass</span> <span class="hlt">systems</span>. We derive their fundamental parameters. Most of the cluster ages are younger than 2 Myr. The studied embedded stellar <span class="hlt">systems</span> in reflection nebulae and/or HII region complexes do not have stars of spectral types earlier than B. The total stellar masses locked in the clusters are in the range 20-220 M⊙. They are found to be gravitationally unstable and are expected to dissolve in a timescale of a few Myr. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/935437','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/935437"><span id="translatedtitle">SIEMENS ADVANCED QUANTRA FTICR MASS SPECTROMETER FOR ULTRA HIGH RESOLUTION AT <span class="hlt">LOW</span> <span class="hlt">MASS</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Spencer, W; Laura Tovo, L</p> <p>2008-07-08</p> <p>The Siemens Advanced Quantra Fourier Transform Ion Cyclotron Resonance (FTICR) mass spectrometer was evaluated as an alternative instrument to large double focusing mass spectrometers for gas analysis. High resolution mass spectrometers capable of resolving the common mass isomers of the hydrogen isotopes are used to provide data for accurate loading of reservoirs and to monitor separation of tritium, deuterium, and helium. Conventional double focusing magnetic sector instruments have a resolution that is limited to about 5000. The Siemens FTICR instrument achieves resolution beyond 400,000 and could possibly resolve the tritium ion from the helium-3 ion, which differ by the weight of an electron, 0.00549 amu. Working with Y-12 and LANL, SRNL requested Siemens to modify their commercial Quantra <span class="hlt">system</span> for <span class="hlt">low</span> <span class="hlt">mass</span> analysis. To achieve the required performance, Siemens had to increase the available waveform operating frequency from 5 MHz to 40 MHz and completely redesign the control electronics and software. However, they were able to use the previous ion trap, magnet, passive pump, and piezo-electric pulsed inlet valve design. NNSA invested $1M in this project and acquired four <span class="hlt">systems</span>, two for Y-12 and one each for SRNL and LANL. Siemens claimed a $10M investment in the Quantra <span class="hlt">systems</span>. The new Siemens Advanced Quantra demonstrated phenomenal resolution in the <span class="hlt">low</span> <span class="hlt">mass</span> range. Resolution greater than 400,000 was achieved for mass 2. The new spectrometer had a useful working mass range to 500 Daltons. However, experiments found that a continuous single scan from <span class="hlt">low</span> <span class="hlt">mass</span> to high was not possible. Two useful working ranges were established covering masses 1 to 6 and masses 12 to 500 for our studies. A compromise performance condition enabled masses 1 to 45 to be surveyed. The instrument was found to have a dynamic range of about three orders of magnitude and quantitative analysis is expected to be limited to around 5 percent without using complex fitting algorithms</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21583051','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21583051"><span id="translatedtitle">INFRARED AND OPTICAL POLARIMETRY AROUND THE <span class="hlt">LOW-MASS</span> STAR-FORMING REGION NGC 1333 IRAS 4A</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Alves, Felipe O.; Girart, Josep M.; Acosta-Pulido, Jose A.; Franco, Gabriel A. P.; Lopez, Rosario E-mail: girart@ice.cat E-mail: franco@fisica.ufmg.br E-mail: falves@astro.uni-bonn.de</p> <p>2011-07-15</p> <p>We performed J- and R-band linear polarimetry with the 4.2 m William Herschel Telescope at the Observatorio del Roque de los Muchachos and with the 1.6 m telescope at the Observatorio do Pico dos Dias, respectively, to derive the magnetic field geometry of the diffuse molecular cloud surrounding the embedded <span class="hlt">protostellar</span> <span class="hlt">system</span> NGC 1333 IRAS 4A. We obtained interstellar polarization data for about three dozen stars. The distribution of polarization position angles has low dispersion and suggests the existence of an ordered magnetic field component at physical scales larger than the protostar. Some of the observed stars present intrinsic polarization and evidence of being young stellar objects. The estimated mean orientation of the interstellar magnetic field as derived from these data is almost perpendicular to the main direction of the magnetic field associated with the dense molecular envelope around IRAS 4A. Since the distribution of the CO emission in NGC 1333 indicates that the diffuse molecular gas has a multi-layered structure, we suggest that the observed polarization position angles are caused by the superposed projection of different magnetic field components along the line of sight.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ARep...57..120K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ARep...57..120K"><span id="translatedtitle">Class I methanol masers in <span class="hlt">low-mass</span> star-forming regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kalenskii, S. V.; Kurtz, S.; Bergman, P.</p> <p>2013-02-01</p> <p>Results of observations of Class I methanol masers in regions of <span class="hlt">low-mass</span> star formation (MMIL) are summarized and analyzed. Four masers were detected at 44, 84, and 95 GHz towards "chemically active" bipolar outflows in the <span class="hlt">low-mass</span> star-forming regions NGC1333 I4A, NGC 1333 I2A, HH 25, and L1157. Another maser was found at 36 GHz towards a similar outflow in NGC 2023. Thus, all the detected MMILs are associated with chemically active outflows. The brightness temperatures of the strongest 44-GHz maser spots in NGC 1333 I4A, HH 25, and L1157 exceed 2000 K, whereas the brightness temperature in NGC 1333 I2A is only 176 K, although a rotational-diagram analysis shows that this last source is also amaser. The flux densities of the newly detectedmasers are no higher than 18 Jy, and are much lower than those of strong masers in regions of high-mass star formation (MMIH). The MMIL luminosities match the maser luminosity-protostar luminosity relation established earlier for MMIHs. No MMIL variability was detected in 2004-2011. The radial velocities of the newly detected masers are close to the <span class="hlt">systemic</span> velocities of the associated regions, except for NGC 2023, where the maser radial velocity is lower than the <span class="hlt">systemic</span> velocity by approximately 3.5 km/s. Thus, the main MMILproperties are similar to those of MMIHs. MMILs are likely to be an extension of the MMIH population toward lower luminosities of both the masers and the associated young stellar objects. The results of VLA observations of MMILs can be explained using a turbulent-cloud model, which predicts that compact maser spots can arise in extended sources because the coherence lengths along some directions randomly appear to be longer than the mean coherence length in a turbulent velocity field. However, one must assume that the column density of methanol towardM1, the strongest maser in L1157, is appreciably higher than the mean column density of the clump B0a where the maser arises. The shape of the maser lines</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22356540','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22356540"><span id="translatedtitle">WISE detection of the galactic <span class="hlt">low-mass</span> X-ray binaries</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, Xuebing; Wang, Zhongxiang</p> <p>2014-06-20</p> <p>We report on the results from our search for the Wide-field Infrared Survey Explorer (WISE) detection of the Galactic <span class="hlt">low-mass</span> X-ray binaries (LMXBs). Among 187 binaries cataloged in Liu et al., we find 13 counterparts and 2 candidate counterparts. For the 13 counterparts, 2 (4U 0614+091 and GX 339–4) have already been confirmed by previous studies to have a jet and 1 (GRS 1915+105) to have a candidate circumbinary disk, from which the detected infrared emission arose. Having collected the broadband optical and near-infrared data in the literature and constructed flux density spectra for the other 10 binaries, we identify that 3 (A0620–00, XTE J1118+480, and GX 1+4) are candidate circumbinary disk <span class="hlt">systems</span>, 4 (Cen X-4, 4U 1700+24, 3A 1954+319, and Cyg X-2) had thermal emission from their companion stars, and 3 (Sco X-1, Her X-1, and Swift J1753.5–0127) are peculiar <span class="hlt">systems</span> with the origin of their infrared emission rather uncertain. We discuss the results and WISE counterparts' brightness distribution among the known LMXBs, and suggest that more than half of the LMXBs would have a jet, a circumbinary disk, or both.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.460.3992N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.460.3992N"><span id="translatedtitle">Common envelope events with <span class="hlt">low-mass</span> giants: understanding the energy budget</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nandez, J. L. A.; Ivanova, N.</p> <p>2016-08-01</p> <p>Common envelope events are important interactions between two binary stars that lead to the formation of close binary <span class="hlt">systems</span>. We present here a systematic three-dimensional study in which we model common envelope events with <span class="hlt">low-mass</span> giant donors. The results allow us to revise the energy formalism that is usually used to determine common envelope event outcomes. We show that the energy budget for this type of <span class="hlt">system</span> should include the recombination energy, and that it also must take into account that a significant fraction of the released orbital energy is taken away by the ejecta. We provide three ways in which our results can be used by binary population synthesis studies: a relation that links the observed post-common envelope binary with the initial binary parameters, a fitting formula for the αceλ parameter of the standard energy formalism, and a revised energy formalism that takes into account both the recombination energy and the energy that is taken away by the ejecta.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997AAS...191.4411W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997AAS...191.4411W&link_type=ABSTRACT"><span id="translatedtitle">A Dynamical Study of the <span class="hlt">Low</span> <span class="hlt">Mass</span> X-ray Binary GX 349+2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wachter, S.</p> <p>1997-12-01</p> <p>We have obtained simultaneous optical photometry and spectroscopy of the <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binary (and Z-source) GX 349+2 with the CTIO 0.9 m and 4 m telescopes in July 1997. The spectrum of GX 349+2 only shows strong, narrow Hα emission. The observed radial velocities indicate that our previously reported 22 hour photometric modulation is indeed the orbital period. We find gamma =-250+/-10 km s(-1) and K=65+/-6 km s(-1) for the <span class="hlt">systemic</span> and semi-amplitude velocities respectively. The photometric light curve and radial velocity curve are offset by 0.25 in phase. Doppler tomography shows the Hα emission centered on the position of the neutron star. The relative phasing implies that the photometric variability is probably caused by the heated face of the companion star while the Hα emission may arise in an accretion disk and traces the motion of the neutron star. It also indicates that the emission region is symmetric around the neutron star. If the Hα emission does originate in the accretion disk, the narrowness of the line suggests a low inclination for the <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040089223&hterms=onion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Donion','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040089223&hterms=onion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Donion"><span id="translatedtitle">Evolutionary status of the pre-<span class="hlt">protostellar</span> core L1498</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuiper, T. B.; Langer, W. D.; Velusamy, T.; Levin, S. M. (Principal Investigator)</p> <p>1996-01-01</p> <p>L1498 is a classic example of a dense cold pre-<span class="hlt">protostellar</span> core. To study the evolutionary status, the structure, dynamics, and chemical properties of this core we have obtained high spatial and high spectral resolution observations of molecules tracing densities of 10(3)-10(5) cm-3. We observed CCS, NH3, C3H2, and HC7N with NASA's DSN 70 m antennas. We also present large-scale maps of C18O and 13CO observed with the AT&T 7 m antenna. For the high spatial resolution maps of selected regions within the core we used the VLA for CCS at 22 GHz, and the Owens Valley Radio Observatory (OVRO) MMA for CCS at 94 GHz and CS (2-1). The 22 GHz CCS emission marks a high-density [n(H2) > 10(4) cm -3] core, which is elongated with a major axis along the SE-NW direction. NH3 and C3H2 emissions are located inside the boundary of the CCS emission. C18O emission traces a lower density gas extending beyond the CCS boundary. Along the major axis of the dense core, CCS, NH3 and C3H2 emission show evidence of limb brightening. The observations are consistent with a chemically differentiated onion-shell structure for the L1498 core, with NH3 in the inner and CCS in the outer parts of the core. The high angular resolution (9"-12") spectral line maps obtained by combining NASA Goldstone 70 m and VLA data resolve the CCS 22 GHz emission in the southeast and northwest boundaries into arclike enhancements, supporting the picture that CCS emission originates in a shell outside the NH3 emitting region. Interferometric maps of CCS at 94 GHz and CS at 98 GHz show that their emitting regions contain several small-scale dense condensations. We suggest that the differences between the CCS, CS, C3H2, and NH3 emission are caused by a time-dependent effect as the core evolves slowly. We interpret the chemical and physical properties of L1498 in terms of a quasi-static (or slowly contracting) dense core in which the outer envelope is still growing. The growth rate of the core is determined by the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21392493','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21392493"><span id="translatedtitle">DUST TRANSPORT IN <span class="hlt">PROTOSTELLAR</span> DISKS THROUGH TURBULENCE AND SETTLING</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Turner, N. J.; Carballido, A.; Sano, T.</p> <p>2010-01-01</p> <p>We apply ionization balance and magnetohydrodynamical (MHD) calculations to investigate whether magnetic activity moderated by recombination on dust grains can account for the mass accretion rates and the mid-infrared spectra and variability of <span class="hlt">protostellar</span> disks. The MHD calculations use the stratified shearing-box approach and include grain settling and the feedback from the changing dust abundance on the resistivity of the gas. The two-decade spread in accretion rates among solar-mass T Tauri stars is too large to result solely from variations in the grain size and stellar X-ray luminosity, but can plausibly be produced by varying these parameters together with the disk magnetic flux. The diverse shapes and strengths of the mid-infrared silicate bands can come from the coupling of grain settling to the distribution of the magnetorotational turbulence, through the following three effects. First, recombination on grains 1 mum or smaller yields a magnetically inactive dead zone extending more than two scale heights from the midplane, while turbulent motions in the magnetically active disk atmosphere overshoot the dead zone boundary by only about one scale height. Second, grains deep in the dead zone oscillate vertically in wave motions driven by the turbulent layer above, but on average settle at the rates found in laminar flow, so that the interior of the dead zone is a particle sink and the disk atmosphere will become dust-depleted unless resupplied from elsewhere. Third, with sufficient depletion, the dead zone is thinner and mixing dredges grains off the midplane. The last of these processes enables evolutionary signatures such as the degree of settling to sometimes decrease with age. The MHD results also show that the magnetic activity intermittently lifts clouds of small grains into the atmosphere. Consequently the photosphere height changes by up to one-third over timescales of a few orbits, while the extinction along lines of sight grazing the disk surface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010025059','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010025059"><span id="translatedtitle">Identification of Gas Phase PAHs in Absorption Towards <span class="hlt">Protostellar</span> Sources</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bregman, Jesse D.; Temi, Pasquale; DeVincenzi, Donald L. (Technical Monitor)</p> <p>2000-01-01</p> <p>The infrared emission bands (also known as the UIR bands.) have recently been observed in absorption at 3.25 micrometers in the ices surrounding a few <span class="hlt">proto-stellar</span> objects at 11.2 micrometers in MonR2, and at 6.2 micrometers towards two sources near the galactic center. The UIR bands have been observed in emission for many years, but identifying these bands has proven to be both difficult and contentious as no one has yet found a single material that provides a good match to the features. However, most investigators agree that some form of carbon-based material with aromatic bonds is the most likely candidate, and many arguments favor free molecules (polycyclic aromatic hydrocarbons, PAHs) as the carriers of at least the narrow emission bands. Since the emission arises not from a single molecule but from a family of molecules, identifying which PAHs are contributing to the infrared emission bands is difficult. The identification is further complicated by the fact that the emission at short wavelengths is dominated by small molecules while at long wavelengths it is dominated by large molecules. Thus, for example, the emission at 3.3 micrometers is from a different mix of molecules than those which produce the 11.2 micrometer band. To complicate matters further, the molecular mix includes both neutral and ionic species. In absorption, the same mixture of molecules contributes at all wavelengths and the molecules should be neutral, potentially simplifying comparisons with lab data. Also, absorption strengths measured in the lab are directly applicable to interstellar absorption bands without the need to model an emission spectrum of an unknown mixture of ionized and neutral PAHs. In this paper we show that a mixture of argon matrix isolated PAH molecules can reproduce the 3.25 micrometers absorption band seen in the ISO SWS spectra of four embedded Infrared sources, S140 IRS1, AFGL 2591, Elias 29, and AFGL 989. In section 2 we describe the ISO SWS data analysis and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.438.2538P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.438.2538P"><span id="translatedtitle">How the presence of a gas giant affects the formation of mean-motion resonances between two <span class="hlt">low-mass</span> planets in a locally isothermal gaseous disc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Podlewska-Gaca, E.; Szuszkiewicz, E.</p> <p>2014-03-01</p> <p>In this paper we investigate the possibility of a migration-induced resonance locking in <span class="hlt">systems</span> containing three planets, namely an Earth analogue (1 M⊕), a super-Earth (4 M⊕) and a gas giant (one Jupiter mass). The planets have been listed in order of increasing orbital periods. All three bodies are embedded in a locally isothermal gaseous disc and orbit around a solar mass star. We are interested in answering the following questions: will the <span class="hlt">low-mass</span> planets form the same resonant structures with each other in the vicinity of the gas giant as in the case when the gas giant is absent? More in general, how will the presence of the gas giant affect the evolution of the two <span class="hlt">low-mass</span> planets? When there is no gas giant in the <span class="hlt">system</span>, it has been already shown that if the two <span class="hlt">low-mass</span> planets undergo a convergent differential migration, they will capture each other in a mean-motion resonance. For the choices of disc parameters and planet masses made in this paper, the formation of the 5:4 resonance in the absence of the Jupiter has been observed in a previous investigation and confirmed here. In this work we add a gas giant on the most external orbit of the <span class="hlt">system</span> in such a way that its differential migration is convergent with the <span class="hlt">low-mass</span> planets. We show that the result of this set-up is the speeding up of the migration of the super-Earth and, after that, all three planets become locked in a triple mean-motion resonance. However, this resonance is not maintained due to the <span class="hlt">low-mass</span> planet eccentricity excitation, a fact that leads to close encounters between planets and eventually to the ejection from the internal orbits of one or both <span class="hlt">low-mass</span> planets. We have observed that the ejected <span class="hlt">low-mass</span> planets can leave the <span class="hlt">system</span>, fall into a star or become the external planet relative to the gas giant. In our simulations the latter situation has been observed for the super-Earth. It follows from the results presented here that the presence of a Jupiter-like planet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22730506S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22730506S"><span id="translatedtitle">Direct Exoplanet Imaging with JWST NIRCam: <span class="hlt">Low-Mass</span> Stars, <span class="hlt">Low-Mass</span> Planets, and Critical Constraints on Planet Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlieder, Joshua E.; Meyer, Michael; Reggiani, Maddalena; Quanz, Sascha; Beichman, Charles A.; Greene, Thomas P.; Burrows, Adam Seth</p> <p>2016-01-01</p> <p>As next generation exoplanet imagers are making their first discoveries, the largest population of stars in the Galaxy, the M dwarfs, are largely unaccounted for in their surveys. However, RV trends and micro lensing have revealed that M dwarfs host a substantial population of Neptune to Jupiter mass planets between ~1-10 AU. The unprecedented sensitivity of NIRCam on the JWST provides direct access to this population of gas-giants. A NIRCam 3 - 5 μm survey for such planets will place critical constraints on planet formation by: 1) measuring the luminosities of young, sub-Jupiter mass planets, 2) providing constraints on the peak in the companion surface density vs. separation distribution, and 3) measuring the frequency of ≤Jupiter mass giants in the outskirts of these <span class="hlt">systems</span> (>10 AU). We have carefully constructed a sample of nearby, young, late-type stars, performed NIRCam survey simulations, and will report on the expected yield and advantages of JWST compared to current ground based capabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...806...62B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...806...62B"><span id="translatedtitle">Planets Around <span class="hlt">Low-mass</span> Stars (PALMS). V. Age-dating <span class="hlt">Low-mass</span> Companions to Members and Interlopers of Young Moving Groups</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bowler, Brendan P.; Shkolnik, Evgenya L.; Liu, Michael C.; Schlieder, Joshua E.; Mann, Andrew W.; Dupuy, Trent J.; Hinkley, Sasha; Crepp, Justin R.; Johnson, John Asher; Howard, Andrew W.; Flagg, Laura; Weinberger, Alycia J.; Aller, Kimberly M.; Allers, Katelyn N.; Best, William M. J.; Kotson, Michael C.; Montet, Benjamin T.; Herczeg, Gregory J.; Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Nielsen, Eric L.; Wahhaj, Zahed; Biller, Beth A.; Hayward, Thomas L.</p> <p>2015-06-01</p> <p>We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7-M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8-120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (˜10-100 MJup) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each <span class="hlt">system</span> to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892-0929121 C (40-60 MJup) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the ˜40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young <span class="hlt">low-mass</span> quadruple <span class="hlt">system</span> in a compact (≲100 AU) configuration. In addition, Li i λ6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (≲200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1″) companions (2MASS J06475229-2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (≳1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the dustiest-known member of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22522311','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22522311"><span id="translatedtitle">PLANETS AROUND <span class="hlt">LOW-MASS</span> STARS (PALMS). V. AGE-DATING <span class="hlt">LOW-MASS</span> COMPANIONS TO MEMBERS AND INTERLOPERS OF YOUNG MOVING GROUPS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bowler, Brendan P.; Montet, Benjamin T.; Riddle, Reed; Shkolnik, Evgenya L.; Flagg, Laura; Liu, Michael C.; Howard, Andrew W.; Aller, Kimberly M.; Best, William M. J.; Kotson, Michael C.; Baranec, Christoph; Schlieder, Joshua E.; Mann, Andrew W.; Dupuy, Trent J.; Hinkley, Sasha; Crepp, Justin R.; Johnson, John Asher; Weinberger, Alycia J.; Allers, Katelyn N.; Herczeg, Gregory J.; and others</p> <p>2015-06-10</p> <p>We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7–M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8–120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (∼10–100 M{sub Jup}) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each <span class="hlt">system</span> to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892–0929121 C (40–60 M{sub Jup}) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the ∼40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young <span class="hlt">low-mass</span> quadruple <span class="hlt">system</span> in a compact (≲100 AU) configuration. In addition, Li i λ6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (≲200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1″) companions (2MASS J06475229–2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (≳1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ASPC..418...73S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ASPC..418...73S"><span id="translatedtitle">Class 0 <span class="hlt">Protostellar</span> Candidates in the AKARI-FIS Bright Source Catalogue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sunada, K.; Ikeda, N.; Kitamura, Y.; Nakazato, T.; Yang, J.</p> <p>2009-12-01</p> <p>It is expected that the FIS Bright Source Catalogue contains many Class 0 <span class="hlt">protostellar</span> candidates. In particular, the identification of high-mass <span class="hlt">protostellar</span> candidates is expected. To search new <span class="hlt">protostellar</span> candidates systematically in the FIS Bright Source Catalogue, we characterized the far-infrared properties of various known objects. We carried out the identification of the FIS point sources for our 1563 survey sources. As a result, we could find the region occupied by the sources associated with the water maser emission on the FIS log(F140 μm) - log(F90 μm/F65 μm) diagram. Comparing the core properties with the far-infrared properties, we also found the spread of the region occupied by the H2O maser sources meant the mass difference and the evolution sequence. Finally, we examined the far-infrared properties of all the point sources in the catalogue. Considering the above results, we were able to confirm the new <span class="hlt">protostellar</span> candidates from low- to high-mass in the FIS Bright Source Catalogue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013A%26A...549A..16N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013A%26A...549A..16N"><span id="translatedtitle">Mapping water in <span class="hlt">protostellar</span> outflows with Herschel. PACS and HIFI observations of L1448-C</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nisini, B.; Santangelo, G.; Antoniucci, S.; Benedettini, M.; Codella, C.; Giannini, T.; Lorenzani, A.; Liseau, R.; Tafalla, M.; Bjerkeli, P.; Cabrit, S.; Caselli, P.; Kristensen, L.; Neufeld, D.; Melnick, G.; van Dishoeck, E. F.</p> <p>2013-01-01</p> <p>Context. Water is a key probe of shocks and outflows from young stars because it is extremely sensitive to both the physical conditions associated with the interaction of supersonic outflows with the ambient medium and the chemical processes at play. Aims: Our goal is to investigate the spatial and velocity distribution of H2O along outflows, its relationship with other tracers, and its abundance variations. In particular, this study focuses on the outflow driven by the <span class="hlt">low-mass</span> protostar L1448-C, which previous observations have shown to be one of the brightest H2O emitters among the class 0 outflows. Methods: To this end, maps of the o-H2O 110-101 and 212-101 transitions taken with the Herschel-HIFI and PACS instruments, respectively, are presented. For comparison, complementary maps of the CO(3-2) and SiO(8-7) transitions, obtained at the JCMT, and the H2 S(0) and S(1) transitions, taken from the literature, were used as well. Physical conditions and H2O column densities were inferred using large velocity gradient radiative transfer calculations. Results: The water distribution appears to be clumpy, with individual peaks corresponding to shock spots along the outflow. The bulk of the 557 GHz line is confined to radial velocities in the range ±10-50 km s-1, but extended emission at extreme velocities (up to vr ~ 80 km s-1) is detected and is associated with the L1448-C extreme high-velocity (EHV) jet. The H2O 110-101/CO(3-2) ratio shows strong variations as a function of velocity that likely reflect different and changing physical conditions in the gas that is responsible for the emissions from the two species. In the EHV jet, a low H2O/SiO abundance ratio is inferred, which could indicate molecular formation from dust-free gas directly ejected from the <span class="hlt">proto-stellar</span> wind. The ratio between the two observed H2O lines and the comparison with H2 indicate averaged Tkin and n(H2) values of ~300-500 K and 5 × 106 cm-3, respectively, while a water abundance with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009A%26A...505.1115L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009A%26A...505.1115L"><span id="translatedtitle">A census of very-<span class="hlt">low-mass</span> stars and brown dwarfs in the σ Orionis cluster</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lodieu, N.; Zapatero Osorio, M. R.; Rebolo, R.; Martín, E. L.; Hambly, N. C.</p> <p>2009-10-01</p> <p>Context: The knowledge of the initial mass function (IMF) in open clusters constitutes one way of constraining the formation of <span class="hlt">low-mass</span> stars and brown dwarfs, along with the frequency of multiple <span class="hlt">systems</span> and the properties of disks. Aims: The aim of the project is to determine the shape of the mass function in the <span class="hlt">low-mass</span> and substellar regimes in the σ Orionis cluster (~3 Myr, ~352 pc, solar metallicity) as accurately as possible and compare it with the results in other clusters. Methods: We have analysed the near-infrared photometric data from the fourth data release (DR4) of the UKIRT Infrared Deep Sky Suvey (UKIDSS) Galactic clusters survey (GCS) to derive the cluster luminosity and mass functions, evaluate the extent of the cluster, and study the distribution and variability of <span class="hlt">low-mass</span> stars and brown dwarfs down to the deuterium-burning limit. Results: We have recovered most of the previously published members and found a total of 287 candidate members within the central 30 arcmin in the 0.5-0.009 M⊙ mass range, including new objects not previously reported in the literature. This new catalogue represents a homogeneous dataset of brown dwarf member candidates over the central 30 arcmin of the cluster. The expected photometric contamination by field objects with similar magnitudes and colours to σ Orionis members is ~15%. We present evidence of variability at the 99.5% confidence level over ~yearly timescales in 10 member candidates that exhibit signs of youth and the presence of disks. The level of variability is low (≤0.3 mag) and does not impact the derivation of the cluster luminosity and mass functions. Furthermore, we find a possible dearth of brown dwarfs within the central five arcmin of the cluster, which is not caused by a lower level of photometric sensitivity around the massive, O-type multiple star σ Ori in the GCS survey. Using state-of-the-art theoretical models, we derived the luminosity and mass functions within the central 30</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvD..93d4019F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvD..93d4019F"><span id="translatedtitle"><span class="hlt">Low</span> <span class="hlt">mass</span> binary neutron star mergers: Gravitational waves and neutrino emission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Foucart, Francois; Haas, Roland; Duez, Matthew D.; O'Connor, Evan; Ott, Christian D.; Roberts, Luke; Kidder, Lawrence E.; Lippuner, Jonas; Pfeiffer, Harald P.; Scheel, Mark A.</p> <p>2016-02-01</p> <p>Neutron star mergers are among the most promising sources of gravitational waves for advanced ground-based detectors. These mergers are also expected to power bright electromagnetic signals, in the form of short gamma-ray bursts, infrared/optical transients powered by r-process nucleosynthesis in neutron-rich material ejected by the merger, and radio emission from the interaction of that ejecta with the interstellar medium. Simulations of these mergers with fully general relativistic codes are critical to understand the merger and postmerger gravitational wave signals and their neutrinos and electromagnetic counterparts. In this paper, we employ the Spectral Einstein Code to simulate the merger of <span class="hlt">low</span> <span class="hlt">mass</span> neutron star binaries (two 1.2 M⊙ neutron stars) for a set of three nuclear-theory-based, finite temperature equations of state. We show that the frequency peaks of the postmerger gravitational wave signal are in good agreement with predictions obtained from recent simulations using a simpler treatment of gravity. We find, however, that only the fundamental mode of the remnant is excited for long periods of time: emission at the secondary peaks is damped on a millisecond time scale in the simulated binaries. For such <span class="hlt">low</span> <span class="hlt">mass</span> <span class="hlt">systems</span>, the remnant is a massive neutron star which, depending on the equation of state, is either permanently stable or long lived (i.e. rapid uniform rotation is sufficient to prevent its collapse). We observe strong excitations of l =2 , m =2 modes, both in the massive neutron star and in the form of hot, shocked tidal arms in the surrounding accretion torus. We estimate the neutrino emission of the remnant using a neutrino leakage scheme and, in one case, compare these results with a gray two-moment neutrino transport scheme. We confirm the complex geometry of the neutrino emission, also observed in previous simulations with neutrino leakage, and show explicitly the presence of important differences in the neutrino luminosity, disk</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...829L..26L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...829L..26L"><span id="translatedtitle">The Influence of Environment on the Chemical Evolution in <span class="hlt">Low-mass</span> Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Yiqing; Ho, Luis C.; Peng, Eric</p> <p>2016-10-01</p> <p>The mean alpha-to-iron abundance ratio ([α/Fe]) of galaxies is sensitive to the chemical evolution processes at early time, and it is an indicator of star formation timescale ({τ }{SF}). Although the physical reason remains ambiguous, there is a tight relation between [α/Fe] and stellar velocity dispersion (σ) among massive early-type galaxies (ETGs). However, no work has shown convincing results as to how this relation behaves at <span class="hlt">low</span> <span class="hlt">masses</span>. We assemble 15 data sets from the literature and build a large sample that includes 192 nearby <span class="hlt">low-mass</span> (18\\lt σ \\lt 80 km s-1) ETGs. We find that the [α/Fe]-σ relation generally holds for <span class="hlt">low-mass</span> ETGs, except in extreme environments. Specifically, in normal galaxy cluster environments, the [α/Fe]-σ relation and its intrinsic scatter are, within uncertainties, similar for <span class="hlt">low-mass</span> and high-mass ETGs. However, in the most massive relaxed galaxy cluster in our sample, the zero point of the relation is higher and the intrinsic scatter is significantly larger. By contrast, in galaxy groups the zero point of the relation offsets in the opposite direction, again with substantial intrinsic scatter. The elevated [α/Fe] of <span class="hlt">low-mass</span> ETGs in the densest environments suggests that their star formation was quenched earlier. For the <span class="hlt">low-mass</span> ETGs in the lowest-density environments, we suggest that their more extended star formation histories suppressed their average [α/Fe]. The large scatter in [α/Fe] may reflect stochasticity in the chemical evolution of <span class="hlt">low-mass</span> galaxies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21471274','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21471274"><span id="translatedtitle">THE ELM SURVEY. I. A COMPLETE SAMPLE OF EXTREMELY <span class="hlt">LOW-MASS</span> WHITE DWARFS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brown, Warren R.; Kilic, Mukremin; Kenyon, Scott J.; Prieto, Carlos Allende E-mail: mkilic@cfa.harvard.ed E-mail: callende@iac.e</p> <p>2010-11-10</p> <p>We analyze radial velocity observations of the 12 extremely <span class="hlt">low-mass</span> (ELM), with {<=}0.25 M{sub sun}, white dwarfs (WDs) in the MMT Hypervelocity Star Survey. Eleven of the twelve WDs are binaries with orbital periods shorter than 14 hr; the one non-variable WD is possibly a pole-on <span class="hlt">system</span> among our non-kinematically selected targets. Our sample is unique: it is complete in a well-defined range of apparent magnitude and color. The orbital mass functions imply that the unseen companions are most likely other WDs, although neutron star companions cannot be excluded. Six of the eleven <span class="hlt">systems</span> with orbital solutions will merge within a Hubble time due to the loss of angular momentum through gravitational wave radiation. The quickest merger is J0923+3028, a g = 15.7 ELM WD binary with a 1.08 hr orbital period and a {<=}130 Myr merger time. The chance of a supernova Ia event among our ELM WDs is only 1%-7%, however. Three binary <span class="hlt">systems</span> (J0755+4906, J1233+1602, and J2119-0018) have extreme mass ratios and will most likely form stable mass-transfer AM CVn <span class="hlt">systems</span>. Two of these objects, SDSS J1233+1602 and J2119-0018, are the lowest surface gravity WDs ever found; both show Ca II absorption likely from accretion of circumbinary material. We predict that at least one of our WDs is an eclipsing detached double WD <span class="hlt">system</span>, important for constraining helium core WD models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ApJ...723.1072B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ApJ...723.1072B"><span id="translatedtitle">The ELM Survey. I. A Complete Sample of Extremely <span class="hlt">Low-mass</span> White Dwarfs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Warren R.; Kilic, Mukremin; Allende Prieto, Carlos; Kenyon, Scott J.</p> <p>2010-11-01</p> <p>We analyze radial velocity observations of the 12 extremely <span class="hlt">low-mass</span> (ELM), with <=0.25 M sun, white dwarfs (WDs) in the MMT Hypervelocity Star Survey. Eleven of the twelve WDs are binaries with orbital periods shorter than 14 hr; the one non-variable WD is possibly a pole-on <span class="hlt">system</span> among our non-kinematically selected targets. Our sample is unique: it is complete in a well-defined range of apparent magnitude and color. The orbital mass functions imply that the unseen companions are most likely other WDs, although neutron star companions cannot be excluded. Six of the eleven <span class="hlt">systems</span> with orbital solutions will merge within a Hubble time due to the loss of angular momentum through gravitational wave radiation. The quickest merger is J0923+3028, a g = 15.7 ELM WD binary with a 1.08 hr orbital period and a <=130 Myr merger time. The chance of a supernova Ia event among our ELM WDs is only 1%-7%, however. Three binary <span class="hlt">systems</span> (J0755+4906, J1233+1602, and J2119-0018) have extreme mass ratios and will most likely form stable mass-transfer AM CVn <span class="hlt">systems</span>. Two of these objects, SDSS J1233+1602 and J2119-0018, are the lowest surface gravity WDs ever found; both show Ca II absorption likely from accretion of circumbinary material. We predict that at least one of our WDs is an eclipsing detached double WD <span class="hlt">system</span>, important for constraining helium core WD models. Based on observations obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.461.3847G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.461.3847G"><span id="translatedtitle">Intermittent dipping in a <span class="hlt">low-mass</span> X-ray binary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galloway, Duncan K.; Ajamyan, Alishan N.; Upjohn, James; Stuart, Matthew</p> <p>2016-10-01</p> <p>Periodic dips observed in ≈20 per cent of <span class="hlt">low-mass</span> X-ray binaries (LMXBs) are thought to arise from obscuration of the neutron star by the outer edge of the accretion disc. We report the detection with the Rossi X-ray Timing Explorer of two dipping episodes in Aql X-1, not previously a known dipper. The X-ray spectrum during the dips exhibited an elevated neutral column density, by a factor between one and almost two orders of magnitude. Dips were not observed in every cycle of the 18.95-h orbit, so that the estimated frequency for these events is 0.10_{-0.05}^{+0.07} cycle-1. This is the first confirmed example of intermittent dipping in such a <span class="hlt">system</span>. Assuming that the dips in Aql X-1 occur because the <span class="hlt">system</span> inclination is intermediate between the non-dipping and dipping sources, implies a range of 72°-79° for the source. This result lends support for the presence of a massive (>2 M⊙) neutron star in Aql X-1, and further implies that ≈30 additional LMXBs may have inclinations within this range, raising the possibility of intermittent dips in those <span class="hlt">systems</span> also. Thus, we searched for dips from 24 other bursting <span class="hlt">systems</span>, without success. For the <span class="hlt">system</span> with the largest number of dip phases covered, 4U 1820-303, the non-detection implies a 95 per cent upper limit to the dip frequency of 1.4 × 10-3 cycle-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AAS...21537103B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AAS...21537103B"><span id="translatedtitle">The Behavior of Accretion Disks in <span class="hlt">Low</span> <span class="hlt">Mass</span> X-ray Binaries: Disk Winds and Alpha Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayless, Amanda J.</p> <p>2010-01-01</p> <p>This dissertation presents research on two <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binaries. The eclipsing <span class="hlt">low-mass</span> X-ray binary 4U 1822-371 is the prototypical accretion disk corona (ADC) <span class="hlt">system</span>. We have obtained new time-resolved UV spectroscopy with the ACS/SBC on the Hubble Space Telescope and new V- and J-band photometry with the 1.3-m SMARTS telescope at CTIO. We show that the accretion disk in the <span class="hlt">system</span> has a strong wind with projected velocities up to 4000 km/s as determined from the Doppler width of the C IV emission line. The broad and shallow eclipse indicates that the disk has a vertically-extended, optically-thick component at optical wavelengths. This component extends almost to the edge of the disk and has a height equal to 50% of the disk radius. As it has a low brightness temperature, we identify it as the optically-thick base of the disk wind. V1408 Aql (=4U 1957+115) is a <span class="hlt">low</span> <span class="hlt">mass</span> X-ray binary which continues to be a black hole candidate. We have new photometric data of this <span class="hlt">system</span> from the Otto Struve 2.1-m telescope's high speed CCD photometer at McDonald Observatory. The light curve is largely sinusoidal which we model with two components: a constant light source from the disk and a sinusoidal modulation at the orbital period from the irradiated face of the companion star. This is a radical re-interpretation of the orbital light curve. We do not require a large or asymmetric disk rim to account for the modulation in the light curve. Thus, the orbital inclination is unconstrained in our new model, removing the foundation for any claims of the compact object being a black hole.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.B13B0515M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.B13B0515M"><span id="translatedtitle">Tidal Timelines: Evolution of Terrestrial Exoplanet Habitability Around <span class="hlt">Low</span> <span class="hlt">Mass</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mullins, K.; Barnes, R.</p> <p>2009-12-01</p> <p>The range of orbits for planetary habitability have traditionally been based on the stellar flux that allows liquid water to persist on a planetary surface. However, when considering terrestrial (rocky) planets close to a <span class="hlt">low</span> <span class="hlt">mass</span> star (≤0.35M⊙), tidal effects must be considered because of the additional energy input from tidal heating. Of further interest is the time over which habitable conditions are generated by tidal interaction. Tides cause orbital evolution, during which the heat flux varies, which may cause the planet to migrate in and out of habitable zones and possibly result in sterilization. So, the heating history of a planet should be a consideration when searching for life-supporting planets. We apply heat flux limitations on habitability (based on observations within our solar <span class="hlt">system</span>) and tidally evolve planets across a range of initial conditions of orbits and masses. Our results provide a visualization of the time a planet has spent with a favorable amount of tidal heat for habitability and/or the amount of time until the heating is no longer conducive to habitability. As a greater number of close in terrestrial planets are found, these results can provide a method for identifying those planets with the highest potential for life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1664c0004K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1664c0004K"><span id="translatedtitle">Orientation birefringence of cross-linked rubber containing <span class="hlt">low-mass</span> compound</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kiyama, Ayumi; Nobukawa, Shogo; Yamauchi, Masayuki</p> <p>2015-05-01</p> <p>Molecular orientation of <span class="hlt">low-mass</span> compounds (LMCs) in a cross-linked rubber is studied in order to obtain the basic information on the dynamics of LMC molecules in a polymer beyond the glass transition temperature. A small amount of LMCs such as 4-cyano-4'-pentylbiphenyl (5CB), tricresylphosphate (TCP), and styrene-based tackifier (TF) is added into polybutadiene rubber (BR). After cross-linking reaction, the sheet samples are used to evaluate the orientation birefringence during stretching and stress relaxation. The rectangular films, cut out from the cross-linked sheets, are set in a uniaxial stretching machine equipped with an optical <span class="hlt">system</span> to measure both birefringence and tensile stress simultaneously. It is confirmed that orientation birefringence is proportional to the stress for not only pure cross-linked BR, but also cross-linked BR containing an LMC in a wide range of strain. Even after stretching, the birefringence does not change as far as the sample is kept at a constant strain. The results suggest that the LMC molecules are forced to orient with polymer chains by the strong intermolecular orientation correlation. Because of the LMC orientation, the stress-optical coefficient CR is enhanced by the addition of 5CB and TCP, but depressed by TF. Therefore, the LMC doping can be used to control the birefringence of a retardation film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.tmp.1092Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.tmp.1092Z&link_type=ABSTRACT"><span id="translatedtitle">The X-ray luminosity temperature relation of a complete sample of <span class="hlt">low</span> <span class="hlt">mass</span> galaxy clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zou, S.; Maughan, B. J.; Giles, P. A.; Vikhlinin, A.; Pacaud, F.; Burenin, R.; Hornstrup, A.</p> <p>2016-08-01</p> <p>We present Chandra observations of 23 galaxy groups and <span class="hlt">low-mass</span> galaxy clusters at 0.03 < z < 0.15 with a median temperature of ˜2 KeV. The sample is a statistically complete flux-limited subset of the 400 deg2 survey. We investigated the scaling relation between X-ray luminosity (L) and temperature (T), taking selection biases fully into account. The logarithmic slope of the bolometric L - T relation was found to be 3.29 ± 0.33, consistent with values typically found for samples of more massive clusters. In combination with other recent studies of the L - T relation we show that there is no evidence for the slope, normalisation, or scatter of the L - T relation of galaxy groups being different than that of massive clusters. The exception to this is that in the special case of the most relaxed <span class="hlt">systems</span>, the slope of the core-excised L - T relation appears to steepen from the self-similar value found for massive clusters to a steeper slope for the lower mass sample studied here. Thanks to our rigorous treatment of selection biases, these measurements provide a robust reference against which to compare predictions of models of the impact of feedback on the X-ray properties of galaxy groups.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...800...17F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...800...17F"><span id="translatedtitle">The Origin of Black Hole Spin in Galactic <span class="hlt">Low-mass</span> X-Ray Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fragos, T.; McClintock, J. E.</p> <p>2015-02-01</p> <p>Galactic field black hole (BH) <span class="hlt">low-mass</span> X-ray binaries (LMXBs) are believed to form in situ via the evolution of isolated binaries. In the standard formation channel, these <span class="hlt">systems</span> survived a common envelope phase, after which the remaining helium core of the primary star and the subsequently formed BH are not expected to be highly spinning. However, the measured spins of BHs in LMXBs cover the whole range of spin parameters. We propose here that the BH spin in LMXBs is acquired through accretion onto the BH after its formation. In order to test this hypothesis, we calculated extensive grids of detailed binary mass-transfer sequences. For each sequence, we examined whether, at any point in time, the calculated binary properties are in agreement with their observationally inferred counterparts of 16 Galactic LMXBs. The "successful" sequences give estimates of the mass that the BH has accreted since the onset of Roche-Lobe overflow. We find that in all Galactic LMXBs with measured BH spin, the origin of the spin can be accounted for by the accreted matter, and we make predictions about the maximum BH spin in LMXBs where no measurement is yet available. Furthermore, we derive limits on the maximum spin that any BH can have depending on current properties of the binary it resides in. Finally we discuss the implication that our findings have on the BH birth-mass distribution, which is shifted by ~1.5 M ⊙ toward lower masses, compared to the currently observed one.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DPS....4810506L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DPS....4810506L"><span id="translatedtitle"><span class="hlt">Low-mass</span> gas envelopes around accreting cores embedded in radiative 3D discs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lega, Elena; Lambrechts, Michiel</p> <p>2016-10-01</p> <p>Planets with a core mass larger than few Earth masses and a gaseous envelope not exceeding about 10% of the total mass budget are common. Such planets are present in the Solar <span class="hlt">System</span> (Uranus, Neptune) and are frequently observed around other stars.Our knowledge about the evolution of gas envelopes is mainly based on 1D models. However, such models cannot investigate the complex interaction between the forming envelope and the surrounding gas disc.In this work we perform 3D hydrodynamics simulations accounting for energy transfer and radiative cooling using the FARGOCA code (Lega et al., MNRAS 440, 2014). In addition to the usually considered heatingsources, namely viscous and compressional heating, we have modeled the energy deposited by the accretion of solids.We show that the thermal evolution of the envelope of a 5 Earth mass core is mainly dominated by compressional heating for accretion rates lower than 5 Earth masses per 105 years.Additionally, we demonstrate efficient gas circulation through the envelope. Under certain conditions, the competition between gas circulation and cooling of the envelope can efficiently delay the onset of runaway accretion. This could help in explaining the population of planets with <span class="hlt">low-mass</span> gas envelope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22521875','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22521875"><span id="translatedtitle">EVOLUTION OF TRANSIENT <span class="hlt">LOW-MASS</span> X-RAY BINARIES TO REDBACK MILLISECOND PULSARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jia, Kun; Li, Xiang-Dong</p> <p>2015-11-20</p> <p>Redback millisecond pulsars (MSPs; hereafter redbacks) are a subpopulation of eclipsing MSPs in close binaries. The formation processes of these <span class="hlt">systems</span> are not clear. The three pulsars showing transitions between rotation- and accretion-powered states belong to both redbacks and transient <span class="hlt">low-mass</span> X-ray binaries (LMXBs), suggesting a possible evolutionary link between them. Through binary evolution calculations, we show that the accretion disks in almost all LMXBs are subject to the thermal-viscous instability during certain evolutionary stages, and the parameter space for the disk instability covers the distribution of known redbacks in the orbital period—companion mass plane. We accordingly suggest that the abrupt reduction of the mass accretion rate during quiescence of transient LMXBs provides a plausible way to switch on the pulsar activity, leading to the formation of redbacks, if the neutron star has been spun up to be an energetic MSP. We investigate the evolution of redbacks, taking into account the evaporation feedback, and discuss its possible influence on the formation of black widow MSPs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.459.4378S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.459.4378S"><span id="translatedtitle"><span class="hlt">Low-mass</span> neutron stars: universal relations, the nuclear symmetry energy and gravitational radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silva, Hector O.; Sotani, Hajime; Berti, Emanuele</p> <p>2016-07-01</p> <p>The lowest neutron star masses currently measured are in the range 1.0-1.1 M⊙, but these measurement have either large uncertainties or refer to isolated neutron stars. The recent claim of a precisely measured mass M/M⊙ = 1.174 ± 0.004 (Martinez et al. 2015) in a double neutron star <span class="hlt">system</span> suggests that <span class="hlt">low-mass</span> neutron stars may be an interesting target for gravitational-wave detectors. Furthermore, Sotani et al. recently found empirical formulas relating the mass and surface redshift of non-rotating neutron stars to the star's central density and to the parameter η ≡ (K0L2)1/3, where K0 is the incompressibility of symmetric nuclear matter and L is the slope of the symmetry energy at saturation density. Motivated by these considerations, we extend the work by Sotani et al. to slowly rotating and tidally deformed neutron stars. We compute the moment of inertia, quadrupole moment, quadrupole ellipticity, tidal and rotational Love number and apsidal constant of slowly rotating neutron stars by integrating the Hartle-Thorne equations at second order in rotation, and we fit all of these quantities as functions of η and of the central density. These fits may be used to constrain η, either via observations of binary pulsars in the electromagnetic spectrum, or via near-future observations of inspiralling compact binaries in the gravitational-wave spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013RAA....13.1471Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013RAA....13.1471Y"><span id="translatedtitle">The <span class="hlt">low-mass</span> classic Algol-type binary UU Leo revisited</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Yuan-Gui</p> <p>2013-12-01</p> <p>New multi-color photometry of the eclipsing binary UU Leo, acquired from 2010 to 2013, was carried out by using the 60-cm and 85-cm telescopes at the Xinglong station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, the photometric solution was derived from BVR light curves. The results imply that UU Leo is a semi-detached Algol-type binary, with a mass ratio of q = 0.100(±0.002). The change in orbital period was reanalyzed based on all available eclipsing times. The O - C curve could be described by an upward parabola superimposed on a quasi-sinusoidal curve. The period and semi-amplitudes are Pmod = 54.5(±1.1) yr and A = 0.0273d(±0.0015d), which may be attributed to the light-time effect via the presence of an invisible third body. The long-term period increases at a rate of dP/dt = +4.64(±0.14) × 10-7d yr-1, which may be interpreted by the conserved mass being transferred from the secondary to the primary. With mass being transferred, the <span class="hlt">low-mass</span> Algol-type binary UU Leo may evolve into a binary <span class="hlt">system</span> with a main sequence star and a helium white dwarf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ESS.....311006F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ESS.....311006F"><span id="translatedtitle">Discovery of four new <span class="hlt">low-mass</span> white-dwarf companions in the Kepler data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faigler, Simchon; Kull, Ilya; Mazeh, Tsevi; Kiefer, Flavien; Latham, David W.; Bloemen, Steven</p> <p>2015-12-01</p> <p>We report the discovery of four new short-period eclipsing <span class="hlt">systems</span> in the Kepler light curves, consisting of an A-star primary and a <span class="hlt">low-mass</span> white-dwarf (WD) secondary (dA+WD) - KIC 4169521, KOI-3818, KIC 2851474 and KIC 9285587. These add to the 6 Kepler, and 19 non-Kepler, previously known short-period eclipsing dA+WD binaries.The discoveries were made through searching the light curves of bright Kepler stars for BEaming, Ellipsoidal and Reflection (BEER) modulations that are consistent with a compact companion, using the BEER search algorithm. This was followed by inspection of the search top hits, looking for eclipsing <span class="hlt">systems</span> with a secondary eclipse deeper than the primary one, as expected for a WD that is hotter than the primary star. Follow-up spectroscopic radial-velocity (RV) observations confirmed the binarity of the <span class="hlt">systems</span>. We derive the <span class="hlt">systems</span>' parameters through analyses of the light curves' eclipses and phase modulations, combined with RV orbital solutions and stellar evolution models.The four <span class="hlt">systems</span>' orbital periods of 1.17-3.82 days and WD masses of 0.19-0.22 Msun are similar to those reported for the previously known <span class="hlt">systems</span>. These values are consistent with evolution models of such <span class="hlt">systems</span>, that undergo a stable mass transfer from the WD progenitor to the current A star.For KIC 4169521 we derive a bloated WD radius of 0.09 Rsun that is well within the WD radius range of 0.04-0.43 Rsun of the known <span class="hlt">systems</span>. For the remaining three <span class="hlt">systems</span> we report WD radii of 0.026-0.035 Rsun, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries.As suggested before, the previously known <span class="hlt">systems</span>, together with KIC 4169521, all with hot and bloated WD secondaries, represent young <span class="hlt">systems</span> probably at a proto-WD, or initial WD cooling track stage. The other three new <span class="hlt">systems</span> - KOI-3818, KIC 2851474, and KIC 9285587, are probably positioned further along the WD cooling track, and extend the known population to older <span class="hlt">systems</span> with cooler</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......216A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......216A"><span id="translatedtitle">Identification and characterization of <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs using Virtual Observatory tools</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aberasturi, Miriam</p> <p>2015-11-01</p> <p> around each source based on assumed separations, mass ratio distributions and orientations of the <span class="hlt">systems</span>. Results: The main conclusion from this dissertation is that the Virtual Observatory has proved to be an excellent research methodology in the field of <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs. In particular, it allowed an efficient management of the queries to different catalogues and archives as well as the estimation of physical parameters through VO-tools. In the first publication we present the identification of 31 brown dwarf (25 known and 6 strong candidates not previously reported in the literature) identified in the sky area in common toWISE, 2MASS and SDSS. This is a remarkable number considering that 2MASS has been extensively searched for ultracool dwarfs and clearly show how new surveys and the use of VO tools can help to mine older surveys. The robustness of our methodology was confirmed with the spectroscopic confirmation of our candidate targets making it an ideal technique to identify brown dwarfs and, by extension, other rare objects. In the second paper, we show the potential of the VO and a purely photometric approach for finding new bright, nearby M dwarfs that escaped previous surveys mostly based on proper motions. We discover 24 new potential targets for exoplanet hunting (7 at less than 20 pc), 12 of which have been included in the CARMENES input catalogue of M dwarfs. We also identify three young very <span class="hlt">low-mass</span> stars (M4-M5 spectral types) in the Taurus-Auriga region and a wide (110 AU) binary <span class="hlt">system</span>. In the third paper we infer an upper limit for the binary fraction of >T5 dwarfs of <16 - < 25% depending of the underlying mass ratio distribution. This binary fraction is consistent with previous estimations. From this work we also conclude that theWFC3 is more sensitive to cool companions than otherHST instruments like NICMOS or WFPC2 but its lower angular resolution makes it unsuitable to detect tight brown dwarf binary <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT.......216A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhDT.......216A&link_type=ABSTRACT"><span id="translatedtitle">Identification and characterization of <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs using Virtual Observatory tools</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aberasturi, Miriam</p> <p>2015-11-01</p> <p> around each source based on assumed separations, mass ratio distributions and orientations of the <span class="hlt">systems</span>. Results: The main conclusion from this dissertation is that the Virtual Observatory has proved to be an excellent research methodology in the field of <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs. In particular, it allowed an efficient management of the queries to different catalogues and archives as well as the estimation of physical parameters through VO-tools. In the first publication we present the identification of 31 brown dwarf (25 known and 6 strong candidates not previously reported in the literature) identified in the sky area in common toWISE, 2MASS and SDSS. This is a remarkable number considering that 2MASS has been extensively searched for ultracool dwarfs and clearly show how new surveys and the use of VO tools can help to mine older surveys. The robustness of our methodology was confirmed with the spectroscopic confirmation of our candidate targets making it an ideal technique to identify brown dwarfs and, by extension, other rare objects. In the second paper, we show the potential of the VO and a purely photometric approach for finding new bright, nearby M dwarfs that escaped previous surveys mostly based on proper motions. We discover 24 new potential targets for exoplanet hunting (7 at less than 20 pc), 12 of which have been included in the CARMENES input catalogue of M dwarfs. We also identify three young very <span class="hlt">low-mass</span> stars (M4-M5 spectral types) in the Taurus-Auriga region and a wide (110 AU) binary <span class="hlt">system</span>. In the third paper we infer an upper limit for the binary fraction of >T5 dwarfs of <16 ‑ < 25% depending of the underlying mass ratio distribution. This binary fraction is consistent with previous estimations. From this work we also conclude that theWFC3 is more sensitive to cool companions than otherHST instruments like NICMOS or WFPC2 but its lower angular resolution makes it unsuitable to detect tight brown dwarf binary <span class="hlt">systems</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21367345','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21367345"><span id="translatedtitle">DETECTABILITY OF TRANSITING JUPITERS AND <span class="hlt">LOW-MASS</span> ECLIPSING BINARIES IN SPARSELY SAMPLED PAN-STARRS-1 SURVEY DATA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dupuy, Trent J.; Liu, Michael C.</p> <p>2009-10-20</p> <p>We present detailed simulations of the Pan-STARRS-1 (PS1) multi-epoch, multiband 3pi Survey in order to assess its potential yield of transiting planets and eclipsing binaries. This survey differs from dedicated transit surveys in that it will cover the entire northern sky but provide only sparsely sampled light curves. Since most eclipses would be detected at only a single epoch, the 3pi Survey will be most sensitive to deep eclipses (approx>0.10 mag) caused by Jupiters transiting M dwarfs and eclipsing stellar/substellar binaries. The survey will measure parallaxes for the approx4 x 10{sup 5} stars within 100 pc, which will enable a volume-limited eclipse search, reducing the number of astrophysical false positives compared with previous magnitude-limited searches. Using the best available empirical data, we constructed a model of the extended solar neighborhood that includes stars, brown dwarfs, and a realistic binary population. We computed the yield of deeply eclipsing <span class="hlt">systems</span> using both a semianalytic and a full Monte Carlo approach. We examined statistical tests for detecting single-epoch eclipses in sparsely sampled data and assessed their vulnerability to false positives due to stellar variability. Assuming a short-period planet frequency of 0.5% for M dwarfs, our simulations predict that about a dozen transiting Jupiters around <span class="hlt">low-mass</span> stars (M {sub *} < 0.3 M {sub sun}) within 100 pc are potentially detectable in the PS1 3pi Survey, along with approx300 <span class="hlt">low-mass</span> eclipsing binaries (both component masses <0.5 M {sub sun}), including approx10 eclipsing field brown dwarfs. Extensive follow-up observations would be required to characterize these candidate eclipsing <span class="hlt">systems</span>, thereby enabling comprehensive tests of structural models and novel insights into the planetary architecture of <span class="hlt">low-mass</span> stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997A%26A...319..547D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997A%26A...319..547D"><span id="translatedtitle"><span class="hlt">Protostellar</span> binary fragmentation: a comparison of results from two distinct second-order hydrodynamic codes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di G. Sigalotti, L.; Klapp, J.</p> <p>1997-03-01</p> <p>A new second-order Eulerian code is compared with a version of the TREESPH code formulated by Hernquist & Katz (1989ApJS...70..419H) for the standard isothermal collapse test. The results indicate that both codes produce a very similar evolution ending with the formation of a <span class="hlt">protostellar</span> binary <span class="hlt">system</span>. Contrary to previous first-order calculations, the binary forms by direct fragmentation, i.e., without the occurrence of an intermediate bar configuration. A similar trend was also found in recent second-order Eulerian calculations (Myhill & Boss 1993ApJS...89..345M), suggesting that it is a result of the decreased numerical diffusion associated with the new second-order schemes. The results have also implications on the differences between the finite difference methods and the particle method SPH, raised by Monaghan & Lattanzio (1986A&A...158..207M) for this problem. In particular, the Eulerian calculation does not result in a run-away collapse of the fragments, and as found in the TREESPH evolution, they also show a clear tendency to get closer together. In agreement with previous SPH calculations (Monaghan & Lattanzio 1986A&A...158..207M), the results of the long term evolution with code TREESPH show that the gravitational interaction between the two fragments may become important, and eventually induce the binary to coalesce. However, most recent SPH calculations (Bate, Bonnell & Price 1995MNRAS.277..362B ) indicate that the two fragments, after having reached a minimum separation distance, do not merge but continue to orbit each other.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GApFD.110..274Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GApFD.110..274Y"><span id="translatedtitle">On the mechanism of self gravitating Rossby interfacial waves in <span class="hlt">proto-stellar</span> accretion discs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yellin-Bergovoy, Ron; Heifetz, Eyal; Umurhan, Orkan M.</p> <p>2016-05-01</p> <p>The dynamical response of edge waves under the influence of self-gravity is examined in an idealized two-dimensional model of a <span class="hlt">proto-stellar</span> disc, characterized in steady state as a rotating vertically infinite cylinder of fluid with constant density except for a single density interface at some radius r0. The fluid in basic state is prescribed to rotate with a Keplerian profile $\\Omega_k(r)\\sim r^{-3/2}$ modified by some additional azimuthal sheared flow. A linear analysis shows that there are two azimuthally propagating edge waves, kin to the familiar Rossby waves and surface gravity waves in terrestrial studies, which move opposite to one another with respect to the local basic state rotation rate at the interface. Instability only occurs if the radial pressure gradient is opposite to that of the density jump (unstably stratified) where self-gravity acts as a wave stabilizer irrespective of the stratification of the <span class="hlt">system</span>. The propagation properties of the waves are discussed in detail in the language of vorticity edge waves. The roles of both Boussinesq and non-Boussinesq effects upon the stability and propagation of these waves with and without the inclusion of self-gravity are then quantified. The dynamics involved with self-gravity non- Boussinesq effect is shown to be a source of vorticity production where there is a jump in the basic state density, in addition, self-gravity also alters the dynamics via the radial main pressure gradient, which is a Boussinesq effect . Further applications of these mechanical insights are presented in the conclusion including the ways in which multiple density jumps or gaps may or may not be stable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22370331','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22370331"><span id="translatedtitle">Herschel photometry of disks around <span class="hlt">low-mass</span> stars in the R CrA cloud</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harvey, Paul M.; Henning, Thomas; Liu, Yao; Wolf, Sebastian E-mail: nje@astro.as.utexas.edu E-mail: yliu@pmo.ac.cn E-mail: yliu@pmo.ac.cn</p> <p>2014-11-01</p> <p>We report photometric results from a subset of a Herschel-PACS program to observe cool dust in disks around <span class="hlt">low-mass</span> stars as a complement to our earlier program to measure far-infrared emission from brown dwarfs. In this latest study we observed five <span class="hlt">low-mass</span> objects in the nearby R Corona Australis region and detected at least three at 70 μm. Using a Monte Carlo radiative transfer code we have investigated the disk masses and geometry based on detailed spectral energy distribution (SED) modeling, and we compare these new results to those from our earlier larger sample of brown dwarfs. In particular, our SED analysis for these five objects shows again that disk geometries of brown dwarfs or <span class="hlt">low-mass</span> stars are generally similar to their higher mass counterparts like T Tauri disks, but the range of disk mass extends to well below the value found in T Tauri stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21467163','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21467163"><span id="translatedtitle">OGLE-2005-BLG-153: MICROLENSING DISCOVERY AND CHARACTERIZATION OF A VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> BINARY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hwang, K.-H.; Han, C.; Ryu, Y.-H.; Udalski, A.; Kubiak, M.; Szymanski, M. K.; Pietrzynski, G.; Soszynski, I.; Szewczyk, O.; Ulaczyk, K.; Wyrzykowski, L.; Bond, I. A.; Beaulieu, J.-P.; Dominik, M.; Horne, K.; Gould, A.; Gaudi, B. S.; Abe, F.; Botzler, C. S.; Hearnshaw, J. B.</p> <p>2010-11-01</p> <p>The mass function and statistics of binaries provide important diagnostics of the star formation process. Despite this importance, the mass function at <span class="hlt">low</span> <span class="hlt">masses</span> remains poorly known due to observational difficulties caused by the faintness of the objects. Here we report the microlensing discovery and characterization of a binary lens composed of very <span class="hlt">low</span> <span class="hlt">mass</span> stars just above the hydrogen-burning limit. From the combined measurements of the Einstein radius and microlens parallax, we measure the masses of the binary components of 0.10 {+-} 0.01 M{sub sun} and 0.09 {+-} 0.01 M{sub sun}. This discovery demonstrates that microlensing will provide a method to measure the mass function of all Galactic populations of very <span class="hlt">low</span> <span class="hlt">mass</span> binaries that is independent of the biases caused by the luminosity of the population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012hcxa.confE..34T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012hcxa.confE..34T"><span id="translatedtitle">A New Sample of <span class="hlt">Low-Mass</span> AGNs Selected by X-ray Variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Terashima, Yuichi</p> <p>2012-09-01</p> <p>We present results from our attempts to search for AGN containing relatively <span class="hlt">low-mass</span> black holes (BHs) using X-ray variability. Variability time scales inversely correlate with black hole mass and can be used to select <span class="hlt">low-mass</span> objects. We utilize the second XMM-Newton serendipitous source catalogue, which contains 262902 unique sources, to select highly variable objects. Black hole masses are derived by using the correlation between BH mass and normalized excess variance, where the effect of break in power spectra is properly taken into account. We present the sample selection and results of analysis including discovery of candidate <span class="hlt">low-mass</span> AGNs with mass lower than 2e6 Msolar. We also present results on a peculiar AGN candidate showing soft thermal emission only found in our survey.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19790056900&hterms=cell+plastic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dcell%2Bplastic','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19790056900&hterms=cell+plastic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dcell%2Bplastic"><span id="translatedtitle">Ultra-<span class="hlt">low-mass</span> flexible planar solar arrays using 50-micron-thick solar cells</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Costogue, E. N.; Rayl, G.</p> <p>1978-01-01</p> <p>A conceptual design study has been completed which has shown the feasibility of ultra-<span class="hlt">low-mass</span> planar solar arrays with specific power of 200 watts/kilogram. The beginning of life (BOL) power output of the array designs would be 10 kW at 1 astronomical unit (AU) and a 55C deg operating temperature. Two designs were studied: a retractable rollout design and a non-retractable fold-out. The designs employed a flexible <span class="hlt">low-mass</span> blanket and <span class="hlt">low-mass</span> structures. The blanket utilized 2 x 2 cm high-efficiency (13.5% at 28C deg AM0), ultra-thin (50 micron), silicon solar cells protected by thin (75 micron) plastic encapsulants. The structural design utilized the 'V'-stiffened approach which allows a lower mass boom to be used. In conjunction with the conceptual design, modules using the thin cells and plastic encapsulant were designed and fabricated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...818..179L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...818..179L"><span id="translatedtitle">Evidence for the Rapid Formation of <span class="hlt">Low-mass</span> Early-type Galaxies in Dense Environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Yiqing; Peng, Eric W.; Blakeslee, John; Côté, Patrick; Ferrarese, Laura; Jordán, Andrés; Puzia, Thomas H.; Toloba, Elisa; Zhang, Hong-Xin</p> <p>2016-02-01</p> <p>We explore the environmental dependence of star formation timescales in <span class="hlt">low-mass</span> galaxies using the [α/Fe] abundance ratio as an evolutionary clock. We present integrated [α/Fe] measurements for 11 <span class="hlt">low-mass</span> ({M}\\star ˜ {10}9 {M}⊙ ) early-type galaxies (ETGs) with a large range of cluster-centric distance in the Virgo Cluster. We find a gradient in [α/Fe], where the galaxies closest to the cluster center (the cD galaxy, M87) have the highest values. This trend is driven by galaxies within a projected radius of 0.4 Mpc (0.26 times the virial radius of Virgo A), all of which have super-solar [α/Fe]. Galaxies in this mass range exhibit a large scatter in the [α/Fe]-σ diagram, and do not obviously lie on an extension of the relation defined by massive ETGs. In addition, we find a correlation between [α/Fe] and globular cluster specific frequency (SN), suggesting that <span class="hlt">low-mass</span> ETGs that formed their stars over a short period of time were also efficient at forming massive star clusters. The innermost <span class="hlt">low-mass</span> ETGs in our sample have [α/Fe] values comparable to that of M87, implying that environment is the controlling factor for star formation timescales in dense regions. These <span class="hlt">low-mass</span> galaxies could be the surviving counterparts of the objects that have already been accreted into the halo of M87, and may be the link between present-day <span class="hlt">low-mass</span> galaxies and the old, metal-poor, high-[α/Fe], high-SN stellar populations seen in the outer halos of massive ETGs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005sfet.confE..42O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005sfet.confE..42O"><span id="translatedtitle">The <span class="hlt">low-mass</span> star and disk populations in NGC 6611</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oliveira, Joana</p> <p>2005-07-01</p> <p>The aim of our observational program is to find empirical answers to two major questions. Do regions of high-mass star formation also produce lots of solar- and <span class="hlt">low-mass</span> stars, i.e. is the <span class="hlt">low-mass</span> IMF unaffected by high-mass siblings? Can <span class="hlt">low-mass</span> stars in hostile environments retain circumstellar disks? We present results of our survey of NGC 6611, a massive cluster with an age of approximately 2 Myr which is currently ionizing the Eagle nebula. This cluster contains a dozen O-stars that emit 10 times more ionizing radiation than the Trapezium, providing a challenging environment for their lower-mass siblings. Our dataset consists of wide field optical and near infrared imaging, intermediate resolution spectroscopy (ESO-VLT) and deep L-band photometry. We have photometrically selected solar- and <span class="hlt">low-mass</span> stars, placed them on the HR diagram and determined the IMF over an area sufficient to deal with mass segregation. We show that the IMF in NGC6611 is similar to that of the Orion Nebula Cluster down to 0.5Msun. Using K-L indices we search for colour excesses that betray the presence of circumstellar material and study what fraction of solar-mass stars still possess disks as a function of age and proximity to the massive stars. By comparing the disk frequency in NGC6611 with similarly aged but quieter regions, we find no evidence that the harsher environment of NGC6611 significantly hastens disk dissipation. Apparently the massive stars in NGC6611 have no global effect on the probability of <span class="hlt">low-mass</span> star formation or disk retention. We have an approved HST program that will allows us to investigate the very <span class="hlt">low-mass</span> and brown dwarf populations in NGC6611. And we complement our IR imaging with Spitzer/ORAC data, extending the area of our ground-based survey.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IAUS..314..203P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IAUS..314..203P"><span id="translatedtitle">Constraining X-ray-Induced Photoevaporation of Protoplanetary Disks Orbiting <span class="hlt">Low-Mass</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Punzi, Kristina M.; Kastner, Joel H.; Rodriguez, David; Principe, David A.; Vican, Laura</p> <p>2016-01-01</p> <p><span class="hlt">Low-mass</span>, pre-main sequence stars possess intense high-energy radiation fields as a result of their strong stellar magnetic activity. This stellar UV and X-ray radiation may have a profound impact on the lifetimes of protoplanetary disks. We aim to constrain the X-ray-induced photoevaporation rates of protoplanetary disks orbiting <span class="hlt">low-mass</span> stars by analyzing serendipitous XMM-Newton and Chandra X-ray observations of candidate nearby (D < 100 pc), young (age < 100 Myr) M stars identified in the GALEX Nearby Young-Star Survey (GALNYSS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070032626&hterms=iron&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Diron','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070032626&hterms=iron&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Diron"><span id="translatedtitle">Mass-Radius Relationships for <span class="hlt">Low-Mass</span> Planets: From Iron Planets to Water Planets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuchner, Marc</p> <p>2007-01-01</p> <p>Transit observations, and radial velocity measurements, have begun to populate the mass radius diagram for extrasolar planets; fubture astrometric measurements and direct images promise more mass and radius information. Clearly, the bulk density of a planet indicates something about a planet s composition--but what? I will attempt to answer this question in general for <span class="hlt">low-mass</span> planets (<Neptune mass) using a combination of analytic and numerical calculations, and I will show that all <span class="hlt">low-mass</span> planets obey a kind of universal mass-radius relationship: an expansion whose first term is M approx. R(sup 3).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22723607S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22723607S"><span id="translatedtitle">3-D MHD disk wind simulations of <span class="hlt">protostellar</span> jets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Staff, Jan E.; Koning, Nico; Ouyed, Rachid; Tanaka, Kei; Tan, Jonathan C.</p> <p>2016-01-01</p> <p>We present the results of large scale, three-dimensional magnetohydrodynamics simulations of disk winds for different initial magnetic field configurations. The jets are followed from the source to distances, which are resolvable by HST and ALMA observations. Our simulations show that jets are heated along their length by many shocks. The mass of the protostar is a free parameter that can be inserted in the post processing of the data, and we apply the simulations to both <span class="hlt">low</span> <span class="hlt">mass</span> and high mass protostars. For the latter we also compute the expected diagnostics when the outflow is photoionized by the protostar. We compute the emission lines that are produced, and find excellent agreement with observations. For a one solar mass protostar, we find the jet width to be between 20 and 30 au while the maximum velocities perpendicular to the jet are found to be 100 km s-1. The initially less open magnetic field configuration simulations result in a wider, two-component jet; a cylindrically shaped outer jet surrounding a narrow and much faster, inner jet. For the initially most open magnetic field configuration the kink mode creates a narrow corkscrew-like jet without a clear Keplerian rotation profile and even regions where we observe rotation opposite to the disk (counter-rotating). This is not seen in the less open field configurations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ARep...57..818K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ARep...57..818K"><span id="translatedtitle">Modeling of the formation of complex molecules in <span class="hlt">protostellar</span> objects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kochina, O. V.; Wiebe, D. S.; Kalenskii, S. V.; Vasyunin, A. I.</p> <p>2013-11-01</p> <p>The results of molecular composition modeling are presented for the well studied <span class="hlt">low-mass</span> star-forming region TMC-1 and the massive star-forming region DR21(OH), which is poorly studied from a chemical point of view. The column densities of dozens of molecules, ranging from simple diatomic to complex organic molecules, are reproduced to within an order of magnitude using a one-dimensional model for the physical and chemical structure of these regions. The chemical ages of the regions are approximately 105 years in both cases. The main desorption mechanisms that are usually included in chemical models (photodesorption, thermal desorption, and cosmic-ray-induced desorption) do not provide sufficient gasphase abundances of molecules that are synthesized in surface reactions; however, this shortcoming can be removed by introducing small amount of reactive desorption into the model. It is possible to reproduce the properties of the TMC-1 chemical composition in a standard model, without requiring additional assumptions about an anomalous C/O ratio or the recent accretion of matter enriched with atomic carbon, as has been proposed by some researchers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040013167&hterms=density+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Ddensity%2Bchemistry','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040013167&hterms=density+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Ddensity%2Bchemistry"><span id="translatedtitle">Gas Heating, Chemistry and Photoevaporation in <span class="hlt">Protostellar</span> Disks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hollenbach, David</p> <p>2004-01-01</p> <p>We model the thermal balance, the chemistry, and the radiative transfer in dusty disks orbiting young, <span class="hlt">low</span> <span class="hlt">mass</span> stars. These models are motivated by observations of infrared and ultraviolet transitions of H2 from protoplanetary disks, as well as millimeter and submillimeter observations of other molecules such as CO, and infrared continuum observations of the dust. The dust grains are heated primarily by the stellar radiation and the infrared radiation field produced by the dust itself. The gas is heated by collisions with warmer dust grains, X-rays from the region close to the stellar surface, UV pumping of hydrogen molecules, and the grain photoelectric heating mechanism initiated by UV photons from the central star. We treat cases where the gas to dust ratio is high, because the dust has settled to the midplane and coagulated into relatively large objects. We discuss situations in which the infrared emission from H2 can be detected, and how the comparison of the observations with our models can deduce physical parameters such as the mass and the density and temperature distribution of the gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22712107F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22712107F"><span id="translatedtitle">The MUSCLES Treasury Survey: Temporally- and Spectrally-Resolved Irradiance from <span class="hlt">Low-mass</span> Exoplanet Host Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>France, Kevin; Parke Loyd, R. O.; Youngblood, Allison; Linsky, Jeffrey; MUSCLES Treasury Survey Team</p> <p>2016-01-01</p> <p>The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. High-energy photons (X-ray to near-UV; 5 - 3200 Ang) from these stars regulate the atmospheric temperature profiles and photochemistry on orbiting planets, influencing the production of potential "biomarker" gases. It has been shown that the atmospheric signatures of potentially habitable planets around <span class="hlt">low-mass</span> stars may be significantly different from planets orbiting Sun-like stars owing to the different UV spectral energy distribution. I will present results from a panchromatic survey (Hubble/Chandra/XMM/optical) of M and K dwarf exoplanet hosts, the MUSCLES Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of <span class="hlt">Low-mass</span> Exoplanetary <span class="hlt">Systems</span>). We reconstruct the Lyman-alpha and extreme-UV (100-900 Ang) radiation lost to interstellar attenuation and create 5 Angstrom to 5 micron stellar irradiance spectra; these data will be publically available as a High-Level Science Product on MAST. We find that all <span class="hlt">low-mass</span> exoplanet host stars exhibit significant chromospheric/transition region/coronal emission -- no "UV inactive" M dwarfs are observed. The F(far-UV)/F(near-UV) flux ratio, a driver for possible abiotic production of the suggested biomarkers O2 and O3, increases by ~3 orders of magnitude as the habitable zone moves inward from 1 to 0.1 AU, while the incident far-UV (912 - 1700 Ang) and XUV (5 - 900 Ang) radiation field strengths decrease by factors of a few across this range. Far-UV flare activity is common in 'optically inactive' M dwarfs; statistics from the entire sample indicate that large UV flares (E(300 - 1700 Ang) >= 10^31 erg) occur several times per day on typical M dwarf exoplanet hosts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2228599F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2228599F"><span id="translatedtitle">Ultraviolet and X-ray Activity and Flaring on <span class="hlt">Low-Mass</span> Exoplanet Host Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>France, Kevin; Parke Loyd, R. O.; Brown, Alexander</p> <p>2015-08-01</p> <p>The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. High-energy photons (X-ray to NUV) from these stars regulate the atmospheric temperature profiles and photochemistry on orbiting planets, influencing the production of potential “biomarker” gases. We present results from the MUSCLES Treasury Survey, an ongoing study of time-resolved UV and X-ray spectroscopy of nearby M and K dwarf exoplanet host stars. This program uses contemporaneous Hubble Space Telescope and Chandra (or XMM) observations to characterize the time variability of the energetic radiation field incident on the habitable zones planetary <span class="hlt">systems</span> at d < 15 pc. We find that all exoplanet host stars observed to date exhibit significant levels of chromospheric and transition region UV emission. M dwarf exoplanet host stars display 30 - 2000% UV emission line amplitude variations on timescales of minutes-to-hours. The relative flare/quiescent UV flux amplitudes on old (age > 1 Gyr) planet-hosting M dwarfs are comparable to active flare stars (e.g., AD Leo), despite their lack of flare activity at visible wavelengths. We also detect similar UV flare behavior on a subset of our K dwarf exoplanet host stars. We conclude that strong flares and stochastic variability are common, even on “optically inactive” M dwarfs hosting planetary <span class="hlt">systems</span>. These results argue that the traditional assumption of weak UV fields and low flare rates on older <span class="hlt">low-mass</span> stars needs to be revised.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.451.3836D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.451.3836D"><span id="translatedtitle">The complex chemistry of outflow cavity walls exposed: the case of <span class="hlt">low-mass</span> protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drozdovskaya, Maria N.; Walsh, Catherine; Visser, Ruud; Harsono, Daniel; van Dishoeck, Ewine F.</p> <p>2015-08-01</p> <p>Complex organic molecules are ubiquitous companions of young <span class="hlt">low-mass</span> protostars. Recent observations suggest that their emission stems, not only from the traditional hot corino, but also from offset positions. In this work, 2D physicochemical modelling of an envelope-cavity <span class="hlt">system</span> is carried out. Wavelength-dependent radiative transfer calculations are performed and a comprehensive gas-grain chemical network is used to simulate the physical and chemical structure. The morphology of the <span class="hlt">system</span> delineates three distinct regions: the cavity wall layer with time-dependent and species-variant enhancements; a torus rich in complex organic ices, but not reflected in gas-phase abundances and the remaining outer envelope abundant in simpler solid and gaseous molecules. Strongly irradiated regions, such as the cavity wall layer, are subject to frequent photodissociation in the solid phase. Subsequent recombination of the photoproducts leads to frequent reactive desorption, causing gas-phase enhancements of several orders of magnitude. This mechanism remains to be quantified with laboratory experiments. Direct photodesorption is found to be relatively inefficient. If radicals are not produced directly in the icy mantle, the formation of complex organics is impeded. For efficiency, a sufficient number of FUV photons needs to penetrate the envelope, and elevated cool dust temperatures need to enable grain-surface radical mobility. As a result, a high stellar luminosity and a sufficiently wide cavity favour chemical complexity. Furthermore within this paradigm, complex organics are demonstrated to have unique lifetimes and be grouped into early (formaldehyde, ketene, methanol, formic acid, methyl formate, acetic acid and glycolaldehyde) and late (acetaldehyde, dimethyl ether and ethanol) species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21301447','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21301447"><span id="translatedtitle">THE BROWN DWARF KINEMATICS PROJECT. II. DETAILS ON NINE WIDE COMMON PROPER MOTION VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> COMPANIONS TO NEARBY STARS ,</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Faherty, Jacqueline K.; Shara, Michael M.; Burgasser, Adam J.; West, Andrew A.; Bochanski, John J.; Cruz, Kelle L.; Walter, Frederick M.</p> <p>2010-01-15</p> <p>We report on nine wide common proper motion <span class="hlt">systems</span> containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new <span class="hlt">systems</span>. The ages of these <span class="hlt">systems</span> are determined using diagnostics for both stellar primaries and <span class="hlt">low-mass</span> secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of {approx}25,000 AU making it one of the widest and lowest binding energy <span class="hlt">systems</span> known to date. The <span class="hlt">system</span> containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows H{alpha} activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. Two of the nine <span class="hlt">systems</span> have discrepant component ages that emerge from stellar or ultracool diagnostics indicating possible shortcomings in our understanding of the age diagnostics of stars and brown dwarfs. We find a resolved binary frequency for widely separated (>100 AU) <span class="hlt">low-mass</span> companions (i.e., at least a triple <span class="hlt">system</span>) which is at least twice the frequency found for the field ultracool dwarf population. The ratio of triples to binaries and quadruples to binaries is also high for this sample: 3:5 and 1:4, respectively, compared to 8 pc sample values of 1:4 and 1:26. The additional components in these wide companion <span class="hlt">systems</span> indicates a formation mechanism that requires a third or fourth component to maintain gravitational stability or facilitate the exchange of angular momentum. The binding energies for the nine multiples discussed in this text are among the lowest known for wide <span class="hlt">low-mass</span> <span class="hlt">systems</span>, suggesting that weakly bound, low-to-intermediate mass (0.2 M {sub sun} < M {sub tot}< 1.0 M {sub sun}) multiples can form and survive to exist in the field (1-8 Gyr)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AJ....139..176F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AJ....139..176F"><span id="translatedtitle">The Brown Dwarf Kinematics Project. II. Details on Nine Wide Common Proper Motion Very <span class="hlt">Low</span> <span class="hlt">Mass</span> Companions to Nearby Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faherty, Jacqueline K.; Burgasser, Adam J.; West, Andrew A.; Bochanski, John J.; Cruz, Kelle L.; Shara, Michael M.; Walter, Frederick M.</p> <p>2010-01-01</p> <p>We report on nine wide common proper motion <span class="hlt">systems</span> containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new <span class="hlt">systems</span>. The ages of these <span class="hlt">systems</span> are determined using diagnostics for both stellar primaries and <span class="hlt">low-mass</span> secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of ~25,000 AU making it one of the widest and lowest binding energy <span class="hlt">systems</span> known to date. The <span class="hlt">system</span> containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows Hα activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. Two of the nine <span class="hlt">systems</span> have discrepant component ages that emerge from stellar or ultracool diagnostics indicating possible shortcomings in our understanding of the age diagnostics of stars and brown dwarfs. We find a resolved binary frequency for widely separated (>100 AU) <span class="hlt">low-mass</span> companions (i.e., at least a triple <span class="hlt">system</span>) which is at least twice the frequency found for the field ultracool dwarf population. The ratio of triples to binaries and quadruples to binaries is also high for this sample: 3:5 and 1:4, respectively, compared to 8 pc sample values of 1:4 and 1:26. The additional components in these wide companion <span class="hlt">systems</span> indicates a formation mechanism that requires a third or fourth component to maintain gravitational stability or facilitate the exchange of angular momentum. The binding energies for the nine multiples discussed in this text are among the lowest known for wide <span class="hlt">low-mass</span> <span class="hlt">systems</span>, suggesting that weakly bound, low-to-intermediate mass (0.2 M sun < M tot< 1.0 M sun) multiples can form and survive to exist in the field (1-8 Gyr). This paper includes data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011adap.prop...54H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011adap.prop...54H"><span id="translatedtitle">Lense-Thirring precession in neutron-star <span class="hlt">low-mass</span> X-ray binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Homan, Jeroen</p> <p></p> <p>Quasi-periodic oscillations (QPOs) with low frequencies (0.01-70 Hz) have been observed in the X-ray light curves of most neutron-star and black-hole <span class="hlt">low-mass</span> X-ray binaries. Despite having been discovered more than 25 years ago, their origin is still not well understood. Similarities between the low-frequency QPOs in the two types of <span class="hlt">systems</span> suggest that they have a common origin in the accretion flows around black holes and neutron stars. Some of the proposed models that attempt to explain low- frequency QPOs invoke a General Relativistic effect known as Lense-Thirring precession (or "frame dragging"). However, for Lense-Thirring precession to produce substantial modulations of the X-ray flux through relativistic beaming and gravitational lensing, the rotation axis of the inner part of the accretion disk needs to have a substantial tilt (10-20 degrees) with respect to the spin axis of the compact object. We argue that observational evidence for such titled inner accretion disks can be found in the variability of neutron- star <span class="hlt">low-mass</span> X-ray binaries that are viewed at inclination angles of 60-80 degrees. In these <span class="hlt">systems</span> low-frequency QPOs at ~0.1-15 Hz are observed that modulate the emission from the neutron star by quasi-periodic obscuration, presumably by a titled inner disc. The goal of our proposed program is to test whether the frequency evolution and spectral state dependence of these QPOs is similar to what is observed for the low-frequency QPOs that are observed in lower-inclination neutron-star X-ray binaries. To make such a comparison, we need to better characterize the properties and behavior of these QPOs. Our study will make use of almost 1300 RXTE observations of 11 sources, totaling 5.7 Ms of data. Signatures of strong gravity have long been sought after in accreting compact objects. While strong evidence from spectral features has emerged in the last decade (e.g. gravitationally broadened iron emission lines), there have only been hints of such</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010yCat..35150013R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010yCat..35150013R"><span id="translatedtitle">VizieR Online Data Catalog: Very <span class="hlt">low</span> <span class="hlt">mass</span> objects in ONC (Rodriguez-Ledesma+, 2010)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodriguez-Ledesma, M. V.; Mundt, R.; Eisloeffel, J.</p> <p>2010-01-01</p> <p>Table 1 lists the 638 very <span class="hlt">low</span> <span class="hlt">mass</span> objects in the Orion Nebula Cluster with magnitudes between 14-21mag in I band for which NIR (JHK) photometry is available. The I band data is from Rodriguez-Ledesma et al. (2009, Cat. <J/A+A/502/883>) and JHK data from 2MASS, UKIDSS, and VLT. (1 data file).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21392470','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21392470"><span id="translatedtitle">A SPITZER SEARCH FOR SUBSTELLAR COMPANIONS TO <span class="hlt">LOW-MASS</span> WHITE DWARFS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kilic, Mukremin; Brown, Warren R.; McLeod, B.</p> <p>2010-01-01</p> <p>The formation scenarios for single <span class="hlt">low-mass</span> (M < 0.45 M{sub sun}) white dwarfs (WDs) include enhanced mass loss from a metal-rich progenitor star or a common envelope phase of a solar-like star with a close-in massive planet or a brown dwarf. Both scenarios suggest that <span class="hlt">low-mass</span> WDs may have planets. Here, we present a Spitzer IRAC search for substellar and planetary mass companions to 14 <span class="hlt">low-mass</span> WDs. One of our targets, HS 1653+7753, displays near- and mid-infrared flux excess. However, follow-up MMT observations show that this excess is due to a nearby resolved source, which is mostly likely a background object. Another target, PG 2257+162, shows flux excess compatible with a late-type stellar companion. We do not detect substellar companions to any of the remaining targets. In addition, eight of these stars do not show any radial velocity variations, ruling out stellar mass companions including other WDs. We conclude that a significant fraction of the <span class="hlt">low-mass</span> WDs in our sample do not have stellar or massive brown dwarf companions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.718d2026I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.718d2026I"><span id="translatedtitle">TREX-DM: a low background Micromegas-based TPC for <span class="hlt">low-mass</span> WIMP detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iguaz, F. J.; Garza, J. G.; Aznar, F.; Castel, J. F.; Cebrián, S.; Dafni, T.; García, J. A.; Irastorza, I. G.; Lagraba, A.; Luzón, G.; Peiró, A.</p> <p>2016-05-01</p> <p>Dark Matter experiments are recently focusing their detection techniques in <span class="hlt">low-mass</span> WIMPs, which requires the use of light elements and low energy threshold. In this context, we describe the TREX-DM experiment, a low background Micromegas-based TPC for <span class="hlt">low-mass</span> WIMP detection. Its main goal is the operation of an active detection mass ~0.3 kg, with an energy threshold below 0.4 keVee and fully built with previously selected radiopure materials. This work describes the commissioning of the actual setup situated in a laboratory on surface and the updates needed for a possible physics run at the Canfranc Underground Laboratory (LSC) in 2016. A preliminary background model of TREX-DM is also presented, based on a Geant4 simulation, the simulation of the detector’s response and two discrimination methods: a conservative muon/electron and one based on a neutron source. Based on this background model, TREX-DM could be competitive in the search for <span class="hlt">low-mass</span> WIMPs. In particular it could be sensitive, e.g., to the <span class="hlt">low-mass</span> WIMP interpretation of the DAMA/LIBRA and other hints in a conservative scenario.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040033921','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040033921"><span id="translatedtitle">Relativistic Astrophysics in Black Hole and <span class="hlt">Low-Mass</span> Neutron Star X-ray Binaries</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2000-01-01</p> <p>During the five-year period, our study of "Relativistic Astrophysics in Black Hole and <span class="hlt">Low-Mass</span> Neutron Star X-ray Binaries" has been focused on the following aspects: observations, data analysis, Monte-Carlo simulations, numerical calculations, and theoretical modeling. Most of the results of our study have been published in refereed journals and conference presentations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010yCat..35260029H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010yCat..35260029H"><span id="translatedtitle">VizieR Online Data Catalog: ASAS <span class="hlt">low-mass</span> eclipsing binaries light curves (Helminiak+, 2011)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Helminiak, K. G.; Konacki, M.</p> <p>2010-09-01</p> <p>Photometric observations of two newly-discovered <span class="hlt">low-mass</span> eclipsing binaries: ASAS J045304-0700.4 (ASAS-04) and ASAS J082552-1622.8 (ASAS-08). V and I band curves were obtained in January 2008 with the 1.0-m Elizabeth telescope and its STE4 camera at the South African Astronomical Observatory (SAAO). (4 data files).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/418689','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/418689"><span id="translatedtitle">Collision safety of a hard-shell <span class="hlt">low-mass</span> vehicle</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kaeser, R.; Walz, F.H.; Brunner, A.</p> <p>1994-06-01</p> <p><span class="hlt">Low-mass</span> vehicles and in particular <span class="hlt">low-mass</span> electric vehicles as produced today in very small quantities are in general not designed for crashworthiness in collisions. Particular problems of compact <span class="hlt">low-mass</span> cars are: reduced length of the car front, <span class="hlt">low</span> <span class="hlt">mass</span> compared to other vehicles, and heavy batteries in the case of an electric car. With the intention of studying design improvements, three frontal crash tests were run last year: the first one with a commercial, lightweight electric car; the second with a reinforced version of the same car; and the last one with a car based on a different structural design with a `hard-shell` car body. Crash tests showed that the latter solution made better use of the small zone available for continuous energy absorption. The paper discusses further the problem of frontal collisions between vehicles of different weight and, in particular, the side collision. A side-collision test was run with the hard-shell vehicle following the ECE lateral-impact test procedure at 50 km/h and led to results for the EuroSIDI-dummy well below current injury tolerance criteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ATel.9072....1B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ATel.9072....1B"><span id="translatedtitle">Outburst from <span class="hlt">low-mass</span> X-ray binary GRS 1747-312 in Terzan 6</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bahramian, A.; Heinke, C. O.; Sivakoff, G. R.; Kennea, J. A.; Wijnands, R.; Altamirano, D.</p> <p>2016-05-01</p> <p>GRS 1747-312 is an eclipsing transient <span class="hlt">low-mass</span> X-ray binary in the core of the globular cluster Terzan 6. This source shows regular outbursts ~ every 6 months and, due to its eclipsing behaviour, has an accurately-constrained orbital period (12.36 hrs, in't Zand et al. 2003, A & A, 406, 233).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2256653F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2256653F"><span id="translatedtitle">The origin of Black-Hole Spin in Galactic <span class="hlt">Low-Mass</span> X-ray Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fragos, Tassos; McClintock, Jeffrey</p> <p>2015-08-01</p> <p>Galactic field <span class="hlt">low-mass</span> X-ray binaries (LMXBs), like the ones for which black hole (BH) spin measurements are available, are believed to form in situ via the evolution of isolated binaries. In the standard formation channel, these <span class="hlt">systems</span> survived a common envelope phase, after which the remaining helium core of the primary star and the subsequently formed BH are not expected to be highly spinning. However, the measured spins of BHs in LMXBs cover the whole range of spin parameters from a*~0 to a*1. In this talk I propose that the BH spin in LMXBs is acquired through accretion onto the BH during its long stable accretion phase. In order to test this hypothesis, I calculated extensive grids of binary evolutionary sequences in which a BH accretes matter from a close companion. For each evolutionary sequence, I examined whether, at any point in time, the calculated binary properties are in agreement with their observationally inferred counterparts of observed Galactic LMXBs with BH spin measurements. Mass-transfer sequences that simultaneously satisfy all observational constraints represent possible progenitors of the considered LMXBs and thus give estimates of the amount of matter that the BH has accreted since the onset of Roche-Lobe overflow. I find that in all Galactic LMXBs with measured BH spin, the origin of the spin can be accounted by the accreted matter. Furthermore, based on this hypothesis, I derive limits on the maximum spin that a BH can have depending on the orbital period of the binary it resides in, and give predictions on the maximum possible BH spin of Galactic LMXBs where a BH spin measurement is not yet available. Finally I will discuss the implication that our findings have on the birth black hole mass distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25567282','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25567282"><span id="translatedtitle">The temperature and chronology of heavy-element synthesis in <span class="hlt">low-mass</span> stars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Neyskens, P; Van Eck, S; Jorissen, A; Goriely, S; Siess, L; Plez, B</p> <p>2015-01-01</p> <p>Roughly half of the heavy elements (atomic mass greater than that of iron) are believed to be synthesized in the late evolutionary stages of stars with masses between 0.8 and 8 solar masses. Deep inside the star, nuclei (mainly iron) capture neutrons and progressively build up (through the slow-neutron-capture process, or s-process) heavier elements that are subsequently brought to the stellar surface by convection. Two neutron sources, activated at distinct temperatures, have been proposed: (13)C and (22)Ne, each releasing one neutron per α-particle ((4)He) captured. To explain the measured stellar abundances, stellar evolution models invoking the (13)C neutron source (which operates at temperatures of about one hundred million kelvin) are favoured. Isotopic ratios in primitive meteorites, however, reflecting nucleosynthesis in the previous generations of stars that contributed material to the Solar <span class="hlt">System</span>, point to higher temperatures (more than three hundred million kelvin), requiring at least a late activation of (22)Ne (ref. 1). Here we report a determination of the s-process temperature directly in evolved <span class="hlt">low-mass</span> giant stars, using zirconium and niobium abundances, independently of stellar evolution models. The derived temperature supports (13)C as the s-process neutron source. The radioactive pair (93)Zr-(93)Nb used to estimate the s-process temperature also provides, together with the pair (99)Tc-(99)Ru, chronometric information on the time elapsed since the start of the s-process, which we determine to be one million to three million years. PMID:25567282</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22258612','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22258612"><span id="translatedtitle">Gravitational detection of a <span class="hlt">low-mass</span> dark satellite galaxy at cosmological distance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vegetti, S; Lagattuta, D J; McKean, J P; Auger, M W; Fassnacht, C D; Koopmans, L V E</p> <p>2012-01-19</p> <p>The mass function of dwarf satellite galaxies that are observed around Local Group galaxies differs substantially from simulations based on cold dark matter: the simulations predict many more dwarf galaxies than are seen. The Local Group, however, may be anomalous in this regard. A massive dark satellite in an early-type lens galaxy at a redshift of 0.222 was recently found using a method based on gravitational lensing, suggesting that the mass fraction contained in substructure could be higher than is predicted from simulations. The lack of very <span class="hlt">low-mass</span> detections, however, prohibited any constraint on their mass function. Here we report the presence of a (1.9 ± 0.1) × 10(8) M dark satellite galaxy in the Einstein ring <span class="hlt">system</span> JVAS B1938+666 (ref. 11) at a redshift of 0.881, where M denotes the solar mass. This satellite galaxy has a mass similar to that of the Sagittarius galaxy, which is a satellite of the Milky Way. We determine the logarithmic slope of the mass function for substructure beyond the local Universe to be 1.1(+0.6)(-0.4), with an average mass fraction of 3.3(+3.6)(-1.8) per cent, by combining data on both of these recently discovered galaxies. Our results are consistent with the predictions from cold dark matter simulations at the 95 per cent confidence level, and therefore agree with the view that galaxies formed hierarchically in a Universe composed of cold dark matter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HEAD...1420505F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HEAD...1420505F"><span id="translatedtitle">The Origin of Black-Hole Spin in Galactic <span class="hlt">Low-Mass</span> X-ray Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fragos, Tassos; McClintock, Jeffrey E.; Narayan, Ramesh</p> <p>2014-08-01</p> <p>Galactic field <span class="hlt">low-mass</span> X-ray binaries (LMXBs), like the ones for which black hole (BH) spin measurements are available, are believed to form in situ via the evolution of isolated binaries. In the standard formation channel, these <span class="hlt">systems</span> survived a common envelope phase, after which the remaining helium core of the primary star and the subsequently formed BH are not expected to be highly spinning. However, the measured spins of BHs in LMXBs cover the whole range of spin parameters from a 0 to a*1. In this talk I propose that the BH spin in LMXBs is acquired through accretion onto the BH during its long stable accretion phase. In order to test this hypothesis, I calculated extensive grids of binary evolutionary sequences in which a BH accretes matter from a close companion. For each evolutionary sequence, I examined whether, at any point in time, the calculated binary properties are in agreement with their observationally inferred counterparts of observed Galactic LMXBs with BH spin measurements. Mass-transfer sequences that simultaneously satisfy all observational constraints represent possible progenitors of the considered LMXBs and thus give estimates of the amount of matter that the BH has accreted since the onset of Roche-Lobe overflow. I find that in all Galactic LMXBs with measured BH spin, the origin of the spin can be accounted by the accreted matter. Furthermore, based on this hypothesis, I derive limits on the maximum spin that a BH can have depending on the orbital period of the binary it resides in, and give predictions on the maximum possible BH spin of Galactic LMXBs where a BH spin measurement is not yet available. Finally I will discuss the implication that our findings have on the birth black hole mass distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25567282','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25567282"><span id="translatedtitle">The temperature and chronology of heavy-element synthesis in <span class="hlt">low-mass</span> stars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Neyskens, P; Van Eck, S; Jorissen, A; Goriely, S; Siess, L; Plez, B</p> <p>2015-01-01</p> <p>Roughly half of the heavy elements (atomic mass greater than that of iron) are believed to be synthesized in the late evolutionary stages of stars with masses between 0.8 and 8 solar masses. Deep inside the star, nuclei (mainly iron) capture neutrons and progressively build up (through the slow-neutron-capture process, or s-process) heavier elements that are subsequently brought to the stellar surface by convection. Two neutron sources, activated at distinct temperatures, have been proposed: (13)C and (22)Ne, each releasing one neutron per α-particle ((4)He) captured. To explain the measured stellar abundances, stellar evolution models invoking the (13)C neutron source (which operates at temperatures of about one hundred million kelvin) are favoured. Isotopic ratios in primitive meteorites, however, reflecting nucleosynthesis in the previous generations of stars that contributed material to the Solar <span class="hlt">System</span>, point to higher temperatures (more than three hundred million kelvin), requiring at least a late activation of (22)Ne (ref. 1). Here we report a determination of the s-process temperature directly in evolved <span class="hlt">low-mass</span> giant stars, using zirconium and niobium abundances, independently of stellar evolution models. The derived temperature supports (13)C as the s-process neutron source. The radioactive pair (93)Zr-(93)Nb used to estimate the s-process temperature also provides, together with the pair (99)Tc-(99)Ru, chronometric information on the time elapsed since the start of the s-process, which we determine to be one million to three million years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22364263','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22364263"><span id="translatedtitle">THE ORIGIN OF BLACK HOLE SPIN IN GALACTIC <span class="hlt">LOW-MASS</span> X-RAY BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fragos, T.; McClintock, J. E.</p> <p>2015-02-10</p> <p>Galactic field black hole (BH) <span class="hlt">low-mass</span> X-ray binaries (LMXBs) are believed to form in situ via the evolution of isolated binaries. In the standard formation channel, these <span class="hlt">systems</span> survived a common envelope phase, after which the remaining helium core of the primary star and the subsequently formed BH are not expected to be highly spinning. However, the measured spins of BHs in LMXBs cover the whole range of spin parameters. We propose here that the BH spin in LMXBs is acquired through accretion onto the BH after its formation. In order to test this hypothesis, we calculated extensive grids of detailed binary mass-transfer sequences. For each sequence, we examined whether, at any point in time, the calculated binary properties are in agreement with their observationally inferred counterparts of 16 Galactic LMXBs. The ''successful'' sequences give estimates of the mass that the BH has accreted since the onset of Roche-Lobe overflow. We find that in all Galactic LMXBs with measured BH spin, the origin of the spin can be accounted for by the accreted matter, and we make predictions about the maximum BH spin in LMXBs where no measurement is yet available. Furthermore, we derive limits on the maximum spin that any BH can have depending on current properties of the binary it resides in. Finally we discuss the implication that our findings have on the BH birth-mass distribution, which is shifted by ∼1.5 M {sub ☉} toward lower masses, compared to the currently observed one.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22258612','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22258612"><span id="translatedtitle">Gravitational detection of a <span class="hlt">low-mass</span> dark satellite galaxy at cosmological distance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vegetti, S; Lagattuta, D J; McKean, J P; Auger, M W; Fassnacht, C D; Koopmans, L V E</p> <p>2012-01-19</p> <p>The mass function of dwarf satellite galaxies that are observed around Local Group galaxies differs substantially from simulations based on cold dark matter: the simulations predict many more dwarf galaxies than are seen. The Local Group, however, may be anomalous in this regard. A massive dark satellite in an early-type lens galaxy at a redshift of 0.222 was recently found using a method based on gravitational lensing, suggesting that the mass fraction contained in substructure could be higher than is predicted from simulations. The lack of very <span class="hlt">low-mass</span> detections, however, prohibited any constraint on their mass function. Here we report the presence of a (1.9 ± 0.1) × 10(8) M dark satellite galaxy in the Einstein ring <span class="hlt">system</span> JVAS B1938+666 (ref. 11) at a redshift of 0.881, where M denotes the solar mass. This satellite galaxy has a mass similar to that of the Sagittarius galaxy, which is a satellite of the Milky Way. We determine the logarithmic slope of the mass function for substructure beyond the local Universe to be 1.1(+0.6)(-0.4), with an average mass fraction of 3.3(+3.6)(-1.8) per cent, by combining data on both of these recently discovered galaxies. Our results are consistent with the predictions from cold dark matter simulations at the 95 per cent confidence level, and therefore agree with the view that galaxies formed hierarchically in a Universe composed of cold dark matter. PMID:22258612</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21464574','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21464574"><span id="translatedtitle">THE FREQUENCY OF <span class="hlt">LOW-MASS</span> EXOPLANETS. II. THE 'PERIOD VALLEY'</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wittenmyer, Robert A.; Tinney, C. G.; Bailey, J.; O'Toole, Simon J.; Jones, H. R. A.; Butler, R. P.; Carter, B. D.</p> <p>2010-10-20</p> <p>Radial-velocity planet search campaigns are now beginning to detect <span class="hlt">low-mass</span> 'Super-Earth' planets, with minimum masses M sin i{approx}< 10 M{sub +}. Using two independently developed methods, we have derived detection limits from nearly four years of the highest-precision data on 24 bright, stable stars from the Anglo-Australian Planet Search. Both methods are more conservative than a human analyzing an individual observed data set, as is demonstrated by the fact that both techniques would detect the radial-velocity signals announced as exoplanets for the 61 Vir <span class="hlt">system</span> in 50% of trials. There are modest differences between the methods which can be recognized as arising from particular criteria that they adopt. What both processes deliver is a quantitative selection process such that one can use them to draw quantitative conclusions about planetary frequency and orbital parameter distribution from a given data set. Averaging over all 24 stars, in the period range P< 300 days and the eccentricity range 0.0 < e < 0.6, we could detect 99% of planets with velocity amplitudes K{approx}> 7.1 m s{sup -1}. For the best stars in the sample, we are able to detect or exclude planets with K{approx}> 3 m s{sup -1}, corresponding to minimum masses of 8 M{sub +} (P = 5 days) or 17 M{sub +} (P = 50 days). Our results indicate that the observed 'period valley', a lack of giant planets (M > 100 M{sub +}) with periods between 10 and 100 days, is indeed real. However, for planets in the mass range 10-100 M{sub +}, our results suggest that the deficit of such planets may be a result of selection effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22127033','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22127033"><span id="translatedtitle">ALIGNMENT BETWEEN FLATTENED <span class="hlt">PROTOSTELLAR</span> INFALL ENVELOPES AND AMBIENT MAGNETIC FIELDS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chapman, Nicholas L.; Matthews, Tristan G.; Novak, Giles; Davidson, Jacqueline A.; Goldsmith, Paul F.; Houde, Martin; Kwon, Woojin; Looney, Leslie W.; Li Zhiyun; Matthews, Brenda; Peng Ruisheng; Vaillancourt, John E.; Volgenau, Nikolaus H.</p> <p>2013-06-20</p> <p>We present 350 {mu}m polarization observations of four <span class="hlt">low-mass</span> cores containing Class 0 protostars: L483, L1157, L1448-IRS2, and Serp-FIR1. This is the second paper in a larger survey aimed at testing magnetically regulated models for core-collapse. One key prediction of these models is that the mean magnetic field in a core should be aligned with the symmetry axis (minor axis) of the flattened young stellar object inner envelope (aka pseudodisk). Furthermore, the field should exhibit a pinched or hourglass-shaped morphology as gravity drags the field inward toward the central protostar. We combine our results for the four cores with results for three similar cores that were published in the first paper from our survey. An analysis of the 350 {mu}m polarization data for the seven cores yields evidence of a positive correlation between mean field direction and pseudodisk symmetry axis. Our rough estimate for the probability of obtaining by pure chance a correlation as strong as the one we found is about 5%. In addition, we combine together data for multiple cores to create a source-averaged magnetic field map having improved signal-to-noise ratio, and this map shows good agreement between mean field direction and pseudodisk axis (they are within 15 Degree-Sign ). We also see hints of a magnetic pinch in the source-averaged map. We conclude that core-scale magnetic fields appear to be strong enough to guide gas infall, as predicted by the magnetically regulated models. Finally, we find evidence of a positive correlation between core magnetic field direction and bipolar outflow axis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22078430','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22078430"><span id="translatedtitle">THE HERSCHEL AND IRAM CHESS SPECTRAL SURVEYS OF THE <span class="hlt">PROTOSTELLAR</span> SHOCK L1157-B1: FOSSIL DEUTERATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Codella, C.; Fontani, F.; Vasta, M.; Ceccarelli, C.; Lefloch, B.; Kahane, C.; Taquet, V.; Wiesenfeld, L.; Caselli, P.; Lis, D.; Viti, S.</p> <p>2012-09-20</p> <p>We present the first study of deuteration toward the <span class="hlt">protostellar</span> shock L1157-B1, based on spectral surveys performed with the Herschel-HIFI and IRAM 30 m telescopes. The L1157 outflow is driven by a <span class="hlt">low-mass</span> Class 0 protostar and is considered the prototype of the so-called chemically active outflows. The young (2000 yr), bright blueshifted bow shock, B1, is an ideal laboratory for studying the gas chemically enriched by the release of dust mantles due to the passage of a shock. A total of 12 emission lines (up to E{sub u} = 63 K) of CH{sub 2}DOH, HDCO, and DCN are detected. In addition, two lines of NH{sub 2}D and HDO are tentatively reported. To estimate the deuteration, we also extracted from our spectral survey emission lines of non-deuterated isotopologues ({sup 13}CH{sub 3}OH, H{sub 2} {sup 13}CO, H{sup 13}CN, H{sub 2} {sup 13}CO, and NH{sub 3}). We infer higher deuteration fractions for CH{sub 3}OH (D/H = 0.2-2 Multiplication-Sign 10{sup -2}) and H{sub 2}CO (5-8 Multiplication-Sign 10{sup -3}) than for H{sub 2}O (0.4-2 Multiplication-Sign 10{sup -3}), HCN ({approx}10{sup -3}), and ammonia ({<=}3 Multiplication-Sign 10{sup -2}). The measurement of deuteration of water, formaldehyde, and methanol in L1157-B1 provides a fossil record of the gas before it was shocked by the jet driven by the protostar. A comparison with gas-grain models indicates that the gas passed through a low-density ({<=}10{sup 3} cm{sup -3}) phase, during which the bulk of water ices formed, followed by a phase of increasing density, up to 3 Multiplication-Sign 10{sup 4} cm{sup -3}, during which formaldehyde and methanol ices formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ARep...60..879E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ARep...60..879E"><span id="translatedtitle">Variations in the accretion rate and luminosity in gravitationally unstable <span class="hlt">protostellar</span> disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elbakyan, V. G.; Vorobyov, E. I.; Glebova, G. M.</p> <p>2016-10-01</p> <p>Self-consistent modeling of a protostar and <span class="hlt">protostellar</span> disk is carried out for early stages of their evolution. The accretion rate at distances of sevral astronomical units from the protostar is appreciably variable, which is reflected in the protostar's luminosity. The amplitude of the variations in the accretion rate and luminosity grows together with the sampling period, as a consequence of the nature of gravitationally unstable <span class="hlt">protostellar</span> disks. A comparison of model luminosity variations with those derived from observations of nearby sites of star formation shows that the model variations are appreciably lower than the observed values for sampling periods of less than 10 years, indicating the presence of additional sources of variability on small dynamical distances from the protostar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.437.1561R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.437.1561R"><span id="translatedtitle">The role of <span class="hlt">low-mass</span> star clusters in forming the massive stars in DR 21</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rivilla, V. M.; Jiménez-Serra, I.; Martín-Pintado, J.; Sanz-Forcada, J.</p> <p>2014-01-01</p> <p>We have studied the young <span class="hlt">low-mass</span> pre-main sequence (PMS) stellar population associated with the massive star-forming region DR 21 by using archival X-ray Chandra observations and by complementing them with existing optical and infrared (IR) surveys. The Chandra observations have revealed for the first time a new highly extincted population of PMS <span class="hlt">low-mass</span> stars previously missed in observations at other wavelengths. The X-ray population exhibits three main stellar density peaks, coincident with the massive star-forming regions, being the DR 21 core the main peak. The cross-correlated X-ray/IR sample exhibits a radial `Spokes-like' stellar filamentary structure that extends from the DR 21 core towards the northeast. The near-IR data reveal a centrally peaked structure for the extinction, which exhibits its maximum in the DR 21 core and gradually decreases with the distance to the N-S cloud axis and to the cluster centre. We find evidence of a global mass segregation in the full <span class="hlt">low-mass</span> stellar cluster, and of a stellar age segregation, with the youngest stars still embedded in the N-S cloud, and more evolved stars more spatially distributed. The results are consistent with the scenario where an elongated overall potential well created by the full <span class="hlt">low-mass</span> stellar cluster funnels gas through filaments feeding stellar formation. Besides the full gravitational well, smaller scale local potential wells created by dense stellar sub-clusters of <span class="hlt">low-mass</span> stars are privileged in the competition for the gas of the common reservoir, allowing the formation of massive stars. We also discuss the possibility that a stellar collision in the very dense stellar cluster revealed by Chandra in the DR 21 core is the origin of the large-scale and highly energetic outflow arising from this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AAS...21714426R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AAS...21714426R"><span id="translatedtitle">A Chandra Search for <span class="hlt">Low-mass</span> Companions of Late B Stars in Tr 16</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Remage Evans, Nancy; DeGioia-Eastwood, K.; Gagne, M.; Townsley, L.; Wolk, S.; Naze, Y.; Broos, P.; Corcoran, M.; Oskinova, L.; Moffat, A. F. J.; Wang, J.; Walborn, N.</p> <p>2011-01-01</p> <p>The cluster Tr 16 is included within the area of the large survey of the Carina region with Chandra (PI: Townsley). Stars later than B3 are not known to produce X-rays. On the other hand, <span class="hlt">low</span> <span class="hlt">mass</span> stars (later than mid-F spectral type) produce copious X-rays when they are young. We have developed a list of B3 to A0 stars in the young cluster Tr 16 which: 1.) are within 3' of Eta Car, 2.) have an appropriate V and B-V combination (including a range of +/- 0.1 in E(B-V), and 3.) have proper motions consistent with cluster membership. We have identified stars from this list which are X-ray sources on a 90 ksec Chandra image of Tr 16. Presumably the X-rays are produced by a <span class="hlt">low</span> <span class="hlt">mass</span> companion, at least in nearly all cases. This attribution is reinforced by the fact that the X-ray sources have higher median temperatures than O and early B sources. In addition, the spectral fits to 4 strongest sources produce temperatures typical of <span class="hlt">low-mass</span> coronal sources. On this basis, 39% of the late B stars have <span class="hlt">low</span> <span class="hlt">mass</span> companions. Interpretation of this number depends on the completeness of the X-ray detections, however discussion of the <span class="hlt">low</span> <span class="hlt">mass</span> stars in Tr 16 indicates that stars which will be M stars on the main sequence are detected. N. Evans acknowledges support from the Chandra X-ray Center NASA Contract NAS8-03060</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26536957','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26536957"><span id="translatedtitle">Episodic molecular outflow in the very young <span class="hlt">protostellar</span> cluster Serpens South.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Plunkett, Adele L; Arce, Héctor G; Mardones, Diego; van Dokkum, Pieter; Dunham, Michael M; Fernández-López, Manuel; Gallardo, José; Corder, Stuartt A</p> <p>2015-11-01</p> <p>The loss of mass from protostars, in the form of a jet or outflow, is a necessary counterpart to <span class="hlt">protostellar</span> mass accretion. Outflow ejection events probably vary in their velocity and/or in the rate of mass loss. Such 'episodic' ejection events have been observed during the class 0 <span class="hlt">protostellar</span> phase (the early accretion stage), and continue during the subsequent class I phase that marks the first one million years of star formation. Previously observed episodic-ejection sources were relatively isolated; however, the most common sites of star formation are clusters. Outflows link protostars with their environment and provide a viable source of the turbulence that is necessary for regulating star formation in clusters, but it is not known how an accretion-driven jet or outflow in a clustered environment manifests itself in its earliest stage. This early stage is important in establishing the initial conditions for momentum and energy transfer to the environment as the protostar and cluster evolve. Here we report that an outflow from a young, class 0 protostar, at the hub of the very active and filamentary Serpens South <span class="hlt">protostellar</span> cluster, shows unambiguous episodic events. The (12)C(16)O (J = 2-1) emission from the protostar reveals 22 distinct features of outflow ejecta, the most recent having the highest velocity. The outflow forms bipolar lobes--one of the first detectable signs of star formation--which originate from the peak of 1-mm continuum emission. Emission from the surrounding C(18)O envelope shows kinematics consistent with rotation and an infall of material onto the protostar. The data suggest that episodic, accretion-driven outflow begins in the earliest phase of <span class="hlt">protostellar</span> evolution, and that the outflow remains intact in a very clustered environment, probably providing efficient momentum transfer for driving turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26536957','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26536957"><span id="translatedtitle">Episodic molecular outflow in the very young <span class="hlt">protostellar</span> cluster Serpens South.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Plunkett, Adele L; Arce, Héctor G; Mardones, Diego; van Dokkum, Pieter; Dunham, Michael M; Fernández-López, Manuel; Gallardo, José; Corder, Stuartt A</p> <p>2015-11-01</p> <p>The loss of mass from protostars, in the form of a jet or outflow, is a necessary counterpart to <span class="hlt">protostellar</span> mass accretion. Outflow ejection events probably vary in their velocity and/or in the rate of mass loss. Such 'episodic' ejection events have been observed during the class 0 <span class="hlt">protostellar</span> phase (the early accretion stage), and continue during the subsequent class I phase that marks the first one million years of star formation. Previously observed episodic-ejection sources were relatively isolated; however, the most common sites of star formation are clusters. Outflows link protostars with their environment and provide a viable source of the turbulence that is necessary for regulating star formation in clusters, but it is not known how an accretion-driven jet or outflow in a clustered environment manifests itself in its earliest stage. This early stage is important in establishing the initial conditions for momentum and energy transfer to the environment as the protostar and cluster evolve. Here we report that an outflow from a young, class 0 protostar, at the hub of the very active and filamentary Serpens South <span class="hlt">protostellar</span> cluster, shows unambiguous episodic events. The (12)C(16)O (J = 2-1) emission from the protostar reveals 22 distinct features of outflow ejecta, the most recent having the highest velocity. The outflow forms bipolar lobes--one of the first detectable signs of star formation--which originate from the peak of 1-mm continuum emission. Emission from the surrounding C(18)O envelope shows kinematics consistent with rotation and an infall of material onto the protostar. The data suggest that episodic, accretion-driven outflow begins in the earliest phase of <span class="hlt">protostellar</span> evolution, and that the outflow remains intact in a very clustered environment, probably providing efficient momentum transfer for driving turbulence. PMID:26536957</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...740..107C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...740..107C"><span id="translatedtitle">Radiation-hydrodynamic Simulations of Massive Star Formation with <span class="hlt">Protostellar</span> Outflows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cunningham, Andrew J.; Klein, Richard I.; Krumholz, Mark R.; McKee, Christopher F.</p> <p>2011-10-01</p> <p>We report the results of a series of adaptive mesh refinement radiation-hydrodynamic simulations of the collapse of massive star-forming clouds using the ORION code. These simulations are the first to include the feedback effects <span class="hlt">protostellar</span> outflows, as well as <span class="hlt">protostellar</span> radiative heating and radiation pressure exerted on the infalling, dusty gas. We find that outflows evacuate polar cavities of reduced optical depth through the ambient core. These enhance the radiative flux in the poleward direction so that it is 1.7-15 times larger than that in the midplane. As a result the radiative heating and outward radiation force exerted on the <span class="hlt">protostellar</span> disk and infalling cloud gas in the equatorial direction are greatly diminished. This simultaneously reduces the Eddington radiation pressure barrier to high-mass star formation and increases the minimum threshold surface density for radiative heating to suppress fragmentation compared to models that do not include outflows. The strength of both these effects depends on the initial core surface density. Lower surface density cores have longer free-fall times and thus massive stars formed within them undergo more Kelvin contraction as the core collapses, leading to more powerful outflows. Furthermore, in lower surface density clouds the ratio of the time required for the outflow to break out of the core to the core free-fall time is smaller, so that these clouds are consequently influenced by outflows at earlier stages of the collapse. As a result, outflow effects are strongest in low surface density cores and weakest in high surface density ones. We also find that radiation focusing in the direction of outflow cavities is sufficient to prevent the formation of radiation pressure-supported circumstellar gas bubbles, in contrast to models which neglect <span class="hlt">protostellar</span> outflow feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1029753','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1029753"><span id="translatedtitle">Radiation-Hydrodynamic Simulations of Massive Star Formation with <span class="hlt">Protostellar</span> Outflows</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cunningham, A J; Klein, R I; Krumholz, M R; McKee, C F</p> <p>2011-03-02</p> <p>We report the results of a series of AMR radiation-hydrodynamic simulations of the collapse of massive star forming clouds using the ORION code. These simulations are the first to include the feedback effects <span class="hlt">protostellar</span> outflows, as well as <span class="hlt">protostellar</span> radiative heating and radiation pressure exerted on the infalling, dusty gas. We find that that outflows evacuate polar cavities of reduced optical depth through the ambient core. These enhance the radiative flux in the poleward direction so that it is 1.7 to 15 times larger than that in the midplane. As a result the radiative heating and outward radiation force exerted on the <span class="hlt">protostellar</span> disk and infalling cloud gas in the equatorial direction are greatly diminished. The simultaneously reduces the Eddington radiation pressure barrier to high-mass star formation and increases the minimum threshold surface density for radiative heating to suppress fragmentation compared to models that do not include outflows. The strength of both these effects depends on the initial core surface density. Lower surface density cores have longer free-fall times and thus massive stars formed within them undergo more Kelvin contraction as the core collapses, leading to more powerful outflows. Furthermore, in lower surface density clouds the ratio of the time required for the outflow to break out of the core to the core free-fall time is smaller, so that these clouds are consequently influenced by outflows at earlier stages of collapse. As a result, outflow effects are strongest in low surface density cores and weakest in high surface density one. We also find that radiation focusing in the direction of outflow cavities is sufficient to prevent the formation of radiation pressure-supported circumstellar gas bubbles, in contrast to models which neglect <span class="hlt">protostellar</span> outflow feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.668a2094U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.668a2094U"><span id="translatedtitle"><span class="hlt">Low-mass</span> dimuon measurements in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Uras, Antonio</p> <p>2016-01-01</p> <p><span class="hlt">Low-mass</span> dimuon production, including light vector mesons ρ, ω, ϕ, provides key information on the hot and dense state of strongly interacting matter produced in high-energy heavy-ion collisions. In particular, strangeness production can be studied via ϕ meson measurements, while the detailed description of the full dimuon mass spectrum down to the kinematic threshold can be used to reveal in-medium modifications of hadron properties and the thermal emission arising from the medium. Measurements in pp and p-A <span class="hlt">systems</span>, in absence of hot nuclear matter effects, must be used as a reference to test our knowledge of the processes expected to contribute to dilepton production. Dimuon production is studied with the ALICE apparatus at the LHC at forward rapidity (2.5 < y < 4) with the Muon Spectrometer. In this contribution, results on <span class="hlt">low-mass</span> dimuon production are shown, for various center-of-mass energies per nucleon pair, in pp, p-Pb, and Pb-Pb collisions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.tmp.1481H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.tmp.1481H"><span id="translatedtitle">The discovery of a planetary candidate around the evolved <span class="hlt">low-mass</span> Kepler giant star HD 175370 ★</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hrudková, M.; Hatzes, A.; Karjalainen, R.; Lehmann, H.; Hekker, S.; Hartmann, M.; Tkachenko, A.; Prins, S.; Van Winckel, H.; De Nutte, R.; Dumortier, L.; Frémat, Y.; Hensberge, H.; Jorissen, A.; Lampens, P.; Laverick, M.; Lombaert, R.; Pápics, P. I.; Raskin, G.; Sódor, Á.; Thoul, A.; Van Eck, S.; Waelkens, C.</p> <p>2016-09-01</p> <p>We report on the discovery of a planetary companion candidate with a minimum mass M sin i = 4.6 ± 1.0 MJupiter orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our program to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coudé echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph HERMES of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 ± 4.5 days) variation with a semi-amplitude K = 133 ± 25 ms-1, superimposed on a long-term trend. A <span class="hlt">low-mass</span> stellar companion with an orbital period of ˜88 years in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-amplitude radial velocity variations and only future continued monitoring of this <span class="hlt">system</span> may answer this uncertainty. From Kepler photometry we find that HD 175370 is most likely a <span class="hlt">low-mass</span> red-giant branch or asymptotic-giant branch star.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AAS...22525732B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AAS...22525732B"><span id="translatedtitle">MINERVA-Red: A Census of Planets Orbiting the Nearest <span class="hlt">Low-mass</span> Stars to the Sun</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blake, Cullen; Johnson, John; Plavchan, Peter; Sliski, David; Wittenmyer, Robert A.; Eastman, Jason D.; Barnes, Stuart</p> <p>2015-01-01</p> <p>Recent results from Kepler and ground-based exoplanet surveys suggest that <span class="hlt">low-mass</span> stars host numerous small planets. Since <span class="hlt">low-mass</span> stars are intrinsically faint at optical wavelengths, obtaining the Doppler precision necessary to detect these companions remains a challenge for existing instruments. We describe MINERVA-Red, a project to use a dedicated, robotic, near-infrared optimized 0.7 meter telescope and a specialized Doppler spectrometer to carry out an intensive, multi-year campaign designed to reveal the planetary <span class="hlt">systems</span> orbiting some of the closest stars to the Sun. The MINERVA-Red cross-dispersed echelle spectrograph is optimized for the 'deep red', between 800 nm and 900 nm, where these stars are relatively bright. The instrument is very compact and designed for the ultimate in Doppler precision by using single-mode fiber input. We describe the spectrometer and the status of the MINERVA-Red project, which is expected to begin routine operations at Whipple Observatory on Mt Hopkins, Arizona, in 2015.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21455073','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21455073"><span id="translatedtitle">DISCOVERY OF A <span class="hlt">LOW-MASS</span> COMPANION TO A METAL-RICH F STAR WITH THE MARVELS PILOT PROJECT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fleming, Scott W.; Ge Jian; Mahadevan, Suvrath; Lee, Brian; Cuong Nguyen, Duy; Morehead, Robert C.; Wan Xiaoke; Zhao Bo; Liu Jian; Guo Pengcheng; Kane, Stephen R.; Eastman, Jason D.; Siverd, Robert J.; Scott Gaudi, B.; Niedzielski, Andrzej; Sivarani, Thirupathi; Stassun, Keivan G.; Gary, Bruce; Wolszczan, Alex; Barnes, Rory</p> <p>2010-08-01</p> <p>We report the discovery of a <span class="hlt">low-mass</span> companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) pilot project. The host star has an effective temperature T{sub eff} = 6135 {+-} 40 K, logg = 4.4 {+-} 0.1, and [Fe/H] = 0.32 {+-} 0.01, indicating a mass of M = 1.25 {+-} 0.09 M{sub sun} and R = 1.15 {+-} 0.15 R{sub sun}. The companion has an orbital period of 5.69449 {+-} 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M{sub J} , and thus may be an example of the rare class of brown dwarfs orbiting at distances comparable to those of 'Hot Jupiters'. We present relative photometry that demonstrates that the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius {approx}>0.8 R{sub J} at the 95% confidence level. Tidal analysis of the <span class="hlt">system</span> suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first <span class="hlt">low-mass</span> companion detected with a multi-object, dispersed, fixed-delay interferometer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/943820','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/943820"><span id="translatedtitle">Molecular Line Emission from Massive <span class="hlt">Protostellar</span> Disks: Predictions for ALMA and the EVLA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krumholz, M R; Klein, R I; McKee, C F</p> <p>2007-05-07</p> <p>We compute the molecular line emission of massive <span class="hlt">protostellar</span> disks by solving the equation of radiative transfer through the cores and disks produced by the recent radiation-hydrodynamic simulations of Krumholz, Klein, & McKee. We find that in several representative lines the disks show brightness temperatures of hundreds of Kelvin over velocity channels {approx} 10 km s{sup -1} wide, extending over regions hundreds of AU in size. We process the computed intensities to model the performance of next-generation radio and submillimeter telescopes. Our calculations show that observations using facilities such as the EVLA and ALMA should be able to detect massive <span class="hlt">protostellar</span> disks and measure their rotation curves, at least in the nearest massive star-forming regions. They should also detect significant sub-structure and non-axisymmetry in the disks, and in some cases may be able to detect star-disk velocity offsets of a few km s{sup -1}, both of which are the result of strong gravitational instability in massive disks. We use our simulations to explore the strengths and weaknesses of different observational techniques, and we also discuss how observations of massive <span class="hlt">protostellar</span> disks may be used to distinguish between alternative models of massive star formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IAUS..292...40C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IAUS..292...40C"><span id="translatedtitle">Deuterium Fractionation and Ionization Degree in Massive <span class="hlt">Protostellar</span>/cluster Cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Huei-Ru; Liu, Sheng-Yuan; Su, Yu-Nung</p> <p>2013-03-01</p> <p>We have conducted a survey of deuterium fractionation of N2H+, RD (N2H+) ≡ N(N2D+)/N(N2H+), with the Arizona Radio Observatory (ARO) Submillimeter Telescope (SMT) to assess the use of RD (N2H+) as an evolutionary tracer among massive <span class="hlt">protostellar</span>/cluster cores in early stages. Our sample includes 32 dense cores in various evolutionary stages, from high-mass starless cores (HMSCs), high-mass <span class="hlt">protostellar</span> objects (HMPOs), to ultra-compact (UC) HII regions, in infrared dark clouds (IRDCs) and high infrared extinction clouds. The results show a decreasing trend in deuterium fractionation with evolutionary stage traced by gas temperature and line width (Fig. 1). A moderate increasing trend of deuterium fractionation with the CO depletion factor is also found among cores in IRDCs and HMSCs. These suggest a general chemical behavior of deuterated species in low- and high-mass <span class="hlt">protostellar</span> candidates. Upper limits to the ionization degree are also estimated to be in the range of 4 × 10-8 - 5 × 10-6.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AJ....143..107W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AJ....143..107W&link_type=ABSTRACT"><span id="translatedtitle">Very <span class="hlt">Low</span> <span class="hlt">Mass</span> Stellar and Substellar Companions to Solar-like Stars from MARVELS. I. A <span class="hlt">Low-mass</span> Ratio Stellar Companion to TYC 4110-01037-1 in a 79 Day Orbit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wisniewski, John P.; Ge, Jian; Crepp, Justin R.; De Lee, Nathan; Eastman, Jason; Esposito, Massimiliano; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; Gonzalez Hernandez, Jonay I.; Lee, Brian L.; Stassun, Keivan G.; Agol, Eric; Allende Prieto, Carlos; Barnes, Rory; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Da Costa, Luiz N.; Porto De Mello, G. F.; Femenía, Bruno; Ferreira, Leticia D.; Gary, Bruce; Hebb, Leslie; Holtzman, Jon; Liu, Jian; Ma, Bo; Mack, Claude E.; Mahadevan, Suvrath; Maia, Marcio A. G.; Nguyen, Duy Cuong; Ogando, Ricardo L. C.; Oravetz, Daniel J.; Paegert, Martin; Pan, Kaike; Pepper, Joshua; Rebolo, Rafael; Santiago, Basilio; Schneider, Donald P.; Shelden, Alaina C.; Simmons, Audrey; Tofflemire, Benjamin M.; Wan, Xiaoke; Wang, Ji; Zhao, Bo</p> <p>2012-05-01</p> <p>TYC 4110-01037-1 has a <span class="hlt">low-mass</span> stellar companion, whose small mass ratio and short orbital period are atypical among binary <span class="hlt">systems</span> with solar-like (T eff <~ 6000 K) primary stars. Our analysis of TYC 4110-01037-1 reveals it to be a moderately aged (lsim5 Gyr) solar-like star having a mass of 1.07 ± 0.08 M ⊙ and radius of 0.99 ± 0.18 R ⊙. We analyze 32 radial velocity (RV) measurements from the SDSS-III MARVELS survey as well as 6 supporting RV measurements from the SARG spectrograph on the 3.6 m Telescopio Nazionale Galileo telescope obtained over a period of ~2 years. The best Keplerian orbital fit parameters were found to have a period of 78.994 ± 0.012 days, an eccentricity of 0.1095 ± 0.0023, and a semi-amplitude of 4199 ± 11 m s-1. We determine the minimum companion mass (if sin i = 1) to be 97.7 ± 5.8 M Jup. The <span class="hlt">system</span>'s companion to host star mass ratio, >=0.087 ± 0.003, places it at the lowest end of observed values for short period stellar companions to solar-like (T eff <~ 6000 K) stars. One possible way to create such a <span class="hlt">system</span> would be if a triple-component stellar multiple broke up into a short period, low q binary during the cluster dispersal phase of its lifetime. A candidate tertiary body has been identified in the <span class="hlt">system</span> via single-epoch, high contrast imagery. If this object is confirmed to be comoving, we estimate it would be a dM4 star. We present these results in the context of our larger-scale effort to constrain the statistics of <span class="hlt">low-mass</span> stellar and brown dwarf companions to FGK-type stars via the MARVELS survey.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AAS...22110705S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AAS...22110705S"><span id="translatedtitle">The Effect of Feedback and Reionization on Star Formation in <span class="hlt">Low-mass</span> Dwarf Galaxy Halos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simpson, Christine M.; Bryan, G.; Johnston, K. V.; Smith, B. D.; Mac Low, M.; Sharma, S.; Tumlinson, J.</p> <p>2013-01-01</p> <p>I will present a set of high resolution simulations of a 109 M⊙ dark matter halo in a cosmological setting done with an adaptive-mesh refinement code as a mass analogue to local low-luminosity dwarf spheroidal galaxies. The primary goal of our simulations is to investigate the roles of reionization and supernova feedback in determining the star formation histories of <span class="hlt">low</span> <span class="hlt">mass</span> dwarf galaxies. We include a wide range of physical effects, including metal cooling, molecular hydrogen formation and cooling, photoionization and photodissociation from a metagalactic (but not local) background, a simple prescription for self-shielding, star formation, and a simple model for supernova driven energetic feedback. We find that reionization is primarily responsible for expelling most of the gas in our simulations, but that supernova feedback is required to disperse the dense, cold gas in the core of the halo. Moreover, we show that the timing of reionization can produce an order of magnitude difference in the final stellar mass of the <span class="hlt">system</span>. For our full physics run with reionization at z=9, we find a stellar mass of about 105 M⊙ at z=0, and a mass-to-light ratio within the half-light radius of approximately 130 M⊙/L⊙, consistent with observed low-luminosity dwarfs. However, the resulting median stellar metallicity is 0.06 Z⊙, considerably larger than observed <span class="hlt">systems</span>. In addition, we find star formation is truncated between redshifts 4 and 7, at odds with the observed late time star formation in isolated dwarf <span class="hlt">systems</span> but in agreement with Milky Way ultrafaint dwarf spheroidals. We investigate the efficacy of energetic feedback in our simple thermal-energy driven feedback scheme, and suggest that it may still suffer from excessive radiative losses, despite reaching stellar particle masses of about 100 M⊙, and a comoving spatial resolution of 11 pc. This has led us to pursue improvements in our supernova feedback model to include kinetic as well as thermal energy in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010MNRAS.401.1141C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010MNRAS.401.1141C&link_type=ABSTRACT"><span id="translatedtitle">NSVS 06507557: a <span class="hlt">low-mass</span> double-lined eclipsing binary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Çakırlı, Ö.; Ibanoǧlu, C.</p> <p>2010-01-01</p> <p>In this paper, we present the results of a detailed spectroscopic and photometric analysis of the V = 13.4 mag <span class="hlt">low-mass</span> eclipsing binary NSVS 06507557 with an orbital period of 0.515d. We have obtained a series of mid-resolution spectra covering nearly the entire orbit of the <span class="hlt">system</span>. In addition, we have obtained simultaneous VRI broad-band photometry using a small aperture telescope. From these spectroscopic and photometric data, we have derived the <span class="hlt">system</span>'s orbital parameters and we have determined the fundamental stellar parameters of the two components. Our results indicate that NSVS 06507557 consists of a K9 pre-main-sequence star and an M3 pre-main-sequence star. These have masses of 0.66 +/- 0.09 Msolar and 0.28 +/- 0.05 Msolar and radii of 0.60 +/- 0.03 and 0.44 +/- 0.02 Rsolar, respectively, and are located at a distance of 111 +/- 9 pc. The radius of the less massive secondary component is larger than that of a zero-age main-sequence (ZAMS) star having the same mass. While the radius of the primary component is in agreement with ZAMS, the secondary component appears to be larger by about 35 per cent with respect to its ZAMS counterpart. Night-to-night intrinsic light variations up to 0.2 mag have been observed. In addition, the Hα and Hβ lines and the forbidden line of [OI] are seen in emission. The LiI 6708 Å absorption line is seen in most of the spectra. These features are taken to be signs of the characteristics of classic T Tauri stars. The parameters we have derived are consistent with an age of about 20 Myr, according to stellar evolutionary models. The spectroscopic and photometric results are in agreement with those obtained using theoretical predictions. Based on spectroscopic observations collected at TÜBİTAK (Turkey). E-mail: omur.cakirli@ege.edu.tr</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.......137D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......137D"><span id="translatedtitle">Direct measurements of the fundamental properties of <span class="hlt">low-mass</span> stars and brown dwarfs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dupuy, Trent J.</p> <p>2010-10-01</p> <p> [approximate]2 at a given mass, which means that model-based substellar mass determinations (e.g., for directly imaged extrasolar planets and the <span class="hlt">low-mass</span> initial mass function) may be systematically overestimating the masses. (3) We have employed our large sample of binary orbits to carry out a novel test of the earliest evolutionary stages, by using the distribution of orbital eccentricities to distinguish between competing models of brown dwarf formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhDT.........2H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT.........2H"><span id="translatedtitle">Photometric monitoring of open clusters: <span class="hlt">Low-mass</span> eclipsing binary stars and the stellar mass-luminosity-radius relation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hebb, Leslie</p> <p>2006-06-01</p> <p>This thesis describes a photometric monitoring survey of Galactic star clusters designed to detect <span class="hlt">low-mass</span> eclipsing binary star <span class="hlt">systems</span> through variations in their relative lightcurves. The aim is to use cluster eclipsing binaries to measure the masses and radii of M-dwarf stars with ages and metallicities known from studies of brighter cluster stars. This information will provide an improved calibration of the mass-luminosity-radius relation for <span class="hlt">low-mass</span> stars, be used to test stellar structure and evolution models, and help quantify the contribution of <span class="hlt">low-mass</span> stars to the global mass census in the Galaxy. The survey is designed to detect eclipse events in stars of ~0.3 M_sun and consists of 600 Gbytes of raw imaging data on six open clusters with a range of ages (~ 0.15 - 4 Gyr) and metallicites (~ -0.2 - 0.0 dex). The clusters NGC 1647 and M 35 contain excellent candidate <span class="hlt">systems</span> showing eclipse like variations in brightness and photometry consistent with cluster membership. The analysis of these clusters and the eclipsing M-dwarf stars detected in them are presented. Analysis of the candidate <span class="hlt">system</span> in NGC 1647 confirms the object as a newly discovered M-dwarf eclipsing binary in the cluster with compenent masses of M 1 = 0.47 ± 0.05[Special characters omitted.] and M 2 = 0.19 ± 0.02[Special characters omitted.] . The small mass ratio ( M 2 / M 1 ) and low secondary mass of this object provide an unprecedented opportunity to test stellar models. We find that no stellar evolution models are consistent with all the properties of both M-dwarf stars in the eclipsing binary. The candidate in M 35 has been confirmed as an M-dwarf eclipsing binary, and the masses of the individual components are estimated to be M 1 ~ 0.25 M_sun and M 2 ~ 0.15 M_sun . Additional high resolution spectroscopic and photometric observations, for which we have applied and been awarded time, are necessary to accurately derive the intrinsic properties of the individual stellar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880012554&hterms=Fermi+Enrico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3D%2528Fermi%252C%2BEnrico%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880012554&hterms=Fermi+Enrico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3D%2528Fermi%252C%2BEnrico%2529"><span id="translatedtitle">The origin of <span class="hlt">low</span> <span class="hlt">mass</span> particles within and beyond the dust coma envelopes of Comet Halley</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simpson, J. A.; Rabinowitz, D.; Tuzzolino, A. J.; Ksanfomality, L. V.; Sagdeev, R. Z.</p> <p>1987-01-01</p> <p>Measurements from the Dust Counter and Mass Analyzer (DUCMA) instruments on VEGA-1 and -2 revealed unexpected fluxes of <span class="hlt">low</span> <span class="hlt">mass</span> (up to 10 to the minus 13th power g) dust particles at very great distances from the nucleus (300,000 to 600,000 km). These particles are detected in clusters (10 sec duration), preceded and followed by relatively long time intervals during which no dust is detected. This cluster phenomenon also occurs inside the envelope boundaries. Clusters of <span class="hlt">low</span> <span class="hlt">mass</span> particles are intermixed with the overall dust distribution throughout the coma. The clusters account for many of the short-term small-scale intensity enhancements previously ascribed to microjets in the coma. The origin of these clusters appears to be emission from the nucleus of large conglomerates which disintegrate in the coma to yield clusters of discrete, small particles continuing outward to the distant coma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChA%26A..40..220C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChA%26A..40..220C"><span id="translatedtitle">R-mode Instability of <span class="hlt">Low-mass</span> Bare Strange Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chun-mei, Pi; Shu-hua, Yang</p> <p>2016-04-01</p> <p>The r-mode instability window of <span class="hlt">low-mass</span> strange stars is studied using the modified bag model of strange quark matter and reasonable sets of parameters. The results show that the ultimate spin frequency of strange stars increases with the decreasing stellar mass, and the highest spin frequency (716 Hz) of pulsars observed sofar can be explained by the bare strange stars with a mass lower than about 0.1∼0.2 M⊙, depending on the selected parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7148691','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7148691"><span id="translatedtitle"><span class="hlt">Low-mass</span>, high-rate cylindrical MWPC's for the MEGA experiment</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mischke, R.E.; Armijo, V.; Black, J.K.; Bolton, R.D.; Carius, S.; Cooper, M.D.; Espinoza, C.; Hart, G.W.; Hogan, G.E.; Piilonen, L.E.; Sandoval, J.; Schilling, S.; Sena, J.; Stanislaus, S.; Suazo, G.; Szymanski, J.J.; Whitehouse, D.A.; Wilkinson, C.A. ); Fisk, R.; Koetke, D.D.; Manweiler, R.W. ); Jui, C. )</p> <p>1990-01-01</p> <p>The construction of MWPCs for the MEGA experiment at LAMPF are described. The chambers are cylindrical, <span class="hlt">low</span> <span class="hlt">mass</span> (3 {times} 10{sup {minus}4} radiation lengths), and are designed to operate at high rates (3 {times} 10{sup 4} /mm{sup 2}/s). Several novel construction techniques have been developed and custom electronics have been designed to help achieve the required performance, which corresponds to that needed at high luminosity colliders. 4 refs., 3 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22522384','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22522384"><span id="translatedtitle">THE DYNAMICAL EVOLUTION OF <span class="hlt">LOW-MASS</span> HYDROGEN-BURNING STARS, BROWN DWARFS, AND PLANETARY-MASS OBJECTS FORMED THROUGH DISK FRAGMENTATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li, Yun; Kouwenhoven, M. B. N.; Stamatellos, D.; Goodwin, S. P.</p> <p>2015-06-01</p> <p>Theory and simulations suggest that it is possible to form <span class="hlt">low-mass</span> hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) via disk fragmentation. As disk fragmentation results in the formation of several bodies at comparable distances to the host star, their orbits are generally unstable. Here, we study the dynamical evolution of these objects. We set up the initial conditions based on the outcomes of the smoothed-particle hydrodynamics simulations of Stamatellos and Whitworth, and for comparison we also study the evolution of <span class="hlt">systems</span> resulting from lower-mass fragmenting disks. We refer to these two sets of simulations as set 1 and set 2, respectively. At 10 Myr, approximately half of the host stars have one companion left, and approximately 22% (set 1) to 9.8% (set 2) of the host stars are single. <span class="hlt">Systems</span> with multiple secondaries in relatively stable configurations are common (about 30% and 44%, respectively). The majority of the companions are ejected within 1 Myr with velocities mostly below 5 km s{sup −1}, with some runaway escapers with velocities over 30 km s{sup −1}. Roughly 6% (set 1) and 2% (set 2) of the companions pair up into very <span class="hlt">low-mass</span> binary <span class="hlt">systems</span>, resulting in respective binary fractions of 3.2% and 1.2%. The majority of these pairs escape as very <span class="hlt">low-mass</span> binaries, while others remain bound to the host star in hierarchical configurations (often with retrograde inner orbits). Physical collisions with the host star (0.43 and 0.18 events per host star for set 1 and set 2, respectively) and between companions (0.08 and 0.04 events per host star for set 1 and set 2, respectively) are relatively common and their frequency increases with increasing disk mass. Our study predicts observable properties of very <span class="hlt">low-mass</span> binaries, <span class="hlt">low-mass</span> hierarchical <span class="hlt">systems</span>, the BD desert, and free-floating BDs and PMOs in and near young stellar groupings, which can be used to distinguish between different formation scenarios of very <span class="hlt">low-mass</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AAS...21934514M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AAS...21934514M"><span id="translatedtitle">Candidate Very-<span class="hlt">Low-Mass</span> Companions to Nearby Stars Found in the WISE Survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mennen, Anne; Dutcher, D.; Lepine, S.; Faherty, J.</p> <p>2012-01-01</p> <p>We report the identification in the Wide-Field Survey Explorer (WISE) preliminary release of 36 probable very-<span class="hlt">low-mass</span> companions to nearby stars from the SUPERBLINK proper motion catalogue. We examined all WISE sources within one arcminute of a subset of 156,000 SUPERBLINK stars with proper motions between 0.040 and 0.015 seconds of arc per year, photometric distances within 100 parsecs, and positions at least seven degrees from the galactic plane. Using proper motions calculated by comparing the WISE positions of the sources to those of their counterparts in the 2MASS Catalogue, we identified all WISE sources sharing a common proper motion with the SUPERBLINK star. We eliminated all sources detected in the Palomar Sky Survey blue plates, keeping only those red enough to be <span class="hlt">low-mass</span> or brown dwarf companions. We used WISE and 2MASS colors to select only objects consistent with being M, L, or T dwarfs, leaving only 36 likely companions. Based on their color and assumed distances, we estimate the 36 <span class="hlt">low-mass</span> companions to be either late M or early L dwarfs. Follow-up spectroscopic observations will be required for confirmation and formal spectral classification of the companions. We acknowledge the American Museum of Natural History and the National Science Foundation for their support.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...578A.129J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...578A.129J"><span id="translatedtitle">The coronal temperatures of <span class="hlt">low-mass</span> main-sequence stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnstone, C. P.; Güdel, M.</p> <p>2015-06-01</p> <p>Aims: We study the X-ray emission of <span class="hlt">low-mass</span> main-sequence stars to derive a reliable general scaling law between coronal temperature and the level of X-ray activity. Methods: We collect ROSAT measurements of hardness ratios and X-ray luminosities for a large sample of stars to derive which stellar X-ray emission parameter is most closely correlated with coronal temperature. We calculate average coronal temperatures for a sample of 24 <span class="hlt">low-mass</span> main-sequence stars with measured emission measure distributions (EMDs) collected from the literature. These EMDs are based on high-resolution X-ray spectra measured by XMM-Newton and Chandra. Results: We confirm that there is one universal scaling relation between coronal average temperature and surface X-ray flux, FX, that applies to all <span class="hlt">low-mass</span> main-sequence stars. We find that coronal temperature is related to FX by T̅cor = 0.11 FX0.26, where T̅cor is in MK and FX is in erg s-1 cm-2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22011837','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22011837"><span id="translatedtitle">RADIUS-DEPENDENT ANGULAR MOMENTUM EVOLUTION IN <span class="hlt">LOW-MASS</span> STARS. I</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reiners, Ansgar; Mohanty, Subhanjoy</p> <p>2012-02-10</p> <p>Angular momentum evolution in <span class="hlt">low-mass</span> stars is determined by initial conditions during star formation, stellar structure evolution, and the behavior of stellar magnetic fields. Here we show that the empirical picture of angular momentum evolution arises naturally if rotation is related to magnetic field strength instead of to magnetic flux and formulate a corrected braking law based on this. Angular momentum evolution then becomes a strong function of stellar radius, explaining the main trends observed in open clusters and field stars at a few Gyr: the steep transition in rotation at the boundary to full convection arises primarily from the large change in radius across this boundary and does not require changes in dynamo mode or field topology. Additionally, the data suggest transient core-envelope decoupling among solar-type stars and field saturation at longer periods in very <span class="hlt">low</span> <span class="hlt">mass</span> stars. For solar-type stars, our model is also in good agreement with the empirical Skumanich law. Finally, in further support of the theory, we show that the predicted age at which <span class="hlt">low-mass</span> stars spin down from the saturated to unsaturated field regimes in our model corresponds remarkably well to the observed lifetime of magnetic activity in these stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920052767&hterms=water+environment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwater%2Benvironment%253F','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920052767&hterms=water+environment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwater%2Benvironment%253F"><span id="translatedtitle">Probing the circumstellar environments of very young <span class="hlt">low-mass</span> stars using water masers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Terebey, S.; Vogel, S. N.; Myers, P. C.</p> <p>1992-01-01</p> <p>The VLA is used to search nearby very young <span class="hlt">low-mass</span> stars for water maser emission. The sample consists of 26 low-luminosity IRAS sources embedded in dense molecular cores, a class of sources suspected to be newly forming <span class="hlt">low-mass</span> stars on the order of a few hundred thousand years old. Three sources were detected. High spatial resolution maps show the region of maser emission is generally confined to an area smaller than about 0.5 arcsec near the star, and the velocities of individual components span intervals ranging from 20 to 40 km/s. It is inferred from the fact that the maser velocities are too large to be due to gravitational motions in at least two of the sources that the masers are associated with the winds from the young <span class="hlt">low-mass</span> stars. A comparison of the high spatial resolution maser data to lower-resolution CO data shows no evidence for higher collimation close to the star; the stellar wind cavity appears to have similar collimation at 10 exp 15 cm as at 10 exp 7 to 10 exp 18 cm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22047849','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22047849"><span id="translatedtitle">SDSS J184037.78+642312.3: THE FIRST PULSATING EXTREMELY <span class="hlt">LOW</span> <span class="hlt">MASS</span> WHITE DWARF</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hermes, J. J.; Montgomery, M. H.; Winget, D. E.; Brown, Warren R.; Kenyon, Scott J.; Kilic, Mukremin</p> <p>2012-05-10</p> <p>We report the discovery of the first pulsating extremely <span class="hlt">low</span> <span class="hlt">mass</span> (ELM) white dwarf (WD), SDSS J184037.78+642312.3 (hereafter J1840). This DA (hydrogen-atmosphere) WD is by far the coolest and the lowest-mass pulsating WD, with T{sub eff} = 9100 {+-} 170 K and log g = 6.22 {+-} 0.06, which corresponds to a mass of {approx}0.17 M{sub Sun }. This <span class="hlt">low-mass</span> pulsating WD greatly extends the DAV (or ZZ Ceti) instability strip, effectively bridging the log g gap between WDs and main-sequence stars. We detect high-amplitude variability in J1840 on timescales exceeding 4000 s, with a non-sinusoidal pulse shape. Our observations also suggest that the variability is multi-periodic. The star is in a 4.6 hr binary with another compact object, most likely another WD. Future, more extensive time-series photometry of this ELM WD offers the first opportunity to probe the interior of a <span class="hlt">low-mass</span>, presumably He-core WD using the tools of asteroseismology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...826..148E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...826..148E"><span id="translatedtitle">Gas Loss by Ram Pressure Stripping and Internal Feedback from <span class="hlt">Low-mass</span> Milky Way Satellites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Emerick, Andrew; Mac Low, Mordecai-Mark; Grcevich, Jana; Gatto, Andrea</p> <p>2016-08-01</p> <p>The evolution of dwarf satellites in the Milky Way (MW) is affected by a combination of ram pressure stripping (RPS), tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the MW using three-dimensional, high-resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these <span class="hlt">low-mass</span> galaxies on the expected timescales, shorter than 2 Gyr. We find that supernova feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that RPS is less efficient than expected in the stripping scenarios we consider. Our work suggests that although RPS can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of <span class="hlt">low-mass</span> MW dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored versus cuspy dark matter profiles, reionization, and satellite preprocessing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of <span class="hlt">low-mass</span> MW satellites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21224439','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21224439"><span id="translatedtitle">KOI-126: a triply eclipsing hierarchical triple with two <span class="hlt">low-mass</span> stars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carter, Joshua A; Fabrycky, Daniel C; Ragozzine, Darin; Holman, Matthew J; Quinn, Samuel N; Latham, David W; Buchhave, Lars A; Van Cleve, Jeffrey; Cochran, William D; Cote, Miles T; Endl, Michael; Ford, Eric B; Haas, Michael R; Jenkins, Jon M; Koch, David G; Li, Jie; Lissauer, Jack J; MacQueen, Phillip J; Middour, Christopher K; Orosz, Jerome A; Rowe, Jason F; Steffen, Jason H; Welsh, William F</p> <p>2011-02-01</p> <p>The Kepler spacecraft has been monitoring the light from 150,000 stars in its primary quest to detect transiting exoplanets. Here, we report on the detection of an eclipsing stellar hierarchical triple, identified in the Kepler photometry. KOI-126 [A, (B, C)], is composed of a <span class="hlt">low-mass</span> binary [masses M(B) = 0.2413 ± 0.0030 solar mass (M(⊙)), M(C) = 0.2127 ± 0.0026 M(⊙); radii R(B) = 0.2543 ± 0.0014 solar radius (R(⊙)), R(C) = 0.2318 ± 0.0013 R(⊙); orbital period P(1) = 1.76713 ± 0.00019 days] on an eccentric orbit about a third star (mass M(A) = 1.347 ± 0.032 M(⊙); radius R(A) = 2.0254 ± 0.0098 R(⊙); period of orbit around the <span class="hlt">low-mass</span> binary P(2) = 33.9214 ± 0.0013 days; eccentricity of that orbit e(2) = 0.3043 ± 0.0024). The <span class="hlt">low-mass</span> pair probe the poorly sampled fully convective stellar domain offering a crucial benchmark for theoretical stellar models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...818..155B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...818..155B"><span id="translatedtitle">The ELM Survey. VII. Orbital Properties of <span class="hlt">Low-Mass</span> White Dwarf Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Warren R.; Gianninas, A.; Kilic, Mukremin; Kenyon, Scott J.; Allende Prieto, Carlos</p> <p>2016-02-01</p> <p>We present the discovery of 15 extremely <span class="hlt">low-mass</span> (5\\lt {log}g\\lt 7) white dwarf (WD) candidates, 9 of which are in ultra-compact double-degenerate binaries. Our targeted extremely <span class="hlt">low-mass</span> Survey sample now includes 76 binaries. The sample has a lognormal distribution of orbital periods with a median period of 5.4 hr. The velocity amplitudes imply that the binary companions have a normal distribution of mass with 0.76 M⊙ mean and 0.25 M⊙ dispersion. Thus extremely <span class="hlt">low-mass</span> WDs are found in binaries with a typical mass ratio of 1:4. Statistically speaking, 95% of the WD binaries have a total mass below the Chandrasekhar mass, and thus are not type Ia supernova progenitors. Yet half of the observed binaries will merge in less than 6 Gyr due to gravitational wave radiation; probable outcomes include single massive WDs and stable mass transfer AM CVn binaries. Based on observations obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22139933','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22139933"><span id="translatedtitle">KEPLER STUDIES OF <span class="hlt">LOW-MASS</span> ECLIPSING BINARIES. I. PARAMETERS OF THE LONG-PERIOD BINARY KIC 6131659</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bass, Gideon; Orosz, Jerome A.; Welsh, William F.; Windmiller, Gur; Gregg, Trevor Ames; Fetherolf, Tara; Wade, Richard A.; Quinn, Samuel N.</p> <p>2012-12-20</p> <p>KIC 6131659 is a long-period (17.5 days) eclipsing binary discovered by the Kepler mission. We analyzed six quarters of Kepler data along with supporting ground-based photometric and spectroscopic data to obtain accurate values for the mass and radius of both stars, namely, M{sub 1} = 0.922 {+-} 0.007 M{sub Sun }, R{sub 1} = 0.8800 {+-} 0.0028 R{sub Sun }, and M{sub 2} = 0.685 {+-} 0.005 M{sub Sun }, R{sub 2} = 0.6395 {+-} 0.0061 R{sub Sun }. There is a well-known issue with <span class="hlt">low-mass</span> (M {approx}< 0.8 M{sub Sun }) stars (in cases where the mass and radius measurement uncertainties are smaller than 2% or 3%) where the measured radii are almost always 5% to 15% larger than expected from evolutionary models, i.e., the measured radii are all above the model isochrones in a mass-radius plane. In contrast, the two stars in KIC 6131659 were found to sit on the same theoretical isochrone in the mass-radius plane. Until recently, all of the well-studied eclipsing binaries with <span class="hlt">low-mass</span> stars had periods of less than about three days. The stars in such <span class="hlt">systems</span> may have been inflated by high levels of stellar activity induced by tidal effects in these close binaries. KIC 6131659 shows essentially no evidence of enhanced stellar activity, and our measurements support the hypothesis that the unusual mass-radius relationship observed in most <span class="hlt">low-mass</span> stars is influenced by strong magnetic activity created by the rapid rotation of the stars in tidally locked, short-period <span class="hlt">systems</span>. Finally, using short cadence data, we show that KIC 6131657 has one of the smallest measured non-zero eccentricities of a binary with two main-sequence stars, where ecos {omega} (4.57 {+-} 0.02) Multiplication-Sign 10{sup -5}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...790L...1C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...790L...1C"><span id="translatedtitle">Herschel Finds Evidence for Stellar Wind Particles in a <span class="hlt">Protostellar</span> Envelope: Is This What Happened to the Young Sun?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ceccarelli, C.; Dominik, C.; López-Sepulcre, A.; Kama, M.; Padovani, M.; Caux, E.; Caselli, P.</p> <p>2014-07-01</p> <p>There is evidence that the young Sun emitted a high flux of energetic (>=10 MeV) particles. The collisions of these particles with the material at the inner edge of the Protosolar Nebula disk induced spallation reactions that formed short-lived radionuclei, like 10Be, whose trace is now visible in some meteorites. However, it is poorly known exactly when this happened, and whether and how it affected the solar <span class="hlt">system</span>. Here, we present indirect evidence for an ejection of energetic particles in the young protostar, OMC-2 FIR 4, similar to that experienced by the young solar <span class="hlt">system</span>. In this case, the energetic particles collide with the material in the <span class="hlt">protostellar</span> envelope, enhancing the abundance of two molecular ions, HCO+ and N2H+, whose presence is detected via Herschel observations. The flux of energetic particles at a distance of 1 AU from the emitting source, estimated from the measured abundance ratio of HCO+ and N2H+, can easily account for the irradiation required by meteoritic observations. These new observations demonstrate that the ejection of >=10 MeV particles is a phenomenon occurring very early in the life of a protostar, before the disappearance of the envelope from which the future star accretes. The whole envelope is affected by the event, which sets constraints on the magnetic field geometry in the source and opens up the possibility that the spallation reactions are not limited to the inner edge of the Protosolar Nebula disk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...733..122D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...733..122D"><span id="translatedtitle">On the Distribution of Orbital Eccentricities for Very <span class="hlt">Low-mass</span> Binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dupuy, Trent J.; Liu, Michael C.</p> <p>2011-06-01</p> <p>We have compiled a sample of 16 orbits for very <span class="hlt">low-mass</span> stellar (<0.1 M sun) and brown dwarf binaries, including updated orbits for HD 130948BC and LP 415-20AB. This sample enables the first comprehensive study of the eccentricity distribution for such objects. We find that very <span class="hlt">low-mass</span> binaries span a broad range of eccentricities from near-circular to highly eccentric (e ≈ 0.8), with a median eccentricity of 0.34. We have examined potential observational biases in this sample, and for visual binaries we show through Monte Carlo simulations that if we choose appropriate selection criteria then all eccentricities are equally represented (lsim 5% difference between input and output eccentricity distributions). The orbits of this sample of very <span class="hlt">low-mass</span> binaries show some significant differences from their solar-type counterparts. They lack a correlation between orbital period and eccentricity, and display a much higher fraction of near-circular orbits (e < 0.1) than solar-type stars, which together may suggest a different formation mechanism or dynamical history for these two populations. Very <span class="hlt">low-mass</span> binaries also do not follow the e 2 distribution of Ambartsumian, which would be expected if their orbits were distributed in phase space according to a function of energy alone (e.g., the Boltzmann distribution). We find that current numerical simulations of very <span class="hlt">low-mass</span> star formation do not completely reproduce the observed properties of our binary sample. The cluster formation model of Bate agrees very well with the overall e distribution, but the lack of any high-e (>0.6) binaries at orbital periods comparable to our sample suggests that tidal damping due to gas disks may play too large of a role in the simulations. In contrast, the circumstellar disk fragmentation model of Stamatellos & Whitworth predicts only high-e binaries and thus is highly inconsistent with our sample. These discrepancies could be explained if multiple formation processes are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015adap.prop..101K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015adap.prop..101K"><span id="translatedtitle">Hazardous Early Days In (and Beyond) the Habitable Zones Around Ultra-<span class="hlt">Low-Mass</span> Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kastner, Joel</p> <p></p> <p>Although a majority of stars in the solar neighborhood are of mid- to late-M type, the magnetically-induced coronal (X-ray) and chromospheric (UV, H-alpha) activity of such stars remain essentially unexplored for the important age range 10-100 Myr. Such information on high-energy processes associated with young M stars would provide much-needed constraints on models of the effects of stellar irradiation on the physics and chemistry of planet-forming disks and newborn planets. In addition, X-ray and UV observations of ultra-<span class="hlt">low-mass</span> young stars can serve to probe the (presently ill-defined) spectral type boundary that determines which very <span class="hlt">low-mass</span> objects will eventually become M stars -- as opposed to brown dwarfs (BDs) -- following their pre-main sequence evolutionary stages. Via ADAP support, we have developed the GALEX Nearby Young Star Search (GALNYSS), a search method that combines GALEX, 2MASS, WISE and proper motion catalog information to identify nearby, young, lowmass stars. We have applied this method to identify ~2000 candidate young (10-100 Myr), <span class="hlt">low-mass</span> (M-type) stars within 150 pc. These GALNYSS-identified young star candidates are distributed over the entire GALEX-covered sky, and their spectral types peak in the M3-4 range; followup optical spectroscopic work is ongoing (Rodriguez et al. 2013, ApJ, 774, 101). We now propose an ADA program to determine the X-ray properties of representative stars among these GALNYSS candidates, so as to confirm their youth and investigate the early evolution of coronal activity near the <span class="hlt">low-mass</span> star/BD boundary and the effects of such activity on planet formation. Specifically, we will exploit the presence in the HEASARC archives of XMM-Newton and (to a lesser extent) Chandra X-ray Observatory data for a few dozen GALNYSS candidates that have been observed serendipitously by one or both of these space observatories. The proposed ADA program will yield the full reduction and analysis of these as-yet unexplored data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21576713','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21576713"><span id="translatedtitle">ON THE DISTRIBUTION OF ORBITAL ECCENTRICITIES FOR VERY <span class="hlt">LOW-MASS</span> BINARIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dupuy, Trent J.; Liu, Michael C.</p> <p>2011-06-01</p> <p>We have compiled a sample of 16 orbits for very <span class="hlt">low-mass</span> stellar (<0.1 M{sub sun}) and brown dwarf binaries, including updated orbits for HD 130948BC and LP 415-20AB. This sample enables the first comprehensive study of the eccentricity distribution for such objects. We find that very <span class="hlt">low-mass</span> binaries span a broad range of eccentricities from near-circular to highly eccentric (e {approx} 0.8), with a median eccentricity of 0.34. We have examined potential observational biases in this sample, and for visual binaries we show through Monte Carlo simulations that if we choose appropriate selection criteria then all eccentricities are equally represented ({approx}< 5% difference between input and output eccentricity distributions). The orbits of this sample of very <span class="hlt">low-mass</span> binaries show some significant differences from their solar-type counterparts. They lack a correlation between orbital period and eccentricity, and display a much higher fraction of near-circular orbits (e < 0.1) than solar-type stars, which together may suggest a different formation mechanism or dynamical history for these two populations. Very <span class="hlt">low-mass</span> binaries also do not follow the e{sup 2} distribution of Ambartsumian, which would be expected if their orbits were distributed in phase space according to a function of energy alone (e.g., the Boltzmann distribution). We find that current numerical simulations of very <span class="hlt">low-mass</span> star formation do not completely reproduce the observed properties of our binary sample. The cluster formation model of Bate agrees very well with the overall e distribution, but the lack of any high-e (>0.6) binaries at orbital periods comparable to our sample suggests that tidal damping due to gas disks may play too large of a role in the simulations. In contrast, the circumstellar disk fragmentation model of Stamatellos and Whitworth predicts only high-e binaries and thus is highly inconsistent with our sample. These discrepancies could be explained if multiple formation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...783L..17Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...783L..17Z"><span id="translatedtitle">Accretion onto Planetary Mass Companions of <span class="hlt">Low-mass</span> Young Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Yifan; Herczeg, Gregory J.; Kraus, Adam L.; Metchev, Stanimir; Cruz, Kelle L.</p> <p>2014-03-01</p> <p>Measurements of accretion rates onto planetary mass objects may distinguish between different planet formation mechanisms, which predict different accretion histories. In this Letter, we use Hubble Space Telescope (HST)/WFC3 UVIS optical photometry to measure accretion rates onto three accreting objects, GSC 06214-00210 b, GQ Lup b, and DH Tau b, that are at the planet/brown dwarf boundary and are companions to solar mass stars. The excess optical emission in the excess accretion continuum yields mass accretion rates of 10-9-10-11 M ⊙ yr-1 for these three objects. Their accretion rates are an order of magnitude higher than expected from the correlation between mass and accretion rates measured from the UV excess, which is applicable if these wide planetary mass companions formed by <span class="hlt">protostellar</span> core fragmentation. The high accretion rates and large separation from the central star demonstrate the presence of massive disks around these objects. Models for the formation and evolution of wide planetary mass companions should account for their large accretion rates. High ratios of Hα luminosity over accretion luminosity for objects with low accretion rates suggest that searches for Hα emission may be an efficient way to find accreting planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EAS....75..219I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EAS....75..219I"><span id="translatedtitle"><span class="hlt">Low-Mass</span> Star Formation: From Molecular Cloud Cores to Protostars and Protoplanetary Disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inutsuka, S.-I.; Machida, M.; Matsumoto, T.; Tsukamoto, Y.; Iwasaki, K.</p> <p>2016-05-01</p> <p>This review describes realistic evolution of magnetic field and rotation of the protostars, dynamics of outflows and jets, and the formation and evolution of protoplanetary disks. Recent advances in the <span class="hlt">protostellar</span> collapse simulations cover a huge dynamic range from molecular cloud core density to stellar density in a self-consistent manner and account for all the non-ideal magnetohydrodynamical effects, such as Ohmic resistivity, ambipolar diffusion, and Hall current. We explain the emergence of the first core, i.e., the quasi-hydrostatic object that consists of molecular gas, and the second core, i.e., the protostar. Ohmic dissipation largely removes the magnetic flux from the center of a collapsing cloud core. A fast well-collimated bipolar jet along the rotation axis of the protostar is driven after the magnetic field is re-coupled with warm gas (˜103 K) around the protostar. The circumstellar disk is born in the "dead zone", a region that is de-coupled from the magnetic field, and the outer radius of the disk increases with that of the dead zone during the early accretion phase. The rapid increase of the disk size occurs after the depletion of the envelope of molecular cloud core. The effect of Hall current may create two distinct populations of protoplanetary disks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22363946','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22363946"><span id="translatedtitle">ACCRETION ONTO PLANETARY MASS COMPANIONS OF <span class="hlt">LOW-MASS</span> YOUNG STARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhou, Yifan; Herczeg, Gregory J.; Kraus, Adam L.; Metchev, Stanimir; Cruz, Kelle L. E-mail: zhouyifan1012@gmail.com</p> <p>2014-03-01</p> <p>Measurements of accretion rates onto planetary mass objects may distinguish between different planet formation mechanisms, which predict different accretion histories. In this Letter, we use Hubble Space Telescope (HST)/WFC3 UVIS optical photometry to measure accretion rates onto three accreting objects, GSC 06214–00210 b, GQ Lup b, and DH Tau b, that are at the planet/brown dwarf boundary and are companions to solar mass stars. The excess optical emission in the excess accretion continuum yields mass accretion rates of 10{sup –9}-10{sup –11} M {sub ☉} yr{sup –1} for these three objects. Their accretion rates are an order of magnitude higher than expected from the correlation between mass and accretion rates measured from the UV excess, which is applicable if these wide planetary mass companions formed by <span class="hlt">protostellar</span> core fragmentation. The high accretion rates and large separation from the central star demonstrate the presence of massive disks around these objects. Models for the formation and evolution of wide planetary mass companions should account for their large accretion rates. High ratios of Hα luminosity over accretion luminosity for objects with low accretion rates suggest that searches for Hα emission may be an efficient way to find accreting planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21394263','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21394263"><span id="translatedtitle">HIGH-RESOLUTION OBSERVATIONS OF DUST CONTINUUM EMISSION AT 340 GHz FROM THE <span class="hlt">LOW-MASS</span> T TAURI STAR FN TAURI</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Momose, Munetake; Ohashi, Nagayoshi; Kudo, Tomoyuki; Tamura, Motohide; Kitamura, Yoshimi</p> <p>2010-03-20</p> <p>FN Tau is a rare example of a very <span class="hlt">low-mass</span> T Tauri star that exhibits a spatially resolved nebulosity in near-infrared scattering light. To directly derive the parameters of a circumstellar disk around FN Tau, observations of dust continuum emission at 340 GHz are carried out with the Submillimeter Array (SMA). A point-like dust continuum emission was detected with a synthesized beam of {approx}0.''7 in FWHM. From the analysis of the visibility plot, the radius of the emission is estimated to be <=0.''29, corresponding to 41 AU. This is much smaller than the radius of the nebulosity, 1.''85 for its brighter part at 1.6 {mu}m. The 340 GHz continuum emission observed with the SMA and the photometric data at lambda <= 70 {mu}m are explained by a power-law disk model whose outer radius and mass are 41 AU and (0.24-5.9) x 10{sup -3} M{sub sun}, respectively, if the exponent of dust mass opacity (beta) is assumed to be 0-2. The disk model cannot fully reproduce the flux density at 230 GHz obtained with the IRAM 30 m telescope, suggesting that there is another extended 'halo' component that is missed in the SMA observations. By requiring the halo not to be detected with the SMA, the lower limit to the size of the halo is evaluated to be between 174 AU and 574 AU, depending on the assumed beta value. This size is comparable to the near-infrared nebulosity, implying that the halo unseen with the SMA corresponds to the origin of the near-infrared nebulosity. The halo can contain mass comparable to or at most 8 times greater than that of the inner power-law disk, but its surface density should be lower than that at the outer edge of the power-law disk by more than 1 order of magnitude. The physical nature of the halo is unclear, but it may be the periphery of a flared circumstellar disk that is not described well in terms of a power-law disk model, or a remnant of a <span class="hlt">protostellar</span> envelope having flattened structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MNRAS.433.2226R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MNRAS.433.2226R"><span id="translatedtitle">HST/WFC3 imaging of <span class="hlt">protostellar</span> jets in Carina: [Fe II] emission tracing massive jets from intermediate-mass protostars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reiter, Megan; Smith, Nathan</p> <p>2013-08-01</p> <p>We present narrow-band Wide Field Camera 3 (WFC3)-UVIS and WFC3-IR images of four externally irradiated <span class="hlt">protostellar</span> jets in the Carina nebula: HH 666, HH 901, HH 902 and HH 1066. These massive jets are unusual because they are bathed in UV radiation from dozens of nearby O-type stars, but despite the strong incident ionizing radiation, portions of the jet remain neutral. Near-IR [Fe II] images reveal dense, neutral gas that was not seen in previous studies of Hα emission. We show that near-IR [Fe II] emitting gas must be self-shielded from Lyman continuum photons, regardless of its excitation mechanism (shocks, far-ultraviolet radiation or both). High densities are required for the survival of Fe+ amid the strong Lyman continuum luminosity from Tr14, raising estimates of the mass-loss rates by an order of magnitude. Higher jet mass-loss rates require higher accretion rates on to their driving protostars, implying that these jets are driven by intermediate-mass (˜2-8 M⊙) stars. Indeed, the IR driving sources of two of these outflows have luminosities that require intermediate-mass protostars (the other two are so deeply embedded that their luminosity is uncertain). All four of these HH jets are highly collimated, with opening angles of only a few degrees, similar to those observed in <span class="hlt">low-mass</span> protostars. We propose that these jets reflect essentially the same outflow phenomenon seen in wide-angle molecular outflows associated with intermediate- and high-mass protostars, but that the collimated atomic jet core is irradiated and rendered observable in the harsh radiative environment of the Carina nebula. In more quiescent environments, this atomic core remains invisible, and outflows traced by shock-excited molecules in the outflow cavity give the impression that these outflows have a wider opening angle. Thus, the externally irradiated jets in Carina constitute a new view of collimated jets from intermediate-mass protostars and offer strong additional evidence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApJ...779..183F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApJ...779..183F"><span id="translatedtitle">Magnetic Inhibition of Convection and the Fundamental Properties of <span class="hlt">Low-mass</span> Stars. I. Stars with a Radiative Core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feiden, Gregory A.; Chaboyer, Brian</p> <p>2013-12-01</p> <p>Magnetic fields are hypothesized to inflate the radii of <span class="hlt">low-mass</span> stars—defined as less massive than 0.8 M ⊙—in detached eclipsing binaries (DEBs). We investigate this hypothesis using the recently introduced magnetic Dartmouth stellar evolution code. In particular, we focus on stars thought to have a radiative core and convective outer envelope by studying in detail three individual DEBs: UV Psc, YY Gem, and CU Cnc. Our results suggest that the stabilization of thermal convection by a magnetic field is a plausible explanation for the observed model-radius discrepancies. However, surface magnetic field strengths required by the models are significantly stronger than those estimated from observed coronal X-ray emission. Agreement between model predicted surface magnetic field strengths and those inferred from X-ray observations can be found by assuming that the magnetic field sources its energy from convection. This approach makes the transport of heat by convection less efficient and is akin to reduced convective mixing length methods used in other studies. Predictions for the metallicity and magnetic field strengths of the aforementioned <span class="hlt">systems</span> are reported. We also develop an expression relating a reduction in the convective mixing length to a magnetic field strength in units of the equipartition value. Our results are compared with those from previous investigations to incorporate magnetic fields to explain the <span class="hlt">low-mass</span> DEB radius inflation. Finally, we explore how the effects of magnetic fields might affect mass determinations using asteroseismic data and the implication of magnetic fields on exoplanet studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014yCat.5144....0M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014yCat.5144....0M"><span id="translatedtitle">VizieR Online Data Catalog: Near-IR spectroscopy of <span class="hlt">low-mass</span> binaries and brown dwarfs (Mace, 2014)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mace, G. N.</p> <p>2014-05-01</p> <p>The mass of a star at formation determines its subsequent evolution and demise. <span class="hlt">Low-mass</span> stars are the most common products of star formation and their long main-sequence lifetimes cause them to accumulate over time. Star formation also produces many substellar-mass objects known as brown dwarfs, which emerge from their natal molecular clouds and continually cool as they age, pervading the Milky Way. <span class="hlt">Low-mass</span> stars and brown dwarfs exhibit a wide range of physical characteristics and their abundance make them ideal subjects for testing formation and evolution models. I have examined a pair of pre-main sequence spectroscopic binaries and used radial velocity variations to determine orbital solutions and mass ratios. Additionally, I have employed synthetic spectra to estimate their effective temperatures and place them on theoretical Hertzsprung-Russell diagrams. From this analysis I discuss the formation and evolution of young binary <span class="hlt">systems</span> and place bounds on absolute masses and radii. I have also studied the late-type T dwarfs revealed by the Wide-field Infrared Survey Explorer (WISE). This includes the exemplar T8 subdwarf Wolf 1130C, which has the lowest inferred metallicity in the literature and spectroscopic traits consistent with old age. Comparison to synthetic spectra implies that the dispersion in near-infrared colors of late-type T dwarfs is a result of age and/or thin sul de clouds. With the updated census of the L, T, and Y dwarfs we can now study specific brown dwarf subpopulations. Finally, I present a number of future studies that would develop our understanding of the physical qualities of T dwarf color outliers and disentangle the tracers of age and atmospheric properties. The thesis is available at: http://www.astro.ucla.edu/~gmace/thesis.html (7 data files).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22348397','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22348397"><span id="translatedtitle">Magnetic inhibition of convection and the fundamental properties of <span class="hlt">low-mass</span> stars. I. Stars with a radiative core</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Feiden, Gregory A.; Chaboyer, Brian E-mail: brian.chaboyer@dartmouth.edu</p> <p>2013-12-20</p> <p>Magnetic fields are hypothesized to inflate the radii of <span class="hlt">low-mass</span> stars—defined as less massive than 0.8 M {sub ☉}—in detached eclipsing binaries (DEBs). We investigate this hypothesis using the recently introduced magnetic Dartmouth stellar evolution code. In particular, we focus on stars thought to have a radiative core and convective outer envelope by studying in detail three individual DEBs: UV Psc, YY Gem, and CU Cnc. Our results suggest that the stabilization of thermal convection by a magnetic field is a plausible explanation for the observed model-radius discrepancies. However, surface magnetic field strengths required by the models are significantly stronger than those estimated from observed coronal X-ray emission. Agreement between model predicted surface magnetic field strengths and those inferred from X-ray observations can be found by assuming that the magnetic field sources its energy from convection. This approach makes the transport of heat by convection less efficient and is akin to reduced convective mixing length methods used in other studies. Predictions for the metallicity and magnetic field strengths of the aforementioned <span class="hlt">systems</span> are reported. We also develop an expression relating a reduction in the convective mixing length to a magnetic field strength in units of the equipartition value. Our results are compared with those from previous investigations to incorporate magnetic fields to explain the <span class="hlt">low-mass</span> DEB radius inflation. Finally, we explore how the effects of magnetic fields might affect mass determinations using asteroseismic data and the implication of magnetic fields on exoplanet studies.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.446..510K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.446..510K"><span id="translatedtitle">Photometry and Hα studies of a <span class="hlt">low-mass</span>-ratio overcontact binary ASAS J082243+1927.0</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kandulapati, S.; Devarapalli, S. P.; Pasagada, V. R.</p> <p>2015-01-01</p> <p>Both high-precision CCD photometric and Hα line studies are presented for an overcontact binary ASAS J082243+1927.0. The light curve exhibits a total eclipse at secondary minima along with an O'Connell effect. The light curve was modelled using the Wilson-Devinney code and the best solution provides the mass ratio q ˜ 0.106 and fill-out factor f ˜ 72 per cent. These parameters indicate that the <span class="hlt">system</span> is a <span class="hlt">low-mass</span>-ratio overcontact binary with a high degree of geometrical contact. The Hα line equivalent width varied at different phases and it is found that the line is possibly filled in at secondary minima. From a small sample of overcontact binaries, we found a correlation between the orbital period and Hα line equivalent width of the primary component. Based on a sample of high filling factor and <span class="hlt">low-mass</span>-ratio contact binaries, a mass ratio cut-off is observed at qcritical = 0.085 in the mass-ratio-period plane. It was observed that for qcritical < 0.085, the period decreases with an increase of q, and above it the period increases as the mass ratio increases. Interestingly, the observed mass ratio cut-off value lies close to the critical mass ratio range as predicted in the literature. The observational evidence of the cut-off of the mass ratio and its variation with orbital period are discussed in terms of mass transfer and angular momentum loss. Based on the results, we suggest that, ASAS J082243+1927.0 is at the verge of merger, eventually forming a fast rotating star.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ApJ...713.1143Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ApJ...713.1143Z"><span id="translatedtitle">Long-term Evolution of <span class="hlt">Protostellar</span> and Protoplanetary Disks. II. Layered Accretion with Infall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Zhaohuan; Hartmann, Lee; Gammie, Charles</p> <p>2010-04-01</p> <p>We use one-dimensional two-zone time-dependent accretion disk models to study the long-term evolution of <span class="hlt">protostellar</span> disks subject to mass addition from the collapse of a rotating cloud core. Our model consists of a constant surface density magnetically coupled active layer, with transport and dissipation in inactive regions only via gravitational instability. We start our simulations after a central protostar has formed, containing ~10% of the mass of the <span class="hlt">protostellar</span> cloud. Subsequent evolution depends on the angular momentum of the accreting envelope. We find that disk accretion matches the infall rate early in the disk evolution because much of the inner disk is hot enough to couple to the magnetic field. Later infall reaches the disk beyond ~10 AU, and the disk undergoes outbursts of accretion in FU Ori-like events as described by Zhu et al. If the initial cloud core is moderately rotating, most of the central star's mass is built up by these outburst events. Our results suggest that the <span class="hlt">protostellar</span> "luminosity problem" is eased by accretion during these FU Ori-like outbursts. After infall stops, the disk enters the T Tauri phase. An outer, viscously evolving disk has a structure that is in reasonable agreement with recent submillimeter studies and its surface density evolves from Σ vprop R -1 to R -1.5. An inner, massive belt of material—the "dead zone"—would not have been observed yet but should be seen in future high angular resolution observations by EVLA and ALMA. This high surface density belt is a generic consequence of low angular momentum transport efficiency at radii where the disk is magnetically decoupled, and would strongly affect planet formation and migration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010069989','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010069989"><span id="translatedtitle">ASCA Observation of MS 1603.6+2600 (=UW Coronae Borealis): A Dipping <span class="hlt">Low-Mass</span> X-ray Binary in the Outer Halo?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mukai, Koji; Smale, Alan; Stahle, Caroline K.; Schlegel, Eric M.; Wijnands, Rudy; White, Nicholas E. (Technical Monitor)</p> <p>2001-01-01</p> <p>MS 1603.6+2600 is a high-latitude X-ray binary with a 111 min orbital period, thought to be either an unusual cataclysmic variable or an unusual <span class="hlt">low-mass</span> X-ray binary. In an ASCA observation in 1997 August, we find a burst whose light curve suggests a Type 1 (thermonuclear flash) origin. We also find an orbital X-ray modulation in MS 1603.6+2600, which is likely to be periodic dips, presumably due to azimuthal structure in the accretion disk. Both are consistent with this <span class="hlt">system</span> being a normal <span class="hlt">low-mass</span> X-ray binary harboring a neutron star, but at a great distance. We tentatively suggest that MS 1603.6+2600 is located in the outer halo of the Milky Way, perhaps associated with the globular cluster Palomar 14, 11 deg away from MS 1603.6+2600 on the sky at an estimated distance of 73.8 kpc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...594A..58O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...594A..58O"><span id="translatedtitle">The segregation of starless and <span class="hlt">protostellar</span> clumps in the Hi-GAL ℓ = 224° region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olmi, L.; Cunningham, M.; Elia, D.; Jones, P.</p> <p>2016-10-01</p> <p>Context. Stars form in dense, dusty structures, which are embedded in larger clumps of molecular clouds often showing a clear filamentary structure on large scales (≳1 pc). The origin (e.g., turbulence or gravitational instabilities) and evolution of these filaments, as well as their relation to clump and core formation, are not yet fully understood. A large sample of both starless and <span class="hlt">protostellar</span> clumps can now be found in the Herschel Infrared GALactic Plane Survey (Hi-GAL) key project, which also provides striking images of the filamentary structure of the parent molecular clouds. Recent results indicate that populations of clumps on and off filaments may differ. Aims: One of the best-studied regions in the Hi-GAL survey can be observed toward the ℓ = 224° field. Here, a filamentary region has been studied and it has been found that <span class="hlt">protostellar</span> clumps are mostly located along the main filament, whereas starless clumps are detected off this filament and are instead found on secondary, less prominent filaments. We want to investigate this segregation effect and how it may affect the clumps properties. Methods: We mapped the 12CO (1-0) line and its main three isotopologues toward the two most prominent filaments observed toward the ℓ = 224° field using the Mopra radio telescope, in order to set observational constraints on the dynamics of these structures and the associated starless and <span class="hlt">protostellar</span> clumps. Results: Compared to the starless clumps, the <span class="hlt">protostellar</span> clumps are more luminous, more turbulent and lie in regions where the filamentary ambient gas shows larger linewidths. We see evidence of gas flowing along the main filament, but we do not find any signs of accretion flow from the filament onto the Hi-GAL clumps. We analyze the radial column density profile of the filaments and their gravitational stability. Conclusions: The more massive and highly fragmented main filament appears to be thermally supercritical and gravitationally bound</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005A%26A...432..921F&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005A%26A...432..921F&link_type=ABSTRACT"><span id="translatedtitle">Search for massive <span class="hlt">protostellar</span> candidates in the southern hemisphere. I. Association with dense gas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fontani, F.; Beltrán, M. T.; Brand, J.; Cesaroni, R.; Testi, L.; Molinari, S.; Walmsley, C. M.</p> <p>2005-03-01</p> <p>We have observed two rotational transitions of both CS and C17O, and the 1.2 mm continuum emission towards a sample of 130 high-mass <span class="hlt">protostellar</span> candidates with δ < -30°. This work represents the first step of the extension to the southern hemisphere of a project started more than a decade ago aimed at the identification of massive <span class="hlt">protostellar</span> candidates. Following the same approach adopted for sources with δ ≥ -30°, we have selected from the IRAS Point Source Catalogue 429 sources which potentially are compact molecular clouds on the basis of their IR colours. The sample has then been divided into two groups according to the colour indices [25 12] and [60 12]: the 298 sources with [25 12] ≥ 0.57 and [60 12] ≥ 1.30 have been called High sources, the remaining 131 have been called Low sources. In this paper, we check the association with dense gas and dust in 130 Low sources. We have obtained a detection rate of ~85% in CS, demonstrating a tight association of the sources with dense molecular clumps. Among the sources detected in CS, ~76% have also been detected in C17O and ~93% in the 1.2 mm continuum. Millimeter-continuum maps show the presence of clumps with diameters in the range 0.2-2 pc and masses from a few M⊙ to 105 M⊙; H2 volume densities computed from CS line ratios lie between ~104.5 and 105.5 cm-3. The bolometric luminosities of the sources, derived from IRAS data, are in the range 103-106 L⊙, consistent with embedded high-mass objects. Based on our results and those found in the literature for other samples of high-mass young stellar objects, we conclude that our sources are massive objects in a very early evolutionary stage, probably prior to the formation of an Hii region. We propose a scenario in which High and Low sources are both made of a massive clump hosting a high-mass <span class="hlt">protostellar</span> candidate and a nearby stellar cluster. The difference might be due to the fact that the 12 μm IRAS flux, the best discriminant between the two</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.441.2111J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.441.2111J"><span id="translatedtitle">The effect of starspots on the radii of <span class="hlt">low-mass</span> pre-main-sequence stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, R. J.; Jeffries, R. D.</p> <p>2014-07-01</p> <p>A polytropic model is used to investigate the effects of dark photospheric spots on the evolution and radii of magnetically active, <span class="hlt">low-mass</span> (M < 0.5 M⊙), pre-main-sequence (PMS) stars. Spots slow the contraction along Hayashi tracks and inflate the radii of PMS stars by a factor of (1 - β)-N compared to unspotted stars of the same luminosity, where β is the equivalent covering fraction of dark starspots and N ≃ 0.45 ± 0.05. This is a much stronger inflation than predicted by Spruit & Weiss for main-sequence stars with the same β, where N ˜ 0.2-0.3. These models have been compared to radii determined for very magnetically active K- and M-dwarfs in the young Pleiades and NGC 2516 clusters, and the radii of tidally locked, <span class="hlt">low-mass</span> eclipsing binary components. The binary components and zero-age main-sequence K-dwarfs have radii inflated by ˜10 per cent compared to an empirical radius-luminosity relation that is defined by magnetically inactive field dwarfs with interferometrically measured radii; <span class="hlt">low-mass</span> M-type PMS stars, that are still on their Hayashi tracks, are inflated by up to ˜40 per cent. If this were attributable to starspots alone, we estimate that an effective spot coverage of 0.35 < β < 0.51 is required. Alternatively, global inhibition of convective flux transport by dynamo-generated fields may play a role. However, we find greater consistency with the starspot models when comparing the loci of active young stars and inactive field stars in colour-magnitude diagrams, particularly for the highly inflated PMS stars, where the large, uniform temperature reduction required in globally inhibited convection models would cause the stars to be much redder than observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22348392','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22348392"><span id="translatedtitle">The atomic and molecular content of disks around very <span class="hlt">low-mass</span> stars and brown dwarfs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pascucci, I.; Herczeg, G.; Carr, J. S.; Bruderer, S.</p> <p>2013-12-20</p> <p>There is growing observational evidence that disk evolution is stellar-mass-dependent. Here, we show that these dependencies extend to the atomic and molecular content of disk atmospheres. We analyze a unique dataset of high-resolution Spitzer/IRS spectra from eight very <span class="hlt">low</span> <span class="hlt">mass</span> star and brown dwarf disks. We report the first detections of Ne{sup +}, H{sub 2}, CO{sub 2}, and tentative detections of H{sub 2}O toward these faint and <span class="hlt">low-mass</span> disks. Two of our [Ne II] 12.81 μm emission lines likely trace the hot (≥5000 K) disk surface irradiated by X-ray photons from the central stellar/sub-stellar object. The H{sub 2} S(2) and S(1) fluxes are consistent with arising below the fully or partially ionized surface traced by the [Ne II] emission in gas at ∼600 K. We confirm the higher C{sub 2}H{sub 2}/HCN flux and column density ratio in brown dwarf disks previously noted from low-resolution IRS spectra. Our high-resolution spectra also show that the HCN/H{sub 2}O fluxes of brown dwarf disks are on average higher than those of T Tauri disks. Our LTE modeling hints that this difference extends to column density ratios if H{sub 2}O lines trace warm ≥600 K disk gas. These trends suggest that the inner regions of brown dwarf disks have a lower O/C ratio than those of T Tauri disks, which may result from a more efficient formation of non-migrating icy planetesimals. An O/C = 1, as inferred from our analysis, would have profound implications on the bulk composition of rocky planets that can form around very <span class="hlt">low</span> <span class="hlt">mass</span> stars and brown dwarfs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013A%26A...552A.141K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013A%26A...552A.141K"><span id="translatedtitle">Water in star-forming regions with Herschel (WISH). III. Far-infrared cooling lines in <span class="hlt">low-mass</span> young stellar objects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karska, A.; Herczeg, G. J.; van Dishoeck, E. F.; Wampfler, S. F.; Kristensen, L. E.; Goicoechea, J. R.; Visser, R.; Nisini, B.; San José-García, I.; Bruderer, S.; Śniady, P.; Doty, S.; Fedele, D.; Yıldız, U. A.; Benz, A. O.; Bergin, E.; Caselli, P.; Herpin, F.; Hogerheijde, M. R.; Johnstone, D.; Jørgensen, J. K.; Liseau, R.; Tafalla, M.; van der Tak, F.; Wyrowski, F.</p> <p>2013-04-01</p> <p>Context. Understanding the physical phenomena involved in the earlierst stages of <span class="hlt">protostellar</span> evolution requires knowledge of the heating and cooling processes that occur in the surroundings of a young stellar object. Spatially resolved information from its constituent gas and dust provides the necessary constraints to distinguish between different theories of accretion energy dissipation into the envelope. Aims. Our aims are to quantify the far-infrared line emission from <span class="hlt">low-mass</span> protostars and the contribution of different atomic and molecular species to the gas cooling budget, to determine the spatial extent of the emission, and to investigate the underlying excitation conditions. Analysis of the line cooling will help us characterize the evolution of the relevant physical processes as the protostar ages. Methods. Far-infrared Herschel-PACS spectra of 18 <span class="hlt">low-mass</span> protostars of various luminosities and evolutionary stages are studied in the context of the WISH key program. For most targets, the spectra include many wavelength intervals selected to cover specific CO, H2O, OH, and atomic lines. For four targets the spectra span the entire 55-200 μm region. The PACS field-of-view covers ~47" with the resolution of 9.4". Results. Most of the protostars in our sample show strong atomic and molecular far-infrared emission. Water is detected in 17 out of 18 objects (except TMC1A), including 5 Class I sources. The high-excitation H2O 818-707 63.3 μm line (Eu/kB = 1071 K) is detected in 7 sources. CO transitions from J = 14-13 up to J = 49 - 48 are found and show two distinct temperature components on Boltzmann diagrams with rotational temperatures of ~350 K and ~700 K. H2O has typical excitation temperatures of ~150 K. Emission from both Class 0 and I sources is usually spatially extended along the outflow direction but with a pattern that depends on the species and the transition. In the extended sources, emission is stronger off source and extended on &≥10,000 AU</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AAS...22534528G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AAS...22534528G"><span id="translatedtitle">Combining Fits of The Optical Photometry and X-ray Spectra of the <span class="hlt">Low</span> <span class="hlt">Mass</span> X-ray Binary V1408 Aquilae.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gomez, Sebastian; Mason, Paul A.; Robinson, Edward L.</p> <p>2015-01-01</p> <p>V1408 Aquilae is a binary <span class="hlt">system</span> with a black hole primary accreting matter from a <span class="hlt">low</span> <span class="hlt">mass</span> secondary. We observed the <span class="hlt">system</span> at the McDonald Observatory and collected 126 hours of high speed optical photometry on the source. We modeled the optical light curve using the XRbinary light curve synthesis software. The best fits to the optical light curve seem to suggest that the primary is a <span class="hlt">low</span> <span class="hlt">mass</span> black hole, however we cannot exclude some high mass solutions. Our models slightly favor a 3 solar mass primary at an inclination of about 13 degrees. In order to further constrain these parameters, and verify their validity we compared the fits of the optical light curve to fits to the X-ray spectra of the source. Using data from the Chandra Transmission Grating Catalog and Archive and the ISIS software analysis package we modeled the spectra of the source with a multi-temperature blackbody for a relativistic accretion disk around a spinning black hole and an additional photon power law component. The fits to the optical lightcurve and X-ray spectra are in agreement, from this we conclude that the case for V1408 Aql to be at a low inclination and harbor a <span class="hlt">low</span> <span class="hlt">mass</span> black hole is plausible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26613428','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26613428"><span id="translatedtitle">Hydrogen Burning in <span class="hlt">Low</span> <span class="hlt">Mass</span> Stars Constrains Scalar-Tensor Theories of Gravity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sakstein, Jeremy</p> <p>2015-11-13</p> <p>The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity and find that it is always significantly larger than the general relativity prediction. The observation of several <span class="hlt">low</span> <span class="hlt">mass</span> red dwarf stars therefore rules out a large class of scalar-tensor gravity theories and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy. PMID:26613428</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2258124V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2258124V"><span id="translatedtitle">Tracing the origin of warm water emission through the stages of <span class="hlt">low-mass</span> star formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vilhelm Persson, Magnus; Jorgensen, Jes K.; Coutens, Audrey; van Dishoeck, Ewine</p> <p>2015-08-01</p> <p>Water is a crucial molecule in the physics and chemistry of star- and planet formation, but its evolution from cold cores to disks is still poorly constrained. The gas-phase abundance of water varies between cold and warm regions up to a factor of 105 and this abundance variation makes water an excellent diagnostic of the physical structure in these sources.The origin of the warm water emission in deeply-embedded <span class="hlt">low-mass</span> protostars is still debated, however. Current options include the innermost envelope (‘hot corino’), heated by the luminosity from the central protostar; a young disk heated by shocks related to ongoing accretion or the warm disk surface layers heated radiatively by the young star. Determining the location and kinematics of the warm water is important because it provides insights into whether water, and the locked up complex organics, actually moves from the outer envelope into the disk, and if so, whether it enters the disk mostly as gas or ice. Evolutionary models suggest that water and complex species enter the disk mostly as ice but this is so far unconfirmed observationally.Thus, in our collaboration we are undertaking a study of warm water in <span class="hlt">low-mass</span> protostars. So far we have obtained interferometric maps of several isotopologues of water toward four deeply-embedded (i.e. Class 0) <span class="hlt">low-mass</span> protostars with PdBI and ALMA. The detected water emission is compact toward the Class 0 sources, and a significant source of uncertainty in determining the abundances is the poorly constrained physical structure in the inner regions. Thus we try to constrain this physical structure by fitting simple disk models to the dust continuum visibilities that are left after subtracting a model of the spherical envelope. Furthermore we estimate upper limits to the warm water content toward the Class I protostars TMC-1A and L1527 from observations with PdBI.In this talk I will summarize our ongoing work in tracing the warm water emission through the various</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013150','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013150"><span id="translatedtitle">Observations of Carbon Chain Chemistry in the Envelopes of <span class="hlt">Low-Mass</span> Protostars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cordiner, M.; Charnley, S.; Buckle, J. V.; Walsh, C.; Millar, T. J.</p> <p>2012-01-01</p> <p>Observational results are reported from our surveys in the Northern Hemisphere (using the Onsala 20 m telescope) and the Southern Hemisphere (using the Mopra 22 m telescope) to search for 3 mm emission lines from carbon-chain-bearing species and other complex molecules in the envelopes of <span class="hlt">low-mass</span> protostars. Based on a sample of approximately 60 sources, we find that carbon-chain-bearing species including HC3N (and C4H) are highly abundant in the vicinity of more than half of the observed protostars. The origin and evolution of these species, including their likely incorporation into ices in protoplanetary disks will be discussed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26613428','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26613428"><span id="translatedtitle">Hydrogen Burning in <span class="hlt">Low</span> <span class="hlt">Mass</span> Stars Constrains Scalar-Tensor Theories of Gravity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sakstein, Jeremy</p> <p>2015-11-13</p> <p>The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity and find that it is always significantly larger than the general relativity prediction. The observation of several <span class="hlt">low</span> <span class="hlt">mass</span> red dwarf stars therefore rules out a large class of scalar-tensor gravity theories and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013A%26A...559A...4C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013A%26A...559A...4C"><span id="translatedtitle">S-process in extremely metal-poor, <span class="hlt">low-mass</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cruz, M. A.; Serenelli, A.; Weiss, A.</p> <p>2013-11-01</p> <p>Context. Extremely metal-poor (EMP), <span class="hlt">low-mass</span> stars experience an ingestion of protons into the helium-rich layer during the core He-flash, resulting in the production of neutrons through the reactions 12C(p,γ)13N(β)13C(α,n)16O. This is a potential site for the production of s-process elements in EMP stars, which does not occur in more metal-rich counterparts. The signatures of s-process elements in the two most iron deficient stars observed to date, HE1327-2326 & HE0107-5240, still await for an explanation. Aims: We investigate the possibility that <span class="hlt">low-mass</span> EMP stars could be the source of s-process elements observed in extremely iron deficient stars, either as a result of self-enrichment or in a binary scenario as the consequence of a mass transfer episode. Methods: We present evolutionary and post-processing s-process calculations of a 1 M⊙ stellar model with metallicities of Z = 0, 10-8, and 10-7. We assess the sensitivity of nucleosynthesis results to uncertainties in the input physics of the stellar models with particular regard to the details of convective mixing during the core He-flash. Results: Our models provide the possibility of explaining the C, O, Sr, and Ba abundance for the star HE0107-5240 as the result of mass-transfer from a <span class="hlt">low-mass</span> EMP star. The drawback of our model is that nitrogen would be overproduced and the 12C/^{13C} abundance ratio would be underproduced in comparison to the observed values if mass would be transferred before the primary star enters the asymptotic giant branch phase. Conclusions: Our results show that <span class="hlt">low-mass</span> EMP stars cannot be ruled out as companion stars that might have polluted HE1327-2326 and HE0107-5240 and produced the observed s-process pattern. However, more detailed studies of the core He-flash and the proton ingestion episode are needed to determine the robustness of our predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.tmp.1216S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016MNRAS.tmp.1216S&link_type=ABSTRACT"><span id="translatedtitle">No evidence for a <span class="hlt">low-mass</span> black hole in Swift J1753.5-0127</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shaw, A. W.; Charles, P. A.; Casares, J.; Hernández Santisteban, J. V.</p> <p>2016-08-01</p> <p>We present high-resolution, time-resolved optical spectroscopy of the black hole X-ray transient Swift J1753.5-0127. Our optical spectra do not show features that we can associate with the companion star. However we do observe broad, double-peaked emission lines, typical of an accretion disc. We show that the mass of the compact object is likely >7.4 ± 1.2M⊙, much higher than previous suggestions of a <span class="hlt">low-mass</span> (<5M⊙) black hole.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22034651','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22034651"><span id="translatedtitle">VERY <span class="hlt">LOW</span> <span class="hlt">MASS</span> STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. I. A <span class="hlt">LOW-MASS</span> RATIO STELLAR COMPANION TO TYC 4110-01037-1 IN A 79 DAY ORBIT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wisniewski, John P.; Agol, Eric; Barnes, Rory; Ge, Jian; De Lee, Nathan; Fleming, Scott W.; Lee, Brian L.; Chang, Liang; Crepp, Justin R.; Eastman, Jason; Gaudi, B. Scott; Esposito, Massimiliano; Gonzalez Hernandez, Jonay I.; Prieto, Carlos Allende; Ghezzi, Luan; Da Costa, Luiz N.; Porto De Mello, G. F.; Stassun, Keivan G.; Cargile, Phillip; Bizyaev, Dmitry; and others</p> <p>2012-05-15</p> <p>TYC 4110-01037-1 has a <span class="hlt">low-mass</span> stellar companion, whose small mass ratio and short orbital period are atypical among binary <span class="hlt">systems</span> with solar-like (T{sub eff} {approx}< 6000 K) primary stars. Our analysis of TYC 4110-01037-1 reveals it to be a moderately aged ({approx}<5 Gyr) solar-like star having a mass of 1.07 {+-} 0.08 M{sub Sun} and radius of 0.99 {+-} 0.18 R{sub Sun }. We analyze 32 radial velocity (RV) measurements from the SDSS-III MARVELS survey as well as 6 supporting RV measurements from the SARG spectrograph on the 3.6 m Telescopio Nazionale Galileo telescope obtained over a period of {approx}2 years. The best Keplerian orbital fit parameters were found to have a period of 78.994 {+-} 0.012 days, an eccentricity of 0.1095 {+-} 0.0023, and a semi-amplitude of 4199 {+-} 11 m s{sup -1}. We determine the minimum companion mass (if sin i = 1) to be 97.7 {+-} 5.8 M{sub Jup}. The <span class="hlt">system</span>'s companion to host star mass ratio, {>=}0.087 {+-} 0.003, places it at the lowest end of observed values for short period stellar companions to solar-like (T{sub eff} {approx}< 6000 K) stars. One possible way to create such a <span class="hlt">system</span> would be if a triple-component stellar multiple broke up into a short period, low q binary during the cluster dispersal phase of its lifetime. A candidate tertiary body has been identified in the <span class="hlt">system</span> via single-epoch, high contrast imagery. If this object is confirmed to be comoving, we estimate it would be a dM4 star. We present these results in the context of our larger-scale effort to constrain the statistics of <span class="hlt">low-mass</span> stellar and brown dwarf companions to FGK-type stars via the MARVELS survey.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.459L..90C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.459L..90C"><span id="translatedtitle">The 21-cm BAO signature of enriched <span class="hlt">low-mass</span> galaxies during cosmic reionization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cohen, Aviad; Fialkov, Anastasia; Barkana, Rennan</p> <p>2016-06-01</p> <p>Studies of the formation of the first stars have established that they formed in small haloes of ˜105-106 M⊙ via molecular hydrogen cooling. Since a low level of ultraviolet radiation from stars suffices to dissociate molecular hydrogen, under the usually assumed scenario this primordial mode of star formation ended by redshift z ˜ 15 and much more massive haloes came to dominate star formation. However, metal enrichment from the first stars may have allowed the smaller haloes to continue to form stars. In this Letter, we explore the possible effect of star formation in metal-rich <span class="hlt">low-mass</span> haloes on the redshifted 21-cm signal of neutral hydrogen from z = 6 to 40. These haloes are significantly affected by the supersonic streaming velocity, with its characteristic baryon acoustic oscillation (BAO) signature. Thus, enrichment of <span class="hlt">low-mass</span> galaxies can produce a strong signature in the 21-cm power spectrum over a wide range of redshifts, especially if star formation in the small haloes was more efficient than suggested by current simulations. We show that upcoming radio telescopes can easily distinguish among various possible scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21448710','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21448710"><span id="translatedtitle">ORBITAL MIGRATION OF <span class="hlt">LOW-MASS</span> PLANETS IN EVOLUTIONARY RADIATIVE MODELS: AVOIDING CATASTROPHIC INFALL</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lyra, Wladimir; Mac Low, Mordecai-Mark; Paardekooper, Sijme-Jan E-mail: mordecai@amnh.or</p> <p>2010-06-01</p> <p>Outward migration of <span class="hlt">low-mass</span> planets has recently been shown to be a possibility in non-barotropic disks. We examine the consequences of this result in evolutionary models of protoplanetary disks. Planet migration occurs toward equilibrium radii with zero torque. These radii themselves migrate inwards because of viscous accretion and photoevaporation. We show that as the surface density and temperature fall the planet orbital migration and disk depletion timescales eventually become comparable, with the precise timing depending on the mass of the planet. When this occurs, the planet decouples from the equilibrium radius. At this time, however, the gas surface density is already too low to drive substantial further migration. A higher mass planet, of 10 M {sub +}, can open a gap during the late evolution of the disk, and stops migrating. <span class="hlt">Low-mass</span> planets, with 1 or 0.1 M {sub +}, released beyond 1 AU in our models avoid migrating into the star. Our results provide support for the reduced migration rates adopted in recent planet population synthesis models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000072579','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000072579"><span id="translatedtitle">Infrared Observations of Hot Gas and Cold Ice Toward the <span class="hlt">Low</span> <span class="hlt">Mass</span> Protostar Elias 29</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boogert, A. C. A.; Tielens, A. G. G. M.; Ceccarelli, C.; Boonman, A. M. S.; vanDishoeck, E. F.; Keane, J. V.; Whittet, D. C. B.; deGraauw, T.</p> <p>2000-01-01</p> <p>We have obtained the full 1-200 micrometer spectrum of the low luminosity (36 solar luminosity Class I protostar Elias 29 in the rho Ophiuchi molecular cloud. It provides a unique opportunity to study the origin and evolution of interstellar ice and the interrelationship of interstellar ice and hot core gases around <span class="hlt">low</span> <span class="hlt">mass</span> protostars. We see abundant hot CO and H2O gas, as well as the absorption bands of CO, CO2, H2O and "6.85 micrometer" ices. We compare the abundances and physical conditions of the gas and ices toward Elias 29 with the conditions around several well studied luminous, high mass protostars. The high gas temperature and gas/solid ratios resemble those of relatively evolved high mass objects (e.g. GL 2591). However, none of the ice band profiles shows evidence for significant thermal processing, and in this respect Elias 29 resembles the least evolved luminous protostars, such as NGC 7538 : IRS9. Thus we conclude that the heating of the envelope of the <span class="hlt">low</span> <span class="hlt">mass</span> object Elias 29 is qualitatively different from that of high mass protostars. This is possibly related to a different density gradient of the envelope or shielding of the ices in a circumstellar disk. This result is important for our understanding of the evolution of interstellar ices, and their relation to cometary ices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5594791','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5594791"><span id="translatedtitle">Effects of Cosmions upon the structure and evolution of very <span class="hlt">low</span> <span class="hlt">mass</span> stars</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Deluca, E.E.; Griest, K.; Rosner, R.; Wang, J.</p> <p>1989-02-01</p> <p>A number of recent studies have suggested that cosmions, or WIMPS, may play an important role in the energetics of the solar interior; in particular, it has been argued that these hypothetical particles may transport sufficient energy within the nuclear-burning solar core so as to depress the solar core temperature to the point of resolving the solar neutrino problem. Solutions to the solar neutrino problem have proven themselves to be quite nonunique, so that it is of some interest whether the cosmion solution can be tested in some independent manner. It is argued that if cosmions solve the solar neutrino problem, then they must also play an important role in the evolution of <span class="hlt">low</span> <span class="hlt">mass</span> main sequence stars; and, second, that if they do so, then a simple (long mean free path) model for the interaction of cosmions with baryons leads to changes in the structure of the nuclear-burning core which may be in principal observable. Such changes include suppression of a fully-convective core in very <span class="hlt">low</span> <span class="hlt">mass</span> main sequence stars; and a possible thermal runaway in the core of the nuclear burning region. Some of these changes may be directly observable, and hence may provide independent constraints on the properties of the cosmions required to solve the solar neutrino problem, perhaps even ruling them out.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MNRAS.392.1034O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MNRAS.392.1034O"><span id="translatedtitle">The <span class="hlt">low-mass</span> initial mass function in the young cluster NGC6611</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oliveira, J. M.; Jeffries, R. D.; van Loon, J. Th.</p> <p>2009-01-01</p> <p>NGC6611 is the massive young cluster (2-3Myr) that ionizes the Eagle Nebula. We present very deep photometric observations of the central region of NGC6611 obtained with the Hubble Space Telescope and the following filters: ACS/WFC F775W and F850LP and NIC2 F110W and F160W, loosely equivalent to ground-based IZJH filters. This survey reaches down to I ~ 26mag. We construct the initial mass function (IMF) from ~1.5Msolar well into the brown dwarf regime (down to ~0.02Msolar). We have detected 30-35 brown dwarf candidates in this sample. The <span class="hlt">low-mass</span> IMF is combined with a higher-mass IMF constructed from the ground-based catalogue from Oliveira et al. We compare the final IMF with those of well-studied star-forming regions: we find that the IMF of NGC6611 more closely resembles that of the <span class="hlt">low-mass</span> star-forming region in Taurus than that of the more massive Orion Nebula Cluster. We conclude that there seems to be no severe environmental effect in the IMF due to the proximity of the massive stars in NGC6611.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22126621','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22126621"><span id="translatedtitle">GAP OPENING BY EXTREMELY <span class="hlt">LOW-MASS</span> PLANETS IN A VISCOUS DISK</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Duffell, Paul C.; MacFadyen, Andrew I. E-mail: macfadyen@nyu.edu</p> <p>2013-05-20</p> <p>By numerically integrating the compressible Navier-Stokes equations in two dimensions, we calculate the criterion for gap formation by a very <span class="hlt">low</span> <span class="hlt">mass</span> (q {approx} 10{sup -4}) protoplanet on a fixed orbit in a thin viscous disk. In contrast with some previously proposed gap-opening criteria, we find that a planet can open a gap even if the Hill radius is smaller than the disk scale height. Moreover, in the low-viscosity limit, we find no minimum mass necessary to open a gap for a planet held on a fixed orbit. In particular, a Neptune-mass planet will open a gap in a minimum mass solar nebula with suitably low viscosity ({alpha} {approx}< 10{sup -4}). We find that the mass threshold scales as the square root of viscosity in the <span class="hlt">low</span> <span class="hlt">mass</span> regime. This is because the gap width for critical planet masses in this regime is a fixed multiple of the scale height, not of the Hill radius of the planet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014hst..prop13860G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014hst..prop13860G"><span id="translatedtitle">Investigating the <span class="hlt">low-mass</span> slope and possible turnover in the LMC IMF</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gennaro, Mario</p> <p>2014-10-01</p> <p>We propose to derive the Initial Mass Function (IMF) of the field population of the Large Magellanic Cloud (LMC) down to 0.2 solar masses, probing the mass regime where the characteristic IMF turnover is observed in our Galaxy. The power of the HST, using the WFC3 IR channel, is necessary to obtain photometric mass estimates for the faint, cool, dwarf stars with masses below the expected IMF turnover point. Only by probing the IMF down to such masses, it will be possible to clearly distinguish between a bottom-heavy or bottom-light IMF in the LMC. Recent studies, using the deepest available observations for the Small Magellanic Cloud, cannot find clear evidence of a turnover in the IMF for this galaxy, suggesting a bottom-heavy IMF in contrast to the Milky Way. A similar study of the LMC is needed to confirm a possible dependence of the <span class="hlt">low-mass</span> IMF with galactic environment. Studies of giant ellipticals have recently challenged the picture of a universal IMF, and suggest an enviromental dependence of the IMF, with the most massive galaxies having a larger fraction of <span class="hlt">low</span> <span class="hlt">mass</span> stars and no IMF turnover. A study of possible IMF variations from resolved stellar populations in nearby galaxies is of great importance in sheding light on this issue. Our simple approach, using direct evidence from basic star counts, is much less prone to systematic errors with respect to studies of more distant objects which have to rely on the observations of integrated properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...797L..32A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...797L..32A"><span id="translatedtitle">The Mass Distribution of Companions to <span class="hlt">Low-mass</span> White Dwarfs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andrews, Jeff J.; Price-Whelan, Adrian M.; Agüeros, Marcel A.</p> <p>2014-12-01</p> <p>Measuring the masses of companions to single-line spectroscopic binary stars is (in general) not possible because of the unknown orbital plane inclination. Even when the mass of the visible star can be measured, only a lower limit can be placed on the mass of the unseen companion. However, since these inclination angles should be isotropically distributed, for a large enough, unbiased sample, the companion mass distribution can be deconvolved from the distribution of observables. In this work, we construct a hierarchical probabilistic model to infer properties of unseen companion stars given observations of the orbital period and projected radial velocity of the primary star. We apply this model to three mock samples of <span class="hlt">low-mass</span> white dwarfs (LMWDs; M <~ 0.45 M ⊙) and a sample of post-common-envelope binaries. We use a mixture of two Gaussians to model the WD and neutron star (NS) companion mass distributions. Our model successfully recovers the initial parameters of these test data sets. We then apply our model to 55 WDs in the extremely <span class="hlt">low-mass</span> (ELM) WD Survey. Our maximum a posteriori model for the WD companion population has a mean mass μWD = 0.74 M ⊙, with a standard deviation σWD = 0.24 M ⊙. Our model constrains the NS companion fraction f NS to be <16% at 68% confidence. We make samples from the posterior distribution publicly available so that future observational efforts may compute the NS probability for newly discovered LMWDs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040034774&hterms=survey+instrument&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsurvey%2Binstrument','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040034774&hterms=survey+instrument&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsurvey%2Binstrument"><span id="translatedtitle">A Deep HRI Survey of <span class="hlt">Low-Mass</span> PMS Stars in NGC 2264</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Patten, Brian</p> <p>1999-01-01</p> <p>Brian Patten is the Principal Investigator of the NASA ADP project 'A Deep HRI Survey of <span class="hlt">Low-Mass</span> PMS Stars in NGC 2264'. This project was funded to support primarily the data reduction and analysis for new ROSAT data to be acquired in ROSAT AO8. For AO8 we were awarded two deep (100 ks) exposures with the ROSAT HRI instrument of a rotation and proper-motion selected sample of young (3 Myr - 15 Myr), <span class="hlt">low-mass</span>, PMS stars in the populous star-forming region NGC 2264. These X-ray data were to be combined with an extensive rotation database for members of this cluster to allow us, for the first time, to probe the early evolution of magnetic dynamo activity for both fully convective stars and those stars found lower on the Hayashi tracks which have developed radiative cores. This database would have been used to study the interrelationship between coronal activity level, interior structure, and rotation rate as a function of mass and age.in the PMS and to define empirical constraints for theoretical models of angular momentum and magnetic dynamo evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PASJ...68...40M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PASJ...68...40M"><span id="translatedtitle">An effective selection method for <span class="hlt">low-mass</span> active black holes and first spectroscopic identification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morokuma, Tomoki; Tominaga, Nozomu; Tanaka, Masaomi; Yasuda, Naoki; Furusawa, Hisanori; Taniguchi, Yuki; Kato, Takahiro; Jiang, Ji-an; Nagao, Tohru; Kuncarayakti, Hanindyo; Morokuma-Matsui, Kana; Ikeda, Hiroyuki; Blinnikov, Sergei; Nomoto, Ken'ichi; Kokubo, Mitsuru; Doi, Mamoru</p> <p>2016-06-01</p> <p>We present a new method for effectively selecting objects which may be <span class="hlt">low-mass</span> active black holes (BHs) at galaxy centers using high-cadence optical imaging data, and our first spectroscopic identification of an active 2.7 × 106 M⊙ BH at z = 0.164. This active BH was originally selected due to its rapid optical variability, from a few hours to a day, based on Subaru Hyper Suprime-Cam g-band imaging data taken with a 1 hr cadence. Broad and narrow Hα lines and many other emission ones are detected in our optical spectra taken with Subaru FOCAS, and the BH mass is measured via the broad Hα emission line width (1880 km s-1) and luminosity (4.2 × 1040 erg s-1) after careful correction to the atmospheric absorption around 7580-7720 Å. We measure the Eddington ratio and find it to be as low as 0.05, considerably smaller than those in a previous SDSS sample with similar BH mass and redshift, which indicates one of the special potentials of our Subaru survey. The g - r color and morphology of the extended component indicate that the host galaxy is a star-forming galaxy. We also show the effectiveness of our variability selection for <span class="hlt">low-mass</span> active BHs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21124316','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21124316"><span id="translatedtitle">A substantial population of <span class="hlt">low-mass</span> stars in luminous elliptical galaxies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>van Dokkum, Pieter G; Conroy, Charlie</p> <p>2010-12-16</p> <p>The stellar initial mass function (IMF) describes the mass distribution of stars at the time of their formation and is of fundamental importance for many areas of astrophysics. The IMF is reasonably well constrained in the disk of the Milky Way but we have very little direct information on the form of the IMF in other galaxies and at earlier cosmic epochs. Here we report observations of the Na (I) doublet and the Wing-Ford molecular FeH band in the spectra of elliptical galaxies. These lines are strong in stars with masses less than 0.3M(⊙) (where M(⊙) is the mass of the Sun) and are weak or absent in all other types of stars. We unambiguously detect both signatures, consistent with previous studies that were based on data of lower signal-to-noise ratio. The direct detection of the light of <span class="hlt">low-mass</span> stars implies that they are very abundant in elliptical galaxies, making up over 80% of the total number of stars and contributing more than 60% of the total stellar mass. We infer that the IMF in massive star-forming galaxies in the early Universe produced many more <span class="hlt">low-mass</span> stars than the IMF in the Milky Way disk, and was probably slightly steeper than the Salpeter form in the mass range 0.1M(⊙) to 1M(⊙).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..APRH15004O&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..APRH15004O&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Low-mass</span> neutron stars: universal relations, the nuclear symmetry energy and gravitational radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O. Silva, Hector; Berti, Emanuele; Sotani, Hajime</p> <p>2016-03-01</p> <p>Compact objects such as neutron stars are ideal astrophysical laboratories to test our understanding of the fundamental interactions in the regime of supranuclear densities, unachievable by terrestrial experiments. Despite recent progress, the description of matter (i.e., the equation of state) at such densities is still debatable. This translates into uncertainties in the bulk properties of neutron stars, masses and radii for instance. Here we will consider <span class="hlt">low-mass</span> neutron stars. Such stars are expected to carry important information on nuclear matter near the nuclear saturation point. It has recently been shown that the masses and surface redshifts of <span class="hlt">low-mass</span> neutron stars smoothly depend on simple functions of the central density and of a characteristic parameter η associated with the choice of equation of state. Here we extend these results to slowly-rotating and tidally deformed stars and obtain empirical relations for various quantities, such as the moment of inertia, quadrupole moment and ellipticity, tidal and rotational Love numbers, and rotational apsidal constants. We discuss how these relations might be used to constrain the equation of state by future observations in the electromagnetic and gravitational-wave spectra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22365266','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22365266"><span id="translatedtitle">Formation of millisecond pulsars with <span class="hlt">low-mass</span> helium white dwarf companions in very compact binaries</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jia, Kun; Li, X.-D.</p> <p>2014-08-20</p> <p>Binary millisecond pulsars (BMSPs) are thought to have evolved from <span class="hlt">low-mass</span> X-ray binaries (LMXBs). If the mass transfer in LMXBs is driven by nuclear evolution of the donor star, the final orbital period is predicted to be well correlated with the mass of the white dwarf (WD), which is the degenerate He core of the donor. Here we show that this relation can be extended to very small WD mass (∼0.14-0.17 M {sub ☉}) and narrow orbital period (about a few hours), depending mainly on the metallicities of the donor stars. There is also discontinuity in the relation, which is due to the temporary contraction of the donor when the H-burning shell crosses the hydrogen discontinuity. BMSPs with <span class="hlt">low-mass</span> He WD companions in very compact binaries can be accounted for if the progenitor binary experienced very late Case A mass transfer. The WD companion of PSR J1738+0333 is likely to evolve from a Pop II star. For PSR J0348+0432, to explain its extreme compact orbit in the Roche-lobe-decoupling phase, even lower metallicity (Z = 0.0001) is required.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22522275','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22522275"><span id="translatedtitle">POTENTIAL GAMMA-RAY EMISSIONS FROM <span class="hlt">LOW-MASS</span> X-RAY BINARY JETS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhang, Jian-Fu; Gu, Wei-Min; Liu, Tong; Xue, Li; Lu, Ju-Fu E-mail: guwm@xmu.edu.cn</p> <p>2015-06-20</p> <p>By proposing a pure leptonic radiation model, we study the potential gamma-ray emissions from the jets of <span class="hlt">low-mass</span> X-ray binaries. In this model, the relativistic electrons that are accelerated in the jets are responsible for radiative outputs. Nevertheless, jet dynamics are dominated by magnetic and proton–matter kinetic energies. The model involves all kinds of related radiative processes and considers the evolution of relativistic electrons along the jet by numerically solving the kinetic equation. Numerical results show that the spectral energy distributions can extend up to TeV bands, in which synchrotron radiation and synchrotron self-Compton scattering are dominant components. As an example, we apply the model to the <span class="hlt">low-mass</span> X-ray binary GX 339–4. The results not only can reproduce the currently available observations from GX 339–4, but also predict detectable radiation at GeV and TeV bands by the Fermi and CTA telescopes. Future observations with Fermi and CTA can be used to test our model, which could be employed to distinguish the origin of X-ray emissions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22370121','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22370121"><span id="translatedtitle">A pulsation search among young brown dwarfs and very-<span class="hlt">low-mass</span> stars</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cody, Ann Marie; Hillenbrand, Lynne A.</p> <p>2014-12-01</p> <p>In 2005, Palla and Baraffe proposed that brown dwarfs (BDs) and very-<span class="hlt">low-mass</span> stars (VLMSs; < 0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of one to four hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of <span class="hlt">low-mass</span> objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters σ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity t