Deficit of Wide Binaries in the η Chamaeleontis Young Cluster

NASA Astrophysics Data System (ADS)

Brandeker, Alexis; Jayawardhana, Ray; Khavari, Parandis; Haisch, Karl E., Jr.; Mardones, Diego

2006-12-01

We have carried out a sensitive high-resolution imaging survey of stars in the young (6-8 Myr), nearby (97 pc) compact cluster around η Chamaeleontis to search for stellar and substellar companions. Our data were obtained using the NACO adaptive optics system on the ESO Very Large Telescope (VLT). Given its youth and proximity, any substellar companions are expected to be luminous, especially in the near-infrared, and thus easier to detect next to their parent stars. Here, we present VLT NACO adaptive optics imaging with companion detection limits for 17 η Cha cluster members, and follow-up VLT ISAAC near-infrared spectroscopy for companion candidates. The widest binary detected is ~0.2", corresponding to the projected separation 20 AU, despite our survey being sensitive down to substellar companions outside 0.3", and planetary-mass objects outside 0.5". This implies that the stellar companion probability outside 0.3" and the brown dwarf companion probability outside 0.5" are less than 0.16 with 95% confidence. We compare the wide binary frequency of η Cha to that of the similarly aged TW Hydrae association and estimate the statistical likelihood that the wide binary probability is equal in both groups to be less than 2×10-4. Even though the η Cha cluster is relatively dense, stellar encounters in its present configuration cannot account for the relative deficit of wide binaries. We thus conclude that the difference in wide binary probability in these two groups provides strong evidence for multiplicity properties being dependent on environment. In two appendices we derive the projected separation probability distribution for binaries, used to constrain physical separations from observed projected separations, and summarize statistical tools useful for multiplicity studies.

Measuring Fundamental Parameters of Substellar Objects. I. Surface Gravities

NASA Astrophysics Data System (ADS)

Mohanty, Subhanjoy; Basri, Gibor; Jayawardhana, Ray; Allard, France; Hauschildt, Peter; Ardila, David

2004-07-01

We present an analysis of high-resolution optical spectra for a sample of very young, mid- to late-M, low-mass stellar and substellar objects: 11 in the Upper Scorpius association, and two (GG Tau Ba and Bb) in the Taurus star-forming region. Effective temperatures and surface gravities are derived from a multiple-feature spectral analysis using TiO, Na I, and K I, through comparison with the latest synthetic spectra. We show that these spectral diagnostics complement each other, removing degeneracies with temperature and gravity in the behavior of each. In combination, they allow us to determine temperature to within 50 K and gravity to within 0.25 dex, in very cool young objects. Our high-resolution spectral analysis does not require extinction estimates. Moreover, it yields temperatures and gravities independent of theoretical evolutionary models (although our estimates do depend on the synthetic spectral modeling). We find that our gravities for most of the sample agree remarkably well with the isochrone predictions for the likely cluster ages. However, discrepancies appear in our coolest targets: these appear to have significantly lower gravity (by up to 0.75 dex) than our hotter objects, even though our entire sample covers a relatively narrow range in effective temperature (~300 K). This drop in gravity is also implied by intercomparisons of the data alone, without recourse to synthetic spectra. We consider, and argue against, dust opacity, cool stellar spots, or metallicity differences leading to the observed spectral effects; a real decline in gravity is strongly indicated. Such gravity variations are contrary to the predictions of the evolutionary tracks, causing improbably low ages to be inferred from the tracks for our coolest targets. Through a simple consideration of contraction timescales, we quantify the age errors introduced into the tracks through the particular choice of initial conditions and demonstrate that they can be significant for low-mass objects that are only a few megayears old. However, we also find that these errors appear insufficient to explain the magnitude of the age offsets in our lowest gravity targets. We venture that this apparent age offset may arise from evolutionary model uncertainties related to accretion, deuterium burning and/or convection effects. Finally, when combined with photometry and distance information, our technique for deriving surface gravities and effective temperatures provides a way of obtaining masses and radii for substellar objects independent of evolutionary models; radius and mass determinations are presented in Paper II.

Characterizing a New Candidate Benchmark Brown Dwarf Companion in the β Pic Moving Group

NASA Astrophysics Data System (ADS)

Phillips, Caprice; Bowler, Brendan; Liu, Michael C.; Mace, Gregory N.; Sokal, Kimberly R.

2018-01-01

Benchmark brown dwarfs are objects that have at least two measured fundamental quantities such as luminosity and age, and therefore can be used to test substellar atmospheric and evolutionary models. Nearby, young, loose associations such as the β Pic moving group represent some of the best regions in which to identify intermediate-age benchmark brown dwarfs due to their well-constrained ages and metallicities. We present a spectroscopic study of a new companion at the hydrogen-burning limit orbiting a low-mass star at a separation of 9″ (650 AU) in the 23 Myr old β Pic moving group. The medium-resolution near-infrared spectrum of this companion from IRTF/SpeX shows clear signs of low surface gravity and yields an index-based spectral type of M6±1 with a VL-G gravity on the Allers & Liu classification system. Currently, there are four known brown dwarf and giant planet companions in the β Pic moving group: HR 7329 B, PZ Tel B, β Pic b, and 51 Eri b. Depending on its exact age and accretion history, this new object may represent the third brown dwarf companion and fifth substellar companion in this association.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geier, S.; Edelmann, H.; Heber, U.

Substellar objects, like planets and brown dwarfs orbiting stars, are by-products of the star formation process. The evolution of their host stars may have an enormous impact on these small companions. Vice versa a planet might also influence stellar evolution as has recently been argued. Here, we report the discovery of an 8-23 Jupiter-mass substellar object orbiting the hot subdwarf HD 149382 in 2.391 d at a distance of only about five solar radii. Obviously, the companion must have survived engulfment in the red giant envelope. Moreover, the substellar companion has triggered envelope ejection and enabled the sdB star tomore » form. Hot subdwarf stars have been identified as the sources of the unexpected ultraviolet (UV) emission in elliptical galaxies, but the formation of these stars is not fully understood. Being the brightest star of its class, HD 149382 offers the best conditions to detect the substellar companion. Hence, undisclosed substellar companions offer a natural solution for the long-standing formation problem of apparently single hot subdwarf stars. Planets and brown dwarfs may therefore alter the evolution of old stellar populations and may also significantly affect the UV emission of elliptical galaxies.« less

BROWN DWARFS IN YOUNG MOVING GROUPS FROM PAN-STARRS1. I. AB DORADUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aller, Kimberly M.; Liu, Michael C.; Magnier, Eugene A.

Substellar members of young (≲150 Myr) moving groups are valuable benchmarks to empirically define brown dwarf evolution with age and to study the low-mass end of the initial mass function. We have combined Pan-STARRS1 (PS1) proper motions with optical–IR photometry from PS1, Two Micron All Sky Survey (2MASS), and WISE to search for substellar members of the AB Dor Moving Group within ≈50 pc and with spectral types of late M to early L, corresponding to masses down to ≈30 M {sub Jup} at the age of the group (≈125 Myr). Including both photometry and proper motions allows us tomore » better select candidates by excluding field dwarfs whose colors are similar to young AB Dor Moving Group members. Our near-IR spectroscopy has identified six ultracool dwarfs (M6–L4; ≈30–100 M {sub Jup}) with intermediate surface gravities (int-g) as candidate members of the AB Dor Moving Group. We find another two candidate members with spectra showing hints of youth but consistent with field gravities. We also find four field brown dwarfs unassociated with the AB Dor Moving Group, three of which have int-g gravity classification. While signatures of youth are present in the spectra of our ≈125 Myr objects, neither their J – K nor W 1 – W 2 colors are significantly redder than field dwarfs with the same spectral types, unlike younger ultracool dwarfs. We also determined PS1 parallaxes for eight of our candidates and one previously identified AB Dor Moving Group candidate. Although radial velocities (and parallaxes, for some) are still needed to fully assess membership, these new objects provide valuable insight into the spectral characteristics and evolution of young brown dwarfs.« less

The SEEDS High-Contrast Imaging Survey of Exoplanets Around Young Stellar Objects

NASA Astrophysics Data System (ADS)

Uyama, Taichi; Hashimoto, Jun; Kuzuhara, Masayuki; Mayama, Satoshi; Akiyama, Eiji; Currie, Thayne; Livingston, John; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R.; Kwon, Jungmi; Matsuo, Taro; Mcelwain, Michael W.; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takahashi, Yasuhiro H.; Takami, Michihiro; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

2017-03-01

We present high-contrast observations of 68 young stellar objects (YSOs) that have been explored as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey on the Subaru telescope. Our targets are very young (<10 Myr) stars, which often harbor protoplanetary disks where planets may be forming. We achieve a typical contrast of ˜10-4-10-5.5 at an angular distance of 1″ from the central star, corresponding to typical mass sensitivities (assuming hot-start evolutionary models) of ˜10 M J at 70 au and ˜6 M J at 140 au. We detected a new stellar companion to HIP 79462 and confirmed the substellar objects GQ Lup b and ROXs 42B b. An additional six companion candidates await follow-up observations to check for common proper motion. Our SEEDS YSO observations probe the population of planets and brown dwarfs at the very youngest ages; these may be compared to the results of surveys targeting somewhat older stars. Our sample and the associated observational results will help enable detailed statistical analyses of giant planet formation.

Cloudless Atmospheres for Young Low-Gravity Substellar Objects

NASA Technical Reports Server (NTRS)

Tremblin, P.; Chabrier, G.; Baraffe, I.; Liu, Michael C.; Magnier, E. A.; Lagage, P.-O.; De Oliveira, C. Alves; Burgasser, A. J.; Amundsen, D. S.; Drummond, B.

2017-01-01

Atmospheric modeling of low-gravity (VL-G) young brown dwarfs remains challenging. The presence of very thick clouds is a possible source of this challenge, because of their extremely red near-infrared (NIR) spectra, but no cloud models provide a good fit to the data with a radius compatible with the evolutionary models for these objects. We show that cloudless atmospheres assuming a temperature gradient reduction caused by fingering convection provide a very good model to match the observed VL-G NIR spectra. The sequence of extremely red colors in the NIR for atmospheres with effective temperatures from approx. 2000 K down to approx. 1200 K is very well reproduced with predicted radii typical of young low-gravity objects. Future observations with NIRSPEC and MIRI on the James Webb Space Telescope (JWST) will provide more constraints in the mid-infrared, helping to confirm or refute whether or not the NIR reddening is caused by fingering convection. We suggest that the presence or absence of clouds will be directly determined by the silicate absorption features that can be observed with MIRI. JWST will therefore be able to better characterize the atmosphere of these hot young brown dwarfs and their low-gravity exoplanet analogs.

Early phases in the stellar and substellar formation and evolution. Infrared and submillimeter data in the Barnard 30 dark cloud

NASA Astrophysics Data System (ADS)

Barrado, D.; de Gregorio Monsalvo, I.; Huélamo, N.; Morales-Calderón, M.; Bayo, A.; Palau, A.; Ruiz, M. T.; Rivière-Marichalar, P.; Bouy, H.; Morata, Ó.; Stauffer, J. R.; Eiroa, C.; Noriega-Crespo, A.

2018-04-01

Aims: The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs. Methods: We have conducted deep observations at 870 μm obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information. Results: We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70 μm, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects. Conclusions: Our findings provide additional evidence concerning the BD formation mechanism, which seems to be a downsized version of the stellar formation. Tables 3-7 and reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/vol/page

The BANYAN-Sigma Bayesian classifier and the search for isolated planetary-mass objects

NASA Astrophysics Data System (ADS)

Gagné, Jonathan

2018-01-01

I will present new developments in the construction of a Bayesian classification tool to identify members of 22 young associations within 150 pc from partially complete kinematic data sets such as Gaia-DR1 and DR2. The new BANYAN-Sigma tool makes it possible to quickly analyze massive data sets and yields a better classification performance than all its predecessors. It will open the door to large-scale surveys to complete the stellar and substellar populations of nearby associations, which will provide deep insights in the low-mass end of the initial mass function and valuable age-calibrated targets for exoplanet surveys.I will also presents preliminary results of a search for T-type isolated planetary-mass objects in these young associations, based on BANYAN-Sigma and a cross-match between the AllWISE and 2MASS-Reject catalogs.

A survey for low-mass stellar and substellar members of the Hyades open cluster

NASA Astrophysics Data System (ADS)

Melnikov, Stanislav; Eislöffel, Jochen

2018-03-01

Context. Unlike young open clusters (with ages < 250 Myr), the Hyades cluster (age 600 Myr) has a clear deficit of very low-mass stars (VLM) and brown dwarfs (BD). Since this open cluster has a low stellar density and covers several tens of square degrees on the sky, extended surveys are required to improve the statistics of the VLM/BD objects in the cluster. Aim. We search for new VLM stars and BD candidates in the Hyades cluster to improve the present-day cluster mass function down to substellar masses. Methods: An imaging survey of the Hyades with a completeness limit of 21.m5 in the R band and 20.m5 in the I band was carried out with the 2k × 2k CCD Schmidt camera at the 2 m Alfred Jensch Telescope in Tautenburg. We performed a photometric selection of the cluster member candidates by combining results of our survey with 2MASS JHKs photometry Results: We present a photometric and proper motion survey covering 23.4 deg2 in the Hyades cluster core region. Using optical/IR colour-magnitude diagrams, we identify 66 photometric cluster member candidates in the magnitude range 14.m7 < I < 20.m5. The proper motion measurements are based on several all-sky surveys with an epoch difference of 60-70 yr for the bright objects. The proper motions allowed us to discriminate the cluster members from field objects and resulted in 14 proper motion members of the Hyades. We rediscover Hy 6 as a proper motion member and classify it as a substellar object candidate (BD) based on the comparison of the observed colour-magnitude diagram with theoretical model isochrones. Conclusions: With our results, the mass function of the Hyades continues to be shallow below 0.15 M⊙ indicating that the Hyades have probably lost their lowest mass members by means of dynamical evolution. We conclude that the Hyades core represents the "VLM/BD desert" and that most of the substeller objects may have already left the volume of the cluster.

The Gemini NICI Planet-finding Campaign: Discovery of a Substellar L Dwarf Companion to the Nearby Young M Dwarf CD-35 2722

NASA Astrophysics Data System (ADS)

Wahhaj, Zahed; Liu, Michael C.; Biller, Beth A.; Clarke, Fraser; Nielsen, Eric L.; Close, Laird M.; Hayward, Thomas L.; Mamajek, Eric E.; Cushing, Michael; Dupuy, Trent; Tecza, Matthias; Thatte, Niranjan; Chun, Mark; Ftaclas, Christ; Hartung, Markus; Reid, I. Neill; Shkolnik, Evgenya L.; Alencar, Silvia H. P.; Artymowicz, Pawel; Boss, Alan; de Gouveia Dal Pino, Elisabethe; Gregorio-Hetem, Jane; Ida, Shigeru; Kuchner, Marc; Lin, Douglas N. C.; Toomey, Douglas W.

2011-03-01

We present the discovery of a wide (67 AU) substellar companion to the nearby (21 pc) young solar-metallicity M1 dwarf CD-35 2722, a member of the ≈100 Myr AB Doradus association. Two epochs of astrometry from the NICI Planet-Finding Campaign confirm that CD-35 2722 B is physically associated with the primary star. Near-IR spectra indicate a spectral type of L4±1 with a moderately low surface gravity, making it one of the coolest young companions found to date. The absorption lines and near-IR continuum shape of CD-35 2722 B agree especially well the dusty field L4.5 dwarf 2MASS J22244381-0158521, while the near-IR colors and absolute magnitudes match those of the 5 Myr old L4 planetary-mass companion, 1RXS J160929.1-210524 b. Overall, CD-35 2722 B appears to be an intermediate-age benchmark for L dwarfs, with a less peaked H-band continuum than the youngest objects and near-IR absorption lines comparable to field objects. We fit Ames-Dusty model atmospheres to the near-IR spectra and find T eff= 1700-1900 K and log(g)= 4.5 ± 0.5. The spectra also show that the radial velocities of components A and B agree to within ±10 km s-1, further confirming their physical association. Using the age and bolometric luminosity of CD-35 2722 B, we derive a mass of 31 ± 8 M Jup from the Lyon/Dusty evolutionary models. Altogether, young late-M to mid-L type companions appear to be overluminous for their near-IR spectral type compared with field objects, in contrast to the underluminosity of young late-L and early-T dwarfs. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Evidence that the Planetary Candidate CVSO30c is a Background Star from Optical, Seeing-limited Data

NASA Astrophysics Data System (ADS)

Lee, Chien-Hsiu; Chiang, Po-Shih

2018-01-01

We report serendipitous optical imaging of CVSO30c, an exoplanet candidate associated with the pre-main-sequence T Tauri star CVSO30 that resides in the 25 Ori stellar cluster. We perform PSF modeling on our seeing-limited optical image to remove the lights from the host star (CVSO30), allowing us to extract photometry of CVSO30c to be g = 23.2 ± 0.2 (statistic) ± 0.1 (systematic) and r = 21.5 ± 0.1 (statistic) ± 0.1 (systematic) magnitudes, respectively. This is 170 and 80 times too bright in the g and r bands, respectively, if CVSO30c were an L0 substellar object as suggested by previous studies. The optical/infrared colors of CVSO30c are indicative of a stellar, not substellar object, while the object’s color–magnitude diagram position is strikingly inconsistent with expected values for a low-mass member of 25 Ori. Broadband photometry for CVSO30c is instead better fit by contaminants such as a background K3 giant or M subdwarf. Our study demonstrates that optical seeing-limited data can help clarify the nature of candidate wide separation planet-mass companions in young star-forming regions.

A Test of Pre-Main-Sequence Evolutionary Models across the Stellar/Substellar Boundary Based on Spectra of the Young Quadruple GG Tauri

NASA Astrophysics Data System (ADS)

White, Russel J.; Ghez, A. M.; Reid, I. Neill; Schultz, Greg

1999-08-01

We present spatially separated optical spectra of the components of the young hierarchical quadruple GG Tau. Spectra of GG Tau Aa and Ab (separation 0.25"~35 AU) were obtained with the Faint Object Spectrograph on board the Hubble Space Telescope. Spectra of GG Tau Ba and Bb (separation 1.48"~207 AU) were obtained with both the HIRES and the LRIS spectrographs on the W. M. Keck telescopes. The components of this minicluster, which span a wide range in spectral type (K7-M7), are used to test both evolutionary models and the temperature scale for very young, low-mass stars under the assumption of coeval formation. Of the evolutionary models tested, those of Baraffe et al. yield the most consistent ages when combined with a temperature scale intermediate between that of dwarfs and giants. The version of the Baraffe et al. models computed with a mixing length nearly twice the pressure scale height is of particular interest, as it predicts masses for GG Tau Aa and Ab that are in agreement with their dynamical mass estimate. Using this evolutionary model and a coeval (at 1.5 Myr) temperature scale, we find that the coldest component of the GG Tau system, GG Tau Bb, is substellar with a mass of 0.044+/-0.006 Msolar. This brown dwarf companion is especially intriguing as it shows signatures of accretion, although this accretion is not likely to alter its mass significantly. GG Tau Bb is currently the lowest mass, spectroscopically confirmed companion to a T Tauri star, and is one of the coldest, lowest mass T Tauri objects in the Taurus-Auriga star-forming region. Based partly on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Star Formation in the Eagle Nebula

NASA Astrophysics Data System (ADS)

Oliveira, J. M.

2008-12-01

M16 (the Eagle Nebula) is a striking star forming region, with a complex morphology of gas and dust sculpted by the massive stars in NGC 6611. Detailed studies of the famous ``elephant trunks'' dramatically increased our understanding of the massive star feedback into the parent molecular cloud. A rich young stellar population (2-3 Myr) has been identified, from massive O-stars down to substellar masses. Deep into the remnant molecular material, embedded protostars, Herbig-Haro objects and maser sources bear evidence of ongoing star formation in the nebula, possibly triggered by the massive cluster members. M 16 is a excellent template for the study of star formation under the hostile environment created by massive O-stars. This review aims at providing an observational overview not only of the young stellar population but also of the gas remnant of the star formation process.

The MUCHFUSS photometric campaign

NASA Astrophysics Data System (ADS)

Schaffenroth, V.; Geier, S.; Heber, U.; Gerber, R.; Schneider, D.; Ziegerer, E.; Cordes, O.

2018-06-01

Hot subdwarfs (sdO/Bs) are the helium-burning cores of red giants, which have lost almost all of their hydrogen envelope. This mass loss is often triggered by common envelope interactions with close stellar or even substellar companions. Cool companions like late-type stars or brown dwarfs are detectable via characteristic light-curve variations like reflection effects and often also eclipses. To search for such objects, we obtained multi-band light curves of 26 close sdO/B binary candidates from the MUCHFUSS project with the BUSCA instrument. We discovered a new eclipsing reflection effect system (P = 0.168938 d) with a low-mass M dwarf companion (0.116 M⊙). Three more reflection effect binaries found in the course of the campaign have already been published; two of them are eclipsing systems, and in one system only showing the reflection effect but no eclipses, the sdB primary is found to be pulsating. Amongst the targets without reflection effect a new long-period sdB pulsator was discovered and irregular light variations were found in two sdO stars. The found light variations allowed us to constrain the fraction of reflection effect binaries and the substellar companion fraction around sdB stars. The minimum fraction of reflection effect systems amongst the close sdB binaries might be greater than 15% and the fraction of close substellar companions in sdB binaries may be as high as 8.0%. This would result in a close substellar companion fraction to sdB stars of about 3%. This fraction is much higher than the fraction of brown dwarfs around possible progenitor systems, which are solar-type stars with substellar companions around 1 AU, as well as close binary white dwarfs with brown dwarf companions. This might suggest that common envelope interactions with substellar objects are preferentially followed by a hot subdwarf phase.

Confirming Planetary Mass Candidate Companions in Ophiuchus

NASA Astrophysics Data System (ADS)

Fontanive, Clemence

2016-10-01

We propose for follow-up observations to confirm common proper motion for two candidate planetary mass companions, identified as part of our GO 12944 (PI Allers) search for companions to the youngest ( 0.5 Myr) brown dwarfs in the nearby Ophiuchus star-forming region. If confirmed to be co-moving, these would be among the lowest mass planetary mass companions imaged to date, with estimated masses <5 Jupiter Masses and would be vital benchmark objects for evolutionary models at these young ages. With our multi-band optical and IR photometric approach based on the SpT-Q relation seen for Ophiuchus brown dwarfs (Allers in prep.), we have already estimated the spectral type of our candidate companions. This approach distinguishes substellar objects from background interlopers based on the strength of the 1.4 um water feature robustly observed in MLTY objects but not in reddened background stars - both our candidates show clear evidence of absorption at 1.4 um. If confirmed, these candidate companions would significantly increase the census of young planetary mass companions around extremely young brown dwarfs. These candidate companions are too faint to be observed with ground-based laser guide star adaptive optics (LGS AO) nor is the 1.4 um water feature observable from the ground for such faint objects due to telluric absorption, thus HST is the only telescope in the world suitable for these observations.

A HST/WFC3 Search for Substellar Companions in the Orion Nebula Cluster

NASA Astrophysics Data System (ADS)

Strampelli, Giovanni Maria; Aguilar, Jonathan; Aparicio, Antonio; Piotto, Giampaolo; Pueyo, Laurent; Robberto, Massimo

2018-01-01

We present new results relative to the population of substellar binaries in the Orion Nebula Cluster. We reprocessed HST/WFC3 data using an analysis technique developed to detect close companions in the wings of the stellar PSFs, based on the PyKLIP implementation of the KLIP PSF subtraction algorithm. Starting from a sample of ~1200 stars selected over the range J=11-15 mag, we were able to uncover ~80 candidate companions in the magnitude range J=16-23 mag. We use the presence of the 1.4 micron H2O absorption feature in the companion photosphere to discriminate 32 bona-fide substellar candidates from a population of reddened background objects. We derive an estimate of the companion mass assuming a 2Myr isochrone and the reddening of their primary. With 8 stellar companions, 19 brown dwarfs and 5 planetary mass objects, our study provide us with an unbiased sample of companions at the low-mass end of the IMF, probing the transition from binary to planetary systems.

The first H-band spectrum of the giant planet β Pictoris b

DOE PAGES

Chilcote, Jeffrey; Barman, Travis; Fitzgerald, Michael P.; ...

2014-12-12

Using the recently installed Gemini Planet Imager (GPI), we have obtained the first H-band spectrum of the planetary companion to the nearby young star β Pictoris. GPI is designed to image and provide low-resolution spectra of Jupiter-sized, self-luminous planetary companions around young nearby stars. These observations were taken covering the H band (1.65 μm). The spectrum has a resolving power of ~45 and demonstrates the distinctive triangular shape of a cool substellar object with low surface gravity. Using atmospheric models, we find an effective temperature of 1600-1700 K and a surface gravity of log (g) = 3.5-4.5 (cgs units). Thesemore » values agree well with "hot-start" predictions from planetary evolution models for a gas giant with mass between 10 and 12 M Jup and age between 10 and 20 Myr.« less

Low-mass Stellar and Substellar Companions to sdB Stars

NASA Astrophysics Data System (ADS)

Geier, S.; Classen, L.; Brünner, P.; Nagel, K.; Schaffenroth, V.; Heuser, C.; Heber, U.; Drechsel, H.; Edelmann, H.; Koen, C.; O'Toole, S. J.; Morales-Rueda, L.

2012-03-01

It has been suggested that besides stellar companions, substellar objects in close orbits may be able to trigger mass loss in a common envelope phase and form hot subdwarfs. In an ongoing project we search for close substellar companions combining time resolved high resolution spectroscopy with photometry. We determine the fraction of as yet undetected radial velocity variable systems from a sample of 27 apparently single sdB stars to be ˜eq16%. We discovered low-mass stellar companions to the He-sdB CPD-20circ 1123 and the pulsator KPD 0629-0016. The brown dwarf reported to orbit the eclipsing binary SDSS J0820+0008 could be confirmed by an analysis of high resolution spectra taken with UVES. Reflection effects have been detected in the light curves of the known sdB binaries CPD -64circ 481 and BPS CS 22169-0001. The inclinations of these systems must be much higher than expected and the most likely companion masses are in the substellar regime. Finally, we determined the orbit of the sdB binary PHL 457, which has a very small radial velocity amplitude and may host the lowest mass substellar companion known. The implications of these new results for the open question of sdB formation are discussed.

A Dual Power Law Distribution for the Stellar Initial Mass Function

NASA Astrophysics Data System (ADS)

Hoffmann, Karl Heinz; Essex, Christopher; Basu, Shantanu; Prehl, Janett

2018-05-01

We introduce a new dual power law (DPL) probability distribution function for the mass distribution of stellar and substellar objects at birth, otherwise known as the initial mass function (IMF). The model contains both deterministic and stochastic elements, and provides a unified framework within which to view the formation of brown dwarfs and stars resulting from an accretion process that starts from extremely low mass seeds. It does not depend upon a top down scenario of collapsing (Jeans) masses or an initial lognormal or otherwise IMF-like distribution of seed masses. Like the modified lognormal power law (MLP) distribution, the DPL distribution has a power law at the high mass end, as a result of exponential growth of mass coupled with equally likely stopping of accretion at any time interval. Unlike the MLP, a power law decay also appears at the low mass end of the IMF. This feature is closely connected to the accretion stopping probability rising from an initially low value up to a high value. This might be associated with physical effects of ejections sometimes (i.e., rarely) stopping accretion at early times followed by outflow driven accretion stopping at later times, with the transition happening at a critical time (therefore mass). Comparing the DPL to empirical data, the critical mass is close to the substellar mass limit, suggesting that the onset of nuclear fusion plays an important role in the subsequent accretion history of a young stellar object.

Observational diagnostics of accretion on young stars and brown dwarfs

NASA Astrophysics Data System (ADS)

Stelzer, Beate; Argiroffi, Costanza

I present a summary of recent observational constraints on the accretion properties of young stars and brown dwarfs with focus on the high-energy emission. In their T Tauri phase young stars assemble a few percent of their mass by accretion from a disk. Various observational signatures of disks around pre-main sequence stars and the ensuing accretion process are found in the IR and optical regime: e.g. excess emission above the stellar photosphere, strong and broad emission lines, optical veiling. At high energies evidence for accretion is less obvious, and the X-ray emission from stars has historically been ascribed to magnetically confined coronal plasmas. While being true for the bulk of the emission, new insight obtained from XMM-Newton and Chandra observations has unveiled contributions from accretion and outflow processes to the X-ray emission from young stars. Their smaller siblings, the brown dwarfs, have been shown to undergo a T Tauri phase on the basis of optical/IR observations of disks and measurements of accretion rates. Most re-cently, first evidence was found for X-rays produced by accretion in a young brown dwarf, complementing the suspected analogy between stars and substellar objects.

A CANDIDATE PLANETARY-MASS OBJECT WITH A PHOTOEVAPORATING DISK IN ORION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Min; Kim, Jinyoung Serena; Apai, Dániel

2016-12-20

In this work, we report the discovery of a candidate planetary-mass object with a photoevaporating protoplanetary disk, Proplyd 133-353, which is near the massive star θ {sup 1} Ori C at the center of the Orion Nebula Cluster (ONC). The object was known to have extended emission pointing away from θ {sup 1} Ori C, indicating ongoing external photoevaporation. Our near-infrared spectroscopic data and the location on the H–R diagram suggest that the central source of Proplyd 133-353 is substellar (∼M9.5) and has a mass probably less than 13 Jupiter mass and an age younger than 0.5 Myr. Proplyd 133-353more » shows a similar ratio of X-ray luminosity to stellar luminosity to other young stars in the ONC with a similar stellar luminosity and has a similar proper motion to the mean one of confirmed ONC members. We propose that Proplyd 133-353 formed in a very low-mass dusty cloud or an evaporating gas globule near θ {sup 1} Ori C as a second generation of star formation, which can explain both its young age and the presence of its disk.« less

Bright Localized Near-Infrared Emission at 1-4 AU in the AB Aurigae Disk Revealed by IOTA Closure Phases

NASA Astrophysics Data System (ADS)

Millan-Gabet, R.; Monnier, J. D.; Berger, J.-P.; Traub, W. A.; Schloerb, F. P.; Pedretti, E.; Benisty, M.; Carleton, N. P.; Haguenauer, P.; Kern, P.; Labeye, P.; Lacasse, M. G.; Malbet, F.; Perraut, K.; Pearlman, M.; Thureau, N.

2006-07-01

We report on the detection of localized off-center emission at 1-4 AU in the circumstellar environment of the young stellar object AB Aurigae. We used closure-phase measurements in the near-infrared that were made at the long-baseline interferometer IOTA, the first obtained on a young stellar object using this technique. When probing sub-AU scales, all closure phases are close to zero degrees, as expected given the previously determined size of the AB Aurigae inner-dust disk. However, a clear closure-phase signal of -3.5d +/- 0.5d is detected on one triangle containing relatively short baselines, requiring a high degree of non-point symmetry from emission at larger (AU-sized) scales in the disk. We have not identified any alternative explanation for these closure-phase results, and we demonstrate that a ``disk hot spot'' model can fit our data. We speculate that such detected asymmetric near-infrared emission might arise as a result of localized viscous heating due to a gravitational instability in the AB Aurigae disk, or to the presence of a close stellar companion or accreting substellar object.

Detection et caracterisation de naines brunes et exoplanetes avec un filtre accordable pour applications dans l'espace

NASA Astrophysics Data System (ADS)

Ingraham, Patrick Jon

This thesis determines the capability of detecting faint companions in the presence of speckle noise when performing space-based high-contrast imaging through spectral differential imagery (SDI) using a low-order Fabry-Perot etalon as a tunable filter. The performance of such a tunable filter is illustrated through the Tunable Filter Imager (TFI), an instrument designed for the James Webb Space Telescope (JWST). Using a TFI prototype etalon and a custom designed test bed, the etalon's ability to perform speckle-suppression through SDI is demonstrated experimentally. Improvements in contrast vary with separation, ranging from a factor of ˜10 at working angles greater than 11 lambda/D and increasing up to a factor of ˜60 at 5 lambda/D. These measurements are consistent with a Fresnel optical propagation model which shows the speckle suppression capability is limited by the test bed and not the etalon. This result demonstrates that a tunable filter is an attractive option to perform high-contrast imaging through SDI. To explore the capability of space-based SDI using an etalon, we perform an end-to-end Fresnel propagation of JWST and TFI. Using this simulation, a contrast improvement ranging from a factor of ˜7 to ˜100 is predicted, depending on the instrument's configuration. The performance of roll-subtraction is simulated and compared to that of SDI. The SDI capability of the Near-Infrared Imager and Slitless Spectrograph (NIRISS), the science instrument module to replace TFI in the JWST Fine Guidance Sensor is also determined. Using low resolution, multi-band (0.85-2.4 microm) multi-object spectroscopy, 104 objects towards the central region of the Orion Nebular Cluster have been assigned spectral types including 7 new brown dwarfs, and 4 new planetary mass candidates. These objects are useful for determining the substellar initial mass function and for testing evolutionary and atmospheric models of young stellar and substellar objects. Using the measured H band magnitudes, combined with our determined extinction values, the classified objects are used to create an Hertzsprung-Russell diagram for the cluster. Our results indicate a single epoch of star formation beginning ˜1 Myr ago. The initial mass function of the cluster is derived and found to be consistent with the values determined for other young clusters and the galactic disk.

Fundamental Parameters Of The Lowest Mass Stars To The Highest Mass Planets

NASA Astrophysics Data System (ADS)

Filippazzo, Joseph C.

2016-09-01

The physical and atmospheric properties of ultracool dwarfs are deeply entangled due to the degenerate effects of mass, age, metallicity, clouds and dust, activity, rotation, and possibly even formation mechanism on observed spectra. Accurate determination of funda- mental parameters for a wide diversity of objects at the low end of the initial mass function (IMF) is thus crucial to testing stellar and planetary formation theories. To determine these quantities, we constructed and flux calibrated nearly-complete spectral energy distributions (SEDs) for 234 M, L, T, and Y dwarfs using published parallaxes and (0.3-40 \\mu m) spectra and photometry. From these homogeneous SEDs, we calculated bolometric luminosity ((L_\\text{bol})), effective temperature ((T_\\text{off})), mass, surface gravity, radius, spectral indexes, synthetic photometry, and bolometric corrections (BCs) for each object. We used these results to derive (L_\\text{bol}), (T_\\text{eff}), and BC polynomial relations across the entire very-low-mass star/brown dwarf/planetary mass regime. We use a subsample of objects with age constraints based on nearby young moving group membership, companionship with a young star, or spectral signatures of low surface gravity to define new age-sensitive diagnostics and characterize the reddening of young substellar atmospheres as a redistribution of flux from the near-infrared (NIR) into the mid-infrared (MIR). Consequently we find the SED flux pivots at K-band, making BCK as a function of spectral type a reliable, age-independent relationship. We find that young L dwarfs are systematically 300 K cooler than field age objects of the same spectral type and up to 600 K cooler than field age objects of the same absolute H magnitude. These findings are used to create prescriptions for the reliable and efficient characterization of new ultracool dwarfs using heterogeneous and limited spectral data.

Why Compositional Convection Cannot Explain Substellar Objects’ Sharp Spectral-type Transitions

NASA Astrophysics Data System (ADS)

Leconte, Jérémy

2018-02-01

As brown dwarfs and young giant planets cool down, they are known to experience various chemical transitions—for example, from {CO} rich L-dwarfs to methane rich T-dwarfs. Those chemical transitions are accompanied by spectral transitions with sharpness that cannot be explained by chemistry alone. In a series of articles, Tremblin et al. proposed that some of the yet-unexplained features associated with these transitions could be explained by a reduction of the thermal gradient near the photosphere. To explain, in turn, this more isothermal profile, they invoke the presence of an instability analogous to fingering convection—compositional convection—triggered by the change in mean molecular weight of the gas due to the chemical transitions mentioned above. In this Letter, we use existing arguments to demonstrate that any turbulent transport, if present, would in fact increase the thermal gradient. This misinterpretation comes from the fact that turbulence mixes/homogenizes entropy (potential temperature) instead of temperature. So, while increasing transport, turbulence in an initially stratified atmosphere actually carries energy downward, whether it is due to fingering or any other type of compositional convection. These processes therefore cannot explain the features observed along the aforementioned transitions by reducing the thermal gradient in the atmosphere of substellar objects. Understanding the microphysical and dynamical properties of clouds at these transitions thus probably remains our best way forward.

The Unevenly Distributed Nearest Brown Dwarfs

NASA Astrophysics Data System (ADS)

Bihain, Gabriel; Scholz, Ralf-Dieter

2016-08-01

To address the questions of how many brown dwarfs there are in the Milky Way, how do these objects relate to star formation, and whether the brown dwarf formation rate was different in the past, the star-to-brown dwarf number ratio can be considered. While main sequence stars are well known components of the solar neighborhood, lower mass, substellar objects increasingly add to the census of the nearest objects. The sky projection of the known objects at <6.5 pc shows that stars present a uniform distribution and brown dwarfs a non-uniform distribution, with about four times more brown dwarfs behind than ahead of the Sun relative to the direction of rotation of the Galaxy. Assuming that substellar objects distribute uniformly, their observed configuration has a probability of 0.1 %. The helio- and geocentricity of the configuration suggests that it probably results from an observational bias, which if compensated for by future discoveries, would bring the star-to-brown dwarf ratio in agreement with the average ratio found in star forming regions.

New Evidence for a Substellar Luminosity Problem: Dynamical Mass for the Brown Dwarf Binary Gl 417BC

NASA Astrophysics Data System (ADS)

Dupuy, Trent J.; Liu, Michael C.; Ireland, Michael J.

2014-08-01

We present new evidence for a problem with cooling rates predicted by substellar evolutionary models that implies that model-derived masses in the literature for brown dwarfs and directly imaged planets may be too high. Based on our dynamical mass for Gl 417BC (L4.5+L6) and a gyrochronology system age from its young, solar-type host star, commonly used models predict luminosities 0.2-0.4 dex lower than we observe. This corroborates a similar luminosity-age discrepancy identified in our previous work on the L4+L4 binary HD 130948BC, which coincidentally has nearly identical component masses (≈50-55 M Jup) and age (≈800 Myr) as Gl 417BC. Such a luminosity offset would cause systematic errors of 15%-25% in model-derived masses at this age. After comparing different models, including cloudless models that should not be appropriate for mid-L dwarfs like Gl 417BC and HD 130948BC but actually match their luminosities better, we speculate the observed overluminosity could be caused by opacity holes (i.e., patchy clouds) in these objects. Moreover, from hybrid substellar evolutionary models that account for cloud disappearance, we infer the corresponding phase of overluminosity may extend from a few hundred million years up to a few gigayears and cause masses to be overestimated by up to 25%, even well after clouds disappear from view entirely. Thus, the range of ages and spectral types affected by this potential systematic shift in luminosity evolution would encompass most known directly imaged gas-giants and field brown dwarfs. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

A Pan-STARRS1 Proper-Motion Survey for Young Brown Dwarfs in the Nearest Star-Forming Regions and a Reddening-Free Classification Method for Ultracool Dwarfs

NASA Astrophysics Data System (ADS)

Zhang, Zhoujian; Liu, Michael C.; Best, William M. J.; Magnier, Eugene; Aller, Kimberly

2018-01-01

Young brown dwarfs are of prime importance to investigate the universality of the initial mass function (IMF). Based on photometry and proper motions from the Pan-STARRS1 (PS1) 3π survey, we are conducting the widest and deepest brown dwarf survey in the nearby star-forming regions, Taurus–Auriga (Taurus) and Upper Scorpius (USco). Our work is the first to measure proper motions, a robust proxy of membership, for brown dwarf candidates in Taurus and USco over such a large area and long time baseline (≈ 15 year) with such high precision (≈ 4 mas yr-1). Since extinction complicates spectral classification, we have developed a new approach to quantitatively determine reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (≈ 100–5 MJup), using low-resolution near-infrared spectra. So far, our IRTF/SpeX spectroscopic follow-up has increased the substellar and planetary-mass census of Taurus by ≈ 50% and almost doubled the substellar census of USco, constituting the largest single increases of brown dwarfs and free-floating planets found in both regions to date. Most notably, our new discoveries reveal an older (> 10 Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. In addition, the mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes. Upon completion, our survey will establish the most complete substellar and planetary-mass census in both Taurus and USco associations, make a significant addition to the low-mass IMF in both regions, and deliver more comprehensive pictures of star formation histories.

Update on ONC's Substellar IMF: A Second Peak in the Brown Dwarf Regime

NASA Astrophysics Data System (ADS)

Drass, Holger; Bayo, A.; Chini, R.; Haas, M.

2017-06-01

The Orion Nebular Cluster (ONC) has become the prototype cluster for studying the Initial Mass Function (IMF). In a deep JHK survey of the ONC with HAWK-I we detected a large population of 900 Brown Dwarfs and Planetary Mass Object candidates presenting a pronounced second peak in the substellar IMF. One of the most obvious issues of this result is the verification of cluster membership. The analysis so far was mainly based on statistical consideration. In this presentation I will show the results from using different high-resolution extinction map to determine the ONC membership.

Direct evidence of a sub-stellar companion around CT Chamaeleontis

NASA Astrophysics Data System (ADS)

Schmidt, T. O. B.; Neuhäuser, R.; Seifahrt, A.; Vogt, N.; Bedalov, A.; Helling, Ch.; Witte, S.; Hauschildt, P. H.

2008-11-01

Aims: In our ongoing search for close and faint companions around T Tauri stars in the Chamaeleon star-forming region, we here present observations of a new common proper motion companion to the young T-Tauri star and Chamaeleon member CT Cha and discuss its properties in comparison to other young, low-mass objects and to synthetic model spectra from different origins. Methods: Common proper motion of the companion and CT Cha was confirmed by direct Ks-band imaging data taken with the VLT Adaptive Optics (AO) instrument NACO in February 2006 and March 2007, together with a Hipparcos binary for astrometric calibration. An additional J-band image was taken in March 2007 to obtain color information for a first classification of the companion. Moreover, AO integral field spectroscopy with SINFONI in J, and H+K bands was obtained to deduce physical parameters of the companion, such as temperature and extinction. Relative flux calibration of the bands was achieved using photometry from the NACO imaging data. Results: We found a very faint (Ks = 14.9 mag, Ks0 = 14.4 mag) object, just ~2.67´´ northwest of CT Cha corresponding to a projected separation of ~440 AU at 165 ± 30 pc. We show that CT Cha A and this faint object form a common proper motion pair and that the companion is by ≥4σ significance not a stationary background object. The near-infrared spectroscopy yields a temperature of 2600 ± 250 K for the companion and an optical extinction of AV = 5.2 ± 0.8 mag, when compared to spectra calculated from Drift-Phoenix model atmospheres. We demonstrate the validity of the model fits by comparison to several other well-known young sub-stellar objects. Conclusions: We conclude that the CT Cha companion is a very low-mass member of Chamaeleon and very likely a physical companion to CT Cha, as the probability for a by chance alignment is ≤0.01. Due to a prominent Pa-β emission in the J-band, accretion is probably still ongoing onto the CT Cha companion. From temperature and luminosity (log(L_bol/L⊙) = -2.68 ± 0.21), we derive a radius of R = 2.20_-0.60+0.81 RJup. We find a consistent mass of M = 17 ± 6 MJup for the CT Cha companion from both its luminosity and temperature when placed on evolutionary tracks. Hence, the CT Cha companion is most likely a wide brown dwarf companion or possibly even a planetary mass object. Based on observations made with ESO telescopes at the Paranal Observatory under program IDs 076.C-0292(A), 078.C-0535(A), & 279.C-5010(A). Color versions of Figs. 4, 6, 8 and 11 are only available in electronic form at http://www.aanda.org

A Search for Water Maser Emission from Brown Dwarfs and Low-luminosity Young Stellar Objects

NASA Astrophysics Data System (ADS)

Gómez, José F.; Palau, Aina; Uscanga, Lucero; Manjarrez, Guillermo; Barrado, David

2017-05-01

We present a survey for water maser emission toward a sample of 44 low-luminosity young objects, comprising (proto-)brown dwarfs, first hydrostatic cores (FHCs), and other young stellar objects (YSOs) with bolometric luminosities lower than 0.4 L ⊙. Water maser emission is a good tracer of energetic processes, such as mass-loss and/or accretion, and is a useful tool to study these processes with very high angular resolution. This type of emission has been confirmed in objects with L bol ≳ 1 L ⊙. Objects with lower luminosities also undergo mass-loss and accretion, and thus, are prospective sites of maser emission. Our sensitive single-dish observations provided a single detection when pointing toward the FHC L1448 IRS 2E. However, follow-up interferometric observations showed water maser emission associated with the nearby YSO L1448 IRS 2 (a Class 0 protostar of L bol ≃ 3.6-5.3 L ⊙) and did not find any emission toward L1448 IRS 2E. The upper limits for water maser emission determined by our observations are one order of magnitude lower than expected from the correlation between water maser luminosities and bolometric luminosities found for YSOs. This suggests that this correlation does not hold at the lower end of the (sub)stellar mass spectrum. Possible reasons are that the slope of this correlation is steeper at L bol ≤ 1 L ⊙ or that there is an absolute luminosity threshold below which water maser emission cannot be produced. Alternatively, if the correlation still stands at low luminosity, the detection rates of masers would be significantly lower than the values obtained in higher-luminosity Class 0 protostars.

A Search for Pulsation in Young Brown Dwarfs and Very Low Mass Stars

NASA Astrophysics Data System (ADS)

Cody, Ann Marie

2012-05-01

In 2005, Palla and Baraffe proposed that brown dwarfs and very low mass stars (<0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated oscillation periods of 1--4 hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1--15 million year age range. Furthermore, several previous reports of short-period variability have suggested that deuterium-burning pulsation is in fact at work in young clusters. For my dissertation, I developed a photometric monitoring campaign to search for low-amplitude periodic variability in young brown dwarfs and very low mass stars using meter-class telescopes from both the ground and space. The resulting high-precision, high-cadence time-series photometry targeted four young clusters and achieved sensitivity to periodic oscillations with photometric amplitudes down to several millimagnitudes. This unprecedented variability census probed timescales ranging from minutes to weeks in a sample of 200 young, low-mass cluster members of IC 348, Sigma Orionis, Chamaeleon I, and Upper Scorpius. While I find a dearth of photometric periods under 10 hours, the campaign's high time resolution and precision have enabled detailed study of diverse light curve behavior in the clusters: rotational spot modulation, accretion signatures, and occultations by surrounding disk material. Analysis of the data has led to the establishment of a lower limit for the timescale of periodic photometric variability in young low-mass and substellar objects, an extension of the rotation period distribution to the brown dwarf regime, as well as insights into the connection between variability and circumstellar disks in the Sigma Orionis and Chamaeleon I clusters.

NEW EXTINCTION AND MASS ESTIMATES FROM OPTICAL PHOTOMETRY OF THE VERY LOW MASS BROWN DWARF COMPANION CT CHAMAELEONTIS B WITH THE MAGELLAN AO SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ya-Lin; Close, Laird M.; Males, Jared R.

We used the Magellan adaptive optics system and its VisAO CCD camera to image the young low mass 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 thatmore » 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.« less

New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System

NASA Astrophysics Data System (ADS)

Wu, Ya-Lin; Close, Laird M.; Males, Jared R.; Barman, Travis S.; Morzinski, Katie M.; Follette, Katherine B.; Bailey, Vanessa; Rodigas, Timothy J.; Hinz, Philip; Puglisi, Alfio; Xompero, Marco; Briguglio, Runa

2015-03-01

We used the Magellan adaptive optics system and its VisAO CCD camera to image the young low mass brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r', i', z', and YS . With our new photometry and T eff ~ 2500 K derived from the shape of its K-band spectrum, we find that CT Cha B has AV = 3.4 ± 1.1 mag, and a mass of 14-24 MJ 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 × 10-10 M ⊙ yr-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', YS ) allows for a better estimate of extinction, luminosity, and mass accretion rate of young substellar companions. This paper includes data gathered with the 6.5 m Magellan Clay Telescope at Las Campanas Observatory, Chile.

Banyan. X. Discovery of a Wide, Low-gravity L-type Companion to a Fast-rotating M3 Dwarf

NASA Astrophysics Data System (ADS)

Desrochers, Marie-Eve; Artigau, Étienne; Gagné, Jonathan; Doyon, René; Malo, Lison; Faherty, Jacqueline K.; Lafrenière, David

2018-01-01

We report the discovery of a substellar-mass co-moving companion to 2MASS J22501512+2325342, an M3 candidate member of the young (130–200 Myr) AB Doradus Moving Group (ABDMG). This L3 β companion was discovered in a 2MASS search for companions at separations of 3″–18″ from a list of 2812 stars suspected to be young (≲500 Myr) in the literature, and was confirmed with follow-up astrometry and spectroscopy. Evolutionary models yield a companion mass of {30}-4+11 {M}{Jup} at the age of ABDMG. The 2MASS J22501512+2325342 AB system appears to be a spatial outlier to the bulk of ABDMG members, similarly to the young 2MASS J22362452+4751425 AB system. Future searches for young objects around these two systems would make it possible to determine whether they are part of a spatial extension of the known ABDMG distribution. Based on observations obtained at the Canada–France–Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientique of France, and the University of Hawaii.

Low mass companions to nearby stars: Spectral classification and its relation to the stellar/substellar break

NASA Technical Reports Server (NTRS)

Kirkpatrick, J. Davy; Mccarthy, Donald W., Jr.

1994-01-01

The relationship between mass and spectral class for main-sequence stars has never been obtained for dwarfs cooler than M6; currently, the true nature of objects classified as M7, M8, M9, or later (be they stellar or substellar) is not known. In this paper, spectral types for the components in five low mass binary systems are estimated based on previously published infrared speckle measurements, red/infrared photometry, and parallax data, together with newly acquired high signal-to-noise composite spectra of the systems and revised magnitude difference relations for M dwarfs. For two of these binaries, the secondary has a smaller mass (less than 0.09 solar mass) than any object having a dynamically measured mass and a known spectral type, thus extending the spectral class/mass relation to lower masses than has previously been possible. Data from the higher mass components (0.09 solar mass less than M less than 0.40 solar mass) are consistent with earlier results; the two lowest mass objects -- though having mass errors which could place them on either side of the M dwarf/brown dwarf dividing line (Mass is about 0.08 solar mass) -- are found to have spectral types no cooler than M6.5 V. An extrapolation of the updated spectral class/mass relation to the hydrogen-burning limit suggests that objects of type M7 and later may be substellar. Direct confirmation of this awaits the discovery of a close, very late-type binary for which dynamical masses can be measured.

ALMA Measurements of Circumstellar Material in the GQ Lup System

NASA Astrophysics Data System (ADS)

Wilner, David J.; MacGregor, Meredith A.; Czekala, Ian; Andrews, Sean M.; Dai, Yu Sophia; Herczeg, Gregory; Kratter, Kaitlin M.; Kraus, Adam L.; Ricci, Luca; Testi, Leonardo

2017-01-01

We present ALMA observations of the GQ Lup system, a young Sun-like star with a substellar mass companion in a wide-separation orbit. These observations of 870 micron continuum and CO J=3-2 line emission with beam 0.3 arcsec (45 AU) resolve the disk of dust and gas surrounding the primary star, GQ Lup A, and provide deep limits on any circumplanetary disk surrounding the companion, GQ Lup b. The 3 sigma upper limit on the 870 micron flux density of < 0.15 mJy implies an upper limit on the GQ Lup b disk mass of about 0.04 solar masses for standard assumptions about optically thin dust emission. Given the non-detection of a circumplanetary disk around GQ Lup b, and other similar systems observed by ALMA, we discuss implications for formation mechanisms of wide-separation substellar companions.

VizieR Online Data Catalog: The Auriga-California molecular cloud (Broekhoven-Fiene+, 2014)

NASA Astrophysics Data System (ADS)

Broekhoven-Fiene, H.; Matthews, B. C.; Harvey, P. M.; Gutermuth, R. A.; Huard, T. L.; Tothill, N. F. H.; Nutter, D.; Bourke, T. L.; Difrancesco, J.; Jorgensen, J. K.; Allen, L. E.; Chapman, N. L.; Cieza, L. A.; Dunham, M. M.; Merin, B.; Miller, J. F.; Terebey, S.; Peterson, D. E.; Stapelfeldt, K. R.

2017-06-01

We have mapped a significant fraction of the AMC with the Infrared Array Camera (IRAC; Fazio et al. 2004ApJS..154...10F) and the Mid-Infrared Photometer for Spitzer (MIPS; Rieke et al. 2004ApJS..154...25R) on board the Spitzer Space Telescope (Werner et al. 2004ApJS..154....1W), with a total overlapping coverage of 2.5 deg2 in the four IRAC bands (3.6, 4.5, 5.8 and 8.0 um) and 10.47 deg2 in the three MIPS bands (24, 70, and 160 um). The mapped areas are not all contiguous and were chosen to include the areas with AV>3, as given by the Dobashi et al. (2005PASJ...57....1S) extinction maps. The goal of these observations is to identify and characterize the young stellar object (YSO) and substellar object populations. The data presented here are the first mid-IR census of the YSO population in this region. (4 data files).

Tracing Interactions of a Protoplanet with its Circumstellar Disk

NASA Astrophysics Data System (ADS)

Stapelfeldt, Karl

2017-08-01

A candidate companion to a very young star has been discovered in HST snapshot optical images. The object is projected at the outer radius of an edge-on protoplanetary disk and is aligned with the disk plane. Keck LGS photometry results indicate the object has the same temperature as brown dwarf GQ Lupi b but with 10x less luminosity - consistent with a planetary mass companion. Because the edge-on disk suppresses the light of the central star, the companion is uniquely accessible to follow-up studies with minimal starlight residuals. We propose HST/WFC3 imaging and spectroscopy of the system to 1) fully define the morphology of the disk scattered light, particularly at the disk outer edge near the companion; 2) search for Halpha emission from the companion as evidence that it is actively accreting; and 3) complete spectral characterization of the companion using G141 spectroscopy. Confirmation of a substellar spectrum, accretion, and disk interaction action would establish this object as a leading example of an accreting protoplanet at 100 AU and offer support to models for planet formation by gravitational instability.

Brown Dwarfs and Giant Planets Around Young Stars

NASA Astrophysics Data System (ADS)

Mahmud, Naved; Crockett, C.; Johns-Krull, C.; Prato, L.; Hartigan, P.; Jaffe, D.; Beichman, C.

2011-01-01

How dry is the brown dwarf (BD) desert at young ages? Previous radial velocity (RV) surveys have revealed that the frequency of BDs as close companions to solar-age stars in the field is extraordinarily low compared to the frequency of close planetary and stellar companions. Is this a formation or an evolutionary effect? Do close-in BDs form at lower rates, or are they destroyed by migration via interactions with a massive circumstellar disk, followed by assimilation into the parent star? To answer these questions, we are conducting an RV survey of 130 T Tauri stars in Taurus-Auriga (a few Myr old) and a dozen stars in the Pleiades (100 Myr old) to search for stellar reflex motions resulting from close substellar companions. Our goal is to measure the frequency of BDs at young ages. Detecting a higher frequency of BDs in young systems relative to the field will provide evidence for the migration theory as well as set limits on the migration timescale. Two additional goals are (1) to investigate the effect of star spots in young stars on RV observations, and (2) to detect the youngest-known giant exoplanet. We present results from the first few years of this survey. Strikingly, after completing observations of a third of our sample, we have yet to detect a single BD. Thus we can set limits on the dryness of the BD desert at young ages and shed light on the mysterious early lives of these objects.

The discovery of the peculiar L dwarf ULAS J222711-004547

NASA Astrophysics Data System (ADS)

Marocco, F.; Day-Jones, A. C.; Jones, H. R. A.; Pinfield, D. J.; Burningham, B.; Zhang, Z. H.

We present the discovery of a very peculiar L dwarf from the UKIDSS Large Area Survey (LAS), ULAS J222711-004547. Its very red infrared colours (MKO J-K = 2.79) make it the reddest brown dwarf discovered so far. The object was discovered as part of a large spectroscopic campaign aimed at constraining the sub-stellar birth rate. We obtained a moderate resolution spectrum of this target using the echelle spectrograph XSHOOTER on VLT/UT2, and classified it as L7pec, confirming its very red nature. We show that applying a simple de-reddening curve to the spectrum of ULAS J222711-004547, this becomes very similar to the spectrum of a L7 spectroscopic standard. Therefore we conclude that the reddening of the spectrum is mostly due to an excess of dust in the photosphere of the object. This new discovery joins the list of unusually red L dwarfs, whose nature is not yet fully understood, and poses a new important challenge to atmospheric modeling of substellar objects.

NTT Observations Indicate that Brown Dwarfs Form Like Stars

NASA Astrophysics Data System (ADS)

2001-06-01

Dusty Disks Detected around Very Young Substellar Objects in the Orion Nebula Summary An international team of astronomers [2] is announcing today the discovery of dusty disks surrounding numerous very faint objects that are believed to be recently formed Brown Dwarfs in the Orion Nebula [3]. This finding is based on detailed observations with SOFI, a specialised infrared-sensitive instrument at the ESO 3.5-m New Technology Telescope at the La Silla Observatory. It is of special interest because it sheds light on the origin and nature of substellar objects, known as "Brown Dwarfs" . In particular, these results suggest that Brown Dwarfs share a common origin with stars and that Brown Dwarfs are more similar in nature to stars than to planets and, like stars, have the potential to form with accompanying systems of planets. Moreover, the presence of dusty protoplanetary disks around the faintest objects in the Orion Nebula cluster confirms both the membership of these faint stars in the cluster and their nature as bona-fide substellar objects, making this the largest population of Brown Dwarf objects yet known . These important results are being reported today to the American Astronomical Society Meeting in Pasadena (California, USA). PR Photo 22a/01 : Infrared picture of the Orion Nebula (NTT + SOFI). PR Photo 22b/01 : "Finding Chart" for Very Young Brown Dwarfs in the Orion Nebula. PR Photo 22c/01 : Animated GIF presentation of PR Photos 22a+b/01. Faint substellar objects in the Milky Way Over the past 5 years, several groups of astronomers have identified a type of very faint, substellar objects within our Milky Way galaxy. These gaseous objects have very low masses and will never shine like normal stars because they cannot achieve central temperatures high enough for sustained thermal nuclear reactions to occur in their cores. Such objects weigh less than about 7% of our Sun and have been variously called "Brown Dwarfs" , "Failed Stars" or "Super Planets" . Indeed, since they have no sustained energy generation by thermal nuclear reactions, many of their properties are more similar to those of giant gas planets in our own solar system such as Jupiter, than to stars like the Sun. For example, even though their masses range between 10-70 times that of Jupiter (the largest and most massive planet in our solar system), the sizes of Brown Dwarfs are still comparable to that of Jupiter, approximately 140,000 km, or roughly 10 times smaller than the Sun. Are Brown Dwarfs giant planets or failed stars? Among the most fundamental issues raised by the existence of Brown Dwarfs is the question of their origin and genetic relationship to planets and stars. Are Brown Dwarfs giant planets or small, failed stars, or perhaps something completely different? The critical test needed to resolve this very basic question is to learn whether Brown Dwarfs form by a process similar to what produces stars or rather to one which produces planets. Stars are thought to form when gravity causes a cold, dusty and rarefied cloud of gas to contract. Such clouds are inevitably rotating so the gas naturally collapses into a rotating disk before it falls onto the forming star. These disks are called circumstellar or protoplanetary disks . They have been found around virtually all young stars and are considered to be sites of planet formation. Gravity helps planets form too, but this occurs by condensation and agglomeration of material contained in the circumstellar disk around a young star. Thus, stars form with a disk around them while planets form within disks around young stars . The planets in our own solar system were formed in such a circumstellar disk around the young Sun about 4.6 billion years ago. To date, the most important observations bearing on the question of Brown Dwarf origin have been: * the observed lack of Brown Dwarf companions to normal stars (something astronomers have called the "Brown Dwarf desert"), and * the existence of free-floating Brown Dwarfs in the Milky Way galaxy. Both facts would appear to imply a stellar, rather than a planet-like origin for these objects. However, one might also explain these observations if most Brown Dwarfs initially formed as companions to stars (within circumstellar disks), but were later ejected from the systems, e.g., because of gravitational effects during encounters with other stars. So the issue of Brown Dwarf origin is still unsettled. NTT observations of substellar objects in the Orion Nebula ESO PR Photo 22a/01 ESO PR Photo 22a/01 [Preview - JPEG: 400 x 434 pix - 192k] [Normal - JPEG: 800 x 877 pix - 496k] [Full Resolution - JPEG: 1772 x 1943 pix - 1.2Mb Caption : PR Photo 22a/01 shows a colour composite of near-infrared images of the central regions of the Orion Nebula, obtained on March 14, 2000, with the SOFI instrument at the ESO 3.5-m New Technology Telescope (NTT) at La Silla. Three exposures were made through J- (wavelength 1.25 µm here colour-coded as "blue"), H- (1.65 µm; "green") and Ks-filters (2.16 µm; "red"), respectively. The central group of bright stars is the famous "Trapezium" . The total effective exposure time was 86.4 seconds per band. The sky field measures about 4.9 x 4.9 arcmin 2 (1024 x 1024 pix 2 ). North is up and East is left. ESO PR Photo 22b/01 ESO PR Photo 22b/01 [Preview - JPEG: 400 x 439 pix - 35k] [Normal - JPEG: 800 x 877 pix - 90k] Caption : PR Photo 22b/01 contains the corresponding "finding chart" with the positions of the very young Brown Dwarfs in the Orion Nebula that were studied during the present investigation. The starlike symbols represent the brightest stars in PR Photo 22a/01 and are plotted for reference. In this chart, very young Brown Dwarfs are represented by a double open circle (if a dusty disk was detected) or with a single open circle (if no dusty disk was detected). The scale is exactly as in PR Photo 22a/01 . ESO PR Photo 22c/01 ESO PR Photo 22c/01 [Animated GIF: 482 x 465 pix - 248k] Caption : PR Photo 22c/01 is an animated GIF-composite of PR Photo 22a/01 and PR Photo 22b/01 for easy comparison. To resolve this mystery, an international team of astronomers [2] has obtained sensitive near-infrared observations of young Brown Dwarf candidates in the Trapezium cluster , at the centre of the Orion Nebula. For this, they used the state-of-the-art near-infrared SOFI instrument on the ESO 3.5-m New Technology Telescope (NTT) at the La Silla Observatory (Chile). The Trapezium Cluster is a group of young stars that appears to the unaided eye as a faint central 'star' in the Orion Nebula . This cluster is located at a distance of about 1200 light-years and contains nearly 1000 stars, most of which are younger than 1 million years. The stars in this cluster are in their infancy when compared to our middle-aged Sun that is about 4.6 billion years old (reduced to a human timescale, they would be just 3 days old, compared to the Sun's 40 years). Among the hundreds of normal stars in the Trapezium Cluster, astronomers have previously identified a population of objects so faint that they have been considered as prime candidates for very young Brown Dwarfs. The observations obtained with the NTT benefitted from superb atmospheric conditions (e.g., a seeing of 0.5 arcsec) and allowed the astronomers to examine the near-infrared light of more than 100 of the Brown Dwarf candidates in the cluster. More than half of them were found to have excess near-infrared light , compared to that a normal young Brown Dwarf should emit. The only plausible explanation is that this extra light originates from glowing, hot dust within protoplanetary disks surrounding these objects . It was the same method, albeit at longer infrared wavelengths, that first led to the discovery of dust disks around several normal stars, some of which have later been studied in much detail, e.g., that at the southern star Beta Pictoris. In fact, and strongly supporting this explanation, twenty-one of the Brown Dwarf candidates detected via the NTT observations are also identified with optical "proplyds" , the famous dusty disks first imaged in 1994 by the Hubble Space Telescope (HST) at optical wavelengths, cf. the corresponding HST Press Release and images [4]. Dusty disks The presence of such hot and dusty disks around these objects is a clear sign of their extreme youth - this in turn confirms both their membership in the young cluster and their nature as bona-fide substellar objects . Thus, the Trapezium Cluster contains the largest population (approximately 100) of Brown Dwarfs yet known. Indeed, only about 80 freely floating Brown Dwarfs have so far been positively identified outside this cluster. " Brown Dwarfs are considerably easier to detect and study when they are young, because they are ten times larger and thousands of times brighter during their early youth than during their middle age " says Elizabeth Lada from the University of Florida and a member of the team. Her colleague August Muench explains that " even at their brightest, however, most Brown Dwarfs are still 100 or more times intrinsically fainter than our Sun, explaining why astronomers have great difficulties in detecting such objects ". A common origin of normal stars and Brown Dwarfs " The high incidence of disks around both young stars and Brown Dwarfs in this cluster strongly suggests that both stars and Brown Dwarfs trace their origin to a common physical process and that Brown Dwarfs are more similar in nature to stars than to planets " says Charles Lada from the Smithsonian Astrophysical Observatory. Moreover, as is the case for stars, the disks that surround Brown Dwarfs may be capable of forming systems of planets. According to João Alves from ESO, " it is entirely possible that the Milky Way Galaxy contains numerous planetary systems that orbit cold and dark, failed stars. Whether these disks can indeed form planetary systems, however, still remains to be determined ". Even if Brown Dwarfs do have planetary systems, their planets would not have a stable climate and thus would be inhospitable to life as we know it. This is because Brown Dwarfs do not generate their own energy for any substantial period of time but instead fade rapidly as they age. The next steps For the moment being, the detection of disks around the Brown Dwarf candidates in the Trapezium Cluster rests entirely on the measurements of the near-infrared colours of these objects. Additional confirmation of the presence of such dust disks can be obtained with sensitive infrared observations made at longer wavelengths. Such observations are possible with the largest ground-based telescopes like the VLT [5] or with the upcoming NASA infrared satellite mission ( SIRTF ). Notes [1]: This ESO Press Release is issued in parallel with a Press Release on the same subject by the American Astronomical Society (AAS). The indicated embargo corresponds to the time of release at the AAS meting in Pasadena. [2]: The team consists of João F. Alves (ESO, Garching, Germany), Charles J. Lada (Smithsonian Astrophysical Observatory, Cambridge MA, USA), Elizabeth A. Lada and August A. Muench (both Department of Astronomy, University of Florida, Gainesville FL, USA). The research reported here was supported in part by the US National Science Foundation. [3]: Other ESO Press Communications about Brown Dwarfs include PR 07/97 , PR 14/99 and PR 16/00. Discoveries of exoplanets and other small objects, some of which have masses near the borderline between Brown Dwarfs and planets, are reported in PR 18/98 , PR 13/00 and PR 07/01. A spectacular infrared image of the Orion Nebula with the VLT and the ISAAC instrument was published earlier this year ( PR Photo 03a/01 ) with a discussion about small objects within this nebula. [4]: More information about "proplyds" (PROto-PLanetarY DiskS) is available in ESO PR 06/97 that discusses the discovery of the first such object outside the Orion Nebula. [5]: The VLT is already equipped with one instrument suited for such measurements, the Infrared Spectrometer And Array Camera (ISAAC) - examples of mid-infrared observations of the giant planet Jupiter have just been published as ESO PR Photos 21a-f/01. The NAOS-CONICA adaptive optics multi-mode instrument will enter into operation later in 2001, to be followed by the VLT Mid Infrared Spectrometer/Imager (VISIR). Another powerful mid-infrared facility at ESO is the Thermal Infrared Multimode Instrument (TIMMI2) , now in operation at the ESO 3.6-m telescope on La Silla and with which observations of the central part of the Orion Nebula were recently made, cf. PR Photos 12a-e/01.

THE EXTREMELY RED, YOUNG L DWARF PSO J318.5338–22.8603: A FREE-FLOATING PLANETARY-MASS ANALOG TO DIRECTLY IMAGED YOUNG GAS-GIANT PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Michael C.; Magnier, Eugene A.; Kotson, Michael C.

2013-11-10

We have discovered using Pan-STARRS1 an extremely red late-L dwarf, which has (J – K){sub MKO} = 2.78 and (J – K){sub 2MASS} = 2.84, making it the reddest known field dwarf and second only to 2MASS J1207–39b among substellar companions. Near-IR spectroscopy shows a spectral type of L7 ± 1 and reveals a triangular H-band continuum and weak alkali (K I and Na I) lines, hallmarks of low surface gravity. Near-IR astrometry from the Hawaii Infrared Parallax Program gives a distance of 24.6 ± 1.4 pc and indicates a much fainter J-band absolute magnitude than field L dwarfs. Themore » position and kinematics of PSO J318.5–22 point to membership in the β Pic moving group. Evolutionary models give a temperature of 1160{sup +30}{sub -40} K and a mass of 6.5{sup +1.3}{sub -1.0} M {sub Jup}, making PSO J318.5–22 one of the lowest mass free-floating objects in the solar neighborhood. This object adds to the growing list of low-gravity field L dwarfs and is the first to be strongly deficient in methane relative to its estimated temperature. Comparing their spectra suggests that young L dwarfs with similar ages and temperatures can have different spectral signatures of youth. For the two objects with well constrained ages (PSO J318.5–22 and 2MASS J0355+11), we find their temperatures are ≈400 K cooler than field objects of similar spectral type but their luminosities are similar, i.e., these young L dwarfs are very red and unusually cool but not 'underluminous'. Altogether, PSO J318.5–22 is the first free-floating object with the colors, magnitudes, spectrum, luminosity, and mass that overlap the young dusty planets around HR 8799 and 2MASS J1207–39.« less

The occurrence of planets and other substellar bodies around white dwarfs using K2

NASA Astrophysics Data System (ADS)

van Sluijs, L.; Van Eylen, V.

2018-03-01

The majority of stars both host planetary systems and evolve into a white dwarf (WD). To understand their post-main-sequence planetary system evolution, we present a search for transiting/eclipsing planets and other substellar bodies (SBs) around WDs using a sample of 1148 WDs observed by K2. Using transit injections, we estimate the completeness of our search. We place constraints on the occurrence of planets and SBs around WDs as a function of planet radius and orbital period. For short-period (P < 40 d) small objects, from asteroid-sized to 1.5 R⊕, these are the strongest constraints known to date. We further constrain the occurrence of hot Jupiters ( < 1.5 per cent), habitable zone Earth-sized planets ( < 28 per cent), and disintegrating short-period planets ( ˜ 12 per cent). We blindly recovered all previously known eclipsing objects, providing confidence in our analysis, and make all light curves publicly available.

Primeval very low-mass stars and brown dwarfs - II. The most metal-poor substellar object

NASA Astrophysics Data System (ADS)

Zhang, Z. H.; Homeier, D.; Pinfield, D. J.; Lodieu, N.; Jones, H. R. A.; Allard, F.; Pavlenko, Ya. V.

2017-06-01

SDSS J010448.46+153501.8 has previously been classified as an sdM9.5 subdwarf. However, its very blue J - K colour (-0.15 ± 0.17) suggests a much lower metallicity compared to normal sdM9.5 subdwarfs. Here, we re-classify this object as a usdL1.5 subdwarf based on a new optical and near-infrared spectrum obtained with X-shooter on the Very Large Telescope. Spectral fitting with BT-Settl models leads to Teff = 2450 ± 150 K, [Fe/H] = -2.4 ± 0.2 and log g = 5.5 ± 0.25. We estimate a mass for SDSS J010448.46+153501.8 of 0.086 ± 0.0015 M⊙ which is just below the hydrogen-burning minimum mass at [Fe/H] = -2.4 (˜0.088 M⊙) according to evolutionary models. Our analysis thus shows SDSS J010448.46+153501.8 to be the most metal-poor and highest mass substellar object known to-date. We found that SDSS J010448.46+153501.8 is joined by another five known L subdwarfs (2MASS J05325346+8246465, 2MASS J06164006-6407194, SDSS J125637.16-022452.2, ULAS J151913.03-000030.0 and 2MASS J16262034+3925190) in a 'halo brown dwarf transition zone' in the Teff-[Fe/H] plane, which represents a narrow mass range in which unsteady nuclear fusion occurs. This halo brown dwarf transition zone forms a 'substellar subdwarf gap' for mid L to early T types.

Mapping the Shores of the Brown Dwarf Desert. III. Young Moving Groups

NASA Astrophysics Data System (ADS)

Evans, T. M.; Ireland, M. J.; Kraus, A. L.; Martinache, F.; Stewart, P.; Tuthill, P. G.; Lacour, S.; Carpenter, J. M.; Hillenbrand, L. A.

2012-01-01

We present the results of an aperture-masking interferometry survey for substellar companions around 67 members of the young (~8-200 Myr) nearby (~5-86 pc) AB Doradus, β Pictoris, Hercules-Lyra, TW Hya, and Tucana-Horologium stellar associations. Observations were made at near-infrared wavelengths between 1.2 and 3.8 μm using the adaptive optics facilities of the Keck II, Very Large Telescope UT4, and Palomar Hale Telescopes. Typical contrast ratios of ~100-200 were achieved at angular separations between ~40 and 320 mas, with our survey being 100% complete for companions with masses below ~0.25 M ⊙ across this range. We report the discovery of a 0.52 ± 0.09 M ⊙ companion to HIP 14807, as well as the detections and orbits of previously known stellar companions to HD 16760, HD 113449, and HD 160934. We show that the companion to HD 16760 is in a face-on orbit, resulting in an upward revision of its mass from M 2sin i ~ 14 M J to M 2 = 0.28 ± 0.04 M ⊙. No substellar companions were detected around any of our sample members, despite our ability to detect companions with masses below 80 M J for 50 of our targets: of these, our sensitivity extended down to 40 M J around 30 targets, with a subset of 22 subject to the still more stringent limit of 20 M J. A statistical analysis of our non-detection of substellar companions allows us to place constraints on their frequency around ~0.2-1.5 M ⊙ stars. In particular, considering companion mass distributions that have been proposed in the literature, we obtain an upper limit estimate of ~9%-11% for the frequency of 20-80 M J companions between 3 and 30 AU at 95% confidence, assuming that their semimajor axes are distributed according to d {N}/da \\propto a^{-1} in this range.

SOAR Adaptive Optics Observations of Young Stellar Objects

NASA Astrophysics Data System (ADS)

Briceno, Cesar

2018-01-01

I present results from recent studies of nearby star-forming regions using the SOAR 4.1m telescope Ground-layer Adaptive Optics system.Using narrow-band Hα and [SII] imaging we discovered a spectacular extended Herbig-Haro jet powered by a 26 MJup young brown dwarf located in the vicinity of the σ Orionis cluster. The collimated structure of multiple knots spans 0.26 pc, making it a scaled down version of the parsec-length jets seen in T Tauri stars, and the first substellar analog of an HH jet system.In the ε Chamaeleon stellar group we carried out an Adaptive Optics-aided speckle imaging study of 47 members and candidate members, to characterize the multiplicity of this, one of the nearest groups of young (~3-5 Myr) stars. We resolved 10 new binary pairs, 5 previously know binaries and two triple systems. We find a companion frequency of 0.010±0.04 per decade of separation, in the 4 to 300 AU separation range, a result comparable to main sequence dwarfs in the field. However, the more massive association members, with B and A spectral types, all have companions in this separation range. Finally, we provide new constraints on the orbital elements of the ε Cha triple system.

Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive

NASA Astrophysics Data System (ADS)

Pueyo, Laurent

2013-10-01

We propose to conduct WFC3 high contrast observations of six faint planetary candidates orbiting young {1 to 100 Myrs} stars identified in archival HST NICMOS coronagraphic data as part of our team's program AR-12652. Such rare objects are of the utmost importance to comparative exo-planetology as their physical properties reflect the initial conditions of still poorly constrained planetary formation mechanisms. Moreover directly imaged systems are precious artifacts in the expanding exo-planetary treasure trove as they are readily available for spectroscopic characterization. Our statistical analysis, which combines population synthesis models and empirical inspections of the entire NICMOS field of view for all sources observed in coronaraphic mode, almost guarantees that one of these six faint candidates is associated with its putative host star. We will conduct our observation in four near infrared filter, F125W, F160W to establish the baseline luminosity of our candidates and in F127M and F139M in order to probe the depth their water absorption features, characteristic of substellar /exo-planetary like atmospheres. Because of the youth of our targets, this program, which only requires a modest 12 HST orbits, will almost certainly identify and image a young or adolescent exo-planet.

A possible brown dwarf companion to Gliese 569

NASA Technical Reports Server (NTRS)

Forrest, W. J.; Shure, Mark; Skrutskie, M. F.

1988-01-01

A faint cool companion to Gliese 569, discovered during an IR imaging survey of nearby stars, may be the lowest-mass stellar object yet found. The companion is somewhat cooler in its 1.65-3.75-micron energy distribution than the coolest known main-sequence stars, indicating a low mass. Despite its lower temperature, it is more luminous than similar extremely low-mass stars, suggesting that it is either a young low-mass star evolving toward the main sequence or a cooling substellar brown dwarf. The primary star has emission lines and a low space velocity and exhibits flaring, all of which imply youth for this system. Observations of Gliese 569 and its companion over a period of 2 yr confirm the common proper motion expected of a true binary. The 5-arcsec apparent separation (50 AU) implies an orbital period of roughly 500 yr, which will permit an eventual direct determination of the mass of the companion.

Baryonic dark matter

NASA Technical Reports Server (NTRS)

Silk, Joseph

1991-01-01

Both canonical primordial nucleosynthesis constraints and large-scale structure measurements, as well as observations of the fundamental cosmological parameters, appear to be consistent with the hypothesis that the universe predominantly consists of baryonic dark matter (BDM). The arguments for BDM to consist of compact objects that are either stellar relics or substellar objects are reviewed. Several techniques for searching for halo BDM are described.

The First Brown Dwarf/Planetary-mass Object in the 32 Orionis Group

NASA Astrophysics Data System (ADS)

Burgasser, Adam J.; Lopez, Mike A.; Mamajek, Eric E.; Gagné, Jonathan; Faherty, Jacqueline K.; Tallis, Melisa; Choban, Caleb; Tamiya, Tomoki; Escala, Ivanna; Aganze, Christian

2016-03-01

The 32 Orionis group is a co-moving group of roughly 20 young (24 Myr) M3-B5 stars 100 pc from the Sun. Here we report the discovery of its first substellar member, WISE J052857.69+090104.2. This source was previously reported to be an M giant star based on its unusual near-infrared spectrum and lack of measureable proper motion. We re-analyze previous data and new moderate-resolution spectroscopy from Magellan/Folded-port InfraRed Echellette to demonstrate that this source is a young near-infrared L1 brown dwarf with very low surface gravity features. Spectral model fits indicate Teff = 1880{}-70+150 K and {log}g = 3.8{}-0.2+0.2, consistent with a 15-22 Myr object with a mass near the deuterium-burning limit. Its sky position, estimated distance, kinematics (both proper motion and radial velocity), and spectral characteristics are all consistent with membership in 32 Orionis, and its temperature and age imply a mass (M = {14}-3+4 MJ) that straddles the brown dwarf/planetary-mass object boundary. The source has a somewhat red J-W2 color compared to other L1 dwarfs, but this is likely a low-gravity-related temperature offset; we find no evidence of significant excess reddening from a disk or cool companion in the 3-5 μm waveband. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

The Low-mass Population in the Young Cluster Stock 8: Stellar Properties and Initial Mass Function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jose, Jessy; Herczeg, Gregory J.; Fang, Qiliang

The evolution of H ii regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution, and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6 and 4.5 μ m photometry from UKIDSS and Spitzer -IRAC. We use multicolor criteria to identify the candidate young stellar objects in the region. Using evolutionary models,more » we obtain a median log(age) of ∼6.5 (∼3.0 Myr) with an observed age spread of ∼0.25 dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of ∼0.15 dex. The intrinsic age spread in the cluster is ∼0.2 dex. The fraction of young stellar objects surrounded by disks is ∼35%. The K -band luminosity function of Stock 8 is similar to that of the Trapezium cluster. The initial mass function (IMF) of Stock 8 has a Salpeter-like slope at >0.5 M {sub ⊙} and flattens and peaks at ∼0.4 M {sub ⊙}, below which it declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of the IMF due to the proximity of massive stars around the cluster.« less

Digging for substellar objects in the stellar graveyard

NASA Astrophysics Data System (ADS)

Debes, John H., IV

2005-11-01

White dwarfs, the endpoint of stellar evolution for stars with mass < 8 [Special characters omitted.] , possess several attributes favorable for studying planet and brown dwarf formation around stars with primordial masses 1 [Special characters omitted.] . This thesis explores the consequences of post-main-sequence evolution on the dynamics of a planetary system and the observational signatures that arise from such evolution. These signatures are then specifically tested with a direct imaging survey of nearby white dwarfs. Finally, new techniques for high contrast imaging are discussed and placed in the context of further searches for planets and brown dwarfs in the stellar graveyard. While planets closer than ~ 5 AU will most likely not survive the post-main sequence evolution of its parent star, any planet with semimajor axis > 5 AU will survive, and its semimajor axis will increase as the central star loses mass. The stability of adjacent orbits to mutual planet-planet perturbations depends on the ratio of the planet mass to the central star's mass, and I demonstrate that some planets in previously stable orbits around a star undergoing mass loss will become unstable. If pollution of a white dwarf's atmosphere is caused by relic planetary systems, any white dwarf with photospheric absorption due to metals can be searched for substellar companions. Hydrogen white dwarfs with metal absorption, so called DAZ white dwarfs, are hard to explain by simple ISM accretion, and present an opportunity to test the observational signatures of unstable planetary systems. Additionally, field white dwarfs can be searched for substellar companions as well. The search for planetary companions to stars requires further development of high contrast imaging techniques. This thesis studies Gaussian aperture pupil masks (GAPMs) which in theory can achieve the contrast requisite for directly imaging an extrasolar planet around a nearby solar type star. I outline the process of designing, fabricating, and testing a GAPM for use on current telescopes and specifically the Penn State near-IR Imager and Spectrograph (PIRIS) at the Mt. Wilson 100" telescope. I find that observations with a prototype are quite successful, achieving a contrast similar to a traditional Lyot coronagraph without blocking any light from a central object and useful for finding faint companions to nearby young solar analogues. In the lab I can reproduce the expected PSF reasonably well and with a single aperture design which achieves ~ 4 x 10 -5 contrast at 10l/ D . I find that small inaccuracies in the mask fabrication process and insufficient correction of the atmosphere contribute the most degradation to contrast at these levels. (Abstract shortened by UMI.)

A Search for Water Maser Emission from Brown Dwarfs and Low-luminosity Young Stellar Objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gómez, José F.; Manjarrez, Guillermo; Palau, Aina

We present a survey for water maser emission toward a sample of 44 low-luminosity young objects, comprising (proto-)brown dwarfs, first hydrostatic cores (FHCs), and other young stellar objects (YSOs) with bolometric luminosities lower than 0.4 L {sub ⊙}. Water maser emission is a good tracer of energetic processes, such as mass-loss and/or accretion, and is a useful tool to study these processes with very high angular resolution. This type of emission has been confirmed in objects with L {sub bol} ≳ 1 L {sub ⊙}. Objects with lower luminosities also undergo mass-loss and accretion, and thus, are prospective sites of maser emission.more » Our sensitive single-dish observations provided a single detection when pointing toward the FHC L1448 IRS 2E. However, follow-up interferometric observations showed water maser emission associated with the nearby YSO L1448 IRS 2 (a Class 0 protostar of L {sub bol} ≃ 3.6–5.3 L {sub ⊙}) and did not find any emission toward L1448 IRS 2E. The upper limits for water maser emission determined by our observations are one order of magnitude lower than expected from the correlation between water maser luminosities and bolometric luminosities found for YSOs. This suggests that this correlation does not hold at the lower end of the (sub)stellar mass spectrum. Possible reasons are that the slope of this correlation is steeper at L {sub bol} ≤ 1 L {sub ⊙} or that there is an absolute luminosity threshold below which water maser emission cannot be produced. Alternatively, if the correlation still stands at low luminosity, the detection rates of masers would be significantly lower than the values obtained in higher-luminosity Class 0 protostars.« less

Convective dynamics and chemical disequilibrium in the atmospheres of substellar objects

NASA Astrophysics Data System (ADS)

Bordwell, Baylee; Brown, Benjamin P.; Oishi, Jeffrey S.

2017-11-01

The thousands of substellar objects now known provide a unique opportunity to test our understanding of atmospheric dynamics across a range of environments. The chemical timescales of certain species transition from being much shorter than the dynamical timescales to being much longer than them at a point in the atmosphere known as the quench point. This transition leads to a state of dynamical disequilibrium, the effects of which can be used to probe the atmospheric dynamics of these objects. Unfortunately, due to computational constraints, models that inform the interpretation of these observations are run at dynamical parameters which are far from realistic values. In this study, we explore the behavior of a disequilibrium chemical process with increasingly realistic planetary conditions, to quantify the effects of the approximations used in current models. We simulate convection in 2-D, plane-parallel, polytropically-stratified atmospheres, into which we add reactive passive tracers that explore disequilibrium behavior. We find that as we increase the Rayleigh number, and thus achieve more realistic planetary conditions, the behavior of these tracers does not conform to the classical predictions of disequilibrium chemistry.

New spectro-photometric characterization of the substellar object HR 2562 B using SPHERE

NASA Astrophysics Data System (ADS)

Mesa, D.; Baudino, J.-L.; Charnay, B.; D'Orazi, V.; Desidera, S.; Boccaletti, A.; Gratton, R.; Bonnefoy, M.; Delorme, P.; Langlois, M.; Vigan, A.; Zurlo, A.; Maire, A.-L.; Janson, M.; Antichi, J.; Baruffolo, A.; Bruno, P.; Cascone, E.; Chauvin, G.; Claudi, R. U.; De Caprio, V.; Fantinel, D.; Farisato, G.; Feldt, M.; Giro, E.; Hagelberg, J.; Incorvaia, S.; Lagadec, E.; Lagrange, A.-M.; Lazzoni, C.; Lessio, L.; Salasnich, B.; Scuderi, S.; Sissa, E.; Turatto, M.

2018-05-01

Aims: HR 2562 is an F5V star located at 33 pc from the Sun hosting a substellar companion that was discovered using the Gemini planet imager (GPI) instrument. The main objective of the present paper is to provide an extensive characterization of the substellar companion, by deriving its fundamental properties. Methods: We observed HR 2562 with the near-infrared branch composed by the integral field spectrograph (IFS) and the infrared dual band spectrograph (IRDIS) of the spectro-polarimetric high-contrast exoplanet research (SPHERE) instrument at the very large telescope (VLT). During our observations IFS was operating in the Y J band, while IRDIS was observing with the H broadband filter. The data were reduced with the dedicated SPHERE GTO pipeline, which is custom designed for this instrument. On the reduced images, we then applied the post-processing procedures that are specifically prepared to subtract the speckle noise. Results: The companion is clearly detected in both IRDIS and IFS datasets. We obtained photometry in three different spectral bands. The comparison with template spectra allowed us to derive a spectral type of T2-T3 for the companion. Using both evolutionary and atmospheric models we inferred the main physical parameters of the companion obtaining a mass of 32 ± 14 MJup, Teff = 1100 ± 200 K, and log g = 4.75 ± 0.41. Based on observations made with European Southern Observatory (ESO) telescopes at Paranal Observatory in Chile, under program ID 198.C-0209(D).

Looking for the Coldest Atmospheres: a Search for Planetary Mass Companions around T and Y Brown Dwarfs

NASA Astrophysics Data System (ADS)

Fontanive, Clemence

2017-08-01

We propose to obtain WFC3/IR imaging of the very coolest brown dwarfs (T < 800 K) to search for substellar and planetary-mass companions to these objects. Companions discovered by this program would likely be analogues of the 250 K brown dwarf WISE 0855 and would provide vital benchmark objects for theoretical models, closing the gap in mass and temperature between brown dwarfs and planets. Finding such an object as a member of a binary system would be even more valuable as it would allow for the measurement of dynamical masses. We recently placed the first constraints to date on the binary frequency for brown dwarfs with spectral types >T8. This program will triple our current sample size, a requirement in order to confirm our current results and compare substellar binary properties for various spectral type and age populations. The WFC3/IR plate will allow us to probe near equal-mass binaries down to separations of 0.2 (2-3 AU for the typical distances of our targets). True cool companions should show strong absorption around 1.4 um as a result of the deep water absorption band observed at that wavelength in substellar spectra. We therefore propose observations in the WFC3 F127M and F139M filters which will allow us to robustly identify bona fide candidates and distinguish them from background stars based on this spectral feature. Most of our targets lack suitable NGS AO guide stars or LGS AO tip-tilt stars to be observed with ground-based telescopes, and the 1.4 um water band is often unobservable from the ground due to telluric water absorption. WFC3 on HST is thus the only instrument suitable for these observations.

Spectroscopic characterization of HD 95086 b with the Gemini Planet Imager

DOE PAGES

De Rosa, Robert J.; Rameau, Julien; Patience, Jenny; ...

2016-06-21

Here, we present new H (1.5–1.8 μm) photometric and K 1 (1.9–2.2 μm) spectroscopic observations of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager. The H-band magnitude has been significantly improved relative to previous measurements, whereas the low-resolution K 1 (more » $$\\lambda /\\delta \\lambda \\approx 66$$) spectrum is featureless within the measurement uncertainties and presents a monotonically increasing pseudo-continuum consistent with a cloudy atmosphere. By combining these new measurements with literature $$L^{\\prime} $$ photometry, we compare the spectral energy distribution (SED) of the planet to other young planetary-mass companions, field brown dwarfs, and to the predictions of grids of model atmospheres. HD 95086 b is over a magnitude redder in $${K}_{1}-L^{\\prime} $$ color than 2MASS J12073346–3932539 b and HR 8799 c and d, despite having a similar $$L^{\\prime} $$ magnitude. Considering only the near-infrared measurements, HD 95086 b is most analogous to the brown dwarfs 2MASS J2244316+204343 and 2MASS J21481633+4003594, both of which are thought to have dusty atmospheres. Morphologically, the SED of HD 95086 b is best fit by low temperature ($${T}_{{\\rm{eff}}}$$ = 800–1300 K), low surface gravity spectra from models which simulate high photospheric dust content. This range of effective temperatures is consistent with field L/T transition objects, but the spectral type of HD 95086 b is poorly constrained between early L and late T due to its unusual position the color–magnitude diagram, demonstrating the difficulty in spectral typing young, low surface gravity substellar objects. As one of the reddest such objects, HD 95086 b represents an important empirical benchmark against which our current understanding of the atmospheric properties of young extrasolar planets can be tested.« less

Galactic Stellar and Substellar Initial Mass Function

NASA Astrophysics Data System (ADS)

Chabrier, Gilles

2003-07-01

We review recent determinations of the present-day mass function (PDMF) and initial mass function (IMF) in various components of the Galaxy-disk, spheroid, young, and globular clusters-and in conditions characteristic of early star formation. As a general feature, the IMF is found to depend weakly on the environment and to be well described by a power-law form for m>~1 Msolar and a lognormal form below, except possibly for early star formation conditions. The disk IMF for single objects has a characteristic mass around mc~0.08 Msolar and a variance in logarithmic mass σ~0.7, whereas the IMF for multiple systems has mc~0.2 Msolar and σ~0.6. The extension of the single MF into the brown dwarf regime is in good agreement with present estimates of L- and T-dwarf densities and yields a disk brown dwarf number density comparable to the stellar one, nBD~n*~0.1 pc-3. The IMF of young clusters is found to be consistent with the disk field IMF, providing the same correction for unresolved binaries, confirming the fact that young star clusters and disk field stars represent the same stellar population. Dynamical effects, yielding depletion of the lowest mass objects, are found to become consequential for ages >~130 Myr. The spheroid IMF relies on much less robust grounds. The large metallicity spread in the local subdwarf photometric sample, in particular, remains puzzling. Recent observations suggest that there is a continuous kinematic shear between the thick-disk population, present in local samples, and the genuine spheroid one. This enables us to derive only an upper limit for the spheroid mass density and IMF. Within all the uncertainties, the latter is found to be similar to the one derived for globular clusters and is well represented also by a lognormal form with a characteristic mass slightly larger than for the disk, mc~0.2-0.3 Msolar, excluding a significant population of brown dwarfs in globular clusters and in the spheroid. The IMF characteristic of early star formation at large redshift remains undetermined, but different observational constraints suggest that it does not extend below ~1 Msolar. These results suggest a characteristic mass for star formation that decreases with time, from conditions prevailing at large redshift to conditions characteristic of the spheroid (or thick disk) to present-day conditions. These conclusions, however, remain speculative, given the large uncertainties in the spheroid and early star IMF determinations. These IMFs allow a reasonably robust determination of the Galactic present-day and initial stellar and brown dwarf contents. They also have important galactic implications beyond the Milky Way in yielding more accurate mass-to-light ratio determinations. The mass-to-light ratios obtained with the disk and the spheroid IMF yield values 1.8-1.4 times smaller than for a Salpeter IMF, respectively, in agreement with various recent dynamical determinations. This general IMF determination is examined in the context of star formation theory. None of the theories based on a Jeans-type mechanism, where fragmentation is due only to gravity, can fulfill all the observational constraints on star formation and predict a large number of substellar objects. On the other hand, recent numerical simulations of compressible turbulence, in particular in super-Alfvénic conditions, seem to reproduce both qualitatively and quantitatively the stellar and substellar IMF and thus provide an appealing theoretical foundation. In this picture, star formation is induced by the dissipation of large-scale turbulence to smaller scales through radiative MHD shocks, producing filamentary structures. These shocks produce local nonequilibrium structures with large density contrasts, which collapse eventually in gravitationally bound objects under the combined influence of turbulence and gravity. The concept of a single Jeans mass is replaced by a distribution of local Jeans masses, representative of the lognormal probability density function of the turbulent gas. Objects below the mean thermal Jeans mass still have a possibility to collapse, although with a decreasing probability. The page charges for this Review were partially covered by a generous gift from a PASP supporter.

Constraining Substellar Magnetic Dynamos using Brown Dwarf Radio Aurorae

NASA Astrophysics Data System (ADS)

Kao, Melodie Minyu

Brown dwarfs share characteristics with both low-mass stars and gas giant planets, making them useful laboratories for studying physics occurring in objects throughout this low mass and temperature range. Of particular interest in this dissertation is the nature of the engine driving their magnetic fields. Fully convective magnetic dynamos can operate in low mass stars, brown dwarfs, gas giant planets, and even fluid metal cores in small rocky planets. Objects in this wide mass range are capable of hosting strong magnetic fields, which shape much of the evolution of planets and stars: strong fields can protect planetary atmospheres from evaporating, generate optical and infrared emission that masquerade as clouds in the atmospheres of other worlds, and affect planet formation mechanisms. Thus, implications from understanding convective dynamo mechanisms also extend to exoplanet habitability. How the convective dynamos driving these fields operate remains an important open problem. While we have extensive data to inform models of magnetic dynamo mechanisms in higher mass stars like our Sun, the coolest and lowest-mass objects that probe the substellar-planetary boundary do not possess the internal structures necessary to drive solar-type dynamos. A number of models examining fully convective dynamo mechanisms have been proposed but they remain unconstrained by magnetic field measurements in the lowest end of the substellar mass and temperature space. Detections of highly circularly polarized pulsed radio emission provide our only window into magnetic field measurements for objects in the ultracool brown dwarf regime, but these detections are very rare; until this dissertation, only one attempt out of 60 had been successful. The work presented in this dissertation seeks to address this problem and examines radio emission from late L, T, and Y spectral type brown dwarfs spanning 1-6 times the surface temperature of Earth and explores implications for fully convective magnetic dynamo models.

An eccentric companion at the edge of the brown dwarf desert orbiting the 2.4 M⊙ giant star HIP 67537

NASA Astrophysics Data System (ADS)

Jones, M. I.; Brahm, R.; Wittenmyer, R. A.; Drass, H.; Jenkins, J. S.; Melo, C. H. F.; Vos, J.; Rojo, P.

2017-06-01

We report the discovery of a substellar companion around the giant star HIP 67537. Based on precision radial velocity measurements from CHIRON and FEROS high-resolution spectroscopic data, we derived the following orbital elements for HIP 67537 b: mb sin I = 11.1+0.4-1.1Mjup, a =4.9+0.14-0.13 AU and e = 0.59+0.05-0.02 . Considering random inclination angles, this object has ≳65% probability to be above the theoretical deuterium-burning limit, thus it is one of the few known objects in the planet to brown-dwarf (BD) transition region. In addition, we analyzed the Hipparcos astrometric data of this star, from which we derived a minimum inclination angle for the companion of 2 deg. This value corresponds to an upper mass limit of 0.3 M⊙, therefore the probability that HIP 67537 b is stellar in nature is ≲7%. The large mass of the host star and the high orbital eccentricity makes HIP 67537 b a very interesting and rare substellar object. This is the second candidate companion in the brown dwarf desert detected in the sample of intermediate-mass stars targeted by the EXoPlanets aRound Evolved StarS (EXPRESS) radial velocity program, which corresponds to a detection fraction of f = +2.0-0.5 %. This value is larger than the fraction observed in solar-type stars, providing new observational evidence of an enhanced formation efficiency of massive substellar companions in massive disks. Finally, we speculate about different formation channels for this object. Based on observations collected at La Silla - Paranal Observatory under programs ID's 085.C-0557, 087.C.0476, 089.C-0524, 090.C-0345 and through the Chilean Telescope Time under programs ID's CN-12A-073, CN-12B-047, CN-13A-111, CN-2013B-51, CN-2014A-52, CN-15A-48, CN-15B-25 and CN-16A-13.

Brown dwarfs: at last filling the gap between stars and planets.

PubMed

Zuckerman, B

2000-02-01

Until the mid-1990s a person could not point to any celestial object and say with assurance that "here is a brown dwarf." Now dozens are known, and the study of brown dwarfs has come of age, touching upon major issues in astrophysics, including the nature of dark matter, the properties of substellar objects, and the origin of binary stars and planetary systems.

The first X-ray emitting brown dwarf.

NASA Astrophysics Data System (ADS)

Comerón, F.; Neuhäuser, R.; Kaas, A. A.

1998-12-01

The increasing number of brown dwarfs discovered in the last few years is rapidly opening the possibilities of studying a wide range of their properties and the ways in which these depend on essential parameters, such as the mass, the age, the rotation, or the environment. One of these properties is the magnetic field, which in principle should be expected to be important in fully convective objects such as brown dwarfs. The chromospheric X-ray emission, widely observed in M-type dwarfs (Neuhäuser 1997), has its origin in this magnetic activity. As such, it offers an observational tool to probe the interior of these objects, the mechanisms for the generation and maintenance of their magnetic fields, and the way in which the magnetic activity is affected by the basic parameters of the object. The detection of X-ray emission from brown dwarfs is thus of great importance to extend our understanding of the properties of stellar magnetic fields to the substellar domain, as well as to ascertain to what extent a small, substellar mass, and the consequent lack of a permanent nuclear energy source, can have an impact in the production and the evolution of a magnetic field.

MAPPING THE SHORES OF THE BROWN DWARF DESERT. III. YOUNG MOVING GROUPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, T. M.; Ireland, M. J.; Stewart, P.

2012-01-10

We present the results of an aperture-masking interferometry survey for substellar companions around 67 members of the young ({approx}8-200 Myr) nearby ({approx}5-86 pc) AB Doradus, {beta} Pictoris, Hercules-Lyra, TW Hya, and Tucana-Horologium stellar associations. Observations were made at near-infrared wavelengths between 1.2 and 3.8 {mu}m using the adaptive optics facilities of the Keck II, Very Large Telescope UT4, and Palomar Hale Telescopes. Typical contrast ratios of {approx}100-200 were achieved at angular separations between {approx}40 and 320 mas, with our survey being 100% complete for companions with masses below {approx}0.25 M{sub Sun} across this range. We report the discovery of amore » 0.52 {+-} 0.09 M{sub Sun} companion to HIP 14807, as well as the detections and orbits of previously known stellar companions to HD 16760, HD 113449, and HD 160934. We show that the companion to HD 16760 is in a face-on orbit, resulting in an upward revision of its mass from M{sub 2}sin i {approx} 14 M{sub J} to M{sub 2} = 0.28 {+-} 0.04 M{sub Sun }. No substellar companions were detected around any of our sample members, despite our ability to detect companions with masses below 80 M{sub J} for 50 of our targets: of these, our sensitivity extended down to 40 M{sub J} around 30 targets, with a subset of 22 subject to the still more stringent limit of 20 M{sub J}. A statistical analysis of our non-detection of substellar companions allows us to place constraints on their frequency around {approx}0.2-1.5 M{sub Sun} stars. In particular, considering companion mass distributions that have been proposed in the literature, we obtain an upper limit estimate of {approx}9%-11% for the frequency of 20-80 M{sub J} companions between 3 and 30 AU at 95% confidence, assuming that their semimajor axes are distributed according to dN/da{proportional_to}a{sup -1} in this range.« less

Brown dwarfs: At last filling the gap between stars and planets

PubMed Central

Zuckerman, Ben

2000-01-01

Until the mid-1990s a person could not point to any celestial object and say with assurance that “here is a brown dwarf.” Now dozens are known, and the study of brown dwarfs has come of age, touching upon major issues in astrophysics, including the nature of dark matter, the properties of substellar objects, and the origin of binary stars and planetary systems. PMID:10655468

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey. II. Disk Masses from ALMA Continuum Observations

NASA Astrophysics Data System (ADS)

Ward-Duong, K.; Patience, J.; Bulger, J.; van der Plas, G.; Ménard, F.; Pinte, C.; Jackson, A. P.; Bryden, G.; Turner, N. J.; Harvey, P.; Hales, A.; De Rosa, R. J.

2018-02-01

We report 885 μm ALMA continuum flux densities for 24 Taurus members spanning the stellar/substellar boundary with spectral types from M4 to M7.75. Of the 24 systems, 22 are detected at levels ranging from 1.0 to 55.7 mJy. The two nondetections are transition disks, though other transition disks in the sample are detected. Converting ALMA continuum measurements to masses using standard scaling laws and radiative transfer modeling yields dust mass estimates ranging from ∼0.3 to 20 M ⊕. The dust mass shows a declining trend with central object mass when combined with results from submillimeter surveys of more massive Taurus members. The substellar disks appear as part of a continuous sequence and not a distinct population. Compared to older Upper Sco members with similar masses across the substellar limit, the Taurus disks are brighter and more massive. Both Taurus and Upper Sco populations are consistent with an approximately linear relationship in M dust to M star, although derived power-law slopes depend strongly upon choices of stellar evolutionary model and dust temperature relation. The median disk around early-M stars in Taurus contains a comparable amount of mass in small solids as the average amount of heavy elements in Kepler planetary systems on short-period orbits around M-dwarf stars, with an order of magnitude spread in disk dust mass about the median value. Assuming a gas-to-dust ratio of 100:1, only a small number of low-mass stars and brown dwarfs have a total disk mass amenable to giant planet formation, consistent with the low frequency of giant planets orbiting M dwarfs.

A proposed search on the solar neighborhood for substellar objects

NASA Technical Reports Server (NTRS)

Reynolds, R. T.; Walker, R. G.; Tarter, J. C.

1980-01-01

The Infrared Astronomical Satellite (IRAS) program will produce an extremely sensitive all-sky survey over the wavelength region 8 to 120 microns when the mission is flown in 1982. These data will provide a novel opportunity to detect planetary-sized objects having masses smaller than 0.08 solar masses in or near the solar system. The improved detection limit of the IRAS will greatly increase the volume of space searched for such objects, as compared with previous optical and infrared studies.

SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars

NASA Technical Reports Server (NTRS)

Tanner, Angelle; Beichman, Charles; Akeson, Rachel; Ghez, Andrea; Grankin, Konstantin N.; Herbst, William; Hillenbrand, Lynne; Huerta, Marcos; Konopacky, Quinn; Metchev, Stanimir;

Astrophysics of brown dwarfs; Proceedings of the Workshop, George Mason University, Fairfax, VA, Oct. 14, 15, 1985

NASA Technical Reports Server (NTRS)

Kafatos, Minas C. (Editor); Harrington, Robert S. (Editor); Maran, Stephen P. (Editor)

1986-01-01

Various reports on theoretical and observational studies of brown dwarfs (BDs) are presented. The topics considered include: astrometric detection of BDs, search for substellar companions to nearby stars using IR imaging, constraints on BD mass function from optical and IR searches, properties of stellar objects near the main sequence mass limit, search for low-mass stellar companions with the HF precision velocity technique, dynamical search for substellar objects, search for BDs in the IRAS data base, deep CCD survey for low mass stars in the disk and halo, the Berkeley search for a faint solar companion, the luminosity function for late M stars, astronomic search for IR dwarfs, and the role of the Space Telescope in the detection of BDs. Also addressed are: theoretical significance of BDs, evolution of super-Jupiters, compositional indicators in IR spectra of BDs, evolution of BDs and the evolutionary status of VB8B, the position of BDs on universal diagrams, theoretical determination of the minimum protostellar mass, Population II BDs and dark halos.

Imaging Protoplanets: Observing Transition Disks with Non-Redundant Masking

NASA Astrophysics Data System (ADS)

Sallum, Stephanie

2017-01-01

Transition disks - protoplanetary disks with inner, solar system sized clearings - may be shaped by young planets. Directly imaging protoplanets in these objects requires high contrast and resolution, making them promising targets for future extremely large telescopes. The interferometric technique of non-redundant masking (NRM) is well suited for these observations, enabling companion detection for contrasts of 1:100 - 1:1000 at or within the diffraction limit. My dissertation focuses on searching for and characterizing companions in transition disk clearings using NRM. I will briefly describe the technique and present spatially resolved observations of the T Cha and LkCa 15 transition disks. Both of these objects hosted posited substellar companions. However multi-epoch T Cha datasets cannot be explained by planets orbiting in the disk plane. Conversely, LkCa 15 data taken with the Large Binocular Telescope (LBT) in single-aperture mode reveal the presence of multiple forming planets. The dual aperture LBT will provide triple the angular resolution of these observations, dramatically increasing the phase space for exoplanet detection. I will also present new results from the dual-aperture LBT, with similar resolution to that expected for next generation facilities like GMT.

The luminosity function at the end of the main sequence: Results of a deep, large-area, CCD survey for cool dwarfs

NASA Technical Reports Server (NTRS)

Kirkpatrick, J. Davy; Mcgraw, John T.; Hess, Thomas R.; Liebert, James; Mccarthy, Donald W., Jr.

1994-01-01

The luminosity function at the end of the main sequence is determined from V, R, and I data taken by the charge coupled devices (CCD)/Transit Instrument, a dedicated telescope surveying an 8.25 min wide strip of sky centered at delta = +28 deg, thus sampling Galactic latitudes of +90 deg down to -35 deg. A selection of 133 objects chosen via R - I and V - I colors has been observed spectroscopically at the 4.5 m Multiple Mirror Telescope to assess contributions by giants and subdwarfs and to verify that the reddest targets are objects of extremely late spectral class. Eighteen dwarfs of type M6 or later have been discovered, with the latest being of type M8.5. Data used for the determination of the luminosity function cover 27.3 sq. deg down to a completeness limit of R = 19.0. This luminosity function, computed at V, I, and bolometric magnitudes, shows an increase at the lowest luminosities, corresponding to spectral types later than M6- an effect suggested in earlier work by Reid & Gilmore and Legget & Hawkins. When the luminosity function is segregated into north Galactic and south Galactic portions, it is found that the upturn at faint magnitudes exists only in the southern sample. In fact, no dwarfs with M(sub I) is greater than or equal to 12.0 are found within the limiting volume of the 19.4 sq deg northern sample, in stark contrast to the smaller 7.9 sq deg area at southerly latitudes where seven such dwarfs are found. This fact, combined with the fact that the Sun is located approximately 10-40 pc north of the midplane, suggests that the latest dwarfs are part of a young population with a scale height much smaller than the 350 pc value generally adopted for other M dwarfs. These objects comprise a young population either because the lower metallicities prevelant at earlier epochs inhibited the formation of late M dwarfs or because the older counterparts of this population have cooled beyond current detection limits. The latter scenario would hold if these late-type M dwarfs are substellar. The luminosity function data together with an empirical derivation of the mass-luminosity relation (from Henry & McCarthy) are used to compute a mass function independent of theory. This mass function increases toward the end of the main sequence, but the observed density of M dwarfs is still insufficient to account for the missing mass. If the increases seen in the luminosity and mass functions are indicative of a large, unseen, substellar population, brown dwarfs may yet add significantly to the mass of the Galaxy.

PLANETS AROUND LOW-MASS STARS (PALMS). V. AGE-DATING LOW-MASS COMPANIONS TO MEMBERS AND INTERLOPERS OF YOUNG MOVING GROUPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowler, Brendan P.; Montet, Benjamin T.; Riddle, Reed

2015-06-10

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 systemmore » 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 low-mass quadruple system 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 Pleiades.« less

A new free-floating planet in the Upper Scorpius association

NASA Astrophysics Data System (ADS)

Peña Ramírez, K.; Béjar, V. J. S.; Zapatero Osorio, M. R.

2016-02-01

We report on a deep photometric survey covering an area of 1.17 deg2 in the young Upper Scorpius stellar association using VIMOS Iz and UKIDSS ZJHK data that was taken with several years in between. The search for the least massive population of Upper Scorpius (~5-10 Myr, 145 pc) is performed on the basis of various optical and infrared color-color and color-magnitude diagrams, including WISE photometry, in the magnitude interval J = 14.5-19 mag (completeness), which corresponds to substellar masses from 0.028 through 0.004 M⊙ at the age and distance of Upper Scorpius. We also present the proper motion analysis of the photometric candidates, finding that two objects successfully pass all photometric and astrometric criteria for membership in the young stellar association. One of them, USco J155150.2-213457, is a new discovery. We obtained low resolution, near-infrared spectroscopy (R ~ 450, 0.85-2.35 μm) of this new finding using the FIRE instrument. We confirmed its low-gravity atmosphere expected for an Upper Scorpius member (weak alkaline lines, strong VO absorption, peaked H-band pseudocontinuum). By comparison with spectroscopic standards, we derive a spectral type of L6 ± 1, and estimate a mass of ≈0.008-0.010 M⊙ for USco J155150.2-213457. The colors and spectral slope of this object resemble those of other young, cool members of Upper Scorpius and σ Orionis (~3 Myr) and field, high gravity dwarfs of related classification in contrast with the very red indices of field, low gravity, L-type dwarfs of intermediate age. USco J155150.2-213457, which does not show infrared flux excesses up to 4.5 μm, becomes one of the least massive and latest type objects known in the entire Upper Scorpius stellar association.

CHARACTERIZING THE BROWN DWARF FORMATION CHANNELS FROM THE INITIAL MASS FUNCTION AND BINARY-STAR DYNAMICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thies, Ingo; Pflamm-Altenburg, Jan; Kroupa, Pavel

2015-02-10

The stellar initial mass function (IMF) is a key property of stellar populations. There is growing evidence that the classical star-formation mechanism by the direct cloud fragmentation process has difficulties reproducing the observed abundance and binary properties of brown dwarfs and very-low-mass stars. In particular, recent analytical derivations of the stellar IMF exhibit a deficit of brown dwarfs compared to observational data. Here we derive the residual mass function of brown dwarfs as an empirical measure of the brown dwarf deficiency in recent star-formation models with respect to observations and show that it is compatible with the substellar part ofmore » the Thies-Kroupa IMF and the mass function obtained by numerical simulations. We conclude that the existing models may be further improved by including a substellar correction term that accounts for additional formation channels like disk or filament fragmentation. The term ''peripheral fragmentation'' is introduced here for such additional formation channels. In addition, we present an updated analytical model of stellar and substellar binarity. The resulting binary fraction and the dynamically evolved companion mass-ratio distribution are in good agreement with observational data on stellar and very-low-mass binaries in the Galactic field, in clusters, and in dynamically unprocessed groups of stars if all stars form as binaries with stellar companions. Cautionary notes are given on the proper analysis of mass functions and the companion mass-ratio distribution and the interpretation of the results. The existence of accretion disks around young brown dwarfs does not imply that these form just like stars in direct fragmentation.« less

The Influence of a Substellar Continent on the Climate of a Tidally Locked Exoplanet

NASA Astrophysics Data System (ADS)

Lewis, Neil T.; Lambert, F. Hugo; Boutle, Ian A.; Mayne, Nathan J.; Manners, James; Acreman, David M.

2018-02-01

Previous studies have demonstrated that continental carbon-silicate weathering is important to the continued habitability of a terrestrial planet. Despite this, few studies have considered the influence of land on the climate of a tidally locked planet. In this work we use the Met Office Unified Model, coupled to a land-surface model, to investigate the climate effects of a continent located at the substellar point. We choose to use the orbital and planetary parameters of Proxima Centauri B as a template, to allow comparison with the work of others. A region of the surface where T s > 273.15 K is always retained, and previous conclusions on the habitability of Proxima Centauri B remain intact. We find that substellar land causes global cooling and increases day–night temperature contrasts by limiting heat redistribution. Furthermore, we find that substellar land is able to introduce a regime change in the atmospheric circulation. Specifically, when a continent offset to the east of the substellar point is introduced, we observe the formation of two mid-latitude counterrotating jets, and a substantially weakened equatorial superrotating jet.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norris, Jackson M.; Wright, Jason T.; Mahadevan, Suvrath

It has been argued that a substellar companion may significantly influence the evolution of the progenitors of subdwarf B (sdB) stars. Recently, the bright sdB star HD 149382 has been claimed to host a substellar (possibly planetary) companion with a period of 2.391 days. This has important implications for the evolution of the progenitors of sdB stars as well as the source of the UV excess seen in elliptical galaxies. In order to verify this putative companion, we made 10 radial velocity measurements of HD 149382 over 17 days with the High Resolution Spectrograph at the Hobby-Eberly Telescope. Our datamore » conclusively demonstrate that the putative substellar companion does not exist, and they exclude the presence of almost any substellar companion with P < 28 days and Msin i {approx}> 1 M{sub Jup}.« less

McDonald Observatory Planetary Search - A high precision stellar radial velocity survey for other planetary systems

NASA Technical Reports Server (NTRS)

Cochran, William D.; Hatzes, Artie P.

1993-01-01

The McDonald Observatory Planetary Search program surveyed a sample of 33 nearby F, G, and K stars since September 1987 to search for substellar companion objects. Measurements of stellar radial velocity variations to a precision of better than 10 m/s were performed as routine observations to detect Jovian planets in orbit around solar type stars. Results confirm the detection of a companion object to HD114762.

Is This Speck of Light an Exoplanet?

NASA Astrophysics Data System (ADS)

2004-09-01

VLT Images and Spectra of Intriguing Object near Young Brown Dwarf [1] Summary Is this newly discovered feeble point of light the long-sought bona-fide image of an exoplanet? A research paper by an international team of astronomers [2] provides sound arguments in favour, but the definitive answer is now awaiting further observations. On several occasions during the past years, astronomical images revealed faint objects, seen near much brighter stars. Some of these have been thought to be those of orbiting exoplanets, but after further study, none of them could stand up to the real test. Some turned out to be faint stellar companions, others were entirely unrelated background stars. This one may well be different. In April of this year, the team of European and American astronomers detected a faint and very red point of light very near (at 0.8 arcsec angular distance) a brown-dwarf object, designated 2MASSWJ1207334-393254. Also known as "2M1207", this is a "failed star", i.e. a body too small for major nuclear fusion processes to have ignited in its interior and now producing energy by contraction. It is a member of the TW Hydrae stellar association located at a distance of about 230 light-years. The discovery was made with the adaptive-optics supported NACO facility [3] at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory (Chile). The feeble object is more than 100 times fainter than 2M1207 and its near-infrared spectrum was obtained with great efforts in June 2004 by NACO, at the technical limit of the powerful facility. This spectrum shows the signatures of water molecules and confirms that the object must be comparatively small and light. None of the available observations contradict that it may be an exoplanet in orbit around 2M1207. Taking into account the infrared colours and the spectral data, evolutionary model calculations point to a 5 jupiter-mass planet in orbit around 2M1207. Still, they do not yet allow a clear-cut decision about the real nature of this intriguing object. Thus, the astronomers refer to it as a "Giant Planet Candidate Companion (GPCC)" [4]. Observations will now be made to ascertain whether the motion in the sky of GPCC is compatible with that of a planet orbiting 2M1207. This should become evident within 1-2 years at the most. PR Photo 26a/04: NACO image of the brown dwarf object 2M1207 and GPCC PR Photo 26b/04: Near-infrared spectrum of the brown dwarf object 2M1207 and GPCC PR Photo 26c/04: Comparison between the possible 2M1207 system and the solar system Just a speck of light ESO PR Photo 26a/04 ESO PR Photo 26a/04 The Brown Dwarf Object 2M1207 and GPCC [Preview - JPEG: 400 x 471 pix - 65k] [Normal - JPEG: 800 x 942 pix - 158k] Caption: ESO PR Photo 26a/04 is a composite image of the brown dwarf object 2M1207 (centre) and the fainter object seen near it, at an angular distance of 778 milliarcsec. Designated "Giant Planet Candidate Companion" by the discoverers, it may represent the first image of an exoplanet. Further observations, in particular of its motion in the sky relative to 2M1207 are needed to ascertain its true nature. The photo is based on three near-infrared exposures (in the H, K and L' wavebands) with the NACO adaptive-optics facility at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory. Since 1998, a team of European and American astronomers [2] is studying the environment of young, nearby "stellar associations", i.e., large conglomerates of mostly young stars and the dust and gas clouds from which they were recently formed. The stars in these associations are ideal targets for the direct imaging of sub-stellar companions (planets or brown dwarf objects). The leader of the team, ESO astronomer Gael Chauvin notes that "whatever their nature, sub-stellar objects are much hotter and brighter when young - tens of millions of years - and therefore can be more easily detected than older objects of similar mass". The team especially focused on the study of the TW Hydrae Association. It is located in the direction of the constellation Hydra (The Water-Snake) deep down in the southern sky, at a distance of about 230 light-years. For this, they used the NACO facility [3] at the 8.2-m VLT Yepun telescope, one of the four giant telescopes at the ESO Paranal Observatory in northern Chile. The instrument's adaptive optics (AO) overcome the distortion induced by atmospheric turbulence, producing extremely sharp near-infrared images. The infrared wavefront sensor was an essential component of the AO system for the success of these observations. This unique instrument senses the deformation of the near-infrared image, i.e. in a wavelength region where objects like 2M1207 (see below) are much brighter than in the visible range. The TW Hydrae Association contains a star with an orbiting brown dwarf companion, approximately 20 times the mass of Jupiter, and four stars surrounded by dusty proto-planetary disks. Brown dwarf objects are "failed stars", i.e. bodies too small for nuclear processes to have ignited in their interior and now producing energy by contraction. They emit almost no visible light. Like the Sun and the giant planets in the solar system, they are composed mainly of hydrogen gas, perhaps with swirling cloud belts. On a series of exposures made through different optical filters, the astronomers discovered a tiny red speck of light, only 0.8 arcsec from the TW Hydrae Association brown-dwarf object 2MASSWJ1207334-393254, or just "2M1207", cf. PR Photo 26a/04. The feeble image is more than 100 times fainter than that of 2M1207. "If these images had been obtained without adaptive optics, that object would not have been seen," says Gael Chauvin. Christophe Dumas, another member of the team, is enthusiastic: "The thrill of seeing this faint source of light in real-time on the instrument display was unbelievable. Although it is surely much bigger than a terrestrial-size object, it is a strange feeling that it may indeed be the first planetary system beyond our own ever imaged." Exoplanet or Brown Dwarf? ESO PR Photo 26b/04 ESO PR Photo 26b/04 The Brown Dwarf Object 2M1207 and GPCC [Preview - JPEG: 400 x 486 pix - 102k] [Normal - JPEG: 800 x 912 pix - 234k] Caption: ESO PR Photo 26b/04 shows near-infrared H-band spectra of the brown dwarf object 2M1207 and the fainter "GPCC" object seen near it, obtained with the NACO facility at the 8.2-m VLT Yepun telescope. In the upper part, the spectrum of 2M1207 (fully drawn blue curve) is compared with that of another substellar object (T513; dashed line); in the lower, the (somewhat noisy) spectrum of GPCC (fully drawn red curve) is compared with two substellar objects of different types (2M0301 and SDSS0539). The spectrum of GPCC is clearly very similar to these, confirming the substellar nature of this body. The broad dips at the left and the right are clear signatures of water in the (atmospheres of the) objects. What is the nature of this faint object [4]? Could it be an exoplanet in orbit around that young brown dwarf object at a projected distance of about 8,250 million km (about twice the distance between the Sun and Neptune)? "If the candidate companion of 2M1207 is really a planet, this would be the first time that a gravitationally bound exoplanet has been imaged around a star or a brown dwarf" says Benjamin Zuckerman of UCLA, a member of the team and also of NASA's Astrobiology Institute. Using high-angular-resolution spectroscopy with the NACO facility, the team has confirmed the substellar status of this object - now referred to as the "Giant Planet Candidate Companion (GPCC)" - by identifying broad water-band absorptions in its atmosphere, cf. PR Photo 26b/04. The spectrum of a young and hot planet - as the GPCC may well be - will have strong similarities with an older and more massive object such as a brown dwarf. However, when it cools down after a few tens of millions of years, such an object will show the spectral signatures of a giant gaseous planet like those in our own solar system. Although the spectrum of GPCC is quite "noisy" because of its faintness, the team was able to assign to it a spectral characterization that excludes a possible contamination by extra-galactic objects or late-type cool stars with abnormal infrared excess, located beyond the brown dwarf. After a very careful study of all options, the team found that, although this is statistically very improbable, the possibility that this object could be an older and more massive, foreground or background, cool brown dwarf cannot be completely excluded. The related detailed analysis is available in the resulting research paper that has been accepted for publication in the European journal Astronomy & Astrophysics (see below). Implications The brown dwarf 2M1207 has approximately 25 times the mass of Jupiter and is thus about 42 times lighter than the Sun. As a member of the TW Hydrae Association, it is about eight million years old. Because our solar system is 4,600 million years old, there is no way to directly measure how the Earth and other planets formed during the first tens of millions of years following the formation of the Sun. But, if astronomers can study the vicinity of young stars which are now only tens of millions of years old, then by witnessing a variety of planetary systems that are now forming, they will be able to understand much more accurately our own distant origins. Anne-Marie Lagrange, a member of the team from the Grenoble Observatory (France), looks towards the future: "Our discovery represents a first step towards opening a whole new field in astrophysics: the imaging and spectroscopic study of planetary systems. Such studies will enable astronomers to characterize the physical structure and chemical composition of giant and, eventually, terrestrial-like planets." Follow-up observations ESO PR Photo 26c/04 ESO PR Photo 26c/04 Comparison between the solar and 2M1207 systems [Preview - JPEG: 400 x 190 pix - 38k] [Normal - JPEG: 800 x 397 pix - 86k] [HiRes - JPEG: 2000 x 948 pix - 326k] Caption: ESO PR Photo 26c/04 shows for illustration a comparison between the solar system and the brown dwarf object 2M1207 system with its possible planet at 55 AU distance. The sizes of the objects are drawn to the same scale, but the distances have been strongly compressed. Taking into account the infrared colours and the spectral data available for GPCC, evolutionary model calculations point to a 5 jupiter-mass planet, about 55 times more distant from 2M1207 than the Earth is from the Sun (55 AU). The surface temperature appears to be about 10 times hotter than Jupiter, about 1000 °C; this is easily explained by the amount of energy that must be liberated during the current rate of contraction of this young object (indeed, the much older giant planet Jupiter is still producing energy in its interior). The astronomers will now continue their research to confirm or deny whether they have in fact discovered an exoplanet. Over the next few years, they expect to establish beyond doubt whether the object is indeed a planet in orbit around the brown dwarf 2M1207 by watching how the two objects move through space and to learn whether or not they move together. They will also measure the brightness of the GPCC at multiple wavelengths and more spectral observations may be attempted. There is no doubt that future programmes to image exoplanets around nearby stars, either from the ground with extremely large telescopes equipped with specially designed adaptive optics, or from space with special planet-finder telescopes, will greatly profit from current technological achievements. More information The results presented in this ESO Press Release are based on a research paper ("A Giant Planet Candidate near a Young Brown Dwarf" by G. Chauvin et al.) that has been accepted for publication and will appear in the leading research journal "Astronomy and Astrophysics" on September 23, 2004 (Vol. 425, Issue 2, page L29). A preprint is available here and also as astro-ph0409323. Notes [1]: This press release is issued simultaneously by ESO and CNRS (in French). [2]: The team consists of Gael Chauvin and Christophe Dumas (ESO-Chile), Anne-Marie Lagrange and Jean-Luc Beuzit (LAOG, Grenoble, France), Benjamin Zuckerman and Inseok Song (UCLA, Los Angeles, USA), David Mouillet (LAOMP, Tarbes, France) and Patrick Lowrance (IPAC, Pasadena, USA). The American members of the team acknowledge funding in part by NASA's Astrobiology Institute. [3]: The NACO facility (from NAOS/Nasmyth Adaptive Optics System and CONICA/Near-Infrared Imager and Spectrograph) at the 8.2-m VLT Yepun telescope on Paranal offers the capability to produce diffraction-limited near-infrared images of astronomical objects. It senses the radiation in this wavelength region with the N90C10 dichroic; 90 percent of the flux is transmitted to the wavefront sensor and 10 percent to the near-infrared camera CONICA. This mode is particularly useful for sharp imaging of red and very-low-mass stellar or substellar objects. The adaptive optics corrector (NAOS) was built, under an ESO contract, by Office National d'Etudes et de Recherches Aérospatiales (ONERA), Laboratoire d'Astrophysique de Grenoble (LAOG) and the LESIA and GEPI laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. [4]: What is the difference between a small brown dwarf and an exoplanet ? The border line between the two is still being investigated but it appears that a brown dwarf object is formed in the same way as stars, i.e. by contraction in an interstellar cloud while planets are formed within stable circumstellar disks via collision/accretion of planetesimals or disk instabilities. This implies that brown dwarfs are formed faster (less than 1 million years) than planets (~10 million years). Another way of separating the two kinds of objects is by mass (as this is also done between brown dwarfs and stars): (giant) planets are lighter than about 13 jupiter-masses (the critical mass needed to ignite deuterium fusion), brown dwarfs are heavier. Unfortunately, the first definition cannot be used in practice, e.g., when detecting a faint companion as in the present case, since the observations do not provide information about the way the object was formed. On the contrary, the above mass criterion is useful in the sense that spectroscopy and astrometry of a faint object, together with the appropriate evolutionary models, may reveal the mass and hence the nature of the object.

The Class of Jsolated Stars and Luminous Planetary Nebulae in old stellar populations

NASA Astrophysics Data System (ADS)

Sabach, Efrat; Soker, Noam

2018-06-01

We suggest that stars whose angular momentum (J) does not increase by a companion, star or planet, along their post-main sequence evolution have much lower mass loss rates along their giant branches. Their classification to a separate group can bring insight on their late evolution stages. We here term these Jsolated stars. We argue that the mass loss rate of Jsolated stars is poorly determined because the mass loss rate expressions on the giant branches are empirically based on samples containing stars that experience strong binary interaction, with stellar or sub-stellar companions, e.g., planetary nebula (PN) progenitors. We use our earlier claim for a low mass loss rate of asymptotic giant branch (AGB) stars that are not spun-up by a stellar or substellar companion to show that we can account for the enigmatic finding that the brightest PNe in old stellar populations reach the same luminosity as the brightest PNe in young populations. It is quite likely that the best solution to the existence of bright PNe in old stellar populations is the combination of higher AGB luminosities, as obtained in some new stellar models, and the lower mass loss rates invoked here.

PSYM-WIDE: A Survey for Large-separation Planetary-mass Companions to Late Spectral Type Members of Young Moving Groups

NASA Astrophysics Data System (ADS)

Naud, Marie-Eve; Artigau, Étienne; Doyon, René; Malo, Lison; Gagné, Jonathan; Lafrenière, David; Wolf, Christian; Magnier, Eugene A.

2017-09-01

We present the results of a direct imaging survey for very large separation (>100 au), low-mass companions around 95 nearby young K5-L5 stars and brown dwarfs. They are high-likelihood candidates or confirmed members of the young (≲150 Myr) β Pictoris and AB Doradus moving groups (ABDMG) and the TW Hya, Tucana-Horologium, Columba, Carina, and Argus associations. Images in I\\prime and z\\prime filters were obtained with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to search for companions down to an apparent magnitude of z\\prime ˜ 22-24 at separations ≳20″ from the targets and in the remainder of the wide 5.‧5 × 5.‧5 GMOS field of view. This allowed us to probe the most distant region where planetary-mass companions could be gravitationally bound to the targets. This region was left largely unstudied by past high-contrast imaging surveys, which probed much closer-in separations. This survey led to the discovery of a planetary-mass (9-13 {M}{Jup}) companion at 2000 au from the M3V star GU Psc, a highly probable member of ABDMG. No other substellar companions were identified. These results allowed us to constrain the frequency of distant planetary-mass companions (5-13 {M}{Jup}) to {0.84}-0.66+6.73% (95% confidence) at semimajor axes between 500 and 5000 au around young K5-L5 stars and brown dwarfs. This is consistent with other studies suggesting that gravitationally bound planetary-mass companions at wide separations from low-mass stars are relatively rare.

Planets around Low-mass Stars (PALMS). VI. Discovery of a Remarkably Red Planetary-mass Companion to the AB Dor Moving Group Candidate 2MASS J22362452+4751425*

NASA Astrophysics Data System (ADS)

Bowler, Brendan P.; Liu, Michael C.; Mawet, Dimitri; Ngo, Henry; Malo, Lison; Mace, Gregory N.; McLane, Jacob N.; Lu, Jessica R.; Tristan, Isaiah I.; Hinkley, Sasha; Hillenbrand, Lynne A.; Shkolnik, Evgenya L.; Benneke, Björn; Best, William M. J.

2017-01-01

We report the discovery of an extremely red planetary-mass companion to 2MASS J22362452+4751425, a ≈0.6 M⊙ late-K dwarf likely belonging to the ˜120 Myr AB Doradus moving group. 2M2236+4751 b was identified in multi-epoch NIRC2 adaptive optics imaging at Keck Observatory at a separation of 3\\buildrel{\\prime\\prime}\\over{.} 7, or 230 ± 20 AU in projection at the kinematic distance of 63 ± 5 pc to its host star. Assuming membership in the AB Dor group, as suggested from its kinematics, the inferred mass of 2M2236+4751 b is 11-14 MJup. Follow-up Keck/OSIRIS K-band spectroscopy of the companion reveals strong CO absorption similar to other faint red L dwarfs and lacks signs of methane absorption, despite having an effective temperature of ≈900-1200 K. With a (J-K)MKO color of 2.69 ± 0.12 mag, the near-infrared slope of 2M2236+4751 b is redder than all of the HR 8799 planets and instead resembles the ≈23 Myr isolated planetary-mass object PSO J318.5-22, implying that similarly thick photospheric clouds can persist in the atmospheres of giant planets at ages beyond 100 Myr. In near-infrared color-magnitude diagrams, 2M2236+4751 b is located at the tip of the red L dwarf sequence and appears to define the “elbow” of the AB Dor substellar isochrone separating low-gravity L dwarfs from the cooler young T dwarf track. 2M2236+4751 b is the reddest substellar companion to a star and will be a valuable benchmark to study the shared atmospheric properties of young low-mass brown dwarfs and extrasolar giant planets. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

X-shooter spectroscopy of young stellar objects. IV. Accretion in low-mass stars and substellar objects in Lupus

NASA Astrophysics Data System (ADS)

Alcalá, J. M.; Natta, A.; Manara, C. F.; Spezzi, L.; Stelzer, B.; Frasca, A.; Biazzo, K.; Covino, E.; Randich, S.; Rigliaco, E.; Testi, L.; Comerón, F.; Cupani, G.; D'Elia, V.

2014-01-01

We present VLT/X-shooter observations of a sample of 36 accreting low-mass stellar and substellar objects (YSOs) in the Lupus star-forming region, spanning a range in mass from ~0.03 to ~1.2 M⊙, but mostly with 0.1 M⊙

Exploring Substellar Evolution with the Coldest Brown Dwarfs

NASA Astrophysics Data System (ADS)

Dupuy, Trent J.

2017-01-01

The coldest brown dwarfs are our best analogs to extrasolar gas-giant planets, representing the lowest mass products of star formation. Our view of such objects has been transformed over the last few years as new observations have revealed that the solar neighborhood is populated by much colder objects than previously recognized. At the center of efforts to discover and characterize these coldest substellar objects have been observations from NASA missions (WISE, Spitzer, HST) and the Keck Telescopes. I will review the tremendous progress made in this field over just the last few years thanks to major community efforts to overcome observational challenges in obtaining spectroscopy, photometry, and astrometry of these infrared-faint, optically invisible objects. Spectra from HST and Keck were key in establishing the much anticipated "Y" spectral type, extending the classic stellar classification scheme to atmospheres as cool as 300-400 K. Parallaxes and photometry from Spitzer and Keck have provided absolute fluxes, enabling robust temperature determinations and critical tests of model atmopheres. High-resolution imaging with Keck laser guide star adaptive optics (LGS AO) has been the most prolific resource for revealing tight companions among the coldest brown dwarfs. In fact, with continued orbit monitoring with Keck LGS AO and HST, these binary systems will ultimately provide dynamical masses that will allow the strongest tests of models and reveal if the coldest brown dwarfs are indeed "planetary mass" (less than about 13 Jupiter masses) as is currently thought.

A SUBSTELLAR COMPANION TO THE DUSTY PLEIADES STAR HD 23514

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, David R.; Zuckerman, B.; Marois, Christian

2012-03-20

With adaptive optics imaging at Keck observatory, we have discovered a substellar companion to the F6 Pleiades star HD 23514, one of the dustiest main-sequence stars known to date (L{sub IR}/L{sub *} {approx} 2%). This is one of the first brown dwarfs discovered as a companion to a star in the Pleiades. The 0.06 M{sub Sun} late-M secondary has a projected separation of {approx}360 AU. The scarcity of substellar companions to stellar primaries in the Pleiades combined with the extremely dusty environment make this a unique system to study.

Planets Around Low-mass Stars (PALMS). V. Age-dating Low-mass Companions to Members and Interlopers of Young Moving Groups

NASA Astrophysics Data System (ADS)

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.

2015-06-01

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 system 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 low-mass quadruple system 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 Pleiades. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile (ESO Program 090.A-9010(A)).

A companion candidate in the gap of the T Chamaeleontis transitional disk

NASA Astrophysics Data System (ADS)

Huélamo, N.; Lacour, S.; Tuthill, P.; Ireland, M.; Kraus, A.; Chauvin, G.

2011-04-01

Context. T Cha is a young star surrounded by a cold disk. The presence of a gap within its disk, inferred from fitting to the spectral energy distribution, has suggested on-going planetary formation. Aims: The aim of this work is to look for very low-mass companions within the disk gap of T Cha. Methods: We observed T Cha in L' and Ks with NAOS-CONICA, the adaptive optics system at the VLT, using sparse aperture masking. Results: We detected a source in the L' data at a separation of 62 ± 7 mas, position angle of ~78 ± 1 degrees, and a contrast of ΔL' = 5.1 ± 0.2 mag. The object is not detected in the Ks band data, which show a 3-σ contrast limit of 5.2 mag at the position of the detected L' source. For a distance of 108 pc, the detected companion candidate is located at 6.7 AU from the primary, well within the disk gap. If T Cha and the companion candidate are bound, the comparison of the L' and Ks photometry with evolutionary tracks shows that the photometry is inconsistent with any unextincted photosphere at the age and distance of T Cha. The detected object shows a very red Ks - L' color, for which a possible explanation would be a significant amount of dust around it. This would imply that the companion candidate is young, which would strengthen the case for a physical companion, and moreover that the object would be in the substellar regime, according to the Ks upper limit. Another exciting possibility would be that this companion is a recently formed planet within the disk. Additional observations are mandatory to confirm that the object is bound and to properly characterize it. Based on observations obtained at the European Southern Observatory using the Very Large Telescope in Cerro Paranal, Chile, under program 84.C-0755(A).

Precise Ages for the Benchmark Brown Dwarfs HD 19467 B and HD 4747 B

NASA Astrophysics Data System (ADS)

Wood, Charlotte; Boyajian, Tabetha; Crepp, Justin; von Braun, Kaspar; Brewer, John; Schaefer, Gail; Adams, Arthur; White, Tim

2018-01-01

Large uncertainty in the age of brown dwarfs, stemming from a mass-age degeneracy, makes it difficult to constrain substellar evolutionary models. To break the degeneracy, we need ''benchmark" brown dwarfs (found in binary systems) whose ages can be determined independent of their masses. HD~19467~B and HD~4747~B are two benchmark brown dwarfs detected through the TRENDS (TaRgeting bENchmark objects with Doppler Spectroscopy) high-contrast imaging program for which we have dynamical mass measurements. To constrain their ages independently through isochronal analysis, we measured the radii of the host stars with interferometry using the Center for High Angular Resolution Astronomy (CHARA) Array. Assuming the brown dwarfs have the same ages as their host stars, we use these results to distinguish between several substellar evolutionary models. In this poster, we present new age estimates for HD~19467 and HD~4747 that are more accurate and precise and show our preliminary comparisons to cooling models.

The Pan-STARRS1 Proper-motion Survey for Young Brown Dwarfs in Nearby Star-forming Regions. I. Taurus Discoveries and a Reddening-free Classification Method for Ultracool Dwarfs

NASA Astrophysics Data System (ADS)

Zhang, Zhoujian; Liu, Michael C.; Best, William M. J.; Magnier, Eugene A.; Aller, Kimberly M.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Metcalfe, N.; Wainscoat, R. J.; Waters, C.

2018-05-01

We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3π Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370 deg2) and deeper (down to ≈3 M Jup) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution (R ≈ 100) near-infrared spectra to quantify reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (≲100–3 M Jup in Taurus). We have discovered 25 low-gravity (VL-G) and the first 11 intermediate-gravity (INT-G) substellar (M6–L1) members of Taurus, constituting the largest single increase of Taurus brown dwarfs to date. We have also discovered 1 new Pleiades member and 13 new members of the Perseus OB2 association, including a candidate very wide separation (58 kau) binary. We homogeneously reclassify the spectral types and extinctions of all previously known Taurus brown dwarfs. Altogether our discoveries have thus far increased the substellar census in Taurus by ≈40% and added three more L-type members (≲5–10 M Jup). Most notably, our discoveries reveal an older (>10 Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. The mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes.

SCExAO and GPI Y JH band photometry and integral field spectroscopy of the young brown dwarf companion to HD 1160

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia, Eugenio Victor; Currie, Thayne; Guyon, Olivier

Here, we present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957–1.120 μm) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5more » $${}_{-0.5}^{+1.0}$$, where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000–3100 K, a surface gravity of log g = 4–4.5, a radius of 1.55 ± 0.10 R J, and a luminosity of log L/L ⊙ = –2.76 ± 0.05. Neither the primary's Hertzspring–Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80–125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70–90 M J). If we consider HD 1160 A alone, younger ages (20–125 Myr) and a brown dwarf-like mass (35–90 M J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system's age and how HD 1160 B fits within the context of (sub)stellar evolution.« less

SCExAO and GPI Y JH band photometry and integral field spectroscopy of the young brown dwarf companion to HD 1160

DOE PAGES

Garcia, Eugenio Victor; Currie, Thayne; Guyon, Olivier; ...

2017-01-10

Here, we present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957–1.120 μm) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5more » $${}_{-0.5}^{+1.0}$$, where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000–3100 K, a surface gravity of log g = 4–4.5, a radius of 1.55 ± 0.10 R J, and a luminosity of log L/L ⊙ = –2.76 ± 0.05. Neither the primary's Hertzspring–Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80–125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70–90 M J). If we consider HD 1160 A alone, younger ages (20–125 Myr) and a brown dwarf-like mass (35–90 M J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system's age and how HD 1160 B fits within the context of (sub)stellar evolution.« less

The First X-shooter Observations of Jets from Young Stars

NASA Astrophysics Data System (ADS)

Bacciotti, F.; Whelan, E. T.; Alcalá, J. M.; Nisini, B.; Podio, L.; Randich, S.; Stelzer, B.; Cupani, G.

2011-08-01

We present the first pilot study of jets from young stars conducted with X-shooter, on the ESO/Very Large Telescope. As it offers simultaneous, high-quality spectra in the range 300-2500 nm, X-shooter is uniquely important for spectral diagnostics in jet studies. We chose to probe the accretion/ejection mechanisms at low stellar masses examining two targets with well-resolved continuous jets lying on the plane of the sky: ESO-HA 574 in Chameleon I and Par-Lup3-4 in Lupus III. The mass of the latter is close to the sub-stellar boundary (M sstarf = 0.13 M sun). A large number of emission lines probing regions of different excitation are identified, position-velocity diagrams are presented, and mass outflow/accretion rates are estimated. Comparison between the two objects is striking. ESO-HA 574 is a weakly accreting star for which we estimate a mass accretion rate of log (\\dot{M}_{acc}) = -10.8 +/- 0.5 (in M sun yr-1), yet it drives a powerful jet with \\dot{M}_{out} ~ 1.5-2.7 × 10-9 M sun yr-1. These values can be reconciled with a magneto-centrifugal jet acceleration mechanism assuming that the presence of the edge-on disk severely depresses the luminosity of the accretion tracers. In comparison, Par-Lup3-4, with stronger mass accretion (log (\\dot{M}_{acc}) = -9.1 +/- 0.4 M sun yr-1), drives a low-excitation jet with about \\dot{M}_{out} ~ 3.2 × 10-10 M sun yr-1 in both lobes. Despite the low stellar mass, \\dot{M}_{out}/\\dot{M}_{acc} for Par-Lup3-4 is at the upper limit of the range usually measured for young objects, but still compatible with a steady magneto-centrifugal wind scenario if all uncertainties are considered. Based on Observations collected with X-shooter at the Very Large Telescope on Cerro Paranal (Chile), operated by the European Southern Observatory (ESO). Program ID: 085.C-0238(A).

Primeval very low-mass stars and brown dwarfs - III. The halo transitional brown dwarfs

NASA Astrophysics Data System (ADS)

Zhang, Z. H.; Pinfield, D. J.; Gálvez-Ortiz, M. C.; Homeier, D.; Burgasser, A. J.; Lodieu, N.; Martín, E. L.; Osorio, M. R. Zapatero; Allard, F.; Jones, H. R. A.; Smart, R. L.; Martí, B. López; Burningham, B.; Rebolo, R.

2018-05-01

We report the discovery of an esdL3 subdwarf, ULAS J020858.62+020657.0 and a usdL4.5 subdwarf, ULAS J230711.01+014447.1. They were identified as L subdwarfs by optical spectra obtained with the Gran Telescopio Canarias, and followed up by optical to near infrared spectroscopy with the Very Large Telescope. We also obtained an optical to near infrared spectrum of a previously known L subdwarf, ULAS J135058.85+081506.8, and re-classified it as a usdL3 subdwarf. These three objects all have typical halo kinematics. They have Teff around 2050-2250 K, -1.8 ≤ [Fe/H] ≤-1.5, and mass around 0.0822-0.0833 M⊙, according to model spectral fitting and evolutionary models. These sources are likely halo transitional brown dwarfs with unsteady hydrogen fusions, as their masses are just below the hydrogen-burning minimum mass, which is ˜ 0.0845 M⊙ at [Fe/H] = -1.6 and ˜ 0.0855 M⊙ at [Fe/H] = -1.8. Including these, there are now nine objects in the `halo brown dwarf transition zone', which is a `substellar subdwarf gap' spans a wide temperature range within a narrow mass range of the substellar population.

International Deep Planet Survey, 317 stars to determine the wide-separated planet frequency

NASA Astrophysics Data System (ADS)

Galicher, R.; Marois, C.; Macintosh, B.; Zuckerman, B.; Song, I.; Barman, T.; Patience, J.

2013-09-01

Since 2000, more than 300 nearby young stars were observed for the International Deep Planet Survey with adaptive optics systems at Gemini (NIRI/NICI), Keck (Nirc2), and VLT (Naco). Massive young AF stars were included in our sample whereas they have generally been neglected in first generation surveys because the contrast and target distances are less favorable to image substellar companions. The most significant discovery of the campaign is the now well-known HR 8799 multi-planet system. This remarkable finding allows, for the first time, an estimate of the Jovians planet population at large separations (further than a few AUs) instead of deriving upper limits. During my presentation, I will present the survey showing images of multiple stars and planets. I will then propose a statistic study of the observed stars deriving constraints on the Jupiter-like planet frequency at large separations.

Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering

NASA Astrophysics Data System (ADS)

Stark, C. R.; Diver, D. A.

2018-04-01

Context. In contemporary sub-stellar model atmospheres, dust growth occurs through neutral gas-phase surface chemistry. Recently, there has been a growing body of theoretical and observational evidence suggesting that ionisation processes can also occur. As a result, atmospheres are populated by regions composed of plasma, gas and dust, and the consequent influence of plasma processes on dust evolution is enhanced. Aim. This paper aims to introduce a new model of dust growth and destruction in sub-stellar atmospheres via plasma deposition and plasma sputtering. Methods: Using example sub-stellar atmospheres from DRIFT-PHOENIX, we have compared plasma deposition and sputtering timescales to those from neutral gas-phase surface chemistry to ascertain their regimes of influence. We calculated the plasma sputtering yield and discuss the circumstances where plasma sputtering dominates over deposition. Results: Within the highest dust density cloud regions, plasma deposition and sputtering dominates over neutral gas-phase surface chemistry if the degree of ionisation is ≳10-4. Loosely bound grains with surface binding energies of the order of 0.1-1 eV are susceptible to destruction through plasma sputtering for feasible degrees of ionisation and electron temperatures; whereas, strong crystalline grains with binding energies of the order 10 eV are resistant to sputtering. Conclusions: The mathematical framework outlined sets the foundation for the inclusion of plasma deposition and plasma sputtering in global dust cloud formation models of sub-stellar atmospheres.

Dwarfs on a Low-Carbon Diet: Modelling the Chemically Peculiar Secondaries of CVs

NASA Astrophysics Data System (ADS)

Homeier, D.; Harrison, T. E.; Barman, T. S.; Howell, S. B.

2003-12-01

Secondary stars of cataclysmic variables show a variety of abundance anomalies that might be caused by deposition of CNO-processed material. We have calculated PHOENIX stellar atmosphere models for late-type stellar and substellar companions using chemical equilibrium compositions for a range of carbon-depleted and/or oxygen-enriched elemental abundances. We present comparisons of our models with medium-resolution IR spectra of CV secondaries, including the possibly substellar secondary of the EF Eridani system. LTE models of the K-band spectrum are consistent with a Teff in the brown dwarf range and show that the complete lack of CH4 and CO absorption features in this object requires a [C/Fe] ratio more than 2 dex below the solar value. We compare our models to temperature estimates from light curve analyses and present a first irradiated model of the secondary, that takes into account the effect of the impinging flux from the white dwarf primary. This project has been supported by grants from the National Science Foundation and the NASA NStars program.

Multi-wavelength Observations of Accreting Compact Objects

NASA Astrophysics Data System (ADS)

Hernandez Santisteban, Juan Venancio

2016-11-01

The study of compact binaries invokes core astrophysical concepts ranging from stellar and sub-stellar atmospheres and interiors, stellar and binary evolution to physics of accretion. All of these systems are hosts to a compact object a white dwarf, neutron star or black hole ???? which produces a wide variety of exotic and energetic phenomena across the full electromagnetic spectrum. In this thesis, I will make use of multi-wavelength observations ranging from far-ultraviolet to nearinfrared in order to investigate two main topics: a) the late evolution of cataclysmic variables, and b) the accreting state of transitional millisecond pulsars. Firstly, I analyse the Very Large Telescope X-Shooter time-resolved spectroscopy of the short orbital period cataclysmic variable, SDSS J1433+1011, in Chapter 2. The wide wavelength coverage allowed me to perform a detailed characterisation of the system, as well as a direct mass measurement of the brown dwarf companion. I show that the donor in SDSS J1433+1011 successfully transitioned from the stellar to sub-stellar regime, as predicted by evolutionary models. Further light-curve modelling allowed me to show that a low albedo as well as a low heat circulation efficiency is present in the atmosphere of the sub-stellar donor. In Chapter 3, I analyse data from large synoptic surveys, such as SDSS and PTF, to search for the predicted population of dead cataclysmic variables. Following the non-detection of dead CVs, I was able to estimate the space density (?0 < 2?10????5 pc????3) of this hidden population via a Monte Carlo simulation of the Galactic CV population. In Chapter 4, I present Hubble Space Telescope ultraviolet observations of the transitional millisecond pulsar PSR J1023+0038, during its latest accretion state. In combination with optical and near-infrared data, I show that a standard accretion disc does not reach the magnetosphere of the neutron star. Instead, the overall spectrum is consistent with a truncated disc at ? 2:3 ? 109 cm away from the compact object. Furthermore, the ultraviolet data shares remarkable similarities with the only accreting white dwarf in a propeller regime, AE Aqr. Finally, I summarise my results in Chapter 5 and provide future lines of research in accreting compact binaries based on this work.

ROTATION PERIODS OF YOUNG BROWN DWARFS: K2 SURVEY IN UPPER SCORPIUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scholz, Alexander; Kostov, Veselin; Jayawardhana, Ray

2015-08-20

We report rotational periods for 16 young brown dwarfs in the nearby Upper Scorpius association, based on 72 days of high-cadence, high-precision photometry from the Keplerspace telescope’s K2 mission. The periods range from a few hours to two days (plus one outlier at five days), with a median just above one day, confirming that brown dwarfs, except at the very youngest ages, are fast rotators. Interestingly, four of the slowest rotators in our sample exhibit mid-infrared excess emission from disks; at least two also show signs of disk eclipses and accretion in the light curves. Comparing these new periods withmore » those for two other young clusters and simple angular momentum evolution tracks, we find little or no rotational braking in brown dwarfs between 1–10 Myr, in contrast to low-mass stars. Our findings show that disk braking, while still at work, is inefficient in the substellar regime, thus providing an important constraint on the mass dependence of the braking mechanism.« less

Sedimentation Efficiency of Condensation Clouds in Substellar Atmospheres

NASA Astrophysics Data System (ADS)

Gao, Peter; Marley, Mark S.; Ackerman, Andrew S.

2018-03-01

Condensation clouds in substellar atmospheres have been widely inferred from spectra and photometric variability. Up until now, their horizontally averaged vertical distribution and mean particle size have been largely characterized using models, one of which is the eddy diffusion–sedimentation model from Ackerman and Marley that relies on a sedimentation efficiency parameter, f sed, to determine the vertical extent of clouds in the atmosphere. However, the physical processes controlling the vertical structure of clouds in substellar atmospheres are not well understood. In this work, we derive trends in f sed across a large range of eddy diffusivities (K zz ), gravities, material properties, and cloud formation pathways by fitting cloud distributions calculated by a more detailed cloud microphysics model. We find that f sed is dependent on K zz , but not gravity, when K zz is held constant. f sed is most sensitive to the nucleation rate of cloud particles, as determined by material properties like surface energy and molecular weight. High surface energy materials form fewer, larger cloud particles, leading to large f sed (>1), and vice versa for materials with low surface energy. For cloud formation via heterogeneous nucleation, f sed is sensitive to the condensation nuclei flux and radius, connecting cloud formation in substellar atmospheres to the objects’ formation environments and other atmospheric aerosols. These insights could lead to improved cloud models that help us better understand substellar atmospheres. For example, we demonstrate that f sed could increase with increasing cloud base depth in an atmosphere, shedding light on the nature of the brown dwarf L/T transition.

Young Low-Mass Stars and Brown Dwarfs in IC 348

NASA Astrophysics Data System (ADS)

Luhman, K. L.

1999-11-01

I present new results from a continuing program to identify and characterize the low-mass stellar and substellar populations in the young cluster IC 348 (0.5-10 Myr). Optical spectroscopy has revealed young objects with spectral types as late as M8.25. The intrinsic J-H and H-K colors of these sources are dwarflike, whereas the R-I and I-J colors appear intermediate between the colors of dwarfs and giants. Furthermore, the spectra from 6500 to 9500 Å are reproduced well with averages of standard dwarf and giant spectra, suggesting that such averages should be used in the classification of young late-type sources. An H-R diagram is constructed for the low-mass population in IC 348 (K6-M8). The presumably coeval components of the young quadruple system GG Tau (White et al.) and the locus of stars in IC 348 are used as empirical isochrones to test the theoretical evolutionary models. The calculations of Burrows et al. do not appear to be consistent with the data at these earliest stages of stellar evolution. There is fair agreement between the data and the model isochrones of D'Antona & Mazzitelli, except near the hydrogen-burning limit. The agreement cannot be improved by changing the conversion between spectral types and effective temperatures. On the other hand, for the models of Baraffe et al., an adjustment of the temperature scale to progressively warmer temperatures at later M types, intermediate between dwarfs and giants, brings all components of GG Tau onto the same model isochrone and gives the population of IC 348 a constant age and age spread as a function of mass. When other observational constraints are considered, such as the dynamical masses of GM Aur, DM Tau, and GG Tau A, the models of Baraffe et al. are the most consistent with observations of young systems. With compatible temperature scales, the models of both D'Antona & Mazzitelli and Baraffe et al. suggest that the hydrogen-burning mass limit occurs near M6 at ages of <~10 Myr. Thus, several likely brown dwarfs are discovered in this study of IC 348, with masses down to ~20-30 MJ.

New White Dwarf-Brown Dwarf Binaries

NASA Astrophysics Data System (ADS)

Casewell, S. L.; Geier, S.; Lodieu, N.

2017-03-01

We present follow-up spectroscopy to 12 candidate white dwarf-brown dwarf binaries. We have confirmed that 8 objects do indeed have a white dwarf primary (7 DA, 1 DB) and two are hot subdwarfs. We have determined the Teff and log g for the white dwarfs and subdwarfs, and when combining these values with a model spectrum and the photometry, we have 3 probable white dwarf-substellar binaries with spectral types between M6 and L6.

Exploring the brown dwarf desert: new substellar companions from the SDSS-III MARVELS survey

NASA Astrophysics Data System (ADS)

Grieves, Nolan; Ge, Jian; Thomas, Neil; Ma, Bo; Sithajan, Sirinrat; Ghezzi, Luan; Kimock, Ben; Willis, Kevin; De Lee, Nathan; Lee, Brian; Fleming, Scott W.; Agol, Eric; Troup, Nicholas; Paegert, Martin; Schneider, Donald P.; Stassun, Keivan; Varosi, Frank; Zhao, Bo; Jian, Liu; Li, Rui; Porto de Mello, Gustavo F.; Bizyaev, Dmitry; Pan, Kaike; Dutra-Ferreira, Letícia; Lorenzo-Oliveira, Diego; Santiago, Basílio X.; da Costa, Luiz N.; Maia, Marcio A. G.; Ogando, Ricardo L. C.; del Peloso, E. F.

2017-06-01

Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ˜5 au in the mass range of ˜10-80 MJup. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New substellar companions in this region help assess the reality of the desert and provide insight to the formation and evolution of these objects. Here, we present 10 new brown dwarf and 2 low-mass stellar companion candidates around solar-type stars from the Multi-object APO Radial Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III. These companions were selected from processed MARVELS data using the latest University of Florida Two Dimensional pipeline, which shows significant improvement and reduction of systematic errors over previous pipelines. The 10 brown dwarf companions range in mass from ˜13 to 76 MJup and have orbital radii of less than 1 au. The two stellar companions have minimum masses of ˜98 and 100 MJup. The host stars of the MARVELS brown dwarf sample have a mean metallicity of [Fe/H] = 0.03 ± 0.08 dex. Given our stellar sample we estimate the brown dwarf occurrence rate around solar-type stars with periods less than ˜300 d to be ˜0.56 per cent.

A SUBSTELLAR COMMON PROPER-MOTION COMPANION TO THE PLEIAD H II 1348

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geissler, Kerstin; Metchev, Stanimir A.; Pham, Alfonse

2012-02-10

We announce the identification of a proper-motion companion to the star H II 1348, a K5 V member of the Pleiades open cluster. The existence of a faint point source 1.''1 away from H II 1348 was previously known from adaptive optics imaging by Bouvier et al. However, because of a high likelihood of background star contamination and in the absence of follow-up astrometry, Bouvier et al. tentatively concluded that the candidate companion was not physically associated with H II 1348. We establish the proper-motion association of the pair from adaptive optics imaging with the Palomar 5 m telescope. Adaptivemore » optics spectroscopy with the integral field spectrograph OSIRIS on the Keck 10 m telescope reveals that the companion has a spectral type of M8 {+-} 1. According to substellar evolution models, the M8 spectral type resides within the substellar mass regime at the age of the Pleiades. The primary itself is a known double-lined spectroscopic binary, which makes the resolved companion, H II 1348B, the least massive and widest component of this hierarchical triple system and the first substellar companion to a stellar primary in the Pleiades.« less

The Orion Nebula Cluster as a Paradigm of Star Formation

NASA Astrophysics Data System (ADS)

Robberto, Massimo

2014-10-01

We propose a 52-orbit Treasury Program to investigate two fundamental questions of star formation: a) the low-mass tail of the IMF, down to a few Jupiter masses; b) the dynamical evolution of clusters, as revealed by stellar proper motions. We target the Orion Nebula Cluster (ONC) using WFC3 and ACS in coordinated parallel mode to perform a synoptic survey in the 1.345micron H2O feature and Ic broad-band. Our main objectives are: 1) to discover and classify ~500 brown dwarfs and planetary-mass objects in the field, extending the IMF down to lowest masses formed by gravitational collapse. Using the latest generation of high contrast image processing we will also search for faint companions, reaching down to sub-arcsecond separations and 1E-4 flux ratios. 2) to derive high precision (~0.2km/s) relative proper motions of low-mass stars and substellar objects (about 1000 sources total), leveraging on first epoch data obtained by our previous HST Treasury Program about 10 years ago. These data will unveil the cluster dynamics: velocity dispersion vs. mass, substructures, and the fraction of escaping sources. Only HST can access the IR H2O absorption feature sensitive to the effective temperature of substellar objects, while providing the exceptionally stable PSF needed for the detection of faint companions, and the identical ACS platform for our second epoch proper-motion survey. This program will provide the definitive HST legacy dataset on the ONC. Our High-Level Science Products will be mined by the community, both statistically to constrain competing theories of star formation, and to study in depth the multitude of exotic sources harboured by the cluster.

Precision Photometric Monitoring of Young Low-mass Stars and Brown Dwarfs: Shedding Light on Rotation, Pulsation, and the Star-disk Connection

NASA Astrophysics Data System (ADS)

Cody, Ann Marie; Hillenbrand, L. A.

2010-01-01

Young star-forming regions are host to a variety of optically variable sources, from accreting and flaring stars to those whose light is modulated by surface spots. In addition, recent theory has suggested that a new type of variability-- pulsation powered by deuterium burning-- may be at work on hour timescales in young brown dwarfs and very low mass stars. Photometric studies of these diverse phenomena are key in probing the underlying physics governing the evolution of few-Myr-old cluster members. High-cadence time series provide insight into not only the stochastic nature of accretion, but also trends in rotation via monitoring of magnetic surface spots. Nevertheless, a complete characterization of variability down to low amplitudes, and particularly amongst very-low-mass (0.01-0.3 M⊙) objects, remains elusive. The lower limit to rotation periods in young clusters is not well established, and mechanisms regulating angular momentum down through the substellar regime are not well understood. To expand the census of variability to very low mass and short timescales, as well as assess the possibility of deuterium-burning pulsation, we have carried out a dedicated monitoring campaign on confirmed low-mass members in several 2-5 Myr clusters. Using meter-class telescopes, our survey achieves sensitivity to periodic variations with photometric amplitudes down to the millimagnitude level on timescales ranging from a fraction of an hour to several weeks. We present results from the 5 Myr Sigma Orionis cluster, including a new compilation of rotation rates and a strong correspondence between variability type and presence of a disk, as indicated by Spitzer/IRAC excesses. In contrast to previous reports of 1-4-hour variability amongst brown dwarfs, we find a dearth of periods under 10 hours. However, we identify a significant positive correlation between rotation period and mass.

The Impact of Clouds and Hazes in Substellar Atmospheres

NASA Astrophysics Data System (ADS)

Morley, Caroline; Fortney, Jonathan J.; Marley, Mark S.

2016-01-01

The formation of clouds significantly alters the spectra of cool substellar atmospheres from terrestrial planets to brown dwarfs. In cool planets like Earth and Jupiter, volatile species like water and ammonia condense to form ice clouds. In hot planets and brown dwarfs, iron and silicates instead condense, forming dusty clouds. Irradiated methane-rich planets may have substantial hydrocarbon hazes. During my thesis, I have studied the impact of clouds and hazes in a variety of substellar objects. First, I present results for cool brown dwarfs including clouds previously neglected in model atmospheres. Model spectra that include sulfide and salt clouds can match the spectra of T dwarf atmospheres; water ice clouds will alter the spectra of the newest and coldest brown dwarfs, the Y dwarfs. These sulfide/salt and ice clouds potentially drive spectroscopic variability in these cool objects, and this variability should be distinguishable from variability caused by hot spots.Next, I present results for small, cool exoplanets between the size of Earth and Neptune, so-called super Earths. They likely have sulfide and salt clouds and also have photochemical hazes caused by stellar irradiation. Vast resources have been dedicated to characterizing the handful of super Earths accessible to current telescopes, yet of the planets smaller than Neptune studied to date, all have radii in the near-infrared consistent with being constant in wavelength, likely showing that these small planets are consistently enshrouded in thick hazes and clouds. Very thick, lofted clouds of salts or sulfides in high metallicity (1000× solar) atmospheres create featureless transmission spectra in the near-infrared. Photochemical hazes with a range of particle sizes also create featureless transmission spectra at lower metallicities. I show that despite these challenges, there are promising avenues for understanding this class of small planets: by observing the thermal emission and reflectivity of small planets, we can break the degeneracies and better constrain the atmospheric compositions. These observations may provide rich diagnostics of molecules and clouds in small planets, in contrast to the limited success to date.

The Scorched Atmosphere of a Low Mass Star

NASA Astrophysics Data System (ADS)

Hines, Dean; Schmidt, Gary

2006-05-01

The recent detection of mid-IR emission from the brown dwarf companion to the white dwarf GD1400 (Farihi & Christopher 2005) demonstrates the power of IRAC for characterizing low-mass companions to white dwarf (WD) stars. Compared with GD1400, the close binary system SDSS121209.31+013627.7 (hereafter SDSS1212) is potentially a far more significant target in this effort. SDSS1212 consists of a magnetic WD plus a low-mass companion in a very close (tidally-locked) orbit (a ~ 0.6 Rsun, P ~ 90 mins). The companion shows the effects of irradiation of its atmosphere by the WD, and the tidal lock (and inclination) ensures that we view the illuminated and far-side hemispheres during each orbit. Ground-based, J-band upper limits constrain the companion to be a late-type brown dwarf (L5 or later). Thus, SDSS1212 is an ideal system for studying the atmosphere of a sub-stellar object heated by a strong continuum. Indeed, the total irradiating flux at ~1 Rsun from a T ~ 10,000K WD is comparable to that at r ~ 0.1 AU from a sun-like main sequence star, and SDSS1212 is the only WD + brown dwarf binary whose orbital period is known. Given its importance for the characterization of planetary atmosphere and binary star evolution, we propose to carry out phase-resolved 3.6?8 micron imaging of the SDSS1212 system with the dual goals of: 1) characterizing the orbit-averaged photometric properties of the low-mass companion, and thus discerning its placement within the ever-expanding zoo of substellar objects; and 2) measuring what is expected to be a modulation of up to 0.4 mag in the net mid-IR brightness of the binary, thereby providing an empirical point of comparison for current theoretical efforts to predict the response of "hot Jupiters" to irradiation by their parent stars. Coupled with the exquisite photometric stability of IRAC and the benign environment of Spitzer, this unique target offers an exceptional opportunity to study the effects of irradiation from host stars on their substellar companions.

Radio emission in ultracool dwarfs: The nearby substellar triple system VHS 1256-1257

NASA Astrophysics Data System (ADS)

Guirado, J. C.; Azulay, R.; Gauza, B.; Pérez-Torres, M. A.; Rebolo, R.; Climent, J. B.; Zapatero Osorio, M. R.

2018-02-01

Aim. With the purpose of investigating the radio emission of new ultracool objects, we carried out a targeted search in the recently discovered system VHS J125601.92-125723.9 (hereafter VHS 1256-1257); this system is composed by an equal-mass M7.5 binary and a L7 low-mass substellar object located at only 15.8 pc. Methods: We observed in phase-reference mode the system VHS 1256-1257 with the Karl G. Jansky Very Large Array at X band and L band and with the European VLBI Network at L band in several epochs during 2015 and 2016. Results: We discovered radio emission at X band spatially coincident with the equal-mass M7.5 binary with a flux density of 60 μJy. We determined a spectral index α = ‑1.1 ± 0.3 between 8 and 12 GHz, suggesting that non-thermal, optically thin, synchrotron, or gyrosynchrotron radiation is responsible for the observed radio emission. Interestingly, no signal is seen at L band where we set a 3σ upper limit of 20 μJy. This might be explained by strong variability of the binary or self-absorption at this frequency. By adopting the latter scenario and gyrosynchrotron radiation, we constrain the turnover frequency to be in the interval 5-8.5 GHz, from which we infer the presence of kG-intense magnetic fields in the M7.5 binary. Our data impose a 3σ upper bound to the radio flux density of the L7 object of 9 μJy at 10 GHz.

STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang Jun; Abbot, Dorian S.; Cowan, Nicolas B., E-mail: abbot@uchicago.edu

2013-07-10

The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies.more » This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phenomenon a stabilizing climate feedback. Substellar clouds also effectively block outgoing radiation from the surface, reducing or even completely reversing the thermal emission contrast between dayside and nightside. The presence of substellar water clouds and the resulting clement surface conditions will therefore be detectable with the James Webb Space Telescope.« less

An ALMA and MagAO Study of the Substellar Companion GQ Lup B*

NASA Astrophysics Data System (ADS)

Wu, Ya-Lin; Sheehan, Patrick D.; Males, Jared R.; Close, Laird M.; Morzinski, Katie M.; Teske, Johanna K.; Haug-Baltzell, Asher; Merchant, Nirav; Lyons, Eric

2017-02-01

Multi-wavelength observations provide a complementary view of the formation of young, directly imaged planet-mass companions. We report the ALMA 1.3 mm and Magellan adaptive optics Hα, I\\prime , z\\prime , and Y S observations of the GQ Lup system, a classical T Tauri star with a 10{--}40 {M}{Jup} substellar companion at ˜110 au projected separation. We estimate the accretion rates for both components from the observed Hα fluxes. In our ˜0.″05 resolution ALMA map, we resolve GQ Lup A’s disk in the dust continuum, but no signal is found from the companion. The disk is compact, with a radius of ˜22 au, a dust mass of ˜6 M ⊕, an inclination angle of ˜56°, and a very flat surface density profile indicative of a radial variation in dust grain sizes. No gaps or inner cavity are found in the disk, so there is unlikely a massive inner companion to scatter GQ Lup B outward. Thus, GQ Lup B might have formed in situ via disk fragmentation or prestellar core collapse. We also show that GQ Lup A’s disk is misaligned with its spin axis, and possibly with GQ Lup B’s orbit. Our analysis on the tidal truncation radius of GQ Lup A’s disk suggests that GQ Lup B’s orbit might have a low eccentricity. This paper includes data gathered with the 6.5 m Magellan Clay Telescope at Las Campanas Observatory, Chile.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bacciotti, F.; Randich, S.; Whelan, E. T.

We present the first pilot study of jets from young stars conducted with X-shooter, on the ESO/Very Large Telescope. As it offers simultaneous, high-quality spectra in the range 300-2500 nm, X-shooter is uniquely important for spectral diagnostics in jet studies. We chose to probe the accretion/ejection mechanisms at low stellar masses examining two targets with well-resolved continuous jets lying on the plane of the sky: ESO-HA 574 in Chameleon I and Par-Lup3-4 in Lupus III. The mass of the latter is close to the sub-stellar boundary (M{sub *} = 0.13 M{sub sun}). A large number of emission lines probing regionsmore » of different excitation are identified, position-velocity diagrams are presented, and mass outflow/accretion rates are estimated. Comparison between the two objects is striking. ESO-HA 574 is a weakly accreting star for which we estimate a mass accretion rate of log ( M-dot{sub acc}) = -10.8{+-}0.5 (in M{sub sun} yr{sup -1}), yet it drives a powerful jet with M-dot{sub out} {approx} 1.5-2.7 x 10{sup -9} M{sub sun} yr{sup -1}. These values can be reconciled with a magneto-centrifugal jet acceleration mechanism assuming that the presence of the edge-on disk severely depresses the luminosity of the accretion tracers. In comparison, Par-Lup3-4, with stronger mass accretion ( log ( M-dot{sub acc}) = -9.1{+-}0.4 M{sub sun} yr{sup -1}), drives a low-excitation jet with about M-dot{sub out} {approx} 3.2 x 10{sup -10} M{sub sun} yr{sup -1} in both lobes. Despite the low stellar mass, M-dot{sub out}/ M-dot{sub acc} for Par-Lup3-4 is at the upper limit of the range usually measured for young objects, but still compatible with a steady magneto-centrifugal wind scenario if all uncertainties are considered.« less

High Contrast Imaging with NICMOS - I: Teaching an Old Dog New Tricks with Coronagraphic Polarimetry

NASA Astrophysics Data System (ADS)

Schneider, G.; Hines, D. C.

2007-06-01

HST's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), with its highly stable point spread function, very high imaging Strehl ratio (panchromatically > 98% over its entire 0.8 - 2.4 micron wavelength regime) and coronagraphic imaging capability, celebrated its tenth anniversary in space earlier this year. These combined instrumental attributes uniquely contribute to its capability as a high-contrast imager as demonstrated by its continuing production of new examples of spatially resolved scattered-light imagery of both optically thick and thin circumstellar disks and sub-stellar companions to young stars and brown dwarfs well into the (several) Jovian mass range. We review these capabilities, illustrating with observationally based results, including examples obtained since HST's entry into two gyro guiding mode in mid 2005. The advent of a recently introduced, and now commissioned and calibrated, coronagraphic polarimetry mode has enabled very-high contrast 2 micron imaging polarimetry with 0.2 spatial resolution. Such imagery provides important constraints in the interpretation of disk-scattered starlight in assessing circumstellar disk geometries and the physical properties of their constituent grains. We demonstrate this new capability with observational results from two currently-executing HST programs obtaining 2 micron coronagraphic polarimetric images of circumstellar T-Tauri and debris disks.

Spectroscopic Confirmation of Young Planetary-mass Companions on Wide Orbits

NASA Astrophysics Data System (ADS)

Bowler, Brendan P.; Liu, Michael C.; Kraus, Adam L.; Mann, Andrew W.

2014-03-01

We present moderate-resolution (R ~ 4000-5000) near-infrared integral field spectroscopy of the young (1-5 Myr) 6-14 M Jup companions ROXs 42B b and FW Tau b obtained with Keck/OSIRIS and Gemini-North/NIFS. The spectrum of ROXs 42B b exhibits clear signs of low surface gravity common to young L dwarfs, confirming its extreme youth, cool temperature, and low mass. Overall, it closely resembles the free-floating 4-7 M Jup L-type Taurus member 2MASS J04373705+2331080. The companion to FW Tau AB is more enigmatic. Our optical and near-infrared spectra show strong evidence of outflow activity and disk accretion in the form of line emission from [S II], [O I], Hα, Ca II, [Fe II], Paβ, and H2. The molecular hydrogen emission is spatially resolved as a single lobe that stretches ≈0.''1 (15 AU). Although the extended emission is not kinematically resolved in our data, its morphology resembles shock-excited H2 jets primarily seen in young Class 0 and Class I sources. The near-infrared continuum of FW Tau b is mostly flat and lacks the deep absorption features expected for a cool, late-type object. This may be a result of accretion-induced veiling, especially in light of its strong and sustained Hα emission (EW(Hα) >~ 290 Å). Alternatively, FW Tau b may be a slightly warmer (M5-M8) accreting low-mass star or brown dwarf (0.03-0.15 M ⊙) with an edge-on disk. Regardless, its young evolutionary stage is in stark contrast to its Class III host FW Tau AB, indicating a more rapid disk clearing timescale for the host binary system than for its wide companion. Finally, we present near-infrared spectra of the young (~2-10 Myr) low-mass (12-15 M Jup) companions GSC 6214-210 B and SR 12 C and find they best resemble low-gravity M9.5 and M9 substellar templates. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Very Low-mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. VI. A Giant Planet and a Brown Dwarf Candidate in a Close Binary System HD 87646

NASA Astrophysics Data System (ADS)

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

2016-11-01

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 system, HD 87646. To the best of our knowledge, it is the first close binary system 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 system is stable if the binary orbit has a large semimajor axis and a low eccentricity, which can be verified with future astrometry observations.

The Optical Gravitational Lensing Experiment. Additional Planetary and Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational Campaigns

NASA Astrophysics Data System (ADS)

Udalski, A.; Pietrzynski, G.; Szymanski, M.; Kubiak, M.; Zebrun, K.; Soszynski, I.; Szewczyk, O.; Wyrzykowski, L.

2003-06-01

The photometric data collected by OGLE-III during the 2001 and 2002 observational campaigns aiming at detection of planetary or low-luminosity object transits were corrected for small scale systematic effects using the data pipeline by Kruszewski and Semeniuk and searched again for low amplitude transits. Sixteen new objects with small transiting companions, additional to previously found samples, were discovered. Most of them are small amplitude cases which remained undetected in the original data. Several new objects seem to be very promising candidates for systems containing substellar objects: extrasolar planets or brown dwarfs. Those include OGLE-TR-122, OGLE-TR-125, OGLE-TR-130, OGLE-TR-131 and a few others. Those objects are particularly worth spectroscopic follow-up observations for radial velocity measurements and mass determination. With well known photometric orbit only a few RV measurements should allow to confirm their actual status. All photometric data of presented objects are available to the astronomical community from the OGLE Internet archive.

The carbonate-silicate cycle and CO2/climate feedbacks on tidally locked terrestrial planets.

PubMed

Edson, Adam R; Kasting, James F; Pollard, David; Lee, Sukyoung; Bannon, Peter R

2012-06-01

Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.

The Widest-separation Substellar Companion Candidate to a Binary T Tauri Star

NASA Astrophysics Data System (ADS)

Kuzuhara, M.; Tamura, M.; Ishii, M.; Kudo, T.; Nishiyama, S.; Kandori, R.

2011-04-01

The results of near-infrared imaging and spectroscopy of a substellar companion (SR12 C), with a possible planetary mass, of a binary T Tauri star (SR12 AB) in the ρ Ophiuchi star-forming region are presented. The object is separated by ~8farcs7, corresponding to ~1100 AU at 125 pc, and has an H-band brightness of 15.2 mag and infrared spectra suggesting a spectral type of M9.0 ± 0.5. It is confirmed that SR12 C is physically related to the ρ Ophiuchi star-forming region from its common proper motion with SR12 AB and its youth is confirmed by a gravity-sensitive spectral feature. Furthermore, based on the number of known members of the ρ Ophiuchi star-forming region in the area in which SR12 AB exists, the probability of a chance alignment is ~1% and it is therefore likely that SR12 C is physically associated with SR12 AB. The mass of SR12 C is estimated by comparing its estimated luminosity and assumed age with the theoretical age-luminosity relation. SR12 C is identified as an extremely low-mass (0.013 ± 0.007 M sun) object, but its separation from its parent star is the widest among planetary-mass companion (PMC) candidates imaged to date. In addition, SR12 C is the first PMC candidate directly imaged around a binary star. This discovery suggests that PMCs form via multiple star formation processes including disk gravitational instability and cloud core fragmentation.

ALMA Measurements of Circumstellar Material in the GQ Lup System

NASA Astrophysics Data System (ADS)

MacGregor, Meredith A.; Wilner, David J.; Czekala, Ian; Andrews, Sean M.; Dai, Y. Sophia; Herczeg, Gregory J.; Kratter, Kaitlin M.; Kraus, Adam L.; Ricci, Luca; Testi, Leonardo

2017-01-01

We present Atacama Large Millimeter/submillimeter Array observations of the GQ Lup system, a young Sun-like star with a substellar-mass companion in a wide-separation orbit. These observations of 870 μm continuum and CO J = 3-2 line emission with beam size ˜0.″3 (˜45 au) resolve the disk of dust and gas surrounding the primary star, GQ Lup A, and provide deep limits on any circumplanetary disk surrounding the companion, GQ Lup b. The circumprimary dust disk is compact with an FWHM of 59 ± 12 au, while the gas has a larger extent with a characteristic radius of 46.5 ± 1.8 au. By forward-modeling the velocity field of the circumprimary disk based on the CO emission, we constrain the mass of GQ Lup A to be M* = (1.03 ± 0.05) ∗ (d/156 pc) M⊙, where d is a known distance, and determine that we view the disk at an inclination angle of 60.°5 ± 0.°5 and a position angle of 346° ± 1°. The 3σ upper limit on the 870 μm flux density of any circumplanetary disk associated with GQ Lup b of <0.15 mJy implies an upper limit on the dust disk mass of <0.04 M⊕ for standard assumptions about optically thin emission. We discuss proposed mechanisms for the formation of wide-separation substellar companions given the non-detection of circumplanetary disks around GQ Lup b and other similar systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geier, S.; Schaffenroth, V.; Drechsel, H.

Hot subdwarf B stars (sdBs) are extreme horizontal branch stars believed to originate from close binary evolution. Indeed about half of the known sdB stars are found in close binaries with periods ranging from a few hours to a few days. The enormous mass loss required to remove the hydrogen envelope of the red-giant progenitor almost entirely can be explained by common envelope ejection. A rare subclass of these binaries are the eclipsing HW Vir binaries where the sdB is orbited by a dwarf M star. Here, we report the discovery of an HW Vir system in the course ofmore » the MUCHFUSS project. A most likely substellar object ({approx_equal}0.068 M{sub sun}) was found to orbit the hot subdwarf J08205+0008 with a period of 0.096 days. Since the eclipses are total, the system parameters are very well constrained. J08205+0008 has the lowest unambiguously measured companion mass yet found in a subdwarf B binary. This implies that the most likely substellar companion has not only survived the engulfment by the red-giant envelope, but also triggered its ejection and enabled the sdB star to form. The system provides evidence that brown dwarfs may indeed be able to significantly affect late stellar evolution.« less

A low-temperature companion to a white dwarf star

NASA Technical Reports Server (NTRS)

Becklin, E. E.; Zuckerman, B.

1988-01-01

An infrared object located about 120 AU from the white dwarf GD165 has been discovered. With the exception of the possible brown dwarf companion to Giclas 29-38 reported last year, the companion to GD165 is the coolest (2100 K) dwarf star ever reported and, according to some theoretical models, it should be a substellar brown dwarf with a mass between 0.06 and 0.08 solar mass. These results, together with newly discovered low-mass stellar companions to white dwarfs, change the investigation of very low-mass stars from the study of a few chance objects to that of a statistical distribution. In particular, it appears that very low-mass stars and perhaps even brown dwarfs could be quite common in the Galaxy.

Understanding the Atmosphere of 51 Eri b: Do Photochemical Hazes Cloud the Planets Spectrum?

NASA Technical Reports Server (NTRS)

Marley, Mark Scott; Zahnle, Kevin; Moses, J.; Morley, C.

2015-01-01

The first young giant planet to be discovered by the Gemini Planet Imager was the (is) approximately 2MJ planet 51 Eri b. This approximately 20 Myr old young Jupiter is the first directly imaged planet to show unmistakable methane in H band. To constrain the planet's mass, atmospheric temperature, and composition, the GPI J and H band spectra as well as some limited photometric points were compared to the predictions of substellar atmosphere models. The best fitting models reported in the discovery paper (Macintosh et al. 2015) relied upon a combination of clear and cloudy atmospheric columns to reproduce the data. However for an object as cool as 700 K, the origin of the cloud coverage is somewhat puzzling, as the global silicate and iron clouds would be expected to have sunk well below the photosphere by this effective temperature. While strong vertical mixing in these low gravity atmospheres remains a plausible explanation, we have explored whether atmospheric photochemistry, driven by the UV flux from the primary star, may yield hazes that also influence the observed spectrum of the planet. To explore this possibility we have modeled the atmospheric photochemistry of 51 Eri b using two state-of-the-art photochemical models, both capable of predicting yields of complex hydrocarbons under various atmospheric conditions. In our presentation we will summarize the modeling approach employed to characterize 51 Eri b, explaining constraints on the planet's effective temperature, gravity, and atmospheric composition and also present results of our studies of atmospheric photochemistry. We will discuss whether photochemical hazes could indeed be responsible for the particulate opacity that apparently sculpts the spectrum of the planet.

A Palette of Climates for Gliese 581g

NASA Astrophysics Data System (ADS)

Pierrehumbert, R. T.

2011-01-01

We consider a range of possible climates for the habitable-zone planet candidate, Gliese 581g, contingent on a plausible set of hypothetical atmospheres and assuming the planet to be tide locked. The two most habitable states we find are (1) a nearly airless Super-Europa with thin ice at the substellar point and (2) an "Eyeball Earth" which is mostly frozen but supports a substantial stable pool of open water centered on the substellar point. We discuss the prospects for observational determination of what kind of climate 581g actually supports.

Filaments in Lupus I

NASA Astrophysics Data System (ADS)

Takahashi, Satoko; Rodon, J.; De Gregorio-Monsalvo, I.; Plunkett, A.

2017-06-01

The mechanisms behind the formation of sub-stellar mass sources are key to determine the populations at the low-mass end of the stellar distribution. Here, we present mapping observations toward the Lupus I cloud in C18O(2-1) and 13CO(2-1) obtained with APEX. We have identified a few velocity-coherent filaments. Each contains several substellar mass sources that are also identified in the 1.1mm continuum data (see also SOLA catalogue presentation). We will discuss the velocity structure, fragmentation properties of the identified filaments, and the nature of the detected sources.

A PALETTE OF CLIMATES FOR GLIESE 581g

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierrehumbert, R. T., E-mail: rtp1@geosci.uchicago.edu

2011-01-01

We consider a range of possible climates for the habitable-zone planet candidate, Gliese 581g, contingent on a plausible set of hypothetical atmospheres and assuming the planet to be tide locked. The two most habitable states we find are (1) a nearly airless Super-Europa with thin ice at the substellar point and (2) an 'Eyeball Earth' which is mostly frozen but supports a substantial stable pool of open water centered on the substellar point. We discuss the prospects for observational determination of what kind of climate 581g actually supports.

A Universal Spin–Mass Relation for Brown Dwarfs and Planets

NASA Astrophysics Data System (ADS)

Scholz, Aleks; Moore, Keavin; Jayawardhana, Ray; Aigrain, Suzanne; Peterson, Dawn; Stelzer, Beate

2018-06-01

While brown dwarfs show similarities to stars early in their lives, their spin evolutions are much more akin to those of planets. We have used light curves from the K2 mission to measure new rotation periods for 18 young brown dwarfs in the Taurus star-forming region. Our sample spans masses from 0.02 to 0.08 M ⊙ and has been characterized extensively in the past. To search for periods, we utilize three different methods (autocorrelation, periodogram, Gaussian processes). The median period for brown dwarfs with disks is twice as long as for those without (3.1 versus 1.6 days), a signature of rotational braking by the disk, albeit with small numbers. With an overall median period of 1.9 days, brown dwarfs in Taurus rotate slower than their counterparts in somewhat older (3–10 Myr) star-forming regions, consistent with spin-up of the latter due to contraction and angular momentum conservation, a clear sign that disk braking overall is inefficient and/or temporary in this mass domain. We confirm the presence of a linear increase of the typical rotation period as a function of mass in the substellar regime. The rotational velocities, when calculated forward to the age of the solar system, assuming angular momentum conservation, fit the known spin–mass relation for solar system planets and extra-solar planetary-mass objects. This spin–mass trend holds over six orders of magnitude in mass, including objects from several different formation paths. Our result implies that brown dwarfs by and large retain their primordial angular momentum through the first few Myr of their evolution.

A Multiplicity Census of Young Stars in Chamaeleon I

NASA Astrophysics Data System (ADS)

Lafrenière, David; Jayawardhana, Ray; Brandeker, Alexis; Ahmic, Mirza; van Kerkwijk, Marten H.

2008-08-01

We present the results of a multiplicity survey of 126 stars spanning ~0.1-3 M⊙ in the ~2 Myr old Chamaeleon I star-forming region, based on adaptive optics imaging with the ESO Very Large Telescope. Our observations have revealed 30 binaries and six triples, of which 19 and four, respectively, are new discoveries. The overall multiplicity fraction we find for Cha I (~30%) is similar to those reported for other dispersed young associations, but significantly higher than seen in denser clusters and the field, for comparable samples. Both the frequency and the maximum separation of Cha I binaries decline with decreasing mass, while the mass ratios approach unity; conversely, tighter pairs are more likely to be equal mass. We confirm that brown dwarf companions to stars are rare, even at young ages at wide separations. Based on follow-up spectroscopy of two low-mass substellar companion candidates, we conclude that both are likely background stars. The overall multiplicity fraction in Cha I is in rough agreement with numerical simulations of cloud collapse and fragmentation, but its observed mass dependence is less steep than predicted. The paucity of higher order multiples, in particular, provides a stringent constraint on the simulations, and seems to indicate a low level of turbulence in the prestellar cores in Cha I.

The SOLA Team: A Star Formation Project To Study the Soul of Lupus with ALMA

NASA Astrophysics Data System (ADS)

De Gregorio-Monsalvo, Itziar; Saito, M.; Rodon, J.; Takahashi, S.

2017-06-01

The SOLA team is a multi-national and multi-wavelength collaboration composed by scientists with technical expertise in ALMA and in infrared and optical techniques. The aim of the team is to establish a low-mass star formation scenario based on the Lupus molecular clouds. In this talk I will present our unique catalog of pre-stellar and proto-stellar cores toward Lupus molecular clouds, the results on our latest studies in protoplanetary disks, as well as our ALMA Cycle 3 data aiming at testing the formation mechanism of sub-stellar objects in Lupus molecular clouds.

Reviews in Modern Astronomy: Vol. 16: The Cosmic Circuit of Matter

NASA Astrophysics Data System (ADS)

Schielicke, Reinhard E.

2003-08-01

The 16th volume in the annual series on recent developments and scientific progress in astronomy and astrophysics contains thirteen invited reviews presented during the International Scientific Conference of the Society on "The Cosmic Circuit of Matter", held in Berlin, Germany. Readers also learn about the lecture on the behaviour of stars by infrared interferometry given by Charles H. Townes, Berkeley, USA who was awarded the Karl Schwarzschild medal 2002. Further contributions on the topic provide, among other, the latest results on the Solar atmosphere, formation of stars, substellar objects, galaxies and clusters of galaxies.

Possible Observational Criteria for Distinguishing Brown Dwarfs From Planets

NASA Technical Reports Server (NTRS)

Black, David C.

1997-01-01

The difference in formation process between binary stars and planetary systems is reflected in their composition, as well as orbital architecture, particularly in their orbital eccentricity as a function of orbital period. It is suggested here that this difference can be used as an observational criterion to distinguish between brown dwarfs and planets. Application of the orbital criterion suggests that, with three possible exceptions, all of the recently discovered substellar companions may be brown dwarfs and not planets. These criterion may be used as a guide for interpretation of the nature of substellar-mass companions to stars in the future.

Finding new sub-stellar co-moving companion candidates - the case of CT Cha

NASA Astrophysics Data System (ADS)

Schmidt, Tobias; Neuhäuser, Ralph

2008-05-01

We have searched for close and faint companions around T Tauri stars in the Chamaeleon star forming region. Two epochs of direct imaging data were taken with the VLT Adaptive Optics instrument NaCo in February 2006 and March 2007 in Ks band for the classical T Tauri star CT Cha together with a Hipparcos binary for astrometric calibration. Moreover a J band image was taken in March 2007 to get color information. We found CT Cha to have a very faint companion (Ks0=14.6 mag) of 2.67” separation corresponding to 440AU. We show that CT Cha A and the faint object form a common proper motion pair and that the companion is not a non-moving background object (with 4σ significance).

QUENCHING OF CARBON MONOXIDE AND METHANE IN THE ATMOSPHERES OF COOL BROWN DWARFS AND HOT JUPITERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Visscher, Channon; Moses, Julianne I., E-mail: visscher@lpi.usra.edu, E-mail: jmoses@spacescience.org

We explore CO{r_reversible}CH{sub 4} quench kinetics in the atmospheres of substellar objects using updated timescale arguments, as suggested by a thermochemical kinetics and diffusion model that transitions from the thermochemical-equilibrium regime in the deep atmosphere to a quench-chemical regime at higher altitudes. More specifically, we examine CO quench chemistry on the T dwarf Gliese 229B and CH{sub 4} quench chemistry on the hot-Jupiter HD 189733b. We describe a method for correctly calculating reverse rate coefficients for chemical reactions, discuss the predominant pathways for CO{r_reversible}CH{sub 4} interconversion as indicated by the model, and demonstrate that a simple timescale approach can bemore » used to accurately describe the behavior of quenched species when updated reaction kinetics and mixing-length-scale assumptions are used. Proper treatment of quench kinetics has important implications for estimates of molecular abundances and/or vertical mixing rates in the atmospheres of substellar objects. Our model results indicate significantly higher K{sub zz} values than previously estimated near the CO quench level on Gliese 229B, whereas current-model-data comparisons using CH{sub 4} permit a wide range of K{sub zz} values on HD 189733b. We also use updated reaction kinetics to revise previous estimates of the Jovian water abundance, based upon the observed abundance and chemical behavior of carbon monoxide. The CO chemical/observational constraint, along with Galileo entry probe data, suggests a water abundance of approximately 0.51-2.6 x solar (for a solar value of H{sub 2}O/H{sub 2} = 9.61 x 10{sup -4}) in Jupiter's troposphere, assuming vertical mixing from the deep atmosphere is the only source of tropospheric CO.« less

IRAS 16253–2429: THE FIRST PROTO-BROWN DWARF BINARY CANDIDATE IDENTIFIED THROUGH THE DYNAMICS OF JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Tien-Hao; Lai, Shih-Ping; Belloche, Arnaud

2016-07-20

The formation mechanism of brown dwarfs (BDs) is one of the long-standing problems in star formation because the typical Jeans mass in molecular clouds is too large to form these substellar objects. To answer this question, it is crucial to study a BD in the embedded phase. IRAS 16253–2429 is classified as a very low-luminosity object (VeLLO) with an internal luminosity of <0.1 L {sub ⊙}. VeLLOs are believed to be very low-mass protostars or even proto-BDs. We observed the jet/outflow driven by IRAS 16253–2429 in CO (2–1), (6–5), and (7–6) using the IRAM 30 m and Atacama Pathfinder Experimentmore » telescopes and the Submillimeter Array (SMA) in order to study its dynamical features and physical properties. Our SMA map reveals two protostellar jets, indicating the existence of a proto-binary system as implied by the precessing jet detected in H{sub 2} emission. We detect a wiggling pattern in the position–velocity diagrams along the jet axes, which is likely due to the binary orbital motion. Based on this information, we derive the current mass of the binary as ∼0.032 M{sub ⊙}. Given the low envelope mass, IRAS 16253–2429 will form a binary that probably consist of one or two BDs. Furthermore, we found that the outflow force as well as the mass accretion rate are very low based on the multi-transition CO observations, which suggests that the final masses of the binary components are at the stellar/substellar boundary. Since IRAS 16253 is located in an isolated environment, we suggest that BDs can form through fragmentation and collapse, similar to low-mass stars.« less

The sub-stellar birth rate from UKIDSS

NASA Astrophysics Data System (ADS)

Day-Jones, A. C.; Marocco, F.; Pinfield, D. J.; Zhang, Z. H.; Burningham, B.; Deacon, N.; Ruiz, M. T.; Gallardo, J.; Jones, H. R. A.; Lucas, P. W. L.; Jenkins, J. S.; Gomes, J.; Folkes, S. L.; Clarke, J. R. A.

2013-04-01

We present a new sample of mid-L to mid-T dwarfs with effective temperatures of 1100-1700 K selected from the UKIDSS Large Area Survey (LAS) and confirmed with infrared spectra from X-shooter/Very Large Telescope. This effective temperature range is especially sensitive to the formation history of Galactic brown dwarfs and allows us to constrain the form of the sub-stellar birth rate, with sensitivity to differentiate between a flat (stellar like) birth rate and an exponentially declining form. We present the discovery of 63 new L and T dwarfs from the UKIDSS LAS DR7, including the identification of 12 likely unresolved binaries, which form the first complete sub-set from our programme, covering 495 square degrees of sky, complete to J = 18.1. We compare our results for this sub-sample with simulations of differing birth rates for objects of masses 0.10-0.03 M⊙ and ages 1-10 Gyr. We find that the more extreme birth rates (e.g. a halo type form) can likely be excluded as the true form of the birth rate. In addition, we find that although there is substantial scatter we find a preference for a mass function, with a power-law index α in the range -1 < α < 0 that is consistent (within the errors) with the studies of late T dwarfs.

The `DODO' survey - I. Limits on ultra-cool substellar and planetary-mass companions to van Maanen's star (vMa2)

NASA Astrophysics Data System (ADS)

Burleigh, M. R.; Clarke, F. J.; Hogan, E.; Brinkworth, C. S.; Bergeron, P.; Dufour, P.; Dobbie, P. D.; Levan, A. J.; Hodgkin, S. T.; Hoard, D. W.; Wachter, S.

2008-05-01

We report limits in the planetary-mass regime for companions around the nearest single white dwarf to the Sun, van Maanen's star (vMa2), from deep J-band imaging with Gemini North and Spitzer Infrared Array Camera (IRAC) mid-IR photometry. We find no resolved common proper motion companions to vMa2 at separations from 3 to 45 arcsec, at a limiting magnitude of J ~ 23. Assuming a total age for the system of 4.1 +/- 1Gyr, and utilizing the latest evolutionary models for substellar objects, this limit is equivalent to companion masses >7 +/- 1MJup(Teff ~ 300K). Taking into account the likely orbital evolution of very low mass companions in the post-main-sequence phase, these J-band observations effectively survey orbits around the white dwarf progenitor from 3 to 50au. There is no flux excess detected in any of the complimentary Spitzer IRAC mid-IR filters. We fit a white dwarf model atmosphere to the optical BVRI, JHK and IRAC photometry. The best solution gives Teff = 6030 +/- 240K, logg = 8.10 +/- 0.04 and, hence, M = 0.633 +/- 0.022Msolar. We then place a 3σ upper limit of 10 +/- 2MJup on the mass of any unresolved companion in the 4.5μm band.

The Thermal Phase Curve Offset on Tidally and Nontidally Locked Exoplanets: A Shallow Water Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penn, James; Vallis, Geoffrey K, E-mail: jp492@exeter.ac.uk, E-mail: g.vallis@exeter.ac.uk

2017-06-20

Using a shallow water model with time-dependent forcing, we show that the peak of an exoplanet thermal phase curve is, in general, offset from the secondary eclipse when the planet is rotating. That is, the planetary hot spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset are functions of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady state in the reference frame of the moving forcing. The model is an extension ofmore » the well-studied Matsuno–Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planet’s surface) exceeds that of the gravity waves, then the hot spot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wave speed of the system, the hottest point may lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics, as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.« less

Mapping the Substellar Mass-Luminosity Relation Down to the L/T Transition

NASA Astrophysics Data System (ADS)

Dupuy, Trent

2016-10-01

Substellar models underpin our theoretical understanding of brown dwarfs and gas-giant exoplanets, so assessing their accuracy is paramount. The past several years have seen progress in testing models thanks to a growing number of dynamical (total) masses for brown dwarf binaries determined via (relative) orbit monitoring from ground-based AO. However, the strongest tests of models require individual masses, particularly for calibrating the mass-luminosity relation. This is poorly constrained over the range of spectral types most influenced by clouds (mid-L to early-T). Given the observed prevalence of clouds in the atmospheres of directly imaged planets, testing models at such temperatures is crucial.We propose a 3-year program to obtain individual masses for a sample of 11 substellar binaries. Our proposal builds on nearly a decade of orbital monitoring from the ground to measure dynamical total masses. Our goal is thus to measure precise mass ratios, utilizing HST's unique wide-field, high-angular resolution astrometric capabilities. We will obtain WFC3-UVIS images capturing our targets and numerous reference stars so that we can measure the relative amount of orbital motion in each component to determine mass ratios. Three of our targets have I-band photocenter orbits measured at USNO and VLT and thus only require one epoch of resolved I-band imaging to unlock individual masses. We will use this first large sample of substellar individual masses to map out the mass-luminosity relation over a wide range of temperatures (1000-2000 K) including the L/T transition. This will become a touchstone sample for tests of ultracool atmospheric models in the era of JWST.

Mapping the Substellar Mass-Luminosity Relation Down to the L/T Transition

NASA Astrophysics Data System (ADS)

Dupuy, Trent

2017-08-01

Substellar models underpin our theoretical understanding of brown dwarfs and gas-giant exoplanets, so assessing their accuracy is paramount. The past several years have seen progress in testing models thanks to a growing number of dynamical (total) masses for brown dwarf binaries determined via (relative) orbit monitoring from ground-based AO. However, the strongest tests of models require individual masses, particularly for calibrating the mass-luminosity relation. This is poorly constrained over the range of spectral types most influenced by clouds (mid-L to early-T). Given the observed prevalence of clouds in the atmospheres of directly imaged planets, testing models at such temperatures is crucial.We propose a 3-year program to obtain individual masses for a sample of 11 substellar binaries. Our proposal builds on nearly a decade of orbital monitoring from the ground to measure dynamical total masses. Our goal is thus to measure precise mass ratios, utilizing HST's unique wide-field, high-angular resolution astrometric capabilities. We will obtain WFC3-UVIS images capturing our targets and numerous reference stars so that we can measure the relative amount of orbital motion in each component to determine mass ratios. Three of our targets have I-band photocenter orbits measured at USNO and VLT and thus only require one epoch of resolved I-band imaging to unlock individual masses. We will use this first large sample of substellar individual masses to map out the mass-luminosity relation over a wide range of temperatures (1000-2000 K) including the L/T transition. This will become a touchstone sample for tests of ultracool atmospheric models in the era of JWST.

A SEMI-ANALYTICAL MODEL OF VISIBLE-WAVELENGTH PHASE CURVES OF EXOPLANETS AND APPLICATIONS TO KEPLER- 7 B AND KEPLER- 10 B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Renyu; Demory, Brice-Olivier; Seager, Sara

2015-03-20

Kepler has detected numerous exoplanet transits by measuring stellar light in a single visible-wavelength band. In addition to detection, the precise photometry provides phase curves of exoplanets, which can be used to study the dynamic processes on these planets. However, the interpretation of these observations can be complicated by the fact that visible-wavelength phase curves can represent both thermal emission and scattering from the planets. Here we present a semi-analytical model framework that can be applied to study Kepler and future visible-wavelength phase curve observations of exoplanets. The model efficiently computes reflection and thermal emission components for both rocky andmore » gaseous planets, considering both homogeneous and inhomogeneous surfaces or atmospheres. We analyze the phase curves of the gaseous planet Kepler- 7 b and the rocky planet Kepler- 10 b using the model. In general, we find that a hot exoplanet’s visible-wavelength phase curve having a significant phase offset can usually be explained by two classes of solutions: one class requires a thermal hot spot shifted to one side of the substellar point, and the other class requires reflective clouds concentrated on the same side of the substellar point. Particularly for Kepler- 7 b, reflective clouds located on the west side of the substellar point can best explain its phase curve. The reflectivity of the clear part of the atmosphere should be less than 7% and that of the cloudy part should be greater than 80%, and the cloud boundary should be located at 11° ± 3° to the west of the substellar point. We suggest single-band photometry surveys could yield valuable information on exoplanet atmospheres and surfaces.« less

Is this a Brown Dwarf or an Exoplanet?

NASA Astrophysics Data System (ADS)

2005-04-01

Since the discovery in 1995 of the first planet orbiting a normal star other than the Sun, there are now more than 150 candidates of these so-called exoplanets known. Most of them are detected by indirect methods, based either on variations of the radial velocity or the dimming of the star as the planet passes in front of it (see ESO PR 06/03, ESO PR 11/04 and ESO PR 22/04). Astronomers would, however, prefer to obtain a direct image of an exoplanet, allowing them to better characterize the object's physical nature. This is an exceedingly difficult task, as the planet is generally hidden in the "glare" of its host star. To partly overcome this problem, astronomers study very young objects. Indeed, sub-stellar objects are much hotter and brighter when young and therefore can be more easily detected than older objects of similar mass. Based on this approach, it might well be that last year's detection of a feeble speck of light next to the young brown dwarf 2M1207 by an international team of astronomers using the ESO Very Large Telescope (ESO PR 23/04) is the long-sought bona-fide image of an exoplanet. A recent report based on data from the Hubble Space Telescope seems to confirm this result. The even more recent observations made with the Spitzer Space Telescope of the warm infrared glows of two previously detected "hot Jupiter" planets is another interesting result in this context. This wealth of new results, obtained in the time span of a few months, illustrates perfectly the dynamic of this field of research. Tiny Companion ESO PR Photo 10a/05 ESO PR Photo 10a/05 The Sub-Stellar Companion to GQ Lupi (NACO/VLT) [Preview - JPEG: 400 x 429 pix - 22k] [Normal - JPEG: 800 x 875 pix - 132k] [Full Res - JPEG: 1042 x 1116 pix - 241k] Caption: ESO PR Photo 10a/05 shows the VLT NACO image, taken in the Ks-band, of GQ Lupi. The feeble point of light to the right of the star is the newly found cold companion. It is 250 times fainter than the star itself and it located 0.73 arcsecond west. At the distance of GQ Lupi, this corresponds to a distance of roughly 100 astronomical units. North is up and East is to the left. Now, a different team of astronomers [1] has possibly made another important breakthrough in this field by finding a tiny companion to a young star. Since several years these scientists have conducted a search for planets and low-mass objects, in particular around stars still in their formation process - so-called T-Tauri stars - using both the direct imaging and the radial velocity techniques. One of the objects on their list is GQ Lupi, a young T-Tauri star, located in the Lupus I (the Wolf) cloud, a region of star formation about 400 or 500 light-years away. The star GQ Lupi is apparently a very young object still surrounded by a disc, with an age between 100,000 and 2 million years. The astronomers observed GQ Lupi on 25 June 2004 with the adaptive optics instrument NACO attached to Yepun, the fourth 8.2-m Unit Telescope of the Very Large Telescope located on top of Cerro Paranal (Chile). The instrument's adaptive optics (AO) overcomes the distortion induced by atmospheric turbulence, producing extremely sharp near-infrared images. As ESO PR Photo 10a/05 shows, the series of NACO exposures clearly reveal the presence of the tiny companion, located in the close vicinity of the star. This newly found object is only 0.7 arcsecond away, and would have been overlooked without the use of the adaptive optics capabilities of NACO. At the distance of GQ Lupi, the separation between the star and its feeble companion is about 100 astronomical units (or 100 times the distance between the Sun and the Earth). This is roughly 2.5 times the distance between Pluto and the Sun. The companion, called GQ Lupi B or GQ Lupi b [2], is roughly 250 times fainter than GQ Lupi A as seen in this series of image. Further images obtained with NACO in August and September confirmed the presence and the position of this companion. Moving in the same direction ESO PR Photo 10b/05 ESO PR Photo 10b/05 Observed Separation between GQ Lupi and its Companion [Preview - JPEG: 400 x 554 pix - 34k] [Normal - JPEG: 800 x 1107 pix - 136k] [Full Res - JPEG: 1560 x 2158 pix - 319k] Caption: ESO PR Photo 10a/05 presents the observed separations between the primary star GQ Lupi and its companion, as deduced from the images taken with HST in 1999 (left), Subaru in 2002 (middle) and NACO on the VLT in 2004 (right). All the observed separations are consistent with no changes in separation, implying the two objects move in the same direction (red line). The curved line shows the change in separation expected if the faint object was a background star, due to the proper motion of GQ Lup. The astronomers then uncovered that the star had been previously observed by the Subaru telescope as well as by the Hubble Space Telescope. They retrieved the corresponding images from the data archives of these facilities for further analysis. The older images, taken in July 2002 and April 1999, respectively, also showed the presence of the companion, giving the astronomers the possibility of precisely measuring the position of the two objects over a period of several years. This in turn allowed them to determine if the stars move together in the sky - as should be expected if they are gravitationally bound together - or if the smaller object is only a background object, just aligned by chance. From their measurements, the astronomers found that the separation between the two objects did not change over the five-year period covered by the observations (see ESO PR Photo 10b/05). For the scientists this is a clear proof that both objects are moving in the same direction in the sky. "If the faint object would be a background object", says Ralph Neuhäuser of the University of Jena (Germany) and leader of the team, "we would see a change in separation as GQ Lup would be moving in the sky. From 1999 to 2004, the separation would have changed by 0.15 arcsec, while we are confident that the change is a least 20 times smaller." Exoplanet or brown dwarf? ESO PR Photo 10c/05 ESO PR Photo 10c/05 Spectrum of the Companion of GQ Lupi (NACO/VLT) [Preview - JPEG: 400 x 554 pix - 53k] [Normal - JPEG: 800 x 1108 pix - 200k] [Full Res - JPEG: 1570 x 2175 pix - 518k] Caption: ESO PR Photo 10c/05 shows the NACO spectrum of the companion of GQ Lupi (thick line, bottom) in the near-infrared (around the Ks-band at 2.2 microns). For comparison, the spectrum of a young M8 brown dwarf (top, in red) and of a L2 brown dwarf (second line, in brown) are shown. Also presented is the spectrum calculated using theoretical models for an object having a temperature of 2,000 degrees. This theoretical spectrum compares well with the observed one. To further probe the physical nature of the newly discovered object, the astronomers used NACO on the VLT to take a series of spectra. These showed the typical signature of a very cool object, in particular the presence of water and CO bands. Taking into account the infrared colours and the spectral data available, atmospheric model calculations point to a temperature between 1,600 and 2,500 degrees and a radius that is twice as large as Jupiter (see PR Photo 10c/05). According to this, GQ Lupi B is thus a cold and rather small object. But what is the nature of this faint object? Is it a bona-fide exoplanet or is it a brown dwarf, those "failed" stars that are not massive enough to centrally produce major nuclear reactions? Although the borderline between the two is still a matter of debate, one way to distinguish between the two is by their mass (as this is also done between brown dwarfs and stars): (giant) planets are lighter than about 13 Jupiter-masses (the critical mass needed to ignite deuterium fusion), brown dwarfs are heavier. What about GQ Lupi b? Unfortunately, the new observations do not provide a direct estimate of the mass of the object. Thus the astronomers must rely on comparison with theoretical models of such objects. But this is not as easy as it sounds. If, as astronomers generally accept, GQ Lupi A and B formed simultaneously, the newly found object is very young. The problem is that for such very young objects, traditional theoretical models are probably not applicable. If they are used, however, they provide an estimate of the mass of the object that lies somewhere between 3 to 42 Jupiter-masses, i.e. encompassing both the planet and the brown dwarf domains. These early phases in brown dwarf and planet formation are essentially unknown territory for models. It is very difficult to model the early collapse of the gas clouds given the conditions around the forming parent star. One set of models, specifically tailored to model the very young objects, provide masses as low as one to two Jupiter-masses. But as Ralph Neuhäuser points out "these new models still need to be calibrated, before the mass of such companions can be determined confidently". The astronomers also stress that from the comparison between their VLT/NACO spectra and the theoretical models of co-author Peter Hauschildt from Hamburg University (Germany), they arrive at the conclusion that the best fit is obtained for an object having roughly 2 Jupiter radii and 2 Jupiter masses. If this result holds, GQ Lupi b would thus be the youngest and lightest exoplanet to have been imaged. Further observations are still required to precisely determine the nature of GQ Lupi B. If the two objects are indeed bound, then the smallest object will need more than 1,000 years to complete an orbit around its host star. This is of course too long to wait but the effect of the orbital motion might possibly be detectable - as a tiny change in the separation between the two objects - in a few years. The team therefore plans to perform regular observations of this object using NACO on the VLT, in order to detect this motion. No doubt that in the mean time, further progress on the theoretical side will be achieved and that many sensational discoveries in this field will be made. More information The research presented in this ESO Press Release is published in a Letter to the Editor accepted for publication by Astronomy and Astrophysics ("Evidence for a co-moving sub-stellar companion of GQ Lup" by R. Neuhäuser et al.) and available in PDF form at http://www.edpsciences.org/articles/aa/pdf/forthpdf/aagj061_forth.pdf.

Spatially Resolved Spectroscopy of the PMS Quadruple GG Tau: Evidence for a Substellar Companion

NASA Astrophysics Data System (ADS)

White, R. J.; Ghez, A. M.; Schultz, G.; Reid, I. N.

1998-05-01

We present spatially resolved optical spectra from HST (FOS) and the Keck Telescope (HIRES & LRIS) of the components of the quadruple PMS system GG Tau. According to the latest PMS evolutionary models, the coldest component of this system, GG Tau/c B, appears to be substellar with a preliminary mass of only 50 M_J. This putative brown dwarf is especially intriguing as it shows clear signatures of accretion. The components of this quadruple, which span a wide range in mass, are used to test theoretical low mass PMS evolutionary models under the assumption that the components should be coeval.

47 new T dwarfs from the UKIDSS Large Area Survey

NASA Astrophysics Data System (ADS)

Burningham, Ben; Pinfield, D. J.; Lucas, P. W.; Leggett, S. K.; Deacon, N. R.; Tamura, M.; Tinney, C. G.; Lodieu, N.; Zhang, Z. H.; Huelamo, N.; Jones, H. R. A.; Murray, D. N.; Mortlock, D. J.; Patel, M.; Barrado Y Navascués, D.; Zapatero Osorio, M. R.; Ishii, M.; Kuzuhara, M.; Smart, R. L.

2010-08-01

We report the discovery of 47 new T dwarfs in the Fourth Data Release (DR4) from the Large Area Survey (LAS) of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey with spectral types ranging from T0 to T8.5. These bring the total sample of LAS T dwarfs to 80 as of DR4. In assigning spectral types to our objects we have identified eight new spectrally peculiar objects, and divide seven of them into two classes. H2O-H-early have a H2O-H index that differs with the H2O-J index by at least two subtypes. CH4-J-early have a CH4-J index that disagrees with the H20-J index by at least two subtypes. We have ruled out binarity as a sole explanation for both types of peculiarity, and suggest that they may represent hitherto unrecognized tracers of composition and/or gravity. Clear trends in z'(AB) - J and Y - J are apparent for our sample, consistent with weakening absorption in the red wing of the KI line at 0.77μm with decreasing effective temperature. We have used our sample to estimate space densities for T6-T9 dwarfs. By comparing our sample to Monte Carlo simulations of field T dwarfs for various mass functions of the form ψ(M) ~M-αpc-3M-1solar, we have placed weak constraints on the form of the field mass function. Our analysis suggests that the substellar mass function is declining at lower masses, with negative values of α preferred. This is at odds with results for young clusters that have been generally found to have α > 0.

Interpretation of a Variable Reflection Nebula Associated with HBC 340 and HBC 341 in NGC 1333

NASA Astrophysics Data System (ADS)

Dahm, S. E.; Hillenbrand, L. A.

2017-11-01

We present multi-epoch, R-band imaging obtained from the Palomar Transient Factory of a small, fan-shaped reflection nebula in NGC 1333 that experiences prominent brightness fluctuations. Photometry of HBC 340 (K7e) and HBC 341 (M5e), a visual pair of late-type, young stellar objects lying near the apex of the nebula, demonstrates that while both are variable, the former has brightened by more than two magnitudes following a deep local minimum in 2014 September. Keck high-dispersion (R ˜ 45,000-66,000), optical spectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary (HBC 340Aa + HBC 340Ab). Both HBC 340 and HBC 341 exhibit strong Hα and forbidden line emission, consistent with accretion and outflow. We conclude that the brightness fluctuations in the reflection nebula represent light echos produced by varying incident radiation emanating from HBC 340. The short-term variability observed in the protostar is attributed to irregular accretion activity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellar material. Archival Hubble Space Telescope imaging of the region reveals a second, faint (F814W ˜ 20.3 mag) companion to HBC 340 that lies 1.″02 (˜235 au) east of the protostar. If associated, this probable substellar mass object (20-50 Jupiter masses), HBC 340B, is likely unrelated to the observed brightness variations. The sustained brightening of HBC 340 since late 2014 can be explained by an EXor-like outburst, the recovery from a long duration eclipse event caused by obscuring circumstellar dust, or by the gradual removal of extincting material from along the line of sight. Our analysis here favors one of the extinction scenarios.

Warm Debris Disk Candidates from WISE

NASA Technical Reports Server (NTRS)

Padgett, Deborah; Stapelfeldt, Karl; Liu, Wilson; Leisawitz, David

2011-01-01

The Wide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22 microns. We report on a preliminary investigation of main sequence Hipparcos and Tycho catalog stars with 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred new warm debris disk candidates are detected among FGK stars and 150 A stars within 120 pc. We are in the process of obtaining spectra to determine spectral types and activity level of these stars and are using HST, Herschel and Keck to characterize the dust, multiplicity, and substellar companions of these systems. In this contribution, we will discuss source selection methods and individual examples from among the WISE debris disk candidates.

Warm Debris Disks from WISE

NASA Technical Reports Server (NTRS)

Padgett, Deborah L.

2011-01-01

"The Wide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22 microns. We report on a preliminary investigation of main sequence Hipparcos and Tycho catalog stars with 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred new warm debris disk candidates are detected among FGK stars and a similar number of A stars within 120 pc. We are in the process of obtaining spectra to determine spectral types and activity level of these stars and are using HST, Herschel and Keck to characterize the dust, multiplicity, and substellar companions of these systems. In this contribution, we will discuss source selection methods and individual examples from among the WISE debris disk candidates. "

Photometry, Astrometry, and Discoveries of Ultracool Dwarfs in the Pan-STARRS 3π Survey

NASA Astrophysics Data System (ADS)

Best, William M. J.; Magnier, Eugene A.; Liu, Michael C.; Deacon, Niall; Aller, Kimberly; Zhang, Zhoujian; Pan-STARRS1 Builders

2018-01-01

The Pan-STARRS1 3π Survey (PS1)'s far-red optical sensitivity makes it an exceptional new resource for discovering and characterizing ultracool dwarfs. We present a PS1-based catalog of photometry and proper motions of nearly 10,000 M, L, and T dwarfs, along with our analysis of the kinematics of nearby M6-T9 dwarfs, building a comprehensive picture of the local ultracool population. We highlight some especially interesting ultracool discoveries made with PS1, including brown dwarfs with spectral types in the enigmatic L/T transition, wide companions to main sequence stars that serve as age and metallicity bechmarks for substellar models, and free-floating members of the nearby young moving groups and star-forming regions with masses down to ≈5 MJup. With its public release, PS1 will continue to be a vital tool for studying the ultracool population.

Near-infrared photometry of WISE J085510.74-071442.5

NASA Astrophysics Data System (ADS)

Zapatero Osorio, M. R.; Lodieu, N.; Béjar, V. J. S.; Martín, E. L.; Ivanov, V. D.; Bayo, A.; Boffin, H. M. J.; Mužić, K.; Minniti, D.; Beamín, J. C.

2016-08-01

Aims: We aim at obtaining near-infrared photometry and deriving the mass, age, temperature, and surface gravity of WISE J085510.74-071442.5 (J0855-0714), which is the coolest object beyond the solar system currently known. Methods: We used publicly available data from the archives of the Hubble Space Telescope (HST) and the Very Large Telescope (VLT) to determine the emission of this source at 1.153 μm (F110W) and 1.575 μm (CH4-off). J0855-0714 was detected at both wavelengths with a signal-to-noise ratio of ≈10 (F110W) and ≈4 (CH4-off) at the peak of the corresponding point-spread-functions. Results: This is the first detection of J0855-0714 in the H-band wavelengths. We measured 26.31 ± 0.10 and 23.22 ± 0.35 mag in F110W and CH4-off (Vega system). J0855-0714 remains unresolved in the HST images that have a spatial resolution of 0.22''. Companions at separations of 0.5 AU (similar mass and brightness) and at ~1 AU (≈1 mag fainter in the F110W filter) are discarded. By combining the new data with published photometry, including non-detections, we build the spectral energy distribution of J0855-0714 from 0.89 through 22.09 μm, and contrast it against current solar-metallicity models of planetary atmospheres. We determine that the best spectral fit yields a temperature of 225-250 K, a bolometric luminosity of log L/L⊙ = -8.57, and a high surface gravity of log g = 5.0 (cm s-2), which suggests an old age although a gravity this high is not fully compatible with evolutionary models. After comparing our data with the cooling theory for brown dwarfs and planets, we infer a mass in the interval 2-10 MJup for ages of 1-12 Gyr and high atmospheric gravities of log g ⪆ 3.5 (cm s-2). If it had the age of the Sun, J0855-0714 would be a ≈5-MJup free-floating planetary-mass object. Conclusions: J0855-0714 meets the mass values previously determined for free-floating planetary-mass objects discovered in star-forming regions and young stellar clusters. Based on extrapolations of the substellar mass functions of young clusters to the field, as many J0855-0714-like objects as M5-L2 stars may be expected to populate the solar neighborhood.

One more neighbor: The first brown dwarf in the VVV survey

NASA Astrophysics Data System (ADS)

Beamín, J. C.; Minniti, D.; Gromadzki, M.; Kurtev, R.; Ivanov, V. D.; Beletsky, Y.; Lucas, P.; Saito, R. K.; Borissova, J.

2013-09-01

Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and young star clusters has helped to constraint the low-mass end of the stellar mass function and the initial mass function. We use data of the Vista Variables in the Vía Láctea (VVV), a near-infrared (NIR) multi-wavelength (ZYJHKs) multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern Galactic plane to search for nearby BDs. Aims: The ultimate aim of the project is to improve the completeness of the census of nearby stellar and substellar objects towards the Galactic bulge and inner disk regions. Methods: Taking advantage of the homogeneous sample of VVV multi-epoch data, we identified stars with high proper motion ( ≥ 0.1'' yr-1), and then selected low-mass objects using NIR colors. We searched for a possible parallax signature using the all available Ks band epochs. We set some constraints on the month-to-year scale Ks band variability of our candidates, and even searched for possible transiting companions. We obtained NIR spectra to properly classify spectral type and then the physical properties of the final list of candidates. Results: We report the discovery of VVV BD001, a new member of the local volume-limited sample (within 20 pc from the Sun) with well defined proper motion, distance, and luminosity. The spectral type of this new object is an L5 ± 1, unusually blue dwarf. The proper motion for this BD is PM(α) = -0.5455 ± 0.004'' yr-1, PM(δ) = -0.3255 ± 0.004'' yr-1, and it has a parallax of 57 ± 4 mas which translates into a distance of 17.5 ± 1.1 pc. VVV BD001 shows no evidence of variability (ΔKs < 0.05 mag) over two years, especially constrained on a six month scale during the year 2012. Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179.B-2002.

Benchmark cool companions: ages and abundances for the PZ Telescopii system

NASA Astrophysics Data System (ADS)

Jenkins, J. S.; Pavlenko, Y. V.; Ivanyuk, O.; Gallardo, J.; Jones, M. I.; Day-Jones, A. C.; Jones, H. R. A.; Ruiz, M. T.; Pinfield, D. J.; Yakovina, L.

2012-03-01

We present new ages and abundance measurements for the pre-main-sequence star PZ Telescopii (more commonly known as PZ Tel). PZ Tel was recently found to host a young and low-mass companion. Such companions, whether they are brown dwarfs or planetary systems, can attain benchmark status by detailed study of the properties of the primary, and then evolutionary and bulk characteristics can be inferred for the companion. Using Fibre-fed Extended Range Optical Spectrograph spectra, we have measured atomic abundances (e.g. Fe and Li) and chromospheric activity for PZ Tel and used these to obtain the metallicity and age estimates for the companion. We have also determined the age independently using the latest evolutionary models. We find PZ Tel A to be a rapidly rotating (v sin i= 73 ± 5 km s-1), approximately solar metallicity star [log N(Fe) =-4.37 ± 0.06 dex or [Fe/H] = 0.05 ± 0.20 dex]. We measure a non-local thermodynamic equilibrium lithium abundance of log N(Li) = 3.1 ± 0.1 dex, which from depletion models gives rise to an age of 7? Myr for the system. Our measured chromospheric activity (? of -4.12) returns an age of 26 ± 2 Myr, as does fitting pre-main-sequence evolutionary tracks (τevol= 22 ± 3 Myr), both of these are in disagreement with the lithium age. We speculate on reasons for this difference and introduce new models for lithium depletion that incorporate both rotation and magnetic field effects. We also synthesize solar, metal-poor and metal-rich substellar evolutionary models to better determine the bulk properties of PZ Tel B, showing that PZ Tel B is probably more massive than previous estimates, meaning the companion is not a giant exoplanet, even though a planetary-like formation origin can go some way to describing the distribution of benchmark binaries currently known. We show how PZ Tel B compares to other currently known age and metallicity benchmark systems and try to empirically test the effects of dust opacity as a function of metallicity on the near-infrared colours of brown dwarfs. Current models suggest that in the near-infrared observations are more sensitive to low-mass companions orbiting more metal rich stars. We also look for trends between infrared photometry and metallicity amongst a growing population of substellar benchmark objects, and identify the need for more data in mass-age-metallicity parameter space.

News From The Erebos Project

NASA Astrophysics Data System (ADS)

Schaffenroth, Veronika; Barlow, Brad; Geier, Stephan; Vučković, Maja; Kilkenny, Dave; Schaffenroth, Johannes

2017-12-01

Planets and brown dwarfs in close orbits will interact with their host stars, as soon as the stars evolve to become red giants. However, the outcome of those interactions is still unclear. Recently, several brown dwarfs have been discovered orbiting hot subdwarf stars at very short orbital periods of 0.065 - 0.096 d. More than 8% of the close hot subdwarf binaries might have sub-stellar companions. This shows that such companions can significantly affect late stellar evolution and that sdB binaries are ideal objects to study this influence. Thirty-eight new eclipsing sdB binary systems with cool low-mass companions and periods from 0.05 to 0.5 d were discovered based on their light curves by the OGLE project. In the recently published catalog of eclipsing binaries in the Galactic bulge, we discovered 75 more systems. We want to use this unique and homogeneously selected sample to derive the mass distribution of the companions, constrain the fraction of sub-stellar companions and determine the minimum mass needed to strip off the red-giant envelope. We are especially interested in testing models that predict hot Jupiter planets as possible companions. Therefore, we started the EREBOS (Eclipsing Reflection Effect Binaries from the OGLE Survey) project, which aims at analyzing those new HW Vir systems based on a spectroscopic and photometric follow up. For this we were granted an ESO Large Program for ESO-VLT/FORS2. Here we give an update on the the current status of the project and present some preliminary results.

Ysovar: The First Sensitive, Wide-area, Mid-infrared Photometric Monitoring of the Orion Nebula Cluster

NASA Astrophysics Data System (ADS)

Morales-Calderón, M.; Stauffer, J. R.; Hillenbrand, L. A.; Gutermuth, R.; Song, I.; Rebull, L. M.; Plavchan, P.; Carpenter, J. M.; Whitney, B. A.; Covey, K.; Alves de Oliveira, C.; Winston, E.; McCaughrean, M. J.; Bouvier, J.; Guieu, S.; Vrba, F. J.; Holtzman, J.; Marchis, F.; Hora, J. L.; Wasserman, L. H.; Terebey, S.; Megeath, T.; Guinan, E.; Forbrich, J.; Huélamo, N.; Riviere-Marichalar, P.; Barrado, D.; Stapelfeldt, K.; Hernández, J.; Allen, L. E.; Ardila, D. R.; Bayo, A.; Favata, F.; James, D.; Werner, M.; Wood, K.

2011-05-01

We present initial results from time-series imaging at infrared wavelengths of 0.9 deg2 in the Orion Nebula Cluster (ONC). During Fall 2009 we obtained 81 epochs of Spitzer 3.6 and 4.5 μm data over 40 consecutive days. We extracted light curves with ~3% photometric accuracy for ~2000 ONC members ranging from several solar masses down to well below the hydrogen-burning mass limit. For many of the stars, we also have time-series photometry obtained at optical (Ic ) and/or near-infrared (JK s ) wavelengths. Our data set can be mined to determine stellar rotation periods, identify new pre-main-sequence eclipsing binaries, search for new substellar Orion members, and help better determine the frequency of circumstellar disks as a function of stellar mass in the ONC. Our primary focus is the unique ability of 3.6 and 4.5 μm variability information to improve our understanding of inner disk processes and structure in the Class I and II young stellar objects (YSOs). In this paper, we provide a brief overview of the YSOVAR Orion data obtained in Fall 2009 and highlight our light curves for AA-Tau analogs—YSOs with narrow dips in flux, most probably due to disk density structures passing through our line of sight. Detailed follow-up observations are needed in order to better quantify the nature of the obscuring bodies and what this implies for the structure of the inner disks of YSOs.

Survival of a brown dwarf after engulfment by a red giant star.

PubMed

Maxted, P F L; Napiwotzki, R; Dobbie, P D; Burleigh, M R

2006-08-03

Many sub-stellar companions (usually planets but also some brown dwarfs) orbit solar-type stars. These stars can engulf their sub-stellar companions when they become red giants. This interaction may explain several outstanding problems in astrophysics but it is unclear under what conditions a low mass companion will evaporate, survive the interaction unchanged or gain mass. Observational tests of models for this interaction have been hampered by a lack of positively identified remnants-that is, white dwarf stars with close, sub-stellar companions. The companion to the pre-white dwarf AA Doradus may be a brown dwarf, but the uncertain history of this star and the extreme luminosity difference between the components make it difficult to interpret the observations or to put strong constraints on the models. The magnetic white dwarf SDSS J121209.31 + 013627.7 may have a close brown dwarf companion but little is known about this binary at present. Here we report the discovery of a brown dwarf in a short period orbit around a white dwarf. The properties of both stars in this binary can be directly observed and show that the brown dwarf was engulfed by a red giant but that this had little effect on it.

Baryonic Dark Matter: The Results from Microlensing Surveys

NASA Astrophysics Data System (ADS)

Alcock, Charles; Allsman, Robyn A.; Alves, David; Axelrod, Tim S.; Becker, Andrew C.; Bennett, David; Cook, Kem H.; Drake, Andrew J.; Freeman, Ken C.; Griest, Kim; Lehner, Matt; Marshall, Stuart; Minniti, Dante; Peterson, Bruce; Pratt, Mark; Quinn, Peter; Rodgers, Alex; Stubbs, Chris; Sutherland, Will; Tomaney, Austin; Vandehei, Thor; Welch, Doug L.

Baryonic material can exist in several dark forms: ``planets," brown dwarfs, very old degenerate dwarf stars, and neutron stars. (Black holes are frequently added to this list, even though a black hole has no baryon number.) These objects, most of which emit some light but at levels below present day detection thresholds, are collectively known as Machos. Several groups have exploited the gravitational microlens signature to search for Machos in the dark halo of the Milky Way. Over 200 microlensing events have been reported (most by the MACHO Project, which uses the Great Melbourne Telescope near this conference site), of which about 20 are toward the Magellanic Clouds. The most straightforward interpretation of the results is that Machos make up between 20% and 100% of the dark matter in the halo, and that these objects weigh about 0.5 msun. Objects of substellar mass do not comprise much of the dark matter. Many alternative interpretations of these results have been proposed. We will discuss strategies for resolving the differences among these competing explanations.

Initial Results from the Palomar Adaptive Optics Survey of Young Solar-Type Stars: A Brown Dwarf and Three Stellar Companions

NASA Astrophysics Data System (ADS)

Metchev, Stanimir A.; Hillenbrand, Lynne A.

2004-12-01

We present first results from the Palomar Adaptive Optics Survey of Young Stars conducted at the Hale 5 m telescope. Through direct imaging we have discovered a brown dwarf and two low-mass stellar companions to the young solar-type stars HD 49197, HD 129333 (EK Dra), and V522 Per and confirmed a previously suspected companion to RX J0329.1+0118 (Sterzik et al.), at respective separations of 0.95" (43 AU), 0.74" (25 AU), 2.09" (400 AU), and 3.78" (380 AU). Physical association of each binary system is established through common proper motion and/or low-resolution infrared spectroscopy. Based on the companion spectral types, we estimate their masses at 0.06, 0.20, 0.13, and 0.20 Msolar, respectively. From analysis of our imaging data combined with archival radial velocity data, we find that the spatially resolved companion to HD 129333 is potentially identical to the previously identified spectroscopic companion to this star (Duquennoy & Mayor). However, a discrepancy with the absolute magnitude suggests that the two companions could also be distinct, with the resolved one being the outermost component of a triple system. The brown dwarf HD 49197B is a new member of a growing list of directly imaged substellar companions at 10-1000 AU separations from main-sequence stars, indicating that such brown dwarfs may be more common than initially speculated.

Knowing Our Neighbors: Fundamental Properties of Nearby Stars

NASA Astrophysics Data System (ADS)

Bartlett, Jennifer L.; Ianna, P. A.; Henry, T. J.; Begam, M. C.; Jao, W.; Subasavage, J. P., Jr.; Nearby Stars, Research Consortium on

2007-12-01

Although the stars within 25 pc of the Sun constitute the one stellar sample that we can aspire to know thoroughly, we continue identifying objects closer than 10 pc. We know even less about local substellar populations, especially planets. The Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI) is observing 31 late-type, red dwarfs selected for my thesis as part of a larger effort to complete the nearby star census. Preliminary parallaxes substantiate distances less than 25 pc for at least 28 stars. Of these, LP 991-84, LHS 6167, and LP 876-10 may lie within 10 pc. Preliminary proper motions for all but three stars exceed 0.2” yr-1. One recently established neighbor, LP 869-26, also appears to be a new binary. Associated VRI photometry and spectroscopy are in progress as well. Many of these stars are potential targets for astrometric planet searches, such as the Space Interferometry Mission (SIM). In addition to confirming solar neighborhood membership, astrometry can discover brown dwarfs and planets. Time-series analyses of residuals to the UVa Southern Parallax Program (SPP) observations are contributing to frequency and distribution data for nearby substellar objects. In particular, LHS 288 displays an intriguing signal, which might be caused by a very low-mass companion. Twelve other SPP stars demonstrate no significant perturbations. Finally, re-analyzing the Leander McCormick Observatory photographic plates of Barnard's Star failed to detect any planets orbiting it. This study of more than 900 exposures was sensitive to bodies of 2.2 Jupiter masses or more. NSF grants AST 98-20711 and 05-07711, GSU, NASA-SIM, Litton Marine Systems, UVa, Hampden-Sydney College, US Naval Observatory, and the Levinson Fund of the Peninsula Community Foundation supported this research. The ANU Research School of Astronomy & Astrophysics allocated observing time generously. CTIOPI was an NOAO Survey Program and continues as part of the SMARTS Consortium.

Low-Mass Star Formation and the Initial Mass Function in Young Clusters

NASA Astrophysics Data System (ADS)

Luhman, Kevin Lee

I have used optical and near-infrared spectroscopy and imaging to measure spectral types and luminosities for young (/tau<10 Myr), embedded (AV=0[-]50), low-mass (0.1-1 Msolar) stars in three nearby (d<300 pc) clusters: L1495E, IC 348, and ρ Ophiuchi. In conjunction with theoretical evolutionary tracks, I have derived the star formation history and initial mass function for each stellar population. A large number of brown dwarf candidates have been identified in the photometry, several of which are confirmed through spectroscopy. Finally, I have measured the frequency and survival times of circumstellar disks and investigated the photometric and spectroscopic properties of protostars. In S 2, I apply observational tests to the available sets of evolutionary models for low-mass stars, concluding that the calculations of D'Antona & Mazzitelli are preferred for the range of masses and ages considered here. In S 3 and S 4, I examine in detail the spectroscopic characteristics and substellar nature of two brown dwarf candidates. The study then expands to include the populations within the clusters L1495E (S 5), IC 348 (S 6), and ρ Ophiuchi (S 7). In S 8, I briefly discuss the past, present, and future of scientific research related to this thesis.

Substellar Companions to weak-line TTauri Stars

NASA Astrophysics Data System (ADS)

Brandner, W.; Alcala, J. M.; Covino, E.; Frink, S.

1997-05-01

Weak-line TTauri stars, contrary to classical TTauri stars, no longer possess massive circumstellar disks. In weak-line TTauri stars, the circumstellar matter was either accreted onto the TTauri star or has been redistributed. Disk instabilities in the outer disk might result in the formation of brown dwarfs and giant planets. Based on photometric and spectroscopic studies of ROSAT sources, we have selected an initial sample of 200 weak-line TTauri stars in the Chamaeleon T association and the Scorpius Centaurus OB association. In the course of follow-up observations we identified visual and spectroscopic binary stars and excluded them from our final list, as the complex dynamics and gravitational interaction in binary systems might aggravate or even completely inhibit the formation of planets (depending on physical separation of the binary components and their mass-ratio). The membership of individual stars to the associations was established from proper motion studies and radial velocity surveys. Our final sample consists of 70 single weak-line TTauri stars. We have initiated a program to spatially RESOLVE young brown dwarfs and young giant planets as companions to single weak-line TTauri stars using adaptive optics at the ESO 3.6m telescope and HST/NICMOS. In this poster we describe the observing strategy and present first results of our adaptive optics observations.

Probing Ultracool Atmospheres and Substellar Interiors with Dynamical Masses

NASA Astrophysics Data System (ADS)

Dupuy, Trent

2010-09-01

After years of patient orbital monitoring, there is now a large sample of very low-mass stars and brown dwarfs with precise { 5%} dynamical masses. These binaries represent the gold standard for testing substellar theoretical models. Work to date has identified problems with the model-predicted broad-band colors, effective temperatures, and possibly even luminosity evolution with age. However, our ability to test models is currently limited by how well the individual components of these highly prized binaries are characterized. To solve this problem, we propose to use NICMOS and STIS to characterize this first large sample of ultracool binaries with well-determined dynamical masses. We will use NICMOS multi-band photometry to measure the SEDs of the binary components and thereby precisely estimate their spectral types and effective temperatures. We will use STIS to obtain resolved spectroscopy of the Li I doublet at 6708 A for a subset of three binaries whose masses lie very near the theoretical mass limit for lithium burning. The STIS data will provide the first ever resolved lithium measurements for brown dwarfs of known mass, enabling a direct probe of substellar interiors. Our proposed HST observations to characterize the components of these binaries is much less daunting in comparison to the years of orbital monitoring needed to yield dynamical masses, but these HST data are equally vital for robust tests of theory.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osorio, Mayra; Anglada, Guillem; Macías, Enrique

We present Very Large Array observations at 7 mm that trace the thermal emission of large dust grains in the HD 169142 protoplanetary disk. Our images show a ring of enhanced emission of radius ∼25-30 AU, whose inner region is devoid of detectable 7 mm emission. We interpret this ring as tracing the rim of an inner cavity or gap, possibly created by a planet or a substellar companion. The ring appears asymmetric, with the western part significantly brighter than the eastern one. This azimuthal asymmetry is reminiscent of the lopsided structures that are expected to be produced as a consequence of trappingmore » of large dust grains. Our observations also reveal an outer annular gap at radii from ∼40 to ∼70 AU. Unlike other sources, the radii of the inner cavity, the ring, and the outer gap observed in the 7 mm images, which trace preferentially the distribution of large (millimeter/centimeter sized) dust grains, coincide with those obtained from a previous near-infrared polarimetric image, which traces scattered light from small (micron-sized) dust grains. We model the broadband spectral energy distribution and the 7 mm images to constrain the disk physical structure. From this modeling we infer the presence of a small (radius ∼0.6 AU) residual disk inside the central cavity, indicating that the HD 169142 disk is a pre-transitional disk. The distribution of dust in three annuli with gaps in between them suggests that the disk in HD 169142 is being disrupted by at least two planets or substellar objects.« less

ALICE Data Release: A Revaluation of HST-NICMOS Coronagraphic Images

NASA Astrophysics Data System (ADS)

Hagan, J. Brendan; Choquet, Élodie; Soummer, Rémi; Vigan, Arthur

2018-04-01

The Hubble Space Telescope NICMOS instrument was used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets and disks studies. As part of the Archival Legacy Investigations of Circumstellar Environments program, we have consistently reprocessed a large fraction of the NICMOS coronagrahic archive using advanced starlight subtraction methods. We present here the high-level science products of these re-analyzed data, which we delivered back to the community through the Mikulski Archive for Space Telescopes: doi:10.17909/T9W89V. We also present the second version of the HCI-FITS format (for High-Contrast Imaging FITS format), which we developed as a standard format for data exchange of imaging reduced science products. These re-analyzed products are openly available for population statistics studies, characterization of specific targets, or detected point-source identification.

Planets, Planetary Nebulae, and Intermediate Luminosity Optical Transients (ILOTs)

NASA Astrophysics Data System (ADS)

Soker, Noam

2018-05-01

I review some aspects related to the influence of planets on the evolution of stars before and beyond the main sequence. Some processes include the tidal destruction of a planet on to a very young main sequence star, on to a low mass main sequence star, and on to a brown dwarf. This process releases gravitational energy that might be observed as a faint intermediate luminosity optical transient (ILOT) event. I then summarize the view that some elliptical planetary nebulae are shaped by planets. When the planet interacts with a low mass upper asymptotic giant branch (AGB) star it both enhances the mass loss rate and shapes the wind to form an elliptical planetary nebula, mainly by spinning up the envelope and by exciting waves in the envelope. If no interaction with a companion, stellar or sub-stellar, takes place beyond the main sequence, the star is termed a Jsolated star, and its mass loss rates on the giant branches are likely to be much lower than what is traditionally assumed.

PROPERTIES OF THE NEARBY BROWN DWARF WISEP J180026.60+013453.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gizis, John E.; Burgasser, Adam J.; Vrba, Frederick J.

2015-12-15

We present new spectroscopy and astrometry to characterize the nearby brown dwarf WISEP J180026.60+013453.1. The optical spectral type, L7.5, is in agreement with the previously reported near-infrared spectral type. The preliminary trigonometric parallax places it at a distance of 8.01 ± 0.21 pc, confirming that it is the fourth closest known late-L (L7–L9) dwarf. The measured luminosity, our detection of lithium, and the lack of low surface gravity indicators indicates that WISEP J180026.60+013453.1 has a mass 0.03 < M < 0.06 M{sub ⊙} and an age between 300 million and 1.5 billion years according to theoretical substellar evolution models. Themore » low space motion is consistent with this young age. We have measured the rotational broadening (v sin i = 13.5 ± 0.5 km s{sup −1}), and use it to estimate a maximum rotation period of 9.3 hr.« less

Exploration of the environments of nearby stars with the NICMOS coronagraph: instrumental performance considerations

NASA Astrophysics Data System (ADS)

Schneider, Glenn; Thompson, Rodger I.; Smith, Bradford A.; Terrile, Richard J.

1998-08-01

The Near IR Camera and Multi-Object Spectrometer (NICMOS), installed into the Hubble Space Telescope (HST) in February 1997, incorporates a coronagraphic imaging capability. The coronagraph is comprised of two optical elements. The camera 2 field divider mirror, upon which the HST f/24 input beam is imaged, includes a 170 micrometers diameter hole which contains approximately 93 percent of the encircled energy from a stellar Point Spread Function (PSF) at a wavelength of 1.6 micrometers . The coronagraphic hole lowers both the diffracted energy in the surrounding region by reducing the high spatial frequency components of the occulted core of the PSF< and down stream scattering. The geometrical radius of this occulting spot, when re-imaged through the camera 2 f/45 optics, is approximately 4 pixels at the detector focal plane. An oversized cold pupil-plane mask, with radial structures co-aligned with the HST secondary mirror spider, acts over the whole 19.1 inch by 19.2 field to further reduce the diffracted energy in the direction of the spider vanes. The absolute performance levels of the coronagraph were ascertained during the servicing mission observatory verification program. Using a differential imaging strategy we expect to achieve statistically significant detectors of sub-stellar companions at 1.6 micrometers with a (Delta) H of approximately 10 and separations as close as 0.5 inch. The NICMOS environments of nearby stars programs is exploiting this capability in systematic surveys of nearby, and young stars searching for brown dwarfs and giant planets, and protoplanetary disks around main-sequence stars.

LOCATING THE TRAILING EDGE OF THE CIRCUMBINARY RING IN THE KH 15D SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capelo, Holly L.; Herbst, William; Leggett, S. K.

2012-09-20

Following two years of complete occultation of both stars in the binary T Tauri star KH 15D by its opaque circumbinary ring, KH 15D has abruptly brightened again during apastron phases, reaching I = 15 mag. Here, we show that the brightening is accompanied by a change in spectral class from K6/K7 (the spectral class of star A) to {approx}K1, and a bluing of the system in V - I by about 0.3 mag. A radial velocity measurement confirms that, at apastron, we are now seeing direct light from star B, which is more luminous and of earlier spectral classmore » than star A. Evidently, the trailing edge of the occulting screen has just become tangent to one anse of star B's projected orbit. This confirms a prediction of the precession models, supports the view that the tilted ring is self-gravitating, and ushers in a new era of the system's evolution that should be accompanied by the same kind of dramatic phenomena observed from 1995 to 2009. It also promotes KH 15D from a single-lined to a double-lined eclipsing binary, greatly enhancing its value for testing pre-main-sequence models. The results of our study strengthen the case for truncation of the outer ring at around 4 AU by a sub-stellar object such as an extremely young giant planet. The system is currently at an optimal configuration for detecting the putative planet and we urge expedient follow-up observations.« less

X-shooter spectroscopy of young stellar objects in Lupus. Accretion properties of class II and transitional objects

NASA Astrophysics Data System (ADS)

Alcalá, J. M.; Manara, C. F.; Natta, A.; Frasca, A.; Testi, L.; Nisini, B.; Stelzer, B.; Williams, J. P.; Antoniucci, S.; Biazzo, K.; Covino, E.; Esposito, M.; Getman, F.; Rigliaco, E.

2017-04-01

The mass accretion rate, Ṁacc, is a key quantity for the understanding of the physical processes governing the evolution of accretion discs around young low-mass (M⋆ ≲ 2.0 M⊙) stars and substellar objects (YSOs). We present here the results of a study of the stellar and accretion properties of the (almost) complete sample of class II and transitional YSOs in the Lupus I, II, III and IV clouds, based on spectroscopic data acquired with the VLT/X-shooter spectrograph. Our study combines the dataset from our previous work with new observations of 55 additional objects. We have investigated 92 YSO candidates in total, 11 of which have been definitely identified with giant stars unrelated to Lupus. The stellar and accretion properties of the 81 bona fide YSOs, which represent more than 90% of the whole class II and transition disc YSO population in the aforementioned Lupus clouds, have been homogeneously and self-consistently derived, allowing for an unbiased study of accretion and its relationship with stellar parameters. The accretion luminosity, Lacc, increases with the stellar luminosity, L⋆, with an overall slope of 1.6, similar but with a smaller scatter than in previous studies. There is a significant lack of strong accretors below L⋆ ≈ 0.1 L⊙, where Lacc is always lower than 0.01 L⋆. We argue that the Lacc - L⋆ slope is not due to observational biases, but is a true property of the Lupus YSOs. The log Ṁacc - log M⋆ correlation shows a statistically significant evidence of a break, with a steeper relation for M⋆ ≲ 0.2 M⊙ and a flatter slope for higher masses. The bimodality of the Ṁacc - M⋆ relation is confirmed with four different evolutionary models used to derive the stellar mass. The bimodal behaviour of the observed relationship supports the importance of modelling self-gravity in the early evolution of the more massive discs, but other processes, such as photo-evaporation and planet formation during the YSO's lifetime, may also lead to disc dispersal on different timescales depending on the stellar mass. The sample studied here more than doubles the number of YSOs with homogeneously and simultaneously determined Lacc and luminosity, Lline, of many permitted emission lines. Hence, we also refined the empirical relationships between Lacc and Lline on a more solid statistical basis. Based on observations collected at the European Southern Observatory at Paranal, under programs 084.C-0269(A), 085.C-0238(A), 086.C-0173(A), 087.C-0244(A), 089.C-0143(A), 095.C-0134(A), 097.C-0349(A), and archive data of programmes 085.C-0764(A) and 093.C-0506(A).

Confirmation of the binary status of Chamaeleon Hα 2 - a very young low-mass binary in Chamaeleon

NASA Astrophysics Data System (ADS)

Schmidt, T. O. B.; Neuhäuser, R.; Vogt, N.; Seifahrt, A.; Roell, T.; Bedalov, A.

2008-06-01

Context: Neuhäuser & Comerón (1998, Science, 282, 83; 1999, A&A, 350, 612) presented direct imaging evidence, as well as first spectra, of several young stellar and sub-stellar M6- to M8-type objects in the Cha I dark cloud. One of these objects is Cha Hα 2, classified as brown dwarf candidate in several publications and suggested as possible binary in Neuhäuser et al. (2002, A&A, 384, 999). Aims: We have searched around Cha Hα 2 for close and faint companions with adaptive optics imaging. Methods: Two epochs of direct imaging data were taken with the Very Large Telescope (VLT) Adaptive Optics instrument NACO in February 2006 and March 2007 in Ks-band together with a Hipparcos binary for astrometric calibration. Moreover, we took a J-band image in March 2007 to get color information. We retrieved an earlier image from 2005 from the European Southern Observatory (ESO) Science Archive Facility, increasing the available time coverage. After confirmation of common proper motion, we deduce physical parameters of the objects by spectroscopy, like temperature and mass. Results: We find Cha Hα 2 to be a very close binary of 0.16 arcsec separation, having a flux ratio of 0.91, thus having almost equal brightness and indistinguishable spectral types within the errors. We show that the two tentative components of Cha Hα 2 form a common proper motion pair, and that neither component is a non-moving background object. We even find evidence for orbital motion. A combined spectrum of both stars spanning optical and near-infrared parts of the spectral energy distribution yields a temperature of 3000 ± 100 K, corresponding to a spectral type of M6 ± 1 and a surface gravity of log{g} = 4.0+0.75-0.5, both from a comparison with GAIA model atmospheres. Furthermore, we obtained an optical extinction of AV ≃ 4.3 mag from this comparison. Conclusions: We derive masses of 0.110 M⊙ (≥0.070 M⊙) and 0.124 M⊙ (≥0.077 M⊙) for the two components of Cha Hα 2, i.e., probably low-mass stars, but one component could possibly be a brown dwarf. Based on observations made with ESO telescopes at the Paranal Observatory under programme IDs 076.C-0292A, 076.C-0339B, 078.C-0535A, at the La Silla Observatory under programme ID 065.L-0144B, the Hubble Space Telescope under programme ID GO-8716 and on observations made with the European Southern Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility. Color version of Fig. [see full textsee full text] is only available in electronic form at http://www.aanda.org

Doppler Imaging of Exoplanets and Brown Dwarfs

NASA Astrophysics Data System (ADS)

Crossfield, I.; Biller, B.; Schlieder, J.; Deacon, N.; Bonnefoy, M.; Homeier, D.; Allard, F.; Buenzli, E.; Henning, T.; Brandner, W.; Goldman, Bertr; Kopytova, T.

2014-03-01

Doppler Imaging produces 2D global maps. When applied to cool planets or more massive brown dwarfs, it can map atmospheric features and track global weather patterns. The first substellar map, of the 2pc-distant brown dwarf Luhman 16B (Crossfeld et al. 2014), revealed patchy regions of thin & thick clouds. Here, I investigate the feasibility of future Doppler Imaging of additional objects. Searching the literature, I find that all 3 of P, v sin i, and variability are published for 22 brown dwarfs. At least one datum exists for 333 targets. The sample is very incomplete below ~L5; we need more surveys to find the best targets for Doppler Imaging! I estimate limiting magnitudes for Doppler Imaging with various hi-resolution near-infrared spectrographs. Only a handful of objects - at the M/L and L/T transitions - can be mapped with current tools. Large telescopes such as TMT and GMT will allow Doppler Imaging of many dozens of brown dwarfs and the brightest exoplanets. More targets beyond type L5 likely remain to be found. Future observations will let us probe the global atmospheric dynamics of many diverse objects.

Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b. First data from the GIARPS Commissioning

NASA Astrophysics Data System (ADS)

Carleo, I.; Benatti, S.; Lanza, A. F.; Gratton, R.; Claudi, R.; Desidera, S.; Mace, G. N.; Messina, S.; Sanna, N.; Sissa, E.; Ghedina, A.; Ghinassi, F.; Guerra, J.; Harutyunyan, A.; Micela, G.; Molinari, E.; Oliva, E.; Tozzi, A.; Baffa, C.; Baruffolo, A.; Bignamini, A.; Buchschacher, N.; Cecconi, M.; Cosentino, R.; Endl, M.; Falcini, G.; Fantinel, D.; Fini, L.; Fugazza, D.; Galli, A.; Giani, E.; González, C.; González-Álvarez, E.; González, M.; Hernandez, N.; Hernandez Diaz, M.; Iuzzolino, M.; Kaplan, K. F.; Kidder, B. T.; Lodi, M.; Malavolta, L.; Maldonado, J.; Origlia, L.; Ventura, H. Perez; Puglisi, A.; Rainer, M.; Riverol, L.; Riverol, C.; San Juan, J.; Scuderi, S.; Seemann, U.; Sokal, K. R.; Sozzetti, A.; Sozzi, M.

2018-05-01

Context. Stellar activity is currently challenging the detection of young planets via the radial velocity (RV) technique. Aims: We attempt to definitively discriminate the nature of the RV variations for the young active K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent results on the existence of a substellar companion. Methods: We compare VIS data with high precision RVs in the near-infrared (NIR) range by using the GIANO-B and IGRINS spectrographs. In addition, we present for the first time simultaneous VIS-NIR observations obtained with GIARPS (GIANO-B and HARPS-N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV amplitude does not change at different wavelengths, while stellar activity induces wavelength-dependent RV variations, which are significantly reduced in the NIR range with respect to the VIS. Results: The NIR radial velocity measurements from GIANO-B and IGRINS show an average amplitude of about one quarter with respect to previously published VIS data, as expected when the RV jitter is due to stellar activity. Coeval multi-band photometry surprisingly shows larger amplitudes in the NIR range, explainable with a mixture of cool and hot spots in the same active region. Conclusions: In this work, the claimed massive planet around BD+20 1790 is ruled out by our data. We exploited the crucial role of multi-wavelength spectroscopy when observing young active stars: thanks to facilities like GIARPS that provide simultaneous observations, this method can reach its maximum potential.

Interpretation of a Variable Reflection Nebula Associated with HBC 340 and HBC 341 in NGC 1333

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahm, S. E.; Hillenbrand, L. A.

We present multi-epoch, R -band imaging obtained from the Palomar Transient Factory of a small, fan-shaped reflection nebula in NGC 1333 that experiences prominent brightness fluctuations. Photometry of HBC 340 (K7e) and HBC 341 (M5e), a visual pair of late-type, young stellar objects lying near the apex of the nebula, demonstrates that while both are variable, the former has brightened by more than two magnitudes following a deep local minimum in 2014 September. Keck high-dispersion ( R  ∼ 45,000–66,000), optical spectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary (HBC 340Aa + HBC 340Ab). Both HBC 340 andmore » HBC 341 exhibit strong H α and forbidden line emission, consistent with accretion and outflow. We conclude that the brightness fluctuations in the reflection nebula represent light echos produced by varying incident radiation emanating from HBC 340. The short-term variability observed in the protostar is attributed to irregular accretion activity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellar material. Archival Hubble Space Telescope imaging of the region reveals a second, faint (F814W ∼ 20.3 mag) companion to HBC 340 that lies 1.″02 (∼235 au) east of the protostar. If associated, this probable substellar mass object (20–50 Jupiter masses), HBC 340B, is likely unrelated to the observed brightness variations. The sustained brightening of HBC 340 since late 2014 can be explained by an EXor-like outburst, the recovery from a long duration eclipse event caused by obscuring circumstellar dust, or by the gradual removal of extincting material from along the line of sight. Our analysis here favors one of the extinction scenarios.« less

Clouds and hazes in exoplanets and brown dwarfs

NASA Astrophysics Data System (ADS)

Morley, Caroline Victoria

The formation of clouds significantly alters the spectra of cool substellar atmospheres from terrestrial planets to brown dwarfs. In cool planets like Earth and Jupiter, volatile species like water and ammonia condense to form ice clouds. In hot planets and brown dwarfs, iron and silicates instead condense, forming dusty clouds. Irradiated methane-rich planets may have substantial hydrocarbon hazes. During my dissertation, I have studied the impact of clouds and hazes in a variety of substellar objects. First, I present results for cool brown dwarfs including clouds previously neglected in model atmospheres. Model spectra that include sulfide and salt clouds can match the spectra of T dwarf atmospheres; water ice clouds will alter the spectra of the newest and coldest brown dwarfs, the Y dwarfs. These sulfide/salt and ice clouds potentially drive spectroscopic variability in these cool objects, and this variability should be distinguishable from variability caused by hot spots. Next, I present results for small, cool exoplanets between the size of Earth and Neptune. They likely have sulfide and salt clouds and also have photochemical hazes caused by stellar irradiation. Vast resources have been dedicated to characterizing the handful of super Earths and Neptunes accessible to current telescopes, yet of the planets smaller than Neptune studied to date, all have radii in the near-infrared consistent with being constant in wavelength, likely showing that these small planets are consistently enshrouded in thick hazes and clouds. For the super Earth GJ 1214b, very thick, lofted clouds of salts or sulfides in high metallicity (1000x solar) atmospheres create featureless transmission spectra in the near-infrared. Photochemical hazes also create featureless transmission spectra at lower metallicities. For the Neptune-sized GJ 436b, its thermal emission and transmission spectra combine indicate a high metallicity atmosphere, potentially heated by tides and affected by disequilibrium chemistry. I show that despite the challenges, there are promising avenues for understanding small planets: by observing thermal emission and reflected light, we can break the degeneracies and con- strain the atmospheric compositions. These future observations will provide rich diagnostics of molecules and clouds in small planets.

Recent Variability Observations of Solar System Giant Planets: Fresh Context for Understanding Exoplanet and Brown Dwarf Weather

NASA Astrophysics Data System (ADS)

Marley, Mark S.; Kepler Giant Planet Variability Team, Spitzer Ice Giant Variability Team

2016-10-01

Over the past several years a number of of high cadence photometric observations of solar system giant planets have been acquired by various platforms. Such observations are of interest as they provide points of comparison to the already expansive set of brown dwarf variability observations and the small, but growing, set of exoplanet variability observations. By measuring how rapidly the integrated light from solar system giant planets can evolve, variability observations of substellar objects that are unlikely to ever be resolved can be placed in a fuller context. Examples of brown dwarf variability observations include extensive work from the ground (e.g., Radigan et al. 2014), Spitzer (e.g., Metchev et al. 2015), Kepler (Gizis et al. 2015), and HST (Yang et al. 2015). Variability has been measured on the planetary mass companion to the brown dwarf 2MASS 1207b (Zhou et al. 2016) and further searches are planned in thermal emission for the known directly imaged planets with ground based telescopes (Apai et al. 2016) and in reflected light with future space based telescopes. Recent solar system variability observations include Kepler monitoring of Neptune (Simon et al. 2016) and Uranus, Spitzer observations of Neptune (Stauffer et al. 2016), and Cassini observations of Jupiter (West et al. in prep). The Cassini observations are of particular interest as they measured the variability of Jupiter at a phase angle of ˜60○, comparable to the viewing geometry expected for space based direct imaging of cool extrasolar Jupiters in reflected light. These solar system analog observations capture many of the characteristics seen in brown dwarf variability, including large amplitudes and rapid light curve evolution on timescales as short as a few rotation periods. Simon et al. (2016) attribute such variations at Neptune to a combination of large scale, stable cloud structures along with smaller, more rapidly varying, cloud patches. The observed brown dwarf and exoplanet variability may well arise from comparable cloud structures. In my presentation I will compare and contrast the nature of the variability observed for the various solar system and other substellar objects and present a wish list for future observations.

Limits on Line Bisector Variability for Stars with Extrasolar Planets

NASA Technical Reports Server (NTRS)

Povich, M. S.; Giampapa, M. S.; Valenti, J. A.; Tilleman, T.; Barden, S.; Deming, D.; Livingston, W. C.; Pilachowski, C.

2000-01-01

We present an analysis of high-resolution synoptic spectra of ten F- and G-type stars, seven of which exhibit periodic radial velocity variations due to the presence of one or more substellar companions. We searched for subtle periodic variations in photospheric line asymmetry, as characterized by line bisectors. In principle, periodic variations in line asymmetry observed at lower spectral resolution could mimic the radial velocity signature of a companion, but we find no significant evidence of such behavior in our data. Observations were obtained from 1998 March to 1999 February using the National Solar Observatory (NSO) 1.52-m McMath-Pierce Solar Telescope Facility on Kitt Peak in conjunction with the solar-stellar spectrograph, achieving a resolving power of 1.2x10(exp5). To characterize line asymmetry, we first measured line bisectors for the unblended Fe I photospheric line at 625.26 nm. To improve sensitivity to small fluctuations, we then combined points in each bisector to form a velocity displacement with respect to the line core. We searched for periodic variations in this displacement, finding no substantial difference between stars with substellar companions and those without reported companions. We find no correlation between bisector velocity displacement and the known orbital phase of substellar companions around our target stars. Simulations of a periodic signal with noise levels that mimic our measurement errors suggest that we can exclude bisector variations with amplitudes greater than about 20 m/s. These results support the conclusion that extrasolar planets best explain the observed periodic variations in radial velocity.

On Lithium-rich Red Giants. I. Engulfment of Substellar Companions

NASA Astrophysics Data System (ADS)

Aguilera-Gómez, Claudia; Chanamé, Julio; Pinsonneault, Marc H.; Carlberg, Joleen K.

2016-10-01

A small fraction of red giants are known to be lithium (Li) rich, in contradiction with expectations from stellar evolutionary theory. A possible explanation for these atypical giants is the engulfment of an Li-rich planet or brown dwarf by the star. In this work, we model the evolution of Li abundance in canonical red giants including the accretion of a substellar mass companion. We consider a wide range of stellar and companion masses, Li abundances, stellar metallicities, and planetary orbital periods. Based on our calculations, companions with masses lower than 15 {M}J dissolve in the convective envelope and can induce Li enrichment in regimes where extra mixing does not operate. Our models indicate that the accretion of a substellar companion can explain abundances up to A(Li) ≈ 2.2, setting an upper limit for Li-rich giants formed by this mechanism. Giants with higher abundances need another mechanism to be explained. For reasonable planetary distributions, we predict the Li abundance distribution of low-mass giants undergoing planet engulfment, finding that between 1% and 3% of them should have {{A}}({Li})≥slant 1.5. We show that depending on the stellar mass range, this traditional definition of Li-rich giants is misleading, as isolated massive stars would be considered anomalous while giants engulfing a companion would be set aside, flagged as normal. We explore the detectability of companion engulfment, finding that planets with masses higher than ∼ 7 {M}J produce a distinct signature, and that descendants of stars originating in the Li dip and low-luminosity red giants are ideal tests of this channel.

Planets around Low-mass Stars. III. A Young Dusty L Dwarf Companion at the Deuterium-burning Limit

NASA Astrophysics Data System (ADS)

Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Dupuy, Trent J.

2013-09-01

We report the discovery of an L-type companion to the young M3.5V star 2MASS J01225093-2439505 at a projected separation of 1.''45 (≈52 AU) as part of our adaptive optics imaging search for extrasolar giant planets around young low-mass stars. 2MASS 0122-2439 B has very red near-infrared colors similar to the HR 8799 planets and the reddest known young/dusty L dwarfs in the field. Moderate-resolution (R ≈ 3800) 1.5-2.4 μm spectroscopy reveals a near-infrared spectral type of L4-L6 and an angular H-band shape, confirming its cool temperature and young age. The kinematics of 2MASS 0122-2439 AB are marginally consistent with members of the ~120 Myr AB Dor young moving group based on the photometric distance to the primary (36 ± 4 pc) and our radial velocity measurement of 2MASS 0122-2439 A from Keck/HIRES. We adopt the AB Dor group age for the system, but the high energy emission, lack of Li I λ6707 absorption, and spectral shape of 2MASS 0122-2439 B suggest a range of ~10-120 Myr is possible. The age and luminosity of 2MASS 0122-2439 B fall in a strip where "hot-start" evolutionary model mass tracks overlap as a result of deuterium burning. Several known substellar companions also fall in this region (2MASS J0103-5515 ABb, AB Pic b, κ And b, G196-3 B, SDSS 2249+0044 B, LP 261-75 B, HD 203030 B, and HN Peg B), but their dual-valued mass predictions have largely been unrecognized. The implied mass of 2MASS 0122-2439 B is ≈12-13 M Jup or ≈22-27 M Jup if it is an AB Dor member, or possibly as low as 11 M Jup if the wider age range is adopted. Evolutionary models predict an effective temperature for 2MASS 0122-2439 B that corresponds to spectral types near the L/T transition (≈1300-1500 K) for field objects. However, we find a mid-L near-infrared spectral type, indicating that 2MASS 0122-2439 B represents another case of photospheric dust being retained to cooler temperatures at low surface gravities, as seen in the spectra of young (8-30 Myr) planetary companions. Altogether, the low mass, low temperature, and red colors of 2MASS 0122-2439 B make it a bridge between warm planets like β Pic b and cool, very dusty ones like HR 8799 bcde. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraus, Stefan; Espaillat, Catherine; Wilner, David J.

Pre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism, we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck Interferometer, Keck-II, Gemini South, and IRTF. This allows us to spatially resolve the AU-scale disk structure from near- to mid-infrared wavelengths (1.5-13 {mu}m), tracing material at different temperatures and over a wide range of stellocentric radii. Our observations reveal a narrow, optically thick inner-disk component (located at 0.18 AU from the star)more » that is separated from the optically thick outer disk (radii {approx}> 46 AU), providing unambiguous evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the H, K', and L' bands, we detect asymmetries in the brightness distribution on scales of {approx}15-40 AU, i.e., within the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the gap clearing.« less

SEARCHING FOR SCATTERERS: HIGH-CONTRAST IMAGING OF YOUNG STARS HOSTING WIDE-SEPARATION PLANETARY-MASS COMPANIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryan, Marta L.; Mawet, Dimitri; Bowler, Brendan P.

2016-08-20

We have conducted an angular differential imaging survey with NIRC2 at Keck in search of close-in substellar companions to a sample of seven systems with confirmed planetary-mass companions (PMCs) on wide orbits (>50 au). These wide-separation PMCs pose significant challenges to all three possible formation mechanisms: core accretion plus scattering, disk instability, and turbulent fragmentation. We explore the possibility that these companions formed closer in and were scattered out to their present-day locations by searching for other massive bodies at smaller separations. The typical sensitivity for this survey is Δ K ∼ 12.5 at 1″. We identify eight candidate companions,more » whose masses would reach as low as one Jupiter mass if gravitationally bound. From our multi-epoch astrometry we determine that seven of these are conclusively background objects, while the eighth near DH Tau is ambiguous and requires additional monitoring. We rule out the presence of >7 M {sub Jup} bodies in these systems down to 15–50 au that could be responsible for scattering. This result combined with the totality of evidence suggests that dynamical scattering is unlikely to have produced this population of PMCs. We detect orbital motion from the companions ROXs 42B b and ROXs 12 b, and from this determine 95% upper limits on the companions’ eccentricities of 0.58 and 0.83 respectively. Finally, we find that the 95% upper limit on the occurrence rate of additional planets with masses between 5 and 15 M {sub Jup} outside of 40 au in systems with PMCs is 54%.« less

The Discovery of a Disk-Jet System Directly Exposed to Strong Ultraviolet Fields in the Rosette Nebula

NASA Astrophysics Data System (ADS)

Li, Jin Zeng; Rector, Travis A.

2004-01-01

We report on the discovery of an optical jet with a striking morphology in the Rosette Nebula. It could be the most extreme case known of an accretion disk and jet system directly exposed to strong ionization fields that impose strong effects on disk evolution. Unlike typical optical flows, this jet system is found to have a high excitation nature mainly due to disruptive interaction with the violent environment. As a result, the extension of the highly collimated jet and possible former episodes of the degenerated counterjet all show bow-shocked structures. Our results provide implications on how incipience of massive stars in giant molecular clouds prevents further generations of low-mass star formation, and possibly also how isolated substellar/planetary-mass objects in regions of massive star formation are formed.

Making Sense of Atmospheric Models and Fundamental Stellar Properties at the Bottom of the Main Sequence

NASA Astrophysics Data System (ADS)

Dieterich, Sergio; Henry, Todd; Jao, W.-C.; Washington, Robert; Silverstein, Michele; Winters, J.; RECONS

2018-01-01

We present a detailed comparison of atmospheric model predictions and photometric observations for late M and L dwarfs. We discuss which wavelength regions are best for determining the fundamental properties of these cool stellar and substellar atmospheres and use this analysis to refine the HR diagram for the hydrogen burning limit first presented in 2014. We also add several new objects to the HR diagram and find little qualitative difference in the HR diagram's overall morphology when compared to our 2014 results. The L2 dwarf 2MASS 0523-1403 remains the smallest hydrogen burning star for which we calculated a radius, thus likely indicating the end of the stellar main sequence. This work is supported by the NSF Astronomy and Astrophysics Postdoctoral Fellowship program through grant AST-1400680.

VizieR Online Data Catalog: SONYC census of substellar objects in Lupus 3 (Muzic+, 2014)

NASA Astrophysics Data System (ADS)

Muzic, K.; Scholz, A.; Geers, V. C.; Jayawardhana, R.; Lopez Marti, B.

2017-06-01

The near-infrared observations were designed to provide J- and KS photometry in the area slightly larger than the one covered with MOSAIC-II. We used NEWFIRM at the CTIO 4 m telescope, providing an FOV of 28'x28' and a pixel scale of 0.4". The NEWFIRM detector is a mosaic of four 2048x2048 Orion InSb arrays, organized in a 2x2 grid. Data reduction was performed using the NEWFIRM pipeline. The data were dark- and sky-subtracted and were corrected for bad pixels and flat-field effects. The astrometry was calibrated with respect to the 2MASS (Skrutskie et al. 2006AJ....131.1163S, Cat. VII/233) coordinate system, and each detector quadrant was re-projected onto an undistorted celestial tangent plane. (3 data files).

Geothermal heating enhances atmospheric asymmetries on synchronously rotating planets

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Kopparapu, Ravi Kumar

2015-01-01

Earth-like planets within the liquid water habitable zone of M-type stars may evolve into synchronous rotators. On these planets, the substellar hemisphere experiences perpetual daylight while the opposing antistellar hemisphere experiences perpetual darkness. Because the night-side hemisphere has no direct source of energy, the air over this side of the planet is prone to freeze out and deposit on the surface, which could result in atmospheric collapse. However, general circulation models (GCMs) have shown that atmospheric dynamics can counteract this problem and provide sufficient energy transport to the antistellar side. Here, we use an idealized GCM to consider the impact of geothermal heating on the habitability of synchronously rotating planets. Geothermal heating may be expected due to tidal interactions with the host star, and the effects of geothermal heating provide additional habitable surface area and may help to induce melting of ice on the antistellar hemisphere. We also explore the persistence of atmospheric asymmetries between the Northern and Southern hemispheres, and we find that the direction of the meridional circulation (for rapidly rotating planets) or the direction of zonal wind (for slowly rotating planets) reverses on either side of the substellar point. We show that the zonal circulation approaches a theoretical state similar to a Walker circulation only for slowly rotating planets, while rapidly rotating planets show a zonal circulation with the opposite direction. We find that a cross-polar circulation is present in all cases and provides an additional mechanism of mass and energy transport from the substellar to antistellar point. Characterization of the atmospheres of synchronously rotating planets should include consideration of hemispheric differences in meridional circulation and examination of transport due to cross-polar flow.

Planets around Low-mass Stars (PALMS). I. A Substellar Companion to the Young M Dwarf 1RXS J235133.3+312720

NASA Astrophysics Data System (ADS)

Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Dupuy, Trent J.; Cieza, Lucas A.; Kraus, Adam L.; Tamura, Motohide

2012-07-01

We report the discovery of a brown dwarf companion to the young M dwarf 1RXS J235133.3+312720 as part of a high contrast imaging search for planets around nearby young low-mass stars with Keck-II/NIRC2 and Subaru/HiCIAO. The 2farcs4 (~120 AU) pair is confirmed to be comoving from two epochs of high-resolution imaging. Follow-up low- and moderate-resolution near-infrared spectroscopy of 1RXS J2351+3127 B with IRTF/SpeX and Keck-II/OSIRIS reveals a spectral type of L0+2 -1. The M2 primary star 1RXS J2351+3127 A exhibits X-ray and UV activity levels comparable to young moving group members with ages of ~10-100 Myr. UVW kinematics based the measured radial velocity of the primary and the system's photometric distance (50 ± 10 pc) indicate it is likely a member of the ~50-150 Myr AB Dor moving group. The near-infrared spectrum of 1RXS J2351+3127 B does not exhibit obvious signs of youth, but its H-band morphology shows subtle hints of intermediate surface gravity. The spectrum is also an excellent match to the ~200 Myr M9 brown dwarf LP 944-20. Assuming an age of 50-150 Myr, evolutionary models imply a mass of 32 ± 6 M Jup for the companion, making 1RXS J2351+3127 B the second lowest-mass member of the AB Dor moving group after the L4 companion CD-35 2722 B and one of the few benchmark brown dwarfs known at young ages. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Substellar fragmentation in self-gravitating fluids with a major phase transition

NASA Astrophysics Data System (ADS)

Füglistaler, A.; Pfenniger, D.

2015-06-01

Context. The observation of various ices in cold molecular clouds, the existence of ubiquitous substellar, cold H2 globules in planetary nebulae and supernova remnants, or the mere existence of comets suggest that the physics of very cold interstellar gas might be much richer than usually envisioned. At the extreme of low temperatures (≲10 K), H2 itself is subject to a phase transition crossing the entire cosmic gas density scale. Aims: This well-known, laboratory-based fact motivates us to study the ideal case of a cold neutral gaseous medium in interstellar conditions for which the bulk of the mass, instead of trace elements, is subject to a gas-liquid or gas-solid phase transition. Methods: On the one hand, the equilibrium of general non-ideal fluids is studied using the virial theorem and linear stability analysis. On the other hand, the non-linear dynamics is studied using computer simulations to characterize the expected formation of solid bodies analogous to comets. The simulations are run with a state-of-the-art molecular dynamics code (LAMMPS) using the Lennard-Jones inter-molecular potential. The long-range gravitational forces can be taken into account together with short-range molecular forces with finite limited computational resources, using super-molecules, provided the right scaling is followed. Results: The concept of super-molecule, where the phase transition conditions are preserved by the proper choice of the particle parameters, is tested with computer simulations, allowing us to correctly satisfy the Jeans instability criterion for one-phase fluids. The simulations show that fluids presenting a phase transition are gravitationally unstable as well, independent of the strength of the gravitational potential, producing two distinct kinds of substellar bodies, those dominated by gravity (planetoids) and those dominated by molecular attractive force (comets). Conclusions: Observations, formal analysis, and computer simulations suggest the possibility of the formation of substellar H2 clumps in cold molecular clouds due to the combination of phase transition and gravity. Fluids presenting a phase transition are gravitationally unstable, independent of the strength of the gravitational potential. Arbitrarily small H2 clumps may form even at relatively high temperatures up to 400-600 K, according to virial analysis. The combination of phase transition and gravity may be relevant for a wider range of astrophysical situations, such as proto-planetary disks. Figures 33-44 are available in electronic form at http://www.aanda.org

A Search for X-ray Emission from the First Magnetically Active T Dwarf

NASA Astrophysics Data System (ADS)

Williams, Peter

2015-09-01

Ultracool dwarfs (spectral types >M7) were long expected to be magnetically inactive, but concerted X-ray and radio observations (mostly by our group) have led to the discovery of magnetic activity and a characterization of its basic properties. We have recently discovered periodic radio bursts from the T6.5 dwarf 2MASS 1047+21, by far the coolest (900 K) substellar object detected in the radio, implying high levels of magnetic activity well into the brown dwarf regime and making it a uniquely compelling target in the challenging search for ultracool X-ray emission. We propose a 40 ks observation with ACIS-S and the VLA that will cover 6 full rotations, place the deepest constraints on X-ray luminosity to date, and may lead to the first detection of X-ray emission from a T dwarf.

The Star, the Dwarf and the Planet

NASA Astrophysics Data System (ADS)

2006-10-01

Astronomers have detected a new faint companion to the star HD 3651, already known to host a planet. This companion, a brown dwarf, is the faintest known companion of an exoplanet host star imaged directly and one of the faintest T dwarfs detected in the Solar neighbourhood so far. The detection yields important information on the conditions under which planets form. "Such a system is an interesting example that might prove that planets and brown dwarfs can form around the same star", said Markus Mugrauer, lead author of the paper presenting the discovery. ESO PR Photo 39a/06 ESO PR Photo 39a/06 The Companion to HD 3651 HD 3651 is a star slightly less massive than the Sun, located 36 light-years away in the constellation Pisces (the "Fish"). For several years, it has been known to harbour a planet less massive than Saturn, sitting closer to its parent star than Mercury is from the Sun: the planet accomplishes a full orbit in 62 days. Mugrauer and his colleagues first spotted the faint companion in 2003 on images from the 3.8-m United Kingdom Infrared Telescope (UKIRT) in Hawaii. Observations in 2004 and 2006 using ESO's 3.6 m New Technology Telescope (NTT) at La Silla provided the crucial confirmation that the speck of light is not a spurious background star, but indeed a true companion. The newly found companion, HD 3651B, is 16 times further away from HD 3651 than Neptune is from the Sun. HD 3651B is the dimmest directly imaged companion of an exoplanet host star. Furthermore, as it is not detected on the photographic plates of the Palomar All Sky Survey, the companion must be even fainter in the visible spectral range than in the infrared, meaning it is a very cool low-mass sub-stellar object. Comparing its characteristics with theoretical models, the astronomers infer that the object has a mass between 20 and 60 Jupiter masses, and a temperature between 500 and 600 degrees Celsius. It is thus ten times colder and 300 000 less luminous than the Sun. These properties place it in the category of cool T-type brown dwarfs. ESO PR Photo 38b/06 ESO PR Photo 39b/06 The Relative Position of the Companion to HD 3651 "Due to their faintness even in the infrared, these cool T dwarfs are very difficult to find", said Mugrauer. "Only two other brown dwarfs with similar brightness are presently known. Their study will provide important insights into the atmospheric properties of cool sub-stellar objects." More than 170 stars are currently known to host exoplanets. In some cases, these stars were also found to have one or several stellar companions, showing that planet formation can also take place in a dynamically more complex environment than our own Solar System where planet formation occurred around an isolated single star. In 2001, Mugrauer and his colleagues started an observational programme to find out whether exoplanet host stars are single or married. In this programme, known exoplanet host stars are systematically imaged at two different epochs, at least several months apart. True companions can be distinguished from coincidental background objects as only they move together with the stars over time. With this effective search strategy several new companions of exoplanet host stars have been detected. Most of the detected companions are low-mass stars in the same evolutionary state as the Sun. In two cases, however, the astronomers found the companions to be white dwarfs, that is, stars at the end of their life. These intriguing systems bear evidence that planets can even survive the troubled last moments in the life of a nearby star. The planet host star HD 3651 is thus surrounded by two sub-stellar objects. The planet, HD 3651b, is very close, while the newly found brown dwarf companion revolves around the star 1500 times farther away than the planet. This system is the first imaged example that planets and brown dwarfs can form around the same star.

The Phases Differential Astrometry Data Archive. 5. Candidate Substellar Companions to Binary Systems

DTIC Science & Technology

2010-12-01

Mathematics and Astronomy , 105-24, California Institute of Technology, Pasadena, CA 91125, USA 5 Nicolaus Copernicus Astronomical Center, Polish Academy...Blind Test with support from NASA contract NAS7-03001 (JPL 1336910). PHASES is funded in part by the California Institute of Technol- ogy Astronomy

Timescales of Disk Evolution and Planet Formation: HST, Adaptive Optics, and ISO Observations of Weak-Line and Post-T Tauri Stars

NASA Astrophysics Data System (ADS)

Brandner, Wolfgang; Zinnecker, Hans; Alcalá, Juan M.; Allard, France; Covino, Elvira; Frink, Sabine; Köhler, Rainer; Kunkel, Michael; Moneti, Andrea; Schweitzer, Andreas

2000-08-01

We present high spatial resolution HST and ground-based adaptive optics observations and high-sensitivity ISO (ISOCAM & ISOPHOT) observations of a sample of X-ray selected weak-line (WTTS) and post- (PTTS) T Tauri stars located in the nearby Chamaeleon T and Scorpius-Centaurus OB associations. HST/NICMOS and adaptive optics observations aimed at identifying substellar companions (young brown dwarfs) at separations >=30 AU from the primary stars. No such objects were found within 300 AU of any of the target stars, and a number of faint objects at larger separations can very likely be attributed to a population of field (background) stars. ISOCAM observations of 5 to 15 Myr old WTTSs and PTTSs in ScoCen reveal infrared excesses which are clearly above photospheric levels and which have a spectral index intermediate between that of younger (1 to 5 Myr) T Tauri stars in Chamaeleon and that of pure stellar photospheres. The difference in the spectral index of the older PTTSs in ScoCen compared with the younger classical and weak-line TTSs in Cha can be attributed to a deficiency of smaller size (0.1 to 1 μm) dust grains relative to larger size (~5 μm) dust grains in the disks of the PTTSs. The lack of small dust grains is either due to the environment (effect of nearby O stars and supernova explosions) or due to disk evolution. If the latter is the case, it would hint that circumstellar disks start to become dust depleted at an age between 5 to 15 Myr. Dust depletion is very likely related to the build-up of larger particles (ultimately rocks and planetesimals) and thus an indicator for the onset of the period of planet formation. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555, observations at the European Southern Observatory, La Silla (ESO Prop ID 58.E-0169), and observations with ESA's Infrared Space Observatory.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star

NASA Astrophysics Data System (ADS)

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M.; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J.; Triaud, Amaury H. M. J.; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K.; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2016-05-01

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ‘ultracool dwarfs’. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them—ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star.

PubMed

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J; Triaud, Amaury H M J; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2016-05-12

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

Imprints of dynamical interactions on brown dwarf pairing statistics and kinematics

NASA Astrophysics Data System (ADS)

Sterzik, M. F.; Durisen, R. H.

2003-03-01

We present statistically robust predictions of brown dwarf properties arising from dynamical interactions during their early evolution in small clusters. Our conclusions are based on numerical calculations of the internal cluster dynamics as well as on Monte-Carlo models. Accounting for recent observational constraints on the sub-stellar mass function and initial properties in fragmenting star forming clumps, we derive multiplicity fractions, mass ratios, separation distributions, and velocity dispersions. We compare them with observations of brown dwarfs in the field and in young clusters. Observed brown dwarf companion fractions around 15 +/- 7% for very low-mass stars as reported recently by Close et al. (\\cite{CSFB03}) are consistent with certain dynamical decay models. A significantly smaller mean separation distribution for brown dwarf binaries than for binaries of late-type stars can be explained by similar specific energy at the time of cluster formation for all cluster masses. Due to their higher velocity dispersions, brown-dwarfs and low-mass single stars will undergo time-dependent spatial segregation from higher-mass stars and multiple systems. This will cause mass functions and binary statistics in star forming regions to vary with the age of the region and the volume sampled.

Sonora: A New Generation Model Atmosphere Grid for Brown Dwarfs and Young Extrasolar Giant Planets

NASA Astrophysics Data System (ADS)

Marley, Mark S.; Saumon, Didier; Fortney, Jonathan J.; Morley, Caroline; Lupu, Roxana E.; Freedman, Richard; Visscher, Channon

2017-06-01

Brown dwarf and giant planet atmospheric structure and composition has been studied both by forward models and, increasingly so, by retrieval methods. While indisputably informative, retrieval methods are of greatest value when judged in the context of grid model predictions. Meanwhile retrieval models can test the assumptions inherent in the forward modeling procedure.In order to provide a new, systematic survey of brown dwarf atmospheric structure, emergent spectra, and evolution, we have constructed a new grid of brown dwarf model atmospheres. We ultimately aim for our grid to span substantial ranges of atmospheric metallilcity, C/O ratios, cloud properties, atmospheric mixing, and other parameters. Spectra predicted by our modeling grid can be compared to both observations and retrieval results to aid in the interpretation and planning of future telescopic observations.We thus present Sonora, a new generation of substellar atmosphere models, appropriate for application to studies of L, T, and Y-type brown dwarfs and young extrasolar giant planets. The models describe the expected temperature-pressure profile and emergent spectra of an atmosphere in radiative-convective equilibrium for ranges of effective temperatures and gravities encompassing 200 ≤ Teff ≤ 2400 K and 2.5 ≤ log g ≤ 5.5. In our poster we briefly describe our modeling methodology, enumerate various updates since our group's previous models, and present our initial tranche of models for cloudless, solar metallicity, and solar carbon-to-oxygen ratio, chemical equilibrium atmospheres. These models will be available online and will be updated as opacities and cloud modeling methods continue to improve.

Coronagraphic Imaging with HST and STIS

NASA Technical Reports Server (NTRS)

Grady, C. A.; Proffitt, C.; Malumuth, E.; Woodgate, B. E.; Gull, T. R.; Bowers, C. W.; Heap, S. R.; Kimble, R. A.; Lindler, D.; Plait, P.

2002-01-01

Revealing faint circumstellar nebulosity and faint stellar or substellar companions to bright stars typically requires use of techniques for rejecting the direct, scattered, and diffracted light of the star. One such technique is Lyot coronagraphy. We summarize the performance of the white-light coronagraphic capability of the Space Telescope Imaging spectrograph, on board the Hubble Space Telescope.

T dwarfs all the way to 550 K?

NASA Astrophysics Data System (ADS)

Burningham, Ben; Pinfield, D. J.; Leggett, S. K.; Tamura, M.; Lucas, P. W.; Homeier, D.

2009-02-01

We highlight recent results from the UKIDSS Large Area Survey (LAS) including a T dwarf with an estimated Teff = 550-600 K and new constraints on the substellar mass function in the field. We also define the T9 subtype as an extension to the T spectral sequence defined by Burgasser et al. (2006).

Mid infrared observations of Van Maanen 2: no substellar companion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farihi, J; Becklin, E; Macintosh, B

2004-11-03

The results of a comprehensive infrared imaging search for the putative 0.06 M{sub {circle_dot}} astrometric companion to the 4.4 pc white dwarf van Mannen 2 are reported. Adaptive optics images acquired at 3.8 {micro}m reveal a diffraction limited core of 0.09 inch and no direct evidence of a secondary. Models predict that at 5 Gyr, a 50 M{sub J} brown dwarf would be only 1 magnitude fainter than van Maanen 2 at this wavelength and the astrometric analysis suggested a separation of 0.2 inch. In the case of a chance alignment along the line of sight, a 0.4 mag excessmore » should be measured. An independent photometric observation at the same wavelength reveals no excess. In addition, there exist published ISO observations of van Maanen 2 at 6.8 {micro}m and 15.0 {micro}m which are consistent with photospheric flux of a 6750 K white dwarf. If recent brown dwarf models are correct, there is no substellar companion with T{sub eff} {approx}> 500 K.« less

The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

NASA Technical Reports Server (NTRS)

Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagne, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob;

The Physics of Extrasolar Gaseous Planets : from Theory to Observable Signatures

NASA Astrophysics Data System (ADS)

Chabrier, G.; Allard, F.; Baraffe, I.; Barman, T.; Hauschildt, P. H.

2004-12-01

We review our present understanding of the physical properties of substellar objects, brown dwarfs and irradiated or non-irradiated gaseous exoplanets. This includes a description of their internal properties, mechanical structure and heat content, their atmospheric properties, thermal profile and emergent spectrum, and their evolution, in particular as irradiated companions of a close parent star. The general theory can be used to make predictions in term of detectability for the future observational projects. Special attention is devoted to the evolution of the two presently detected transit planets, HD 209458b and OGLE-TR-56B. For this latter, we present a consistent evolution for its recently revised mass and show that we reproduce the observed radius within its error bars. We briefly discuss differences between brown dwarfs and gaseous planets, both in terms of mass function and formation process. We outline several arguments to show that the minimum mass for deuterium burning, recently adopted officially as the limit to distinguish the two types of objects, is unlikely to play any specific role in star formation, so that such a limit is of purely semantic nature and is not supported by a physical justification.

The young, tight, and low-mass binary TWA22AB: a new calibrator for evolutionary models?. Orbit, spectral types, and temperature

NASA Astrophysics Data System (ADS)

Bonnefoy, M.; Chauvin, G.; Dumas, C.; Lagrange, A.-M.; Beust, H.; Desort, M.; Teixeira, R.; Ducourant, C.; Beuzit, J.-L.; Song, I.

2009-11-01

Context: Tight binaries discovered in young, nearby associations are ideal targets for providing dynamical mass measurements to test the physics of evolutionary models at young ages and very low masses. Aims: We report the binarity of TWA22 for the first time. We aim at monitoring the orbit of this young and tight system to determine its total dynamical mass using an accurate distance determination. We also intend to characterize the physical properties (luminosity, effective temperature, and surface gravity) of each component based on near-infrared photometric and spectroscopic observations. Methods: We used the adaptive-optics assisted imager NACO to resolve the components, to monitor the complete orbit and to obtain the relative near-infrared photometry of TWA22 AB. The adaptive-optics assisted integral field spectrometer SINFONI was also used to obtain medium-resolution (Rλ=1500-2000) spectra in JHK bands. Comparison with empirical and synthetic librairies were necessary for deriving the spectral type, the effective temperature, and the surface gravity for each component of the system. Results: Based on an accurate trigonometric distance (17.5 ± 0.2 pc) determination, we infer a total dynamical mass of 220 ± 21 MJup for the system. From the complete set of spectra, we find an effective temperature T_eff=2900+200-200 K for TWA22 A and T_eff=2900+200-100 K for TWA22 B and surface gravities between 4.0 and 5.5 dex. From our photometry and an M6 ± 1 spectral type for both components, we find luminosities of log(L/L⊙) = -2.11 ± 0.13 dex and log(L/L⊙) = -2.30 ± 0.16 dex for TWA22 A and B, respectively. By comparing these parameters with evolutionary models, we question the age and the multiplicity of this system. We also discuss a possible underestimation of the mass predicted by evolutionary models for young stars close to the substellar boundary. Based on service-mode observations (072.C-0644, 073.C-0469, 075.C-0521, 076.C-0554, 078.C-0510, 080.C-0581) collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile.

A Combined Very Large Telescope and Gemini Study of the Atmosphere of the Directly Imaged Planet, Beta Pictoris b

NASA Technical Reports Server (NTRS)

Currie, Thayne; Burrows, Adam; Madhusudhan, Nikku; Fukagawa, Misato; Girard, Julien H.; Dawson, Rebekah; Murray-Clay, Ruth; Kenyon, Scott; Kuchner, Marc J.; Matsumura, Soko;

Dynamical analysis of nearby clusters. Automated astrometry from the ground: precision proper motions over a wide field

NASA Astrophysics Data System (ADS)

Bouy, H.; Bertin, E.; Moraux, E.; Cuillandre, J.-C.; Bouvier, J.; Barrado, D.; Solano, E.; Bayo, A.

2013-06-01

Context. The kinematic properties of the different classes of objects in a given association hold important clues about the history of its members, and offer a unique opportunity to test the predictions of the various models of stellar formation and evolution. Aims: DANCe (standing for dynamical analysis of nearby clusters) is a survey program aimed at deriving a comprehensive and homogeneous census of the stellar and substellar content of a number of nearby (<1 kpc) young (<500 Myr) associations. Whenever possible, members will be identified based on their kinematics properties, ensuring little contamination from background and foreground sources. Otherwise, the dynamics of previously confirmed members will be studied using the proper motion measurements. We present here the method used to derive precise proper motion measurements, using the Pleiades cluster as a test bench. Methods: Combining deep wide-field multi-epoch panchromatic images obtained at various obervatories over up to 14 years, we derived accurate proper motions for the sources in the field of the survey. The datasets cover ≈80 square degrees, centered around the Seven Sisters. Results: Using new tools, we have computed a catalog of 6 116 907 unique sources, including proper motion measurements for 3 577 478 of them. The catalog covers the magnitude range between i = 12 ~ 24 mag, achieving a proper motion accuracy <1 mas y-1 for sources as faint as i = 22.5 mag. We estimate that our final accuracy reaches 0.3 mas yr-1 in the best cases, depending on magnitude, observing history, and the presence of reference extragalactic sources for the anchoring onto the ICRS. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii.

Temperate Earth-sized planets transiting a nearby ultracool dwarf star

PubMed Central

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M.; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam; Triaud, Amaury H. M. J.; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K.; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2017-01-01

Stellar-like objects with effective temperatures of 2700K and below are referred to as “ultracool dwarfs”1. This heterogeneous group includes both extremely low-mass stars and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for ultracool dwarfs predicts a large, but heretofore undetected population of close-in terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable volatile-rich Earth-sized planets7. Here we report the discovery of three short-period Earth-sized planets transiting an ultracool dwarf star 12 parsecs away using data collected by the TRAPPIST8 telescope as part of an ongoing prototype transit survey9. The inner two planets receive four and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star10. Eleven orbits remain possible for the third planet based on our data, the most likely resulting in an irradiation significantly smaller than Earth's. The infrared brightness of the host star combined with its Jupiter-like size offer the possibility of thoroughly characterizing the components of this nearby planetary system. PMID:27135924

A MASSIF Effort To Determine The Mass-Luminosity Relation for Stars of Various Ages, Metallicities, and Evolution States

NASA Technical Reports Server (NTRS)

Henry, Todd J.; Beedict, G. Fritz; Gies, Douglas R.; Golimowski, David A.; Ianna, Philip A.; Mason, Brian; McArthur, Barbara; Nelan, Edmund; Torres, Guillermo

2004-01-01

The MASSIF (Masses and Stellar Systems with Interferometry) Team will use SIM to investigate the mass content of the Galaxy - from huge stars to barely glimmering brown dwarfs, and from hot white dwarfs to exotic black holes. We will target various samples of the Galactic population to determine and relate the fundamental characteristics of mass, luminosity, age, composition, and multiplicity - attributes that together yield an extensive understanding of the stars. Our samples will include distant clusters that span a factor of 5000 in age, and commonplace stars and substellar objects that lurk near the Sun. The principal goals of the MASSIF Key Project are to (1) define the mass-luminosity relation for main sequence stars in five fundamental clusters so that effects of age and metallicity can be mapped (Trapezium, TW Hydrae, Pleiades, Hyades, and M67), and (2) determine accurate masses for representative examples of nearly every type of star, stellar descendant or brown dwarf in the Galaxy.

Direct Spectrum of the Benchmark T Dwarf HD 19467 B

NASA Astrophysics Data System (ADS)

Crepp, Justin R.; Rice, Emily L.; Veicht, Aaron; Aguilar, Jonathan; Pueyo, Laurent; Giorla, Paige; Nilsson, Ricky; Luszcz-Cook, Statia H.; Oppenheimer, Rebecca; Hinkley, Sasha; Brenner, Douglas; Vasisht, Gautam; Cady, Eric; Beichman, Charles A.; Hillenbrand, Lynne A.; Lockhart, Thomas; Matthews, Christopher T.; Roberts, Lewis C., Jr.; Sivaramakrishnan, Anand; Soummer, Remi; Zhai, Chengxing

2015-01-01

HD 19467 B is presently the only directly imaged T dwarf companion known to induce a measurable Doppler acceleration around a solar-type star. We present spectroscopy measurements of this important benchmark object taken with the Project 1640 integral field unit at Palomar Observatory. Our high-contrast R ≈ 30 observations obtained simultaneously across the JH bands confirm the cold nature of the companion as reported from the discovery article and determine its spectral type for the first time. Fitting the measured spectral energy distribution to SpeX/IRTF T dwarf standards and synthetic spectra from BT-Settl atmospheric models, we find that HD 19467 B is a T5.5 ± 1 dwarf with effective temperature T_eff=978+20-43 K. Our observations reveal significant methane absorption affirming its substellar nature. HD 19467 B shows promise to become the first T dwarf that simultaneously reveals its mass, age, and metallicity independent from the spectrum of light that it emits.

DIFFICULTY IN THE FORMATION OF COUNTER-ORBITING HOT JUPITERS FROM NEAR-COPLANAR HIERARCHICAL TRIPLE SYSTEMS: A SUB-STELLAR PERTURBER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Yuxin; Suto, Yasushi, E-mail: yuxin@utap.phys.s.u-tokyo.ac.jp

2016-03-20

Among 100 transiting planets with a measured projected spin–orbit angle λ, several systems are suggested to be counter-orbiting. While these cases may be due to the projection effect, the mechanism that produces a counter-orbiting planet has not been established. A promising scenario for counter-orbiting planets is the extreme eccentricity evolution in near-coplanar hierarchical triple systems with eccentric inner and outer orbits. We examine this scenario in detail by performing a series of systematic numerical simulations, and consider the possibility of forming hot Jupiters (HJs), especially a counter-orbiting one under this mechanism with a distant sub-stellar perturber. We incorporate quadrupole andmore » octupole secular gravitational interaction between the two orbits, and also short-range forces (correction for general relativity, star and inner planetary tide, and rotational distortion) simultaneously. We find that most systems are tidally disrupted and that a small fraction of the surviving planets turn out to be prograde. The formation of counter-orbiting HJs in this scenario is possible only in a very restricted parameter region, and thus is very unlikely in practice.« less

HIGH-RESOLUTION SPECTROSCOPY DURING ECLIPSE OF THE YOUNG SUBSTELLAR ECLIPSING BINARY 2MASS 0535-0546. II. SECONDARY SPECTRUM: NO EVIDENCE THAT SPOTS CAUSE THE TEMPERATURE REVERSAL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohanty, Subhanjoy; Stassun, Keivan G., E-mail: s.mohanty@imperial.ac.uk, E-mail: keivan.stassun@vanderbilt.edu

2012-10-10

We present high-resolution optical spectra of the young brown dwarf eclipsing binary 2M0535-05, obtained during eclipse of the higher-mass (primary) brown dwarf. Combined with our previous spectrum of the primary alone (Paper I), the new observations yield the spectrum of the secondary alone. We investigate, through a differential analysis of the two binary components, whether cool surface spots are responsible for suppressing the temperature of the primary. In Paper I, we found a significant discrepancy between the empirical surface gravity of the primary and that inferred via fine analysis of its spectrum. Here we find precisely the same discrepancy inmore » surface gravity, both qualitatively and quantitatively. While this may again be ascribed to either cool spots or model opacity errors, it implies that cool spots cannot be responsible for preferentially lowering the temperature of the primary: if they were, spot effects on the primary spectrum should be preferentially larger, and they are not. The T{sub eff}'s we infer for the primary and secondary, from the TiO-{epsilon} bands alone, show the same reversal, in the same ratio, as is empirically observed, bolstering the validity of our analysis. In turn, this implies that if suppression of convection by magnetic fields on the primary is the fundamental cause of the T{sub eff} reversal, then it cannot be a local suppression yielding spots mainly on the primary (though both components may be equally spotted), but a global suppression in the interior of the primary. We briefly discuss current theories of how this might work.« less

Sonora: A New Generation Model Atmosphere Grid for Brown Dwarfs and Young Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

Marley, Mark S.; Saumon, Didier; Fortney, Jonathan J.; Morley, Caroline; Lupu, Roxana Elena; Freedman, Richard; Visscher, Channon

2017-01-01

Brown dwarf and giant planet atmospheric structure and composition has been studied both by forward models and, increasingly so, by retrieval methods. While indisputably informative, retrieval methods are of greatest value when judged in the context of grid model predictions. Meanwhile retrieval models can test the assumptions inherent in the forward modeling procedure. In order to provide a new, systematic survey of brown dwarf atmospheric structure, emergent spectra, and evolution, we have constructed a new grid of brown dwarf model atmospheres. We ultimately aim for our grid to span substantial ranges of atmospheric metallilcity, C/O ratios, cloud properties, atmospheric mixing, and other parameters. Spectra predicted by our modeling grid can be compared to both observations and retrieval results to aid in the interpretation and planning of future telescopic observations. We thus present Sonora, a new generation of substellar atmosphere models, appropriate for application to studies of L, T, and Y-type brown dwarfs and young extrasolar giant planets. The models describe the expected temperature-pressure profile and emergent spectra of an atmosphere in radiative-convective equilibrium for ranges of effective temperatures and gravities encompassing 200 less than or equal to T(sub eff) less than or equal to 2400 K and 2.5 less than or equal to log g less than or equal to 5.5. In our poster we briefly describe our modeling methodology, enumerate various updates since our group's previous models, and present our initial tranche of models for cloudless, solar metallicity, and solar carbon-to-oxygen ratio, chemical equilibrium atmospheres. These models will be available online and will be updated as opacities and cloud modeling methods continue to improve.

A Search for Low Mass Stars and Substellar Companions and A Study of Circumbinary Gas and Dust Disks

NASA Astrophysics Data System (ADS)

Rodriguez, David R.

2011-01-01

We have searched for nearby low-mass stars and brown dwarfs and have studied the planet-forming environment of binary stars. We have carried out a search for young, low-mass stars in nearby stellar associations using X-ray and UV source catalogs. We discovered a new technique to identify 10-100 Myr-old low-mass stars within 100 pc of the Earth using GALEX-optical/near-IR data. We present candidate young stars found by applying this new method in the 10 Myr old TW Hydrae and Scorpius-Centaurus associations. In addition, we have searched for the coolest brown dwarf class: Y-dwarfs, expected to appear at temperatures <500 K. Using wide-field near infrared imaging with ground (CTIO, Palomar, KPNO) and space (Spitzer, AKARI) observatories, we have looked for companions to nearby, old (2 Gyr or older), high proper motion white dwarfs. We present results for Southern Hemisphere white dwarfs. Additionally, we have characterized how likely planet formation occurs in binary star systems. While 20% of planets have been discovered around one member of a binary system, these binaries have semi-major axes larger than 20 AU. We have performed an AO and spectroscopic search for binary stars among a sample of known debris disk stars, which allows us to indirectly study planet formation and evolution in binary systems. As a case study, we examined the gas and dust present in the circumbinary disk around V4046 Sagittarii, a 2.4-day spectroscopic binary. Our results demonstrate it is unlikely that planets can form in binaries with stellar semi-major axes of 10s of AU. This research has been funded by a NASA ADA grant to UCLA and RIT.

The UKIRT Infrared Deep Sky Survey (UKIDSS)

NASA Astrophysics Data System (ADS)

Lawrence, A.; Warren, S. J.; Almaini, O.; Edge, A. C.; Hambly, N. C.; Jameson, R. F.; Lucas, P.; Casali, M.; Adamson, A.; Dye, S.; Emerson, J. P.; Foucaud, S.; Hewett, P.; Hirst, P.; Hodgkin, S. T.; Irwin, M. J.; Lodieu, N.; McMahon, R. G.; Simpson, C.; Smail, I.; Mortlock, D.; Folger, M.

2007-08-01

We describe the goals, design, implementation, and initial progress of the UKIRT Infrared Deep Sky Survey (UKIDSS), a seven-year sky survey which began in 2005 May. UKIDSS is being carried out using the UKIRT Wide Field Camera (WFCAM), which has the largest étendue of any infrared astronomical instrument to date. It is a portfolio of five survey components covering various combinations of the filter set ZYJHK and H2. The Large Area Survey, the Galactic Clusters Survey, and the Galactic Plane Survey cover approximately 7000deg2 to a depth of K ~ 18; the Deep Extragalactic Survey covers 35deg2 to K ~ 21, and the Ultra Deep Survey covers 0.77deg2 to K ~ 23. Summed together UKIDSS is 12 times larger in effective volume than the 2MASS survey. The prime aim of UKIDSS is to provide a long-term astronomical legacy data base; the design is, however, driven by a series of specific goals - for example, to find the nearest and faintest substellar objects, to discover Population II brown dwarfs, if they exist, to determine the substellar mass function, to break the z = 7 quasar barrier; to determine the epoch of re-ionization, to measure the growth of structure from z = 3 to the present day, to determine the epoch of spheroid formation, and to map the Milky Way through the dust, to several kpc. The survey data are being uniformly processed. Images and catalogues are being made available through a fully queryable user interface - the WFCAM Science Archive (http://surveys.roe.ac.uk/wsa). The data are being released in stages. The data are immediately public to astronomers in all ESO member states, and available to the world after 18 months. Before the formal survey began, UKIRT and the UKIDSS consortia collaborated in obtaining and analysing a series of small science verification (SV) projects to complete the commissioning of the camera. We show some results from these SV projects in order to demonstrate the likely power of the eventual complete survey. Finally, using the data from the First Data Release, we assess how well UKIDSS is meeting its design targets so far.

Spitzer and z' secondary eclipse observations of the highly irradiated transiting brown dwarf KELT-1b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beatty, Thomas G.; Gaudi, B. Scott; Collins, Karen A.

2014-03-10

We present secondary eclipse observations of the highly irradiated transiting brown dwarf KELT-1b. These observations represent the first constraints on the atmospheric dynamics of a highly irradiated brown dwarf, the atmospheres of irradiated giant planets at high surface gravity, and the atmospheres of brown dwarfs that are dominated by external, rather than internal, energy. Using the Spitzer Space Telescope, we measure secondary eclipse depths of 0.195% ± 0.010% at 3.6 μm and 0.200% ± 0.012% at 4.5 μm. We also find tentative evidence for the secondary eclipse in the z' band with a depth of 0.049% ± 0.023%. These measuredmore » eclipse depths are most consistent with an atmosphere model in which there is a strong substellar hotspot, implying that heat redistribution in the atmosphere of KELT-1b is low. While models with a more mild hotspot or even with dayside heat redistribution are only marginally disfavored, models with complete heat redistribution are strongly ruled out. The eclipse depths also prefer an atmosphere with no TiO inversion layer, although a model with TiO inversion is permitted in the dayside heat redistribution case, and we consider the possibility of a day-night TiO cold trap in this object. For the first time, we compare the IRAC colors of brown dwarfs and hot Jupiters as a function of effective temperature. Importantly, our measurements reveal that KELT-1b has a [3.6] – [4.5] color of 0.07 ± 0.11, identical to that of isolated brown dwarfs of similarly high temperature. In contrast, hot Jupiters generally show redder [3.6] – [4.5] colors of ∼0.4, with a very large range from ∼0 to ∼1. Evidently, despite being more similar to hot Jupiters than to isolated brown dwarfs in terms of external forcing of the atmosphere by stellar insolation, KELT-1b appears to have an atmosphere most like that of other brown dwarfs. This suggests that surface gravity is very important in controlling the atmospheric systems of substellar mass bodies.« less

Ground-Based Astrometry 2010-2020

DTIC Science & Technology

2010-01-01

The two most compelling questions to be addressed are (1) What is the composition of the stellar and substellar population near the Sun? and (2) What ...of the intellectual and financial investments made for what some have called “The Decade of Astrometry.” The most important recommendation is to...measurements in astronomy is the trigonometric parallax, which forms the fundamental rung in the astronomical distance ladder. Advances in

The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

NASA Astrophysics Data System (ADS)

Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagné, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob; Mokaev, Khasan; Stajic, Tamara

2017-06-01

The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding nearby brown dwarfs and searching for new planets in the outer solar system, especially with the incorporation of NEOWISE and NEOWISE-Reactivation data. However, so far, searches for brown dwarfs in WISE data have yet to take advantage of the full depth of the WISE images. To efficiently search this unexplored space via visual inspection, we have launched a new citizen science project, called “Backyard Worlds: Planet 9,” which asks volunteers to examine short animations composed of difference images constructed from time-resolved WISE coadds. We report the first new substellar object discovered by this project, WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from the Sun with a total proper motion of ˜0.″7 {{yr}}-1. WISEA J110125.95+540052.8 has a WISE W2 magnitude of W2=15.37+/- 0.09; our sensitivity to this source demonstrates the ability of citizen scientists to identify moving objects via visual inspection that are 0.9 mag fainter than the W2 single-exposure sensitivity, a threshold that has limited prior motion-based brown dwarf searches with WISE.

High-contrast imaging of the close environment of HD 142527. VLT/NaCo adaptive optics thermal and angular differential imaging

NASA Astrophysics Data System (ADS)

Rameau, J.; Chauvin, G.; Lagrange, A.-M.; Thébault, P.; Milli, J.; Girard, J. H.; Bonnefoy, M.

2012-10-01

Context. It has long been suggested that circumstellar disks surrounding young stars may be the signposts of planets, and even more so since the recent discoveries of embedded substellar companions. According to models, the planet-disk interaction may create large structures, gaps, rings, or spirals in the disk. In that sense, the Herbig star HD 142527 is particularly compelling, as its massive disk displays intriguing asymmetries that suggest the existence of a dynamical peturber of unknown nature. Aims: Our goal was to obtain deep thermal images of the close circumstellar environment of HD 142527 to re-image the reported close-in structures (cavity, spiral arms) of the disk and to search for stellar and substellar companions that could be connected to their presence. Methods: We obtained high-contrast images with the NaCo adaptive optics system at the Very Large Telescope in L'-band. We applied different analysis strategies using both classical PSF-subtraction and angular differential imaging to probe for any extended structures or point-like sources. Results: The circumstellar environment of HD 142527 is revealed at an unprecedented spatial resolution down to the subarcsecond level for the first time at 3.8 μm. Our images reveal important radial and azimuthal asymmetries that invalidate an elliptical shape for the disk. It instead suggests a bright inhomogeneous spiral arm plus various fainter spiral arms. We also confirm an inner cavity down to 30 AU and two important dips at position angles of 0 and 135 deg. The detection performance in angular differential imaging enables exploration of the planetary mass regime for projected physical separations as close as 40 AU. Use of our detection map together with Monte Carlo simulations sets stringent constraints on the presence of planetary mass, brown dwarf or stellar companions as a function of the semi-major axis. They severely limit any presence of massive giant planets with semi-major axis beyond 50 AU, i.e. probably within the large disk's cavity which extends radially up to 145 AU or even farther outside. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, ESO: run 087.C-0299A.Reduced images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/A24

A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf "Lithium Test" at Early Ages

NASA Astrophysics Data System (ADS)

Kirkpatrick, J. Davy; Cruz, Kelle L.; Barman, Travis S.; Burgasser, Adam J.; Looper, Dagny L.; Tinney, C. G.; Gelino, Christopher R.; Lowrance, Patrick J.; Liebert, James; Carpenter, John M.; Hillenbrand, Lynne A.; Stauffer, John R.

2008-12-01

Using a large sample of optical spectra of late-type dwarfs, we identify a subset of late-M through L field dwarfs that, because of the presence of low-gravity features in their spectra, are believed to be unusually young. From a combined sample of 303 field L dwarfs, we find observationally that 7.6% +/- 1.6% are younger than 100 Myr. This percentage is in agreement with theoretical predictions once observing biases are taken into account. We find that these young L dwarfs tend to fall in the southern hemisphere (decl . < 0°) and may be previously unrecognized, low-mass members of nearby, young associations like Tucana-Horologium, TW Hydrae, β Pictoris, and AB Doradus. We use a homogeneously observed sample of ~150 optical spectra to examine lithium strength as a function of L/T spectral type and further corroborate the trends noted by Kirkpatrick and coworkers. We use our low-gravity spectra to investigate lithium strength as a function of age. The data weakly suggest that for early- to mid-L dwarfs the line strength reaches a maximum for a few × 100 Myr, whereas for much older (few Gyr) and much younger (<100 Myr) L dwarfs the line is weaker or undetectable. We show that a weakening of lithium at lower gravities is predicted by model atmosphere calculations, an effect partially corroborated by existing observational data. Larger samples containing L dwarfs of well-determined ages are needed to further test this empirically. If verified, this result would reinforce the caveat first cited by Kirkpatrick and coworkers that the lithium test should be used with caution when attempting to confirm the substellar nature of the youngest brown dwarfs. Most of the spectroscopic data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Other spectroscopic data were collected at the Subaru Telescope, the twin telescopes of the Gemini Observatory, the Magellan-Clay Telescope, the Kitt Peak National Observatory Mayall Telescope, and the Cerro Tololo Interamerican Observatory Blanco Telescope.

M Dwarfs From The SDSS, 2MASS and WISE Surveys: Identification, Characterisation and Unresolved Ultracool Companionship

NASA Astrophysics Data System (ADS)

Cook, Neil James

2016-08-01

The aim of this thesis is to use a cross-match between WISE, 2MASS and SDSS to identify a large sample of M dwarfs. Through the careful characterisation and quality control of these M dwarfs I aim to identify rare systems (i.e. unresolved UCD companions, young M dwarfs, late M dwarfs and M dwarfs with common proper motion companions). Locating ultracool companions to M dwarfs is important for constraining low-mass formation models, the measurement of substellar dynamical masses and radii, and for testing ultracool evolutionary models. This is done by using an optimised method for identifying M dwarfs which may have unresolved ultracool companions. To do this I construct a catalogue of 440 694 M dwarf candidates, from WISE, 2MASS and SDSS, based on optical- and near-infrared colours and reduced proper motion. With strict reddening, photometric and quality constraints I isolate a sub-sample of 36 898 M dwarfs and search for possible mid-infrared M dwarf + ultracool dwarf candidates by comparing M dwarfs which have similar optical/near-infrared colours (chosen for their sensitivity to effective temperature and metallicity). I present 1 082 M dwarf + ultracool dwarf candidates for follow-up. Using simulated ultracool dwarf companions to M dwarfs, I estimate that the occurrence of unresolved ultracool companions amongst my M dwarf + ultracool dwarf candidates should be at least four times the average for my full M dwarf catalogue. I discuss yields of candidates based on my simulations. The possible contamination and bias from misidentified M dwarfs is then discussed, from chance alignments with other M dwarfs and UCDs, from chance alignments with giant stars, from chance alignments with galaxies, and from blended systems (via visual inspection). I then use optical spectra from LAMOST to spectral type a subset of my M dwarf + ultracool dwarf candidates. These candidates need confirming as true M dwarf + ultracool dwarf systems thus I present a new method I developed to use low resolution near-infrared spectra which relies on two colour similar objects (one an excess candidate, one not) having very similar spectra. A spectral difference of these two colour similar objects should leave the signature of a UCD in the residual of their differences, which I look for using the difference in two spectral bands designed to identify UCD spectral features. I then present the methods used to identify other rare systems from my full M dwarf catalogue. Young M dwarfs were identified by measuring equivalent widths of Hα from the LAMOST spectra, and by measuring rotation periods from Kepler 2 light curves. I identify late M dwarfs photometrically (using reduced proper motion and colour cuts) and spectroscopically (using the LAMOST spectra with spectral indices from the literature). Also I present common proper motion analysis aimed at finding Tycho-2 primaries for my M dwarfs and look for physically separated M dwarf + M dwarf pairs (internally within my full M dwarf catalogue).

The Young Substellar Companion ROXs 12 B: Near-infrared Spectrum, System Architecture, and Spin-Orbit Misalignment

NASA Astrophysics Data System (ADS)

Bowler, Brendan P.; Kraus, Adam L.; Bryan, Marta L.; Knutson, Heather A.; Brogi, Matteo; Rizzuto, Aaron C.; Mace, Gregory N.; Vanderburg, Andrew; Liu, Michael C.; Hillenbrand, Lynne A.; Cieza, Lucas A.

2017-10-01

ROXs 12 (2MASS J16262803-2526477) is a young star hosting a directly imaged companion near the deuterium-burning limit. We present a suite of spectroscopic, imaging, and time-series observations to characterize the physical and environmental properties of this system. Moderate-resolution near-infrared spectroscopy of ROXs 12 B from Gemini-North/NIFS and Keck/OSIRIS reveals signatures of low surface gravity including weak alkali absorption lines and a triangular H-band pseudocontinuum shape. No signs of Paβ emission are evident. As a population, however, we find that about half (46% ± 14%) of young (≲15 Myr) companions with masses ≲20 M Jup possess actively accreting subdisks detected via Paβ line emission, which represents a lower limit on the prevalence of circumplanetary disks in general, as some are expected to be in a quiescent phase of accretion. The bolometric luminosity of the companion and age of the host star ({6}-2+4 Myr) imply a mass of 17.5 ± 1.5 M Jup for ROXs 12 B based on hot-start evolutionary models. We identify a wide (5100 au) tertiary companion to this system, 2MASS J16262774-2527247, that is heavily accreting and exhibits stochastic variability in its K2 light curve. By combining v sin I * measurements with rotation periods from K2, we constrain the line-of-sight inclinations of ROXs 12 A and 2MASS J16262774-2527247 and find that they are misaligned by {{60}-11+7}^\\circ . In addition, the orbital axis of ROXs 12 B is likely misaligned from the spin axis of its host star, ROXs 12 A, suggesting that ROXs 12 B formed akin to fragmenting binary stars or in an equatorial disk that was torqued by the wide stellar tertiary. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Fragment Production and Survival in Irradiated Disks: A Comprehensive Cooling Criterion

NASA Astrophysics Data System (ADS)

Kratter, Kaitlin M.; Murray-Clay, Ruth A.

2011-10-01

Accretion disks that become gravitationally unstable can fragment into stellar or substellar companions. The formation and survival of these fragments depends on the precarious balance between self-gravity, internal pressure, tidal shearing, and rotation. Disk fragmentation depends on two key factors: (1) whether the disk can get to the fragmentation boundary of Q = 1 and (2) whether fragments can survive for many orbital periods. Previous work suggests that to reach Q = 1, and have fragments survive, a disk must cool on an orbital timescale. Here we show that disks heated primarily by external irradiation always satisfy the standard cooling time criterion. Thus, even though irradiation heats disks and makes them more stable in general, once they reach the fragmentation boundary, they fragment more easily. We derive a new cooling criterion that determines fragment survival and calculate a pressure-modified Hill radius, which sets the maximum size of pressure-supported objects in a Keplerian disk. We conclude that fragmentation in protostellar disks might occur at slightly smaller radii than previously thought and recommend tests for future simulations that will better predict the outcome of fragmentation in real disks.

DIRECT SPECTRUM OF THE BENCHMARK T DWARF HD 19467 B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crepp, Justin R.; Matthews, Christopher T.; Rice, Emily L.

2015-01-10

HD 19467 B is presently the only directly imaged T dwarf companion known to induce a measurable Doppler acceleration around a solar-type star. We present spectroscopy measurements of this important benchmark object taken with the Project 1640 integral field unit at Palomar Observatory. Our high-contrast R ≈ 30 observations obtained simultaneously across the JH bands confirm the cold nature of the companion as reported from the discovery article and determine its spectral type for the first time. Fitting the measured spectral energy distribution to SpeX/IRTF T dwarf standards and synthetic spectra from BT-Settl atmospheric models, we find that HD 19467 B is a T5.5more » ± 1 dwarf with effective temperature T{sub eff}=978{sub −43}{sup +20} K. Our observations reveal significant methane absorption affirming its substellar nature. HD 19467 B shows promise to become the first T dwarf that simultaneously reveals its mass, age, and metallicity independent from the spectrum of light that it emits.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geier, S.; Classen, L.; Heber, U., E-mail: geier@sternwarte.uni-erlangen.de

Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose almost all of its hydrogen envelope right at the tip of the red-giant branch. In binary systems, mass transfer to the companion provides the extraordinary mass loss required for their formation. However, apparently single sdBs exist as well and their formation has been unclear for decades. The merger of helium white dwarfs (He-WDs) leading to an ignition of core helium burning or the merger of a helium core and a low-mass star during themore » common envelope phase have been proposed as processes leading to sdB formation. Here we report the discovery of EC 22081-1916 as a fast-rotating, single sdB star of low gravity. Its atmospheric parameters indicate that the hydrogen envelope must be unusually thick, which is at variance with the He-WD merger scenario, but consistent with a common envelope merger of a low-mass, possibly substellar object with a red-giant core.« less

DISCOVERY OF A LOW-MASS COMPANION AROUND HR 3549

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mawet, D.; David, T.; Bottom, M.

2015-10-01

We report the discovery of a low-mass 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 thismore » system 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.« less

Social object play among young Japanese macaques (Macaca fuscata) in Arashiyama, Japan.

PubMed

Shimada, Masaki

2006-10-01

Social object play (SOP), i.e., social play using portable object(s), among young Japanese macaques (Macaca fuscata; 0-4 years old) in the Arashiyama E troop was studied using a modified sequence sampling method from July to October 2000. SOP was a relatively common activity for most of the young macaques and often continued for long periods. Participants used many kinds of object, including edible natural objects and artificial objects, such as plastic bottles, but they never used provisioned food or wild fruit in SOP bouts. An analysis of long bouts (>/=0.5 min) revealed the following interactive SOP features: (1) at any given time, participants used only one object, and only one participant held the object; (2) during SOP play-chasing, the object holder was likely to be chased by others; (3) during long bouts, the object changed hands frequently; and (4) agonistic competition for an object among young macaques was rare. Combinations of sexes, ages, relative ranks, or matrilines of the object holder and non-holder did not affect the tendency that the holder was chased by non-holder(s) during play-chasing. Even when there was a change in object holders, the repetitiveness of this interactive pattern, i.e., that the holder would be chased during SOP bouts, distinguished the SOP structure from that of other types of social play without object(s). General proximate social play mechanisms, such as self-handicapping or role taking, were associated with SOP. Other mechanisms that affected SOP included the following: (1) young macaques treated an object as a target in play competition, and (2) 'being the holder of a target object' was associated with the 'role of the chasee.'

The VAST Survey - IV. A wide brown dwarf companion to the A3V star ζ Delphini

NASA Astrophysics Data System (ADS)

De Rosa, R. J.; Patience, J.; Ward-Duong, K.; Vigan, A.; Marois, C.; Song, I.; Macintosh, B.; Graham, J. R.; Doyon, R.; Bessell, M. S.; Lai, O.; McCarthy, D. W.; Kulesa, C.

2014-12-01

We report the discovery of a wide comoving substellar companion to the nearby (D = 67.5 ± 1.1 pc) A3V star ζ Delphini based on imaging and follow-up spectroscopic observations obtained during the course of our Volume-limited A-Star (VAST) multiplicity survey. ζ Del was observed over a five-year baseline with adaptive optics, revealing the presence of a previously unresolved companion with a proper motion consistent with that of the A-type primary. The age of the ζ Del system was estimated as 525 ± 125 Myr based on the position of the primary on the colour-magnitude and temperature-luminosity diagrams. Using intermediate-resolution near-infrared spectroscopy, the spectrum of ζ Del B is shown to be consistent with a mid-L dwarf (L5 ± 2), at a temperature of 1650 ± 200 K. Combining the measured near-infrared magnitude of ζ Del B with the estimated temperature leads to a model-dependent mass estimate of 50 ± 15 MJup, corresponding to a mass ratio of q = 0.019 ± 0.006. At a projected separation of 910 ± 14 au, ζ Del B is among the most widely separated and extreme-mass ratio substellar companions to a main-sequence star resolved to date, providing a rare empirical constraint of the formation of low-mass ratio companions at extremely wide separations.

THE EVOLUTION OF CIRCUMPLANETARY DISKS AROUND PLANETS IN WIDE ORBITS: IMPLICATIONS FOR FORMATION THEORY, OBSERVATIONS, AND MOON SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shabram, Megan; Boley, Aaron C.

2013-04-10

Using radiation hydrodynamics simulations, we explore the evolution of circumplanetary disks around wide-orbit proto-gas giants. At large distances from the star ({approx}100 AU), gravitational instability followed by disk fragmentation can form low-mass substellar companions (massive gas giants and/or brown dwarfs) that are likely to host large disks. We examine the initial evolution of these subdisks and their role in regulating the growth of their substellar companions, as well as explore consequences of their interactions with circumstellar material. We find that subdisks that form in the context of GIs evolve quickly from a very massive state. Long-term accretion rates from themore » subdisk onto the proto-gas giant reach {approx}0.3 Jupiter masses kyr{sup -1}. We also find consistency with previous simulations, demonstrating that subdisks are truncated at {approx}1/3 of the companion's Hill radius and are thick, with (h/r) of {approx}> 0.2. The thickness of subdisks draws to question the use of thin-disk approximations for understanding the behavior of subdisks, and the morphology of subdisks has implications for the formation and extent of satellite systems. These subdisks create heating events in otherwise cold regions of the circumstellar disk and serve as planet formation beacons that can be detected by instruments such as ALMA.« less

Protostellar Disk Instabilities and the Formation of Substellar Companions

NASA Astrophysics Data System (ADS)

Pickett, Brian K.; Durisen, Richard H.; Cassen, Patrick; Mejia, Annie C.

2000-09-01

Recent numerical simulations of self-gravitating protostellar 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 protostellar 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 protostellar 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 protostellar 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.

New binaries among UV-selected, hot subdwarf stars and population properties

NASA Astrophysics Data System (ADS)

Kawka, A.; Vennes, S.; O'Toole, S.; Németh, P.; Burton, D.; Kotze, E.; Buckley, D. A. H.

2015-07-01

We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ˜0.17 to 3 d. One new system, GALEX J2205-3141, shows reflection on an M dwarf companion. Three other objects show significant short-period variations, but their orbital parameters could not be constrained. Two systems comprising a hot subdwarf paired with a bright main-sequence/giant companion display short-period photometric variations possibly due to irradiation or stellar activity and are also short-period candidates. All except two candidates were drawn from a selection of subluminous stars in the Galaxy Evolution Explorer ultraviolet sky survey. Our new identifications also include a low-mass subdwarf B star and likely progenitor of a low-mass white dwarf (GALEX J0805-1058) paired with an unseen, possibly substellar, companion. The mass functions of the newly identified binaries imply minimum secondary masses ranging from 0.03 to 0.39 M⊙. Photometric time series suggest that, apart from GALEX J0805-1058 and J2205-3141, the companions are most likely white dwarfs. We update the binary population statistics: close to 40 per cent of hot subdwarfs have a companion. Also, we found that the secondary mass distribution shows a low-mass peak attributed to late-type dwarfs, and a higher mass peak and tail distribution attributed to white dwarfs and a few spectroscopic composites. Also, we found that the population kinematics imply an old age and include a few likely halo population members.

Parallaxes for the Coldest Brown Dwarfs

NASA Astrophysics Data System (ADS)

Dupuy, Trent; Kraus, Adam; Liu, Michael

2014-12-01

Understanding extremely cool atmospheres is a major goal of both brown dwarf and exoplanet studies. The WISE all-sky survey has uncovered the coolest brown dwarfs to date including the first unambiguous Y dwarfs. These discoveries are spectroscopically estimated to have temperatures of ~300-500 K and masses of ~5-20 Mjup, overlapping discoveries from radial velocity exoplanet surveys. However, direct distances are needed to determine model-independent temperatures and to test the observed properties against theoretical models in this new physical frontier. From our Cycle 8 program, we have successfully measured the first robust parallaxes for these extremely low-luminosity objects using Spitzer [3.6]-band astrometry, made possible with our improved distortion solution for IRAC. Our results, comprising less than half the currently known late-T/Y census, have uncovered a number of puzzles. Perhaps the most intriguing is the possibility that the observed near-IR spectral types and spectral energy distributions do not follow a simple correspondence with temperature, in contrast to all other (hotter) substellar and stellar objects. We propose here to obtain definitive parallaxes and temperatures to the ~2 dozen known coldest brown dwarfs. For our Cycle 8 sample, these new data will double the time baseline, leading to major improvements over our preliminary results. We will also double the total sample with parallaxes for more recent discoveries. Altogether, our work will establish the temperature scale as a function of spectral type, delineate the cooling (and intrinsic scatter) through the T/Y transition, and enable strong test of theoretical models for these coldest brown dwarfs, which are ~100x fainter than previously known objects at near-IR wavelengths.

Discarded candidate companions to low-mass members of Chamaeleon I

NASA Astrophysics Data System (ADS)

Comerón, F.

2012-01-01

Context. Direct detections of brown dwarfs and planetary-mass companions to members of nearby star-forming regions provide important clues about the process of star formation, core fragmentation, and protoplanetary disk evolution. Aims: We study two faint objects at a very small angular distance from the low-mass star ESO-Hα-558 and the possible massive brown dwarf ESO-Hα-566, both of which are members of the Chamaeleon I star-forming region, to establish whether they are physical companions to those sources. If they are, their low luminosities should imply L or T spectral types, which have clearly detectable spectral features. Methods: Adaptive optics-assisted imaging and spectroscopy of both faint candidate companions has been obtained with the NACO instrument at the Very Large Telescope (VLT). Results: Photometry shows that the colors of both objects are compatible with them being moderately reddened, normal stars in the background of the Chamaeleon I clouds. This interpretation is confirmed spectroscopically, as the spectrum between 1.4 and 2.4 μm of both objects has a featureless, monotonic slope lacking the strong H2O absorption features that dominate cool stellar and substellar spectra in that domain. Conclusions: We demonstrate that the two faint sources seen very close to ESO-Hα-558 and ESO-Hα-566 are unrelated background stars, instead of giant planetary-mass companions as might be expected based on their faintness and angular proximity. Based on observations collected with the Very Large Telescope (VLT) at the European Southern Observatory, Paranal, Chile, under observing programmes 075.C-0809(B) and 078.C-0429(C).

Young Stellar Objects from Soft to Hard X-rays

NASA Astrophysics Data System (ADS)

Güdel, Manuel

2009-05-01

Magnetically active stars are the sites of efficient particle acceleration and plasma heating, processes that have been studied in detail in the solar corona. Investigation of such processes in young stellar objects is much more challenging due to various absorption processes. There is, however, evidence for violent magnetic energy release in very young stellar objects. The impact on young stellar environments (e.g., circumstellar disk heating and ionization, operation of chemical networks, photoevaporation) may be substantial. Hard X-ray devices like those carried on Simbol-X will establish a basis for detailed studies of these processes.

Combining angular differential imaging and accurate polarimetry with SPHERE/IRDIS to characterize young giant exoplanets

NASA Astrophysics Data System (ADS)

van Holstein, Rob G.; Snik, Frans; Girard, Julien H.; de Boer, Jozua; Ginski, C.; Keller, Christoph U.; Stam, Daphne M.; Beuzit, Jean-Luc; Mouillet, David; Kasper, Markus; Langlois, Maud; Zurlo, Alice; de Kok, Remco J.; Vigan, Arthur

2017-09-01

Young giant exoplanets emit infrared radiation that can be linearly polarized up to several percent. This linear polarization can trace: 1) the presence of atmospheric cloud and haze layers, 2) spatial structure, e.g. cloud bands and rotational flattening, 3) the spin axis orientation and 4) particle sizes and cloud top pressure. We introduce a novel high-contrast imaging scheme that combines angular differential imaging (ADI) and accurate near-infrared polarimetry to characterize self-luminous giant exoplanets. We implemented this technique at VLT/SPHEREIRDIS and developed the corresponding observing strategies, the polarization calibration and the data-reduction approaches. The combination of ADI and polarimetry is challenging, because the field rotation required for ADI negatively affects the polarimetric performance. By combining ADI and polarimetry we can characterize planets that can be directly imaged with a very high signal-to-noise ratio. We use the IRDIS pupil-tracking mode and combine ADI and principal component analysis to reduce speckle noise. We take advantage of IRDIS' dual-beam polarimetric mode to eliminate differential effects that severely limit the polarimetric sensitivity (flat-fielding errors, differential aberrations and seeing), and thus further suppress speckle noise. To correct for instrumental polarization effects, we apply a detailed Mueller matrix model that describes the telescope and instrument and that has an absolute polarimetric accuracy <= 0.1%. Using this technique we have observed the planets of HR 8799 and the (sub-stellar) companion PZ Tel B. Unfortunately, we do not detect a polarization signal in a first analysis. We estimate preliminary 1σ upper limits on the degree of linear polarization of ˜ 1% and ˜ 0.1% for the planets of HR 8799 and PZ Tel B, respectively. The achieved sub-percent sensitivity and accuracy show that our technique has great promise for characterizing exoplanets through direct-imaging polarimetry

Priming of familiar and unfamiliar visual objects over delays in young and older adults.

PubMed

Soldan, Anja; Hilton, H John; Cooper, Lynn A; Stern, Yaakov

2009-03-01

Although priming of familiar stimuli is usually age invariant, little is known about how aging affects priming of preexperimentally unfamiliar stimuli. Therefore, this study investigated the effects of aging and encoding-to-test delays (0 min, 20 min, 90 min, and 1 week) on priming of unfamiliar objects in block-based priming paradigms. During the encoding phase, participants viewed pictures of novel objects (Experiments 1 and 2) or novel and familiar objects (Experiment 3) and judged their left-right orientation. In the test block, priming was measured using the possible-impossible object-decision test (Experiment 1), symmetric-asymmetric object-decision test (Experiment 2), and real-nonreal object-decision test (Experiment 3). In Experiments 1 and 2, young adults showed priming for unfamiliar objects at all delays, whereas older adults whose baseline task performance was similar to that of young adults did not show any priming. Experiment 3 found no effects of age or delay on priming of familiar objects; however, priming of unfamiliar objects was only observed in the young participants. This suggests that when older adults cannot rely on preexisting memory representations, age-related deficits in priming can emerge.

MUCHFUSS: Status and Highlights

NASA Astrophysics Data System (ADS)

Geier, S.; Kupfer, T.; Barlow, B.; Schaffenroth, V.; Fürst, F.; Heuser, C.; Ziegerer, E.; Heber, U.; Marsh, T.; Maxted, P.; Östensen, R.; O'Toole, S.; Gänsicke, B.; Napiwotzki, R.

2014-04-01

The MUCHFUSS project aims at finding sdBs with massive compact companions. Here we report on the current status of our spectroscopic and photometric follow-up campaigns and present some highlight results. We derive orbital solutions of seven new sdB binaries and estimate the fraction of close substellar companions to sdBs. Finally, we present an ultracompact sdB+WD binary as possible progenitor of a thermonuclear supernova and connect it to the only known hypervelocity subdwarf star, which might be the donor remnant of such an event.

Responding to Parental Objections to School Sexuality Education: A Selection of 12 Objections

ERIC Educational Resources Information Center

Goldman, Juliette D. G.

2008-01-01

Sexuality education for school-aged young people is a crucial component of all quality education systems. It prepares young people for participation in society as responsible, mature and community-minded citizens. Most contemporary school education curricula generally aim to enhance young people's knowledge, skills and understandings of the world,…

Associations between young children's perceived and actual ball skill competence and physical activity.

PubMed

Barnett, Lisa M; Ridgers, Nicola D; Salmon, Jo

2015-03-01

The relationship between actual and perceived object control competence (ball skills) and the contribution to young children's physical activity is not known. Cross sectional study. The Test Gross Motor Development-2 assessed actual object control competence and a modified version of the Pictorial Scale of Perceived Competence and Social Acceptance for Young Children assessed perceived object control competence. Moderate- to vigorous-intensity physical activity was measured via accelerometry. Three mixed regression models were performed: (i) object control competence as the predictor and the outcome as perceived object control, (ii) perceived object control competence as the predictor and the outcome moderate to vigorous physical activity and (iii) actual object control as the predictor and the outcome moderate to vigorous physical activity. Models adjusted for school clustering, monitor wear time, sex and age. Interactions between respective predictor variables and sex were performed if warranted. A total of 102 children (56% boys, 44% girls) aged 4-8 years (M 6.3, SD 0.92) completed assessments. Girls had lower perceived and actual object control competence and were less active than boys. Actual object control competence was positively associated with perceived object control competence (B=0.11, t(96)=2.25, p<0.001, p=0.027) and this relationship did not differ by sex (p=0.449); however, neither actual (p=0.092) nor perceived object control competence (p=0.827) were associated with moderate to vigorous physical activity. Young children's perceived ball skill abilities appear to relate to actual competence; however, these measures were not associated with physical activity. In older children, object control skill is associated with physical activity so targeting young children's object control skills is an intervention priority. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Curriculum for Young Deaf Children.

ERIC Educational Resources Information Center

Restaino, Lillian C. R.; And Others

Presented is a curriculum designed to provide the teacher of the young deaf child with learning disabilities with a description of developmental objectives and methods for fulfilling these objectives in the areas of gross motor development, sensory motor integration, visual analysis, attention and memory, and conceptualization. The objectives are…

Young People's Perceptions of the Objective Physical Activity Monitoring Process: A Qualitative Exploration

ERIC Educational Resources Information Center

Scott, Joseph J.; Hansen, Vibeke; Morgan, Philip J.; Plotnikoff, Ronald C.; Lubans, David R.

2018-01-01

Objective: To explore young people's perceptions of pedometers and investigate behaviours exhibited while being monitored. Design: Qualitative design using six focus groups with participants (mean age 14.7 years). Setting: Study participants (n = 24) were randomly selected from a previous study of 123 young people aged 14-15 years from three…

Young Infants' Reasoning about Hidden Objects: Evidence from Violation-of-Expectation Tasks with Test Trials Only

ERIC Educational Resources Information Center

Wang, Su-hua; Baillargeon, Renee; Brueckner, Laura

2004-01-01

The present research examined alternative accounts of prior violation-of-expectation (VOE) reports that young infants can represent and reason about hidden objects. According to these accounts, young infants' apparent success in these VOE tasks reflects only novelty and familiarity preferences induced by the habituation or familiarization trials…

Stellar Radial Velocities with IGRINS at McDonald Observatory

NASA Astrophysics Data System (ADS)

Mace, Gregory; Jaffe, Daniel; Park, Chan; Lee, Jae-Joon

2016-06-01

Exoplanet searches with dedicated instrumentation have made 1 m/s radial velocity (RV) precision routine.Yet, RVs for large samples of stars generally remain at the 1km/s level.TheImmersion Grating Infrared Spectrometer (IGRINS) is a revolutionary instrument that exploits broad spectral coverage at high-resolution in the near-infrared.IGRINS on the 2.7 meter Harlan J. Smith Telescope at McDonald Observatory is nearly as sensitive as CRIRES at the 8 meter Very Large Telescope. However, IGRINS at R=45,000 has more than 30 times the spectral grasp of CRIRES.The use of a silicon immersion grating facilitates a compact cryostat while providing simultaneous wavelength coverage from 1.45 - 2.45 microns. Wehave developed a pipeline to cross-correlate the more than 20,000 resolution elements in two IGRINS exposures and provide relative RVs with uncertainties of 50m/s (<1% of a resolution element). Absolute RVs are limited by thezero point uncertainty, which is 150m/s.IGRINS RVs will be provided for thousands of objects per year as a default procedure of the data reduction pipeline, creating a legacy product for multi-epoch studies of low-mass, stellar and substellar multiplicity.

How do binary separations depend on cloud initial conditions?

NASA Astrophysics Data System (ADS)

Sterzik, M. F.; Durisen, R. H.; Zinnecker, H.

2003-11-01

We explore the consequences of a star formation scenario in which the isothermal collapse of a rotating, star-forming core is followed by prompt fragmentation into a cluster containing a small number (N <~ 10) of protostars and/or substellar objects. The subsequent evolution of the cluster is assumed to be dominated by dynamical interactions among cluster members, and this establishes the final properties of the binary and multiple systems. The characteristic scale of the fragmenting core is determined by the cloud initial conditions (such as temperature, angular momentum and mass), and we are able to relate the separation distributions of the final binary population to the properties of the star-forming core. Because the fragmentation scale immediately after the isothermal collapse is typically a factor of 3-10 too large, we conjecture that fragmentation into small clusters followed by dynamical evolution is required to account for the observed binary separation distributions. Differences in the environmental properties of the cores are expected to imprint differences on the characteristic dimensions of the binary systems they form. Recent observations of hierarchical systems, differences in binary characteristics among star forming regions and systematic variations in binary properties with primary mass can be interpreted in the context of this scenario.

Hot subdwarfs in (eclipsing) binaries with brown dwarf or low-mass main-sequence companions

NASA Astrophysics Data System (ADS)

Schaffenroth, Veronika; Geier, Stephan; Heber, Uli

2014-09-01

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 systems 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 systems 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 systems. 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 low-mass main-sequence companions and their spectral and photometric analysis to determine the fundamental parameters of both components.

VizieR Online Data Catalog: Solar neighborhood. XXXII. L and M dwarfs (Dieterich+, 2014)

NASA Astrophysics Data System (ADS)

Dieterich, S. B.; Henry, T. J.; Jao, W.-C.; Winters, J. G.; Hosey, A. D.; Riedel, A. R.; Subasavage, J. P.

2015-01-01

We obtained VRI photometry for all targets in our sample using the Cerro Tololo Inter-American Observatory (CTIO) 0.9m telescope for the brighter targets and the SOuthern Astrophysical Research (SOAR) Optical Imager camera on the SOAR 4.1m telescope for fainter targets. SOAR observations were conducted between 2009 September and 2010 December during six observing runs comprising NOAO programs 2009B-0425, 2010A-0185, and 2010B-0176. A total of 17 nights on SOAR were used for optical photometry. Table 1 shows the photometry in the photometric system used by the telescope with which the measurements were taken (Johnson-Kron-Cousins for the CTIO 0.9m telescope and Bessell for SOAR). Astrometric observations are based in part on observations obtained via the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI), at the Cerro Tololo 0.9m telescope. CTIOPI is a large and versatile astrometric monitoring program targeting diverse types of stellar and substellar objects in the solar neighborhood. Observations are taken using the CTIO 0.9m telescope and its sole instrument, a 2048*2048 Tektronix imaging CCD detector with a plate scale of 0.401''/pixel. (4 data files).

Race to the Top: Transiting Brown Dwarfs and Hot Jupiters

NASA Astrophysics Data System (ADS)

Beatty, Thomas G.

2015-12-01

There are currently twelve known transiting brown dwarfs, nine of which orbit single main-sequence stars. These systems give us one of the only ways in which we may directly measure the masses and radii brown dwarfs, which in turn provides strong constraints on theoretical models of brown dwarf interiors and atmospheres. In addition, the transiting brown dwarfs allow us to forge a link between our understanding of transiting hot Jupiters, and our understanding of the field brown dwarf population. Comparing the two gives us a unique avenue to explore the role and interaction of surface gravity and stellar irradiation in the atmospheres of sub-stellar objects. It also allows us to leverage the detailed spectroscopic information we have for field brown dwarfs to interpret the broadband colors of hot Jupiters. This provides us with insight into the L/T transition in brown dwarfs, and the atmospheric chemistry changes that occur in hot Jupiter atmospheres as they cool. I will discuss recent observational results, with a particular focus on the transiting brown dwarf KELT-1b, and suggest how more of these important systems may be discovered in the future.

An Evolving Trio of Hybrid Stars: C 111

NASA Technical Reports Server (NTRS)

Oliversen, Ronald (Technical Monitor); Dupree, Andrea K.

2004-01-01

Our goal is to understand the behavior of the outer atmosphere in this intermediate stage to create a comprehensive picture of atmospheric evolution. In the hybrid phase, the large-scale magnetic dynamo activity decays and hydrodynamic processes assume importance. Some hot plasma is still confined close to the star by magnetic loops, yet the confining field is breaking open, the atmosphere can escape through these open field lines, and the diffuse corona may be warm. There may well be a more extended and variable transition process. It remains for FUSE to identify the controlling parameters of the hybrid stars. It shows the positions of our 3 targets in the color-magnitude diagram where it is seen that they are at the extreme end of the hybrid region. Originally we had been awarded the hybrid star Iota Aur, but due to newly imposed pointing constraints of FUSE, that target was not accessible. And so we substituted Iota Dra, a giant of mass similar to our other targets but less evolved. In addition, Iota Dra was recently found to harbor a sub-stellar objects, possibly a planet, and so it could reveal the stellar environment of the planet. This substitution was accepted.

Young Stellar Objects observed by MOST

NASA Astrophysics Data System (ADS)

Siwak, Michal

2013-07-01

In the recent years the MOST satellite gathered dozens of high quality light curves of Young Stellar Objects (YSO). We present the most interesting results obtained from the data collected between 2009-2013.

Getting to know the nearest stars: Intermittent radio bursts from Ross 614

NASA Astrophysics Data System (ADS)

Winterhalter, Daniel; Knapp, Mary; Bastian, Tim

2017-04-01

Radio observations have been used as a search tool for exoplanets since before the confirmed discovery of the first extrasolar planet. To date, there have been no definitive detections of exoplanets in the radio regime. We are engaged in an ongoing blind radio survey of the nearest star systems for exoplanetary radio emission. The goal of this survey is to obtain meaningful upper limits on radio emission from (or modulated by) sub-stellar companions of the nearest stars. Nearby stars are strongly preferred because they suffer the least from the dilution of potential radio signals by distance. Targets are selected by distance and observability (both LOFAR and VLA) only. Other properties of target stars, such as stellar type, are not considered to avoid biasing the search. Five survey targets, Procyon, GJ 1111, GJ 725, Ross 614, and UGPSJ072227.51, have been observed with the VLA telescope L- and S-band receivers. P-band observations are ongoing. Of particular interest are, at this time, our observation of the Ross 614 System. Ross 614 is an M-dwarf binary system at a distance of about 13 Ly, with an orbital period of 16.6 years. The binary companions are classified as flare stars because strong radio emission has been detected from the location of the system in previous work. Analyses are in progress to determine if the intermittent burst are similar to solar-type burst, and/or if there is any evidence for emissions from sub-stellar companions.

IGRINS on the DCT

NASA Astrophysics Data System (ADS)

Prato, Lisa A.

2017-01-01

Through an agreement with the University of Texas at Austin and the Korea Astronomy and Space Science Institute, the Immersion Grating Infrared Spectrograph (IGRINS) saw first light on the Lowell Observatory 4.3 m Discovery Channel Telescope (DCT) telescope on September 8, 2016. IGRINS, originally commissioned at the McDonald Observatory 2.7 m telescope, provides a spectral resolution of 45,000 and a simultaneous spectral grasp of 1.45 to 2.45 microns, recording all of the H and K bands with no gaps in wavelength coverage on two H2RG detectors in a single exposure. The instrument design minimizes optical surfaces, optimizing throughput, and has no moving parts, key for stability. IGRINS on the DCT attains a signal to noise of 100 per resolution element in one hour of integration time on a K=12 magnitude source, currently making it the most sensitive high-resolution spectrograph in the world at H and K. Science programs in the fourth quarter, 2016, include such diverse topics as abundance measurements in M dwarfs and population II stars, studies of ices and atmospheres in outer solar system bodies, measurement of fundamental properties of pre-main sequence stars, calibrating young star evolution, defining the substellar boundary at the youngest ages, outflow characteristics in Wolf-Rayet stars, finding the first generation of exoplanets, gas dynamics in planetary nebulae, and structure of the ISM in molecular clouds. In this talk I will report on initial results from selected programs.

The Use of Play Expansions to Increase the Diversity and Complexity of Object Play in Young Children with Disabilities

ERIC Educational Resources Information Center

Frey, Jennifer R.; Kaiser, Ann P.

2011-01-01

The purpose of this study was to determine if an intervention consisting of contingently imitating play, modeling expansions of play actions, and describing play actions increased the diversity of object play in young children with disabilities. The multicomponent intervention was introduced in a multiple-probe design across three young children…

Narrative Writing Competence and Internal State Terms of Young Adults Clinically Diagnosed with Childhood Attention Deficit Hyperactivity Disorder

ERIC Educational Resources Information Center

Miranda, Ana; Baixauli, Inmaculada; Colomer, Carla

2013-01-01

Objective: The first objective of this study was to compare the written expression competence of young adults with attention deficit hyperactivity disorder (ADHD) with that of young adults without ADHD on three types of measures: indicators of the story's microstructure with regard to productivity and morphosyntax; indicators of the macrostructure…

The GAPS Programme with HARPS-N at TNG. XV. A substellar companion around a K giant star identified with quasi-simultaneous HARPS-N and GIANO measurements

NASA Astrophysics Data System (ADS)

González-Álvarez, E.; Affer, L.; Micela, G.; Maldonado, J.; Carleo, I.; Damasso, M.; D'Orazi, V.; Lanza, A. F.; Biazzo, K.; Poretti, E.; Gratton, R.; Sozzetti, A.; Desidera, S.; Sanna, N.; Harutyunyan, A.; Massi, F.; Oliva, E.; Claudi, R.; Cosentino, R.; Covino, E.; Maggio, A.; Masiero, S.; Molinari, E.; Pagano, I.; Piotto, G.; Smareglia, R.; Benatti, S.; Bonomo, A. S.; Borsa, F.; Esposito, M.; Giacobbe, P.; Malavolta, L.; Martinez-Fiorenzano, A.; Nascimbeni, V.; Pedani, M.; Rainer, M.; Scandariato, G.

2017-10-01

Context. Identification of planetary companions of giant stars is made difficult because of the astrophysical noise, that may produce radial velocity variations similar to those induced by a companion. On the other hand any stellar signal is wavelength dependent, while signals due to a companion are achromatic. Aims: Our goal is to determine the origin of the Doppler periodic variations observed in the thick disk K giant star TYC 4282-605-1 by HARPS-N at the Telescopio Nazionale Galileo (TNG) and verify if they can be due to the presence of a substellar companion. Methods: Several methods have been used to exclude the stellar origin of the observed signal including detailed analysis of activity indicators and bisector and the analysis of the photometric light curve. Finally we have conducted an observational campaign to monitor the near infrared (NIR) radial velocity with GIANO at the TNG in order to verify whether the NIR amplitude variations are comparable with those observed in the visible. Results: Both optical and NIR radial velocities show consistent variations with a period at 101 days and similar amplitude, pointing to the presence of a companion orbiting the target. The main orbital properties obtained for our giant star with a derived mass of M = 0.97 ± 0.03M⊙ are MPsini = 10.78 ± 0.12MJ; P = 101.54 ± 0.05 days; e = 0.28 ± 0.01 and a = 0.422 ± 0.009 AU. The chemical analysis shows a significant enrichment in the abundance of Na I, Mg I, Al I and Si I while the rest of analyzed elements are consistent with the solar value demonstrating that the chemical composition corresponds with an old K giant (age = 10.1 Gyr) belonging to local thick disk. Conclusions: We conclude that the substellar companion hypothesis for this K giant is the best explanation for the observed periodic radial velocity variation. This study also shows the high potential of multi-wavelength radial velocity observations for the validation of planet candidates. Based on observations collected at the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the frame of the programme Global Architecture of Planetary Systems (GAPS).

43 CFR 32.3 - Program purpose and objectives.

Code of Federal Regulations, 2014 CFR

2014-10-01

... ESTABLISHING YOUNG ADULT CONSERVATION CORPS (YACC) PROGRAM § 32.3 Program purpose and objectives. It is the purpose of the Young Adult Conservation Corps to provide employment and other benefits to youths of both...

43 CFR 32.3 - Program purpose and objectives.

Code of Federal Regulations, 2010 CFR

2010-10-01

... ESTABLISHING YOUNG ADULT CONSERVATION CORPS (YACC) PROGRAM § 32.3 Program purpose and objectives. It is the purpose of the Young Adult Conservation Corps to provide employment and other benefits to youths of both...

The IMF in extreme star-forming environments: Searching for variations vs. initial conditions

NASA Astrophysics Data System (ADS)

Andersen, Morten; Meyer, M. R.; Greissl, J.; Oppenheimer, B. D.; Kenworthy, M. A.; McCarthy, D. W.; Zinnecker, H.

Any predictive theory of star formation must explain observed variations (or lack thereof) in the initial mass function. Recent work suggests that we might expect quantitative variations in the IMF as a function of metallicity (Larson 2005) or magnetic field strength (Shu et al. 2004). We summarize results from several on-going studies attempting to constrain the ratio of high to low mass stars, as well as stars to sub- stellar objects, in a variety of different environments, all containing high mass stars.First, we examine the ratio of stars to sub-stellar objects in the nearby Mon R2 region utilizing NICMOS/HST data. We compare our results to the IMF by Kroupa (2002) and to the observed ratios for IC 348 and Orion. Second, we present preliminary results for the ratio of high to low mass stars in W51, the most luminous HII region in the galaxy. Based on ground-based multi-colour images of the cluster obtained with the MMT adaptive optics system, we derive a lower limit to the ratio of high-mass to low-mass stars and compare it to the ratios for nearby clusters. Finally, we present the derived IMF for the R136 region in the LMC where the metallicity is 1/4 solar using HST/NICMOS data. We find that the IMF is consistent with that characterizing the field (Chabrier 2003), as well as nearby star-forming regions, down to 1.0 M_⊙ outside 2 pc. Whereas the results for both Mon R2 and R136 are consistent with the nearby clusters, the ratio of high to low mass stars in W51 tentatively indicates a lack of low-mass objects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yun; Kouwenhoven, M. B. N.; Stamatellos, D.

The origin of very low-mass hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) at the low-mass end of the initial mass function is not yet fully understood. Gravitational fragmentation of circumstellar disks provides a possible mechanism for the formation of such low-mass objects. The kinematic and binary properties of very low-mass objects formed through disk fragmentation at early times (<10 Myr) were discussed in our previous paper. In this paper we extend the analysis by following the long-term evolution of disk-fragmented systems up to an age of 10 Gyr, covering the ages of the stellar and substellar populations inmore » the Galactic field. We find that the systems continue to decay, although the rates at which companions escape or collide with each other are substantially lower than during the first 10 Myr, and that dynamical evolution is limited beyond 1 Gyr. By t = 10 Gyr, about one third of the host stars are single, and more than half have only one companion left. Most of the other systems have two companions left that orbit their host star in widely separated orbits. A small fraction of companions have formed binaries that orbit the host star in a hierarchical triple configuration. The majority of such double-companion systems have internal orbits that are retrograde with respect to their orbits around their host stars. Our simulations allow a comparison between the predicted outcomes of disk fragmentation with the observed low-mass hydrogen-burning stars, BDs, and PMOs in the solar neighborhood. Imaging and radial velocity surveys for faint binary companions among nearby stars are necessary for verification or rejection of the formation mechanism proposed in this paper.« less

3-D Mind Maps: Placing Young Children in the Centre of Their Own Learning

ERIC Educational Resources Information Center

Howitt, Christine

2009-01-01

Three-dimensional mind maps are a highly effective tool for providing engaging, kinaesthetic and sensory experiences for young children, with real objects used to promote the sharing of knowledge and the creation of connections. The use of real objects allows children the opportunity to connect with those objects at a personal level, thus placing…

Involving a young person in the development of a digital resource in nurse education.

PubMed

Fenton, Gaynor

2014-01-01

Health policies across western societies have embedded the need for service user and carer perspectives in service design and delivery of educational programmes. There is a growing recognition of the need to include the perspectives of children and young people as service users in the design and delivery of child focused educational programmes. Digital storytelling provides a strategy for student nurses to gain insight into the lived experiences of children and young people. Engaging with these stories enables students to develop an understanding of a young persons' experience of healthcare. This paper outlines a project that developed a digital learning object based upon a young person's experience of cancer and student evaluations of the digital learning object as a teaching and learning strategy. Over 80% of students rated the digital learning object as interesting and were motivated to explore its content. In addition, the evaluation highlighted that listening to the young person's experiences of her treatment regimes was informative and assisted understanding of a patients' perspective of care delivery. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Solar Neighborhood. XXXII. The Hydrogen Burning Limit

NASA Astrophysics Data System (ADS)

Dieterich, Sergio B.; Henry, Todd J.; Jao, Wei-Chun; Winters, Jennifer G.; Hosey, Altonio D.; Riedel, Adric R.; Subasavage, John P.

2014-05-01

We construct a Hertzsprung-Russell diagram for the stellar/substellar boundary based on a sample of 63 objects ranging in spectral type from M6V to L4. We report newly observed VRI photometry for all 63 objects and new trigonometric parallaxes for 37 objects. The remaining 26 objects have trigonometric parallaxes from the literature. We combine our optical photometry and trigonometric parallaxes with 2MASS and WISE photometry and employ a novel spectral energy distribution fitting algorithm to determine effective temperatures, bolometric luminosities, and radii. Our uncertainties range from ~20 K to ~150 K in temperature, ~0.01 to ~0.06 in log (L/L ⊙) and ~3% to ~10% in radius. We check our methodology by comparing our calculated radii to radii directly measured via long baseline optical interferometry. We find evidence for the local minimum in the radius-temperature and radius-luminosity trends that signals the end of the stellar main sequence and the start of the brown dwarf sequence at T eff ~ 2075 K, log (L/L ⊙) ~ -3.9, and (R/R ⊙) ~ 0.086. The existence of this local minimum is predicted by evolutionary models, but at temperatures ~400 K cooler. The minimum radius happens near the locus of 2MASS J0523-1403, an L2.5 dwarf with V - K = 9.42. We make qualitative arguments as to why the effects of the recent revision in solar abundances accounts for the discrepancy between our findings and the evolutionary models. We also report new color-absolute magnitude relations for optical and infrared colors which are useful for estimating photometric distances. We study the optical variability of all 63 targets and find an overall variability fraction of 36^{+9}_{-7}% at a threshold of 15 mmag in the I band, which is in agreement with previous studies.

DISCOVERY OF A HIGHLY UNEQUAL-MASS BINARY T DWARF WITH KECK LASER GUIDE STAR ADAPTIVE OPTICS: A COEVALITY TEST OF SUBSTELLAR THEORETICAL MODELS AND EFFECTIVE TEMPERATURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Michael C.; Dupuy, Trent J.; Leggett, S. K., E-mail: mliu@ifa.hawaii.ed

Highly unequal-mass ratio binaries are rare among field brown dwarfs, with the mass ratio distribution of the known census described by q {sup (4.9{+-}0.7)}. However, such systems enable a unique test of the joint accuracy of evolutionary and atmospheric models, under the constraint of coevality for the individual components (the 'isochrone test'). We carry out this test using two of the most extreme field substellar binaries currently known, the T1 + T6 {epsilon} Ind Bab binary and a newly discovered 0.''14 T2.0 + T7.5 binary, 2MASS J12095613-1004008AB, identified with Keck laser guide star adaptive optics. The latter is the mostmore » extreme tight binary resolved to date (q {approx} 0.5). Based on the locations of the binary components on the Hertzsprung-Russell (H-R) diagram, current models successfully indicate that these two systems are coeval, with internal age differences of log(age) = -0.8 {+-} 1.3(-1.0{sup +1.2}{sub -1.3}) dex and 0.5{sup +0.4}{sub -0.3}(0.3{sup +0.3}{sub -0.4}) dex for 2MASS J1209-1004AB and {epsilon} Ind Bab, respectively, as inferred from the Lyon (Tucson) models. However, the total mass of {epsilon} Ind Bab derived from the H-R diagram ({approx} 80 M{sub Jup} using the Lyon models) is strongly discrepant with the reported dynamical mass. This problem, which is independent of the assumed age of the {epsilon} Ind Bab system, can be explained by a {approx} 50-100 K systematic error in the model atmosphere fitting, indicating slightly warmer temperatures for both components; bringing the mass determinations from the H-R diagram and the visual orbit into consistency leads to an inferred age of {approx} 6 Gyr for {epsilon} Ind Bab, older than previously assumed. Overall, the two T dwarf binaries studied here, along with recent results from T dwarfs in age and mass benchmark systems, yield evidence for small ({approx}100 K) errors in the evolutionary models and/or model atmospheres, but not significantly larger. Future parallax, resolved spectroscopy, and dynamical mass measurements for 2MASS J1209-1004AB will enable a more stringent application of the isochrone test. Finally, the binary nature of this object reduces its utility as the primary T3 near-IR spectral typing standard; we suggest SDSS J1206+2813 as a replacement.« less

FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filippazzo, Joseph C.; Rice, Emily L.; Faherty, Jacqueline

We combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 Myr) and 53 young (lower age estimate <500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (L{sub bol})more » and radius estimates from evolutionary models give semi-empirical effective temperatures (T{sub eff}) for the full range of young and field age late-M, L, and T dwarfs. We construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as T{sub eff}, surface gravity, and clouds on spectral morphology. We report bolometric corrections in J for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in Ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR–MIR reddening of low gravity L dwarfs and identify a systematically cooler T{sub eff} of up to 300 K from field age objects of the same spectral type and 400 K cooler from field age objects of the same M{sub H} magnitude.« less

The Moving Group Targets of the Seeds High-Contrast Imaging Survey of Exoplanets and Disks: Results and Observations from the First Three Years

NASA Technical Reports Server (NTRS)

Brandt, Timothy D.; Kuzuhara, Masayuki; McElwain, Michael W.; Schlieder, Joshua E.; Wisniewski, John P.; Turner, Edwin L.; Carson, J.; Matsuo, T.; Biller, B.; Bonnefoy, M.;

Lithium in Open Cluster Red Giants Hosting Substellar Companions

NASA Technical Reports Server (NTRS)

Carlberg, Joleen K.; Smith, Verne V.; Cunha, Katia; Carpenter, Kenneth G.

2016-01-01

We have measured stellar parameters, [Fe/H], lithium abundances, rotation, and (12)C/13C in a small sample of red giants (RGs) in three open clusters that are each home to a RG star that hosts a substellar companion (SSC) (NGC 2423 3, NGC 4349 127, and BD+12 1917 in M67). Our goal is to explore whether the presence of SSCs influences the Li content. Both (12)C/13C and stellar rotation are measured as additional tracers of stellar mixing. One of the companion hosts, NGC 2423?3, is found to be Li-rich with A(Li)(sub NLTE) = 1.56 dex, and this abundance is significantly higher than the A(Li) of the two comparison stars in NGC 2423. All three SSC hosts have the highest A(Li) and (12)C/13C when compared to the control RGs in their respective clusters; however, except for NGC 2423?3, at least one control star has similarly high abundances within the uncertainties. Higher A(Li) could suggest that the formation or presence of planets plays a role in the degree of internal mixing on or before the RG branch. However, a multitude of factors affect A(Li) during the RG phase, and when the abundances of our sample are compared with the abundances of RGs in other open clusters available in the literature, we find that they all fall well within a much larger distribution of A(Li) and (12)C/13C. Thus, even the high Li in NGC 2423 3 cannot be concretely tied to the presence of the SSC.

Lithium in Open Cluster Red Giants Hosting Substellar Companions

NASA Astrophysics Data System (ADS)

Carlberg, Joleen K.; Smith, Verne V.; Cunha, Katia; Carpenter, Kenneth G.

2016-02-01

We have measured stellar parameters, [Fe/H], lithium abundances, rotation, and 12C/13C in a small sample of red giants (RGs) in three open clusters that are each home to a RG star that hosts a substellar companion (SSC) (NGC 2423 3, NGC 4349 127, and BD+12 1917 in M67). Our goal is to explore whether the presence of SSCs influences the Li content. Both 12C/13C and stellar rotation are measured as additional tracers of stellar mixing. One of the companion hosts, NGC 2423 3, is found to be Li-rich with A(Li){}{{NLTE}} = 1.56 dex, and this abundance is significantly higher than the A(Li) of the two comparison stars in NGC 2423. All three SSC hosts have the highest A(Li) and 12C/13C when compared to the control RGs in their respective clusters; however, except for NGC 2423 3, at least one control star has similarly high abundances within the uncertainties. Higher A(Li) could suggest that the formation or presence of planets plays a role in the degree of internal mixing on or before the RG branch. However, a multitude of factors affect A(Li) during the RG phase, and when the abundances of our sample are compared with the abundances of RGs in other open clusters available in the literature, we find that they all fall well within a much larger distribution of A(Li) and 12C/13C. Thus, even the high Li in NGC 2423 3 cannot be concretely tied to the presence of the SSC.

The moving group targets of the seeds high-contrast imaging survey of exoplanets and disks: Results and observations from the first three years

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Timothy D.; Turner, Edwin L.; Janson, M.

2014-05-01

We present results from the first three years of observations of moving group (MG) targets in the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) high-contrast imaging survey of exoplanets and disks using the Subaru telescope. We achieve typical contrasts of ∼10{sup 5} at 1'' and ∼10{sup 6} beyond 2'' around 63 proposed members of nearby kinematic MGs. We review each of the kinematic associations to which our targets belong, concluding that five, β Pictoris (∼20 Myr), AB Doradus (∼100 Myr), Columba (∼30 Myr), Tucana-Horogium (∼30 Myr), and TW Hydrae (∼10 Myr), are sufficiently well-defined to constrain the agesmore » of individual targets. Somewhat less than half of our targets are high-probability members of one of these MGs. For all of our targets, we combine proposed MG membership with other age indicators where available, including Ca II HK emission, X-ray activity, and rotation period, to produce a posterior probability distribution of age. SEEDS observations discovered a substellar companion to one of our targets, κ And, a late B star. We do not detect any other substellar companions, but do find seven new close binary systems, of which one still needs to be confirmed. A detailed analysis of the statistics of this sample, and of the companion mass constraints given our age probability distributions and exoplanet cooling models, will be presented in a forthcoming paper.« less

Infants' Use of Category Knowledge and Object Attributes when Segregating Objects at 8.5 Months of Age

ERIC Educational Resources Information Center

Needham, Amy; Cantlon, Jessica F.; Ormsbee Holley, Susan M.

2006-01-01

The current research investigates infants' perception of a novel object from a category that is familiar to young infants: key rings. We ask whether experiences obtained outside the lab would allow young infants to parse the visible portions of a partly occluded key ring display into one single unit, presumably as a result of having categorized it…

Laboratory Synthesized Calcium Oxide and Calcium Hydroxide Grains: A Candidate to Explain the 6.8 Micron Band

NASA Technical Reports Server (NTRS)

Kimura, Yuki; Nuth, Joseph A., III

2005-01-01

We will demonstrate that CaO and Ca(OH)2 are excellent candidates to explain the 6.8 microns feature, which is one of the most obscure features in young stellar objects. We discuss the condensation of CaO grains and the potential formation of a Ca(OH)2 surface layer. The infrared spectra of these grains are compared with the spectra of fifteen young stellar objects. We note that CaO-rich grains are seen in all meteoritic CAIs (calcium-aluminum-rich inclusions) and the 6.8 micron feature has only been observed in young stellar objects. Therefore, we consider CaO grains to be a plausible candidate to explain the 6.8 microns feature and hypothesize that they are produced in the hot interiors of young stellar environments.

NEW YOUNG STAR CANDIDATES IN CG4 AND Sa101

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebull, L. M.; Laine, S.; Laher, R.

2011-07-15

The CG4 and Sa101 regions together cover a region of {approx}0.5 deg{sup 2} in the vicinity of a 'cometary globule' that is part of the Gum Nebula. There are seven previously identified young stars in this region; we have searched for new young stars using mid- and far-infrared data (3.6-70 {mu}m) from the Spitzer Space Telescope, combined with ground-based optical data and near-infrared data from the Two Micron All Sky Survey. We find infrared excesses in all six of the previously identified young stars in our maps and identify 16 more candidate young stars based on apparent infrared excesses. Mostmore » (73%) of the new young stars are Class II objects. There is a tighter grouping of young stars and young star candidates in the Sa101 region, in contrast to the CG4 region, where there are fewer young stars and young star candidates, and they are more dispersed. Few likely young objects are found in the 'fingers' of the dust being disturbed by the ionization front from the heart of the Gum Nebula.« less

Spectroscopic binaries in the Solar Twin Planet Search program: from substellar-mass to M dwarf companions

NASA Astrophysics Data System (ADS)

dos Santos, Leonardo A.; Meléndez, Jorge; Bedell, Megan; Bean, Jacob L.; Spina, Lorenzo; Alves-Brito, Alan; Dreizler, Stefan; Ramírez, Iván; Asplund, Martin

2017-12-01

Previous studies on the rotation of Sun-like stars revealed that the rotational rates of young stars converge towards a well-defined evolution that follows a power-law decay. It seems, however, that some binary stars do not obey this relation, often by displaying enhanced rotational rates and activity. In the Solar Twin Planet Search program, we observed several solar twin binaries, and found a multiplicity fraction of 42 per cent ± 6 per cent in the whole sample; moreover, at least three of these binaries (HIP 19911, HIP 67620 and HIP 103983) clearly exhibit the aforementioned anomalies. We investigated the configuration of the binaries in the program, and discovered new companions for HIP 6407, HIP 54582, HIP 62039 and HIP 30037, of which the latter is orbited by a 0.06 M⊙ brown dwarf in a 1 m long orbit. We report the orbital parameters of the systems with well-sampled orbits and, in addition, the lower limits of parameters for the companions that only display a curvature in their radial velocities. For the linear trend binaries, we report an estimate of the masses of their companions when their observed separation is available, and a minimum mass otherwise. We conclude that solar twin binaries with low-mass stellar companions at moderate orbital periods do not display signs of a distinct rotational evolution when compared to single stars. We confirm that the three peculiar stars are double-lined binaries, and that their companions are polluting their spectra, which explains the observed anomalies.

First Spectropolarimetric Measurement of a Brown Dwarf Magnetic Field in Molecular Bands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuzmychov, Oleksii; Berdyugina, Svetlana V.; Harrington, David M., E-mail: oleksii@leibniz-kis.de

We present the first measurements of the surface magnetic field of a late-M dwarf, LSR J1835+3259, with the help of the full-Stokes spectropolarimetry in the bands of diatomic molecules. Our measurements at different rotational phases of a dwarf yielded one 5 σ and two 3 σ magnetic field detections. The observational data have been obtained with the LRISp polarimeter at the Keck observatory on 2012 August 22 and 23. These data have been compared against synthetic full-Stokes spectra in the bands of the molecules CrH, FeH, and TiO, which have been calculated for a range of the stellar parameters andmore » magnetic field strengths. Making use of χ {sup 2}-minimization and maximum likelihood estimation, we determine the net magnetic field strength B (and not flux Bf ) of LSR J1835+3259 to ∼5 kG with the help of the Paschen–Back effect in the CrH lines. Our measurements at different rotational phases suggest that the dwarf’s surface might be covered with strong small-scale magnetic fields. In addition, recent findings of the dwarf’s hydrogen emission and the Stokes V signal from the lower chromosphere indicate that its surface magnetic field might be changing rapidly giving rise to flare activity, similar to young dMe dwarfs. We substantiate the substellar origin of LSR J1835+3259 by making use of our own data as well as the photometric data from the all-sky surveys 2MASS and WISE .« less

How Young Children and Chimpanzees ("Pan Troglodytes") Perceive Objects in a 2D Display: Putting an Assumption to the Test

ERIC Educational Resources Information Center

Leighty, Katherine A.; Menzel, Charles R.; Fragaszy, Dorothy M.

2008-01-01

Object recognition research is typically conducted using 2D stimuli in lieu of 3D objects. This study investigated the amount and complexity of knowledge gained from 2D stimuli in adult chimpanzees ("Pan troglodytes") and young children (aged 3 and 4 years) using a titrated series of cross-dimensional search tasks. Results indicate that 3-year-old…

Story Book Science

ERIC Educational Resources Information Center

Enfield, Mark; Mathew, Eliza

2012-01-01

Young children love stories, and teachers love to read stories. Young children also love to explore the motion of objects--they watch tossed balls, observe objects rolling down ramps, and are mesmerized by spinning tops. Yet it can be challenging to integrate these two loves, stories and exploring motion, in one lesson. Furthermore, while children…

Learning Activities for the Young Handicapped Child.

ERIC Educational Resources Information Center

Bailey, Don; And Others

Presented is a collection of learning activities for the young handicapped child covering 295 individual learning objectives in six areas of development: gross motor skills, fine motor skills, social skills, self help skills, cognitive skills, and language skills. Provided for each learning activity are the teaching objective, teaching procedures,…

A circumstellar disk associated with a massive protostellar object.

PubMed

Jiang, Zhibo; Tamura, Motohide; Fukagawa, Misato; Hough, Jim; Lucas, Phil; Suto, Hiroshi; Ishii, Miki; Yang, Ji

2005-09-01

The formation process for stars with masses several times that of the Sun is still unclear. The two main theories are mergers of several low-mass young stellar objects, which requires a high stellar density, or mass accretion from circumstellar disks in the same way as low-mass stars are formed, accompanied by outflows during the process of gravitational infall. Although a number of disks have been discovered around low- and intermediate-mass young stellar objects, the presence of disks around massive young stellar objects is still uncertain and the mass of the disk system detected around one such object, M17, is disputed. Here we report near-infrared imaging polarimetry that reveals an outflow/disk system around the Becklin-Neugebauer protostellar object, which has a mass of at least seven solar masses (M(o)). This strongly supports the theory that stars with masses of at least 7M(o) form in the same way as lower mass stars.

Self-initiated object-location memory in young and older adults.

PubMed

Berger-Mandelbaum, Anat; Magen, Hagit

2017-11-20

The present study explored self-initiated object-location memory in ecological contexts, as aspect of memory that is largely absent from the research literature. Young and older adults memorized objects-location associations they selected themselves or object-location associations provided to them, and elaborated on the strategy they used when selecting the locations themselves. Retrieval took place 30 min and 1 month after encoding. The results showed an age-related decline in self-initiated and provided object-location memory. Older adults benefited from self-initiation more than young adults when tested after 30 min, while the benefit was equal when tested after 1 month. Furthermore, elaboration enhanced memory only in older adults, and only after 30 min. Both age groups used deep encoding strategies on the majority of the trials, but their percentage was lower in older adults. Overall, the study demonstrated the processes involved in self-initiated object-location memory, which is an essential part of everyday functioning.

WISEP J060738.65+242953.4: A NEARBY POLE-ON L8 BROWN DWARF WITH RADIO EMISSION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gizis, John E.; Paudel, Rishi; Williams, Peter K. G.

2016-11-01

We present a simultaneous, multi-wavelength campaign targeting the nearby (7.2 pc) L8/L9 (optical/near-infrared) dwarf WISEP J060738.65+242953.4 in the mid-infrared, radio, and optical. Spitzer Space Telescope observations show no variability at the 0.2% level over 10 hr each in the 3.6 and 4.5 μ m bands. Kepler K2 monitoring over 36 days in Campaign 0 rules out stable periodic signals in the optical with amplitudes greater than 1.5% and periods between 1.5 hr and 2 days. Non-simultaneous Gemini optical spectroscopy detects lithium, constraining this L dwarf to be less than ∼2 Gyr old, but no Balmer emission is observed. The lowmore » measured projected rotation velocity ( v sin i < 6 km s{sup −1}) and lack of variability are very unusual compared to other brown dwarfs, and we argue that this substellar object is likely viewed pole-on. We detect quiescent (non-bursting) radio emission with the Very Large Array. Among radio-detected L and T dwarfs, it has the lowest observed L{sub ν} and the lowest v  sin  i . We discuss the implications of a pole-on detection for various proposed radio emission scenarios.« less

OV Bootis: Forty Nights Of World-Wide Photometry

NASA Astrophysics Data System (ADS)

Patterson, Joseph; de Miguel, Enrique; Barret, Douglas; Brincat, Stephen; Boardman, James, Jr.; Buczynski, Denis; Campbell, Tut; Cejudo, David; Cook, Lew; Cook, Michael J.; Collins, Donald; Cooney, Walt; Dubois, Franky; Dvorak, Shawn; Halpern, Jules P.; Kroes, Anthony J.; Lemay, Damien; Licchelli, Domenico; Mankel, Dylan; Marshall, Matt; Novak, Rudolf; Oksanen, Arto; Roberts, George; Seargeant, Jim; Sears, Huei; Silcox, Austin; Slauson, Douglas; Stone, Geoff; Thorstensen, J. R.; Ulowetz, Joe; Vanmunster, Tonny; Wallgren, John; Wood, Matt

2017-06-01

Among the 1000 known cataclysmic variables, only one appears to belong to the "Galactic halo" - the Population II stars. We report round-the-world photometry of this star (OV Boo) during March-April 2017, when it staged its first certified dwarf-nova outburst. The star is remarkable for its short binary period (66 minutes), high proper motion, metal-poor composition, substellar secondary, sharp white-dwarf eclipses, and nonradial pulsations. Something for everybody...... and it even had the good manners to erupt in northern springtime, when it transits near local midnight. Move over, SS Cyg and WZ Sge; there's a new celebrity in town!

Precipitating Condensation Clouds in Substellar Atmospheres

NASA Technical Reports Server (NTRS)

Ackerman, Andrew S.; Marley, Mark S.; Gore, Warren J. (Technical Monitor)

2000-01-01

We present a method to calculate vertical profiles of particle size distributions in condensation clouds of giant planets and brown dwarfs. The method assumes a balance between turbulent diffusion and precipitation in horizontally uniform cloud decks. Calculations for the Jovian ammonia cloud are compared with previous methods. An adjustable parameter describing the efficiency of precipitation allows the new model to span the range of predictions from previous models. Calculations for the Jovian ammonia cloud are found to be consistent with observational constraints. Example calculations are provided for water, silicate, and iron clouds on brown dwarfs and on a cool extrasolar giant planet.

Accuracy of self-reported sleep parameters compared with actigraphy in young people with mental ill-health.

PubMed

Biddle, Daniel J; Robillard, Rébecca; Hermens, Daniel F; Hickie, Ian B; Glozier, Nicholas

2015-09-01

Validation of self-report assessment of habitual sleep duration and onset time in young people with mental ill-health. Validation sample. Specialized early intervention centers for young people in Sydney, Australia. One hundred and forty-six young people with mental ill-health. N/A. Self-reported habitual sleep duration and onset time were compared against at least 7 days of actigraphy monitoring. Average bias in and calibration of subjective measures were assessed, along with correlation of subjective and objective measures. Differences by age, sex, mental-disorder type, and reported insomnia were also explored. On average, subjective estimates of sleep were unbiased. Overall, each additional hour of objective habitual sleep duration predicted 41 minutes more subjective habitual sleep duration, and each hour later objective habitual sleep onset occurred predicted a 43-minute later subjective habitual sleep onset. There were subgroup differences: subjective habitual sleep duration in self-reported insomnia was shorter than objective duration by 30 minutes (SD = 119), on average. Calibration of habitual sleep duration was worse for those with mood disorders than with other primary diagnoses (t = -2.39, P = .018). Correlation between subjective and objective measures was strong for sleep onset time (Á = .667, P < .001) and moderate for sleep duration (r = .332, P < .001). For the mood disorder group, subjective and objective sleep durations were uncorrelated. Self-reports seem valid for large-scale studies of habitual sleep duration and onset in help-seeking young people, but assessment of habitual sleep duration requires objective measures where individual accuracy is important. Copyright © 2015 National Sleep Foundation. Published by Elsevier Inc. All rights reserved.

CHANDRA CHARACTERIZATION OF X-RAY EMISSION IN THE YOUNG F-STAR BINARY SYSTEM HD 113766

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisse, C. M.; Christian, D. J.; Wolk, S. J.

Using Chandra , we have obtained imaging X-ray spectroscopy of the 10–16 Myr old F-star binary HD 113766. We individually resolve the 1.″4 separation binary components for the first time in the X-ray and find a total 0.3–2.0 keV luminosity of 2.2 × 10{sup 29} erg s{sup −1}, consistent with previous RASS estimates. We find emission from the easternmost, infrared-bright, dusty member HD 113766A to be only ∼10% that of the western, infrared-faint member HD 113766B. There is no evidence for a 3rd late-type stellar or substellar member of HD 113766 with L {sub x} > 6 × 10{sup 25} erg s{sup −1} within 2′ ofmore » the binary pair. The ratio of the two stars’ X-ray luminosity is consistent with their assignments as F2V and F6V by Pecaut et al. The emission is soft for both stars, kT {sub Apec} = 0.30–0.50 keV, suggesting X-rays produced by stellar rotation and/or convection in young dynamos, but not accretion or outflow shocks, which we rule out. A possible 2.8 ± 0.15 (2 σ ) hr modulation in the HD 113766B X-ray emission is seen, but at very low confidence and of unknown provenance. Stellar wind drag models corresponding to L {sub x} ∼ 2 × 10{sup 29} erg s{sup −1} argue for a 1 mm dust particle lifetime around HD 113766B of only ∼90,0000 years, suggesting that dust around HD 113766B is quickly removed, whereas 1 mm sized dust around HD 113766A can survive for >1.5 × 10{sup 6} years. At 10{sup 28}–10{sup 29} erg s{sup −1} X-ray luminosity, astrobiologically important effects, like dust warming and X-ray photolytic organic synthesis, are likely for any circumstellar material in the HD 113766 systems.« less

On Mature Reflection: "Strange Objects" and the Cultivation of Reflective Reading.

ERIC Educational Resources Information Center

Heyde, Emma

2000-01-01

Examines Gary Crew's novel written for a young adult audience, called "Strange Objects," a story containing verifiable historical fact interwoven with elements of fiction and the supernatural. Shows how the numerous genres and viewpoints in the book challenge and contradict one another, forcing young readers to perform resistant readings…

Earlier and greater hand pre-shaping in the elderly: a study based on kinematic analysis of reaching movements to grasp objects.

PubMed

Tamaru, Yoshiki; Naito, Yasuo; Nishikawa, Takashi

2017-11-01

Elderly people are less able to manipulate objects skilfully than young adults. Although previous studies have examined age-related deterioration of hand movements with a focus on the phase after grasping objects, the changes in the reaching phase have not been studied thus far. We aimed to examine whether changes in hand shape patterns during the reaching phase of grasping movements differ between young adults and the elderly. Ten healthy elderly adults and 10 healthy young adults were examined using the Simple Test for Evaluating Hand Functions and kinetic analysis of hand pre-shaping reach-to-grasp tasks. The results were then compared between the two groups. For kinetic analysis, we measured the time of peak tangential velocity of the wrist and the inter-fingertip distance (the distance between the tips of the thumb and index finger) at different time points. The results showed that the elderly group's performance on the Simple Test for Evaluating Hand Functions was significantly lower than that of the young adult group, irrespective of whether the dominant or non-dominant hand was used, indicating deterioration of hand movement in the elderly. The peak tangential velocity of the wrist in either hand appeared significantly earlier in the elderly group than in the young adult group. The elderly group also showed larger inter-fingertip distances with arch-like fingertip trajectories compared to the young adult group for all object sizes. To perform accurate prehension, elderly people have an earlier peak tangential velocity point than young adults. This allows for a longer adjustment time for reaching and grasping movements and for reducing errors in object prehension by opening the hand and fingers wider. Elderly individuals gradually modify their strategy based on previous successes and failures during daily living to compensate for their decline in dexterity and operational capabilities. © 2017 Japanese Psychogeriatric Society.

Young Adults' Perceptions of Calcium Intake and Health: A Qualitative Study

ERIC Educational Resources Information Center

Marcinow, Michelle L.; Randall Simpson, Janis A.; Whiting, Susan J.; Jung, Mary E.; Buchholz, Andrea C.

2017-01-01

Many young Canadian adults are not meeting dietary calcium recommendations. This is concerning as adequate calcium is important throughout young adulthood to maximize peak bone mass for osteoporosis prevention. There are limited studies that have explored young adults' perceptions toward calcium and health. Our objectives were to determine young…

A critical reassessment of the fundamental properties of GJ 504: chemical composition and age

NASA Astrophysics Data System (ADS)

D'Orazi, V.; Desidera, S.; Gratton, R. G.; Lanza, A. F.; Messina, S.; Andrievsky, S. M.; Korotin, S.; Benatti, S.; Bonnefoy, M.; Covino, E.; Janson, M.

2017-02-01

Context. The recent development of brand new observational techniques and theoretical models have greatly advanced the exoplanet research field. Despite significant achievements, which have allowed the detection of thousands extrasolar systems, a comprehensive understanding of planetary formation and evolution mechanisms is still desired. One relevant limitation is given by the accuracy in the measurements of planet-host star ages. The star GJ 504 has been found to host a substellar companion whose nature is strongly debated. There has been a recent difference of opinion in the literature owing to the uncertainty on the age of the system: a young age of 160 Myr would imply a giant planet as a companion, but a recent revision pointing to a solar age ( 4 Gyr) instead suggests a brown dwarf. Aims: With the aim of shedding light on this debated topic, we have carried out a high-resolution spectroscopic study of GJ 504 to derive stellar parameters, metallicity, and abundances of both light and heavy elements, providing a full chemical characterisation. The main objective is to infer clues on the evolutionary stage (hence the age) of this system. Methods: We performed a strictly differential (line-by-line) analysis of GJ 504 with respect to two reference stars, that is the planet-host dwarf ι Hor and the subgiant HIP 84827. The former is crucial in this context because its stellar parameters (hence the evolutionary stage) is well constrained from asteroseismic observations. Regardless of the zero point offsets, our differential approach allows us to put tight constraints on the age of GJ 504 with respect to ι Hor, thereby minimising the internal uncertainties. Results: We found that the surface gravity of GJ 504 is 0.2 ± 0.07 dex lower than that of the main-sequence star ι Hor, suggesting a past turn-off evolution for our target. The isochrone comparison provides us with an age range between 1.8 and 3.5 Gyr, with a most probable age of ≈2.5 Gyr. Thus, our findings support an old age for the system; further evidence comes from the barium abundance, which is compatible with a solar pattern and not enhanced as observed in young stars. Conclusions: We envisaged a possible engulfment scenario to reconcile all the age indicators (spectroscopy, isochrones, rotation, and activity); this engulfment could have occurred very recently and could be responsible for the enhanced levels of rotation and chromospheric activity, as previously suggested. We tested this hypothesis, exploiting a tidal evolution code and finding that the engulfment of a hot Jupiter, with mass not larger than ≈3 Mj and initially located at ≈0.03 AU, seems to be a very likely scenario. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 072.A-9006(A) and 083.A-9003(A).

Line Bisector Variations in Stars with Extrasolar Planets

NASA Astrophysics Data System (ADS)

Povich, M. S.; Giampapa, M. S.; Valenti, J. A.; Tilleman, T.

1999-12-01

We present the results from a high-resolution, synoptic spectroscopic program of observation of ten F- and G-type stars, seven of which exhibit periodic radial velocity variations attributed to the presence of one or more substellar companions. The observations were obtained from 1998 March to 1999 February using the 1.52-m NSO McMath-Pierce Solar Telescope Facility on Kitt Peak in conjunction with the solar-stellar spectrograph. The spectra were acquired with a resolving power of approximately 1.2 x 105. The line bisector was then derived from unblended photospheric features. In particular, we define the velocity displacement of the spectral line bisector and determine the bisector amplitude for the Fe I absorption line at 625.26 nm in order to search for variations in the line asymmetry over time. Such variations could mimic Doppler shifts in observations with lower spectral resolution. Examination of the bisector velocity displacement over the time span of our observations reveals no substantial difference between stars with planetary companions and those without reported companions. We find no correlation between the bisector variations and the orbital phase of a substellar companion in any of our target stars. Simulations of a periodic signal with noise levels based on our measurement errors suggest that we can exclude bisector variations with amplitudes greater than about 20 m s-1. These results support the conclusion that extrasolar planets best explain the observed periodic variations in radial velocity. This work was supported by a NASA grant to the NOAO under the auspices of the Origins of Solar Systems Program. MP gratefully acknowledges support from the NSF-sponsored Research Experience for Undergraduates (REU) program at the NOAO. The NOAO is operated by AURA, Inc., under a cooperative agreement with the NSF.

Individual Dynamical Masses of Ultracool Dwarfs

NASA Astrophysics Data System (ADS)

Dupuy, Trent J.; Liu, Michael C.

2017-08-01

We present the full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7-T5. Joint analysis of resolved imaging from Keck Observatory and Hubble Space Telescope and unresolved astrometry from CFHT/WIRCam yields parallactic distances for all systems, robust orbit determinations for 23 systems, and photocenter orbits for 19 systems. As a result, we measure 38 precise individual masses spanning 30-115 {M}{Jup}. We determine a model-independent substellar boundary that is ≈70 {M}{Jup} in mass (≈L4 in spectral type), and we validate Baraffe et al. evolutionary model predictions for the lithium-depletion boundary (60 {M}{Jup} at field ages). Assuming each binary is coeval, we test models of the substellar mass-luminosity relation and find that in the L/T transition, only the Saumon & Marley “hybrid” models accounting for cloud clearing match our data. We derive a precise, mass-calibrated spectral type-effective temperature relation covering 1100-2800 K. Our masses enable a novel direct determination of the age distribution of field brown dwarfs spanning L4-T5 and 30-70 {M}{Jup}. We determine a median age of 1.3 Gyr, and our population synthesis modeling indicates our sample is consistent with a constant star formation history modulated by dynamical heating in the Galactic disk. We discover two triple-brown-dwarf systems, the first with directly measured masses and eccentricities. We examine the eccentricity distribution, carefully considering biases and completeness, and find that low-eccentricity orbits are significantly more common among ultracool binaries than solar-type binaries, possibly indicating the early influence of long-lived dissipative gas disks. Overall, this work represents a major advance in the empirical view of very low-mass stars and brown dwarfs.

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

NASA Astrophysics Data System (ADS)

Nilsson, R.; Veicht, A.; Giorla Godfrey, P. A.; Rice, E. L.; Aguilar, J.; Pueyo, L.; Roberts, L. C., Jr.; Oppenheimer, R.; Brenner, D.; Luszcz-Cook, S. H.; Bacchus, E.; Beichman, C.; Burruss, R.; Cady, E.; Dekany, R.; Fergus, R.; Hillenbrand, L.; Hinkley, S.; King, D.; Lockhart, T.; Parry, I. R.; Sivaramakrishnan, A.; Soummer, R.; Vasisht, G.; Zhai, C.; Zimmerman, N. T.

2017-03-01

The nearby Sun-like star GJ 758 hosts a cold substellar companion, GJ 758 B, at a projected separation of ≲30 au, previously detected in high-contrast multi-band photometric observations. In order to better constrain the companion’s physical characteristics, we acquired the first low-resolution (R ˜ 50) near-infrared spectrum of it using the high-contrast hyperspectral imaging instrument Project 1640 on Palomar Observatory’s 5 m Hale telescope. We obtained simultaneous images in 32 wavelength channels covering the Y, J, and H bands (˜952-1770 nm), and used data processing techniques based on principal component analysis to efficiently subtract chromatic background speckle-noise. GJ 758 B was detected in four epochs during 2013 and 2014. Basic astrometric measurements confirm its apparent northwest trajectory relative to the primary star, with no clear signs of orbital curvature. Spectra of SpeX/IRTF observed T dwarfs were compared to the combined spectrum of GJ 758 B, with χ 2 minimization suggesting a best fit for spectral type T7.0 ± 1.0, but with a shallow minimum over T5-T8. Fitting of synthetic spectra from the BT-Settl13 model atmospheres gives an effective temperature T eff = 741 ± 25 K and surface gravity {log}g=4.3+/- 0.5 dex (cgs). Our derived best-fit spectral type and effective temperature from modeling of the low-resolution spectrum suggest a slightly earlier and hotter companion than previous findings from photometric data, but do not rule out current results, and confirm GJ 758 B as one of the coolest sub-stellar companions to a Sun-like star to date.

Response to Taguchi and Noma on "relationship between directionality and orientation in drawings by young children and adults.

PubMed

Karev, George B

2006-02-01

When assessing the relationship between direction and orientation in drawings by young children and adults, Taguchi and Noma used a fish-drawing task. However, the fish is not convenient enough as an object for such a task so it is highly preferable to use, instead of a single object, a set of several objects to assess directionality quantitatively. These authors' conclusions do not acknowledge alternative explanations.

Spectral Characteristics of Young Stars Associated with the Sh2-296 Nebula

NASA Astrophysics Data System (ADS)

Fernandes, Beatriz; Gregorio-Hetem, Jane

Aiming to contribute to the understanding of star formation and evolution in the Canis Major (CMa R1) Molecular Clouds Complex, we analyze the spectral characteristics of a population of young stars associated with the arc-shaped nebula Sh2-296. Our XMM/Newton observations detected 109 X-ray sources in the region and optical spectroscopy was performed with Gemini telescope for 85 optical counterparts. We identified and characterized 51 objects that present features typically found in young objects, such as Hα emission and strong absorption on the Li I line.

The Complexity of Trauma Response: A 4-Year Follow-up of Adolescent Cambodian Refugees

ERIC Educational Resources Information Center

Rousseau, Cecile; Drapeau, Aline; Rahimi, Sadeq

2003-01-01

Objective: The objective of this study was to document the psychosocial adjustment of young refugees during their adolescence and its association with the war-related trauma experienced by their family before migration. Method: Data were collected on 57 young Khmer resettled in Montreal and followed from early to late adolescence. The associations…

Young Children's Understanding of Violations of Property Rights

ERIC Educational Resources Information Center

Rossano, Federico; Rakoczy, Hannes; Tomasello, Michael

2011-01-01

The present work investigated young children's normative understanding of property rights using a novel methodology. Two- and 3-year-old children participated in situations in which an actor (1) took possession of an object for himself, and (2) attempted to throw it away. What varied was who owned the object: the actor himself, the child subject,…

Prevalence, Patterns, and Predictors of Sleep Problems and Daytime Sleepiness in Young Adolescents with Attention-Deficit/Hyperactivity Disorder

ERIC Educational Resources Information Center

Langberg, Joshua M.; Molitor, Stephen J.; Oddo, Lauren E.; Eadeh, Hana-May; Dvorsky, Melissa R.; Becker, Stephen P.

2017-01-01

Objective: The primary objective of this study was to evaluate the prevalence of multiple types of sleep problems in young adolescents with ADHD. Method: 262 adolescents comprehensively diagnosed with ADHD and their caregivers completed well-validated measures of sleep problems and daytime sleepiness. Participants also completed measures related…

Food Safety Knowledge and Behaviours of Children (5-7 Years)

ERIC Educational Resources Information Center

Eves, Anita; Bielby, Gill; Egan, Bernadette; Lumbers, Margaret; Raats, Monique; Adams, Martin

2010-01-01

Objective: The objective of this study was to determine knowledge of food hygiene amongst young children (5-7 years), and facilitators and barriers to application of knowledge. Few studies exist that explore the knowledge and attitudes of young children towards food hygiene. This is an important age group, as it is a time when attitudes and…

A survey for variable young stars with small telescopes: First results from HOYS-CAPS

NASA Astrophysics Data System (ADS)

Froebrich, D.; Campbell-White, J.; Scholz, A.; Eislöffel, J.; Zegmott, T.; Billington, S. J.; Donohoe, J.; Makin, S. V.; Hibbert, R.; Newport, R. J.; Pickard, R.; Quinn, N.; Rodda, T.; Piehler, G.; Shelley, M.; Parkinson, S.; Wiersema, K.; Walton, I.

2018-05-01

Variability in Young Stellar Objects (YSOs) is one of their primary characteristics. Long-term, multi-filter, high-cadence monitoring of large YSO samples is the key to understand the partly unusual light-curves that many of these objects show. Here we introduce and present the first results of the HOYS-CAPScitizen science project which aims to perform such monitoring for nearby (d < 1 kpc) and young (age < 10 Myr) clusters and star forming regions, visible from the northern hemisphere, with small telescopes. We have identified and characterised 466 variable (413 confirmed young) stars in 8 young, nearby clusters. All sources vary by at least 0.2 mag in V, have been observed at least 15 times in V, R and I in the same night over a period of about 2 yrs and have a Stetson index of larger than 1. This is one of the largest samples of variable YSOs observed over such a time-span and cadence in multiple filters. About two thirds of our sample are classical T-Tauri stars, while the rest are objects with depleted or transition disks. Objects characterised as bursters show by far the highest variability. Dippers and objects whose variability is dominated by occultations from normal interstellar dust or dust with larger grains (or opaque material) have smaller amplitudes. We have established a hierarchical clustering algorithm based on the light-curve properties which allows the identification of the YSOs with the most unusual behaviour, and to group sources with similar properties. We discuss in detail the light-curves of the unusual objects V2492 Cyg, V350 Cep and 2MASS J21383981+5708470.

A parsec-scale optical jet from a massive young star in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

McLeod, Anna F.; Reiter, Megan; Kuiper, Rolf; Klaassen, Pamela D.; Evans, Christopher J.

2018-02-01

Highly collimated parsec-scale jets, which are generally linked to the presence of an accretion disk, are commonly observed in low-mass young stellar objects. In the past two decades, a few of these jets have been directly (or indirectly) observed from higher-mass (larger than eight solar masses) young stellar objects, adding to the growing evidence that disk-mediated accretion also occurs in high-mass stars, the formation mechanism of which is still poorly understood. Of the observed jets from massive young stars, none is in the optical regime (massive young stars are typically highly obscured by their natal material), and none is found outside of the Milky Way. Here we report observations of HH 1177, an optical ionized jet that originates from a massive young stellar object located in the Large Magellanic Cloud. The jet is highly collimated over its entire measured length of at least ten parsecs and has a bipolar geometry. The presence of a jet indicates ongoing, disk-mediated accretion and, together with the high degree of collimation, implies that this system is probably formed through a scaled-up version of the formation mechanism of low-mass stars. We conclude that the physics that govern jet launching and collimation is independent of stellar mass.

A parsec-scale optical jet from a massive young star in the Large Magellanic Cloud.

PubMed

McLeod, Anna F; Reiter, Megan; Kuiper, Rolf; Klaassen, Pamela D; Evans, Christopher J

2018-02-15

Highly collimated parsec-scale jets, which are generally linked to the presence of an accretion disk, are commonly observed in low-mass young stellar objects. In the past two decades, a few of these jets have been directly (or indirectly) observed from higher-mass (larger than eight solar masses) young stellar objects, adding to the growing evidence that disk-mediated accretion also occurs in high-mass stars, the formation mechanism of which is still poorly understood. Of the observed jets from massive young stars, none is in the optical regime (massive young stars are typically highly obscured by their natal material), and none is found outside of the Milky Way. Here we report observations of HH 1177, an optical ionized jet that originates from a massive young stellar object located in the Large Magellanic Cloud. The jet is highly collimated over its entire measured length of at least ten parsecs and has a bipolar geometry. The presence of a jet indicates ongoing, disk-mediated accretion and, together with the high degree of collimation, implies that this system is probably formed through a scaled-up version of the formation mechanism of low-mass stars. We conclude that the physics that govern jet launching and collimation is independent of stellar mass.

Barriers to Positive Mental Health in a Young Offenders Institution: A Qualitative Study

ERIC Educational Resources Information Center

Woodall, James

2007-01-01

Objective: To explore the barriers to positive mental health in a group of young offenders. Design: A qualitative approach was used to provide insight into the ways in which mental health for young offenders is experienced and managed. Setting: A Young Offenders Institute (YOI) accommodating males aged between 18 and 21 years. Method: Participants…

Age effect in generating mental images of buildings but not common objects.

PubMed

Piccardi, L; Nori, R; Palermo, L; Guariglia, C; Giusberti, F

2015-08-18

Imagining a familiar environment is different from imagining an environmental map and clinical evidence demonstrated the existence of double dissociations in brain-damaged patients due to the contents of mental images. Here, we assessed a large sample of young and old participants by considering their ability to generate different kinds of mental images, namely, buildings or common objects. As buildings are environmental stimuli that have an important role in human navigation, we expected that elderly participants would have greater difficulty in generating images of buildings than common objects. We found that young and older participants differed in generating both buildings and common objects. For young participants there were no differences between buildings and common objects, but older participants found easier to generate common objects than buildings. Buildings are a special type of visual stimuli because in urban environments they are commonly used as landmarks for navigational purposes. Considering that topographical orientation is one of the abilities mostly affected in normal and pathological aging, the present data throw some light on the impaired processes underlying human navigation. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Weather and Rotation on Young Brown Dwarfs

NASA Astrophysics Data System (ADS)

Vos, Johanna; Biller, Beth; Allers, Katelyn; Manjavacas, Elena; Liu, Michael; Best, William; Metchev, Stanimir; Buenzli, Esther; Bonavita, Mariangela; Eriksson, Simon; Dupuy, Trent; Kopytova, Taisiya; Brandner, Wolfgang; Henning, Thomas; Bonnefoy, Mickael; Crossfield, Ian; Schlieder, Joshua; Homeier, Derek; Janson, Markus; Radigan, Jacqueline

2018-05-01

As part of a large, ground-based survey for weather patterns on exoplanet analogues, we have detected J-band variability in 5 young exoplanet analogues. We have already carried out followup Spitzer monitoring of two objects and here we propose Spitzer 3.6um and 4.5um monitoring of three early-mid-L detections in our survey. The proposed observations will enable us to assess the role of gravity in the variability properties of these young objects by providing a full measure of mid-IR amplitude across the full L spectral sequence for low-gravity objects. The proposed observations will also allow us to measure the rotational periods of our three targets. This will provide vital information on the angular momentum of young brown dwarfs, while enabling us to correct for geometric effects when considering the variability properties of our targets. This study will act as a necessary pathfinder for future variability studies of free-floating and companion exoplanets with JWST.

A New Functional Health Literacy Scale for Japanese Young Adults Based on Item Response Theory.

PubMed

Tsubakita, Takashi; Kawazoe, Nobuo; Kasano, Eri

2017-03-01

Health literacy predicts health outcomes. Despite concerns surrounding the health of Japanese young adults, to date there has been no objective assessment of health literacy in this population. This study aimed to develop a Functional Health Literacy Scale for Young Adults (funHLS-YA) based on item response theory. Each item in the scale requires participants to choose the most relevant term from 3 choices in relation to a target item, thus assessing objective rather than perceived health literacy. The 20-item scale was administered to 1816 university students and 1751 responded. Cronbach's α coefficient was .73. Difficulty and discrimination parameters of each item were estimated, resulting in the exclusion of 1 item. Some items showed different difficulty parameters for male and female participants, reflecting that some aspects of health literacy may differ by gender. The current 19-item version of funHLS-YA can reliably assess the objective health literacy of Japanese young adults.

Generalization of Learning from Picture Books to Novel Test Conditions by 18- and 24-Month-Old Children

ERIC Educational Resources Information Center

Simcock, Gabrielle; Dooley, Megan

2007-01-01

Researchers know little about whether very young children can recognize objects originally introduced to them in a picture book when they encounter similar looking objects in various real-world contexts. The present studies used an imitation procedure to explore young children's ability to generalize a novel action sequence from a picture book to…

The Assessment of Elaborated Role-Play in Young Children: Invisible Friends, Personified Objects, and Pretend Identities

ERIC Educational Resources Information Center

Taylor, Marjorie; Sachet, Alison B.; Maring, Bayta L.; Mannering, Anne M.

2013-01-01

Role-play (i.e., pretending in which children imagine and act out the part of another individual) was assessed with child interviews and parent questionnaires about invisible friends, personified objects, and pretend identities in a sample of 208 young children. Children who engaged in role-play did not differ from other children in age or…

Assessment of Factors Resulting in Abuse Evaluations in Young Children with Minor Head Trauma

ERIC Educational Resources Information Center

Anderst, James D.

2008-01-01

Objective: The primary objective was to determine which of the examined factors prompted physicians to initiate a further abuse evaluation in young children with minor head injury. The recording of important historical elements in the charts of these patients was also evaluated. Methods: Charts of 349 children less than 3 years of age with minor…

Mother-Child Communication about Location: Giving and Following Directions for Finding Hidden Objects

ERIC Educational Resources Information Center

Plumert, Jodie M.; Haggerty, Kathryn A.; Mickunas, Andrew; Herzog, Lauren; Shadrick, Courtney

2012-01-01

We conducted 2 experiments to examine how mothers structure directions to young children for finding hidden objects and how young children use these directions to guide their searches. In Experiment 1, we examined the reference frames mothers use to communicate with their 2.5-, 3-, and 3.5-year-old children about location by asking mothers to…

Effect of Repetition Lag on Priming of Unfamiliar Visual Objects in Young and Older Adults

PubMed Central

Gordon, Leamarie T.; Soldan, Anja; Thomas, Ayanna K.; Stern, Yaakov

2013-01-01

Across three experiments, we examined the effect of repetition lag on priming of unfamiliar visual objects in healthy young and older adults. Multiple levels of lag were examined, ranging from short (one to four intervening stimuli) to long (50+ intervening stimuli). In each experiment, subjects viewed a series of new and repeated line drawings of objects and decided whether they depicted structurally possible or impossible figures. Experiment 1 and 2 found similar levels of priming in young and older adults at short and medium lags. At the longer repetition lags (∼20+ intervening stimuli), older adults showed less overall priming, as measured by reaction time facilitation, than young adults. This indicates that older adults can rapidly encode unfamiliar three-dimensional objects to support priming at shorter lags; however, they cannot maintain these representations over longer intervals. In addition to repetition lag, we also explored the relationship between priming and cognitive reserve, as measured by education and verbal intelligence. In the older adults, higher levels of cognitive reserve were associated with greater reaction time priming, suggesting that cognitive reserve may mediate the relationship between aging and priming. PMID:23276220

OV Bootis: Forty Nights of World-Wide Photometry (Abstract)

NASA Astrophysics Data System (ADS)

Patterson, J.; de Miguel, E.; Barret, D.; Brincat, S.; Boardman, J., Jr.; Buczynski, D.; Campbell, T.; Cejudo, D.; Cook, L.; Cook, M. J.; Collins, D.; Cooney, W.; Dubois, F.; Dvorak, S.; Halpern, J. P.; Kroes, A. J.; Lemay, D.; Licchelli, D.; Mankel, D.; Marshall, M.; Novak, R.; Oksanen, A.; Roberts, G.; Seargeant, J.; Sears, H.; Silcox, A.; Slauson, D.; Stone, G.; Thorstensen, J. R.; Ulowetz, J.; Vanmunster, T.; Wallgren, J.; Wood, M.

2017-12-01

(Abstract only) Among the 1000 known cataclysmic variables, only one appears to belong to the "Galactic halo"-the Population II stars. We report round-the-world photometry of this star (OV Boo) during March-April 2017, when it staged its first certified dwarf-nova outburst. The star is remarkable for its short binary period (66 minutes), high proper motion, metal-poor composition, substellar secondary, sharp white-dwarf eclipses, and nonradial pulsations. Something for everybody - and it even had the good manners to erupt in northern springtime, when it transits near local midnight. Move over, SS Cyg and WZ Sge; there's a new celebrity in town!

Discovery of a substellar companion to the nearby debris disk host HR 2562

DOE PAGES

Konopacky, Quinn M.; Rameau, Julien; Duchêne, Gaspard; ...

2016-09-14

Here, we present the discovery of a brown dwarf companion to the debris disk host star HR 2562. This object, discovered with the Gemini Planet Imager (GPI), has a projected separation of 20.3 ± 0.3 au (more » $$0\\buildrel{\\prime\\prime}\\over{.} 618\\pm 0\\buildrel{\\prime\\prime}\\over{.} 004$$) from the star. With the high astrometric precision afforded by GPI, we have confirmed, to more than 5σ, the common proper motion of HR 2562B with the star, with only a month-long time baseline between observations. Spectral data in the J-, H-, and K-bands show a morphological similarity to L/T transition objects. We assign a spectral type of L7 ± 3 to HR 2562B and derive a luminosity of log(L $${}_{\\mathrm{bol}}$$/$${L}_{\\odot })=-4.62\\pm 0.12$$, corresponding to a mass of 30 ± 15 $${M}_{\\mathrm{Jup}}$$ from evolutionary models at an estimated age of the system of 300–900 Myr. Although the uncertainty in the age of the host star is significant, the spectra and photometry exhibit several indications of youth for HR 2562B. The source has a position angle that is consistent with an orbit in the same plane as the debris disk recently resolved with Herschel. Additionally, it appears to be interior to the debris disk. Though the extent of the inner hole is currently too uncertain to place limits on the mass of HR 2562B, future observations of the disk with higher spatial resolution may be able to provide mass constraints. This is the first brown-dwarf-mass object found to reside in the inner hole of a debris disk, offering the opportunity to search for evidence of formation above the deuterium burning limit in a circumstellar disk.« less

Isolated and companion young brown dwarfs in the taurus and chamaeleon molecular clouds

PubMed

Tamura; Itoh; Oasa; Nakajima

1998-11-06

Infrared imaging observations have detected a dozen faint young stellar objects (YSOs) in the Taurus and Chamaeleon molecular clouds whose near-infrared colors are similar to those of classical T Tauri stars (TTS). They are around four magnitudes fainter than low-luminosity YSOs in Taurus detected in earlier surveys and as much as eight magnitudes fainter than typical TTS. The extreme faintness of the objects and their lower luminosity relative to previously identified brown dwarfs in the Pleiades indicate that these faint YSOs are very young brown dwarfs on the order of 1 million years old.

GPI Spectroscopy of the Mass, Age, and Metallicity Benchmark Brown Dwarf HD 4747 B

NASA Astrophysics Data System (ADS)

Crepp, Justin R.; Principe, David A.; Wolff, Schuyler; Giorla Godfrey, Paige A.; Rice, Emily L.; Cieza, Lucas; Pueyo, Laurent; Bechter, Eric B.; Gonzales, Erica J.

2018-02-01

The physical properties of brown dwarf companions found to orbit nearby, solar-type stars can be benchmarked against independent measures of their mass, age, chemical composition, and other parameters, offering insights into the evolution of substellar objects. The TRENDS high-contrast imaging survey has recently discovered a (mass/age/metallicity) benchmark brown dwarf orbiting the nearby (d = 18.69 ± 0.19 pc), G8V/K0V star HD 4747. We have acquired follow-up spectroscopic measurements of HD 4747 B using the Gemini Planet Imager to study its spectral type, effective temperature, surface gravity, and cloud properties. Observations obtained in the H-band and K 1-band recover the companion and reveal that it is near the L/T transition (T1 ± 2). Fitting atmospheric models to the companion spectrum, we find strong evidence for the presence of clouds. However, spectral models cannot satisfactorily fit the complete data set: while the shape of the spectrum can be well-matched in individual filters, a joint fit across the full passband results in discrepancies that are a consequence of the inherent color of the brown dwarf. We also find a 2σ tension in the companion mass, age, and surface gravity when comparing to evolutionary models. These results highlight the importance of using benchmark objects to study “secondary effects” such as metallicity, non-equilibrium chemistry, cloud parameters, electron conduction, non-adiabatic cooling, and other subtleties affecting emergent spectra. As a new L/T transition benchmark, HD 4747 B warrants further investigation into the modeling of cloud physics using higher resolution spectroscopy across a broader range of wavelengths, polarimetric observations, and continued Doppler radial velocity and astrometric monitoring.

Hunting for brown dwarf binaries with X-Shooter

NASA Astrophysics Data System (ADS)

Manjavacas, E.; Goldman, B.; Alcalá, J. M.; Zapatero-Osorio, M. R.; Béjar, B. J. S.; Homeier, D.; Bonnefoy, M.; Smart, R. L.; Henning, T.; Allard, F.

2015-05-01

The refinement of the brown dwarf binary fraction may contribute to the understanding of the substellar formation mechanisms. Peculiar brown dwarf spectra or discrepancy between optical and near-infrared spectral type classification of brown dwarfs may indicate unresolved brown dwarf binary systems. We obtained medium-resolution spectra of 22 brown dwarfs of potential binary candidates using X-Shooter at the VLT. We aimed to select brown dwarf binary candidates. We also tested whether BT-Settl 2014 atmospheric models reproduce the physics in the atmospheres of these objects. To find different spectral type spectral binaries, we used spectral indices and we compared the selected candidates to single spectra and composition of two single spectra from libraries, to try to reproduce our X-Shooter spectra. We also created artificial binaries within the same spectral class, and we tried to find them using the same method as for brown dwarf binaries with different spectral types. We compared our spectra to the BT-Settl models 2014. We selected six possible candidates to be combination of L plus T brown dwarfs. All candidates, except one, are better reproduced by a combination of two single brown dwarf spectra than by a single spectrum. The one-sided F-test discarded this object as a binary candidate. We found that we are not able to find the artificial binaries with components of the same spectral type using the same method used for L plus T brown dwarfs. Best matches to models gave a range of effective temperatures between 950 K and 1900 K, a range of gravities between 4.0 and 5.5. Some best matches corresponded to supersolar metallicity.

Attitudes of Young African American Fathers Toward Early Childbearing

ERIC Educational Resources Information Center

Davies, Susan L.; Dix, Emily S.; Rhodes, Scott D.; Harrington, Kathleen F.; Frison, Sonja; Willis, Leigh

2004-01-01

Objective : To qualitatively examine the perceptions of young fathers toward issues related to early childbearing. Methods : Focus groups were held with male partners of adolescent females who had become pregnant while participating in an HIV-prevention trial. Results : Primary domains that emerged included young male's desire for pregnancy, their…

Teaching the Young Child: Goals for Illinois.

ERIC Educational Resources Information Center

Katz, Lilian G.

This paper, outlining the present goals, purposes and future role of the Illinois Association for the Education of Young Children (ILLAEYC), discusses what is involved in providing high quality programs for young children everywhere, not only in Illinois. Among ILLAEYC's objectives: (1) to provide a channel of information for people working with…

Motivational Traits of Elite Young Soccer Players

ERIC Educational Resources Information Center

Stewart, Craig; Meyers, Michael C.

2004-01-01

Among the most overlooked aspects in the development of elite young soccer players is that of specific psychological traits. Of those traits, motivation has important implications for programs whose objectives are identification and cultivation of young, skilled performers. The growth in popularity of soccer by youth and the successes experienced…

Selective attention affects conceptual object priming and recognition: a study with young and older adults.

PubMed

Ballesteros, Soledad; Mayas, Julia

2014-01-01

In the present study, we investigated the effects of selective attention at encoding on conceptual object priming (Experiment 1) and old-new recognition memory (Experiment 2) tasks in young and older adults. The procedures of both experiments included encoding and memory test phases separated by a short delay. At encoding, the picture outlines of two familiar objects, one in blue and the other in green, were presented to the left and to the right of fixation. In Experiment 1, participants were instructed to attend to the picture outline of a certain color and to classify the object as natural or artificial. After a short delay, participants performed a natural/artificial speeded conceptual classification task with repeated attended, repeated unattended, and new pictures. In Experiment 2, participants at encoding memorized the attended pictures and classify them as natural or artificial. After the encoding phase, they performed an old-new recognition memory task. Consistent with previous findings with perceptual priming tasks, we found that conceptual object priming, like explicit memory, required attention at encoding. Significant priming was obtained in both age groups, but only for those pictures that were attended at encoding. Although older adults were slower than young adults, both groups showed facilitation for attended pictures. In line with previous studies, young adults had better recognition memory than older adults.

Selective attention affects conceptual object priming and recognition: a study with young and older adults

PubMed Central

Ballesteros, Soledad; Mayas, Julia

2015-01-01

In the present study, we investigated the effects of selective attention at encoding on conceptual object priming (Experiment 1) and old–new recognition memory (Experiment 2) tasks in young and older adults. The procedures of both experiments included encoding and memory test phases separated by a short delay. At encoding, the picture outlines of two familiar objects, one in blue and the other in green, were presented to the left and to the right of fixation. In Experiment 1, participants were instructed to attend to the picture outline of a certain color and to classify the object as natural or artificial. After a short delay, participants performed a natural/artificial speeded conceptual classification task with repeated attended, repeated unattended, and new pictures. In Experiment 2, participants at encoding memorized the attended pictures and classify them as natural or artificial. After the encoding phase, they performed an old–new recognition memory task. Consistent with previous findings with perceptual priming tasks, we found that conceptual object priming, like explicit memory, required attention at encoding. Significant priming was obtained in both age groups, but only for those pictures that were attended at encoding. Although older adults were slower than young adults, both groups showed facilitation for attended pictures. In line with previous studies, young adults had better recognition memory than older adults. PMID:25628588

Radial velocity variability and stellar properties of FGK stars in the cores of NGC 2516 and NGC 2422

NASA Astrophysics Data System (ADS)

Bailey, John I.; Mateo, Mario; White, Russel J.; Shectman, Stephen A.; Crane, Jeffrey D.

2018-04-01

We present multi-epoch high-dispersion optical spectra obtained with the Michigan/Magellan Fibre System of 126 and 125 Sun-like stars in the young clusters NGC 2516 (141 Myr) and NGC 2422 (73 Myr). We determine stellar properties including radial velocity (RV), Teff, [Fe/H], [α/Fe] and the line-of-sight rotation rate, vrsin (i), from these spectra. Our median RV precision of 80 m s-1 on individual epochs that span a temporal baseline of 1.1 yr enables us to investigate membership and stellar binarity, and to search for sub-stellar companions. We determine membership probabilities and RV variability probabilities for our sample along with candidate companion orbital periods for a select subset of stars. In NGC 2516, we identified 81 RV members, 27 spectroscopic binaries (17 previously identified as photometric binaries) and 16 other stars that show significant RV variability after accounting for average stellar jitter at the 74 m s-1 level. In NGC 2422, we identify 57 members, 11 spectroscopic binaries and three other stars that show significant RV variability after accounting for an average jitter of 138 m s-1. We use Monte Carlo simulations to verify our stellar jitter measurements, determine the proportion of exoplanets and stellar companions to which we are sensitive, and estimate companion-mass limits for our targets. We also report mean cluster metallicity, velocity and velocity dispersion based on our member targets. We identify 58 non-member stars as RV variables, 24 of which have RV amplitudes that imply stellar or brown-dwarf mass companions. Finally, we note the discovery of a separate RV clustering of stars in our NGC 2422 sample.

Sixteen month decline in the 850 micron continuum brightness of the young stellar object HOPS 358 in NGC 2068

NASA Astrophysics Data System (ADS)

Mairs, Steve; Bell, Graham S.; Johnstone, Doug; Herczeg, Gregory J.; Bower, Geoffrey C.; Aikawa, Yuri; Lee, Jeong-Eun; Chen, Huei-Ru Vivien; Hatchell, Jennifer; Kang, Miju; Contreras Pena, Carlos; Scholz, Alexander; Naylor, Tim

2018-04-01

As part of our young stellar object (YSO) sub-mm monthly monitoring programme, the JCMT Transient Survey (Herczeg et al. 2017 ApJ, 849, 43; Johnstone et al. 2018 ApJ, 854, 31), we have uncovered a steady sixteen-month decline in the 850 micron peak brightness of YSO HOPS 358 (R.A.

The Effects of Age on Divergent Thinking and Creative Objects Production: A Cross-Sectional Study

ERIC Educational Resources Information Center

Massimiliano, Palmiero

2015-01-01

Age-related changes in divergent thinking and creative objects production were investigated in 150 native Italian speakers, divided into six age groups, each one comprised 25 participants: young (20-29), young adult (30-39), middle aged (40-49), adult-old (50-59), old (60-69), and old-old (70-80). Two tasks were used: the alternative uses task,…

OBJECT REPRESENTATION, IDENTITY, AND THE PARADOX OF EARLY PERMANENCE: Steps Toward a New Framework.

PubMed

Meltzoff, Andrew N; Moore, M Keith

1998-01-01

The sensorimotor theory of infancy has been overthrown, but there is little consensus on a replacement. We hypothesize that a capacity for representation is the starting point for infant development, not its culmination. Logical distinctions are drawn between object representation, identity, and permanence. Modern experiments on early object permanence and deferred imitation suggest: (a) even for young infants, representations persist over breaks in sensory contact, (b) numerical identity of objects ( O s) is initially specified by spatiotemporal criteria (place and trajectory), (c) featural and functional identity criteria develop, (d) events are analyzed by comparing representations to current perception, and (e) representation operates both prospectively, anticipating future contacts with an O , and retrospectively, reidentifying an O as the "same one again." A model of the architecture and functioning of the early representational system is proposed. It accounts for young infants' behavior toward absent people and things in terms of their efforts to determine the identity of objects. Our proposal is developmental without denying innate structure and elevates the power of perception and representation while being cautious about attributing complex concepts to young infants.

OBJECT REPRESENTATION, IDENTITY, AND THE PARADOX OF EARLY PERMANENCE: Steps Toward a New Framework

PubMed Central

Meltzoff, Andrew N.; Moore, M. Keith

2013-01-01

The sensorimotor theory of infancy has been overthrown, but there is little consensus on a replacement. We hypothesize that a capacity for representation is the starting point for infant development, not its culmination. Logical distinctions are drawn between object representation, identity, and permanence. Modern experiments on early object permanence and deferred imitation suggest: (a) even for young infants, representations persist over breaks in sensory contact, (b) numerical identity of objects (Os) is initially specified by spatiotemporal criteria (place and trajectory), (c) featural and functional identity criteria develop, (d) events are analyzed by comparing representations to current perception, and (e) representation operates both prospectively, anticipating future contacts with an O, and retrospectively, reidentifying an O as the “same one again.” A model of the architecture and functioning of the early representational system is proposed. It accounts for young infants’ behavior toward absent people and things in terms of their efforts to determine the identity of objects. Our proposal is developmental without denying innate structure and elevates the power of perception and representation while being cautious about attributing complex concepts to young infants. PMID:25147418

Archetype and object: primary deintegration and primary love in analytical play therapy with young children.

PubMed

Peery, J Craig

2002-07-01

Jungian and post-Jungian theory of the development of the child's psyche is reviewed. A discrimination between primary and secondary deintegration is suggested. Post-Freudian theory regarding primary object relations is integrated with the Jungian model. The two approaches can contribute synergistically to inform and advance play therapy with young children. Patients from widely diverse cultural backgrounds use their relationship with the therapist as a helpful person (object), and engage in archetypal material from the collective unconscious, to help them work on and through their unresolved emotional issues.

Response of Haloalkaliphilic Archaeon Natronococcus Jeotgali RR17 to Hypergravity

NASA Astrophysics Data System (ADS)

Thombre, Rebecca S.; Bhalerao, Aniruddha R.; Shinde, Vinaya D.; Dhar, Sunil Kumar; Shouche, Yogesh S.

2017-06-01

The survival of archaeabacteria in extreme inhabitable environments on earth that challenge organismic survival is ubiquitously known. However, the studies related to the effect of hypergravity on the growth and proliferation of archaea are unprecedented. The survival of organisms in hypergravity and rocks in addition to resistance to cosmic radiations, pressure and other extremities is imperative to study the possibilities of microbial travel between planets and endurance in hyperaccelerative forces faced during ejection of rocks from planets. The current investigation highlights the growth of an extremophilic archaeon isolated from a rocky substrate in hypergravity environment. The haloalkaliphilic archaeon, Natronococcus jeotgali RR17 was isolated from an Indian laterite rock, submerged in the Arabian sea lining Coastal Maharashtra, India. The endolithic haloarchaeon was subjected to hypergravity from 56 - 893 X gusing acceleration generated by centrifugal rotation. The cells of N. jeotgali RR17 proliferated and demonstrated good growth in hypergravity (223 X g). This is the first report on isolation of endolithic haloarchaeon N. jeotgali RR17 from an Indian laterite rock and its ability to proliferate in hypergravity. The present study demonstrates the ability of microbial life to survive and proliferate in hypergravity. Thus the inability of organismic growth in hypergravity may no longer be a limitation for astrobiology studies related to habitability of substellar objects, brown dwarfs and other planetary bodies in the universe besides planet earth.

Convective Dynamics and Disequilibrium Chemistry in the Atmospheres of Giant Planets and Brown Dwarfs

NASA Astrophysics Data System (ADS)

Bordwell, Baylee; Brown, Benjamin P.; Oishi, Jeffrey S.

2018-02-01

Disequilibrium chemical processes significantly affect the spectra of substellar objects. To study these effects, dynamical disequilibrium has been parameterized using the quench and eddy diffusion approximations, but little work has been done to explore how these approximations perform under realistic planetary conditions in different dynamical regimes. As a first step toward addressing this problem, we study the localized, small-scale convective dynamics of planetary atmospheres by direct numerical simulation of fully compressible hydrodynamics with reactive tracers using the Dedalus code. Using polytropically stratified, plane-parallel atmospheres in 2D and 3D, we explore the quenching behavior of different abstract chemical species as a function of the dynamical conditions of the atmosphere as parameterized by the Rayleigh number. We find that in both 2D and 3D, chemical species quench deeper than would be predicted based on simple mixing-length arguments. Instead, it is necessary to employ length scales based on the chemical equilibrium profile of the reacting species in order to predict quench points and perform chemical kinetics modeling in 1D. Based on the results of our simulations, we provide a new length scale, derived from the chemical scale height, that can be used to perform these calculations. This length scale is simple to calculate from known chemical data and makes reasonable predictions for our dynamical simulations.

The WIRED Survey. I. A Bright IR Excess Due to Dust Around the Heavily Polluted White Dwarf Galex J193156.8+011745

NASA Technical Reports Server (NTRS)

Debes, John H.; Hoard, D. W.; Kilic, Mukremin; Wachter, Stefanie; Leisawitz, David T.; Cohen, Martin; Kirkpatrick, J. Davy; Griffith, Roger L.

2011-01-01

With the launch of the Wide-Field Infrared Survey Explorer (WISE), a new era of detecting planetary debris around white dwarfs (WDs) has begun with the WISE InfraRed Excesses around Degenerates (WIRED) Survey. The WIRED survey will be sensitive to substellar objects and dusty debris around WDs out to distances exceeding 100 pc, well beyond the completeness level of local WDs and covering a large fraction of known WDs detected with the SDSS DR4 WD catalog. In this paper, we report an initial result of the WIRED survey, the detection of the heavily polluted hydrogen WD (spectral type DAZ) GALEX Jl93156.S-KlI1745 at 3.35 and 4.6/Lm. We find that the excess is consistent with either a narrow dusty ring with an inner radius of 29 RWD. outer radius of 40 RWD, and a face-on inclination, or a disk with an inclination of 70 , an inner radius of 23 RWD. and an outer radius of 80 RWD. We also report initial optical spectroscopic monitoring of several metal lines present in the photosphere and find no variability in the line strengths or radial velocities of the lines. We rule out all but planetary mass companions to GALEXl931 out to 0.5 AU.

Discovery of an M9.5 Candidate Brown Dwarf in the TW Hydrae Association: DENIS J124514.1-442907

NASA Astrophysics Data System (ADS)

Looper, Dagny L.; Burgasser, Adam J.; Kirkpatrick, J. Davy; Swift, Brandon J.

2007-11-01

We report the discovery of a fifth candidate substellar system in the ~5-10 Myr TW Hydrae association: DENIS J124514.1-442907. This object has a NIR spectrum remarkably similar to that of 2MASS J1139511-315921, a known TW Hydrae brown dwarf, with low surface gravity features such as a triangular-shaped H band, deep H2O absorption, weak alkali lines, and weak hydride bands. We find an optical spectral type of M9.5 and estimate a mass of <~24 MJup, assuming an age of ~5-10 Myr. While the measured proper motion for DENIS J124514.1-442907 is inconclusive as a test for membership, its position in the sky is coincident with the TW Hydrae association. A more accurate proper-motion measurement, higher resolution spectroscopy for radial velocity, and a parallax measurement are needed to derive the true space motion and to confirm its membership. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This Letter includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

On the local standard of rest. [comoving with young objects in gravitational field of spiral galaxies

NASA Technical Reports Server (NTRS)

Yuan, C.

1983-01-01

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a spiral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars. Previously announced in STAR as N83-24443

The peculiar dipping events in the disc-bearing young-stellar object EPIC 204278916

NASA Astrophysics Data System (ADS)

Scaringi, S.; Manara, C. F.; Barenfeld, S. A.; Groot, P. J.; Isella, A.; Kenworthy, M. A.; Knigge, C.; Maccarone, T. J.; Ricci, L.; Ansdell, M.

2016-12-01

EPIC 204278916 has been serendipitously discovered from its K2 light curve that displays irregular dimmings of up to 65 per cent for ≈25 consecutive days out of 78.8 d of observations. For the remaining duration of the observations, the variability is highly periodic and attributed to stellar rotation. The star is a young, low-mass (M-type) pre-main-sequence star with clear evidence of a resolved tilted disc from Atacama Large Millimeter/submillimeter Array (ALMA) observations. We examine the K2 light curve in detail and hypothesize that the irregular dimmings are caused by either a warped inner disc edge or transiting cometary-like objects in either circular or eccentric orbits. The explanations discussed here are particularly relevant for other recently discovered young objects with similar absorption dips.

An intermediate luminosity optical transient (ILOTs) model for the young stellar object ASASSN-15qi

NASA Astrophysics Data System (ADS)

Kashi, Amit; Soker, Noam

2017-07-01

We construct a scenario where the outburst of the young stellar object ASASSN-15qi is an intermediate luminosity optical transient (ILOT). In this scenario, a sub-Jupiter young planet was tidally destructed on to a young main-sequence (MS) star. The system is young, and therefore the radius of the planet is larger than its final value; consequently, its density is smaller. The lower density allows the tidal destruction of the young Saturn-like planet on to the MS star of mass ≈2.4 M⊙, resulting in the formation of a disc and a gravitationally powered ILOT. Unlike the case of the more energetic ILOT V838 Mon, the mass of the destructed planet is too low to inflate a giant envelope, and hence the merger remnant remains hot. If our suggested model holds, this ILOT possesses two interesting properties: (I) its luminosity and total energy are below those of novae; (II) it is not as red as other ILOTs. The unusual outburst of ASASSN-15qi - if indeed is an ILOT - further increases the diversity of the already heterogeneous group of ILOTs. We mark the region on the energy-time diagram occupied by such young ILOTs.

Objective reports versus subjective perceptions of crime and their relationships to accelerometer-measured physical activity in Hispanic caretaker-child dyads.

PubMed

van Bakergem, Margaret; Sommer, Evan C; Heerman, William J; Hipp, James Aaron; Barkin, Shari L

2017-02-01

Crime and safety are commonly cited barriers to physical activity (PA). We had three objectives, 1) describe the association between objective crime measures and perceptions of crime, 2) analyze the relationships between each type of crime and accelerometer-measured physical activity in caretakers and young children (ages 3-5years), and 3) explore for early gender differences in the relationship between crime and physical activity in young children. Data are from the cross-sectional baseline data of an ongoing randomized controlled trial in Nashville, Tennessee spanning September 2012 through May 2014. Data was analyzed from 480 Hispanic dyads (adult caretaker and 3-5year old child). Objective crime rate was assessed in ArcGIS and perception of crime was measured by caretaker agreement with the statement "The crime rate in my neighborhood makes it unsafe to go on walks." The primary outcome was accelerometer-measured physical activity over seven consecutive days. Objective and perceived crime were significantly positively correlated. Caretaker vigorous PA was significantly related to perceptions of crime; however, its relationship to objective crime was not significant. Child PA was not significantly related to caretaker perceptions of crime. However, interactions suggested that the relationship between crime rate and PA was significantly more negative for girls than for boys. Objective and subjective measures of crime rate are expected to be important correlates of PA, but they appear to have complex relationships that are different for adults than they are for young children, as well as for young girls compared to boys, and research has produced conflicting findings. Copyright © 2016 Elsevier Inc. All rights reserved.

Objective reports versus subjective perceptions of crime and their relationships to accelerometer-measured physical activity in Hispanic caretaker-child dyads

PubMed Central

van Bakergem, Margaret; Sommer, Evan C.; Heerman, William J.; Hipp, James Aaron; Barkin, Shari L.

2016-01-01

Crime and safety are commonly cited barriers to physical activity (PA). We had three objectives, 1) describe the association between objective crime measures and perceptions of crime, 2) analyze the relationships between each type of crime and accelerometer-measured physical activity in caretakers and young children (ages 3–5 years), and 3) explore for early gender differences in the relationship between crime and physical activity in young children. Data are from the cross-sectional baseline data of an ongoing randomized controlled trial in Nashville, Tennessee spanning September 2012 through May 2014. Data was analyzed from 480 Hispanic dyads (adult caretaker and 3–5 year old child). Objective crime rate was assessed in ArcGIS and perception of crime was measured by caretaker agreement with the statement “The crime rate in my neighborhood makes it unsafe to go on walks.” The primary outcome was accelerometer-measured physical activity over seven consecutive days. Objective and perceived crime were significantly positively correlated. Caretaker vigorous PA was significantly related to perceptions of crime; however, its relationship to objective crime was not significant. Child PA was not significantly related to caretaker perceptions of crime. However, interactions suggested that the relationship between crime rate and PA was significantly more negative for girls than for boys. Objective and subjective measures of crime rate are expected to be important correlates of PA, but they appear to have complex relationships that are different for adults than they are for young children, as well as for young girls compared to boys, and research has produced conflicting findings. PMID:27939263

A Helping Hand with Language Learning: Teaching French Vocabulary with Gesture

ERIC Educational Resources Information Center

Porter, Alison

2016-01-01

Finding ways to make language teaching practices both active and effective is of great importance for young learners. However, extending the foreign language production of young learners in instructional settings beyond the naming of objects is often challenging. The memorisation abilities of very young learners (children aged 5-7) sometimes…

Low-Income Mothers' Food Practices with Young Children: A Qualitative Longitudinal Study

ERIC Educational Resources Information Center

Harden, Jeni; Dickson, Adele

2015-01-01

Objective: Young children living in socioeconomically deprived areas of Scotland have an increased risk of becoming overweight or obese. To enhance understanding of the wider contexts within which family food practices are developed, this study examined the experiences of low-income mothers with young children. Design: Qualitative longitudinal…

Examining the Conflict and Interconnectedness of Young People's Ideas about Environmental Issues, Responsibility and Action

ERIC Educational Resources Information Center

Wilks, Leigh; Harris, Neil

2016-01-01

Objective: Young people's environmental views are typically conflicted, with little recognition of the links between environmental issues or between environmental responsibility and action. The purpose of this study was to clarify whether young people's understanding of the environment is in conflict or whether they are forming interconnections…

Program of Vocational Rehabilitation for Young Adult Offenders.

ERIC Educational Resources Information Center

Pennsylvania State Correctional Inst., Camp Hill.

Full development of the educational, occupational, and attitudinal abilities of young delinquents admitted to the Camp Hill State Correctional Institute was the object of this Elementary and Secondary Education Act Title I Program. Young adults 15-21 years committed to Camp Hill average 6.1 on the standard educational battery test and their…

Young Adult Outcome of Hyperactive Children: Adaptive Functioning in Major Life Activities

ERIC Educational Resources Information Center

Barkley, Russell A.; Fischer, Mariellen; Smallish, Lori; Fletcher, Kenneth

2006-01-01

Objective: The authors report the adaptive functioning of hyperactive and control children in southeastern Wisconsin (Milwaukee) followed to young adulthood. Method: Interviews with participants concerning major life activities were collected between 1992 and 1996 and used along with employer ratings and high school records at the young adult…

Understanding Tobacco-Related Attitudes among College and Noncollege Young Adult Hookah and Cigarette Users

ERIC Educational Resources Information Center

Lee, Youn Ok; Bahreinifar, Sareh; Ling, Pamela M.

2014-01-01

Objective: To examine differences in tobacco-related attitudes and hookah and cigarette use among college and noncollege young adults. Participants: Time-location samples of young adult bar patrons in San Diego, California ("N" = 2,243), Tulsa ("N" = 2,095) and Oklahoma City ("N" = 2,200), Oklahoma, Albuquerque…

Healthy Behaviors and Lifestyles in Young Adults with a History of Developmental Disabilities

ERIC Educational Resources Information Center

Rurangirwa, Jacqueline; Braun, Kim Van Naarden; Schendel, Diana; Yeargin-Allsopp, Marshalyn

2006-01-01

Objective: Measure select Healthy People 2010 Leading Health Indicators in young adults with and without a history of developmental disabilities (DD) using a population-based cohort. Methods: Young adults were interviewed to assess the prevalence of seven Leading Health Indicators: physical activity, overweight and obesity, tobacco use, substance…

DETERMINATION OF A STANDARD FOOD ITEM FOR ANALYSIS OF PESTICIDE CONSUMPTION IN THE DIETARY INTAKE OF YOUNG CHILDREN

EPA Science Inventory

The objective of this study was to establish a standard food item for the collection of residential use pesticides from household surfaces commonly encountered by young children while eating. The amount of a pesticide that young children ingest during eating is influenced by the ...

Atlas of low-mass young stellar object disks from mid-infrared interferometry

NASA Astrophysics Data System (ADS)

Varga, J.; Ábrahám, P.; Ratzka, Th.; Menu, J.; Gabányi, K.; Kóspál, Á.; van Boekel, R.; Mosoni, L.; Henning, Th.

We present our approach of visibility modeling of disks around low-mass (< 2 M ⊙) young stellar objects (YSOs). We compiled an atlas based on mid-infrared interferometric observations from the MIDI instrument at the VLTI. We use three different models to fit the data. These models allow us to determine overall sizes (and the extent of the inner gaps) of the modeled circumstellar disks.

Planet Forming Protostellar Disks

NASA Technical Reports Server (NTRS)

Lubow, Stephen

1998-01-01

The project achieved many of its objectives. The main area of investigation was the interaction of young binary stars with surrounding protostellar 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.

World Ocean Circulation Experiment (WOCE) Young Investigator Workshops

NASA Technical Reports Server (NTRS)

Austin, Meg

2004-01-01

The World Ocean Circulation Experiment (WOCE) Young Investigator Workshops goals and objectives are: a) to familiarize Young Investigators with WOCE models, datasets and estimation procedures; b) to offer intensive hands-on exposure to these models ard methods; c) to build collaborations among junior scientists and more senior WOCE investigators; and finally, d) to generate ideas and projects leading to fundable WOCE synthesis projects. To achieve these goals and objectives, the Workshop will offer a mixture of tutorial lectures on numerical models and estimation procedures, advanced seminars on current WOCE synthesis activities and related projects, and the opportunity to conduct small projects which put into practice the techniques advanced in the lectures.

Parts and Relations in Young Children's Shape-Based Object Recognition

ERIC Educational Resources Information Center

Augustine, Elaine; Smith, Linda B.; Jones, Susan S.

2011-01-01

The ability to recognize common objects from sparse information about geometric shape emerges during the same period in which children learn object names and object categories. Hummel and Biederman's (1992) theory of object recognition proposes that the geometric shapes of objects have two components--geometric volumes representing major object…

Age-related changes in frequency of mind-wandering and task-related interferences during memory encoding and their impact on retrieval.

PubMed

Maillet, David; Rajah, M Natasha

2013-01-01

During the performance of cognitive tasks such as memory encoding, attention can become decoupled from the external environment and instead focused on internal thoughts related to the appraisal of the current task (task-related interferences; TRI), or personal thoughts unrelated to the task at hand (mind-wandering; MW). However, the association between the frequency of these thoughts experienced at encoding and retrieval accuracy in young and older adults remains poorly understood. In this study young and older adults encoded lists of words using one of two encoding tasks: judging whether words are man-made/natural (objective task), or whether they are pleasant/neutral (subjective task). We measured the frequency of TRI and MW at encoding, and related them to retrieval accuracy in both age groups. We found that encoding task influenced the type of internal thoughts experienced by young, but not older, adults: young exhibited greater MW in the subjective vs the objective task, and greater TRI in the objective vs subjective encoding task. Second, across both tasks we found marked age-related decreases in both MW and TRI at encoding, and frequency of these thoughts negatively impacted memory retrieval in young adults only. We discuss these findings in relation to current theories of ageing, attention and memory.

Health-Seeking Challenges Among Homeless Youth

PubMed Central

Hudson, Angela L.; Nyamathi, Adeline; Greengold, Barbara; Slagle, Alexandra; Koniak-Griffin, Deborah; Khalilifard, Farinaz; Getzoff, Daniel

2010-01-01

Background Approximately 1.5 to 2 million homeless young persons live on the streets in the United States. With the current economic situation, research is needed on quality of services geared toward homeless young adults. Objectives The objective of this study was to explore homeless young adults' perspectives on barriers and facilitators of health-care-seeking behavior and their perspectives on improving existing programs for homeless persons. Methods This article is a descriptive qualitative study using focus groups, with a purposeful sample of 24 homeless drug-using young adults. Results Identified themes were failing access to care based on perceived structural barriers (limited clinic sites, limited hours of operation, priority health conditions, and long wait times) and social barriers (perception of discrimination by uncaring professionals, law enforcement, and society in general). Discussion Results provide insight into programmatic and agency resources that facilitate health-seeking behaviors among homeless young adults and include implications for more research with providers of homeless health and social services. PMID:20404776

Younger vampire bats (Desmodus rotundus) are more likely than adults to explore novel objects.

PubMed

Carter, Gerald G; Forss, Sofia; Page, Rachel A; Ratcliffe, John M

2018-01-01

The effects of age on neophobia and exploration are best described in birds and primates, and broader comparisons require reports from other taxa. Here we present data showing age-dependent exploration in a long-lived social species, the common vampire bat (Desmodus rotundus). A previous study found that vampire bats regurgitated food to partners trapped in a cage. Interestingly, while only a few adult bats visited the trapped bat, in every trial all or most of the eight young males in the colony would visit the trapped bat without feeding it. To test whether this behavioral difference resulted from age class differences in exploration, we compared responses of the bats to a trapped conspecific versus an inanimate novel object. Some adults and young showed interest in trapped conspecifics, but only the young males explored the novel objects. Additional novel object tests in a second captive colony showed that higher rates of novel object exploration were shown by young of both sexes. Our results corroborate past findings from other mammals and birds that age predicts exploration. If age-dependent exploration is indeed adaptive, then the role of age as a predictor of exploration tendency should depend on species-specific life history traits. Finally, because younger vampire bats also appear to have higher exposure to pathogens such as rabies virus, there may be implications for pathogen transmission if younger and more exploratory vampire bats are more likely to feed on novel hosts.

Longitudinal Impact of Attachment-Related Risk and Exposure to Trauma among Young Children after Hurricane Katrina

ERIC Educational Resources Information Center

Osofsky, Joy; Kronenberg, Mindy; Bocknek, Erika; Hansel, Tonya Cross

2015-01-01

Background: Research suggests that young childhood is a dynamic developmental phase during which risks to attachment figures as well as traumatic events may be particularly important. The loss and disruption associated with Hurricane Katrina highlighted the vulnerabilities and special needs of young children exposed to natural disaster. Objective:…

A Long-Term Outcome Study of Selective Mutism in Childhood

ERIC Educational Resources Information Center

Steinhausen, Hans-Christoph; Wachter, Miriam; Laimbock, Karin; Metzke, Christa Winkler

2006-01-01

Objective: Controlled study of the long-term outcome of selective mutism (SM) in childhood. Method: A sample of 33 young adults with SM in childhood and two age- and gender-matched comparison groups were studied. The latter comprised 26 young adults with anxiety disorders in childhood (ANX) and 30 young adults with no psychiatric disorders during…

Young Children's Reactions to Mothers' Disclosure of Maternal HIV+ Serostatus

ERIC Educational Resources Information Center

Murphy, Debra A.; Roberts, Kathleen J.; Hoffman, Dannie

2006-01-01

Little is known about the impact of maternal disclosure of HIV-positive serostatus on young children. The objective of this study was to explore this topic, utilizing in-depth qualitative interviews. Qualitative interviews were conducted with 47 mothers who had disclosed to their young, well child, and with the children. The most prevalent child…

A Structural Analysis on Korean Young Children's Mathematical Ability and Its Related Children's and Mothers' Variables

ERIC Educational Resources Information Center

Lee, Hye Jung; Kim, Jihyun

2016-01-01

The objective of this study is to examine the structural relationships among variables that predict the mathematical ability of young children, namely young children's mathematical attitude, exposure to private mathematical learning, mothers' view about their children's mathematical learning, and mothers' mathematical attitude. To this end, we…

Young Children Follow Pointing over Words in Interpreting Acts of Reference

ERIC Educational Resources Information Center

Grassmann, Susanne; Tomasello, Michael

2010-01-01

Adults refer young children's attention to things in two basic ways: through the use of pointing (and other deictic gestures) and words (and other linguistic conventions). In the current studies, we referred young children (2- and 4-year-olds) to things in conflicting ways, that is, by pointing to one object while indicating linguistically (in…

Childhood Predictors of Young Adult Social Functioning in 22q11.2 Deletion Syndrome

ERIC Educational Resources Information Center

Wagner, Kayla E.; Kates, Wendy R.; Fremont, Wanda; Antshel, Kevin M.

2017-01-01

The primary objectives of the current prospective longitudinal study were to (a) describe social functioning outcomes and (b) identify childhood predictors of social functioning in young adults with (22q11.2DS). Childhood predictors of young adult social functioning were examined. Family environment and parental stress in adolescence were…

Articulation Rate and Vowel Space Characteristics of Young Males with Fragile X Syndrome: Preliminary Acoustic Findings

ERIC Educational Resources Information Center

Zajac, David J.; Roberts, Joanne E.; Hennon, Elizabeth A.; Harris, Adrianne A.; Barnes, Elizabeth F.; Misenheimer, Jan

2006-01-01

Purpose: Increased speaking rate is a commonly reported perceptual characteristic among males with fragile X syndrome (FXS). The objective of this preliminary study was to determine articulation rate--one component of perceived speaking rate--and vowel space characteristics of young males with FXS. Method: Young males with FXS (n = 38), …

Catching the Next Burst: the periodic young stellar object EC 53 in Serpens Main is sharply brightening at 850 microns and at near-IR H-band and K-band

NASA Astrophysics Data System (ADS)

Johnstone, Doug; Mairs, Steve; Naylor, Tim; Contreras Pena, Carlos; Varricatt, Watson; Hodapp, Klaus; Herczeg, Gregory J.; Lee, Jeong-Eun; Yoo, Hyunju; Bell, Graham S.; Bower, Geoffrey C.; Aikawa, Yuri; Chen, Huei-Ru Vivien; Hatchell, Jennifer; Park, Sunkyung

2018-05-01

As part of our young stellar object (YSO) sub-mm monthly monitoring programme, the JCMT-Transient Survey (Herczeg et al. 2017 ApJ, 849, 43; Johnstone et al. 2018 ApJ, 854, 31), we are using SCUBA2 to monitor the 850 micron peak brightness of the YSO EC 53 (R.A.

Wide-field Infrared Survey Explorer

NASA Technical Reports Server (NTRS)

Padgett, Deborah

2012-01-01

We present WISE (Wide-field Infrared Survey Explorer) mid-infrared photometry of young stellar object candidates in the Canis Majoris clouds at a distance of 1 kpc. WISE has identified 682 objects with apparent 12 and 22 micron excess emission in a 7 deg x 10 deg field around the CMa Rl cloud . While a substantial fraction of these candidates are likely galaxies, AGB stars, and artifacts from confusion along the galactic plane, others are part of a spectacular cluster of YSOs imaged by WISE along a dark filament in the R1 cloud. Palomar Double Spectrograph observations of several sources in this cluster confirm their identity as young A and B stars with strong emission lines. In this contribution, we plot the optical -mid-infrared spectral energy distribution for the WISE YSO candidates and discuss potential contaminants to the sample . The data demonstrate the utility of WISE in performing wide-area surveys for young stellar objects.

Limited effectiveness of HIV prevention for young people in sub-Saharan Africa: studying the role of intervention and evaluation

PubMed Central

Michielsen, K.

2013-01-01

On average, 2,500 young people (15-24 years) get infected with HIV every day; 80% of which live in sub-Saharan Africa. Since no cure or vaccine is available, reducing sexual risk behaviour in this group is crucial in tackling the epidemic. The general objective of this doctoral study was to improve the effectiveness of HIV prevention interventions for young people in sub-Saharan Africa. First, we assessed the overall effectiveness of such interventions (systematic literature review, meta-analysis). Secondly, we evaluated a school-based peer-led HIV prevention interventions in Rwanda (longitudinal, non-randomized controlled trial), to get insight into how interventions are developed, implemented and evaluated. While the first two objectives demonstrated limited effectiveness, the third objective aimed to identify reasons for this limited effectiveness: a) baseline characteristics of respondents that predict participation were identified (using data from objective 2); b) we studied determinants of young people’s sexual behavior using a qualitative ‘mailbox study’ that assessed the spontaneous thoughts of Rwandan adolescents on sexuality; c) we assessed the role of one specific structural factor: education (literature review and analysis of existing datasets); d) we assessed the theoretical underpinnings of existing HIV prevention interventions for young people in sub-Saharan Africa (literature review). Based on these studies, we discuss two main reasons for the observed limited effectiveness: factors associated with the intervention (strong focus on cognitions and moral, and implementation issues), and with evaluation (design, power, indicators). Recommendations for improving interventions, evaluations and for further research are provided. PMID:24753945

Preplanetary Nebulae: A Hubble Space Telescope Imaging Survey and a New Morphological Classification System

NASA Technical Reports Server (NTRS)

Sahai, Raghvendra; Morris, Mark; Sanchez Contreras, Carmen; Claussen, Mark

2007-01-01

Using the Hubble Space Telescope (HST ), we have carried out a survey of candidate preplanetary nebulae (PPNs). We report here our discoveries of objects having well-resolved geometric structures, and we use the large sample of PPNs now imaged with HST (including previously studied objects in this class) to devise a comprehensive morphological classification system for this category of objects. The wide variety of aspherical morphologies which we have found for PPNs are qualitatively similar to those found for young planetary nebulae (PNs) in previous surveys. We also find prominent halos surrounding the central aspherical shapes in many of our objects; these are direct signatures of the undisturbed circumstellar envelopes of the progenitor AGB stars. Although the majority of these have surface brightness distributions consistent with a constant mass-loss rate with a constant expansion velocity, there are also examples of objects with varying mass-loss rates. As in our surveys of young PNs, we find no round PPNs. The similarities in morphologies between our survey objects and young PNs supports the view that the former are the progenitors of aspherical PNs. This suggests that the primary shaping of a PN does not occur during the PN phase via the fast radiative wind of the hot central star, but significantly earlier in its evolution.

Age doesn’t matter: Memory complaints are related to negative affect throughout adulthood

PubMed Central

Rowell, Shaina F.; Green, Jennifer S.; Teachman, Bethany A.; Salthouse, Timothy A.

2016-01-01

Objectives Memory complaints are present in adults of all ages but are only weakly related to objective memory deficits, raising the question of what their presence may indicate. In older adults, memory complaints are moderately related to negative affect, but there is little research examining this relationship in young and middle-aged adults. This study examined whether memory complaints and negative affect were similarly related across the adult lifespan and in adults with varying levels of objective memory performance. Method The sample included 3,798 healthy adults aged 18 to 99, and was divided into five groups: young, middle-aged, young-old, old-old, and oldest-old adults. Participants completed questionnaire measures of memory complaints and negative affect (neuroticism and depressive and anxiety symptoms), in addition to lab measures of objective memory. Results Using structural equation models, we found that the relationship between memory complaints and negative affect was moderate in all the age groups, and there was no evidence for moderation by objective memory. Conclusion For adults of all ages, perceived memory decline may be distressing and/or negative affect may lead to negative self-evaluations of memory. PMID:26305735

Peer Communication in Online Mental Health Forums for Young People: Directional and Nondirectional Support

PubMed Central

Hanley, Terry; Ujhelyi, Katalin

2017-01-01

Background The Internet has the potential to help young people by reducing the stigma associated with mental health and enabling young people to access services and professionals which they may not otherwise access. Online support can empower young people, help them develop new online friendships, share personal experiences, communicate with others who understand, provide information and emotional support, and most importantly help them feel less alone and normalize their experiences in the world. Objective The aim of the research was to gain an understanding of how young people use an online forum for emotional and mental health issues. Specifically, the project examined what young people discuss and how they seek support on the forum (objective 1). Furthermore, it looked at how the young service users responded to posts to gain an understanding of how young people provided each other with peer-to-peer support (objective 2). Methods Kooth is an online counseling service for young people aged 11-25 years and experiencing emotional and mental health problems. It is based in the United Kingdom and provides support that is anonymous, confidential, and free at the point of delivery. Kooth provided the researchers with all the online forum posts between a 2-year period, which resulted in a dataset of 622 initial posts and 3657 initial posts with responses. Thematic analysis was employed to elicit key themes from the dataset. Results The findings support the literature that online forums provide young people with both informational and emotional support around a wide array of topics. The findings from this large dataset also reveal that this informational or emotional support can be viewed as directive or nondirective. The nondirective approach refers to when young people provide others with support by sharing their own experiences. These posts do not include explicit advice to act in a particular way, but the sharing process is hoped to be of use to the poster. The directive approach, in contrast, involves individuals making an explicit suggestion of what they believe the poster should do. Conclusions This study adds to the research exploring what young people discuss within online forums and provides insights into how these communications take place. Furthermore, it highlights the challenge that organizations may encounter in mediating support that is multidimensional in nature (informational-emotional, directive-nondirective). PMID:28768607

"Children of the city": juvenile justice, property, and place in England and Scotland, 1945-60.

PubMed

Jackson, Louise A; Bartie, Angela

2011-01-01

This article uses cases studies of Dundee and Manchester to explain juvenile property-offending in terms of young people's use of objects and spaces in the period 1945-60. A composite picture is assembled of objects stolen, which reflects growth of the specifically "teenage" consumer market as well as continued significance of young people's contribution to family economies. Concerns about youth, property, and space were reported in newspapers in terms of vandalism and hooliganism. "Play" and "nuisance" were overlapping and contested categories; re-education of young people in the correct use of place, space, and property was a key aim of the postwar juvenile justice system.

X-ray sources associated with young stellar objects in the star formation region CMa R1

NASA Astrophysics Data System (ADS)

Santos-Silva, Thais; Gregorio-Hetem, Jane; Montmerle, Thierry

2013-07-01

In previous works we studied the star formation scenario in the molecular cloud Canis Major R1 (CMa R1), derived from the existence of young stellar population groups near the Be stars Z CMa and GU CMa. Using data from the ROSAT X-ray satellite, having a field-of-view of ~ 1° in diameter, Gregorio-Hetem et al. (2009) discovered in this region young stellar objects mainly grouped in two clusters of different ages, with others located in between. In order to investigate the nature of these objects and to test a possible scenario of sequential star formation in this region, four fields (each 30 arcmin diameter, with some overlap) have been observed with the XMM-Newton satellite, with a sensitivity about 10 times better than ROSAT. The XMM-Newton data are currently under analysis. Preliminary results indicate the presence of about 324 sources, most of them apparently having one or more near-infrared counterparts showing typical colors of young stars. The youth of the X-ray sources was also confirmed by X-ray hardness ratio diagrams (XHRD), in different energy bands, giving an estimate of their Lx/Lbol ratios. In addition to these results, we present a detailed study of the XMM field covering the cluster near Z CMa. Several of these sources were classified as T Tauri and Herbig Ae/Be stars, using optical spectroscopy obtained with Gemini telescopes, in order to validate the use of XHRD applied to the entire sample. This classification is also used to confirm the relation between the luminosities in the near-infrared and X-ray bands expected for the T Tauri stars in CMa R1. In the present work we show the results of the study based on the spectra of about 90 sources found nearby Z CMa. We checked that the X-ray spectra (0.3 to 10 keV) of young objects is different from that observed in field stars and extragalactic objects. Some of the candidates also have light curve showing flares that are typical of T Tauri stars, which confirms the young nature of these X-ray sources.

Warm gas towards young stellar objects in Corona Australis. Herschel/PACS observations from the DIGIT key programme

NASA Astrophysics Data System (ADS)

Lindberg, Johan E.; Jørgensen, Jes K.; Green, Joel D.; Herczeg, Gregory J.; Dionatos, Odysseas; Evans, Neal J.; Karska, Agata; Wampfler, Susanne F.

2014-05-01

Context. The effects of external irradiation on the chemistry and physics in the protostellar envelope around low-mass young stellar objects are poorly understood. The Corona Australis star-forming region contains the R CrA dark cloud, comprising several low-mass protostellar cores irradiated by an intermediate-mass young star. Aims: We study the effects of the irradiation coming from the young luminous Herbig Be star R CrA on the warm gas and dust in a group of low-mass young stellar objects. Methods: Herschel/PACS far-infrared datacubes of two low-mass star-forming regions in the R CrA dark cloud are presented. The distributions of CO, OH, H2O, [C ii], [O i], and continuum emission are investigated. We have developed a deconvolution algorithm which we use to deconvolve the maps, separating the point-source emission from the extended emission. We also construct rotational diagrams of the molecular species. Results: By deconvolution of the Herschel data, we find large-scale (several thousand AU) dust continuum and spectral line emission not associated with the point sources. Similar rotational temperatures are found for the warm CO (282 ± 4 K), hot CO (890 ± 84 K), OH (79 ± 4 K), and H2O (197 ± 7 K) emission in the point sources and the extended emission. The rotational temperatures are also similar to those found in other more isolated cores. The extended dust continuum emission is found in two ridges similar in extent and temperature to molecular millimetre emission, indicative of external heating from the Herbig Be star R CrA. Conclusions: Our results show that nearby luminous stars do not increase the molecular excitation temperatures of the warm gas around young stellar objects (YSOs). However, the emission from photodissociation products of H2O, such as OH and O, is enhanced in the warm gas associated with these protostars and their surroundings compared to similar objects not subjected to external irradiation. Table 9 and appendices are available in electronic form at http://www.aanda.org

Color Vision and Hue Categorization in Young Human Infants

ERIC Educational Resources Information Center

Bornstein, Marc H.; And Others

1976-01-01

The main objective of the present investigations was to determine whether or not young human infants see the physical spectrum in a categorical fashion as human adults and animals who possess color vision regularly do. (Author)

Oculomotor Exploration of Impossible Figures in Early Infancy

PubMed Central

Shuwairi, Sarah M.; Johnson, Scott P.

2012-01-01

Previous studies with young infants revealed that young infants can distinguish between displays of possible or impossible figures, which may require detection of inconsistent depth relations among local line junctions that disrupt global object configurations. Here, we used an eye-tracking paradigm to record eye movements in young infants during an object discrimination task with matched pairs of possible and impossible figures. Our goal was to identify differential patterns of oculomotor activity as infants viewed pictures of possible and impossible objects. We predicted that infants would actively attend to specific pictorial depth cues that denote shape (e.g., T-junctions), and in the context of an impossible figure that they would fixate to a greater extent in anomalous regions of the display relative to other parts. By the age of 4 months, infants fixated reliably longer overall on displays of impossible vs. possible cubes, specifically within the critical region where the incompatible lines and irreconcilable depth relations were located, implying an early capacity for selective attention to critical line junction information and integration of local depth cues necessary to perceive object coherence. PMID:23646001

Wide-Field Infrared Survey Explorer Observations of Young Stellar Objects in the Lynds 1509 Dark Cloud in Auriga

NASA Technical Reports Server (NTRS)

Liu, Wilson M.; Padgett, Deborah L.; Terebey, Susan; Angione, John; Rebull, Luisa M.; McCollum, Bruce; Fajardo-Acosta, Sergio; Leisawitz, David

2015-01-01

The Wide-Field Infrared Survey Explorer (WISE) has uncovered a striking cluster of young stellar object (YSO) candidates associated with the L1509 dark cloud in Auriga. The WISE observations, at 3.4, 4.6, 12, and 22 microns, show a number of objects with colors consistent with YSOs, and their spectral energy distributions suggest the presence of circumstellar dust emission, including numerous Class I, flat spectrum, and Class II objects. In general, the YSOs in L1509 are much more tightly clustered than YSOs in other dark clouds in the Taurus-Auriga star forming region, with Class I and flat spectrum objects confined to the densest aggregates, and Class II objects more sparsely distributed. We estimate a most probable distance of 485-700 pc, and possibly as far as the previously estimated distance of 2 kpc.

Academic Self-Concept and Motivation in Young Talents of a Private University in Tarapoto

ERIC Educational Resources Information Center

Carranza, Renzo F.; Apaza, Effer E.

2015-01-01

The objective of this study was to determine the relationship between academic self-concept and academic motivation in young talents (Scholarship 18) at a Private University in Tarapoto city, Peru. The sample was obtained through a probabislitic sampling and there were 92 young talents, being 47.8% male and 52.2% female between 17 and 22 years…

Comparisons of Gambling and Alcohol Use among College Students and Noncollege Young People in the United States

ERIC Educational Resources Information Center

Barnes, Grace M.; Welte, John W.; Hoffman, Joseph H.; Tidwell, Marie-Cecile O.

2010-01-01

Objective: Gambling and alcohol use were compared for college and noncollege young adults in the US population. Participants: Participants were 1,000 respondents aged 18 to 21. Methods: Data were analyzed from a representative household sample of US young people aged 14 to 21 years old. Telephone interviews were conducted between August 2005 and…

A Cluster Randomized Controlled Trial Testing the Effectiveness of Houvast: A Strengths-Based Intervention for Homeless Young Adults

ERIC Educational Resources Information Center

Krabbenborg, Manon A. M.; Boersma, Sandra N.; van der Veld, William M.; van Hulst, Bente; Vollebergh, Wilma A. M.; Wolf, Judith R. L. M.

2017-01-01

Objective: To test the effectiveness of Houvast: a strengths-based intervention for homeless young adults. Method: A cluster randomized controlled trial was conducted with 10 Dutch shelter facilities randomly allocated to an intervention and a control group. Homeless young adults were interviewed when entering the facility and when care ended.…

Teaching the Imitation and Spontaneous Use of Descriptive Gestures in Young Children with Autism Using a Naturalistic Behavioral Intervention

ERIC Educational Resources Information Center

Ingersoll, Brooke; Lewis, Elizabeth; Kroman, Emily

2007-01-01

Children with autism exhibit deficits in the imitation and spontaneous use of descriptive gestures. Reciprocal Imitation Training (RIT), a naturalistic imitation intervention, has been shown to increase object imitation skills in young children with autism. A single-subject, multiple-baseline design across five young children with autism was used…

Hmong Food Helps Us Remember Who We Are: Perspectives of Food Culture and Health among Hmong Women with Young Children

ERIC Educational Resources Information Center

Vue, Wa; Wolff, Cindy; Goto, Keiko

2011-01-01

Objective: To examine perspectives on food habits, acculturation, and health among Hmong women with young children in northern California. Methods: Qualitative interviews were conducted with 15 Hmong mothers with young children in a low-income community of northern California. The interviews were transcribed and coded based on the principles of…

Changing the Culture of Young People's Binge Drinking: From Motivations to Practical Solutions

ERIC Educational Resources Information Center

Coleman, Lester; Cater, Suzanne

2007-01-01

Aims: This paper explores young people's own opinions about how the "drinking to get drunk" culture can be changed. More precisely, the two objectives of this study were to explore: (1) whether young people viewed binge drinking as a real "problem"; and (2) what they thought could be done to reduce binge drinking. Methods:…

The History and Timing of Depression Onset as Predictors of Young Adult Self-Esteem

ERIC Educational Resources Information Center

Gayman, Mathew D.; Lloyd, Donald A.; Ueno, Koji

2011-01-01

Depression often emerges early in the lifecourse and is consistently shown to be associated with poor self-esteem. The 3 main objectives of the current study are to (1) evaluate the association between a history major depression and self-esteem in young adulthood, (2) assess the relationship between timing of depression onset and young adult…

Young Adults' Risk Perceptions of Various Tobacco Products Relative to Cigarettes: Results from the National Young Adult Health Survey

ERIC Educational Resources Information Center

Wackowski, Olivia A.; Delnevo, Cristine D.

2016-01-01

Objectives: Tobacco product risk perceptions may influence whether individuals use those products instead of or in addition to regular cigarettes. This study aimed to explore risk perceptions of various tobacco products relative to traditional cigarettes with young adults, a group with higher rates of tobacco use. Method: We examined risk…

Interventions for Young Bereaved Children: A Systematic Review and Implications for School Mental Health Providers

ERIC Educational Resources Information Center

Chen, Cliff Yung-Chi; Panebianco, Andrea

2018-01-01

Background: Many young children experience the death of a family member and they may be at risk for developing psychological and behavioral problems, but not much is known about how to help young children cope with such a stressful and painful experience. Objective: The purposes of this study are to identify the interventions for bereaved young…

The Religious Behavior and Beliefs of Orthodox Young People in the Mogilev Area

ERIC Educational Resources Information Center

Iudin, V. V.

2007-01-01

In the past twenty years a generation has grown up that, unlike previous generations, was not the object of atheistic upbringing. In this article, based on sociological surveys of young people in Mogilev and Mogilev Oblast conducted in 2002 and 2004, the author examines the religious behavior of young believers and analyze the level and degree of…

Actions Versus Likenesses As Determinants of Early Object Concepts.

ERIC Educational Resources Information Center

Latimer, James

This experiment was designed to test whether paired objects described as interacting through movement are more memorable to young children than the same objects described as alike in structure or color. Drawings of eight familiar objects were presented in unfamiliar combinations to forty-five 4-year-old subjects. Objects were described as…

Children and Objects: Affection and Infection

ERIC Educational Resources Information Center

Jones, Liz; MacLure, Maggie; Holmes, Rachel; MacRae, Christina

2012-01-01

This paper considers young children's (aged 3-5 years) relations with objects, and in particular objects that are brought from home to school. We begin by considering the place of objects within early years classrooms and their relationship to children's education before considering why some objects are often separated from their owners on entry…

Near- and Mid-Infrared Photometry of the Pleiades and a New List of Substellar Candidate Members

NASA Astrophysics Data System (ADS)

Stauffer, John R.; Hartmann, Lee W.; Fazio, Giovanni G.; Allen, Lori E.; Patten, Brian M.; Lowrance, Patrick J.; Hurt, Robert L.; Rebull, Luisa M.; Cutri, Roc M.; Ramirez, Solange V.; Young, Erick T.; Rieke, George H.; Gorlova, Nadya I.; Muzerolle, James C.; Slesnick, Cathy L.; Skrutskie, Michael F.

2007-10-01

We make use of new near- and mid-IR photometry of the Pleiades cluster in order to help identify proposed cluster members. We also use the new photometry with previously published photometry to define the single-star main-sequence locus at the age of the Pleiades in a variety of color-magnitude planes. The new near- and mid-IR photometry extend effectively 2 mag deeper than the 2MASS All-Sky Point Source catalog, and hence allow us to select a new set of candidate very low-mass and substellar mass members of the Pleiades in the central square degree of the cluster. We identify 42 new candidate members fainter than Ks=14 (corresponding to 0.1 Msolar). These candidate members should eventually allow a better estimate of the cluster mass function to be made down to of order 0.04 Msolar. We also use new IRAC data, in particular the images obtained at 8 μm, in order to comment briefly on interstellar dust in and near the Pleiades. We confirm, as expected, that-with one exception-a sample of low-mass stars recently identified as having 24 μm excesses due to debris disks do not have significant excesses at IRAC wavelengths. However, evidence is also presented that several of the Pleiades high-mass stars are found to be impacting with local condensations of the molecular cloud that is passing through the Pleiades at the current epoch. This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

Search for Planetary-mass Companions of the LHB Star eta Corvi

NASA Astrophysics Data System (ADS)

Marengo, Massimo; Lisse, Carey; Stapelfeldt, Karl; Hulsebus, Alan; Sitko, Michael

2016-08-01

The nearby sun-like star eta Corvi (F2V, d = 18 pc, age = 1.2 Gyr) has long been known to possess a bright, dusty Kuiper belt that has been recently resolved with Herschel/PACS. In addition to this structure, eta Corvi is one of the rare mature planetary systems to possess also an inner warm belt (~ 3 AU radius), located within the Terrestrial Habitable Zone (TLZ) of this star. Our characterization of this structure, based on Spitzer/IRS and NASA/IRTF SpeX spectral observations, reveals the signature of ice, organics and silicate dust in this warm belt. This supports the hypothesis that eta Corvi is undergoing a Late Heavy Bombardment (LHB), delivering life-bearing water- and organic-rich material from the Kuiper belt to the TLZ, at roughly the same age as the Solar System?s LHB. For the past four years we have monitored the brightness of eta Corvi?s warm belt with Spitzer/IRAC, finding that its infrared emission has been stable over a multi-year timescale. In 2012 we have also conducted a search for widely separated substellar-mass companions of this star, whose presence as been suggested as a possible trigger for the LHB currently undergoing in the system. This search has led to the identification of three sources with colors and magnitudes consistent with being late-T and Y dwarf companions of this star. We here propose to acquire a new deep roll-subtracted image of the system, 5 years after our first visit, to test for common proper motion of these candidate companions, and determine if any of this sources is physically associated with eta Corvi. A positive identification of a substellar-mass companions (one of which could be a 3-5 MJ planet at ~360 AU from the star) would be a significant step in understanding the processes leading to LHB-like events in a system analogous to the Solar System.

A statistical analysis of seeds and other high-contrast exoplanet surveys: massive planets or low-mass brown dwarfs?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Timothy D.; Spiegel, David S.; McElwain, Michael W.

2014-10-20

We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars. The stars cover a wide range of ages and spectral types, and include five detections (κ And b, two ∼60 M {sub J} brown dwarf companions in the Pleiades, PZ Tel B, and CD–35 2722B). For some analyses we add a currently unpublished set of SEEDS observations, including the detections GJ 504b and GJ 758B. We conduct a uniform, Bayesian analysis of all stellar ages using both membership in a kinematic moving group and activity/rotation age indicators. We then present a new statisticalmore » method for computing the likelihood of a substellar distribution function. By performing most of the integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis of the distribution function derived from radial-velocity planets, finding model-dependent values of ∼30-100 AU. Finally, we model the entire substellar sample, from massive brown dwarfs to a theoretically motivated cutoff at ∼5 M {sub J}, with a single power-law distribution. We find that p(M, a)∝M {sup –0.65} {sup ±} {sup 0.60} a {sup –0.85} {sup ±} {sup 0.39} (1σ errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M {sub J} companions between 10 and 100 AU. This suggests that many of the directly imaged exoplanets known, including most (if not all) of the low-mass companions in our sample, formed by fragmentation in a cloud or disk, and represent the low-mass tail of the brown dwarfs.« less

Social categories guide young children's preferences for novel objects

PubMed Central

Shutts, Kristin; Banaji, Mahzarin R.; Spelke, Elizabeth S.

2009-01-01

To whom do children look when deciding on their own preferences? To address this question, three-year-old children were asked to choose between objects or activities that were endorsed by unfamiliar people who differed in gender, race (White, Black), or age (child, adult). In Experiment 1, children demonstrated robust preferences for objects and activities endorsed by children of their own gender, but less consistent preferences for objects and activities endorsed by children of their own race. In Experiment 2, children selected objects and activities favored by people of their own gender and age. In neither study did most children acknowledge the influence of these social categories. These findings suggest that gender and age categories are encoded spontaneously and influence children's preferences and choices. For young children, gender and age may be more powerful guides to preferences than race. PMID:20590724

Motion and Edge Sensitivity in Perception of Object Unity

ERIC Educational Resources Information Center

Smith, W. Carter; Johnson, Scott P.; Spelke, Elizabeth S.

2003-01-01

Although much evidence indicates that young infants perceive unitary objects by analyzing patterns of motion, infants' abilities to perceive object unity by analyzing Gestalt properties and by integrating distinct views of an object over time are in dispute. To address these controversies, four experiments investigated adults' and infants'…

Object Boundaries Influence Toddlers' Performance in a Search Task

ERIC Educational Resources Information Center

Shutts, Kristin; Keen, Rachel; Spelke, Elizabeth S.

2006-01-01

Previous research has shown that young children have difficulty searching for a hidden object whose location depends on the position of a partly visible physical barrier. Across four experiments, we tested whether children's search errors are affected by two variables that influence adults' object-directed attention: object boundaries and…

Visual Object Pattern Separation Varies in Older Adults

ERIC Educational Resources Information Center

Holden, Heather M.; Toner, Chelsea; Pirogovsky, Eva; Kirwan, C. Brock; Gilbert, Paul E.

2013-01-01

Young and nondemented older adults completed a visual object continuous recognition memory task in which some stimuli (lures) were similar but not identical to previously presented objects. The lures were hypothesized to result in increased interference and increased pattern separation demand. To examine variability in object pattern separation…

A search for embedded young stellar objects in and near the IC 1396 complex

NASA Technical Reports Server (NTRS)

Schwartz, Richard D.; Wilking, Bruce A.; Giulbudagian, Armen L.

1991-01-01

The IRAS data base is used to locate young stellar object candidates in and near the IC 1396 complex located in the Cepheus OB2 association. Co-added survey data are used to identify all sources with a flux density Snu(100) greater than 10 Jy and with Snu(100) greater than Snu(60). The 15 sources located at the positions of globules and dark clouds are further analyzed using the inscan slices to assess the source profiles.

Final Report of the Evaluation of the Summer Program for Mentally Retarded Young Adults--Occupational Training Centers. Summer 1970. ESEA Title I.

ERIC Educational Resources Information Center

Nalven, Fredric; Oliver, Adela

The 1970 Summer Program for Mentally Retarded Young Adults Occupational Training Centers program, funded under Title I of the 1965 Elementary Secondary Education Act, was designed to serve the summer educational, prevocational, and social needs of approximately 170 retarded adolescents and young adults. The general objectives of the project were…

Cannabis and Anxiety and Depression in Young Adults: A Large Prospective Study

ERIC Educational Resources Information Center

Hayatbakhsh, Mohammad R.; Najman, Jake M.; Jamrozik, Konrad; Mamun, Abdullah A.; Alati, Rosa; Bor, William

2007-01-01

Objective: To examine whether age of first use or frequency of use of cannabis is associated with anxiety and depression (AD) in young adults, independent of known potential confounders, including the use of other illicit drugs. Method: A cohort of 3,239 Australian young adults was followed from birth to the age of 21 when data on AD were obtained…

Effects of Green Tea Extract on Learning, Memory, Behavior and Acetylcholinesterase Activity in Young and Old Male Rats

ERIC Educational Resources Information Center

Kaur, Tranum; Pathak, C. M.; Pandhi, P.; Khanduja, K. L.

2008-01-01

Objective: To study the effects of green tea extract administration on age-related cognition in young and old male Wistar rats. Methods: Young and old rats were orally administered 0.5% green tea extract for a period of eight weeks and were evaluated by passive avoidance, elevated maze plus paradigm and changes in acetylcholinesterase activity.…

Educational and Skills-Based Interventions for Preventing Relationship and Dating Violence in Adolescents and Young Adults. A Systematic Review. Campbell Systematic Reviews 2013:14

ERIC Educational Resources Information Center

Fellmeth, Gracia L. T.; Heffernan, Catherine; Nurse, Joanna; Habibula, Shakiba; Sethi, Dinesh

2013-01-01

Background: Educational and skills-based interventions are often used to prevent relationship and dating violence among young people. Objectives: To assess the efficacy of educational and skills-based interventions designed to prevent relationship and dating violence in adolescents and young adults. Search Methods: We searched the Cochrane Central…

The Palomar Transient Factory Orion Project: Eclipsing Binaries and Young Stellar Objects

NASA Astrophysics Data System (ADS)

van Eyken, Julian C.; Ciardi, David R.; Rebull, Luisa M.; Stauffer, John R.; Akeson, Rachel L.; Beichman, Charles A.; Boden, Andrew F.; von Braun, Kaspar; Gelino, Dawn M.; Hoard, D. W.; Howell, Steve B.; Kane, Stephen R.; Plavchan, Peter; Ramírez, Solange V.; Bloom, Joshua S.; Cenko, S. Bradley; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Law, Nicholas M.; Nugent, Peter E.; Ofek, Eran O.; Poznanski, Dovi; Quimby, Robert M.; Grillmair, Carl J.; Laher, Russ; Levitan, David; Mattingly, Sean; Surace, Jason A.

2011-08-01

The Palomar Transient Factory (PTF) Orion project is one of the experiments within the broader PTF survey, a systematic automated exploration of the sky for optical transients. Taking advantage of the wide (3fdg5 × 2fdg3) field of view available using the PTF camera installed at the Palomar 48 inch telescope, 40 nights were dedicated in 2009 December to 2010 January to perform continuous high-cadence differential photometry on a single field containing the young (7-10 Myr) 25 Ori association. Little is known empirically about the formation of planets at these young ages, and the primary motivation for the project is to search for planets around young stars in this region. The unique data set also provides for much ancillary science. In this first paper, we describe the survey and the data reduction pipeline, and present some initial results from an inspection of the most clearly varying stars relating to two of the ancillary science objectives: detection of eclipsing binaries and young stellar objects. We find 82 new eclipsing binary systems, 9 of which are good candidate 25 Ori or Orion OB1a association members. Of these, two are potential young W UMa type systems. We report on the possible low-mass (M-dwarf primary) eclipsing systems in the sample, which include six of the candidate young systems. Forty-five of the binary systems are close (mainly contact) systems, and one of these shows an orbital period among the shortest known for W UMa binaries, at 0.2156509 ± 0.0000071 days, with flat-bottomed primary eclipses, and a derived distance that appears consistent with membership in the general Orion association. One of the candidate young systems presents an unusual light curve, perhaps representing a semi-detached binary system with an inflated low-mass primary or a star with a warped disk, and may represent an additional young Orion member. Finally, we identify 14 probable new classical T-Tauri stars in our data, along with one previously known (CVSO 35) and one previously reported as a candidate weak-line T-Tauri star (SDSS J052700.12+010136.8).

Novel end points for clinical trials in young children with cystic fibrosis.

PubMed

Simpson, Shannon J; Mott, Lauren S; Esther, Charles R; Stick, Stephen M; Hall, Graham L

2013-06-01

Cystic fibrosis (CF) lung disease commences early in the disease progression and is the most common cause of mortality. While new CF disease-modifying agents are currently undergoing clinical trial evaluation, the implementation of such trials in young children is limited by the lack of age-appropriate clinical trial end points. Advances in infant and preschool lung function testing, imaging of the chest and the development of biochemical biomarkers have led to increased possibility of quantifying mild lung disease in young children with CF and objectively monitoring disease progression over the course of an intervention. Despite this, further standardization and development of these techniques is required to provide robust objective measures for clinical trials in this age group.

FREQUENCY OF MOUTHING BEHAVIOR IN YOUNG CHILDREN

EPA Science Inventory

Young children may be more likely than adults to be exposed to pesticides following a residential application as a result of hand- and object-to-mouth contacts in contaminated areas. However, relatively few studies have specifically evaluated mouthing behavior in children less ...

The star fish twins: Two young planetary nebulae with extreme multipolar morphology

NASA Technical Reports Server (NTRS)

Sahai, R.

2000-01-01

We present alpha images of two objects, He 2-47 and M1-37, obtained during a Hubble Space Telescope imaging survey of young planetary nebulae (PNs) selected on the basis of their low-excitation characteristics.

FREQUENCY OF MOUTHING BEHAVIOR IN YOUNG CHILDREN

EPA Science Inventory

Young children, as compared to adults, are more likely to be exposed after a pesticide application due to potential hand- and object-to-mouth contacts in contaminated areas. However, relatively few studies have specifically evaluated mouthing behavior in children <60 months of...

Intact perception but abnormal orientation towards face-like objects in young children with ASD

PubMed Central

Guillon, Quentin; Rogé, Bernadette; Afzali, Mohammad H.; Baduel, Sophie; Kruck, Jeanne; Hadjikhani, Nouchine

2016-01-01

There is ample behavioral evidence of diminished orientation towards faces as well as the presence of face perception impairments in autism spectrum disorder (ASD), but the underlying mechanisms of these deficits are still unclear. We used face-like object stimuli that have been shown to evoke pareidolia in typically developing (TD) individuals to test the effect of a global face-like configuration on orientation and perceptual processes in young children with ASD and age-matched TD controls. We show that TD children were more likely to look first towards upright face-like objects than children with ASD, showing that a global face-like configuration elicit a stronger orientation bias in TD children as compared to children with ASD. However, once they were looking at the stimuli, both groups spent more time exploring the upright face-like object, suggesting that they both perceived it as a face. Our results are in agreement with abnormal social orienting in ASD, possibly due to an abnormal tuning of the subcortical pathway, leading to poor orienting and attention towards faces. Our results also indicate that young children with ASD can perceive a generic face holistically, such as face-like objects, further demonstrating holistic processing of faces in ASD. PMID:26912096

Intact perception but abnormal orientation towards face-like objects in young children with ASD.

PubMed

Guillon, Quentin; Rogé, Bernadette; Afzali, Mohammad H; Baduel, Sophie; Kruck, Jeanne; Hadjikhani, Nouchine

2016-02-25

There is ample behavioral evidence of diminished orientation towards faces as well as the presence of face perception impairments in autism spectrum disorder (ASD), but the underlying mechanisms of these deficits are still unclear. We used face-like object stimuli that have been shown to evoke pareidolia in typically developing (TD) individuals to test the effect of a global face-like configuration on orientation and perceptual processes in young children with ASD and age-matched TD controls. We show that TD children were more likely to look first towards upright face-like objects than children with ASD, showing that a global face-like configuration elicit a stronger orientation bias in TD children as compared to children with ASD. However, once they were looking at the stimuli, both groups spent more time exploring the upright face-like object, suggesting that they both perceived it as a face. Our results are in agreement with abnormal social orienting in ASD, possibly due to an abnormal tuning of the subcortical pathway, leading to poor orienting and attention towards faces. Our results also indicate that young children with ASD can perceive a generic face holistically, such as face-like objects, further demonstrating holistic processing of faces in ASD.

2MASS J11151597+1937266: A Young, Dusty, Isolated, Planetary-mass Object with a Potential Wide Stellar Companion

NASA Astrophysics Data System (ADS)

Theissen, Christopher A.; Burgasser, Adam J.; Bardalez Gagliuffi, Daniella C.; Hardegree-Ullman, Kevin K.; Gagné, Jonathan; Schmidt, Sarah J.; West, Andrew A.

2018-01-01

We present 2MASS J11151597+1937266, a recently identified low-surface-gravity L dwarf, classified as an L2γ based on Sloan Digital Sky Survey optical spectroscopy. We confirm this spectral type with near-infrared spectroscopy, which provides further evidence that 2MASS J11151597+1937266 is a low-surface-gravity L dwarf. This object also shows significant excess mid-infrared flux, indicative of circumstellar material; and its strong Hα emission (EWHα = 560 ± 82 Å) is an indicator of enhanced magnetic activity or weak accretion. Comparison of its spectral energy distribution to model photospheres yields an effective temperature of {1724}-38+184 {{K}}. We also provide a revised distance estimate of 37 ± 6 pc using a spectral type–luminosity relationship for low-surface-gravity objects. The three-dimensional galactic velocities and positions of 2MASS J11151597+1937266 do not match any known young association or moving group. Assuming a probable age in the range of 5–45 Myr, the model-dependent estimated mass of this object is between 7 and 21 M Jup, making it a potentially isolated planetary-mass object. We also identify a candidate co-moving, young stellar companion, 2MASS J11131089+2110086.

Young Children's Self-Generated Object Views and Object Recognition

ERIC Educational Resources Information Center

James, Karin H.; Jones, Susan S.; Smith, Linda B.; Swain, Shelley N.

2014-01-01

Two important and related developments in children between 18 and 24 months of age are the rapid expansion of object name vocabularies and the emergence of an ability to recognize objects from sparse representations of their geometric shapes. In the same period, children also begin to show a preference for planar views (i.e., views of objects held…

Dust in brown dwarfs and extra-solar planets. I. Chemical composition and spectral appearance of quasi-static cloud layers

NASA Astrophysics Data System (ADS)

Helling, Ch.; Woitke, P.; Thi, W.-F.

2008-07-01

Aims: Brown dwarfs are covered by dust cloud layers which cause inhomogeneous surface features and move below the observable τ = 1 level during the object's evolution. The cloud layers have a strong influence on the structure and spectral appearance of brown dwarfs and extra-solar planets, e.g. by providing high local opacities and by removing condensable elements from the atmosphere causing a sub-solar metalicity in the atmosphere. We aim at understanding the formation of cloud layers in quasi-static substellar atmospheres that consist of dirty grains composed of numerous small islands of different solid condensates. Methods: The time-dependent description is a kinetic model describing nucleation, growth and evaporation. It is extended to treat gravitational settling and is applied to the static-stationary case of substellar model atmospheres. From the solution of the dust moments, we determine the grain size distribution function approximately which, together with the calculated material volume fractions, provides the basis for applying effective medium theory and Mie theory to calculate the opacities of the composite dust grains. Results: The cloud particles in brown dwarfs and hot giant-gas planets are found to be small in the high atmospheric layers (a ≈ 0.01 μm), and are composed of a rich mixture of all considered condensates, in particular MgSiO3[s], Mg2SiO4[s] and SiO2[s]. As the particles settle downward, they increase in size and reach several 100 μm in the deepest layers. The more volatile parts of the grains evaporate and the particles stepwise purify to form composite particles of high-temperature condensates in the deeper layers, mainly made of Fe[s] and Al2O3[s]. The gas phase abundances of the elements involved in the dust formation process vary by orders of magnitudes throughout the atmosphere. The grain size distribution is found to be relatively broad in the upper atmospheric layers but strongly peaked in the deeper layers. This reflects the cessation of the nucleation process at intermediate heights. The spectral appearance of the cloud layers in the mid IR (7-20 μm) is close to a grey body with only weak broad features of a few percent, mainly caused by MgSiO3[s], and Mg2SiO4[s]. These features are, nevertheless, a fingerprint of the dust in the higher atmospheric layers that can be probed by observations. Conclusions: Our models predict that the gas phase depletion is much weaker than phase-equilibrium calculations in the high atmospheric layers. Because of the low densities, the dust formation process is incomplete there, which results in considerable amounts of left-over elements that might produce stronger and broader neutral metallic lines.

Discovery of a Highly Unequal-mass Binary T Dwarf with Keck Laser Guide Star Adaptive Optics: A Coevality Test of Substellar Theoretical Models and Effective Temperatures

NASA Astrophysics Data System (ADS)

Liu, Michael C.; Dupuy, Trent J.; Leggett, S. K.

2010-10-01

Highly unequal-mass ratio binaries are rare among field brown dwarfs, with the mass ratio distribution of the known census described by q (4.9±0.7). However, such systems enable a unique test of the joint accuracy of evolutionary and atmospheric models, under the constraint of coevality for the individual components (the "isochrone test"). We carry out this test using two of the most extreme field substellar binaries currently known, the T1 + T6 epsilon Ind Bab binary and a newly discovered 0farcs14 T2.0 + T7.5 binary, 2MASS J12095613-1004008AB, identified with Keck laser guide star adaptive optics. The latter is the most extreme tight binary resolved to date (q ≈ 0.5). Based on the locations of the binary components on the Hertzsprung-Russell (H-R) diagram, current models successfully indicate that these two systems are coeval, with internal age differences of log(age) = -0.8 ± 1.3(-1.0+1.2 -1.3) dex and 0.5+0.4 -0.3(0.3+0.3 -0.4) dex for 2MASS J1209-1004AB and epsilon Ind Bab, respectively, as inferred from the Lyon (Tucson) models. However, the total mass of epsilon Ind Bab derived from the H-R diagram (≈ 80 M Jup using the Lyon models) is strongly discrepant with the reported dynamical mass. This problem, which is independent of the assumed age of the epsilon Ind Bab system, can be explained by a ≈ 50-100 K systematic error in the model atmosphere fitting, indicating slightly warmer temperatures for both components; bringing the mass determinations from the H-R diagram and the visual orbit into consistency leads to an inferred age of ≈ 6 Gyr for epsilon Ind Bab, older than previously assumed. Overall, the two T dwarf binaries studied here, along with recent results from T dwarfs in age and mass benchmark systems, yield evidence for small (≈100 K) errors in the evolutionary models and/or model atmospheres, but not significantly larger. Future parallax, resolved spectroscopy, and dynamical mass measurements for 2MASS J1209-1004AB will enable a more stringent application of the isochrone test. Finally, the binary nature of this object reduces its utility as the primary T3 near-IR spectral typing standard; we suggest SDSS J1206+2813 as a replacement. Most of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Does playing a sports active video game improve young children's ball skill competence?

PubMed

Johnson, Tara M; Ridgers, Nicola D; Hulteen, Ryan M; Mellecker, Robin R; Barnett, Lisa M

2016-05-01

Actual and perceived object control (commonly ball) skill proficiency is associated with higher physical activity in children and adolescents. Active video games (AVGs) encourage whole body movement to control/play the electronic gaming system and therefore provide an opportunity for screen time to become more active. The purpose of this study was to determine whether playing sports AVGs has a positive influence on young children's actual and perceived object control skills. Two group pre/post experimental design study. Thirty-six children aged 6-10 years old from one school were randomly allocated to a control or intervention condition. The Test of Gross Motor Development-3 assessed object control skill. The Pictorial Scale of Perceived Competence for Young Children assessed perceived object control skill. The intervention consisted of 6×50min lunchtime AVG sessions on the Xbox Kinect. Two to three sport games were chosen for participants to play each session. General linear models with either perceived object control or actual object control skill as the outcome variables were conducted. Each base model adjusted for intervention status and pre-score of the respective outcome variable. Additional models adjusted for potential confounding variables (sex of child and game at home). No significant differences between the control and intervention groups were observed for both outcomes. This study found that playing the Xbox Kinect does not significantly influence children's perceived or actual object control skills, suggesting that the utility of the Xbox Kinect for developing perceived and actual object control skill competence is questionable. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

A new statistical method for characterizing the atmospheres of extrasolar planets

NASA Astrophysics Data System (ADS)

Henderson, Cassandra S.; Skemer, Andrew J.; Morley, Caroline V.; Fortney, Jonathan J.

2017-10-01

By detecting light from extrasolar planets, we can measure their compositions and bulk physical properties. The technologies used to make these measurements are still in their infancy, and a lack of self-consistency suggests that previous observations have underestimated their systemic errors. We demonstrate a statistical method, newly applied to exoplanet characterization, which uses a Bayesian formalism to account for underestimated errorbars. We use this method to compare photometry of a substellar companion, GJ 758b, with custom atmospheric models. Our method produces a probability distribution of atmospheric model parameters including temperature, gravity, cloud model (fsed) and chemical abundance for GJ 758b. This distribution is less sensitive to highly variant data and appropriately reflects a greater uncertainty on parameter fits.

Model Atmospheres for Novae in Outburst: Summary of Research

NASA Technical Reports Server (NTRS)

Hauschildt, Peter H.

1999-01-01

This paper presents a final report and summary of research on Model Atmospheres for Novae in Outburst. Some of the topics include: 1) Detailed NLTE (non-local thermodynamic equilibrium) Model Atmospheres for Novae during Outburst: II. Modeling optical and ultraviolet observations of Nova LMC 1988 #1; 2) A Non-LTE Line-Blanketed Stellar Atmosphere Model of the Early B Giant epsilon CMa; 3) Spectroscopy of Low Metallicity Stellar atmospheres; 4) Infrared Colors at the Stellar/Substellar Boundary; 5) On the abundance of Lithium in T CrB; 6) Numerical Solution of the Expanding Stellar Atmosphere Problem; and 7) The NextGen Model Atmosphere grid for 3000 less than or equal to T (sub eff) less than or equal to 10000K.

Models of very-low-mass stars, brown dwarfs and exoplanets.

PubMed

Allard, F; Homeier, D; Freytag, B

2012-06-13

Within the next few years, GAIA and several instruments aiming to image extrasolar planets will be ready. In parallel, low-mass planets are being sought around red dwarfs, which offer more favourable conditions, for both radial velocity detection and transit studies, than solar-type stars. In this paper, the authors of a model atmosphere code that has allowed the detection of water vapour in the atmosphere of hot Jupiters review recent advances in modelling the stellar to substellar transition. The revised solar oxygen abundances and cloud model allow the photometric and spectroscopic properties of this transition to be reproduced for the first time. Also presented are highlight results of a model atmosphere grid for stars, brown dwarfs and extrasolar planets.

DORSAL HIPPOCAMPAL PROGESTERONE INFUSIONS ENHANCE OBJECT RECOGNITION IN YOUNG FEMALE MICE

PubMed Central

Orr, Patrick T.; Lewis, Michael C.; Frick, Karyn M.

2009-01-01

The effects of progesterone on memory are not nearly as well studied as the effects of estrogens. Although progesterone can reportedly enhance spatial and/or object recognition in female rodents when given immediately after training, previous studies have injected progesterone systemically, and therefore, the brain regions mediating this enhancement are not clear. As such, this study was designed to determine the role of the dorsal hippocampus in mediating the beneficial effect of progesterone on object recognition. Young ovariectomized C57BL/6 mice were trained in a hippocampal-dependent object recognition task utilizing two identical objects, and then immediately or 2 hrs afterwards, received bilateral dorsal hippocampal infusions of vehicle or 0.01, 0.1, or 1.0 μg/μl water-soluble progesterone. Forty-eight hours later, object recognition memory was tested using a previously explored object and a novel object. Relative to the vehicle group, memory for the familiar object was enhanced in all groups receiving immediate infusions of progesterone. Progesterone infusion delayed 2 hrs after training did not affect object recognition. These data suggest that the dorsal hippocampus may play a critical role in progesterone-induced enhancement of object recognition. PMID:19477194

Assessing the Math Performance of Young ESL Students.

ERIC Educational Resources Information Center

Lee, Fong Yun; Silverman, Fredrick L.; Montoya, Patricia

2002-01-01

Describes proven assessment strategies, which, used separately or in combination, can help young ESL students express their understanding of math concepts while building their English-language skills: Manipulative objects, diagrams, and physical movement. Also describes other assessment techniques including self-assessment, interviewing, and…

IRAC Photometry of the Coldest CatWISE-selected Brown Dwarfs

NASA Astrophysics Data System (ADS)

Meisner, Aaron; Kirkpatrick, J. Davy; Kirkpatrick, J. Davy; Eisenhardt, Peter; Marocco, Federico; Faherty, Jacqueline; Cushing, Michael; Wright, Edward

2018-05-01

We will obtain IRAC [3.6] and [4.5] photometry of 250 extremely cool brown dwarfs newly revealed by the powerful combination of WISE and NEOWISE imaging at 4.6 microns. Our CatWISE effort, which is an archival data analysis program using WISE and NEOWISE data, will improve upon the motion selection of AllWISE by enabling a >10x time baseline enhancement, from 0.5 years (AllWISE) to 6.5 years (CatWISE). As a result, CatWISE motion selection is expected to yield a dramatic 8-fold increase in the sample of known brown dwarfs at spectral types T5 and later (T < 1,200 K). Many of the coolest such CatWISE discoveries will be detected exclusively in the WISE 4.6 micron (W2) channel. WISE W1 (3.4 micron) nondetections, which we expect for the majority of our most interesting sources, will provide only limits on mid-infrared color. Spitzer can supply this critical datum by measuring accurate [3.6]-[4.5] colors of our discoveries. These Spitzer color measurements will permit photometric spectral type estimates, which in turn yield estimates for critical parameters including luminosity, distance, and near-infrared flux. Using large [3.6]-[4.5] color to pinpoint the coldest late T and Y dwarfs among our CatWISE sample will enable us to prioritize these objects for spectroscopic follow-up, better understand the bottom of the substellar mass function, and identify nearby giant planet analogs suitable for future atmospheric studies with JWST.

Searching for Faint Companions to Nearby Stars with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Schroeder, Daniel J.; Golimowski, David A.

1996-01-01

A search for faint companions (FC's) to selected stars within 5 pc of the Sun using the Hubble Space Telescope's Planetary Camera (PC) has been initiated. To assess the PC's ability to detect FCs, we have constructed both model and laboratory-simulated images and compared them to actual PC images. We find that the PC's point-spread function (PSF) is 3-4 times brighter over the angular range 2-5 sec than the PSF expected for a perfect optical system. Azimuthal variations of the PC's PSF are 10-20 times larger than expected for a perfect PSF. These variations suggest that light is scattered nonuniformly from the surface of the detector. Because the anomalies in the PC's PSF cannot be precisely simulated, subtracting a reference PSF from the PC image is problematic. We have developed a computer algorithm that identifies local brightness anomalies within the PSF as potential FCs. We find that this search algorithm will successfully locate FCs anywhere within the circumstellar field provided that the average pixel signal from the FC is at least 10 sigma above the local background. This detection limit suggests that a comprehensive search for extrasolar Jovian planets with the PC is impractical. However, the PC is useful for detecting other types of substellar objects. With a stellar signal of 10(exp 9) e(-), for example, we may detect brown dwarfs as faint as M(sub I) = 16.7 separated by 1 sec from alpha Cen A.

ExoMol line lists - VII. The rotation-vibration spectrum of phosphine up to 1500 K

NASA Astrophysics Data System (ADS)

Sousa-Silva, Clara; Al-Refaie, Ahmed F.; Tennyson, Jonathan; Yurchenko, Sergei N.

2015-01-01

A comprehensive hot line list is calculated for 31PH3 in its ground electronic state. This line list, called SAlTY, contains almost 16.8 billion transitions between 7.5 million energy levels and it is suitable for simulating spectra up to temperatures of 1500 K. It covers wavelengths longer than 1 μm and includes all transitions to upper states with energies below hc × 18 000 cm-1 and rotational excitation up to J = 46. The line list is computed by variational solution of the Schrödinger equation for the rotation-vibration motion employing the nuclear-motion program TROVE. A previously reported ab initio dipole moment surface is used as well as an updated `spectroscopic' potential energy surface, obtained by refining an existing ab initio surface through least-squares fitting to the experimentally derived energies. Detailed comparisons with other available sources of phosphine transitions confirms SAlTY's accuracy and illustrates the incompleteness of previous experimental and theoretical compilations for temperatures above 300 K. Atmospheric models are expected to severely underestimate the abundance of phosphine in disequilibrium environments, and it is predicted that phosphine will be detectable in the upper troposphere of many substellar objects. This list is suitable for modelling atmospheres of many astrophysical environments, namely carbon stars, Y dwarfs, T dwarfs, hot Jupiters and Solar system gas giant planets. It is available in full from the Strasbourg data centre, CDS, and at www.exomol.com.

VizieR Online Data Catalog: σ Orionis cluster stellar population (Hernandez+, 2014)

NASA Astrophysics Data System (ADS)

Hernandez, J.; Calvet, N.; Perez, A.; Briceno, C.; Olguin, L.; Contreras, M. E.; Hartmann, L.; Allen, L.; Espaillat, C.; Hernan, R.

2017-04-01

We obtained optical photometry (UBVRCIC) of the center on 2011 December 24 using the Ohio State Multi-Object Spectrograph (OSMOS) on the MDM 2.4 m Hiltner telescope (Stoll et al. 2010SPIE.7735E..4LS; Martini et al. 2011PASP..123..187M). We obtained two sets of images, one short exposure set (20, 15, 10, 5, and 5 s for U, B, V, RC and IC, respectively) and one long exposures set (3x200, 3x200, 3x150, 3x100, and 3x100 s for U, B, V, RC, and IC, respectively). The initial sample in this study includes all Two Micron All Sky Survey (2MASS) sources (4659 sources; Cutri et al. 2003yCat.2246....0C) in a region of 48'x48' centered at RA=84.7° and DE=-2.6°. This region covers the field studied in H07b (Hernandez et al. 2007, J/ApJ/662/1067) using the four channels of the InfraRed Array Camera (IRAC; Fazio et al. 2004ApJS..154...39F). The 2MASS catalog (Cutri et al. 2003yCat.2246....0C, Cat.II/246) is complete down to J<15.8, which includes stars beyond the substellar limit expected for the σ Orionis cluster (e.g., J~14.6; Hernandez et al. 2007, J/ApJ/662/1067). (8 data files).

A CHEMICAL KINETICS NETWORK FOR LIGHTNING AND LIFE IN PLANETARY ATMOSPHERES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rimmer, P. B.; Helling, Ch, E-mail: pr33@st-andrews.ac.uk

2016-05-01

There are many open questions about prebiotic chemistry in both planetary and exoplanetary environments. The increasing number of known exoplanets and other ultra-cool, substellar objects has propelled the desire to detect life and prebiotic chemistry outside the solar system. We present an ion–neutral chemical network constructed from scratch, Stand2015, that treats hydrogen, nitrogen, carbon, and oxygen chemistry accurately within a temperature range between 100 and 30,000 K. Formation pathways for glycine and other organic molecules are included. The network is complete up to H6C2N2O3. Stand2015 is successfully tested against atmospheric chemistry models for HD 209458b, Jupiter, and the present-day Earth usingmore » a simple one-dimensional photochemistry/diffusion code. Our results for the early Earth agree with those of Kasting for CO{sub 2}, H{sub 2}, CO, and O{sub 2}, but do not agree for water and atomic oxygen. We use the network to simulate an experiment where varied chemical initial conditions are irradiated by UV light. The result from our simulation is that more glycine is produced when more ammonia and methane is present. Very little glycine is produced in the absence of any molecular nitrogen and oxygen. This suggests that the production of glycine is inhibited if a gas is too strongly reducing. Possible applications and limitations of the chemical kinetics network are also discussed.« less

Young Infants' Expectations about Hidden Objects

ERIC Educational Resources Information Center

Ruffman, Ted; Slade, Lance; Redman, Jessica

2005-01-01

Infants aged 3-5 months (mean of approximately 4 months) were given a novel anticipatory looking task to test object permanence understanding. They were trained to expect an experimenter to retrieve an object from behind a transparent screen upon hearing a cue (''Doors up, here comes the hand''). The experimenter then hid the object behind one of…

Second Community Pilot Project Programme: Transition of Young People from School to Adult and Working Life: Results and Prospects. Dossier.

ERIC Educational Resources Information Center

Eurydice News, 1987

1987-01-01

During 1983-87 the Commission of the European Communities helped fund 30 pilot projects that were intended to help young people aged 14-18 make the transition from school to work in 10 member states. The objective of these projects was to use local initiative to identify and develop innovative solutions to the problems facing young people. The…

Academic Careers and Post-College Employment of Young Men. Final Report.

ERIC Educational Resources Information Center

Miller, Herman P.; Garfinkle, Stuart

This study of career goals, academic objectives and the relation of these to success in the job market involved a series of annual interviews with samples of people representing four different population groups: young men who were 14 to 24 years old in 1966; men who were 45 to 59 years old in 1966; young women who were 14 to 24 years old in 1968;…

Racial/Ethnic Differences in HIV-Related Knowledge among Young Men Who Have Sex with Men and Their Association with Condom Errors

ERIC Educational Resources Information Center

Garofalo, Robert; Gayles, Travis; Bottone, Paul Devine; Ryan, Dan; Kuhns, Lisa M.; Mustanski, Brian

2015-01-01

Objective: HIV disproportionately affects young men who have sex with men, and knowledge about HIV transmission is one factor that may play a role in high rate of infections for this population. This study examined racial/ethnic differences in HIV knowledge among young men who have sex with men in the USA and their correlation to condom usage…

"I Think Boys Would Rather Be Alpha Male": Being Male and Sexual Health Experiences of Young Men from a Deprived Area in the UK

ERIC Educational Resources Information Center

Watkins, F.; Bristow, K.; Robertson, S.; Norman, R.; Litva, A.; Stanistreet, D.

2013-01-01

Objective: To explore the experiences of young men aged 16-19, living in an area of high deprivation, when accessing local sexual health services. Design: A qualitative design drawing on ethnographic methods. Setting: A local college. Methods: A multi-method approach was adopted using: one-to-one semi-structured interviews with young men and…

Employing Machine-Learning Methods to Study Young Stellar Objects

NASA Astrophysics Data System (ADS)

Moore, Nicholas

2018-01-01

Vast amounts of data exist in the astronomical data archives, and yet a large number of sources remain unclassified. We developed a multi-wavelength pipeline to classify infrared sources. The pipeline uses supervised machine learning methods to classify objects into the appropriate categories. The program is fed data that is already classified to train it, and is then applied to unknown catalogues. The primary use for such a pipeline is the rapid classification and cataloging of data that would take a much longer time to classify otherwise. While our primary goal is to study young stellar objects (YSOs), the applications extend beyond the scope of this project. We present preliminary results from our analysis and discuss future applications.

Learning What to Remember: Vocabulary Knowledge and Children's Memory for Object Names and Features

ERIC Educational Resources Information Center

Perry, Lynn K.; Axelsson, Emma L.; Horst, Jessica S.

2016-01-01

Although young children can map a novel name to a novel object, it remains unclear what they actually remember about objects when they initially make such a name-object association. In the current study we investigated (1) what children remembered after they were initially introduced to name-object associations and (2) how their vocabulary size…

The influence of familiar characters and other appealing images on young children's preference for low-quality objects.

PubMed

Danovitch, Judith H; Mills, Candice M

2017-09-01

This study examines the factors underlying young children's preference for products bearing a familiar character's image. Three-year-olds (N = 92) chose between low-quality objects with images on or near the objects and high-quality objects without images. Children showed stronger preferences for damaged objects bearing images of a preferred familiar character than for objects bearing images of a preferred colour star, and they showed weak preferences for damaged objects with the character near, but not on, the object. The results suggest that children's preference for low-quality products bearing character images is driven by prior exposure to characters, and not only by the act of identifying a favourite. Statement of contribution What is already known on this subject? Children are exposed to characters in the media and on products such as clothing and school supplies. Products featuring familiar characters appeal to preschool children, even if they are of low quality. What does this study add? Three-year-olds prefer damaged objects with an image of a favourite character over plain undamaged objects. Children's preference is not solely a function of having identified a favourite image or of attentional cues. © 2017 The British Psychological Society.

Fossil Explorers

ERIC Educational Resources Information Center

Moran, Sean; McLaughlin, Cheryl; MacFadden, Bruce; Jacobbe, Elizabeth; Poole, Michael

2015-01-01

Many young learners are fascinated with fossils, particularly charismatic forms such as dinosaurs and giant sharks. Fossils provide tangible, objective evidence of life that lived millions of years ago. They also provide a timescale of evolution not typically appreciated by young learners. Fossils and the science of paleontology can, therefore,…

YSOVAR: MID-INFRARED VARIABILITY OF YOUNG STELLAR OBJECTS AND THEIR DISKS IN THE CLUSTER IRAS 20050+2720

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poppenhaeger, K.; Wolk, S. J.; Hora, J. L.

2015-10-15

We present a time-variability study of young stellar objects (YSOs) in the cluster IRAS 20050+2720, performed at 3.6 and 4.5 μm with the Spitzer Space Telescope; this study is part of the Young Stellar Object VARiability (YSOVAR) project. We have collected light curves for 181 cluster members over 60 days. We find a high variability fraction among embedded cluster members of ca. 70%, whereas young stars without a detectable disk display variability less often (in ca. 50% of the cases) and with lower amplitudes. We detect periodic variability for 33 sources with periods primarily in the range of 2–6 days.more » Practically all embedded periodic sources display additional variability on top of their periodicity. Furthermore, we analyze the slopes of the tracks that our sources span in the color–magnitude diagram (CMD). We find that sources with long variability time scales tend to display CMD slopes that are at least partially influenced by accretion processes, while sources with short variability timescales tend to display extinction-dominated slopes. We find a tentative trend of X-ray detected cluster members to vary on longer timescales than the X-ray undetected members.« less

KINEMATICS OF STELLAR POPULATIONS IN POSTSTARBURST GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiner, Kyle D.; Canalizo, Gabriela, E-mail: gabriela.canalizo@ucr.edu, E-mail: khiner@astro-udec.cl

2015-01-20

Poststarburst galaxies host a population of early-type stars (A or F) but simultaneously lack indicators of ongoing star formation such as [O II] emission. Two distinct stellar populations have been identified in these systems: a young poststarburst population superimposed on an older host population. We present a study of nine poststarburst galaxies with the following objectives: (1) to investigate whether and how kinematical differences between the young and old populations of stars can be measured, and (2) to gain insight into the formation mechanism of the young population in these systems. We fit high signal-to-noise spectra with two independent populationsmore » in distinct spectral regions: the Balmer region, the Mg IB region, and the Ca triplet when available. We show that the kinematics of the two populations largely track one another if measured in the Balmer region with high signal-to-noise data. Results from examining the Faber-Jackson relation and the fundamental plane indicate that these objects are not kinematically disturbed relative to more evolved spheroids. A case study of the internal kinematics of one object in our sample shows it to be pressure supported and not rotationally dominated. Overall our results are consistent with merger-induced starburst scenarios where the young population is observed during the later stages of the merger.« less

Hubble Space Telescope Planetary Camera observations of Arp 220

NASA Technical Reports Server (NTRS)

Shaya, Edward J.; Dowling, Daniel M.; Currie, Douglas G.; Faber, S. M.; Groth, Edward J.

1994-01-01

Planetary Camera images of peculiar galaxy Arp 220 taken with V, R, and I band filters reveal a very luminous object near the position of the western radio continuum source, assumed to be the major nucleus, ans seven lesser objects within 2 sec of this position. The most luminous object is formally coincident with the radio source to within the errors of Hubble Space Telescope (HST) pointing accuracy, but we have found an alternate, more compelling alignment of maps in which the eastern radio source coincides with one of the lesser objects and the OH radio sources reside near the surfaces of other optical objects. The proposed centering places the most luminous object 150 pc (0.4 sec) away from the western radio source. We explore the possibilities that the objects are either holes in the dense dust distribution, dusty clouds reflecting a hidden bright nucleus, or associations of bright young stars. We favor the interpretation that at least the brightest two objects are massive young star associations with luminosities 10(exp 9) to 10(exp 11) solar luminosity, but highly extinguished by intervening dust. These massive associations should fall into the nucleus on a time scale of 10(exp 8) yr. About 10% of the enigmatic far-IR flux arises from the observed objects. In addition, if the diffuse starlight out to a radius of 8 sec is dominated by stars with typical ages of order 10(exp 8) yr (the time since the alleged merger of two galaxies), as indicated by the blue colors at larger radius, then the lower limit to the reradiation of diffuse starlight contributes 3 x 10(exp 11) solar luminosity to the far-infrared flux, or greater than or equal to 25% of the total far-IR flux. Three additional bright objects (M(sub V) approximately equals -13) located about 6 sec from the core are likely young globular clusters, but any of these could be recently exploded supernovae instead. The expected supernovae rate, if the dominant energy source is young stars, is about one per month for the region where the intense far-infrared flux originates. Also, individual giant dust clouds are visible in these images. Their typical size is 300 pc (1 sec).

Identification of transitional disks in Chamaeleon with Herschel

NASA Astrophysics Data System (ADS)

Ribas, Á.; Merín, B.; Bouy, H.; Alves de Oliveira, C.; Ardila, D. R.; Puga, E.; Kóspál, Á.; Spezzi, L.; Cox, N. L. J.; Prusti, T.; Pilbratt, G. L.; André, Ph.; Matrà, L.; Vavrek, R.

2013-04-01

Context. Transitional disks are circumstellar disks with inner holes that in some cases are produced by planets and/or substellar companions in these systems. For this reason, these disks are extremely important for the study of planetary system formation. Aims: The Herschel Space Observatory provides an unique opportunity for studying the outer regions of protoplanetary disks. In this work we update previous knowledge on the transitional disks in the Chamaeleon I and II regions with data from the Herschel Gould Belt Survey. Methods: We propose a new method for transitional disk classification based on the WISE 12 μm - PACS 70 μm color, together with inspection of the Herschel images. We applied this method to the population of Class II sources in the Chamaeleon region and studied the spectral energy distributions of the transitional disks in the sample. We also built the median spectral energy distribution of Class II objects in these regions for comparison with transitional disks. Results: The proposed method allows a clear separation of the known transitional disks from the Class II sources. We find six transitional disks, all previously known, and identify five objects previously thought to be transitional as possibly non-transitional. We find higher fluxes at the PACS wavelengths in the sample of transitional disks than those of Class II objects. Conclusions: We show the Herschel 70 μm band to be a robust and efficient tool for transitional disk identification. The sensitivity and spatial resolution of Herschel reveals a significant contamination level among the previously identified transitional disk candidates for the two regions, which calls for a revision of previous samples of transitional disks in other regions. The systematic excess found at the PACS bands could be either a result of the mechanism that produces the transitional phase, or an indication of different evolutionary paths for transitional disks and Class II sources. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix A is available in electronic form at http://www.aanda.org

Beyond the T Dwarfs: Theoretical Spectra, Colors, and Detectability of the Coolest Brown Dwarfs

NASA Astrophysics Data System (ADS)

Burrows, Adam; Sudarsky, David; Lunine, Jonathan I.

2003-10-01

We explore the spectral and atmospheric properties of brown dwarfs cooler than the latest known T dwarfs. Our focus is on the yet-to-be-discovered free-floating brown dwarfs in the Teff range from ~800 to ~130 K and with masses from 25 to 1 MJ. This study is in anticipation of the new characterization capabilities enabled by the launch of the Space Infrared Telescope Facility (SIRTF) and the eventual launch of the James Webb Space Telescope (JWST). In addition, it is in support of the continuing ground-based searches for the coolest substellar objects. We provide spectra from ~0.4 to 30 μm, highlight the evolution and mass dependence of the dominant H2O, CH4, and NH3 molecular bands, consider the formation and effects of water ice clouds, and compare our theoretical flux densities with the putative sensitivities of the instruments on board SIRTF and JWST. The latter can be used to determine the detection ranges from space of cool brown dwarfs. In the process, we determine the reversal point of the blueward trend in the near-infrared colors with decreasing Teff (a prominent feature of the hotter T dwarf family), the Teff's at which water and ammonia clouds appear, the strengths of gas-phase ammonia and methane bands, the masses and ages of the objects for which the neutral alkali metal lines (signatures of L and T dwarfs) are muted, and the increasing role as Teff decreases of the mid-infrared fluxes longward of 4 μm. These changes suggest physical reasons to expect the emergence of at least one new stellar class beyond the T dwarfs. Furthermore, studies in the mid-infrared could assume a new, perhaps transformational, importance in the understanding of the coolest brown dwarfs. Our spectral models populate, with cooler brown dwarfs having progressively more planet-like features, the theoretical gap between the known T dwarfs and the known giant planets. Such objects likely inhabit the Galaxy, but their numbers are as yet unknown.

VizieR Online Data Catalog: Catalog of Suspected Nearby Young Stars (Riedel+, 2017)

NASA Astrophysics Data System (ADS)

Riedel, A. R.; Blunt, S. C.; Lambrides, E. L.; Rice, E. L.; Cruz, K. L.; Faherty, J. K.

2018-04-01

LocAting Constituent mEmbers In Nearby Groups (LACEwING) is a frequentist observation space kinematic moving group identification code. Using the spatial and kinematic information available about a target object (α, δ, Dist, μα, μδ, and γ), it determines the probability that the object is a member of each of the known nearby young moving groups (NYMGs). As with other moving group identification codes, LACEwING is capable of estimating memberships for stars with incomplete kinematic and spatial information. (2 data files).

Observations of Young Stellar Objects with Infrared Interferometry: Recent Results from PTI, KI and IOTA

NASA Astrophysics Data System (ADS)

Akeson, Rachel

Young stellar objects have been one of the favorite targets of infrared interferometers for many years. In this contribution I will briefly review some of the first results and their contributions to the field and then describe some of the recent results from the Keck Interferometer (KI), the Palomar Testbed Interferometer (PTI) and the Infrared-Optical Telescope Array (IOTA). This conference also saw many exciting new results from the VLTI at both near and mid-infrared wavelengths that are covered by other contributions.

Increased objectively assessed vigorous-intensity exercise is associated with reduced stress, increased mental health and good objective and subjective sleep in young adults.

PubMed

Gerber, Markus; Brand, Serge; Herrmann, Christian; Colledge, Flora; Holsboer-Trachsler, Edith; Pühse, Uwe

2014-08-01

The role of physical activity as a factor that protects against stress-related mental disorders is well documented. Nevertheless, there is still a dearth of research using objective measures of physical activity. The present study examines whether objectively assessed vigorous physical activity (VPA) is associated with mental health benefits beyond moderate physical activity (MPA). Particularly, this study examines whether young adults who accomplish the American College of Sports Medicine's (ACSM) vigorous-intensity exercise recommendations differ from peers below these standards with regard to their level of perceived stress, depressive symptoms, perceived pain, and subjective and objective sleep. A total of 42 undergraduate students (22 women, 20 men; M=21.24years, SD=2.20) volunteered to take part in the study. Stress, pain, depressive symptoms, and subjective sleep were assessed via questionnaire, objective sleep via sleep-EEG assessment, and VPA via actigraphy. Meeting VPA recommendations had mental health benefits beyond MPA. VPA was associated with less stress, pain, subjective sleep complaints and depressive symptoms. Moreover, vigorous exercisers had more favorable objective sleep pattern. Especially, they had increased total sleep time, more stage 4 and REM sleep, more slow wave sleep and a lower percentage of light sleep. Vigorous exercisers also reported fewer mental health problems if exposed to high stress. This study provides evidence that meeting the VPA standards of the ACSM is associated with improved mental health and more successful coping among young people, even compared to those who are meeting or exceeding the requirements for MPA. Copyright © 2014 Elsevier Inc. All rights reserved.

Children's Exploration of Physical Phenomena during Object Play

ERIC Educational Resources Information Center

Solis, S. Lynneth; Curtis, Kaley N.; Hayes-Messinger, Amani

2017-01-01

Researchers propose that experiencing and manipulating physical principles through objects allows young children to formulate scientific intuitions that may serve as precursors to learning in STEM subjects. This may be especially true when children discover these physical principles through object affordances during play. The present study…

Food preparation by young adults is associated with better diet quality.

PubMed

Larson, Nicole I; Perry, Cheryl L; Story, Mary; Neumark-Sztainer, Dianne

2006-12-01

To describe food-preparation behaviors, cooking skills, resources for preparing food, and associations with diet quality among young adults. Cross-sectional analyses were performed in a sample of young adults who responded to the second wave of a population-based longitudinal study. Measures pertaining to food preparation were self-reported and dietary intake was assessed by a food frequency questionnaire, both by a mailed survey. Males (n = 764) and females (n = 946) ages 18 to 23 years. Cross-tabulations and chi2 tests were used to examine associations between food preparation, skills/resources for preparing foods, and characteristics of young adults. Mixed regression models were used to generate expected probabilities of meeting the Healthy People 2010 dietary objectives according to reported behaviors and skills/resources. Food-preparation behaviors were not performed by the majority of young adults even weekly. Sex (male), race (African American), and living situation (campus housing) were significantly related to less frequent food preparation. Lower perceived adequacy of skills and resources for food preparation was related to reported race (African American or Hispanic) and student status (part-time or not in school). The most common barrier to food preparation was lack of time, reported by 36% of young adults. Young adults who reported frequent food preparation reported less frequent fast-food use and were more likely to meet dietary objectives for fat (P < 0.001), calcium (P < 0.001), fruit (P < 0.001), vegetable (P < 0.001), and whole-grain (P = 0.003) consumption. To improve dietary intake, interventions among young adults should teach skills for preparing quick and healthful meals.

State-by-State Variation in the Number of Children and Young Adults in Nursing Homes, 2005-2012.

PubMed

Jin, Evan; Agrawal, Rishi

2017-12-01

Objectives One goal of Healthy People 2020 is to reduce the number of children and young adults living in nursing homes. However, little is known about the prevalence of nursing home use among children and young adults on a state-by-state basis. The objective of this study was to determine the prevalence of nursing home use among children and young adults in each state from 2005 to 2012. The study also looked for prevalence trends between 2005 and 2012. Methods The Centers for Medicare and Medicaid Services Minimum Data Set and US Census data were used to calculate the prevalence of nursing home residents among children and young adults aged 0-30 in each US state in 2012 and assess trends in each state from 2005 to 2012. Results In 2012, the prevalence of nursing home residents among children and young adults aged 0-30 varied across states, ranging from 14 in 100,000 (New Jersey) to 0.8 in 100,000 (Alaska). Testing for trends from 2005 to 2012 also revealed significant trends (p < 0.05), with Florida trending upward with borderline statistical significance (p = 0.05) and six states trending downward. Conclusion There is wide variation in the prevalence of nursing home residents among children and young adults aged 0-30 across states. There is also variation in the nursing home prevalence trends across states. Observed variations may represent potential opportunities for some states to reduce their population of children and young adults in nursing homes.

Eclipsing binaries and fast rotators in the Kepler sample. Characterization via radial velocity analysis from Calar Alto

NASA Astrophysics Data System (ADS)

Lillo-Box, J.; Barrado, D.; Mancini, L.; Henning, Th.; Figueira, P.; Ciceri, S.; Santos, N.

2015-04-01

Context. The Kepler mission has searched for planetary transits in more than two hundred thousand stars by obtaining very accurate photometric data over a long period of time. Among the thousands of detected candidates, the planetary nature of around 15% has been established or validated by different techniques. But additional data are needed to characterize the rest of the candidates and reject other possible configurations. Aims: We started a follow-up program to validate, confirm, and characterize some of the planet candidates. In this paper we present the radial velocity analysis of those that present large variations, which are compatible with being eclipsing binaries. We also study those showing high rotational velocities, which prevents us from reaching the necessary precision to detect planetary-like objects. Methods: We present new radial velocity results for 13 Kepler objects of interest (KOIs) obtained with the CAFE spectrograph at the Calar Alto Observatory and analyze their high-spatial resolution (lucky) images obtained with AstraLux and the Kepler light curves of some interesting cases. Results: We have found five spectroscopic and eclipsing binaries (group A). Among them, the case of KOI-3853 is of particular interest. This system is a new example of the so-called heartbeat stars, showing dynamic tidal distortions in the Kepler light curve. We have also detected duration and depth variations of the eclipse. We suggest possible scenarios to explain such an effect, including the presence of a third substellar body possibly detected in our radial velocity analysis. We also provide upper mass limits to the transiting companions of six other KOIs with high rotational velocities (group B). This property prevents the radial velocity method from achieving the necessary precision to detect planetary-like masses. Finally, we analyze the large radial velocity variations of two other KOIs, which are incompatible with the presence of planetary-mass objects (group C).These objects are likely to be stellar binaries. However, a longer timespan is needed to complete their characterization. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck Institut fur Astronomie (Heidelberg) and the Instituto de Astrofísica de Andalucía (IAA-CSIC, Granada).Appendix A is available in electronic form at http://www.aanda.org

Direct imaging of an ultracool substellar companion to the exoplanet host star HD 4113 A

NASA Astrophysics Data System (ADS)

Cheetham, A.; Ségransan, D.; Peretti, S.; Delisle, J.-B.; Hagelberg, J.; Beuzit, J.-L.; Forveille, T.; Marmier, M.; Udry, S.; Wildi, F.

2018-06-01

Using high-contrast imaging with the SPHERE instrument at the Very Large Telescope (VLT), we report the first images of a cold brown dwarf companion to the exoplanet host star HD 4113A. The brown dwarf HD 4113C is part of a complex dynamical system consisting of a giant planet, a stellar host, and a known wide M-dwarf companion. Its separation of 535 ± 3 mas and H-band contrast of 13.35 ± 0.10 mag correspond to a projected separation of 22 AU and an isochronal mass estimate of 36 ± 5 MJ based on COND models. The companion shows strong methane absorption, and through fitting an atmosphere model, we estimate a surface gravity of logg = 5 and an effective temperature of 500-600 K. A comparison of its spectrum with observed T dwarfs indicates a late-T spectral type, with a T9 object providing the best match. By combining the observed astrometry from the imaging data with 27 years of radial velocities, we use orbital fitting to constrain its orbital and physical parameters, as well as update those of the planet HD 4113A b, discovered by previous radial velocity measurements. The data suggest a dynamical mass of 66-4+5 MJ and moderate eccentricity of 0.44-0.07+0.08 for the brown dwarf. This mass estimate appears to contradict the isochronal estimate and that of objects with similar temperatures, which may be caused by the newly detected object being an unresolved binary brown dwarf system or the presence of an additional object in the system. Through dynamical simulations, we show that the planet may undergo strong Lidov-Kozai cycles, raising the possibility that it formed on a quasi-circular orbit and gained its currently observed high eccentricity (e 0.9) through interactions with the brown dwarf. Follow-up observations combining radial velocities, direct imaging, and Gaia astrometry will be crucial to precisely constrain the dynamical mass of the brown dwarf and allow for an in-depth comparison with evolutionary and atmosphere models. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 097.C-0893(A), 077.C-0293(A), 279.C-5052(A), 081.C-0653(A) and 091.C-0721(B).

Cognitive impairment and medial temporal lobe structure in young adults with a depressive episode.

PubMed

Donix, Markus; Haussmann, Robert; Helling, Franziska; Zweiniger, Anne; Lange, Jan; Werner, Annett; Donix, Katharina L; Brandt, Moritz D; Linn, Jennifer; Bauer, Michael; Buthut, Maria

2018-09-01

Cognitive deficits are common in patients with a depressive episode although the predictors for their development and severity remain elusive. We investigated whether subjective and objective cognitive impairment in young depressed adults would be associated with cortical thinning in medial temporal subregions. High-resolution magnetic resonance imaging, cortical unfolding data analysis, and comprehensive assessments of subjective and objective cognitive abilities were performed on 27 young patients with a depressive episode (mean age: 29.0 ± 5.8 years) and 23 older participants without a history of a depressive disorder but amnestic mild cognitive impairment (68.5 ± 6.6 years) or normal cognition (65.2 ± 8.7 years). Thickness reductions in parahippocampal, perirhinal and fusiform cortices were associated with subjective memory deficits only among young patients with a depressive episode and a measurable cognitive impairment. Long-term longitudinal data would be desirable to determine the trajectories of cognitive impairment associated with depression in patients with or without cortical structure changes. The presence of clinically significant cognitive deficits in young people with a depressive episode may identify a patient population with extrahippocampal cortical thinning. Copyright © 2018 Elsevier B.V. All rights reserved.

Does everything happen when you are young? Introducing the youth bias.

PubMed

Koppel, Jonathan; Berntsen, Dorthe

2014-01-01

The reminiscence bump refers to the disproportionate number of individuals' autobiographical memories that date from young adulthood. A similar bump is found in cultural life scripts: When people are asked to nominate and date major transitional events in a typical life course in their culture, a disproportionate number of the events cited are likewise expected to occur in young adulthood. Across two online studies, we tested whether these effects reflect a broader tendency to ascribe most important events to young adulthood. Specifically, we probed, in adult USA samples, for when individuals expect the most important public event of a typical person's life to take place. Although the occurrence of such public events should be randomly distributed across the lifespan, we found a bump in young adulthood. We found this bump in both subjective (Study 1; probing cultural expectations for the expected timing of the public event that a typical person considers to be the most important of their lifetime) and objective (Study 2; probing cultural expectations for the expected timing of the objectively most important public event of a typical person's lifetime) conditions. We term this set of cultural expectations the youth bias and discuss its implications for human cognition.

Upper limb motor function in young adults with spina bifida and hydrocephalus

PubMed Central

Salman, M. S.; Jewell, D.; Hetherington, R.; Spiegler, B. J.; MacGregor, D. L.; Drake, J. M.; Humphreys, R. P.; Gentili, F.

2011-01-01

Objective The objective of the study was to measure upper limb motor function in young adults with spina bifida meningomyelocele (SBM) and typically developing age peers. Method Participants were 26 young adults with SBM, with a Verbal or Performance IQ score of at least 70 on the Wechsler scales, and 27 age- and gender-matched controls. Four upper limb motor function tasks were performed under four different visual and cognitive challenge conditions. Motor independence was assessed by questionnaire. Results Fewer SBM than control participants obtained perfect posture and rebound scores. The SBM group performed less accurately and was more disrupted by cognitive challenge than controls on limb dysmetria tasks. The SBM group was slower than controls on the diadochokinesis task. Adaptive motor independence was related to one upper limb motor task, arm posture, and upper rather than lower spinal lesions were associated with less motor independence. Conclusions Young adults with SBM have significant limitations in upper limb function and are more disrupted by some challenges while performing upper limb motor tasks. Within the group of young adults with SBM, upper spinal lesions compromise motor independence more than lower spinal lesions. PMID:19672605

Sensitivity to Relational Similarity and Object Similarity in Apes and Children.

PubMed

Christie, Stella; Gentner, Dedre; Call, Josep; Haun, Daniel Benjamin Moritz

2016-02-22

Relational reasoning is a hallmark of sophisticated cognition in humans. Does it exist in other primates? Despite some affirmative answers, there appears to be a wide gap in relational ability between humans and other primates--even other apes. Here, we test one possible explanation for this gap, motivated by developmental research showing that young humans often fail at relational reasoning tasks because they focus on objects instead of relations. When asked, "duck:duckling is like tiger:?," preschool children choose another duckling (object match) rather than a cub. If other apes share this focus on concrete objects, it could undermine their relational reasoning in similar ways. To test this, we compared great apes and 3-year-old humans' relational reasoning on the same spatial mapping task, with and without competing object matches. Without competing object matches, both children and Pan species (chimpanzees and bonobos) spontaneously used relational similarity, albeit children more so. But when object matches were present, only children responded strongly to them. We conclude that the relational gap is not due to great apes' preference for concrete objects. In fact, young humans show greater object focus than nonhuman apes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of age-related macular degeneration on object searches in realistic panoramic scenes.

PubMed

Thibaut, Miguel; Tran, Thi-Ha-Chau; Szaffarczyk, Sebastien; Boucart, Muriel

2018-05-01

This study investigated whether realistic immersive conditions with dynamic indoor scenes presented on a large, hemispheric panoramic screen covering 180° of the visual field improved the visual search abilities of participants with age-related macular degeneration (AMD). Twenty-one participants with AMD, 16 age-matched controls and 16 young observers were included. Realistic indoor scenes were presented on a panoramic five metre diameter screen. Twelve different objects were used as targets. The participants were asked to search for a target object, shown on paper before each trial, within a room composed of various objects. A joystick was used for navigation within the scene views. A target object was present in 24 trials and absent in 24 trials. The percentage of correct detection of the target, the percentage of false alarms (that is, the detection of the target when it was absent), the number of scene views explored and the search time were measured. The search time was slower for participants with AMD than for the age-matched controls, who in turn were slower than the young participants. The participants with AMD were able to accomplish the task with a performance of 75 per cent correct detections. This was slightly lower than older controls (79.2 per cent) while young controls were at ceiling (91.7 per cent). Errors were mainly due to false alarms resulting from confusion between the target object and another object present in the scene in the target-absent trials. The outcomes of the present study indicate that, under realistic conditions, although slower than age-matched, normally sighted controls, participants with AMD were able to accomplish visual searches of objects with high accuracy. © 2017 Optometry Australia.

The Human First Hypothesis: Identification of Conspecifics and Individuation of Objects in the Young Infant

ERIC Educational Resources Information Center

Bonatti, Luca; Frot, Emmanuel; Zangl, Renate; Mehler, Jacques

2002-01-01

How do infants individuate and track objects, and among them objects belonging to their species, when they can only rely on information about the properties of those objects? We propose the Human First Hypothesis (HFH), which posits that infants possess information about their conspecifics and use it to identify and count objects. F. Xu and S.…

Children's Use of Objects in an Early Years Playground

ERIC Educational Resources Information Center

Bateman, Amanda; Church, Amelia

2017-01-01

Early childhood research has investigated children's use of objects largely focusing on cognitive and motor development. Yet members of a particular culture, such as young children's peer groups, use objects that have cultural relevance as "conversational" items, as a means to interacting with other members of the group. This article…

Preschoolers' Preparation for Retrieval in Object Relocation Tasks.

ERIC Educational Resources Information Center

Beal, Carole R.; Fleisig, Wayne E.

The finding that young children do not prepare markers to help themselves relocate objects after a delay may have resulted from children's misunderstanding of the difficulty of unassisted retrieval. This study examined children's ability to recognize that they should prepare markers in two simplified object relocation tasks after they had been…

Ape Metaphysics: Object Individuation without Language

ERIC Educational Resources Information Center

Mendes, Natacha; Rakoczy, Hannes; Call, Josep

2008-01-01

Developmental research suggests that whereas very young infants individuate objects purely on spatiotemporal grounds, from (at latest) around 1 year of age children are capable of individuating objects according to the kind they belong to and the properties they instantiate. As the latter ability has been found to correlate with language, some…

A motivation-based explanatory model of street drinking among young people.

PubMed

Martín-Santana, Josefa D; Beerli-Palacio, Asunción; Fernández-Monroy, Margarita

2014-01-01

This social marketing study focuses on street drinking behavior among young people. The objective is to divide the market of young people who engage in this activity into segments according to their motivations. For the three segments identified, a behavior model is created using the beliefs, attitudes, behavior, and social belonging of young people who engage in street drinking. The methodology used individual questionnaires filled in by a representative sample of young people. The results show that the behavior model follows the sequence of attitudes-beliefs-behavior and that social belonging influences these three variables. Similarly, differences are observed in the behavior model depending on the segment individuals belong to.

Function of eye coloration in North American accipiters

USGS Publications Warehouse

Snyder, N.F.R.; Snyder, H.A.

1974-01-01

Young nestling Cooper?s Hawks peck vigorously at red objects but do not peck at yellow objects. The significance of this response is discussed in relation to developmental changes in iris coloration in adult hawks.

Development of Morphological Awareness in Young Chinese Readers: Comparing Poor Comprehenders and Good Comprehenders

ERIC Educational Resources Information Center

Zhang, Haomin

2017-01-01

The present study explored the relationship between reading comprehension skill and morphological awareness among young Chinese readers. The objectives were to investigate whether morphological awareness is a critical cognitive and linguistic ability to differentiate poor comprehenders and good comprehenders and to further scrutinize the…

Professional Involvement: Requirements as Students and Trends after Certification

ERIC Educational Resources Information Center

Lancaster, Jennifer N.; Myers, Bettye; Nichols, David L.; Webb, Kerry S.

2014-01-01

Context: The field of athletic training needs young engaged professionals for continued progress in allied health care. Academic and clinical requirements during the entry-level education could potentially impact the decisions and directions these students choose to pursue as young professionals. Objective: To determine the difference in…

Educational Management within a Young Offender Institution.

ERIC Educational Resources Information Center

Fryer, Winny; Fryer, Paul

1992-01-01

Examines educational theory and objectives within prisons and relates these to the real-time case study of the Young Offender Institution at Whatton, in Nottinghamshire, England. Measuring success and cost effectiveness is extremely difficult in the prison education field, and a significant gap exists between the theoretical model and everyday…

Using Alcohol to Sell Cigarettes to Young Adults: A Content Analysis of Cigarette Advertisements

ERIC Educational Resources Information Center

Belstock, Sarah A.; Connolly, Gregory N.; Carpenter, Carrie M.; Tucker, Lindsey

2008-01-01

Objective: Advertising influences the health-related behaviors of college-aged individuals. Cigarette manufacturers aggressively market to young adults and may exploit their affinity for alcohol when creating advertisements designed to increase cigarettes' appeal. Internal tobacco industry documents reveal that cigarette manufacturers understood…

Perceived Effectiveness of Tobacco Countermarketing Advertisements among Young Adults

ERIC Educational Resources Information Center

Murphy-Hoefer, Rebecca; Hyland, Andrew; Higbee, Cheryl

2008-01-01

Objectives: To measure relative effectiveness of tobacco countermarketing advertisements by category and emotive execution style among young adults. Methods: Participants (n = 1011) from 2 US 4-year colleges, one southern and one northern were surveyed before and after viewing advertisements in one of 3 categories: social norms, health…

Music for Engaging Young People in Education

ERIC Educational Resources Information Center

Cheong-Clinch, Carmen

2009-01-01

Two music programs were developed specifically to meet therapeutic objectives for newly arrived immigrant and refugee students and for adolescent boys in a residential care facility. The author's observations justify further research to establish whether music can support and nurture the social, physical and mental wellbeing of young people,…

Young Children as Curators

ERIC Educational Resources Information Center

Hope, Alice

2018-01-01

Literature that addresses young children's learning in galleries and museums typically concentrates on what is already offered and discusses what has proven to be effective, or not, in accommodating their needs. This article offers insight into how objects can be explored with early years children at school, to create greater understanding of…

Is Pubertal Timing Associated with Psychopathology in Young Adulthood?

ERIC Educational Resources Information Center

Graber, Julia A.; Seeley, John R.; Brooks-Gunn, Jeanne; Lewinsohn, Peter M.

2004-01-01

Objective: This investigation tested whether the timing of puberty continued to be associated with experiences of psychopathology (symptoms and disorders) from mid-adolescence into young adulthood. Method: At age 24, 931 participants from a large community sample, who had been interviewed twice during adolescence, completed a telephone interview…

Beliefs and Intentions for Skin Protection and UV Exposure in Young Adults

ERIC Educational Resources Information Center

Heckman, Carolyn J.; Manne, Sharon L.; Kloss, Jacqueline D.; Bass, Sarah Bauerle; Collins, Bradley; Lessin, Stuart R.

2011-01-01

Objective: To evaluate Fishbein's integrative model in predicting young adults' skin protection, sun exposure, and indoor tanning intentions. Methods: Two hundred twelve participants completed an online survey. Results: Damage distress, self-efficacy, and perceived control accounted for 34% of the variance in skin protection intentions. Outcome…

Educational and Skills-Based Interventions to Prevent Relationship Violence in Young People

ERIC Educational Resources Information Center

Fellmeth, Gracia; Heffernan, Catherine; Nurse, Joanna; Habibula, Shakiba; Sethi, Dinesh

2015-01-01

Objectives: To assess the efficacy of educational and skills-based interventions to prevent relationship and dating violence in adolescents and young adults. Methods: We searched Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, PsycINFO, and other databases for randomized, cluster-randomized, and quasi-randomized…

Oculomotor Exploration of Impossible Figures in Early Infancy

ERIC Educational Resources Information Center

Shuwairi, Sarah M.; Johnson, Scott P.

2013-01-01

Previous studies have revealed that young infants can distinguish between displays of possible or impossible figures, which may require detection of inconsistent depth relations among local line junctions that disrupt global object configurations. Here, we used an eye-tracking paradigm to record eye movements in young infants during an object…

Gender Differences in Beliefs about Condom Use among Young, Heterosexual Australian Adults

ERIC Educational Resources Information Center

Newton, Fiona J.; Newton, Joshua D.; Windisch, Lydia; Ewing, Michael T.

2013-01-01

Objective: To investigate gender differences in beliefs about condom use among young, sexually active, heterosexual Australian adults. Design: Cross-sectional survey of 1,113 adults aged 18-26 years. Setting: Higher education institutions across New South Wales and Victoria, Australia. Method: Participants were recruited during higher-education…

Representations of Abstract Grammatical Feature Agreement in Young Children

ERIC Educational Resources Information Center

Melançon, Andréane; Shi, Rushen

2015-01-01

A fundamental question in language acquisition research is whether young children have abstract grammatical representations. We tested this question experimentally. French-learning 30-month-olds were first taught novel word-object pairs in the context of a gender-marked determiner (e.g., un[subscript MASC]ravole "a ravole"). Test trials…

MRI Neuroanatomy in Young Girls with Autism: A Preliminary Study

ERIC Educational Resources Information Center

Bloss, Cinnamon S.; Courchesne, Eric

2007-01-01

Objective: To test the hypothesis that young girls and boys with autism exhibit different profiles of neuroanatomical abnormality relative to each other and relative to typically developing children. Method: Structural magnetic resonance imaging was used to measure gray and white matter volumes (whole cerebrum, cerebral lobes, and cerebellum) and…

Fun with Handwashing Education.

ERIC Educational Resources Information Center

Geiger, Brian F.; Artz, Lynn; Petri, Cynthia J.; Winnail, Scott D.; Mason, J. Walter

Noting that primary prevention of contagious diseases includes teaching young children and their caregivers about personal hygiene behavior, this paper presents a lesson for teaching handwashing to young children in preschool and early elementary grades using a variety of fun and low-cost techniques. The learning objectives for the lesson are that…

The influence of directed attention at encoding on source memory retrieval in the young and old: an ERP study.

PubMed

Dulas, Michael R; Duarte, Audrey

2013-03-15

Neuroimaging evidence suggests that older adults exhibit deficits in frontally-mediated strategic retrieval processes, such as post-retrieval monitoring. Behavioral research suggests that explicitly directing attention toward source features during encoding may improve source memory for both young and older adults and alleviate age-related source memory impairments, in part, by reducing demands on post-retrieval monitoring. We investigated this hypothesis in the present event-related potential (ERP) study. Young and older adults attended to either objects and their presented color (source) or to the object alone during study and made color source memory decisions at test. We attempted to match performance between groups by halving the memory load for older adults. Behavioral results showed that, while direction of attention to object and color improved source memory for both groups, older adults benefited less than the young. ERPs revealed that demands on late right frontal effects, indicative of post-retrieval monitoring, were similarly reduced by directed attention at encoding for both groups. However, older adults showed reduced ERP correlates of recollection (parietal old-new effect), as well as a sustained widespread negativity, potentially indicative of memory searches for perceptual details in the face of impaired recollection. These results suggest that older adults, like the young, can engage in post-retrieval monitoring when source details are difficult to recover. However, impaired recollection may underlie persistent age-related source memory deficits, even when encoding is supported via directed attention. Copyright © 2013 Elsevier B.V. All rights reserved.

Finding High Quality Young Star Candidates in Ceph C using X-ray, Optical, and IR data

NASA Astrophysics Data System (ADS)

Orr, Laura; Rebull, Luisa M.; Johnson, Milton; Miller, Alexandra; Aragon Orozco, Anthony; Bakhaj, Benjamin; Bakshian, Jacquelyn; Chiffelle, Elizabeth; DeLint, Arie; Gerber, Stefan; Mader, Jared; Marengo, Amelia; McAdams, Jesse; Montufar, Cassandra; Orr, Quinton; San Emeterio, Lis; Stern, Eliyah; Weisserman, Drew

2017-01-01

We looked for new candidate young stars within the star forming region of Ceph OB3, more specifically in a region of this molecular cloud called Ceph C. While this region lies in the galactic plane and is included in several large surveys, Ceph C has not been well studied in the past and few young stellar objects (YSOs) have been identified there. The YSOVAR team (Rebull et al. 2014) has time-series monitoring data of this region, and in order to understand the diversity of the light curves, it is crucial to understand which objects in the field of view are likely YSOs, and which are foreground/background objects. The goal of our study is to identify candidate YSO sources as well as support the greater understanding of the variety, evolution, and variability of young stars. Our search for young stars includes data in X-ray, optical, and IR. Data points used are from Chandra, SDSS, IPHAS, 2MASS, Spitzer IRAC and MIPS, and WISE, giving us data over many orders of magnitude, 0.001 to 25 microns (0.36 to 25 microns without the X-rays). The catalogs were merged across all available wavelengths. Each source was inspected in all available images to insure good matches and quality of data across wavelengths and to eliminate poor candidates, those with contamination or confusion, and non-YSO objects. Spectral energy distributions (SEDs) for each candidate YSO were constructed and compared to images for greater assessment and reliable YSO identification. Color-color and color-magnitude diagrams have been created for the sources in this region and are used in conjunction with images, SEDs, X-ray, IR excess, and variability properties to identify candidate YSOs. Support provided for this work by the NASA/IPAC Teacher Archive Research Program (NITARP), which receives funding from the NASA ADP program.

Optical Monitoring of Young Stellar Objects

NASA Astrophysics Data System (ADS)

Kar, Aman; Jang-Condell, Hannah; Kasper, David; Findlay, Joseph; Kobulnicky, Henry A.

2018-06-01

Observing Young Stellar Objects (YSOs) for variability in different wavelengths enables us to understand the evolution and structure of the protoplanetary disks around stars. The stars observed in this project are known YSOs that show variability in the Infrared. Targets were selected from the Spitzer Space Telescope Young Stellar Object Variability (YSOVAR) Program, which monitored star-forming regions in the mid-infrared. The goal of our project is to investigate any correlation between the variability in the infrared versus the optical. Infrared variability of YSOs is associated with the heating of the protoplanetary disk while accretion signatures are observed in the H-alpha region. We used the University of Wyoming’s Red Buttes Observatory to monitor these stars for signs of accretion using an H-alpha narrowband filter and the Johnson-Cousins filter set, over the Summer of 2017. We perform relative photometry and inspect for an image-to-image variation by observing these targets for a period of four months every two to three nights. The study helps us better understand the link between accretion and H-alpha activity and establish a disk-star connection.

Children's Understanding of the Distinction between Natural and Crafted Objects.

ERIC Educational Resources Information Center

Chen, J. Q.; And Others

This study examined whether evidence for understanding the distinction between natural and man-made aspects of the world can be found in young children. Children 3, 5, and 7 years of age were asked to make judgments about the origins of 12 objects and people's ability to change the objects. The objects were evenly divided into naturally occurring…

How Tactile and Function Information Affect Young Children's Ability to Understand the Nature of Food-Appearing, Deceptive Objects

ERIC Educational Resources Information Center

Krause, Christina Miles

2008-01-01

Preschool children's (N = 64) ability to use tactile information and function cues on less-realistic and more-realistic food-appearing, deceptive objects was examined before and after training on the function of deceptive objects. They also responded to appearance and reality questions about deceptive objects. Half of the children (F-S:…

Surface Variability of Short-wavelength Radiation and Temperature on Exoplanets around M Dwarfs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xin; Tian, Feng; Wang, Yuwei

2017-03-10

It is a common practice to use 3D General Circulation Models (GCM) with spatial resolution of a few hundred kilometers to simulate the climate of Earth-like exoplanets. The enhanced albedo effect of clouds is especially important for exoplanets in the habitable zones around M dwarfs that likely have fixed substellar regions and substantial cloud coverage. Here, we carry out mesoscale model simulations with 3 km spatial resolution driven by the initial and boundary conditions in a 3D GCM and find that it could significantly underestimate the spatial variability of both the incident short-wavelength radiation and the temperature at planet surface.more » Our findings suggest that mesoscale models with cloud-resolving capability be considered for future studies of exoplanet climate.« less

A brown dwarf mass donor in an accreting binary.

PubMed

Littlefair, S P; Dhillon, V S; Marsh, T R; Gänsicke, Boris T; Southworth, John; Watson, C A

2006-12-08

A long-standing and unverified prediction of binary star evolution theory is the existence of a population of white dwarfs accreting from substellar donor stars. Such systems ought to be common, but the difficulty of finding them, combined with the challenge of detecting the donor against the light from accretion, means that no donor star to date has a measured mass below the hydrogen burning limit. We applied a technique that allowed us to reliably measure the mass of the unseen donor star in eclipsing systems. We were able to identify a brown dwarf donor star, with a mass of 0.052 +/- 0.002 solar mass. The relatively high mass of the donor star for its orbital period suggests that current evolutionary models may underestimate the radii of brown dwarfs.

Chronic methylphenidate-effects over circadian cycle of young and adult rats submitted to open-field and object recognition tests.

PubMed

Gomes, Karin M; Souza, Renan P; Valvassori, Samira S; Réus, Gislaine Z; Inácio, Cecília G; Martins, Márcio R; Comim, Clarissa M; Quevedo, João

2009-11-01

In this study age-, circadian rhythm- and methylphenidate administration- effect on open field habituation and object recognition were analyzed. Young and adult male Wistar rats were treated with saline or methylphenidate 2.0 mg/kg for 28 days. Experiments were performed during the light and the dark cycle. Locomotor activity was significantly altered by circadian cycle and methylphenidate treatment during the training session and by drug treatment during the testing session. Exploratory activity was significantly modulated by age during the training session and by age and drug treatment during the testing session. Object recognition memory was altered by cycle at the training session; by age 1.5 h later and by cycle and age 24 h after the training session. These results show that methylphenidate treatment was the major modulator factor on open-field test while cycle and age had an important effect on object recognition experiment.

The accelerating pace of star formation

NASA Astrophysics Data System (ADS)

Caldwell, Spencer; Chang, Philip

2018-03-01

We study the temporal and spatial distribution of star formation rates in four well-studied star-forming regions in local molecular clouds (MCs): Taurus, Perseus, ρ Ophiuchi, and Orion A. Using published mass and age estimates for young stellar objects in each system, we show that the rate of star formation over the last 10 Myr has been accelerating and is (roughly) consistent with a t2 power law. This is in line with previous studies of the star formation history of MCs and with recent theoretical studies. We further study the clustering of star formation in the Orion nebula cluster. We examine the distribution of young stellar objects as a function of their age by computing an effective half-light radius for these young stars subdivided into age bins. We show that the distribution of young stellar objects is broadly consistent with the star formation being entirely localized within the central region. We also find a slow radial expansion of the newly formed stars at a velocity of v = 0.17 km s-1, which is roughly the sound speed of the cold molecular gas. This strongly suggests the dense structures that form stars persist much longer than the local dynamical time. We argue that this structure is quasi-static in nature and is likely the result of the density profile approaching an attractor solution as suggested by recent analytic and numerical analysis.

Retrospective attention in short-term memory has a lasting effect on long-term memory across age.

PubMed

Strunk, Jonathan; Morgan, Lauren; Reaves, Sarah; Verhaeghen, Paul; Duarte, Audrey

2018-04-13

Declines in both short- and long-term memory are typical of healthy aging. Recent findings suggest that retrodictive attentional cues ("retro-cues") that indicate the location of to-be-probed items in short-term memory (STM) have a lasting impact on long-term memory (LTM) performance in young adults. Whether older adults can also use retro-cues to facilitate both STM and LTM is unknown. Young and older adults performed a visual STM task in which spatially informative retro-cues or non-informative neutral-cues were presented during STM maintenance of real-world objects. We tested participants' memory at both STM and LTM delays for objects that were previously cued with retrodictive or neutral cues during STM order to measure the lasting impact of retrospective attention on LTM. Older adults showed reduced STM and LTM capacity compared to young adults. However, they showed similar magnitude retro-cue memory benefits as young adults at both STM and LTM delays. To the best of our knowledge, this is the first study to investigate whether retro-cues in STM facilitate the encoding of objects into LTM such that they are more likely to be subsequently retrieved by older adults. Our results support the idea that retrospective attention can be an effective means by which older adults can improve their short and long-term memory performance, even in the context of reduced memory capacity.

Acute coronary syndrome in young adults from a Malaysian tertiary care centre

PubMed Central

Hoo, Fan Kee; Foo, Yoke Loong; Lim, Sazlyna Mohd Sazlly; Ching, Siew Mooi; Boo, Yang Liang

2016-01-01

Background and Objective: Acute coronary syndrome (ACS) is one of the leading cause of morbidity and mortality worldwide. It is relatively uncommon in young adults as compared to the older population. Our objective was to assess the prevalence, demographic distribution, and risk factors for acute coronary syndrome (ACS) in patients less than 45 years of age admitted to a Malaysian tertiary care centre. Methods: This is a cross-sectional, retrospective, and single centre study with random sampling of the patients admitted for ACS to hospital from January 2005 to December 2013. Data were collected and analyzed. Patients less than 45 years of age were compared with patients more than 45 years of age. Result: A total of 628 patients were included in the study and with the prevalence of young ACS was 6.1% and mean age of 39±6 years. All the young ACS patients were diagnosed with unstable angina and non-ST elevation myocardial infarction (NSTEMI). Tobacco smoking and family history of coronary artery disease (CAD) were more frequent in young ACS. 59.5% of the young ACS patients were smokers, while 37.8% and 51.4% of them were found to suffer from diabetes mellitus and hypertension respectively. Tobacco smoking, diabetes mellitus, and hypertension had shown significant association with the onset of young ACS (p ≤ 0.05). Conclusion: Three leading risk factors (tobacco smoking, diabetes mellitus, and hypertension) had been shown to be significantly associated with the onset of young ACS. Thus, it is important to identify this cohort and implement aggressive measures in tackling the risk factors in order to prevent or halt the development of coronary artery disease. PMID:27648025

Direct observation of extrasolar planets and the development of the gemini planet imager integral field spectrograph

NASA Astrophysics Data System (ADS)

Chilcote, Jeffrey Kaplan

This thesis is focused on the development and testing of a new instrument capable of finding and characterizing recently-formed Jupiter-sized planets orbiting other stars. To observe these planets, I present the design, construction and testing of the Gemini Planet Imager (GPI) Integral Field Spectrograph (IFS). GPI is a facility class instrument for the Gemini Observatory with the primary goal of directly detecting young Jovian planets. The GPI IFS utilizes an infrared transmissive lenslet array to sample a rectangular 2.7 x 2.7 arcsecond field of view and provide low-resolution spectra across five bands between 1 and 2.5 mum. The dispersing element can be replaced with a Wollaston prism to provide broadband polarimetry across the same five filter bands. The IFS construction was based at the University of California, Los Angeles in collaboration with the Universite de Montreal, Immervision and Lawrence Livermore National Laboratory. I will present performance results, from in-lab testing, of the Integral Field Spectrograph (IFS) for the Gemini Planet Imager (GPI). The IFS is a large, complex, cryogenic, optical system requiring several years of development and testing. I will present the design and integration of the mechanical and optical performance of the spectrograph optics. The IFS passed its pre-ship review in 2011 and was shipped to University of California, Santa Cruz for integration with the remaining sub-systems of GPI. The UCLA built GPI IFS was integrated with the rest of GPI and is delivering high quality spectral datacubes of GPI's coronagraphic field. Using the NIRC2 instrument located at the Keck Observatory, my collaborators and I observed the planetary companion to beta Pictoris in L' (3.5--4.1mum). Observations taken in the fall of 2009 and 2012 are used to find the location and inclination of the planet relative to the massive debris disk orbiting beta Pictoris. We find that the planet's orbit has a position angle on the sky of 211.9+/-0.4 degrees, making the planet misaligned by 2.9+/-0.5 degrees from the main disk, consistent with other observations that beta Pic b is misaligned with the main disk, and part of the misaligned inner disk. In 2009 & 2012 we find a projected orbital separation of 312.8 +/- 18.3 and 466.35 +/- 8.4 milliarcseconds consistent with an orbital period of ˜ 20 years, and a semi-major axis of ˜ 9 AU as found by Macintosh et al. (2014). During the first commissioning observations with the Gemini Planet Imager (GPI), my collaborators and I took the first H-band spectrum of the planetary companion to the nearby young star beta Pictoris. The spectrum has a resolving power of ˜ 45 and demonstrates the distinctive triangular shape of a cool substellar object with low surface gravity. Using atmospheric models, we find an effective temperature of 1650 +/- 50K and a surface gravity of log(g) = 4.0 +/- 0.25 (cgs units). These values agree well with predictions from planetary evolution models for a gas giant with mass between 10 and 12 MJup and age between 10 and 20 Myrs. The spectrum is very similar to a known low mass field brown dwarf but has more flux at the long wavelength end of the filters compared to models. Given the very high signal-to-noise of our spectrum this likely indicates additional physics such as patchy clouds that need to be included in the model.

Apodization in high-contrast long-slit spectroscopy. Closer, deeper, fainter, cooler

NASA Astrophysics Data System (ADS)

Vigan, A.; N'Diaye, M.; Dohlen, K.

2013-07-01

The spectroscopy of faint planetary-mass companions to nearby stars is one of the main challenges that new-generation high-contrast spectro-imagers are going to face. However, the high contrast ratio between main-sequence stars and young planets makes it difficult to extract a companion spectrum that is not biased by the signal from the star. In a previous work we demonstrated that coupling long-slit spectroscopy (LSS) and classical Lyot coronagraphy (CLC) to form a long-slit coronagraph (LSC) allows low-mass companions to be properly characterized when combined with an innovative a posteriori data analysis methods based on the spectral deconvolution (SD). However, the presence of a slit in the coronagraphic focal plane induces a complex distribution of energy in the Lyot pupil plane that cannot be easily masked with a binary Lyot stop, creating strong diffraction residuals at close angular separation. To alleviate this concern, we propose to use a pupil apodization to suppress diffraction, creating an apodized long-slit coronagraph (ALSC). We show that this concept allows looking at a closer separation from the star, at deeper contrast, which enables the characterization of fainter substellar companions. After describing how the apodization was optimized, we demonstrate its advantages with respect to the CLC in the context of SPHERE/IRDIS LSS mode at low resolution with a 0.12'' slit and 0.18'' coronagraphic mask. We performed different sets of simulations with and without aberrations, and with and without a slit to demonstrate that the apodization is a more appropriate concept for LSS, at the expense of a significantly reduced throughput (37%) compared to the LSC. Then we performed detailed end-to-end simulations of the LSC and the ALSC that include realistic levels of aberrations to obtain several datasets representing 1 h of integration time on stars of spectral type A0 to M0 located at 10 pc. We inserted the spectra of planetary companions at different effective temperatures (Teff) and surface gravities (log g) into the data at angular separations of 0.3'' to 1.5'' and with contrast ratios from 6 to 18 mag. Using the SD method to subtract the speckles, we show that the ALSC brings a gain in sensitivity of up to ~3 mag at 0.3'' over the LSC and that both concepts are essentially equivalent for separations larger than 0.5''. The gain at small separation is the result of suppressing of the bright Airy rings that are difficult to estimate at very small angular separations because of the point spread function chromaticity. The improved sensitivity is confirmed by extracting the simulated companions spectra from the data and comparing them to libraries of models to determine their Teff and log g. Using a restoration factor that quantitatively compares the input and output spectra, we show that the ALSC data systematically leads to better quality spectra below 0.5''. In terms of Teff, we demonstrate that at small angular separations the limit with the ALSC is always lower by at least 100 K, inducing an increase in sensitivity of a factor up to 1.8 in objects' masses at young ages. Finally, for the determination of log g, we show that the ALSC provides a less biased estimation than the LSC.

THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgasser, Adam J.; Logsdon, Sarah E.; Gagné, Jonathan

2015-09-15

Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2–3 km s{sup −1}, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2 ± 0.2 Gyr for sources within 20 pc. We find signficantly different kinematic ages between late-M dwarfsmore » (4.0 ± 0.2 Gyr) and L dwarfs (6.5 ± 0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313–4912012AB, a low-probability member of the β Pictoris Moving Group; and 2MASS J15104786–2818174, a moderate-probability member of the 30–50 Myr Argus Association.« less

A COMBINED VERY LARGE TELESCOPE AND GEMINI STUDY OF THE ATMOSPHERE OF THE DIRECTLY IMAGED PLANET, β PICTORIS b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Currie, Thayne; Jayawardhana, Ray; Burrows, Adam

We analyze new/archival VLT/NaCo and Gemini/NICI high-contrast imaging of the young, self-luminous planet β Pictoris b in seven near-to-mid IR photometric filters, using advanced image processing methods to achieve high signal-to-noise, high precision measurements. While β Pic b's near-IR colors mimic those of a standard, cloudy early-to-mid L dwarf, it is overluminous in the mid-infrared compared to the field L/T dwarf sequence. Few substellar/planet-mass objects—i.e., κ And b and 1RXJ 1609B—match β Pic b's JHK{sub s}L' photometry and its 3.1 μm and 5 μm photometry are particularly difficult to reproduce. Atmosphere models adopting cloud prescriptions and large (∼60 μm) dustmore » grains fail to reproduce the β Pic b spectrum. However, models incorporating thick clouds similar to those found for HR 8799 bcde, but also with small (a few microns) modal particle sizes, yield fits consistent with the data within the uncertainties. Assuming solar abundance models, thick clouds, and small dust particles ((a) = 4 μm), we derive atmosphere parameters of log (g) = 3.8 ± 0.2 and T{sub eff} = 1575-1650 K, an inferred mass of 7{sup +4}{sub -3} M{sub J} , and a luminosity of log(L/L{sub ☉}) ∼–3.80 ± 0.02. The best-estimated planet radius, ≈1.65 ± 0.06 R{sub J} , is near the upper end of allowable planet radii for hot-start models given the host star's age and likely reflects challenges constructing accurate atmospheric models. Alternatively, these radii are comfortably consistent with hot-start model predictions if β Pic b is younger than ≈7 Myr, consistent with a late formation well after its host star's birth ∼12{sup +8}{sub -4} Myr ago.« less

A Combined Very Large Telescope and Gemini Study of the Atmosphere of the Directly Imaged Planet, β Pictoris b

NASA Astrophysics Data System (ADS)

Currie, Thayne; Burrows, Adam; Madhusudhan, Nikku; Fukagawa, Misato; Girard, Julien H.; Dawson, Rebekah; Murray-Clay, Ruth; Kenyon, Scott; Kuchner, Marc; Matsumura, Soko; Jayawardhana, Ray; Chambers, John; Bromley, Ben

2013-10-01

We analyze new/archival VLT/NaCo and Gemini/NICI high-contrast imaging of the young, self-luminous planet β Pictoris b in seven near-to-mid IR photometric filters, using advanced image processing methods to achieve high signal-to-noise, high precision measurements. While β Pic b's near-IR colors mimic those of a standard, cloudy early-to-mid L dwarf, it is overluminous in the mid-infrared compared to the field L/T dwarf sequence. Few substellar/planet-mass objects—i.e., κ And b and 1RXJ 1609B—match β Pic b's JHKsL' photometry and its 3.1 μm and 5 μm photometry are particularly difficult to reproduce. Atmosphere models adopting cloud prescriptions and large (~60 μm) dust grains fail to reproduce the β Pic b spectrum. However, models incorporating thick clouds similar to those found for HR 8799 bcde, but also with small (a few microns) modal particle sizes, yield fits consistent with the data within the uncertainties. Assuming solar abundance models, thick clouds, and small dust particles (langarang = 4 μm), we derive atmosphere parameters of log (g) = 3.8 ± 0.2 and T eff = 1575-1650 K, an inferred mass of 7^{+4}_{-3} MJ , and a luminosity of log(L/L ⊙) ~-3.80 ± 0.02. The best-estimated planet radius, ≈1.65 ± 0.06 RJ , is near the upper end of allowable planet radii for hot-start models given the host star's age and likely reflects challenges constructing accurate atmospheric models. Alternatively, these radii are comfortably consistent with hot-start model predictions if β Pic b is younger than ≈7 Myr, consistent with a late formation well after its host star's birth ~12^{+8}_{-4} Myr ago.

Everyday Scale Errors

ERIC Educational Resources Information Center

Ware, Elizabeth A.; Uttal, David H.; DeLoache, Judy S.

2010-01-01

Young children occasionally make "scale errors"--they attempt to fit their bodies into extremely small objects or attempt to fit a larger object into another, tiny, object. For example, a child might try to sit in a dollhouse-sized chair or try to stuff a large doll into it. Scale error research was originally motivated by parents' and…

Shaking things up: Young infants' use of sound information for object individuation

PubMed Central

wilcox, Teresa

2013-01-01

A search task was used to assess 5- to 7-month-olds' ability to use property-rich sounds to individuate objects. Results suggest that infants interpret an occlusion event involving two distinct rattle sounds as involving two objects but are unsure of how to interpret two identical rattle sounds. PMID:22306182

Objects, Numbers, Fingers, Space: Clustering of Ventral and Dorsal Functions in Young Children and Adults

ERIC Educational Resources Information Center

Chinello, Alessandro; Cattani, Veronica; Bonfiglioli, Claudia; Dehaene, Stanislas; Piazza, Manuela

2013-01-01

In the primate brain, sensory information is processed along two partially segregated cortical streams: the ventral stream, mainly coding for objects' shape and identity, and the dorsal stream, mainly coding for objects' quantitative information (including size, number, and spatial position). Neurophysiological measures indicate that such…

Developments in Young Infants' Reasoning about Occluded Objects

ERIC Educational Resources Information Center

Aguiar, Andrea; Baillargeon, Renee

2002-01-01

Eight experiments were conducted to examine 3- and 3.5-month-old infants' responses to occlusion events. The results revealed two developments, one in infants' knowledge of when objects should and should not be occluded and the other in infants' ability to posit additional objects to make sense of events that would otherwise violate their…

New T Tauri stars in Chamaeleon I and Chamaeleon II

NASA Technical Reports Server (NTRS)

Hartigan, Patrick

1993-01-01

A new objective prism survey of the entire Chamaeleon I dark cloud and 2/3 of the Chamaeleon II cloud has uncovered 26 new H-alpha emission line objects that were missed by previous H-alpha plate surveys. The new H-alpha emission line objects have similar IR colors and spatial distributions to the known T Tauri stars in these dark clouds, and could represent the very low mass end of the stellar population in these clouds or an older, less active component to the usual classical T Tauri star population. The new H-alpha survey identified 70 percent of the total known Young Stellar Objects (YSOs) in Cha I, compared with 35 percent for IRAS, and 25 percent from the Einstein X-ray survey. Ten of the new objects are weak-lined stars, with H-alpha equivalent widths less than 10 A. Weak-lined T Tauri stars make up about half of the total population of young stars in the Chamaeleon I cloud, a proportion similar to the Taurus-Auriga cloud. Presented are coordinates, finding charts, and optical and IR photometry of the new emission-line objects.

Object-Based Epistemology at a Creationist Museum

NASA Astrophysics Data System (ADS)

Wendel, Paul J.

2011-01-01

In a regional young-earth creationist museum, objects are presented as if they speak for themselves, purportedly embodying proof that the earth is less than 10,000 years old, that humans have lived on earth throughout its history, and that dinosaurs and humans lived simultaneously. In public lectures, tours, and displays, museum associates emphasize direct observation over inference or theory. These emphases resonate closely with the "object-based epistemology" of the late nineteenth century described in Steven Conn's Museums and American Intellectual Life, 1876- 1926. In Conn's description, museum objects, artfully arranged and displayed, were intended to speak for themselves, and observation and categorization were valued over experiment and theory. The regional young-earth creationist museum is observed to partly succeed and partly fail in implementing an object-based epistemology. Although object-based epistemology represents a nineteenth-century approach to knowledge and museum display, it is compatible with an inductive approach to biblical interpretation and it confers various rhetorical advantages to creationist arguments. It is concluded that a focus on the theory-laden nature of data would likely strengthen nature-of-science education efforts to increase public acceptance of evolution.

The Leading Edge: A Career Development Workshop Series for Young Adults. Facilitator Guide.

ERIC Educational Resources Information Center

Canadian Career Development Foundation, Ottawa (Ontario).

This booklet is designed to be used by facilitators of the Canadian Career Development Foundation's "The Leading Edge: A Career Development Workshop Series for Young Adults." The guide provides information, including objectives of the workshops and lists of required materials, needed in order to facilitate an introductory session as well…

Four windows on modern science in flavor and fragrance chemistry at Firmenich.

PubMed

Starkenmann, Christian; Wünsche, Laurent

2012-01-01

Four young scientists, recently hired by Firmenich, presented lectures at the University of Geneva. The objective was to stimulate young students to choose sciences. The challenges in the discovery, synthesis, or extraction of new molecules were presented, as well as the structure-activity relationships of human odorant receptors.

Repetition across Successive Sentences Facilitates Young Children's Word Learning

ERIC Educational Resources Information Center

Schwab, Jessica F.; Lew-Williams, Casey

2016-01-01

Young children who hear more child-directed speech (CDS) tend to have larger vocabularies later in childhood, but the specific characteristics of CDS underlying this link are currently underspecified. The present study sought to elucidate how the structure of language input boosts learning by investigating whether repetition of object labels in…

Silvicultural options for young-growth Douglas-fir forests: the Capitol Forest study—establishment and first results.

Treesearch

Robert O. Curtis; David D. Marshall; Dean S. DeBell

2004-01-01

This report describes the origin, design, establishment and measurement procedures and first results of a large long-term cooperative study comparing a number of widely different silvicultural regimes applied to young-growth Douglas-fir (Pseudotsuga menziesii) stands managed for multiple objectives. Regimes consist of (1) conventional clearcutting...

Motion and Structure Estimation of Manoeuvring Objects in Multiple- Camera Image Sequences

DTIC Science & Technology

1992-11-01

and Speckert [23], Gennery [24], Hallman [25], Legters and Young [26], Stuller and Krishnamurthy [27], Wu et al. [381, Matthies, Kanade, and Szeliski...26] G.R. Legters , T.Y. Young, "A mathematical model for computer image track- ing," IEEE Transactions on Pattern Analysis and Machine Intelligence

Development of a Cross-Cultural HPV Community Engagement Model within Scotland

ERIC Educational Resources Information Center

Carnegie, Elaine; Whittaker, Anne; Gray Brunton, Carol; Hogg, Rhona; Kennedy, Catriona; Hilton, Shona; Harding, Seeromanie; Pollock, Kevin G.; Pow, Janette

2017-01-01

Objective: To examine cultural barriers and participant solutions regarding acceptance and uptake of the human papillomavirus (HPV) vaccine from the perspective of Black African, White-Caribbean, Arab, Indian, Bangladeshi and Pakistani young people. Methods: In total, 40 young people from minority ethnic communities in Scotland took part in a…

Sexual Health Services and Education: Young People's Experiences and Preferences

ERIC Educational Resources Information Center

Reeves, C.; Whitaker, R.; Parsonage, R. K.; Robinson, C. A.; Swale, K.; Bayley, L.

2006-01-01

Objective: To examine young people's requirements and perceptions of sexual health services and education in the context of their experience of sexual relationships and knowledge of sexual health. Design: A questionnaire based cohort study. Setting: Three hundred and sixty Year 11 students (aged 15-16 years) surveyed in three Secondary Schools.…

Helping Parents of Young Children with Disabilities Become Consumers of Early Intervention: A Marketing Approach.

ERIC Educational Resources Information Center

Fugate, Douglas L.; Fugate, Janet M.

1995-01-01

This article suggests the use of marketing techniques to disseminate information products to parents of young children with disabilities. A marketing plan might include the following steps: determination of market needs, market segmentation and target marketing, marketing goals and objectives, marketing strategy, marketing mix tactics, and control…