Science.gov

Sample records for main sequence mass

  1. Exploring The Wide Main Sequence of Low Mass Stars

    NASA Astrophysics Data System (ADS)

    Pewett, Tiffany; Henry, T. J.; Hosey, A. D.; Jao, W.; Lepine, S.; Riedel, A. R.; Winters, J. G.; RECONS Team

    2014-01-01

    The RECONS (REsearch Consortium On Nearby Stars, www.recons.org) team has compiled photometric and astrometric data on over 3000 stars with trigonometric parallaxes placing them within 25 parsecs, allowing for an accurate representation of the H-R Diagram from A stars through M stars. We find that the main sequence is widest, by up to 2.5 full magnitudes in Mv, in the region of low mass K and M dwarf stars. This corresponds to a factor of almost 10 in luminosity among stars of the same temperature, but a detailed understanding of the causes of this range remains elusive. Given that temperature and radius determine the observed luminosity of a star, stars with identical temperatures must have radii differing by up to a factor of three to account for the width of the main sequence. In order to determine the underlying causes of the different radii, we have embarked on a project to measure the variability, rotation, ages, and metallicities of a large sample of the nearest low mass stars. We are comparing these stars to known young stars and cool subdwarfs in the same temperature slices to map the complex interplay of these many factors. Here we present our initial findings from the photometric variability data and first spectroscopic results. This effort is supported by the NSF through grants AST-0908402 and AST-1109445, and via observations made possible by the SMARTS Consortium.

  2. REEVALUATING THE MASS-RADIUS RELATION FOR LOW-MASS, MAIN-SEQUENCE STARS

    SciTech Connect

    Feiden, Gregory A.; Chaboyer, Brian, E-mail: Gregory.A.Feiden.GR@Dartmouth.edu

    2012-09-20

    We examine the agreement between the observed and theoretical low-mass (<0.8 M{sub Sun }) stellar main-sequence mass-radius relationship by comparing detached eclipsing binary (DEB) data with a new, large grid of stellar evolution models. The new grid allows for a realistic variation in the age and metallicity of the DEB population, characteristic of the local galactic neighborhood. Overall, our models do a reasonable job of reproducing the observational data. A large majority of the models match the observed stellar radii to within 4%, with a mean absolute error of 2.3%. These results represent a factor of two improvement compared tomore » previous examinations of the low-mass mass-radius relationship. The improved agreement between models and observations brings the radius deviations within the limits imposed by potential starspot-related uncertainties for 92% of the stars in our DEB sample.« less

  3. Dust discs around low-mass main-sequence stars

    NASA Technical Reports Server (NTRS)

    Wolstencroft, R. D.; Walker, Helen J.

    1988-01-01

    The current understanding of the formation of circumstellar disks as a natural accompaniment to the process of low-mass star formation is examined. Models of the thermal emission from the dust disks around the prototype stars Alpha Lyr, Alpha PsA, Beta Pic, and Epsilon Eri are discussed, which indicate that the central regions of three of these disks are almost devoid of dust within radii ranging between 17 and 26 AU, with the temperature of the hottest zone lying between about 115 and 210 K. One possible explanation of the dust-free zones is the presence of a planet at the inner boundary of each cloud which sweeps up grains crossing its orbit.

  4. Effects of main-sequence mass loss on stellar and galactic chemical evolution

    SciTech Connect

    Guzik, J.A.

    1988-01-01

    L.A. Willson, G.H. Bowen and C. Struck-Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10{sup {minus}9}M mass of sun/yr, diminishing over several times 10{sup 8} years. The author attempts to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity andmore » radius at its present age. The most extreme viable models have initial mass 2.0 M{sub 0}, and mass-loss rates decreasing exponentially over 2-3 {times} 10{sup 8} years. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 M mass of sun and mass loss timescales 0.2 to 2.0 Gry. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M mass of sun and a metallicity-dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus-remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main sequence to the present.« less

  5. Masses of Pre-Main Sequence Binary Stars-Part 2

    NASA Astrophysics Data System (ADS)

    Simon, Michal

    1991-07-01

    There are still no pre-main sequence stars with reliably known masses. This represents a serious gap in our understanding of low-mass star formation. The goal of this long-term program is to measure the masses of pre-main sequence binaries selected from our survey (ref. 3) of the Taurus star forming region by IR lunar occultation and imaging. We propose to use the Fine Guide Sensors in the Transfer Function Mode to determine the apparent orbits of the binaries. Since the distance to the region is known, the apparent orbits will yield the total masses of the binaries. THIS PROPOSAL CONTAINS ONE FOLLOW-UP VISIT TO HV-TAU-C ONLY. THE REST OF THE EXPOSURES ARE IN 3842.

  6. Determining the main-sequence mass of Type II supernova progenitors

    NASA Astrophysics Data System (ADS)

    Dessart, Luc; Livne, Eli; Waldman, Roni

    2010-10-01

    We present radiation-hydrodynamic simulations of core-collapse supernova (SN) explosions, artificially generated by driving a piston at the base of the envelope of a rotating or non-rotating red-supergiant progenitor star. We search for trends in ejecta kinematics in the resulting Type II-Plateau (II-P) SN, exploring dependencies with explosion energy and pre-SN stellar-evolution model. We recover the trivial result that larger explosion energies yield larger ejecta velocities in a given progenitor. However, we emphasize that for a given explosion energy, the increasing helium-core mass with main-sequence mass of such Type II-P SN progenitors leads to ejection of core-embedded oxygen-rich material at larger velocities. We find that the photospheric velocity at 15d after shock breakout is a good and simple indicator of the explosion energy in our selected set of pre-SN models. This measurement, combined with the width of the nebular-phase OI6303-6363 Å line, can be used to place an upper-limit on the progenitor main-sequence mass. Using the results from our simulations, we find that the current, but remarkably scant, late-time spectra of Type II-P SNe support progenitor main-sequence masses inferior to ~20Msolar, and thus corroborate the inferences based on the direct, but difficult, progenitor identification in pre-explosion images. The narrow width of OI6303-6363 Å in Type II-P SNe with nebular spectra does not support high-mass progenitors in the range 25-30Msolar. Combined with quantitative spectroscopic modelling, such diagnostics offer a means to constrain the main-sequence mass of the progenitor, the mass fraction of the core ejected and, thus, the mass of the compact remnant formed.

  7. Reconciling mass functions with the star-forming main sequence via mergers

    NASA Astrophysics Data System (ADS)

    Steinhardt, Charles L.; Yurk, Dominic; Capak, Peter

    2017-06-01

    We combine star formation along the 'main sequence', quiescence and clustering and merging to produce an empirical model for the evolution of individual galaxies. Main-sequence star formation alone would significantly steepen the stellar mass function towards low redshift, in sharp conflict with observation. However, a combination of star formation and merging produces a consistent result for correct choice of the merger rate function. As a result, we are motivated to propose a model in which hierarchical merging is disconnected from environmentally independent star formation. This model can be tested via correlation functions and would produce new constraints on clustering and merging.

  8. Connecting mass accretion and ejection in pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Espaillat, Catherine; Hernandez, Jesus; Grant, Sierra; Macias, Enrique; Reynolds, Mark; Robinson, Connor

    2017-10-01

    Many pre-main sequence stars are surrounded by circumstellar material and display the typical signatures of astrophysical accretion disks, namely mass accretion onto the central object and mass ejection via jets. There is an observed correlation between the accretion rate onto the star and the mass loss rate. This suggests a linked formation mechanism, presumably the stellar magnetic field which can both channel material onto the star as well as eject it in collimated jets along twisted field lines. Here we propose a test of the observed correlation between mass accretion and ejection by using NIR emission to trace the mass reservoir available for accretion in the innermost disk, UV emission to detect accreting gas, and centimeter emission to trace the jet while disentangling the influence of high-energy X-ray radiation from the star. These would be the first simultaneous Chandra-HST-Spitzer-VLA observations of a young, accreting star.

  9. Beyond the Main Sequence: Testing the Accuracy of Stellar Masses Predicted by the PARSEC Evolutionary Tracks

    NASA Astrophysics Data System (ADS)

    Ghezzi, Luan; Johnson, John Asher

    2015-10-01

    Characterizing the physical properties of exoplanets and understanding their formation and orbital evolution requires precise and accurate knowledge of their host stars. Accurately measuring stellar masses is particularly important because they likely influence planet occurrence and the architectures of planetary systems. Single main-sequence stars typically have masses estimated from evolutionary tracks, which generally provide accurate results due to their extensive empirical calibration. However, the validity of this method for subgiants and giants has been called into question by recent studies, with suggestions that the masses of these evolved stars could have been overestimated. We investigate these concerns using a sample of 59 benchmark evolved stars with model-independent masses (from binary systems or asteroseismology) obtained from the literature. We find very good agreement between these benchmark masses and the ones estimated using evolutionary tracks. The average fractional difference in the mass interval ˜0.7-4.5 M⊙ is consistent with zero (-1.30 ± 2.42%), with no significant trends in the residuals relative to the input parameters. A good agreement between model-dependent and -independent radii (-4.81 ± 1.32%) and surface gravities (0.71 ± 0.51%) is also found. The consistency between independently determined ages for members of binary systems adds further support for the accuracy of the method employed to derive the stellar masses. Taken together, our results indicate that determination of masses of evolved stars using grids of evolutionary tracks is not significantly affected by systematic errors, and is thus valid for estimating the masses of isolated stars beyond the main sequence.

  10. The Role Of Rejuvenation In Shaping The High-Mass End Of The Main Sequence

    NASA Astrophysics Data System (ADS)

    Mancini, Chiara

    2017-06-01

    We investigate the nature of star forming galaxies with reduced specific SFRs and high stellar masses, those that seemingly cause the so-called bending of the main sequence. The fact that such objects host large bulges recently lead some to suggest that the internal formation of the bulges, via compaction or disk instabilities, was the late event that induced sSFRs of massive galaxies to drop in a slow downfall and thus the main sequence to bend. We have studied in detail a sample of 16 galaxies at 0.5main sequence' are virtually all maximally old, with ages approaching the age of the Universe at the time of observation, while disks are very young (t50 1-2 Gyr). We conclude that the bending of the main sequence is likely due to rejuvenation, disfavouring mechanisms that postulate the internal formation of bulges at late times.

  11. The open flux evolution of a solar-mass star on the main sequence

    NASA Astrophysics Data System (ADS)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Boro Saikia, S.; Fares, R.; Folsom, C. P.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Petit, P.; BCool Collaboration

    2018-02-01

    Magnetic activity is known to be correlated to the rotation period for moderately active main-sequence solar-like stars. In turn, the stellar rotation period evolves as a result of magnetized stellar winds that carry away angular momentum. Understanding the interplay between magnetic activity and stellar rotation is therefore a central task for stellar astrophysics. Angular momentum evolution models typically employ spin-down torques that are formulated in terms of the surface magnetic field strength. However, these formulations fail to account for the magnetic field geometry, unlike those that are expressed in terms of the open flux, i.e. the magnetic flux along which stellar winds flow. In this work, we model the angular momentum evolution of main-sequence solar-mass stars using a torque law formulated in terms of the open flux. This is done using a potential field source surface model in conjunction with the Zeeman-Doppler magnetograms of a sample of roughly solar-mass stars. We explore how the open flux of these stars varies with stellar rotation and choice of source surface radii. We also explore the effect of field geometry by using two methods of determining the open flux. The first method only accounts for the dipole component while the second accounts for the full set of spherical harmonics available in the Zeeman-Doppler magnetogram. We find only a small difference between the two methods, demonstrating that the open flux, and indeed the spin-down, of main-sequence solar-mass stars is likely dominated by the dipolar component of the magnetic field.

  12. X-ray Emission Properties of Intermediate-Mass, Pre-Main-Sequence Stars

    NASA Astrophysics Data System (ADS)

    Povich, Matthew S.; Binder, Breanna; Townsley, Leisa K.; Broos, Patrick S.

    2017-08-01

    Intermediate-mass (2-8 M⊙) main-sequence stars with A to mid-B spectral types occupy an X-ray "desert" of weak intrinsic emission between low- and high-mass stars. Lacking the wind-shock driven emission of massive, O and early B stars or the convectively-driven magnetic reconnection flaring activity of later-type stars, X-ray detections of (non-peculiar) main-sequence AB stars are typically ascribed to the presence of unresolved, lower-mass binary companions. There is mounting evidence, however, that intermediate-mass, pre-main sequence stars (IMPS) with GK spectral types produce intrinsic X-ray emission that rapidly decays with time following the development of a radiative zone as IMPS approach the ZAMS as AB stars. This suggests that X-ray emission from IMPS may be a more luminous analog of the well-studied coronal X-ray emission from lower-mass, T Tauri stars. Statistical studies of young IMPS have been hampered by their scarcety in nearby, unobscured star-forming regions. We present the first results from a spectral-fitting study to measure absorption-corrected X-ray luminosities and plasma temperatures for hundreds of candidate X-ray emitting IMPS found in the MYStIX and MAGiX surveys of massive Galactic star forming regions. Candidate IMPS are placed on the HR diagram via a novel infrared spectral energy distribution modeling technique designed for highly-obscured, young massive star-forming regions. The rapid decay of X-ray emission from these objects has the potential to provide an independent chronometer to constrain star formation rates, and may produce an age-dependent bias in the relationship between the stellar X-ray luminosity function and mass function in distant (>2 kpc) regions observed with relatively shallow X-ray observations.This work is supported by the National Science Foundation under grant CAREER-1454334 and by NASA through Chandra Award 18200040.

  13. Mass functions for globular cluster main sequences based on CCD photometry and stellar models

    NASA Astrophysics Data System (ADS)

    McClure, Robert D.; Vandenberg, Don A.; Smith, Graeme H.; Fahlman, Gregory G.; Richer, Harvey B.; Hesser, James E.; Harris, William E.; Stetson, Peter B.; Bell, R. A.

    1986-08-01

    Main-sequence luminosity functions constructed from CCD observations of globular clusters reveal a strong trend in slope with metal abundance. Theoretical luminosity functions constructed from VandenBerg and Bell's (1985) isochrones have been fitted to the observations and reveal a trend between x, the power-law index of the mass function, and metal abundance. The most metal-poor clusters require an index of about x = 2.5, whereas the most metal-rich clusters exhibit an index of x of roughly -0.5. The luminosity functions for two sparse clusters, E3 and Pal 5, are distinct from those of the more massive clusters, in that they show a turndown which is possibly a result of mass loss or tidal disruption.

  14. Characterizing Intermediate-Mass, Pre-Main-Sequence Stars via X-Ray Emision

    NASA Astrophysics Data System (ADS)

    Haze Nunez, Evan; Povich, Matthew Samuel; Binder, Breanna Arlene; Broos, Patrick; Townsley, Leisa K.

    2018-01-01

    The X-ray emission from intermediate-mass, pre-main-sequence stars (IMPS) can provide useful constraints on the ages of very young (${<}5$~Myr) massive star forming regions. IMPS have masses between 2 and 8 $M_{\\odot}$ and are getting power from the gravitational contraction of the star. Main-sequence late-B and A-type stars are not expected to be strong X-ray emitters, because they lack the both strong winds of more massive stars and the magneto-coronal activity of lower-mass stars. There is, however, mounting evidence that IMPS are powerful intrinsic x-ray emitters during their convection-dominated early evolution, before the development and rapid growth of a radiation zone. We present our prime candidates for intrinsic, coronal X-ray emission from IMPS identified in the Chandra Carina Complex Project. The Carina massive star-forming complex is of special interest due to the wide variation of star formation stages within the region. Candidate IMPS were identified using infrared spectral energy distribution (SED) models. X-ray properties, including thermal plasma temperatures and absorption-corrected fluxes, were derived from XSPEC fits performed using absorption ($N_{H}$) constrained by the extinction values returned by the infrared SED fits. We find that IMPS have systematically higher X-ray luminosities compared to their lower-mass cousins, the TTauri stars.This work is supported by the National Science Foundation under grant CAREER-1454334 and by NASA through Chandra Award 18200040.

  15. MASS LOSS IN PRE-MAIN-SEQUENCE STARS VIA CORONAL MASS EJECTIONS AND IMPLICATIONS FOR ANGULAR MOMENTUM LOSS

    SciTech Connect

    Aarnio, Alicia N.; Matt, Sean P.; Stassun, Keivan G., E-mail: aarnio@umich.edu

    2012-11-20

    We develop an empirical model to estimate mass-loss rates via coronal mass ejections (CMEs) for solar-type pre-main-sequence (PMS) stars. Our method estimates the CME mass-loss rate from the observed energies of PMS X-ray flares, using our empirically determined relationship between solar X-ray flare energy and CME mass: log (M {sub CME}[g]) = 0.63 Multiplication-Sign log (E {sub flare}[erg]) - 2.57. Using masses determined for the largest flaring magnetic structures observed on PMS stars, we suggest that this solar-calibrated relationship may hold over 10 orders of magnitude in flare energy and 7 orders of magnitude in CME mass. The total CMEmore » mass-loss rate we calculate for typical solar-type PMS stars is in the range 10{sup -12}-10{sup -9} M {sub Sun} yr{sup -1}. We then use these CME mass-loss rate estimates to infer the attendant angular momentum loss leading up to the main sequence. Assuming that the CME outflow rate for a typical {approx}1 M {sub Sun} T Tauri star is <10{sup -10} M {sub Sun} yr{sup -1}, the resulting spin-down torque is too small during the first {approx}1 Myr to counteract the stellar spin-up due to contraction and accretion. However, if the CME mass-loss rate is {approx}> 10{sup -10} M {sub Sun} yr{sup -1}, as permitted by our calculations, then the CME spin-down torque may influence the stellar spin evolution after an age of a few Myr.« less

  16. Is main-sequence galaxy star formation controlled by halo mass accretion?

    NASA Astrophysics Data System (ADS)

    Rodríguez-Puebla, Aldo; Primack, Joel R.; Behroozi, Peter; Faber, S. M.

    2016-01-01

    The galaxy stellar-to-halo mass relation (SHMR) is nearly time-independent for z < 4. We therefore construct a time-independent SHMR model for central galaxies, wherein the in situ star formation rate (SFR) is determined by the halo mass accretion rate (MAR), which we call stellar halo accretion rate coevolution (SHARC). We show that the ˜0.3 dex dispersion of the halo MAR matches the observed dispersion of the SFR on the star formation main sequence (MS). In the context of `bathtub'-type models of galaxy formation, SHARC leads to mass-dependent constraints on the relation between SFR and MAR. Despite its simplicity and the simplified treatment of mass growth from mergers, the SHARC model is likely to be a good approximation for central galaxies with M* = 109-1010.5 M⊙ that are on the MS, representing most of the star formation in the Universe. SHARC predictions agree with observed SFRs for galaxies on the MS at low redshifts, agree fairly well at z ˜ 4, but exceed observations at z ≳ 4. Assuming that the interstellar gas mass is constant for each galaxy (the `equilibrium condition' in bathtub models), the SHARC model allows calculation of net mass loading factors for inflowing and outflowing gas. With assumptions about preventive feedback based on simulations, SHARC allows calculation of galaxy metallicity evolution. If galaxy SFRs indeed track halo MARs, especially at low redshifts, that may help explain the success of models linking galaxy properties to haloes (including age-matching) and the similarities between two-halo galaxy conformity and halo mass accretion conformity.

  17. Standard pre-main sequence models of low-mass stars

    SciTech Connect

    Prada Moroni, P. G.; Degl'Innocenti, S.; Tognelli, E.

    2014-05-09

    The main characteristics of standard pre-main sequence (PMS) models are described. A discussion of the uncer-tainties affecting the current generation of PMS evolutionary tracks and isochrones is also provided. In particular, the impact of the uncertainties in the adopted equation of state, radiative opacity, nuclear cross sections, and initial chemical abundances are analysed.

  18. Ionization Structure and Mass-Loss for Rapidly-Rotating Near Main-Sequence B Stars

    NASA Astrophysics Data System (ADS)

    Bjorkman, J. E.; Abbott, B. P.

    1999-05-01

    Ultraviolet resonance line profiles of rapidly-rotating near main-sequence B stars indicate that the two-dimensional ionization structure of the circumstellar envelope can be crucial to our understanding of the mass-loss rate. We investigate these two-dimensional effects through the use of a radiation transfer model to construct piece-wise spherical ionization fractions for the wind-compressed disk model of a rotating stellar wind. Using these ionization fractions, we generate theoretical line profiles using a two-dimensional Monte Carlo simulation of the radiation transport for the UV resonance lines of Si iii, Si iv, C iii, C iv, and N v. For the B2.5 IV star chosen for this study, we find the mass-loss rate to be on the order of a few times 10(-9) Msuntextrm { yr}(-1) and the X-ray emission measure log EM_X ~ 52.5 cm(-3) . This result is consistent with observed X-ray luminosities as well as UV resonance line profiles. Our mass-loss rate is higher by a factor of 5--10 over those predicted theoretically (via spherically symmetric radiation-driven wind theory) and observationally (due to uncertainties in the ionization fractions). In addition, we also examine the effects of a latitudinal density gradient on the line profiles. We find that the line profiles are sensitive to two-dimensional effects, showing disproportionate amounts of emission versus absorption as the viewing location changes from pole to equator. Specifically, N v, which is abundant in the polar regions and depleted in the equator, shows enhanced emission for an observer looking edge-on to the equatorial wind-compressed disk. We show that spherically symmetric models cannot account for the anomalously strong emission or absorption resulting from a latitudinal ionization gradient in the wind. This work has been supported under NASA grants NAG5-3447 (BPA) and NAG5-3248 (JEB) to the University of Toledo.

  19. The naked T Tauri stars - The low-mass pre-main sequence unveiled

    NASA Technical Reports Server (NTRS)

    Walter, Frederick M.

    1987-01-01

    The search for low-mass premain-sequence (PMS) stars associated with X-ray sources in regions of star formation is discussed. The survey to date has revealed at least 30 low-mass PMS stars in the Tau-Aur region, and a comparable number in Oph. These stars are the naked T Tau stars, unveiled versions of the well-known classical T Tau stars. The properties of these newly discovered PMS stars and their relation to the classical T Tau stars are discussed, and it is concluded that the naked T Tau stars are the true low-mass PMS stars, and that the observable characteristics defining the classical T Tau stars are due to the interaction of an underlying, fairly normal star with a dominant circumstellar environment. The impact the naked T Tau stars are likely to have on models of the PMS evolution of low-mass stars is considered.

  20. Mass loss from pre-main-sequence accretion disks. I - The accelerating wind of FU Orionis

    NASA Technical Reports Server (NTRS)

    Calvet, Nuria; Hartmann, Lee; Kenyon, Scott J.

    1993-01-01

    We present evidence that the wind of the pre-main-sequence object FU Orionis arises from the surface of the luminous accretion disk. A disk wind model calculated assuming radiative equilibrium explains the differential behavior of the observed asymmetric absorption-line profiles. The model predicts that strong lines should be asymmetric and blueshifted, while weak lines should be symmetric and double-peaked due to disk rotation, in agreement with observations. We propose that many blueshifted 'shell' absorption features are not produced in a true shell of material, but rather form in a differentially expanding wind that is rapidly rotating. The inference of rapid rotation supports the proposal that pre-main-sequence disk winds are rotationally driven.

  1. ADIABATIC MASS LOSS IN BINARY STARS. II. FROM ZERO-AGE MAIN SEQUENCE TO THE BASE OF THE GIANT BRANCH

    SciTech Connect

    Ge, Hongwei; Chen, Xuefei; Han, Zhanwen

    2015-10-10

    In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z = 0.02) of mass 0.10 M{sub ⊙}–100 M{sub ⊙} from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. Formore » intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio q{sub ad} (throughout this paper, we follow the convention of defining the binary mass ratio as q ≡ M{sub donor}/M{sub accretor}) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, q{sub ad} plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with q{sub ad} declining with decreasing mass, and asymptotically approaching q{sub ad} = 2/3, appropriate to a classical isentropic n = 3/2 polytrope. Our calculated q{sub ad} values agree well with the behavior of time-dependent models by Chen and Han of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as

  2. Adiabatic Mass Loss in Binary Stars. II. From Zero-age Main Sequence to the Base of the Giant Branch

    NASA Astrophysics Data System (ADS)

    Ge, Hongwei; Webbink, Ronald F.; Chen, Xuefei; Han, Zhanwen

    2015-10-01

    In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z = 0.02) of mass 0.10 M⊙-100 M⊙ from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. For intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio qad (throughout this paper, we follow the convention of defining the binary mass ratio as q ≡ Mdonor/Maccretor) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, qad plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with qad declining with decreasing mass, and asymptotically approaching qad = 2/3, appropriate to a classical isentropic n = 3/2 polytrope. Our calculated qad values agree well with the behavior of time-dependent models by Chen & Han of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as systems that must be stable against rapid mass transfer, nicely

  3. Low-mass, pre-main-sequence stars - The infrared emission from circumstellar dust

    NASA Technical Reports Server (NTRS)

    Wolfire, Mark G.; Churchwell, E.

    1987-01-01

    Models for the dust shells around the low-mass, premain sequence stars IRS 1 and IRS 2 embedded in the Serpens molecular cloud are calculated which accurately fit the stars' observed near-IR fluxes. The far-IR fluxes are predicted, and the model parameters are adjusted to provide a best fit to the observed near-IR spectra. Best fit models are obtained for protostar masses of 2.97 and 2.14 solar masses, an accretion rate of about 10 to the -7th solar masses/yr, and inner shell radii of 9.6 x 10 to the 12th and 4.6 x 10 to the 12th cm, respectively, for IRS 1 and 2. The calculated spectra of the dust shells alone peak at about 2 microns and have no other broad continuum maxima longward of 2-3 microns. The empirical technique of Churchwell and Koornneef (1986) for estimating the mean temperature, radius, and luminosity of circumstellar dust shells by using H and K fluxes gives values in reasonably good agreement with the model calculations.

  4. Tidal Disruptions of Main-sequence Stars of Varying Mass and Age: Inferences from the Composition of the Fallback Material

    NASA Astrophysics Data System (ADS)

    Gallegos-Garcia, Monica; Law-Smith, Jamie; Ramirez-Ruiz, Enrico

    2018-04-01

    We use a simple framework to calculate the time evolution of the composition of the fallback material onto a supermassive black hole arising from the tidal disruption of main-sequence stars. We study stars with masses between 0.8 and 3.0 M ⊙, at evolutionary stages from zero-age main sequence to terminal-age main sequence, built using the Modules for Experiments in Stellar Astrophysics code. We show that most stars develop enhancements in nitrogen (14N) and depletions in carbon (12C) and oxygen (16O) over their lifetimes, and that these features are more pronounced for higher mass stars. We find that, in an accretion-powered tidal disruption flare, these features become prominent only after the time of peak of the fallback rate and appear at earlier times for stars of increasing mass. We postulate that no severe compositional changes resulting from the fallback material should be expected near peak for a wide range of stellar masses and, as such, are unable to explain the extreme helium-to-hydrogen line ratios observed in some TDEs. On the other hand, the resulting compositional changes could help explain the presence of nitrogen-rich features, which are currently only detected after peak. When combined with the shape of the light curve, the time evolution of the composition of the fallback material provides a clear method to help constrain the nature of the disrupted star. This will enable a better characterization of the event by helping break the degeneracy between the mass of the star and the mass of the black hole when fitting tidal disruption light curves.

  5. Evolution models of helium white dwarf-main-sequence star merger remnants: the mass distribution of single low-mass white dwarfs

    NASA Astrophysics Data System (ADS)

    Zhang, Xianfei; Hall, Philip D.; Jeffery, C. Simon; Bi, Shaolan

    2018-02-01

    It is not known how single white dwarfs with masses less than 0.5Msolar -- low-mass white dwarfs -- are formed. One way in which such a white dwarf might be formed is after the merger of a helium-core white dwarf with a main-sequence star that produces a red giant branch star and fails to ignite helium. We use a stellar-evolution code to compute models of the remnants of these mergers and find a relation between the pre-merger masses and the final white dwarf mass. Combining our results with a model population, we predict that the mass distribution of single low-mass white dwarfs formed through this channel spans the range 0.37 to 0.5Msolar and peaks between 0.45 and 0.46Msolar. Helium white dwarf--main-sequence star mergers can also lead to the formation of single helium white dwarfs with masses up to 0.51Msolar. In our model the Galactic formation rate of single low-mass white dwarfs through this channel is about 8.7X10^-3yr^-1. Comparing our models with observations, we find that the majority of single low-mass white dwarfs (<0.5Msolar) are formed from helium white dwarf--main-sequence star mergers, at a rate which is about $2$ per cent of the total white dwarf formation rate.

  6. Calibrating the Mass-Luminosity Relation at the End of the Main Sequence

    NASA Astrophysics Data System (ADS)

    Henry, Todd

    2006-07-01

    We propose to use HST-FGS1R to finish calibrating the mass-luminosity relation for stars less massive than 0.5Msun, with special emphasis on objects near the stellar/substellar border. Our goals are to determine Mv values to 0.05 magnitude and masses to 5%, and thereby build the fundamental database of stellar masses that we will use to test theoretical models as never before.This program uses the combination of HST-FGS3/FGS1R at optical wavelengths, historical infrared speckle data, ground-based parallax work, metallicity studies, and radial velocity monitoring to examine nearby, subarcsecond binary systems. The high precision separation and position angle measurements with HST-FGS3/FGS1R {to 1 mas in the separations} for these faint {V = 10-15} targets simply cannot be equaled by any ground-based technique. As a result of these measurements, we are deriving high quality luminosities and masses for the components in the systems, and characterizing their spectral energy distributions from 0.5 to 2.2 microns. One of the objects, GJ 1245 C with mass 0.074 +/- 0.002 Msun, is the only object known with an accurate dynamical mass less than 0.10 Msun. The payoff of this proposal is high because the six systems selected for final observations in Cycles 15 and 16 have already been resolved during Cycles 5-13 with HST FGS3/FGS1R and contain most of the reddest objects for which accurate dynamical masses can be determined.

  7. Calibrating the Mass-Luminosity Relation at the End of the Main Sequence

    NASA Astrophysics Data System (ADS)

    Henry, Todd

    2007-07-01

    We propose to use HST-FGS1R to finish calibrating the mass-luminosity relation for stars less massive than 0.5 Msun, with special emphasis on objects near the stellar/substellar border. Our goals are to determine Mv values to 0.05 magnitude and masses to 5%, and thereby build the fundamental database of stellar masses that we will use to test theoretical models as never before.This program uses the combination of HST-FGS3/FGS1R at optical wavelengths, historical infrared speckle data, ground-based parallax work, metallicity studies, and radial velocity monitoring to examine nearby, subarcsecond binary systems. The high precision separation and position angle measurements with HST-FGS3/FGS1R {to 1 mas in the separations} for these faint {V = 10-15} targets simply cannot be equaled by any ground-based technique. As a result of these measurements, we are deriving high quality luminosities and masses for the components in the systems, and characterizing their spectral energy distributions from 0.5 to 2.2 microns. One of the objects, GJ 1245 C with mass 0.074 +/- 0.002 Msun, is the only object known with an accurate dynamical mass less than 0.10 Msun. The payoff of this proposal is high because the six systems selected for final observations in Cycles 15 and 16 have already been resolved during Cycles 5-13 with HST FGS3/FGS1R and contain most of the reddest objects for which accurate dynamical masses can be determined.

  8. PHOTOMETRIC DETERMINATION OF THE MASS ACCRETION RATES OF PRE-MAIN-SEQUENCE STARS. IV. RECENT STAR FORMATION IN NGC 602

    SciTech Connect

    De Marchi, Guido; Beccari, Giacomo; Panagia, Nino, E-mail: gdemarchi@rssd.esa.int, E-mail: gbeccari@eso.org, E-mail: panagia@stsci.edu

    2013-09-20

    We have studied the young stellar populations in NGC 602, in the Small Magellanic Cloud, using a novel method that we have developed to combine Hubble Space Telescope photometry in the V, I, and Hα bands. We have identified about 300 pre-main-sequence (PMS) stars, all of which are still undergoing active mass accretion, and have determined their physical parameters (effective temperature, luminosity, age, mass, and mass accretion rate). Our analysis shows that star formation has been present in this field over the last 60 Myr. In addition, we can recognize at least two clear, distinct, and prominent episodes in themore » recent past: one about 2 Myr ago, but still ongoing in regions of higher nebulosity, and one (or more) older than 30 Myr, encompassing both stars dispersed in the field and two smaller clusters located about 100'' north of the center of NGC 602. The relative locations of younger and older PMS stars do not imply a causal effect or triggering of one generation on the other. The strength of the two episodes appears to be comparable, but the episodes occurring more than 30 Myr ago might have been even stronger than the current one. We have investigated the evolution of the mass accretion rate, M-dot{sub acc}, as a function of the stellar parameters finding that log M-dot{sub acc}≅-0.6 log t + log m + c, where t is the age of the star, m is its mass, and c is a decreasing function of the metallicity.« less

  9. Effect of accretion on the pre-main-sequence evolution of low-mass stars and brown dwarfs

    NASA Astrophysics Data System (ADS)

    Vorobyov, Eduard I.; Elbakyan, Vardan; Hosokawa, Takashi; Sakurai, Yuya; Guedel, Manuel; Yorke, Harold

    2017-09-01

    Aims: The pre-main-sequence evolution of low-mass stars and brown dwarfs is studied numerically starting from the formation of a protostellar or proto-brown dwarf seed and taking into account the mass accretion onto the central object during the initial several Myr of evolution. Methods: The stellar evolution was computed using the STELLAR evolution code with recent modifications. The mass accretion rates were taken from numerical hydrodynamics models by computing the circumstellar disk evolution starting from the gravitational collapse of prestellar cloud cores of various mass and angular momentum. The resulting stellar evolution tracks were compared with the isochrones and isomasses calculated using non-accreting models. Results: We find that mass accretion in the initial several Myr of protostellar evolution can have a strong effect on the subsequent evolution of young stars and brown dwarfs. The disagreement between accreting and non-accreting models in terms of the total stellar luminosity L∗, stellar radius R∗, and effective temperature Teff depends on the thermal efficiency of accretion, that is, on the fraction of accretion energy that is absorbed by the central object. The largest mismatch is found for the cold accretion case, in which essentially all accretion energy is radiated away. The relative deviations in L∗ and R∗ in this case can reach 50% for objects 1.0 Myr old, and they remain notable even for objects 10 Myr old. In the hot and hybrid accretion cases, in which a constant fraction of accretion energy is absorbed, the disagreement between accreting and non-accreting models becomes less pronounced, but still remains notable for objects 1.0 Myr old. These disagreements may lead to an incorrect age estimate for objects of (sub-)solar mass when using the isochrones that are based on non-accreting models, as has also been noted previously. We find that objects with strong luminosity bursts exhibit notable excursions in the L∗-Teff diagram

  10. Detection of [O III] at z ∼ 3: A Galaxy Above the Main Sequence, Rapidly Assembling Its Stellar Mass

    NASA Astrophysics Data System (ADS)

    Vishwas, Amit; Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen C.; Schoenwald, Justin P.; Stacey, Gordon J.; Higdon, Sarah J. U.; Higdon, James L.; Weiss, Axel; Güsten, Rolf; Menten, Karl M.

    2018-04-01

    We detect bright emission in the far-infrared (far-IR) fine structure [O III] 88 μm line from a strong lensing candidate galaxy, H-ATLAS J113526.3-014605, hereafter G12v2.43, at z = 3.127, using the second-generation Redshift (z) and Early Universe Spectrometer (ZEUS-2) at the Atacama Pathfinder Experiment Telescope (APEX). This is only the fifth detection of this far-IR line from a submillimeter galaxy at the epoch of galaxy assembly. The observed [O III] luminosity of 7.1 × 109 ≤ft(\\tfrac{10}{μ }\\right) L ⊙ likely arises from H II regions around massive stars, and the amount of Lyman continuum photons required to support the ionization indicate the presence of (1.2–5.2) × 106 ≤ft(\\tfrac{10}{μ }\\right) equivalent O5.5 or higher stars, where μ would be the lensing magnification factor. The observed line luminosity also requires a minimum mass of ∼2 × 108 ≤ft(\\tfrac{10}{μ }\\right) M ⊙ in ionized gas, that is 0.33% of the estimated total molecular gas mass of 6 × 1010 ≤ft(\\tfrac{10}{μ }\\right) M ⊙. We compile multi-band photometry tracing rest-frame ultraviolet to millimeter continuum emission to further constrain the properties of this dusty high-redshift, star-forming galaxy. Via SED modeling we find G12v2.43 is forming stars at a rate of 916 ≤ft(\\tfrac{10}{μ }\\right) M ⊙ yr‑1 and already has a stellar mass of 8 × 1010 ≤ft(\\tfrac{10}{μ }\\right) M ⊙. We also constrain the age of the current starburst to be ≤slant 5 Myr, making G12v2.43 a gas-rich galaxy lying above the star-forming main sequence at z ∼ 3, undergoing a growth spurt, and it could be on the main sequence within the derived gas depletion timescale of ∼66 Myr.

  11. Evolution of very low mass pre-main sequence stars and young brown dwarfs under accretion A phenomenological approach

    NASA Astrophysics Data System (ADS)

    Gallardo, J.; Baraffe, I.; Chabrier, G.

    2009-02-01

    In the poster presented in Cool Star 15, we analyzed the effect of disk accretion on the evolution of very low mass pre-main sequence stars and young brown dwarfs and the resulting uncertainties on the determination of masses and ages. We use the Lyon evolutionary 1-D code ([1]) assuming a magnetospheric accretion process, i.e., the material falls covering a small area of the radiative surface, and we take into account the internal energy added from the accreted material as a free parameter ɛ. Even if the approach to this problem is phenomenological, our formalism provides important hints about characteristics of disk accretion, which are useful for improved stellar interior calculations. Using the accretion rates derived from observations our results show that accretion does not affect considerably the position of theoretical isochrones as well as the luminosity compared with standard non-accreting models (e.g., [2]). See more discussions in a forthcoming paper by Gallardo, Baraffe & Chabrier (2008).

  12. Low-mass members of the young cluster IC 4665 and pre-main-sequence lithium depletion

    NASA Astrophysics Data System (ADS)

    Jeffries, R. D.; Jackson, R. J.; James, David J.; Cargile, P. A.

    2009-11-01

    We have used fibre spectroscopy to establish cluster membership and examine pre-main-sequence (PMS) lithium depletion for low-mass stars (spectral types F to M) in the sparse young (~=30Myr) cluster IC 4665. We present a filtered candidate list of 40 stars that should contain 75 per cent of single cluster members with 11.5 < V < 18 in the central square degree of the cluster. Whilst F- and G-type stars in IC 4665 have depleted little or no lithium, the K- and early M-type stars have depleted more Li than expected when compared with similar stars in other clusters of known age. An empirical age estimate based on Li depletion among the late-type stars of IC 4665 would suggest that it is older than 100Myr. This disagrees entirely with ages determined either from the nuclear turn-off, from isochronal matches to low-mass stars or from the re-appearance of lithium previously found in much lower mass stars (the `lithium depletion boundary'). We suggest that other parameters besides age, perhaps composition or rotation, are very influential in determining the degree of PMS Li depletion in stars with M > 0.5Msolar. Further work is required to identify and assess the effects of these additional parameters, particularly to probe conditions at the interface between the subphotospheric convection zone and developing radiative core. Until then, PMS Li depletion in F- to early M-type stars cannot be confidently used as a precise age indicator in young clusters, kinematic groups or individual field stars.

  13. A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

    NASA Astrophysics Data System (ADS)

    Gillen, Ed; Aigrain, Suzanne; McQuillan, Amy; Bouvier, Jerome; Hodgkin, Simon; Alencar, Silvia; Terquem, Caroline; Southworth, John; Gibson, Neale; Cody, Ann Marie; Lendl, Monika; Morales-Calderón, Maria; Favata, Fabio; Stauffer, John; Micela, Giusi

    2013-07-01

    We present the discovery of a double-lined, detached eclipsing binary (EB), comprising two pre-main sequence M-dwarfs, in the 3 Myr old NGC 2264 star-forming region. Eclipses were detected in this system, during a continuous 23-day observation of NGC 2264 by the CoRoT space mission in 2008. Multi-epoch optical and near-IR follow-up spectroscopy with VLT/FLAMES and WHT/ISIS yielded a full orbital solution. We derive fundamental stellar parameters by modelling the light curve and radial velocity data, finding that the two stars travel on essentially circular orbits with a period of 3.8745745 ± 0.0000014 days and have masses of 0.67 ± 0.01 and 0.495 ± 0.007 M_sun with corresponding radii of 1.30 ± 0.04 and 1.11 ± 0.05 R_sun. The CoRoT light curve also contains large-amplitude, rapidly evolving out-of-eclipse variations, which are difficult to explain with star spots alone. SED modelling of the system's broadband optical and infrared magnitudes reveals a mid-IR excess, which we model as emission from a small amount of dust located within the inner cavity of a circumbinary disk. In turn, this opens up the possibility that some of the out-of-eclipse variability could be due to occultations of the central stars by material located at the inner edge or in the central cavity of the circumbinary disk.

  14. A Main Sequence For Quasars

    NASA Astrophysics Data System (ADS)

    Marziani, Paola; Sulentic, J. W.; Dultzin, D.; Negrete, A.; del Olmo, A.; Martínez-Carballo, M. A.; Stirpe, G. M.; D'Onofrio, M.; Perea, J.

    2016-10-01

    The 4D eigenvector 1 parameter space defined by Sulentic et al. may be seen as a surrogate H-R diagram for quasars. As in the stellar H-R diagram, a source sequence can be easily identified. In the case of quasars, the main sequence appears to be mainly driven by Eddington ratio. A transition Eddington ratio may in part explain the striking observational differences between quasars at opposite ends of the main sequence. The eigenvector-1 approach opens the door towards properly contextualized models of quasar physics, geometry and kinematics. We review some of the progress that has been made over the past 15 years, and point out still unsolved issues.

  15. 2-D and 3-D models of convective turbulence and oscillations in intermediate-mass main-sequence stars

    NASA Astrophysics Data System (ADS)

    Guzik, Joyce A.; Morgan, T. H.; Nelson, N. J.; Lovekin, C.; Kosak, K.; Kitiashvili, I. N.; Mansour, N. N.; Kosovichev, A.

    We present multidimensional modeling of convection and oscillations in main-sequence stars somewhat more massive than the Sun, using three separate approaches: 1) Using the 3-D planar StellarBox radiation hydrodynamics code to model the envelope convection zone and part of the radiative zone. Our goals are to examine the interaction of stellar pulsations with turbulent convection in the envelope, excitation of acoustic modes, and the role of convective overshooting; 2) Applying the spherical 3-D MHD ASH (Anelastic Spherical Harmonics) code to simulate the core convection and radiative zone. Our goal is to determine whether core convection can excite low-frequency gravity modes, and thereby explain the presence of low frequencies for some hybrid γ Dor/δ Sct variables for which the envelope convection zone is too shallow for the convective blocking mechanism to drive gravity modes; 3) Applying the ROTORC 2-D stellar evolution and dynamics code to calculate evolution with a variety of initial rotation rates and extents of core convective overshooting. The nonradial adiabatic pulsation frequencies of these nonspherical models are calculated using the 2-D pulsation code NRO. We present new insights into pulsations of 1-2 M⊙ stars gained by multidimensional modeling.

  16. 2D and 3D Models of Convective Turbulence and Oscillations in Intermediate-Mass Main-Sequence Stars

    NASA Astrophysics Data System (ADS)

    Guzik, Joyce Ann; Morgan, Taylor H.; Nelson, Nicholas J.; Lovekin, Catherine; Kitiashvili, Irina N.; Mansour, Nagi N.; Kosovichev, Alexander

    2015-08-01

    We present multidimensional modeling of convection and oscillations in main-sequence stars somewhat more massive than the sun, using three separate approaches: 1) Applying the spherical 3D MHD ASH (Anelastic Spherical Harmonics) code to simulate the core convection and radiative zone. Our goal is to determine whether core convection can excite low-frequency gravity modes, and thereby explain the presence of low frequencies for some hybrid gamma Dor/delta Sct variables for which the envelope convection zone is too shallow for the convective blocking mechanism to drive g modes; 2) Using the 3D planar ‘StellarBox’ radiation hydrodynamics code to model the envelope convection zone and part of the radiative zone. Our goals are to examine the interaction of stellar pulsations with turbulent convection in the envelope, excitation of acoustic modes, and the role of convective overshooting; 3) Applying the ROTORC 2D stellar evolution and dynamics code to calculate evolution with a variety of initial rotation rates and extents of core convective overshooting. The nonradial adiabatic pulsation frequencies of these nonspherical models will be calculated using the 2D pulsation code NRO of Clement. We will present new insights into gamma Dor and delta Sct pulsations gained by multidimensional modeling compared to 1D model expectations.

  17. A Study of the Wide Main Sequence: The Long-Term Photometric Variability of Low Mass Stars

    NASA Astrophysics Data System (ADS)

    Pewett, Tiffany; Henry, Todd J.; Hosey, Altonio D.; Dieterich, Sergio; Jao, Wei-Chun; Winters, Jennifer G.; Riedel, Adric R.; RECONS Team

    2016-01-01

    The RECONS (REsearch Consortium On Nearby Stars, www.recons.org) team has carried out a long-term photometric variability study using the SMARTS 0.9m telescope at the Cerro Tololo Inter-American Observatory (CTIO). The program has obtained up to 15 years of observations in the V band for hundreds of M dwarf stars. This unique study has provided insight into how the ubiquitous M dwarfs change over decadal timescales, revealing their long-term magnetic cycles and how the presence or lack of such activity may affect their sizes and consequent luminosities, and thus their positions on the H-R Diagram.Using carefully vetted parallaxes and photometric colors, many measured by the RECONS team, we have created a highly accurate H-R Diagram of the nearest (within 25pc) stars using their V-K colors to represent temperatures and absolute V magnitudes as proxies for luminosities. We find that for M dwarfs, the main sequence widens significantly, by up to four magnitudes in MV, corresponding to a factor of almost 40 in optical flux. This spread implies a wide range of stellar radii for M dwarfs of the same temperature. Our study of long-term photometric variability indicates that there is a trend in cyclic activity that is highest for the most luminous red dwarfs and lowest for the rare, cool red subdwarfs. This provides valuable insight into the complex interplay of age, metallicity, and magnetic fields that molds the character of the red dwarfs.This effort has been supported by the NSF through grants AST-0908402, AST-1109445, and AST-1412026, STScI grant HST-GO-13724.001-A, and via observations made possible by the SMARTS Consortium.

  18. Testing the companion hypothesis for the origin of the X-ray emission from intermediate-mass main-sequence stars

    NASA Astrophysics Data System (ADS)

    Stelzer, B.; Huélamo, N.; Micela, G.; Hubrig, S.

    2006-06-01

    Context: .The X-ray emission from B-type main-sequence stars is a longstanding mystery in stellar coronal research. Since there is no theory at hand that explains intrinsic X-ray emission from intermediate-mass main-sequence stars, the observations have often been interpreted in terms of (unknown) late-type magnetically active companion stars. Aims: .Resolving the hypothesized companions requires high spatial resolution observations in the infrared and in X-rays. We use Chandra imaging observations to spatially resolve a sample of main-sequence B-type stars with recently discovered companions at arcsecond separation. Methods: .Our strategy is to search for X-ray emission at the position of both the B-type primary and the faint companion. Results: .We find that all spatially resolved companions are X-ray emitters, but seven out of eleven intermediate-mass stars are also X-ray sources. If this emission is interpreted in terms of additional sub-arcsecond or spectroscopic companions, this implies a high multiplicity of B-type stars. Firm results on B star multiplicity pending, the alternative, that B stars produce intrinsic X-rays, cannot be discarded. An appropriate scenario would be a magnetically confined wind, as suggested for the X-ray emission of the magnetic Ap star IQ Aur. However, the only Ap star in the Chandra sample is not detected in X-rays, and therefore does not support this picture.

  19. X-Ray Properties of Low-mass Pre-main Sequence Stars in the Orion Trapezium Cluster

    NASA Astrophysics Data System (ADS)

    Schulz, Norbert S.; Huenemoerder, David P.; Günther, Moritz; Testa, Paola; Canizares, Claude R.

    2015-09-01

    The Chandra HETG Orion Legacy Project (HOLP) is the first comprehensive set of observations of a very young massive stellar cluster that provides high-resolution X-ray spectra of very young stars over a wide mass range (0.7-2.3 {M}⊙ ). In this paper, we focus on the six brightest X-ray sources with T Tauri stellar counterparts that are well-characterized at optical and infrared wavelengths. All stars show column densities which are substantially smaller than expected from optical extinction, indicating that the sources are located on the near side of the cluster with respect to the observer as well as that these stars are embedded in more dusty environments. Stellar X-ray luminosities are well above 1031 erg s-1, in some cases exceeding 1032 erg s-1 for a substantial amount of time. The stars during these observations show no flares but are persistently bright. The spectra can be well fit with two temperature plasma components of 10 MK and 40 MK, of which the latter dominates the flux by a ratio 6:1 on average. The total emission measures range between 3-8 × 1054 cm-3 and are comparable to active coronal sources. The fits to the Ne ix He-Like K-shell lines indicate forbidden to inter-combination line ratios consistent with the low-density limit. Observed abundances compare well with active coronal sources underlying the coronal nature of these sources. The surface flux in this sample of 0.6-2.3 {M}⊙ classical T Tauri stars shows that coronal activity increases significantly between ages 0.1 and 10 Myr. The results demonstrate the power of X-ray line diagnostics to study coronal properties of T Tauri stars in young stellar clusters.

  20. PHOTOMETRIC DETERMINATION OF THE MASS ACCRETION RATES OF PRE-MAIN-SEQUENCE STARS. II. NGC 346 IN THE SMALL MAGELLANIC CLOUD

    SciTech Connect

    De Marchi, Guido; Sirianni, Marco; Panagia, Nino

    2011-10-10

    We have studied the properties of the stellar populations in the field of the NGC 346 cluster in the Small Magellanic Cloud, using a novel self-consistent method that allows us to reliably identify pre-main-sequence (PMS) objects actively undergoing mass accretion, regardless of their age. The method does not require spectroscopy and combines broadband V and I photometry with narrowband H{alpha} imaging to identify all stars with excess H{alpha} emission and derive the accretion luminosity L{sub acc} and mass accretion rate M-dot{sub acc} for all of them. The application of this method to existing Hubble Space Telescope (HST)/Advanced Camera for Surveysmore » photometry of the NGC 346 field has allowed us to identify and study 680 bona fide PMS stars with masses from {approx}0.4 M{sub sun} to {approx}4 M{sub sun} and ages in the range from {approx}1 Myr to {approx}30 Myr. Previous investigations of this region, based on the same data, had identified young ({approx}3 Myr old) candidate PMS stars on the basis of their broadband colors. In this study, we show that there are at least two, almost equally numerous, young populations with distinct ages of, respectively, {approx}1 and {approx}20 Myr. We provide accurate physical parameters for all of them. We take advantage of the unprecedented size of our PMS sample and of its spread in mass and age to study the evolution of the mass accretion rate as a function of stellar parameters. We find that, regardless of stellar mass, the mass accretion rate decreases with roughly the square root of the age, or about three times slower than predicted by current models of viscous disk evolution, and that more massive stars systematically have a higher mass accretion rate in proportion to their mass. A multivariate linear regression fit reveals that log M-dot{sub acc}{approx_equal}-0.6 log t + log m + c, where t is the age of the star, m is its mass, and c is a quantity that is higher at lower metallicity. This result is

  1. Theoretical studies of massive stars. I - Evolution of a 15-solar-mass star from the zero-age main sequence to neon ignition

    NASA Technical Reports Server (NTRS)

    Endal, A. S.

    1975-01-01

    The evolution of a star with mass 15 times that of the sun from the zero-age main sequence to neon ignition has been computed by the Henyey method. The hydrogen-rich envelope and all shell sources were explicitly included in the models. An algorithm has been developed for approximating the results of carbon burning, including the branching ratio for the C-12 + C-12 reaction and taking some secondary reactions into account. Penetration of the convective envelope into the core is found to be unimportant during the stages covered by the models. Energy transfer from the carbon-burning shell to the core by degenerate electron conduction becomes important after the core carbon-burning stage. Neon ignition will occur in a semidegenerate core and will lead to a mild 'flash.' Detailed numerical results are given in an appendix. Continuation of the calculations into later stages and variations with the total mass of the star will be discussed in later papers.

  2. The Pisa pre-main sequence tracks and isochrones. A database covering a wide range of Z, Y, mass, and age values

    NASA Astrophysics Data System (ADS)

    Tognelli, E.; Prada Moroni, P. G.; Degl'Innocenti, S.

    2011-09-01

    Context. In recent years new observations of pre-main sequence stars (pre-MS) with Z ≤ Z⊙ have been made available. To take full advantage of the continuously growing amount of data of pre-MS stars in different environments, we need to develop updated pre-MS models for a wide range of metallicity to assign reliable ages and masses to the observed stars. Aims: We present updated evolutionary pre-MS models and isochrones for a fine grid of mass, age, metallicity, and helium values. Methods: We use a standard and well-tested stellar evolutionary code (i.e. FRANEC), that adopts outer boundary conditions from detailed and realistic atmosphere models. In this code, we incorporate additional improvements to the physical inputs related to the equation of state and the low temperature radiative opacities essential to computing low-mass stellar models. Results: We make available via internet a large database of pre-MS tracks and isochrones for a wide range of chemical compositions (Z = 0.0002-0.03), masses (M = 0.2-7.0 M⊙), and ages (1-100 Myr) for a solar-calibrated mixing length parameter α (i.e. 1.68). For each chemical composition, additional models were computed with two different mixing length values, namely α = 1.2 and 1.9. Moreover, for Z ≥ 0.008, we also provided models with two different initial deuterium abundances. The characteristics of the models have been discussed in detail and compared with other work in the literature. The main uncertainties affecting theoretical predictions have been critically discussed. Comparisons with selected data indicate that there is close agreement between theory and observation. Tracks and isochrones are available on the web at the http://astro.df.unipi.it/stellar-models/Tracks and isochrones are also available in electronic form 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/533/A109

  3. Submillimeter studies of main-sequence stars

    NASA Astrophysics Data System (ADS)

    Zuckerman, B.; Becklin, E. E.

    1993-09-01

    JCMT maps of the 800-micron emission from Vega, Fomalhaut, and Beta Pictoris are interpreted to indicate that they are not ringed by large reservoirs of distant orbiting dust particles that are too cold to have been detected by IRAS. A search for 800-micron emission from stars in the Pleiades and Ursa Majoris open clusters is reported. In comparison with the mass of dust particles near T Tauri and Herbig Ae stars, the JCMT data indicate a decline in dust mass during the initial 3 x 10 exp 8 yr that a star spends on the main sequence that is at least as rapid as (time) exp -2. It is estimated that in the Kuiper belt the ratio of total mass carried by small particles to that carried by comets is orders of magnitude smaller than this ratio is 1 AU from the sun. If 800-micron opacities calculated by Pollack et al. (1993) are correct, then the particles with radii less than 100 microns that dominate the FIR fluxes measured by IRAS cannot entirely account for the measured 800-micron fluxes at Vega, Beta Pic, and Fomalhaut; larger particles must be present as well.

  4. PHOTOMETRIC DETERMINATION OF THE MASS ACCRETION RATES OF PRE-MAIN-SEQUENCE STARS. I. METHOD AND APPLICATION TO THE SN 1987A FIELD

    SciTech Connect

    De Marchi, Guido; Panagia, Nino; Romaniello, Martino, E-mail: gdemarchi@rssd.esa.in, E-mail: panagia@stsci.ed, E-mail: mromanie@eso.or

    2010-05-20

    We have developed and successfully tested a new self-consistent method to reliably identify pre-main-sequence (PMS) objects actively undergoing mass accretion in a resolved stellar population, regardless of their age. The method does not require spectroscopy and combines broadband V and I photometry with narrowband H{alpha} imaging to (1) identify all stars with excess H{alpha} emission, (2) convert the excess H{alpha} magnitude into H{alpha} luminosity L(H{alpha}), (3) estimate the H{alpha} emission equivalent width, (4) derive the accretion luminosity L{sub acc} from L(H{alpha}), and finally (5) obtain the mass accretion rate M-dot{sub acc} from L{sub acc} and the stellar parameters (mass andmore » radius). By selecting stars with an accuracy of 15% or better in the H{alpha} photometry, the statistical uncertainty on the derived M-dot{sub acc} is typically {approx_lt}17% and is dictated by the precision of the H{alpha} photometry. Systematic uncertainties, of up to a factor of 3 on the value of M-dot{sub acc}, are caused by our incomplete understanding of the physics of the accretion process and affect all determinations of the mass accretion rate, including those based on a spectroscopic H{alpha} line analysis. As an application of our method, we study the accretion process in a field of 9.16 arcmin{sup 2} around SN 1987A, using existing Hubble Space Telescope photometry. We identify as bona fide PMS stars a total of 133 objects with a H{alpha} excess above the 4{sigma} level and a median age of 13.5 Myr. Their median mass accretion rate of 2.6 x 10{sup -8} M{sub sun} yr{sup -1} is in excellent agreement with previous determinations based on the U-band excess of the stars in the same field, as well as with the value measured for G-type PMS stars in the Milky Way. The accretion luminosity of these PMS objects shows a strong dependence on their distance from a group of hot massive stars in the field and suggests that the ultraviolet radiation of the latter is

  5. The very low mass multiple system LHS 1070. A testbed for model atmospheres for the lower end of the main sequence

    NASA Astrophysics Data System (ADS)

    Rajpurohit, A. S.; Reylé, C.; Schultheis, M.; Leinert, Ch.; Allard, F.; Homeier, D.; Ratzka, T.; Abraham, P.; Moster, B.; Witte, S.; Ryde, N.

    2012-09-01

    Context. LHS 1070 is a nearby multiple system of low mass stars. It is an important source of information for probing the low mass end of the main sequence, down to the hydrogen-burning limit. The primary of the system is a mid-M dwarf and two components are late-M to early L dwarfs, at the star-brown dwarf transition. Hence LHS 1070 is a valuable object to understand the onset of dust formation in cool stellar atmospheres. Aims: This work aims at determining the fundamental stellar parameters of LHS 1070 and to test recent model atmospheres: BT-Dusty, BT-Settl, DRIFT, and MARCS models. Methods: Unlike in previous studies, we have performed a χ2-minimization comparing well calibrated optical and infrared (IR) spectra with recent cool star synthetic spectra leading to the determination of the physical stellar parameters Teff, radius, and log g for each of the three components of LHS 1070. Results: With exception of the MARCS models which do not include dust formation, the models are able to reproduce the observations and describe the main features of the visible to IR spectra. This is consistent with the fact that dust formation prevails in the B and C component atmospheres. The parameters obtained with the DRIFT models confirm the values determined in earlier studies. But important differences between models are observed, where the MARCS model is too bright in the H and K bands, and the BT-Settl and BT-Dusty models systematically yield up to 100 K higher Teff in the case of the B and C components. This confirms a trend for models without, or with less efficient cloud formation, to predict higher Teff than models richer in dust (DRIFT). Even models including cloud physics however still produce slightly too bright J band flux, showing as too blue J - K colors. The onset of dust formation remains therefore a particularly challenging regime to understand. Based on observations made with the ESO Very Large Telescope at the Paranal Observatory under programme 072.C-0022

  6. Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. V. Recent Star Formation in the 30 Dor Nebula

    NASA Astrophysics Data System (ADS)

    De Marchi, Guido; Panagia, Nino; Beccari, Giacomo

    2017-09-01

    We report on the properties of the low-mass stars that recently formed in the central ˜ 2\\buildrel{ \\prime}\\over{.} 7× 2\\buildrel{ \\prime}\\over{.} 7 of 30 Dor, including the R136 cluster. Using the photometric catalog of De Marchi et al., based on observations with the Hubble Space Telescope, and the most recent extinction law for this field, we identify 1035 bona fide pre-main-sequence (PMS) stars showing {{H}}α excess emission at the 4σ level with an {{H}}α equivalent width of 20 Å or more. We find a wide spread in age spanning the range ˜ 0.1{--}50 {Myr}. We also find that the older PMS objects are placed in front of the R136 cluster and are separated from it by a conspicuous amount of absorbing material, indicating that star formation has proceeded from the periphery into the interior of the region. We derive physical parameters for all PMS stars, including masses m, ages t, and mass accretion rates {\\dot{M}}{acc}. To identify reliable correlations between these parameters, which are intertwined, we use a multivariate linear regression fit of the type {log}{\\dot{M}}{acc}=a× {log}t+b× {log}m+c. The values of a and b for 30 Dor are compatible with those found in NGC 346 and NGC 602. We extend the fit to a uniform sample of 1307 PMS stars with 0.5< m/{M}⊙ < 1.5 and t< 16 {Myr} in six star-forming regions in the Large and Small Magellanic Clouds and Milky Way with metallicities in the range of 0.1-1.0 {{Z}}⊙ . We find a=-0.59+/- 0.02 and b=0.78+/- 0.08. The residuals are systematically different between the six regions and reveal a strong correlation with metallicity Z, of the type c=(-3.69+/- 0.02)-(0.30+/- 0.04)× {log}Z/{Z}⊙ . A possible interpretation of this trend is that when the metallicity is higher so is the radiation pressure, and this limits the accretion process, in both its rate and duration. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by

  7. CoRoT 223992193: A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

    NASA Astrophysics Data System (ADS)

    Gillen, E.; Aigrain, S.; McQuillan, A.; Bouvier, J.; Hodgkin, S.; Alencar, S. H. P.; Terquem, C.; Southworth, J.; Gibson, N. P.; Cody, A.; Lendl, M.; Morales-Calderón, M.; Favata, F.; Stauffer, J.; Micela, G.

    2014-02-01

    We present the discovery of CoRoT 223992193, a double-lined, detached eclipsing binary, comprising two pre-main sequence M dwarfs, discovered by the CoRoT space mission during a 23-day observation of the 3 Myr old NGC 2264 star-forming region. Using multi-epoch optical and near-IR follow-up spectroscopy with FLAMES on the Very Large Telescope and ISIS on the William Herschel Telescope we obtain a full orbital solution and derive the fundamental parameters of both stars by modelling the light curve and radial velocity data. The orbit is circular and has a period of 3.8745745 ± 0.0000014 days. The masses and radii of the two stars are 0.67 ± 0.01 and 0.495 ± 0.007 M⊙ and 1.30 ± 0.04 and 1.11-0.05+0.04 R⊙, respectively. This system is a useful test of evolutionary models of young low-mass stars, as it lies in a region of parameter space where observational constraints are scarce; comparison with these models indicates an apparent age of ~3.5-6 Myr. The systemic velocity is within 1σ of the cluster value which, along with the presence of lithium absorption, strongly indicates cluster membership. The CoRoT light curve also contains large-amplitude, rapidly evolving out-of-eclipse variations, which are difficult to explain using starspots alone. The system's spectral energy distribution reveals a mid-infrared excess, which we model as thermal emission from a small amount of dust located in the inner cavity of a circumbinary disk. In turn, this opens up the possibility that some of the out-of-eclipse variability could be due to occultations of the central stars by material located at the inner edge or in the central cavity of the circumbinary disk. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESAs RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  8. Secular Resonances During Main-Sequence and Post-Main-Sequence Planetary System Dynamics

    NASA Astrophysics Data System (ADS)

    Smallwood, Jeremy L.

    We investigate gravitational perturbations of an asteroid belt by secular resonances. We ap- ply analytic and numerical models to main-sequence and post-main-sequence planetary systems. First, we investigate how the asteroid impact rate on the Earth is affected by the architecture of the planetary system. We find that the nu6 resonance plays an important role in the asteroid collision rate with the Earth. Compared to exoplanetary systems, the solar system is somewhat special in its lack of a super-Earth mass planet in the inner solar system. We therefore consider the effects of the presence of a super-Earth in the terrestrial planet region. We find a significant effect for super-Earths with a mass of around 10 M_{Earth} and a separation greater than about 0.7 AU. These results have implications for the habitability of exoplanetary systems. Secondly, we model white dwarf pollution by asteroids from secular resonances. In the past few decades, observations have revealed signatures of metals polluting the atmospheres of white dwarfs that require a continu- ous accretion of asteroids. We show that secular resonances driven by two outer companions can provide a source of pollution if an inner terrestrial planet is engulfed during the red-giant branch phase. Secular resonances may be a viable mechanism for the pollution of white dwarfs in a variety of exoplanetary system architectures including systems with two giant planets and systems with one giant planet and a binary star companion.

  9. The double main sequence of Omega Centauri

    NASA Astrophysics Data System (ADS)

    Bedin, L. R.; Piotto, G.; Anderson, J.; King, I. R.; Cassisi, S.; Momany, Y.

    Recent, high precision photometry of Omega Centauri, the biggest Galactic globular cluster, has been obtained with Hubble Space Telescope (HST). The color magnitude diagram reveals an unexpected bifurcation of colors in the main sequence (MS). The newly found double MS, the multiple turnoffs and subgiant branches, and other sequences discovered in the past along the red giant branch of this cluster add up to a fascinating but frustrating puzzle. Among the possible explanations for the blue main sequence an anomalous overabundance of helium is suggested. The hypothesis will be tested with a set of FLAMES@VLT data we have recently obtained (ESO DDT program), and with forthcoming ACS@HST images. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  10. The ultracool dwarf DENIS-P J104814.7-395606. Chromospheres and coronae at the low-mass end of the main-sequence

    NASA Astrophysics Data System (ADS)

    Stelzer, B.; Alcalá, J.; Biazzo, K.; Ercolano, B.; Crespo-Chacón, I.; López-Santiago, J.; Martínez-Arnáiz, R.; Schmitt, J. H. M. M.; Rigliaco, E.; Leone, F.; Cupani, G.

    2012-01-01

    Context. Several diagnostics ranging from the radio to the X-ray band are suitable for investigating the magnetic activity of late-type stars. Empirical connections between the emission at different wavelengths place constraints on the nature and efficiency of the emission mechanism and the physical conditions in different atmospheric layers. The activity of ultracool dwarfs, at the low-mass end of the main-sequence, is poorly understood. Aims: We perform a multi-wavelength study of one of the nearest M9 dwarfs, DENIS-P J104814.7-395606 (4 pc), to examine its position within the group of magnetically active ultracool dwarfs, and, in general, advance our understanding of these objects by comparing them to early-M type dwarf stars and the Sun. Methods: We obtained an XMM-Newton observation of DENIS-P J104814.7-395606 and a broad-band spectrum from the ultraviolet to the near-infrared with X-Shooter. From this dataset, we derive the X-ray properties, stellar parameters, kinematics, and the emission-line spectrum tracing chromospheric activity. We integrate these data by compiling the activity parameters of ultracool dwarfs from the literature. Results: Our deep XMM-Newton observation provides the first X-ray detection of DENIS-P J104814.7-395606 (log Lx = 25.1), as well as the first measurement of its V band brightness (V = 17.35 mag). The flux-flux relations between X-ray and chromospheric activity indicators are here for the first time extended into the regime of the ultracool dwarfs. The approximate agreement of DENIS-P J104814.7-395606 and other ultracool dwarfs with flux-flux relations for early-M dwarfs suggests that the same heating mechanisms work in the atmospheres of ultracool dwarfs, albeit weaker as judged from their lower fluxes. The observed Balmer decrements of DENIS 1048-3956 are compatible with optically thick plasma in local thermal equilibrium (LTE) at low, nearly photospheric temperature or optically thin LTE plasma at 20 000 K. Describing the

  11. Post-main-sequence planetary system evolution

    PubMed Central

    Veras, Dimitri

    2016-01-01

    The fates of planetary systems provide unassailable insights into their formation and represent rich cross-disciplinary dynamical laboratories. Mounting observations of post-main-sequence planetary systems necessitate a complementary level of theoretical scrutiny. Here, I review the diverse dynamical processes which affect planets, asteroids, comets and pebbles as their parent stars evolve into giant branch, white dwarf and neutron stars. This reference provides a foundation for the interpretation and modelling of currently known systems and upcoming discoveries. PMID:26998326

  12. The Infrared Eye of the Wide-Field Camera 3 on the Hubble Space Telescope Reveals Multiple Main Sequences of Very Low Mass Stars in NGC 2808

    NASA Astrophysics Data System (ADS)

    Milone, A. P.; Marino, A. F.; Cassisi, S.; Piotto, G.; Bedin, L. R.; Anderson, J.; Allard, F.; Aparicio, A.; Bellini, A.; Buonanno, R.; Monelli, M.; Pietrinferni, A.

    2012-08-01

    We use images taken with the infrared channel of the Wide Field Camera 3 on the Hubble Space Telescope to study the multiple main sequences (MSs) of NGC 2808. Below the turnoff, the red, the middle, and the blue MS, previously detected from visual-band photometry, are visible over an interval of about 3.5 F160W magnitudes. The three MSs merge together at the level of the MS bend. At fainter magnitudes, the MS again splits into two components containing ~65% and ~35% of stars, with the most-populated MS being the bluest one. Theoretical isochrones suggest that the latter is connected to the red MS discovered in the optical color-magnitude diagram (CMD) and hence corresponds to the first stellar generation, having primordial helium and enhanced carbon and oxygen abundances. The less-populated MS in the faint part of the near-IR CMD is helium-rich and poor in carbon and oxygen, and it can be associated with the middle and the blue MS of the optical CMD. The finding that the photometric signature of abundance anti-correlation is also present in fully convective MS stars reinforces the inference that they have a primordial origin. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  13. Main sequence models for massive zero-metal stars

    NASA Technical Reports Server (NTRS)

    Cary, N.

    1974-01-01

    Zero-age main-sequence models for stars of 20, 10, 5, and 2 solar masses with no heavy elements are constructed for three different possible primordial helium abundances: Y=0.00, Y=0.23, and Y=0.30. The latter two values of Y bracket the range of primordial helium abundances cited by Wagoner. With the exceptions of the two 20 solar mass models that contain helium, these models are found to be self-consistent in the sense that the formation of carbon through the triple-alpha process during premain sequence contraction is not sufficient to bring the CN cycle into competition with the proton-proton chain on the ZAMS. The zero-metal models of the present study have higher surface and central temperatures, higher central densities, smaller radii, and smaller convective cores than do the population I models with the same masses.

  14. Spectroscopic evolution of massive stars on the main sequence

    NASA Astrophysics Data System (ADS)

    Martins, F.; Palacios, A.

    2017-02-01

    Context. The evolution of massive stars depends on several parameters, and the relation between different morphological types is not fully constrained. Aims: We aim to provide an observational view of evolutionary models in the Hertzsprung-Russell diagram, on the main sequence. This view should help compare observations and model predictions. Methods: We first computed evolutionary models with the code STAREVOL for initial masses between 15 and 100 M⊙. We subsequently calculated atmosphere models at specific points along the evolutionary tracks, using the code CMFGEN. Synthetic spectra obtained in this way were classified as if they were observational data: we assigned them a spectral type and a luminosity class. We tested our spectral classification by comparison to observed spectra of various stars with different spectral types. We also compared our results with empirical data of a large number of OB stars. Results: We obtain spectroscopic sequences along evolutionary tracks. In our computations, the earliest O stars (O2-3.5) appear only above 50 M⊙. For later spectral types, a similar mass limit exists, but is lower. A luminosity class V does not correspond to the entire main sequence. This only holds for the 15 M⊙ track. As mass increases, a larger portion of the main sequence is spent in luminosity class III. Above 50 M⊙, supergiants appear before the end of core-hydrogen burning. Dwarf stars (luminosity class V) do not occur on the zero-age main sequence above 80 M⊙. Consequently, the distribution of luminosity class V in the HR diagram is not a diagnostic of the length of the main sequence (above 15 M⊙) and cannot be used to constrain the size of the convective core. The distribution of dwarfs and giants in the HR diagram that results from our calculations agrees well with the location of stars analyzed by means of quantitative spectroscopy. For supergiants, there is a slight discrepancy in the sense that luminosity class I is observed slightly

  15. High-precision Radio and Infrared Astrometry of LSPM J1314+1320AB. II. Testing Pre-main-sequence Models at the Lithium Depletion Boundary with Dynamical Masses

    NASA Astrophysics Data System (ADS)

    Dupuy, Trent J.; Forbrich, Jan; Rizzuto, Aaron; Mann, Andrew W.; Aller, Kimberly; Liu, Michael C.; Kraus, Adam L.; Berger, Edo

    2016-08-01

    We present novel tests of pre-main-sequence models based on individual dynamical masses for the M7 binary LSPM J1314+1320AB. Joint analysis of Keck adaptive optics astrometric monitoring along with Very Long Baseline Array radio data from a companion paper yield component masses of 92.8 ± 0.6 M Jup (0.0885 ± 0.0006 M ⊙) and 91.7 ± 1.0 M Jup (0.0875 ± 0.0010 M ⊙) and a parallactic distance of 17.249 ± 0.013 pc. We find component luminosities consistent with the system being coeval at 80.8 ± 2.5 Myr, according to BHAC15 evolutionary models. The presence of lithium is consistent with model predictions, marking the first test of the theoretical lithium depletion boundary using ultracool dwarfs of known mass. However, we find that the evolutionary model-derived average effective temperature (2950 ± 5 K) is 180 K hotter than that given by a spectral type-{T}{eff} relation based on BT-Settl models (2770 ± 100 K). We suggest that the dominant source of this discrepancy is model radii being too small by ≈13%. In a test mimicking the typical application of models by observers, we derive masses on the H-R diagram using luminosity and BT-Settl temperature. The estimated masses are lower by {46}-19+16 % (2.0σ) than we measure dynamically and would imply that this is a system of ≈50 M Jup brown dwarfs, highlighting the large systematic errors possible in H-R diagram properties. This is the first time masses have been measured for ultracool (≥M6) dwarfs displaying spectral signatures of low gravity. Based on features in the infrared, LSPM J1314+1320AB appears to have higher gravity than typical Pleiades and AB Dor members, opposite the expectation given its younger age. The components of LSPM J1314+1320AB are now the nearest, lowest mass pre-main-sequence stars with direct mass measurements. 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

  16. Lithium Depletion in Fully Convective Pre-Main-Sequence Stars

    NASA Astrophysics Data System (ADS)

    Bildsten, Lars; Brown, Edward F.; Matzner, Christopher D.; Ushomirsky, Greg

    1997-06-01

    We present an analytic calculation of the thermonuclear depletion of lithium in contracting, fully convective, pre-main-sequence stars of mass M <~ 0.5 M⊙. Previous numerical work relies on still uncertain physics (atmospheric opacities and convection, in particular) to calculate the effective temperature as a unique function of stellar mass. We assume that the star's effective temperature, Teff, is fixed during Hayashi contraction and allow its actual value to be a free parameter constrained by observation. Using this approximation, we compute lithium burning analytically and explore the dependence of lithium depletion on Teff, M, and composition. Our calculations yield the radius, age, and luminosity of a pre-main-sequence star as a function of lithium depletion. This allows for more direct comparisons with observations of lithium-depleted stars. Our results agree with those numerical calculations that explicitly determine stellar structure during Hayashi contraction. In agreement with Basri, Marcy, & Graham, we show that the absence of lithium in the Pleiades star HHJ 3 implies that it is older than 100 Myr. We also suggest a generalized method for dating Galactic clusters younger than 100 Myr (i.e., those with contracting stars of M >~ 0.08 M⊙) and for constraining the masses of lithium-depleted stars.

  17. Pre-main sequence variables in young cluster Stock 18

    NASA Astrophysics Data System (ADS)

    Sinha, Tirthendu; Sharma, Saurabh; Pandey, Rakesh; Pandey, Anil Kumar

    2018-04-01

    We have carried out multi-epoch deep I band photometry of the open cluster Stock 18 to search for variable stars in star forming regions. In the present study, we identified 65 periodic and 217 non-periodic variable stars. The periods of most of the periodic variables are between 2 hours to 15 days and their magnitude varies between 0.05 to 0.6 mag. We have derived spectral energy distributions for 48 probable pre-main sequence variables. Their average age and mass are 2.7 ± 0.3 Myrs and 2.7 ± 0.2 Mo, respectively.

  18. Orbital motion in pre-main sequence binaries

    SciTech Connect

    Schaefer, G. H.; Prato, L.; Simon, M.

    2014-06-01

    We present results from our ongoing program to map the visual orbits of pre-main sequence (PMS) binaries in the Taurus star forming region using adaptive optics imaging at the Keck Observatory. We combine our results with measurements reported in the literature to analyze the orbital motion for each binary. We present preliminary orbits for DF Tau, T Tau S, ZZ Tau, and the Pleiades binary HBC 351. Seven additional binaries show curvature in their relative motion. Currently, we can place lower limits on the orbital periods for these systems; full solutions will be possible with more orbital coverage. Five othermore » binaries show motion that is indistinguishable from linear motion. We suspect that these systems are bound and might show curvature with additional measurements in the future. The observations reported herein lay critical groundwork toward the goal of measuring precise masses for low-mass PMS stars.« less

  19. Pre-main-sequence disk accretion in Z Canis Majoris

    NASA Technical Reports Server (NTRS)

    Hartmann, L.; Kenyon, S. J.; Hewett, R.; Edwards, S.; Strom, K. M.; Strom, S. E.; Stauffer, J. R.

    1989-01-01

    It is suggested that the pre-main-sequence object Z CMa is a luminous accretion disk, similar in many respects to the FU Orionis variables. Z CMa shows the broad, doubled optical absorption lines expected from a rapidly rotating accretion disk. The first overtone CO absorption detected in Z CMa is blue-shifted, suggesting line formation in a disk wind. Accretion at rates about 0.001 solar mass/yr over 100 yr is required to explain the luminosity of Z CMa. The large amount of material accreted (0.1 solar mass/yr) indicates that Z CMa is in a very early stage of stellar evolution, possibly in an initial phase of massive disk accretion.

  20. The dynamics of post-main sequence planetary systems

    NASA Astrophysics Data System (ADS)

    Mustill, Alexander James

    2017-06-01

    The study of planetary systems after their host stars have left the main sequence is of fundamental importance for exoplanet science, as the most direct determination of the compositions of extra-Solar planets, asteroids and comets is in fact made by an analysis of the elemental abundances of the remnants of these bodies accreted into the atmospheres of white dwarfs.To understand how the accreted bodies relate to the source populations in the planetary system, and to model their dynamical delivery to the white dwarf, it is necessary to understand the effects of stellar evolution on bodies' orbits. On the red giant branch (RGB) and asymptotic giant branch (AGB) prior to becoming a white dwarf, stars expand to a large size (>1 au) and are easily deformed by orbiting planets, leading to tidal energy dissipation and orbital decay. They also lose half or more of their mass, causing the expansion of bodies' orbits. This mass loss increases the planet:star mass ratio, so planetary systems orbiting white dwarfs can be much less stable than those orbiting their main-sequence progenitors. Finally, small bodies in the system experience strong non-gravitational forces during the RGB and AGB: aerodynamic drag from the mass shed by the star, and strong radiation forces as the stellar luminosity reaches several thousand Solar luminosities.I will review these effects, focusing on planet--star tidal interactions and planet--asteroid interactions, and I will discuss some of the numerical challenges in modelling systems over their entire lifetimes of multiple Gyr.

  1. Spatially Resolved Star Formation Main Sequence of Galaxies

    NASA Astrophysics Data System (ADS)

    Cano-Díaz, M.; Sánchez, S. F.; Zibetti, S.; Ascaribar, Y.; Bland-Hawthorn, J.; Ziegler, B.; González-Delgado, R. M.; Walcher, C. J.; García-Benito, R.; Mast, D.; Mendoza-Pérez, M. A.; Falcón-Barroso, J.; Galbany, L.; Husemann, B.; Kehring, C.; Marino, R. A.; Sánchez-Blázquez, P.; López-Cobá, C.; López-Sánchez, A. R.; Vilchez, J. M.

    2016-06-01

    The relation known as Star Formation Main Sequence (SFMS) of galaxies is defined in terms of stellar mass and star formation rate. This approximately linear relation has been proven to be tight and holds for several star formation indicators at local and at high redshifts. In this talk I will show recent results about our first attempts to study the Spatially Resolved SFMS, using integral field spectroscopic data, coming primarily from the CALIFA survey. I will present as a main result that a local SFMS is found with a slope and zero point of 0.72 +/ 0.04, and -7.95 +/ 0.29 respectively. I will also discuss the influence of characteristics such as environment and morphology in the relation. Finally I will present some extensions of these results for data com in from the MaNGA survey.

  2. Infalling Planetesimals in Pre-Main Sequence Stellar Systems

    NASA Technical Reports Server (NTRS)

    Grady, Carol A.; Sitko, Michael L.; Russell, Ray W.; Lynch, David K.; Hanner, Martha S.; Perez, Mario R.; Bjorkman, Karen S.; DeWinter, Dolf

    1999-01-01

    These are exciting times in the study of planetary system formation with a steadily expanding inventory of exo-planet detections, and imaging of dust disks around nearby young and main sequence stars. While these discoveries imply that our Solar System is far from unique, linking the data for the protoplanetary and debris disks to mature planetary systems requires a demonstration that disk evolution proceeds via planetesimal production and growth to the formation of planets. Theoretical studies of planet formation indicate that planetesimals grow, via runaway accretion, to lunar-sized (approx. = 2000 km) embryos in 10(exp 5) years. Recent gas giant planet formation studies have suggested that most of the action in planet formation occurs over 1-16 Myr, with formation of planets similar to Jupiter in t less than 10 Myr, within the time interval that infrared (IR) and optical emission line studies have demonstrated that circumstellar material remains detectable around both solar mass and intermediate mass stars. Direct imaging of exo-planetesimals is not feasible with current and foreseeable technology, since such bodies have substantially less surface area than micron-sized grains distributed in a disk, and thus are inefficient IR emitters. However, such bodies may be indirectly detectable.

  3. On the Statistical Properties of the Lower Main Sequence

    NASA Astrophysics Data System (ADS)

    Angelou, George C.; Bellinger, Earl P.; Hekker, Saskia; Basu, Sarbani

    2017-04-01

    Astronomy is in an era where all-sky surveys are mapping the Galaxy. The plethora of photometric, spectroscopic, asteroseismic, and astrometric data allows us to characterize the comprising stars in detail. Here we quantify to what extent precise stellar observations reveal information about the properties of a star, including properties that are unobserved, or even unobservable. We analyze the diagnostic potential of classical and asteroseismic observations for inferring stellar parameters such as age, mass, and radius from evolutionary tracks of solar-like oscillators on the lower main sequence. We perform rank correlation tests in order to determine the capacity of each observable quantity to probe structural components of stars and infer their evolutionary histories. We also analyze the principal components of classic and asteroseismic observables to highlight the degree of redundancy present in the measured quantities and demonstrate the extent to which information of the model parameters can be extracted. We perform multiple regression using combinations of observable quantities in a grid of evolutionary simulations and appraise the predictive utility of each combination in determining the properties of stars. We identify the combinations that are useful and provide limits to where each type of observable quantity can reveal information about a star. We investigate the accuracy with which targets in the upcoming TESS and PLATO missions can be characterized. We demonstrate that the combination of observations from GAIA and PLATO will allow us to tightly constrain stellar masses, ages, and radii with machine learning for the purposes of Galactic and planetary studies.

  4. Dynamical Mass Constraints on Low-Mass Pre-Main-Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion With a 1.0 M Primary and a 0.7 M Secondary

    DTIC Science & Technology

    2003-12-30

    distance assumed. As noted by Simon et al. (2000), the distance uncertainty to any particular star in Taurus may be as large as 15%, manifesting itself...Ori A and LkCa 15 (a single star in Taurus ), which have identical masses and are at identical positions in the H-R diagram. But, disconcertingly, we

  5. Properties of the main-sequence eclipsing binary UZ Draconis

    SciTech Connect

    Lacy, C.H.; Gulmen, O.; Gudur, N.

    1989-03-01

    The fundamental properties of the main-sequence binary, UZ Dra, are determined from observational data. Photoelectric radial-velocity measurements (Imbert, 1986), spectroscopic data obtained with solid-state array detectors, and B,V photoelectric light curves of the binary are examined. The properties of the stars in the binary are presented and compared with those of other F-type main-sequence binaries listed by Popper (1980). 26 references.

  6. HABITABLE ZONES OF POST-MAIN SEQUENCE STARS

    SciTech Connect

    Ramirez, Ramses M.; Kaltenegger, Lisa

    2016-05-20

    Once a star leaves the main sequence and becomes a red giant, its Habitable Zone (HZ) moves outward, promoting detectable habitable conditions at larger orbital distances. We use a one-dimensional radiative-convective climate and stellar evolutionary models to calculate post-MS HZ distances for a grid of stars from 3700 to 10,000 K (∼M1 to A5 stellar types) for different stellar metallicities. The post-MS HZ limits are comparable to the distances of known directly imaged planets. We model the stellar as well as planetary atmospheric mass loss during the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) phases for super-Moons tomore » super-Earths. A planet can stay between 200 million years up to 9 Gyr in the post-MS HZ for our hottest and coldest grid stars, respectively, assuming solar metallicity. These numbers increase for increased stellar metallicity. Total atmospheric erosion only occurs for planets in close-in orbits. The post-MS HZ orbital distances are within detection capabilities of direct imaging techniques.« less

  7. On the Statistical Properties of the Lower Main Sequence

    SciTech Connect

    Angelou, George C.; Bellinger, Earl P.; Hekker, Saskia

    2017-04-20

    Astronomy is in an era where all-sky surveys are mapping the Galaxy. The plethora of photometric, spectroscopic, asteroseismic, and astrometric data allows us to characterize the comprising stars in detail. Here we quantify to what extent precise stellar observations reveal information about the properties of a star, including properties that are unobserved, or even unobservable. We analyze the diagnostic potential of classical and asteroseismic observations for inferring stellar parameters such as age, mass, and radius from evolutionary tracks of solar-like oscillators on the lower main sequence. We perform rank correlation tests in order to determine the capacity of each observablemore » quantity to probe structural components of stars and infer their evolutionary histories. We also analyze the principal components of classic and asteroseismic observables to highlight the degree of redundancy present in the measured quantities and demonstrate the extent to which information of the model parameters can be extracted. We perform multiple regression using combinations of observable quantities in a grid of evolutionary simulations and appraise the predictive utility of each combination in determining the properties of stars. We identify the combinations that are useful and provide limits to where each type of observable quantity can reveal information about a star. We investigate the accuracy with which targets in the upcoming TESS and PLATO missions can be characterized. We demonstrate that the combination of observations from GAIA and PLATO will allow us to tightly constrain stellar masses, ages, and radii with machine learning for the purposes of Galactic and planetary studies.« less

  8. The Main-Sequence Stars of the Sagittarius Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Fahlman, G. G.; Mandushev, G.; Richer, H. B.; Thompson, I. B.; Sivaramakrishnan, A.

    1996-03-01

    The Sagittarius dwarf galaxy (SDG) is visible in the background field of the globular cluster M55. We present a deep VI color-magnitude diagram (CMD) of M55, which shows a prominent sequence of stars some 3.5 mag below the cluster main sequence. Through a comparison with a similar CMD for the globular cluster M4, we show that the M55 background field is not the Galactic bulge or spheroid. The SDG main sequence is almost as blue as that of M55 and thus, if it is metal rich, it must be younger than M55, a typical old Galactic globular cluster. The results from isochrone fitting indicate that the age of the SDG is 10--14 Gyr, similar to the ages inferred for the two associated globular clusters Ter 7 and Arp 2.

  9. PRE-MAIN-SEQUENCE STARS IN THE CEPHEUS FLARE REGION

    SciTech Connect

    Kun, Maria; Balog, Zoltan; Kenyon, Scott J.

    2009-12-01

    We present results of optical spectroscopic and BVR {sub C} I {sub C} photometric observations of 77 pre-main-sequence (PMS) stars in the Cepheus flare region. A total of 64 of these are newly confirmed PMS stars, originally selected from various published candidate lists. We estimate effective temperatures and luminosities for the PMS stars, and comparing the results with PMS evolutionary models, we estimate stellar masses of 0.2-2.4 M {sub sun} and stellar ages of 0.1-15 Myr. Among the PMS stars, we identify 15 visual binaries with separations of 2-10 arcsec. From archival IRAS, Two Micron All Sky Survey, and Spitzermore » data, we construct their spectral energy distributions (SEDs) and classify 5% of the stars as Class I, 10% as Flat SED, 60% as Class II, and 3% as Class III young stellar objects. We identify 12 classical T Tauri stars and two weak-line T Tauri stars as members of NGC 7023, with a mean age of 1.6 Myr. The 13 PMS stars associated with L1228 belong to three small aggregates: RNO 129, L1228A, and L1228S. The age distribution of the 17 PMS stars associated with L1251 suggests that star formation has propagated with the expansion of the Cepheus flare shell. We detect sparse aggregates of {approx}6-7 Myr old PMS stars around the dark clouds L1177 and L1219, at a distance of {approx}400 pc. Three T Tauri stars appear to be associated with the Herbig Ae star SV Cep at a distance of 600 pc. Our results confirm that the molecular complex in the Cepheus flare region contains clouds of various distances and star-forming histories.« less

  10. Finding the Onset of Convection in Main Sequence Stars

    NASA Technical Reports Server (NTRS)

    Simon, Theodore

    2003-01-01

    The primary goal of the work performed under this grant was to locate, if possible, the onset of subphotospheric convection zones in normal main sequence stars by using the presence of emission in high temperature lines in far ultraviolet spectra from the FUSE spacecraft as a proxy for convection. The change in stellar structure represented by this boundary between radiative and convective stars has always been difficult to find by other empirical means. A search was conducted through observations of a sample of A-type stars, which were somewhat hotter and more massive than the Sun, and which were carefully chosen to bridge the theoretically expected radiative/convective boundary line along the main sequence.

  11. The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

    NASA Astrophysics Data System (ADS)

    Medling, Anne M.; Cortese, Luca; Croom, Scott M.; Green, Andrew W.; Groves, Brent; Hampton, Elise; Ho, I.-Ting; Davies, Luke J. M.; Kewley, Lisa J.; Moffett, Amanda J.; Schaefer, Adam L.; Taylor, Edward; Zafar, Tayyaba; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V.; Brough, Sarah; Bryant, Julia J.; Catinella, Barbara; Cecil, Gerald; Colless, Matthew; Couch, Warrick J.; Drinkwater, Michael J.; Driver, Simon P.; Federrath, Christoph; Foster, Caroline; Goldstein, Gregory; Goodwin, Michael; Hopkins, Andrew; Lawrence, J. S.; Leslie, Sarah K.; Lewis, Geraint F.; Lorente, Nuria P. F.; Owers, Matt S.; McDermid, Richard; Richards, Samuel N.; Sharp, Robert; Scott, Nicholas; Sweet, Sarah M.; Taranu, Dan S.; Tescari, Edoardo; Tonini, Chiara; van de Sande, Jesse; Walcher, C. Jakob; Wright, Angus

    2018-04-01

    We present the ˜800 star formation rate maps for the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey based on H α emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1. We mask out spaxels contaminated by non-stellar emission using the [O III]/H β, [N II]/H α, [S II]/H α, and [O I]/H α line ratios. Using these maps, we examine the global and resolved star-forming main sequences of SAMI galaxies as a function of morphology, environmental density, and stellar mass. Galaxies further below the star-forming main sequence are more likely to have flatter star formation profiles. Early-type galaxies split into two populations with similar stellar masses and central stellar mass surface densities. The main-sequence population has centrally concentrated star formation similar to late-type galaxies, while galaxies >3σ below the main sequence show significantly reduced star formation most strikingly in the nuclear regions. The split populations support a two-step quenching mechanism, wherein halo mass first cuts off the gas supply and remaining gas continues to form stars until the local stellar mass surface density can stabilize the reduced remaining fuel against further star formation. Across all morphologies, galaxies in denser environments show a decreased specific star formation rate from the outside in, supporting an environmental cause for quenching, such as ram-pressure stripping or galaxy interactions.

  12. The lower main sequence and the nature of secondary stars in ultracompact binaries

    NASA Technical Reports Server (NTRS)

    Rappaport, S.; Joss, P. C.

    1984-01-01

    The possible nature of the secondary stars in ultracompact binary stellar systems (with orbital periods of less than about 1 hr) are systematically investigated. Using a simplified stellar evolution code, which assumes isentropic stellar models, nearly 3000 separate models for hydrogen-burning main-sequence stars with masses less than 0.3 solar mass are generated. The effects of the (homogeneous) chemical composition on the properties of such stars and in, particular, on the minimum main-sequence mass are explored in detail. It is found that this minimum mass is a sensitive function of the hydrogen content and can be as small as 0.035 solar mass. The properties of fully degenerate low-mass stars, as well as low-mass stars that are not in thermal equilibrium are also studied. In particular, it is shown that the thermal time scale of such nonequilibrium stars may exceed 10 billion yr. The results also confirm the existence of a second branch of the main sequence and shed new light on the thermal instability of this branch. The available observational information on the three known ultracompact binary systems (4U 1626-67, G61-29, 4U 1916-05) is summarized, and the results of the stellar model calculations are combined with the empirical results to place constraints on the properties of the secondary stars.

  13. Discovery of five pre-main-sequence binaries in Taurus

    NASA Technical Reports Server (NTRS)

    Chen, W. P.; Simon, M.; Longmore, A. J.; Howell, R. R.; Benson, J. A.

    1990-01-01

    The progress of an infrared K band lunar occultation search for binaries among premain-sequence stars is reported. From the fall of 1986 to the fall of 1989, 13 objects have been observed, all in the Taurus star-forming region. Five new binaries have been discovered: DF Tau, DI Tau, FS Tau (Haro 6-5) A, FV Tau (Haro 6-8), and FW Tau, with projected separations ranging from 0.01 to 0.57 arcsec. Including results reported previously, a total of 31 objects, 21 in Taurus and 10 in Ophiuchus, have been surveyed and nine double systems have been found. The detected binary frequency (0.29) seems consistent with that of the solar-type main-sequence field stars.

  14. Evolution of Pre-Main Sequence Accretion Disks

    NASA Technical Reports Server (NTRS)

    Hartmann, Lee W.

    2003-01-01

    The aim of this project is to develop a comprehensive global picture of the physical conditions in, and evolutionary timescales of, pre-main sequence accretion disks. The results of this work will help constrain the initial conditions for planet formation. To this end we are developing much larger samples of 3-10 Myr-old stars to provide better empirical constraints on protoplanetary disk evolution; measuring disk accretion rates in these systems; and constructing detailed model disk structures consistent with observations to infer physical conditions such as grain growth in protoplanetary disks.

  15. Cool circumstellar matter around nearby main-sequence stars

    NASA Technical Reports Server (NTRS)

    Walker, H. J.; Wolstencroft, R. D.

    1988-01-01

    Stars are presented which have characteristics similar to Vega and other main-sequence stars with cool dust disks, based on the IRAS Point Source Catalog fluxes. The objects are selected to have a 60-micron/100-micron ratio similar to Vega, Beta Pic, Alpha PsA, and Epsilon Eri, and they are also required to show evidence of extension in the IRAS Working Survey Database. The fluxes are modeled using a blackbody energy distribution. The temperatures derived range from 50 to 650 K. The diameters of the dust disks observed by IRAS are estimated.

  16. Environmental impact analysis for the main accidental sequences of ignitor

    SciTech Connect

    Carpignano, A.; Francabandiera, S.; Vella, R.

    1996-12-31

    A safety analysis study has been applied to the Ignitor machine using Probabilistic Safety Assessment. The main initiating events have been identified, and accident sequences have been studied by means of traditional methods such as Failure Mode and Effect Analysis (FMEA), Fault Trees (FT) and Event Trees (ET). The consequences of the radioactive environmental releases have been assessed in terms of Effective Dose Equivalent (EDEs) to the Most Exposed Individuals (MEI) of the chosen site, by means of a population dose code. Results point out the low enviromental impact of the machine. 13 refs., 1 fig., 3 tabs.

  17. Evolution of Pre-Main Sequence Accretion Disks

    NASA Technical Reports Server (NTRS)

    Hartmann, Lee W.

    2004-01-01

    The aim of this project is to develop a comprehensive global picture of the physical conditions in, and evolutionary timescales of, pre-main sequence accretion disks. The results of this work will help constrain the initial conditions for planet formation. To this end we are developing much larger samples of 3-10 Myr-old stars to provide better empirical constraints on protoplanetary disk evolution; measuring disk accretion rates in these systems; and constructing detailed model disk structures consistent with observations to infer physical conditions such as grain growth in protoplanetary disks.

  18. Cool circumstellar matter around nearby main-sequence stars

    SciTech Connect

    Walker, H.J.; Wolstencroft, R.D.

    1988-12-01

    Stars are presented which have characteristics similar to Vega and other main-sequence stars with cool dust disks, based on the IRAS Point Source Catalog fluxes. The objects are selected to have a 60-micron/100-micron ratio similar to Vega, Beta Pic, Alpha PsA, and Epsilon Eri, and they are also required to show evidence of extension in the IRAS Working Survey Database. The fluxes are modeled using a blackbody energy distribution. The temperatures derived range from 50 to 650 K. The diameters of the dust disks observed by IRAS are estimated. 23 references.

  19. Characterization of Detached Main Sequence Binaries Observed by Kepler, SDSS(APOGEE) and Gaia

    NASA Astrophysics Data System (ADS)

    Solis, Christina Oleander; Mason, Paul A.

    2017-01-01

    In addition to finding planets, the Kepler Observatory obtained high precision light curves of eclipsing binaries that have subsequently been observed by SDSS and Gaia. Main sequence eclipsing binaries are important laboratories for stellar astrophysics. The determination of precise temperatures, radii, masses, and orbital parameters constrain evolution theory. We examined 28 main sequence binaries observed using Kepler, SDSS(APOGEE) and Gaia. Combining observed astrometric, photometric, and spectroscopic data places strong constraints on stellar and binary characteristics. We compare derived parameters with model calculations of these binaries and present preliminary results.

  20. Granulation in a main-sequence F-type star

    NASA Technical Reports Server (NTRS)

    Nelson, G. D.

    1980-01-01

    The modal approach developed by Nelson and Musman (1977) is used to investigate convection in an F-type main-sequence star (effective temperature of 7300 K, g = 10,000 cm per sec per sec). The convective velocities and intensity contrasts are found to be larger than in the sun. Even though the convective flux is less than 1% of the total flux at a mean optical depth of unity, the spectral-energy distribution is strongly reddened as a result of the fluctuating opacity. This has important implications in the conversion scale from observed colors to effective temperature. The scale of the surface granulation is expected to be in the range 1000-5000 km. Calculations of the combined H-He I and He II convection zones support the prediction of Toomre et al. (1976) that the stable region between the zones is well mixed

  1. Pre- and main-sequence evolution of solar activity

    NASA Technical Reports Server (NTRS)

    Walter, Frederick M.; Barry, Don C.

    1991-01-01

    The magnetic activity on single solarlike stars declines with stellar age. This has important consequences for the influence of the sun on the early solar system. What is meant by stellar activity, and how it is measured, is reviewed. Stellar activity on the premain-sequence phase of evolution is discussed; the classical T Tauri stars do not exhibit solarlike activity, while the naked T Tauri stars do. The emission surface fluxes of the naked T Tauri stars are similar to those of the youngest main-sequence G stars. The best representation for solarlike stars is a decay proportional to exp(A x t exp 0.5), where A is a function of line excitation temperature. From these decay laws, one can determine the interdependences of the activity, age, and rotation periods. The fluxes of ionizing photons at the earth early in its history are discussed; there was sufficient fluence to account for the observed isotopic ratios of the noble gases.

  2. Pre-Main-Sequence Star Candidates in the Bar of the Large Magellanic Cloud

    PubMed

    Beaulieu; Lamers; Grison; Julien; Lanciaux; Ferlet; Vidal-Madjar; Bertin; Maurice; Prevot; Gry; Guibert; Moreau; Tajhmady; Aubourg; Bareyre; de Kat J; Gros; Laurent; Lachieze-Rey; Lesquoy; Magneville; Milsztajn; Moscoso; Queinnec; Renault; Rich; Spiro; Vigroux; Zylberajch; Ansari; Cavalier; Moniez

    1996-05-17

    Candidate pre-main-sequence stars were observed in the bar of the Large Magellanic Cloud during the search for dark matter in the galactic halo. Seven blue stars of apparent visual magnitude 15 to 17 had irregular photometric variations and hydrogen emission lines in their optical spectra, which suggested that these stars are pre-main-sequence stars of about 10 solar masses. These stars are slightly more massive and definitely more luminous than are Herbig AeBe pre-main-sequence stars in our own galaxy. Continued observations of these very young stars from another galaxy, which are probably at the pre-hydrogen-burning stage, should provide important clues about early stages of star formation.

  3. Lithium evolution in metal-poor stars: from Pre-Main Sequence to the Spite Plateau

    NASA Astrophysics Data System (ADS)

    Fu, Xiaoting; Bressan, Alessandro; Molaro, Paolo; Marigo, Paola

    2015-08-01

    Lithium abundance derived in metal-poor main sequence stars is about three times lower than the value of primordial Li predicts by the standard Big Bang nucleosynthesis when the baryon density is taken from the CMB or the deuterium measurements. This disagreement is generally referred as the Li problem. We here reconsider the stellar Li evolution from the pre-main sequence to the end of the main sequence phase by introducing the effects of convective overshooting and residual mass accretion. We show that 7Li could be significantly depleted by convective overshooting in the PMS phase and then partially restored in the stellar atmosphere by a tail of matter accretion which follows the Li depletion phase and that could be regulated by EUV photo-evaporation. By considering the conventional nuclear burning and microscopic diffusion along the main sequence we can reproduce the Spite plateau for stars with m0 = 0.62 - 0.80 M⊙ and the Li decline branch for lower mass dwarfs e.g, m0 = 0.57 - 0.60 M⊙ for a wide range of metallicities (Z=0.00001 to Z=0.0005) starting from an initial 7Li abundance A(Li) = 2.72. This environmental Li evolution model offers the possibility to interpret the decreasing of Li abundance in extremely metal-poor stars, the Li disparities in spectroscopic binaries and low Li abundance in planet hosting stars.

  4. Analysis of pre-main-sequence delta-Scuti stars

    NASA Astrophysics Data System (ADS)

    Casey, Michael Patrick

    Information on 72 confirmed or candidate pre-main-sequence delta-Scuti stars is collected and analysed to varying degree of sophistication and completeness. A systematic asteroseismic analysis of around 40 of these stars is performed, putting significant luminosity constraints on many of them simply by comparing the pulsation spectra of the stars to the fundamental and acoustic cut-off frequencies of a dense grid of stellar models. One star in particular, V1366 Ori, appears to be pulsating at or near the acoustic cut-off frequency. Many stars are found to otherwise defy proper asteroseismic analysis, in that matches between observed pulsation spectra and computed values are not able to be found. A simple test reveals that the most likely cause for these problems are the high stellar-rotation rates typically found in this class of star, with v sin i most typically between 60 and 200 km/s. The high rotation rates are found to significantly modify the pulsation spectrum of a star compared to a non-rotating star. These collective results reveal the richness and variety of phenomena within this group of stars, with stars pulsating anywhere from the lowest to the highest possible radial orders, including radial orders just below the acoustic cut-off frequency of some stars. Pulsation in non-radial orders is the normal case, not the exception to the rule, with all stars displaying low-amplitude delta-Scuti variability only.

  5. Habitable zone lifetimes of exoplanets around main sequence stars.

    PubMed

    Rushby, Andrew J; Claire, Mark W; Osborn, Hugh; Watson, Andrew J

    2013-09-01

    The potential habitability of newly discovered exoplanets is initially assessed by determining whether their orbits fall within the circumstellar habitable zone of their star. However, the habitable zone (HZ) is not static in time or space, and its boundaries migrate outward at a rate proportional to the increase in luminosity of a star undergoing stellar evolution, possibly including or excluding planets over the course of the star's main sequence lifetime. We describe the time that a planet spends within the HZ as its "habitable zone lifetime." The HZ lifetime of a planet has strong astrobiological implications and is especially important when considering the evolution of complex life, which is likely to require a longer residence time within the HZ. Here, we present results from a simple model built to investigate the evolution of the "classic" HZ over time, while also providing estimates for the evolution of stellar luminosity over time in order to develop a "hybrid" HZ model. These models return estimates for the HZ lifetimes of Earth and 7 confirmed HZ exoplanets and 27 unconfirmed Kepler candidates. The HZ lifetime for Earth ranges between 6.29 and 7.79×10⁹ years (Gyr). The 7 exoplanets fall in a range between ∼1 and 54.72 Gyr, while the 27 Kepler candidate planets' HZ lifetimes range between 0.43 and 18.8 Gyr. Our results show that exoplanet HD 85512b is no longer within the HZ, assuming it has an Earth analog atmosphere. The HZ lifetime should be considered in future models of planetary habitability as setting an upper limit on the lifetime of any potential exoplanetary biosphere, and also for identifying planets of high astrobiological potential for continued observational or modeling campaigns.

  6. The Winds of Main Sequence B Stars in NGC 6231, Evidence for Shocks in Weak Winds.

    NASA Astrophysics Data System (ADS)

    Massa, Derck

    1996-07-01

    Because the main sequence B stars in NGC 6231 have abnormallystrong C iv wind lines, they are the only main sequence Bstars with distinct edge velocities. Although the underlyingcause for the strong lines remains unknown, these stars doprovide an opportunity to test two important ideas concerningB star winds: 1) that the driving ions in the winds of starswith low mass loss rates decouple from the general flow, and;2) that shocks deep in the winds of main sequence B stars areresponsible for their observed X-rays. In both of thesemodels, the wind accelerates toward a terminal velocity,v_infty, far greater than the observed value, shocking ordecoupling well before it can attain the high v_infty. As aresult, the observable wind accelerates very rapidly, leadingto wind flushing times less than 30 minutes. If theseconjectures are correct, then the winds of main sequence Bstars should be highly variable on time scales of minutes.Model fitting of available IUE data are consistant with thegeneral notion of a rapidly accelerating wind, shocking wellbefore its actual v_infty. However, these are 5 hourexposures, so the fits are to ill-defined mean wind flows.The new GHRS observations will provide adequate spectral andtemporal resolution to observe the expected variability and,thereby, verify the existance of two important astrophysicalprocesses.

  7. Elevation or Suppression? The Resolved Star Formation Main Sequence of Galaxies with Two Different Assembly Modes

    NASA Astrophysics Data System (ADS)

    Liu, Qing; Wang, Enci; Lin, Zesen; Gao, Yulong; Liu, Haiyang; Berhane Teklu, Berzaf; Kong, Xu

    2018-04-01

    We investigate the spatially resolved star formation main sequence in star-forming galaxies using Integral Field Spectroscopic observations from the Mapping Nearby Galaxies at the Apache Point Observatory survey. We demonstrate that the correlation between the stellar mass surface density (Σ*) and star formation rate surface density (ΣSFR) holds down to the sub-galactic scale, leading to the sub-galactic main sequence (SGMS). By dividing galaxies into two populations based on their recent mass assembly modes, we find the resolved main sequence in galaxies with the “outside-in” mode is steeper than that in galaxies with the “inside-out” mode. This is also confirmed on a galaxy-by-galaxy level, where we find the distributions of SGMS slopes for individual galaxies are clearly separated for the two populations. When normalizing and stacking the SGMS of individual galaxies on one panel for the two populations, we find that the inner regions of galaxies with the “inside-out” mode statistically exhibit a suppression in star formation, with a less significant trend in the outer regions of galaxies with the “outside-in” mode. In contrast, the inner regions of galaxies with “outside-in” mode and the outer regions of galaxies with “inside-out” mode follow a slightly sublinear scaling relation with a slope ∼0.9, which is in good agreement with previous findings, suggesting that they are experiencing a universal regulation without influences of additional physical processes.

  8. Lithium in lower-main-sequence stars of the Alpha Persei cluster

    NASA Technical Reports Server (NTRS)

    Balachandran, Suchitra; Lambert, David L.; Stauffer, John R.

    1988-01-01

    Lithium abundances are presented for main-sequence stars of spectral types F, G, and K in the young open cluster Alpha Per. For 46 cluster members, a correlation between Li abundance and projected rotational velocity v sin i is found: all of the Li-poor stars are slow rotators. Two explanations are proposed to account for the correlation: (1) that the Li depletion is introduced following a rapid spin-down phase experienced by young low-mass stars, and that this episode of Li depletion may be the dominant one determining the spread of Li abundances among young low-mass main-sequence stars, and (2) that star formation has occurred over a finite period such that the older stars have undergone a spin-down and depletion of Li by a means that may or may not depend on rotation. The Li abundance in the warm and rapidly rotating stars appears to be undepleted, as is predicted by recent models of pre-main-sequence stars. The depletion observed in the cool stars exceeds the level predicted by these models.

  9. Isolating Added Mass Load Components of CPAS Main Clusters

    NASA Technical Reports Server (NTRS)

    Ray, Eric S.

    2017-01-01

    The current simulation for the Capsule Parachute Assembly System (CPAS) lacks fidelity in representing added mass for the 116 ft Do ringsail Main parachute. The availability of 3-D models of inflating Main canopies allowed for better estimation the enclosed air volume as a function of time. This was combined with trajectory state information to estimate the components making up measured axial loads. A proof-of-concept for an alternate simulation algorithm was developed based on enclosed volume as the primary independent variable rather than drag area growth. Databases of volume growth and parachute drag area vs. volume were developed for several flight tests. Other state information was read directly from test data, rather than numerically propagated. The resulting simulated peak loads were close in timing and magnitude to the measured loads data. However, results are very sensitive to data curve fitting and may not be suitable for Monte Carlo simulations. It was assumed that apparent mass was either negligible or a small fraction of enclosed mass, with little difference in results.

  10. Revisiting Molar Mass, Atomic Mass, and Mass Number: Organizing, Integrating, and Sequencing Fundamental Chemical Concepts

    NASA Astrophysics Data System (ADS)

    Demeo, Stephen

    2006-04-01

    It is often confusing for introductory chemistry students to differentiate between molar mass, atomic mass, and mass number as well as to conceptually understand these ideas beyond a surface level. One way to improve understanding is to integrate the concepts, articulate their relationships, and present them in a meaningful sequence. The integrated conception, what is described as the "atomic mass conception", involves the description and sequencing of these three concepts based upon IUPAC terminology and findings from educational researchers. The sequencing and detail of these concepts run counter to how these three ideas are presented in popular textbooks.

  11. A survey for rapid variability among early main-sequence A stars

    NASA Technical Reports Server (NTRS)

    Schutt, Randy L.

    1993-01-01

    A survey of nonpeculiar early (A0-A5) main-sequence A stars for rapid, low-amplitude variability is presented. The survey is also an independent test of the main-sequence mass-loss theory proposed by Willson et al. (1986). All observations were gathered with the University of Wisconsin Two-Star Photometer. Several period-searching methods are used to analyze time series of differential-photometric data. This instrument coupled with a computerized high-speed data collection system was used with small telescopes at Pine Bluff Observatory and Table Mountain Observatory. Several period-search methods are used to analyze time series of differential-photometric data. This instrument and data-reduction technique allow millimagnitude light variations to be detected. The survey also discovered several low-amplitude Delta Sct stars, all of which are in or blueward of the recognized instability strip.

  12. Lithium evolution in metal-poor stars: from pre-main sequence to the Spite plateau

    NASA Astrophysics Data System (ADS)

    Fu, Xiaoting; Bressan, Alessandro; Molaro, Paolo; Marigo, Paola

    2015-09-01

    Lithium abundance derived in metal-poor main-sequence (MS) stars is about three times lower than the value of primordial Li predicted by the standard big bang nucleosynthesis when the baryon density is taken from the cosmic microwave background or the deuterium measurements. This disagreement is generally referred as the lithium problem. We here reconsider the stellar Li evolution from the pre-main sequence (PMS) to the end of the MS phase by introducing the effects of convective overshooting (OV) and residual mass accretion. We show that 7Li could be significantly depleted by convective OV in the PMS phase and then partially restored in the stellar atmosphere by a tail of matter accretion which follows the Li-depletion phase and that could be regulated by EUV photoevaporation. By considering the conventional nuclear burning and microscopic diffusion along the MS, we can reproduce the Spite plateau for stars with initial mass m0 = 0.62-0.80 M⊙, and the Li declining branch for lower mass dwarfs, e.g. m0 = 0.57-0.60 M⊙, for a wide range of metallicities (Z = 0.00001 to Z = 0.0005), starting from an initial Li abundance A(Li) = 2.72. This environmental Li evolution model also offers the possibility to interpret the decrease of Li abundance in extremely metal-poor stars, the Li disparities in spectroscopic binaries and the low Li abundance in planet hosting stars.

  13. ABSOLUTE PROPERTIES OF THE PRE-MAIN-SEQUENCE ECLIPSING BINARY STAR NP PERSEI

    SciTech Connect

    Lacy, Claud H. Sandberg; Fekel, Francis C.; Muterspaugh, Matthew W.

    2016-07-01

    NP Per is a well-detached, 2.2 day eclipsing binary whose components are both pre-main-sequence stars that are still contracting toward the main-sequence phase of evolution. We report extensive photometric and spectroscopic observations with which we have determined their properties accurately. Their surface temperatures are quite different: 6420 ± 90 K for the larger F5 primary star and 4540 ± 160 K for the smaller K5e star. Their masses and radii are 1.3207 ± 0.0087 solar masses and 1.372 ± 0.013 solar radii for the primary, and 1.0456 ± 0.0046 solar masses and 1.229 ± 0.013 solar radii for the secondary. The orbital period is variable over long periods of time. A comparisonmore » of the observations with current stellar evolution models from MESA indicates that the stars cannot be fit at a single age: the secondary appears significantly younger than the primary. If the stars are assumed to be coeval and to have the age of the primary (17 Myr), then the secondary is larger and cooler than predicted by current models. The H α spectral line of the secondary component is completely filled by, presumably, chromospheric emission due to a magnetic activity cycle.« less

  14. Theory of winds in late-type evolved and pre-main-sequence stars

    NASA Technical Reports Server (NTRS)

    Macgregor, K. B.

    1983-01-01

    Recent observational results confirm that many of the physical processes which are known to occur in the Sun also occur among late-type stars in general. One such process is the continuous loss of mass from a star in the form of a wind. There now exists an abundance of either direct or circumstantial evidence which suggests that most (if not all) stars in the cool portion of the HR diagram possess winds. An attempt is made to assess the current state of theoretical understanding of mass loss from two distinctly different classes of late-type stars: the post-main-sequence giant/supergiant stars and the pre-main-sequence T Tauri stars. Toward this end, the observationally inferred properties of the wind associated with each of the two stellar classes under consideration are summarized and compared against the predictions of existing theoretical models. Although considerable progress has been made in attempting to identify the mechanisms responsible for mass loss from cool stars, many fundamental problems remain to be solved.

  15. Discovery and characterization of 3000+ main-sequence binaries from APOGEE spectra

    NASA Astrophysics Data System (ADS)

    El-Badry, Kareem; Ting, Yuan-Sen; Rix, Hans-Walter; Quataert, Eliot; Weisz, Daniel R.; Cargile, Phillip; Conroy, Charlie; Hogg, David W.; Bergemann, Maria; Liu, Chao

    2018-05-01

    We develop a data-driven spectral model for identifying and characterizing spatially unresolved multiple-star systems and apply it to APOGEE DR13 spectra of main-sequence stars. Binaries and triples are identified as targets whose spectra can be significantly better fit by a superposition of two or three model spectra, drawn from the same isochrone, than any single-star model. From an initial sample of ˜20 000 main-sequence targets, we identify ˜2500 binaries in which both the primary and secondary stars contribute detectably to the spectrum, simultaneously fitting for the velocities and stellar parameters of both components. We additionally identify and fit ˜200 triple systems, as well as ˜700 velocity-variable systems in which the secondary does not contribute detectably to the spectrum. Our model simplifies the process of simultaneously fitting single- or multi-epoch spectra with composite models and does not depend on a velocity offset between the two components of a binary, making it sensitive to traditionally undetectable systems with periods of hundreds or thousands of years. In agreement with conventional expectations, almost all the spectrally identified binaries with measured parallaxes fall above the main sequence in the colour-magnitude diagram. We find excellent agreement between spectrally and dynamically inferred mass ratios for the ˜600 binaries in which a dynamical mass ratio can be measured from multi-epoch radial velocities. We obtain full orbital solutions for 64 systems, including 14 close binaries within hierarchical triples. We make available catalogues of stellar parameters, abundances, mass ratios, and orbital parameters.

  16. The evolved slowly pulsating B star 18 Peg. A testbed for upper main sequence stellar evolution

    NASA Astrophysics Data System (ADS)

    Irrgang, Andreas; De Cat, Peter; Tkachenko, Andrew

    2017-09-01

    The predicted width of the upper main sequence in stellar evolution models depends on the empirical calibration of the convective overshooting parameter. Despite decades of discussions, its precise value is still unknown and further observational constraints are required to gauge it. Irrgang et al. ([1]) showed that the B3 III giant 18 Peg is one of the most evolved members of the class of slowly pulsating B (SPB) stars and, thus, bears tremendous potential to derive a tight lower limit for the width of the upper main sequence. In addition, 18 Peg turns out to be part of a single-lined spectroscopic binary system with an eccentric, more than 6-year orbit. The orbital solution, in combination with the absence of additional signatures of the secondary component in the spectroscopic data and the spectral energy distribution, lead to the conclusion that all the observations of 18 Peg are fully compatible with the assumption that the secondary component is either a main-sequence star with a mass of 1-4 M⊙ or a neutron star.

  17. Tracing Star Formation and Molecular Cloud Evolution with Pre-main Sequence Stars in the SMC

    NASA Astrophysics Data System (ADS)

    Johnson, L. Clifton; SMIDGE Team

    2018-01-01

    The Southwest Bar region in the Small Magellanic Cloud (SMC) contains star-forming molecular clouds sampling a wide range of evolutionary states: from quiescent pre-star-forming regions to evolved HII region hosts. We use deep, panchromatic, high spatial resolution Hubble Space Telescope imaging obtained as part of the SMIDGE survey (PI: K. Sandstrom) to identify young, pre-main sequence stars that trace recent and ongoing star formation within these clouds. We characterize a color-selected sample (and Hα line-emitting subsample) of pre-main sequence stars via SED fitting and analyze their association with the local ISM, inferred from observations of CO and dust emission. These low-mass stars serve as robust star formation tracers not tied to massive stars (e.g., Hα-based star formation rate estimates) in SMC star-forming regions, where low dust-to-gas ratios allow optical detections even in gas-rich embedded regions. We demonstrate pre-main sequence stars' ability to trace molecular cloud evolution within the Southwest Bar and across the SMC, and discuss future synergies between optical Hubble Space Telescope observations and near/mid-IR James Webb Space Telescope observations.

  18. Discovery of three X-ray luminous pre-main-sequence stars

    NASA Technical Reports Server (NTRS)

    Feigelson, E. D.; Kriss, G. A.

    1981-01-01

    Three X-ray sources found serendipitously in Einstein images of the Taurus-Auriga cloud complex were observed at the McGraw-Hill Observatory and are found to be associated with stars of approximately 12 mag with weak H-alpha emission. The stars lie on the edges of dark clouds and are spectroscopically similar to the least active emission-line pre-main-sequence stars. Although they lie well above the ZAMS in the H-R diagram, they do not exhibit ultraviolet excess, strong optical variability, or evidence for mass outflow/inflow characteristics of the more active T Tauri stars. Their only unusual property is high X-ray luminosity (approximately 10 to the 30th ergs/s). It is suggested that the X-ray emission from pre-main-sequence stars is not closely linked to the conditions giving rise to their unusual spectroscopic properties. The emission may instead represent an enhanced form of the coronal activity producing X-rays observed in late-type main-sequence stars.

  19. Updating the Dartmouth Stellar Evolution Model Grid: Pre-main-sequence Models & Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Feiden, Gregory A.; Jones, Jaquille; Chaboyer, Brian

    2015-01-01

    We present the current status of an effort to create an updated grid of low-mass stellar evolution mass tracks and isochrones computed using the Dartmouth stellar evolution code. Emphasis is placed on reliably extending the present grid to the pre-main-sequence, where modeling uncertainties have the greatest impact. Revisions to the original code release include: updated surface boundary conditions, the introduction of deuterium burning, and magnetic fields. The mass track grid contains models with a mass above 0.1 M_{⊙} and metallicities in the range of -0.5 to +0.5 dex. Magnetic mass tracks are calculated for surface magnetic field strengths between 0.1 kG and 4.0 kG using two different prescriptions for magneto-convection. Standard and magnetic model isochrones are available for ages older than 1 Myr. Tabulated quantities include the stellar fundamental properties, absolute photometric magnitudes, magnetic field properties, convective turnover times, apsidal motion constants, and lithium abundances. The complete grid of mass tracks and isochrones will be made publicly available.

  20. ORBITS, MASSES, AND EVOLUTION OF MAIN BELT TRIPLE (87) SYLVIA

    SciTech Connect

    Fang, Julia; Margot, Jean-Luc; Rojo, Patricio

    2012-08-15

    Sylvia is a triple asteroid system located in the main belt. We report new adaptive optics observations of this system that extend the baseline of existing astrometric observations to a decade. We present the first fully dynamical three-body model for this system by fitting to all available astrometric measurements. This model simultaneously fits for individual masses, orbits, and primary oblateness. We find that Sylvia is composed of a dominant central mass surrounded by two satellites orbiting at 706.5 {+-} 2.5 km and 1357 {+-} 4.0 km, i.e., about 5 and nearly 10 primary radii. We derive individual masses of 1.484{supmore » +0.016}{sub -0.014} Multiplication-Sign 10{sup 19} kg for the primary (corresponding to a density of 1.29 {+-} 0.39 g cm{sup -3}), 7.33{sup +4.7}{sub -2.3} Multiplication-Sign 10{sup 14} kg for the inner satellite, and 9.32{sup +20.7}{sub -8.3} Multiplication-Sign 10{sup 14} kg for the outer satellite. The oblateness of the primary induces substantial precession and the J{sub 2} value can be constrained to the range of 0.0985-0.1. The orbits of the satellites are relatively circular with eccentricities less than 0.04. The spin axis of the primary body and the orbital poles of both satellites are all aligned within about 2 deg of each other, indicating a nearly coplanar configuration and suggestive of satellite formation in or near the equatorial plane of the primary. We also investigate the past orbital evolution of the system by simulating the effects of a recent passage through 3:1 mean-motion eccentricity-type resonances. In some scenarios this allow us to place constraints on interior structure and past eccentricities.« less

  1. The Main Sequence of Explosive Solar Active Regions: Comparison of Emerging and Mature Active Regions

    NASA Technical Reports Server (NTRS)

    Falconer, David; Moore, Ron

    2011-01-01

    For mature active regions, an active region s magnetic flux content determines the maximum free energy the active region can have. Most Large flares and CMEs occur in active regions that are near their free-energy limit. Active-region flare power radiated in the GOES 1-8 band increases steeply as the free-energy limit is approached. We infer that the free-energy limit is set by the rate of release of an active region s free magnetic energy by flares, CMEs and coronal heating balancing the maximum rate the Sun can put free energy into the active region s magnetic field. This balance of maximum power results in explosive active regions residing in a "mainsequence" in active-region (flux content, free energy content) phase space, which sequence is analogous to the main sequence of hydrogen-burning stars in (mass, luminosity) phase space.

  2. Water Masses and Nutrient Sources to the Gulf of Maine

    PubMed Central

    Townsend, David W.; Pettigrew, Neal R.; Thomas, Maura A.; Neary, Mark G.; McGillicuddy, Dennis J.; O’Donnell, James

    2016-01-01

    The Gulf of Maine, a semi-enclosed basin on the continental shelf of the northwest Atlantic Ocean, is fed by surface and deep water flows from outside the Gulf: Scotian Shelf Water from the Nova Scotian shelf that enters the Gulf at the surface, and Slope Water that enters at depth and along the bottom through the Northeast Channel. There are two types of Slope Water, Labrador Slope Water (LSW) and Warm Slope Water (WSW); it is these deep water masses that are the major source of dissolved inorganic nutrients to the Gulf. It has been known for some time that the volume inflow of Slope Waters of either type that enters the Gulf of Maine is variable, that it co-varies with the magnitude of inflowing Scotian Shelf Water, and that periods of greater inflows of Scotian Shelf Water have become more frequent in recent years, accompanied by reduced Slope Water inflows. We present here analyses of a ten-year record of data collected by moored sensors in Jordan Basin, in the interior Gulf of Maine, and in the Northeast Channel, along with recent and historical hydrographic and nutrient data, that help reveal the nature of Scotian Shelf Water and Slope Water inflows. Proportional inflows of nutrient-rich Slope Waters and nutrient-poor Scotian Shelf Waters alternate episodically with one another on time scales of months to several years, creating a variable nutrient field upon which the biological productivities of the Gulf of Maine and Georges Bank depend. Unlike decades past, the inflows of Slope Waters of either type do not appear to be correlated with the North Atlantic Oscillation, which had been shown earlier to influence the relative proportions of the two Slope Waters, WSW and LSW, that enter the Gulf. We suggest that of greater importance in recent years are more frequent, episodic influxes of colder, fresher, less dense, and low-nutrient Scotian Shelf Water into the Gulf of Maine, and concomitant reductions in the inflow of deep, nutrient-rich Slope Waters. We also

  3. NEW X-RAY-SELECTED PRE-MAIN-SEQUENCE MEMBERS OF THE SERPENS MOLECULAR CLOUD

    SciTech Connect

    Oliveira, Isa; Van der Laan, Margriet; Brown, Joanna M., E-mail: oliveira@astro.as.utexas.edu

    2013-11-01

    The study of young stars no longer surrounded by disks can greatly add to our understanding of how protoplanetary disks evolve and planets form. We have used VLT/FLAMES optical spectroscopy to confirm the youth and membership of 19 new young diskless stars in the Serpens Molecular Cloud, identified at X-ray wavelengths. Spectral types, effective temperatures, and stellar luminosities were determined using optical spectra and optical/near-infrared photometry. Stellar masses and ages were derived based on pre-main-sequence evolutionary tracks. The results yield remarkable similarities for age and mass distribution between the diskless and disk-bearing stellar populations in Serpens. We discuss the importantmore » implications these similarities may have on the standard picture of disk evolution.« less

  4. Acne at The Bottom Of The Main Sequence

    NASA Astrophysics Data System (ADS)

    Barnes, John; Haswell, C.; Jenkins, J.; Jeffers, S.; Jones, H. R. A.; Lohr, M.; Pavlenko, Y.

    2016-08-01

    Starspots are an important manifestation of stellar activity and yet their distribution patterns on the lowest mass stars is not well known. Time series spectra of fully convective M dwarfs taken in the red-optical with UVES reveal numerous line profile distortions which are interpreted as starspots. We derive Doppler images for four M4.5V - M9V stars and find that contrast ratios corresponding to photosphere-spot temperature differences of only 200-300 K are sufficient to model the timeseries spectra. Although more starspot structure is found at high latitudes, spots are reconstructed at a range of phases and latitudes with mean spot filling factors of only a few per cent. The occurrence of low-contrast spots at predominantly high latitudes is in general likely to be responsible for the low amplitude photometric variability seen in late-M dwarfs. The recovered starspot patterns are used to assess their effect on precision radial velocity surveys aimed at detecting planets around this population of stars.

  5. ACCRETION RATES ON PRE-MAIN-SEQUENCE STARS IN THE YOUNG OPEN CLUSTER NGC 6530

    SciTech Connect

    Gallardo, Jose; Del Valle, Luciano; Ruiz, Maria Teresa, E-mail: gallardo@das.uchile.cl, E-mail: ldelvall@das.uchile.cl, E-mail: mtruiz@das.uchile.cl

    2012-01-15

    It is well accepted that during the star formation process, material from a protoplanetary disk is accreted onto the central object during the first {approx}1-5 Myr. Different authors have published measurements of accretion rates for young low- and intermediate-mass stars in several nearby star-forming regions (SFRs). Due to its somewhat larger distance, the SFR M8 (the Lagoon Nebula) has not been studied to the same extent, despite its abundant population of young stellar objects. We have obtained optical band low-resolution spectra of a sample of pre-main-sequence stars in the open cluster NGC 6530 located in the aforementioned nebulae using themore » Gemini Multi Object Spectrograph at Gemini-South in multi-object mode. Spectra cover the H{sub {alpha}} emission line used to measure the accretion rate, following the method presented by Natta et al. The observed spectral characteristics are fully consistent with pre-main-sequence stars, showing lithium absorption lines, which are very common in young stellar objects, as well as prominent and broad H{sub {alpha}} emission lines, indicating a T Tauri evolutionary stage. This work presents the first determinations of mass accretion rates of young stellar objects in the open cluster NGC 6530, confirming that they are classical T Tauri stars going through the accretion phase. These observations contribute to a better understanding of the stellar content and evolutionary phase of the very active Lagoon Nebula SFR.« less

  6. Winds in hot main-sequence stars near the static limit

    NASA Technical Reports Server (NTRS)

    Morrison, Nancy D.

    1995-01-01

    This project began with the acquisition of short-wavelength, high-dispersion IUE spectra of selected late O- and early B-type stars that are near the main sequence in open clusters and associations. The profiles of the resonance lines of N(V), Si(IV), and C(IV) were studied, and we found that the C(IV) lines are the most sensitive indicators of mass loss (stellar winds) in stars of this type. The mass loss manifests itself as an extension of the short-wavelength absorption wing of the doublet, while there is no P Cygni-type emission on the long-wavelength side of the line profile. We investigated whether the short-wavelength extension could be caused by blended lines of other ionic species formed in the photosphere. Although blending is present and introduces uncertainty into the estimation of the precise location on the main sequence of the onset of the mass-loss signature, it is a crucial issue only in a few marginal cases. Mass loss certainly overwhelms blending in its influence on the spectrum between spectral types B0 and B1 (effective temperatures in the range 25,000-27,000 K). We defined a parameter called P(sub w), to describe the degree of asymmetry of the C(IV) resonance-line profile, and we studied the dependence of this parameter on the fundamental stellar parameters. For this purpose, we derived new estimates of the stellar T(eff) and log g from a non-LTE, line-blanketed model-atmosphere analysis of these stars (Grigsby, Morrison, and Anderson 1992). In order to estimate the stellar luminosities, we performed an exhaustive search of the literature for the most reliable available estimates of the distances of the clusters and associations to which the program stars belong. The dependence of P(sub w) on stellar temperature and luminosity is also studied.

  7. Constraining the magnitude of the largest event in a foreshock-main shock-aftershock sequence

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Robert; Zhuang, Jiancang; Ogata, Yosihiko

    2018-01-01

    Extreme value statistics and Bayesian methods are used to constrain the magnitudes of the largest expected earthquakes in a sequence governed by the parametric time-dependent occurrence rate and frequency-magnitude statistics. The Bayesian predictive distribution for the magnitude of the largest event in a sequence is derived. Two types of sequences are considered, that is, the classical aftershock sequences generated by large main shocks and the aftershocks generated by large foreshocks preceding a main shock. For the former sequences, the early aftershocks during a training time interval are used to constrain the magnitude of the future extreme event during the forecasting time interval. For the latter sequences, the earthquakes preceding the main shock are used to constrain the magnitudes of the subsequent extreme events including the main shock. The analysis is applied retrospectively to past prominent earthquake sequences.

  8. Main-Sequence CMEs as Magnetic Explosions: Compatibility with Observed Kinematics

    NASA Technical Reports Server (NTRS)

    Moore, Ron; Falconer, David; Sterling, Alphonse

    2004-01-01

    We examine the kinematics of 26 CMEs of the morphological main sequence of CMEs, those having the classic three-part bubble structure of (1) a bright front eveloping (2) a dark cavity within which rides (3) a bright blob/filamentary feature. Each CME is observed in Yohkoh/SXT images to originate from near the limb (> or equal to 0.7 R(sub Sun) from disk center). The basic data (from the SOHO LASCO CME Catalog) for the kinematics of each CME are the sequence of LASCO images of the CME, the time of each image, the measured radial distance of the front edge of the CME in each image, and the measured angular extent of the CME. About half of our CMEs (12) occur with a flare, and the rest (14) occur without a flare. While the average linear-fit speed of the flare CMEs (1000 km/s) is twice that of the non-flare CMEs (510 km/s), the flare CMEs and the non-flare CMEs are similar in that some have nearly flat velocity-height (radial extent) profiles (little acceleration), some have noticeably falling velocity profiles (noticeable deceleration), and the rest have velocity profiles that rise considerably through the outer corona (blatant acceleration). This suggests that in addition to sharing similar morphology, main-sequence CMEs all have basically the same driving mechanism. The observed radial progression of each of our 26 CMEs is fit by a simple model magnetic plasmoid that is in pressure balance with the radial magnetic field in the outer corona and that propels itself outward by magnetic expansion, doing no net work on its surroundings. On average over the 26 CMEs, this model fits the observations as well as the assumption of constant acceleration. This is compatible with main-sequence CMEs being magnetically driven, basically magnetic explosions, with the velocity profile in the outer corona being largely dictated by the initial Alfien speed in the CME (when the front is at approx. 3 (sub Sun), analogous to the mass of a main-sequence star dictating the luminosity.

  9. Evolution of magnetic fields in stars across the upper main sequence: II. Observed distribution of the magnetic field geometry

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; North, P.; Schöller, M.

    2007-07-01

    We re-discuss the evolutionary state of upper main sequence magnetic stars using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and definitely determined longitudinal magnetic fields. We confirm our previous results obtained from the study of Ap and Bp stars with accurate measurements of the mean magnetic field modulus and mean quadratic magnetic fields that magnetic stars of mass {M}<3 M_⊙ are concentrated towards the centre of the main-sequence band. In contrast, stars with masses {M}>3 M_⊙ seem to be concentrated closer to the ZAMS. The study of a few known members of nearby open clusters with accurate Hipparcos parallaxes confirms these conclusions. Stronger magnetic fields tend to be found in hotter, younger and more massive stars, as well as in stars with shorter rotation periods. The longest rotation periods are found only in stars which spent already more than 40% of their main sequence life, in the mass domain between 1.8 and 3 M_⊙ and with log g values ranging from 3.80 to 4.13. No evidence is found for any loss of angular momentum during the main-sequence life. The magnetic flux remains constant over the stellar life time on the main sequence. An excess of stars with large obliquities β is detected in both higher and lower mass stars. It is quite possible that the angle β becomes close to 0o in slower rotating stars of mass {M}>3 M_⊙ too, analog to the behaviour of angles β in slowly rotating stars of {M}<3 M_⊙. The obliquity angle distribution as inferred from the distribution of r-values appears random at the time magnetic stars become observable on the H-R diagram. After quite a short time spent on the main sequence, the obliquity angle β tends to reach values close to either 90o or 0o for {M}<3 M_⊙. The evolution of the obliquity angle β seems to be somewhat different for low and high mass stars. While we find a strong hint for an increase of β with the elapsed time on the main sequence for stars with {M}>3 M_⊙, no

  10. ESTIMATING THE RADIUS OF THE CONVECTIVE CORE OF MAIN-SEQUENCE STARS FROM OBSERVED OSCILLATION FREQUENCIES

    SciTech Connect

    Yang, Wuming, E-mail: yangwuming@bnu.edu.cn, E-mail: yangwuming@ynao.ac.cn

    2016-10-01

    The determination of the size of the convective core of main-sequence stars is usually dependent on the construction of models of stars. Here we introduce a method to estimate the radius of the convective core of main-sequence stars with masses between about 1.1 and 1.5 M {sub ⊙} from observed frequencies of low-degree p -modes. A formula is proposed to achieve the estimation. The values of the radius of the convective core of four known stars are successfully estimated by the formula. The radius of the convective core of KIC 9812850 estimated by the formula is 0.140 ± 0.028 Rmore » {sub ⊙}. In order to confirm this prediction, a grid of evolutionary models was computed. The value of the convective-core radius of the best-fit model of KIC 9812850 is 0.149 R {sub ⊙}, which is in good agreement with that estimated by the formula from observed frequencies. The formula aids in understanding the interior structure of stars directly from observed frequencies. The understanding is not dependent on the construction of models.« less

  11. Galaxy Zoo: spiral galaxy morphologies and their relation to the star-forming main sequence

    NASA Astrophysics Data System (ADS)

    Willett, Kyle; Schawinski, Kevin; Masters, Karen; Melvin, Tom; Skibba, Ramin A.; Nichol, Robert; Cheung, Edmond; Lintott, Chris; Simmons, Brooke D.; Kaviraj, Sugata; Keel, William C.; Fortson, Lucy; Galaxy Zoo volunteers

    2015-01-01

    We examine the relationship between stellar mass and star formation rate in disk galaxies at z<0.085, measuring different populations of spirals as classified by their kiloparsec-scale structure. The morphologies of disk galaxies are obtained from the Galaxy Zoo 2 project, which includes the number of spiral arms, the arm pitch angle, and the presence of strong galactic bars. We show that both the slope and dispersion of the star-forming main sequence (SFMS) is constant no matter what the morphology of the spiral disk. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by 0.3 dex; this is a significant reduction over the increase seen in merging systems at higher redshifts (z > 1). Of the galaxies that do lie significantly above the SFMS in the local Universe, more than 50% are mergers, with a large contribution from the compact green pea galaxies. We interpret our results as evidence that the number and pitch angle of spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms for star formation or are completely overwhelmed by the combination of outflows and feedback.

  12. An extensive VLT/X-shooter library of photospheric templates of pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Manara, C. F.; Frasca, A.; Alcalá, J. M.; Natta, A.; Stelzer, B.; Testi, L.

    2017-09-01

    Context. Studies of the formation and evolution of young stars and their disks rely on knowledge of the stellar parameters of the young stars. The derivation of these parameters is commonly based on comparison with photospheric template spectra. Furthermore, chromospheric emission in young active stars impacts the measurement of mass accretion rates, a key quantity for studying disk evolution. Aims: Here we derive stellar properties of low-mass (M⋆≲ 2 M⊙) pre-main sequence stars without disks, which represent ideal photospheric templates for studies of young stars. We also use these spectra to constrain the impact of chromospheric emission on the measurements of mass accretion rates. The spectra are reduced, flux-calibrated, and corrected for telluric absorption, and are made available to the community. Methods: We derive the spectral type for our targets by analyzing the photospheric molecular features present in their VLT/X-shooter spectra by means of spectral indices and comparison of the relative strength of photospheric absorption features. We also measure effective temperature, gravity, projected rotational velocity, and radial velocity from our spectra by fitting them with synthetic spectra with the ROTFIT tool. The targets have negligible extinction (AV< 0.5 mag) and spectral type from G5 to K6, and from M6.5 to M8. They thus complement the library of photospheric templates presented in our previous publication. We perform synthetic photometry on the spectra to derive the typical colors of young stars in different filters. We measure the luminosity of the emission lines present in the spectra and estimate the noise due to chromospheric emission in the measurements of accretion luminosity in accreting stars. Results: We provide a calibration of the photospheric colors of young pre-main sequence stars as a function of their spectral type in a set of standard broad-band optical and near-infrared filters. The logarithm of the noise on the accretion

  13. Post main sequence evolution of icy minor planets: water retention and white dwarf pollution

    NASA Astrophysics Data System (ADS)

    Malamud, Uri; Perets, Hagai

    2017-06-01

    We investigate the evolution of icy minor planets from the moment of their birth and through the all evolutionary stages of their host stars, including the main sequence, red giant branch and asymptotic giant branch phases. We then asses the degree of water retention in planetary systems around white dwarf, as a function of various parameters. We consider progenitor stars of different masses and metallicities. We also consider minor planets of various sizes, initial orbital distances, compositions and formation times. Our results indicate that water can survive to the white dwarf stage in a variety of circumstances, especially around G, F, A and even some B type stars. We discuss the significance of water retention with respect to white dwarf pollution and also for planet habitability.

  14. 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.

  15. A Population Study of Wide-Separation Brown Dwarf Companions to Main Sequence Stars

    NASA Technical Reports Server (NTRS)

    Smith, Jeffrey J.

    2005-01-01

    Increased interest in infrared astronomy has opened the frontier to study cooler objects that shed significant light on the formation of planetary systems. Brown dwarf research provides a wealth of information useful for sorting through a myriad of proposed formation theories. Our study combines observational data from 2MASS with rigorous computer simulations to estimate the true population of long-range (greater than 1000 AU) brown dwarf companions in the solar neighborhood (less than 25 pc from Earth). Expanding on Gizis et al. (2001), we have found the margin of error in previous estimates to be significantly underestimated after we included orbit eccentricity, longitude of pericenter, angle of inclination, field star density, and primary and secondary luminosities as parameters influencing the companion systems in observational studies. We apply our simulation results to current L- and T-dwarf catalogs to provide updated estimates on the frequency of wide-separation brown dwarf companions to main sequence stars.

  16. Fundamental Parameters of Main-Sequence Stars in an Instant with Machine Learning

    NASA Astrophysics Data System (ADS)

    Bellinger, Earl P.; Angelou, George C.; Hekker, Saskia; Basu, Sarbani; Ball, Warrick H.; Guggenberger, Elisabeth

    2016-10-01

    Owing to the remarkable photometric precision of space observatories like Kepler, stellar and planetary systems beyond our own are now being characterized en masse for the first time. These characterizations are pivotal for endeavors such as searching for Earth-like planets and solar twins, understanding the mechanisms that govern stellar evolution, and tracing the dynamics of our Galaxy. The volume of data that is becoming available, however, brings with it the need to process this information accurately and rapidly. While existing methods can constrain fundamental stellar parameters such as ages, masses, and radii from these observations, they require substantial computational effort to do so. We develop a method based on machine learning for rapidly estimating fundamental parameters of main-sequence solar-like stars from classical and asteroseismic observations. We first demonstrate this method on a hare-and-hound exercise and then apply it to the Sun, 16 Cyg A and B, and 34 planet-hosting candidates that have been observed by the Kepler spacecraft. We find that our estimates and their associated uncertainties are comparable to the results of other methods, but with the additional benefit of being able to explore many more stellar parameters while using much less computation time. We furthermore use this method to present evidence for an empirical diffusion-mass relation. Our method is open source and freely available for the community to use.6

  17. Accretion Rates on Pre-main-sequence Stars in the Young Open Cluster NGC 6530

    NASA Astrophysics Data System (ADS)

    Gallardo, José; del Valle, Luciano; Ruiz, María Teresa

    2012-01-01

    It is well accepted that during the star formation process, material from a protoplanetary disk is accreted onto the central object during the first ~1-5 Myr. Different authors have published measurements of accretion rates for young low- and intermediate-mass stars in several nearby star-forming regions (SFRs). Due to its somewhat larger distance, the SFR M8 (the Lagoon Nebula) has not been studied to the same extent, despite its abundant population of young stellar objects. We have obtained optical band low-resolution spectra of a sample of pre-main-sequence stars in the open cluster NGC 6530 located in the aforementioned nebulae using the Gemini Multi Object Spectrograph at Gemini-South in multi-object mode. Spectra cover the Hα emission line used to measure the accretion rate, following the method presented by Natta et al. The observed spectral characteristics are fully consistent with pre-main-sequence stars, showing lithium absorption lines, which are very common in young stellar objects, as well as prominent and broad Hα emission lines, indicating a T Tauri evolutionary stage. This work presents the first determinations of mass accretion rates of young stellar objects in the open cluster NGC 6530, confirming that they are classical T Tauri stars going through the accretion phase. These observations contribute to a better understanding of the stellar content and evolutionary phase of the very active Lagoon Nebula SFR. 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 Ciencia e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva

  18. PSR J1903+0327: A UNIQUE MILLISECOND PULSAR WITH A MAIN-SEQUENCE COMPANION STAR

    SciTech Connect

    Khargharia, Juthika; Stocke, John T.; Froning, Cynthia S.

    2012-01-10

    PSR J1903+0327 is a millisecond pulsar with a mass of 1.67 M{sub Sun} in a highly eccentric orbit (e = 0.44) around a main-sequence star. This unique system cannot be reconciled with current observations where millisecond pulsars are generally seen to orbit white dwarfs in almost exactly circular orbits. Current theoretical models of binary and stellar formation and evolution cannot explain the high eccentricity of this system either. In this work, we present three new epochs of optical spectroscopy for the companion to PSR J1903+0327, obtained to confirm the association of the main-sequence star with the pulsar. These three newmore » epochs, together with the two previous ones, firmly establish the high eccentricity of the companion's orbit as predicted by pulsar timing. Using all five epochs of optical data, we have provided an independent estimate of the mass ratio, R = 1.56 {+-} 0.15, as well as the systemic radial velocity of the binary, {gamma} = 42.1 {+-} 2.5 km s{sup -1}. We constrain the spectral type of the pulsar companion to lie between F5 V and G0 V (a slightly earlier type than suggested previously) by measuring the equivalent widths of two of the three Ca-triplet lines (8498 A, 8542 A) and the Paschen line at 8598 A (P14); we also broadly constrain the metallicity of the companion. Additionally, we have placed a somewhat better limit on the rotational velocity of the pulsar companion of v{sub rot}sin i {<=} 66 km s{sup -1}, which is still not sufficient to allow a test of general relativity using this system.« less

  19. The potential of space observations for pulsating pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Zwintz, Konstanze

    2017-10-01

    The first asteroseismic studies of pre-main sequence (pre-MS) pulsators have been conducted based on data from the space telescopes MOST and CoRoT with typical time bases of less than 40 days. With these data, a relation between the pulsational properties of pre-MS δ Scuti stars and their relative evolutionary phase on their way from the birthline to the zero-age main sequence was revealed. But it is evident from comparison with the more evolved pulsators in their main sequence or post-main sequence stages observed by the main Kepler mission, that many more questions could be addressed with significantly longer time bases and ultrahigh precision. Here, I will discuss the observational status of pre-MS asteroseismology and the potential of future space observations for this research field.

  20. How supercritical are stellar dynamos, or why do old main-sequence dwarfs not obey gyrochronology?

    NASA Astrophysics Data System (ADS)

    Kitchatinov, Leonid; Nepomnyashchikh, Alexander

    2017-09-01

    Asteroseismological determinations of stellar ages have shown that old main-sequence dwarfs do not obey gyrochronology. Their rotation is slow compared to young stars but faster than what gyrochronology predicts. This can be explained by the presence of a maximum rotation period beyond which the large-scale dynamo switches off and stops providing global magnetic fields necessary for stellar spin-down. Assuming this explanation, the excess of stellar dynamo parameters over their marginal values can be estimated for the given spectral type and rotation rate. The estimation gives the dynamo number for the Sun about 10 per cent above its critical value. The corresponding dynamo model provides - though with some further tuning - reasonable results for the Sun. Following the same approach, the differential rotation and marginal dynamo modes are computed for stars between 0.7 and 1.2 solar masses. With an increasing stellar mass, the differential rotation and the ratio of toroidal-to-poloidal field are predicted to increase while the field topology changes from dipolar to mixed quadrupolar-dipolar parity.

  1. ASTEROSEISMIC ANALYSIS OF THE PRE-MAIN-SEQUENCE STARS IN NGC 2264

    SciTech Connect

    Guenther, D. B.; Casey, M. P.; Kallinger, T.

    2009-10-20

    NGC 2264 is a young open cluster lying above the Galactic plane in which six variable stars have previously been identified as possible pre-main-sequence (PMS) pulsators. Their oscillation spectra are relatively sparse with each star having from 2 to 12 unambiguous frequency identifications based on Microvariability and Oscillations of Stars satellite and multi-site ground-based photometry. We describe our efforts to find classical PMS stellar models (i.e., models evolved from the Hayashi track) whose oscillation spectra match the observed frequencies. We find model eigenspectra that match the observed frequencies and are consistent with the stars' locations in the HR diagram formore » the three faintest of the six stars. Not all the frequencies found in spectra of the three brightest stars can be matched to classical PMS model spectra possibly because of effects not included in our PMS models such as chemical and angular momentum stratification in the outer layers of the star. All the oscillation spectra contain both radial and nonradial p-modes. We argue that the PMS pulsating stars divide into two groups depending on whether or not they have undergone complete mixing (i.e., have gone through a Hayashi phase). Lower mass stars that do evolve through a Hayashi phase have oscillation spectra predicted by classical PMS models, whereas more massive stars that do not, retain mass infall effects in their surface layers and are not well modeled by classical PMS models.« less

  2. The origin of the scatter of the star forming main sequence at z=0

    NASA Astrophysics Data System (ADS)

    Shanahan, Clare; Somerville, Rachel S.; Saintonge, Amelie; Huang, Mei-Ling

    2016-01-01

    We investigate the origin of the dispersion in the relationship between star formation rate (SFR) and stellar mass, known as the star forming main sequence (SFMS). Our study includes predictions from a state-of-the-art semi-analytic model (SAM) as well as observations from the COLDGASS, Bluedisk, and GAMA surveys. Using a simple toy model we demonstrate that, in the absence of a correlation between gas fraction and galaxy size, we would expect more compact disks to live 'high' on the SFMS, and vice versa, due to the observational Kennicutt relation. We demonstrate that this correlation is not seen in the observations, nor is it predicted by the SAM. We find in both the model and the observations that extended disks have a higher fraction of their baryonic mass in total cold gas and in HI and $H_{2}$ gas separately, offsetting the dependence of SFR on disk size. We investigate the origin of the gas fraction-size correlation in the SAMs, and find that it is connected with the rate of cosmological accretion of gas from the intergalactic medium.

  3. On The Sfr-M* Main Sequence Archetypal Star-Formation History And Analytical Models

    NASA Astrophysics Data System (ADS)

    Ciesla, Laure; Elbaz, David; Fensch, Jeremy

    2017-06-01

    From the evolution of the main sequence we can build the star formation history (SFH) of MS galaxies, assuming that they follow this relation all their life. We show that this SFH is not only a function of cosmic time but also involve the seed mass of the galaxy. We discuss the implications of this MS SFH on the stellar mass growth, and the entry in the passive region of the UVJ diagram, while the galaxy is still forming stars. We test the ability of different analytical SFH forms found in the literature to probe the SFR of all type of galaxies. Using a sample of GOODS-South galaxies, we show that these SFHs artificially enhance or create a gradient of age, parallel to the MS. A simple model of a MS galaxy, such as those expected from compaction or variation in gas accretion, undergoing some fluctuations provide does not predict such a gradient, that we show is due to SFH assumptions. We propose an improved analytical form, taking into account a flexibility in the recent SFH that we calibrate as a diagnostic to identify rapidly quenched galaxies from large photometric survey.

  4. Evolution Models of Helium White Dwarf–Main-sequence Star Merger Remnants

    SciTech Connect

    Zhang, Xianfei; Bi, Shaolan; Hall, Philip D.

    2017-02-01

    It is predicted that orbital decay by gravitational-wave radiation and tidal interaction will cause some close binary stars to merge within a Hubble time. The merger of a helium-core white dwarf with a main-sequence (MS) star can produce a red giant branch star that has a low-mass hydrogen envelope when helium is ignited and thus become a hot subdwarf. Because detailed calculations have not been made, we compute post-merger models with a stellar evolution code. We find the evolutionary paths available to merger remnants and find the pre-merger conditions that lead to the formation of hot subdwarfs. We find thatmore » some such mergers result in the formation of stars with intermediate helium-rich surfaces. These stars later develop helium-poor surfaces owing to diffusion. Combining our results with a model population and comparing to observed stars, we find that some observed intermediate helium-rich hot subdwarfs can be explained as the remnants of the mergers of helium-core white dwarfs with low-mass MS stars.« less

  5. DNA sequencing using biotinylated dideoxynucleotides and mass spectrometry

    PubMed Central

    Edwards, John R.; Itagaki, Yasuhiro; Ju, Jingyue

    2001-01-01

    Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MS) has been explored widely for DNA sequencing. The major requirement for this method is that the DNA sequencing fragments must be free from alkaline and alkaline earth salts as well as other contaminants for accurately measuring the masses of the DNA fragments. We report here the development of a novel MS DNA sequencing method that generates Sanger-sequencing fragments in one tube using biotinylated dideoxynucleotides. The DNA sequencing fragments that carry a biotin at the 3′-end are made free from salts and other components in the sequencing reaction by capture with streptavidin-coated magnetic beads. Only correctly terminated biotinylated DNA fragments are subsequently released and loaded onto a mass spectrometer to obtain accurate DNA sequencing data. Compared with gel electrophoresis-based sequencing systems, MS produces a very high resolution of DNA-sequencing fragments, fast separation on microsecond time scales, and completely eliminates the compressions associated with gel electrophoresis. The high resolution of MS allows accurate mutation and heterozygote detection. This optimized solid-phase DNA-sequencing chemistry plus future improvements in detector sensitivity for large DNA fragments in MS instrumentation will further improve MS for DNA sequencing. PMID:11691941

  6. ROTATION PERIODS OF 34,030 KEPLER MAIN-SEQUENCE STARS: THE FULL AUTOCORRELATION SAMPLE

    SciTech Connect

    McQuillan, A.; Mazeh, T.; Aigrain, S., E-mail: amy@wise.tau.ac.il

    2014-04-01

    We analyzed three years of data from the Kepler space mission to derive rotation periods of main-sequence stars below 6500 K. Our automated autocorrelation-based method detected rotation periods between 0.2 and 70 days for 34,030 (25.6%) of the 133,030 main-sequence Kepler targets (excluding known eclipsing binaries and Kepler Objects of Interest), making this the largest sample of stellar rotation periods to date. In this paper we consider the detailed features of the now well-populated period-temperature distribution and demonstrate that the period bimodality, first seen by McQuillan et al. in the M-dwarf sample, persists to higher masses, becoming less visible abovemore » 0.6 M {sub ☉}. We show that these results are globally consistent with the existing ground-based rotation-period data and find that the upper envelope of the period distribution is broadly consistent with a gyrochronological age of 4.5 Gyr, based on the isochrones of Barnes, Mamajek, and Hillenbrand and Meibom et al. We also performed a detailed comparison of our results to those of Reinhold et al. and Nielsen et al., who measured rotation periods of field stars observed by Kepler. We examined the amplitude of periodic variability for the stars with detection rotation periods, and found a typical range between ∼950 ppm (5th percentile) and ∼22,700 ppm (95th percentile), with a median of ∼5600 ppm. We found typically higher amplitudes for shorter periods and lower effective temperatures, with an excess of low-amplitude stars above ∼5400 K.« less

  7. Dissecting the extended main-sequence turn-off of the young star cluster NGC 1850

    NASA Astrophysics Data System (ADS)

    Correnti, Matteo; Goudfrooij, Paul; Bellini, Andrea; Kalirai, Jason S.; Puzia, Thomas H.

    2017-05-01

    We use the Wide Field Camera 3 onboard the Hubble Space Telescope to obtain deep, high-resolution photometry of the young (˜100 Myr) star cluster NGC 1850 in the Large Magellanic Cloud. We analyse the cluster colour-magnitude diagram (CMD) and find that it hosts an extended main-sequence turn-off (MSTO) and a double main sequence (MS). We demonstrate that these features cannot be due to photometric errors, field star contamination or differential reddening. From a comparison with theoretical models and Monte Carlo simulations, we show that a coeval stellar population featuring a distribution of stellar rotation rates can reproduce the MS split quite well. However, it cannot reproduce the observed MSTO region, which is significantly wider than the simulated ones. Exploiting narrow-band Hα imaging, we find that the MSTO hosts a population of Hα-emitting stars that are interpreted as rapidly rotating Be-type stars. We explore the possibility that the discrepancy between the observed MSTO morphology and that of the simulated simple stellar population (SSP) is caused by the fraction of these objects that are highly reddened, but we rule out this hypothesis. We demonstrate that the global CMD morphology is well reproduced by a combination of SSPs that covers an age range of ˜35 Myr as well as a wide variety of rotation rates. We derive the cluster mass and escape velocity, and use dynamical evolution models to predict their evolution starting at an age of 10 Myr. We discuss these results and their implications in the context of the extended MSTO phenomenon.

  8. Pre-main-sequence Stellar Populations across Shapley Constellation III. I. Photometric Analysis and Identification

    NASA Astrophysics Data System (ADS)

    Gouliermis, Dimitrios A.; Dolphin, Andrew E.; Robberto, Massimo; Gruendl, Robert A.; Chu, You-Hua; Gennaro, Mario; Henning, Thomas; Rosa, Michael; Da Rio, Nicola; Brandner, Wolfgang; Romaniello, Martino; De Marchi, Guido; Panagia, Nino; Zinnecker, Hans

    2011-09-01

    We present our investigation of pre-main-sequence (PMS) stellar populations in the Large Magellanic Cloud (LMC) from imaging with Hubble Space Telescope Wide-Field Planetary Camera 2. Our targets of interest are four star-forming regions located at the periphery of the super-giant shell LMC 4 (Shapley Constellation III). The PMS stellar content of the regions is revealed through the differential Hess diagrams and the observed color-magnitude diagrams (CMDs). Further statistical analysis of stellar distributions along cross sections of the faint part of the CMDs allowed the quantitative assessment of the PMS stars census, and the isolation of faint PMS stars as the true low-mass stellar members of the regions. These distributions are found to be well represented by a double-Gaussian function, the first component of which represents the main-sequence field stars and the second the native PMS stars of each region. Based on this result, a cluster membership probability was assigned to each PMS star according to its CMD position. The higher extinction in the region LH 88 did not allow the unambiguous identification of its native stellar population. The CMD distributions of the PMS stars with the highest membership probability in the regions LH 60, LH 63, and LH 72 exhibit an extraordinary similarity among the regions, suggesting that these stars share common characteristics, as well as common recent star formation history. Considering that the regions are located at different areas of the edge of LMC 4, this finding suggests that star formation along the super-giant shell may have occurred almost simultaneously. Based on observations made 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 NAS 5-26555. Research supported by the National Aeronautics and Space Administration (NASA), and the German Aerospace Center (DLR).

  9. PRE-MAIN-SEQUENCE STELLAR POPULATIONS ACROSS SHAPLEY CONSTELLATION III. I. PHOTOMETRIC ANALYSIS AND IDENTIFICATION ,

    SciTech Connect

    Gouliermis, Dimitrios A.; Gennaro, Mario; Henning, Thomas

    2011-09-10

    We present our investigation of pre-main-sequence (PMS) stellar populations in the Large Magellanic Cloud (LMC) from imaging with Hubble Space Telescope Wide-Field Planetary Camera 2. Our targets of interest are four star-forming regions located at the periphery of the super-giant shell LMC 4 (Shapley Constellation III). The PMS stellar content of the regions is revealed through the differential Hess diagrams and the observed color-magnitude diagrams (CMDs). Further statistical analysis of stellar distributions along cross sections of the faint part of the CMDs allowed the quantitative assessment of the PMS stars census, and the isolation of faint PMS stars as themore » true low-mass stellar members of the regions. These distributions are found to be well represented by a double-Gaussian function, the first component of which represents the main-sequence field stars and the second the native PMS stars of each region. Based on this result, a cluster membership probability was assigned to each PMS star according to its CMD position. The higher extinction in the region LH 88 did not allow the unambiguous identification of its native stellar population. The CMD distributions of the PMS stars with the highest membership probability in the regions LH 60, LH 63, and LH 72 exhibit an extraordinary similarity among the regions, suggesting that these stars share common characteristics, as well as common recent star formation history. Considering that the regions are located at different areas of the edge of LMC 4, this finding suggests that star formation along the super-giant shell may have occurred almost simultaneously.« less

  10. Rotation Periods of 34,030 Kepler Main-sequence Stars: The Full Autocorrelation Sample

    NASA Astrophysics Data System (ADS)

    McQuillan, A.; Mazeh, T.; Aigrain, S.

    2014-04-01

    We analyzed three years of data from the Kepler space mission to derive rotation periods of main-sequence stars below 6500 K. Our automated autocorrelation-based method detected rotation periods between 0.2 and 70 days for 34,030 (25.6%) of the 133,030 main-sequence Kepler targets (excluding known eclipsing binaries and Kepler Objects of Interest), making this the largest sample of stellar rotation periods to date. In this paper we consider the detailed features of the now well-populated period-temperature distribution and demonstrate that the period bimodality, first seen by McQuillan et al. in the M-dwarf sample, persists to higher masses, becoming less visible above 0.6 M ⊙. We show that these results are globally consistent with the existing ground-based rotation-period data and find that the upper envelope of the period distribution is broadly consistent with a gyrochronological age of 4.5 Gyr, based on the isochrones of Barnes, Mamajek, & Hillenbrand and Meibom et al. We also performed a detailed comparison of our results to those of Reinhold et al. and Nielsen et al., who measured rotation periods of field stars observed by Kepler. We examined the amplitude of periodic variability for the stars with detection rotation periods, and found a typical range between ~950 ppm (5th percentile) and ~22,700 ppm (95th percentile), with a median of ~5600 ppm. We found typically higher amplitudes for shorter periods and lower effective temperatures, with an excess of low-amplitude stars above ~5400 K.

  11. AN OBJECTIVE DEFINITION FOR THE MAIN SEQUENCE OF STAR-FORMING GALAXIES

    SciTech Connect

    Renzini, Alvio; Peng, Ying-jie, E-mail: alvio.renzini@oapd.inaf.it, E-mail: y.peng@mrao.cam.ac.uk

    2015-03-10

    The main sequence (MS) of star-forming (SF) galaxies plays a fundamental role in driving galaxy evolution and our efforts to understand it. However, different studies find significant differences in the normalization, slope, and shape of the MS. These discrepancies arise mainly from the different selection criteria adopted to isolate SF galaxies, which may include or exclude galaxies with a specific star formation rate (SFR) substantially below the MS value. To obviate this limitation of all current criteria, we propose an objective definition of the MS that does not rely at all on a pre-selection of SF galaxies. Constructing the 3Dmore » SFR–mass–number plot, the MS is then defined as the ridge line of the SF peak, as illustrated with various figures. The advantages of such a definition are manifold. If generally adopted, it will facilitate the inter-comparison of results from different groups using the same SFR and stellar mass diagnostics, or it will highlight the relative systematics of different diagnostics. All of this could help to understand MS galaxies as systems in a quasi-steady state equilibrium and would also provide a more objective criterion for identifying quenching galaxies.« less

  12. The 2016-2017 peak luminosity of the pre-main sequence variable V2492 Cygni

    NASA Astrophysics Data System (ADS)

    Giannini, T.; Munari, U.; Antoniucci, S.; Lorenzetti, D.; Arkharov, A. A.; Dallaporta, S.; Rossi, A.; Traven, G.

    2018-03-01

    Context. V2492 Cyg is a young pre-main sequence star presenting repetitive brightness variations of significant amplitude (ΔR ≥ 5 mag) whose physical origin has been ascribed to both extinction (UXor-type) and accretion (EXor-type) variability, although their mutual proportion has not been clarified yet. Recently, V2492 Cyg has reached a level of brightness ever registered in the period of its documented activity. Aim. We aim to derive the variation of the mass accretion rate between low- and high-state and to get new insights on the origin of the variability of V2492 Cyg. Methods: Optical and near-infrared (NIR) photometry and spectroscopy have been obtained in October 2016 and between March and July 2017. The source has remained bright until the end of May 2017, then it started to rapidly fade since the beginning of June at a rate of 0.08 mag/day. On mid-July 2017 the source has reached the same low-brightness level as two years before. Extinction and mass accretion rate were derived by means of the luminosity of the brightest lines, in particular Hα and Hβ. A couple of optical high-resolution spectra are also presented to derive information on the gas kinematics. Results: Visual extinction variations do not exceed a few magnitudes, while the mass accretion rate is estimated to vary from less than 10-8 up to a few 10-7 M⊙ yr-1. This latter is comparable to that estimated on the previous high-state in 2010, likely occurred under more severe extinction conditions. Conclusions: The combined analysis of the optical and NIR observations extends to the present event the original suggestion that the V2492 Cyg variability is a combination of changing extinction and accretion.

  13. Laser mass spectrometry for DNA sequencing, disease diagnosis, and fingerprinting

    NASA Astrophysics Data System (ADS)

    Chen, C. H. Winston; Taranenko, N. I.; Zhu, Y. F.; Chung, C. N.; Allman, S. L.

    1997-05-01

    Since laser mass spectrometry has the potential for achieving very fast DNA analysis, we recently applied it to DNA sequencing, DNA typing for fingerprinting, and DNA screening for disease diagnosis. Two different approaches for sequencing DNA have been successfully demonstrated. One is to sequence DNA with DNA ladders produced from Sanger's enzymatic method. The other is to do direct sequencing without DNA ladders. The need for quick DNA typing for identification purposes is critical for forensic application. Our preliminary results indicate laser mass spectrometry can possible be used for rapid DNA fingerprinting applications at a much lower cost than gel electrophoresis. Population screening for certain genetic disease can be a very efficient step to reducing medical costs through prevention. Since laser mass spectrometry can provide very fast DNA analysis, we applied laser mass spectrometry to disease diagnosis. Clinical samples with both base deletion and point mutation have been tested with complete success.

  14. THE YOUNG OPEN CLUSTERS KING 12, NGC 7788, AND NGC 7790: PRE-MAIN-SEQUENCE STARS AND EXTENDED STELLAR HALOS

    SciTech Connect

    Davidge, T. J.

    2012-12-20

    The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images. Comparisons with isochrones yield an age <20 Myr for King 12, 20-40 Myr for NGC 7788, and 60-80 Myr for NGC 7790 based on the properties of stars near the main-sequence turnoff (MSTO) in each cluster. The reddening of NGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 show breaks that are attributed to the onset of pre-main-sequence (PMS) objects, and comparisons with models of PMS evolution yield ages that are consistentmore » with those measured from stars near the MSTO. In contrast, the r' LF of main-sequence stars in NGC 7790 is matched to r' = 20 by a model that is based on the solar neighborhood mass function. The structural properties of all three clusters are investigated by examining the two-point angular correlation function of blue main-sequence stars. King 12 and NGC 7788 are each surrounded by a stellar halo that extends out to a radius of 5 arcmin ({approx}3.4 pc). It is suggested that these halos form in response to large-scale mass ejection early in the evolution of the clusters, as predicted by models. In contrast, blue main-sequence stars in NGC 7790 are traced out to a radius of {approx}7.5 arcmin ({approx}5.5 pc), with no evidence of a halo. It is suggested that all three clusters may have originated in the same star-forming complex, but not in the same giant molecular cloud.« less

  15. AN M DWARF COMPANION TO AN F-TYPE STAR IN A YOUNG MAIN-SEQUENCE BINARY

    SciTech Connect

    Eigmüller, Ph.; Csizmadia, Sz.; Erikson, A.

    2016-03-15

    Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung–Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 ± 0.073) M{sub ⊙}more » and a radius of (1.474 ± 0.040) R{sub ⊙}. The companion is an M dwarf with a mass of (0.188 ± 0.014) M{sub ⊙} and a radius of (0.234 ± 0.009) R{sub ⊙}. The orbital period is (1.35121 ± 0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin–orbit synchronization. This indicates a young main-sequence binary with an age below ∼250 Myr. The mass–radius relation of both components are in agreement with this finding.« less

  16. INTRINSIC COLORS, TEMPERATURES, AND BOLOMETRIC CORRECTIONS OF PRE-MAIN-SEQUENCE STARS

    SciTech Connect

    Pecaut, Mark J.; Mamajek, Eric E.

    2013-09-01

    We present an analysis of the intrinsic colors and temperatures of 5-30 Myr old pre-main-sequence (pre-MS) stars using the F0- through M9-type members of nearby, negligibly reddened groups: the η Cha cluster, the TW Hydra Association, the β Pic Moving Group, and the Tucana-Horologium Association. To check the consistency of spectral types from the literature, we estimate new spectral types for 52 nearby pre-MS stars with spectral types F3 through M4 using optical spectra taken with the SMARTS 1.5 m telescope. Combining these new types with published spectral types and photometry from the literature (Johnson-Cousins BVI{sub C} , 2MASS JHK{submore » S} and WISE W1, W2, W3, and W4), we derive a new empirical spectral type-color sequence for 5-30 Myr old pre-MS stars. Colors for pre-MS stars match dwarf colors for some spectral types and colors, but for other spectral types and colors, deviations can exceed 0.3 mag. We estimate effective temperatures (T {sub eff}) and bolometric corrections (BCs) for our pre-MS star sample through comparing their photometry to synthetic photometry generated using the BT-Settl grid of model atmosphere spectra. We derive a new T {sub eff} and BC scale for pre-MS stars, which should be a more appropriate match for T Tauri stars than often-adopted dwarf star scales. While our new T {sub eff} scale for pre-MS stars is within ≅100 K of dwarfs at a given spectral type for stars« less

  17. Coronagraphic imaging of pre-main-sequence stars: Remnant evvelopes of star formation seen in reflection

    NASA Technical Reports Server (NTRS)

    Nakajima, Tadashi; Golimowski, David A.

    1995-01-01

    We have obtained R- and I-band coronagraphic images of the vicinities of 11 pre-main sequence (PMS) stars to search for faint, small-scale reflection nebulae. The inner radius of the search and the field of view are 1.9 arcsec and 1x1 arcmin, respectively. Reflection nebulae were imaged around RY Tau, T Tau,DG Tau, SU Aur, AB Aur, FU Ori, and Z CMa. No nebulae were detected around HBC 347, GG Tau, V773 Tau, and V830 Tau. Categorically speaking, most of the classical T Tauri program stars and all the FU Orionis-type program stars are associated with the reflection nebulae, while none of the weak-line T Tauri program stars are associated with nebulae. The detected nebulae range in size from 250 to 37 000 AU. From the brightness ratios of the stars and nebulae, we obtain a lower limit to the visual extinction of PMS star light through the nebulae of (A(sub V))(sub neb) = 0.1. The lower limits of masses and volume densities of the nebulae associated with the classical T Tauri stars are 10(exp-6) Solar mass and N(sub H) = 10(exp 5)/cu cm, respectively. Lower limits for the nebulae around FU Orionis stars are 10(exp -5) Solar mass and n(sub H) = 10 (exp 5)/cu cm, respectively. Some reflection nebulae may trace the illuminated surfaces of the optically thick dust nebulae, so these mass estimates are not stringent. All the PMS stars with associated nebulae are strong far-infrared emitters. Both the far-infrared emission and the reflection nebulae appear to originate from the remnant envelopes of star formation. The 100 micrometers emitting regions of SU Aur and FU Ori are likely to be cospatial with the reflection nebulae. A spatial discontinuity between FU Ori and its reflection nebula may explain the dip in the far-infrared spectral energy distribution at 60 micrometers. The warped, disk-like nebulae around T Tau and Z CMa are aligned with and embrace the inner star/circumstellar disk systems. The arc-shaped nebula around DG Tau may be in contact with the coaligned inner

  18. The pre-main-sequence eclipsing binary ASAS J052821+0338.5

    NASA Astrophysics Data System (ADS)

    Stempels, H. C.; Hebb, L.; Stassun, K. G.; Holtzman, J.; Dunstone, N.; Glowienka, L.; Frandsen, S.

    2008-04-01

    Aims: In this paper we present the first results of a detailed spectroscopic and photometric analysis of the V = 11.7m eclipsing binary ASAS J052821+0338.5. Methods: With the FIES spectrograph at the Nordic Optical Telescope, we obtained a series of high-resolution spectra (R ≈ 47 000) covering the entire orbit of the system. In addition we obtained simultaneous broadband photometry from three small aperture telescopes. From these spectroscopic and photometric data we have derived the system's orbital parameters and determined the fundamental stellar parameters of the two components. Results: Our results indicate that ASAS J052821+0338.5 is a K1/K3 pre-main-sequence eclipsing binary, with component masses of 1.38 {M}⊙ and 1.33 {M}⊙ and a period of 3.87 days, located at a distance of 280 ± 30 pc. The kinematics, physical location, and the evolutionary status of the two stars suggest that ASAS J052821+0338.5 is a member of the 11 Myr old Orion OB1a subassociation. The systems also exhibits smooth 0.15m out-of-eclipse variations that are similar to those found in RS CVn binaries. Furthermore, the parameters we derived are consistent with the 10-13 Myr isochrones of the popular Baraffe stellar evolutionary models. Based on observations made with the Nordic Optical Telescope.

  19. The population of white dwarf-main sequence binaries in the SDSS DR 12

    NASA Astrophysics Data System (ADS)

    Cojocaru, R.; Rebassa-Mansergas, A.; Torres, S.; García-Berro, E.

    2017-09-01

    We present a Monte Carlo population synthesis study of white dwarf-main sequence (WD+MS) binaries in the Galactic disc aimed at reproducing the ensemble properties of the entire population observed by the Sloan Digital Sky Survey (SDSS) Data Release 12. Our simulations take into account all known observational biases and use the most up-to-date stellar evolutionary models. This allows us to perform a sound comparison between the simulations and the observational data. We find that the properties of the simulated and observed parameter distributions agree best when assuming low values of the common envelope efficiency (0.2-0.3), a result that is in agreement with previous findings obtained by observational and population synthesis studies of close SDSS WD+MS binaries. We also show that all synthetic populations that result from adopting an initial mass ratio distribution with a positive slope are excluded by observations. Finally, we confirm that the properties of the simulated WD+MS binary populations are nearly independent of the age adopted for the thin disc, on the contribution of WD+MS binaries from the thick disc (0-17 per cent of the total population) and on the assumed fraction of the internal energy that is used to eject the envelope during the common envelope phase (0.1-0.5).

  20. Pulsations and metallicity of the pre-main sequence eclipsing spectroscopic binary RS Cha

    NASA Astrophysics Data System (ADS)

    Alecian, E.; Catala, C.; van't Veer-Menneret, C.; Goupil, M.-J.; Balona, L.

    2005-11-01

    We present new spectroscopic observations of the pre-main sequence eclipsing spectroscopic binary RS Cha. A sample of 174 spectra were obtained with the GIRAFFE spectrograph at the SAAO at 32 000 resolution. The radial velocity curves derived from these spectra were combined with previous observations spanning a period of about 30 years to correct the ephemeris of the system, and the result indicates that the orbital period is not constant. Residuals of the binary radial velocity curve for both components with amplitudes up to a few km s-1 and periods on the order of 1 h are clearly seen in our data, which we interpret as the signatures of delta-Scuti type pulsations. We revisited the masses of both components and determined the surface metallicity Z of both components of the RS Cha system by fitting synthetic spectra to observed spectra in a set of selected spectral regions. The synthetic spectra are calculated with the SYNTH code using stellar atmosphere models computed with the Kurucz ATLAS 9 code, along with a list of lines obtained from the VALD database. A selection of the best spectra and the most relevant spectral regions allowed us to determine Z = 0.028 ± 0.005. We also derived new values of v sin i: 64 ± 6 km s-1 and 70 ± 6 km s-1 for the primary and the secondary star, respectively. Finally, we observationally confirm that the RS Cha system is a synchronized and circularized system.

  1. WHITE-DWARF-MAIN-SEQUENCE BINARIES IDENTIFIED FROM THE LAMOST PILOT SURVEY

    SciTech Connect

    Ren Juanjuan; Luo Ali; Li Yinbi

    2013-10-01

    We present a set of white-dwarf-main-sequence (WDMS) binaries identified spectroscopically from the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) pilot survey. We develop a color selection criteria based on what is so far the largest and most complete Sloan Digital Sky Survey (SDSS) DR7 WDMS binary catalog and identify 28 WDMS binaries within the LAMOST pilot survey. The primaries in our binary sample are mostly DA white dwarfs except for one DB white dwarf. We derive the stellar atmospheric parameters, masses, and radii for the two components of 10 of our binaries.more » We also provide cooling ages for the white dwarf primaries as well as the spectral types for the companion stars of these 10 WDMS binaries. These binaries tend to contain hot white dwarfs and early-type companions. Through cross-identification, we note that nine binaries in our sample have been published in the SDSS DR7 WDMS binary catalog. Nineteen spectroscopic WDMS binaries identified by the LAMOST pilot survey are new. Using the 3{sigma} radial velocity variation as a criterion, we find two post-common-envelope binary candidates from our WDMS binary sample.« less

  2. Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars

    NASA Astrophysics Data System (ADS)

    Gontcharov, George A.; Mosenkov, Aleksandr V.

    2017-12-01

    We compare eight sources of reddening and extinction estimates for approximately 60 000 Gaia DR1 Tycho-Gaia Astrometric Solution (TGAS) main sequence stars younger than 3 Gyr with a relative error of the Gaia parallax less than 0.1. For the majority of the stars, the best 2D dust emission-based reddening maps show considerable differences between the reddening to infinity and the one calculated to the stellar distance using the barometric law of the dust distribution. This proves that the majority of the TGAS stars are embedded in the Galactic dust layer and a proper 3D treatment of the reddening/extinction is required to calculate their dereddened colours and absolute magnitudes reliably. Sources with 3D estimates of reddening are tested in their ability to put the stars among the PARSEC and MIST theoretical isochrones in the Hertzsprung-Russell diagram based on the precise Gaia, Tycho-2, 2MASS and WISE photometry. Only the reddening/extinction estimates by Arenou et al. and Gontcharov, being appropriate for nearby stars within 280 pc, provide both the minimal number of outliers bluer than any reasonable isochrone and the correct number of stars younger than 3 Gyr in agreement with the Besançon Galaxy model.

  3. YSOVAR: SIX PRE-MAIN-SEQUENCE ECLIPSING BINARIES IN THE ORION NEBULA CLUSTER

    SciTech Connect

    Morales-Calderon, M.; Stauffer, J. R.; Rebull, L. M.

    2012-07-10

    Eclipsing binaries (EBs) provide critical laboratories for empirically testing predictions of theoretical models of stellar structure and evolution. Pre-main-sequence (PMS) EBs are particularly valuable, both due to their rarity and the highly dynamic nature of PMS evolution, such that a dense grid of PMS EBs is required to properly calibrate theoretical PMS models. Analyzing multi-epoch, multi-color light curves for {approx}2400 candidate Orion Nebula Cluster (ONC) members from our Warm Spitzer Exploration Science Program YSOVAR, we have identified 12 stars whose light curves show eclipse features. Four of these 12 EBs are previously known. Supplementing our light curves with follow-up opticalmore » and near-infrared spectroscopy, we establish two of the candidates as likely field EBs lying behind the ONC. We confirm the remaining six candidate systems, however, as newly identified ONC PMS EBs. These systems increase the number of known PMS EBs by over 50% and include the highest mass ({theta}{sup 1} Ori E, for which we provide a complete set of well-determined parameters including component masses of 2.807 and 2.797 M{sub Sun }) and longest-period (ISOY J053505.71-052354.1, P {approx} 20 days) PMS EBs currently known. In two cases ({theta}{sup 1} Ori E and ISOY J053526.88-044730.7), enough photometric and spectroscopic data exist to attempt an orbit solution and derive the system parameters. For the remaining systems, we combine our data with literature information to provide a preliminary characterization sufficient to guide follow-up investigations of these rare, benchmark systems.« less

  4. High Dispersion Line Profile Studies of TW HYA and Other Pre-Main Sequence Stars

    NASA Astrophysics Data System (ADS)

    Linsky, Jeffrey L.

    1984-07-01

    We propose to extend our study of line profiles in T Tauri stars by obtaining a 16 hour SWP-HI spectrum of TW Hya and 6-8 hour LWP-HI spectra of TW Hya, AK Sco, CoD -35 10525 and CoD -33 10685. High dispersion spectra of pre-main sequence (PMS) stars provide unique information on line widths, shifts, and asymmetries, as well as evidence for mass outflow, circumstellar absorption, and diagnostics for the temperature structure of the outer atmosphere layers of these complex yet incredibly important objects. We have previously obtained and studied line profiles in RU Lupi and the prototype star T Tau. RU Lupi has line profiles that are dominated by the wind expansion, for example the MgII and FeII multiplet UV1 profiles are unique in that they have a classical P Cygni shape, whereas T Tau has more symmetric emission profiles indicative of a chromosphere and hotter layers not dominated by expansion. TW Hya is different from these two previously studied stars in that it may be the brightest known example of a post-T Tauri star, and hence less active and older than the other PMS stars. We intend to compare its line profiles with those of RU Lupi and T Tauri in order to understand the differences in the non-thermal mass motions, wind expansion, and thermal structures of these three very different T Tau stars. The requested LWPHI spectra are to obtain MgII and FeII multiplet UV1. profiles of 4 different T Tauri objects so as to infer the expansion and thermal structure in their chromospheric layers.

  5. Variations of the ISM conditions accross the Main Sequence of star forming galaxies: observations and simulations.

    NASA Astrophysics Data System (ADS)

    Martinez Galarza, Juan R.; Smith, Howard Alan; Lanz, Lauranne; Hayward, Christopher C.; Zezas, Andreas; Hung, Chao-Ling; Rosenthal, Lee; Weiner, Aaron

    2015-01-01

    A significant amount of evidence has been gathered that leads to the existence of a main sequence (MS) of star formation in galaxies. This MS is expressed in terms of a correlation between the SFR and the stellar mass of the form SFR ∝ M* and spans a few orders of magnitude in both quantities. Several ideas have been suggested to explain fundamental properties of the MS, such as its slope, its dispersion, and its evolution with redshift, but no consensus has been reached regarding its true nature, and whether the membership or not of particular galaxies to this MS underlies the existence of two different modes of star formation. In order to advance in the understanding of the MS, here we use a statistically robust Bayesian SED analysis method (CHIBURST) to consistently analyze the star-forming properties of a set of hydro-dynamical simulations of mergers, as well as observations of real mergers, both local and at intermediate redshift. We find a remarkable, very tight correlation between the specific star formation rate (sSFR) of galaxies, and the typical ISM conditions near their inernal star-forming regions, parametrized via a novel quantity: the compactness parameter (C). The evolution of mergers along this correlation explains the spread of the MS, and implies that the physical conditions of the ISM smoothly evolve between on-MS (secular) conditions and off-MS (coalescence/starburst) conditions. Furthermore, we show that the slope of the correlation can be interpreted in terms of the efficiency in the conversion of gas into stars, and that this efficiency remains unchanged along and across the MS. Finally, we discuss differences in the normalization of the correlation as a function of merger mass and redshift, and conclude that these differences imply the existence of two different modes of star formation, unrelated to the smooth evolution across the MS: a disk-like, low pressure mode and a compact nuclear-starburst mode.

  6. Tandem Mass Spectrum Sequencing: An Alternative to Database Search Engines in Shotgun Proteomics.

    PubMed

    Muth, Thilo; Rapp, Erdmann; Berven, Frode S; Barsnes, Harald; Vaudel, Marc

    2016-01-01

    Protein identification via database searches has become the gold standard in mass spectrometry based shotgun proteomics. However, as the quality of tandem mass spectra improves, direct mass spectrum sequencing gains interest as a database-independent alternative. In this chapter, the general principle of this so-called de novo sequencing is introduced along with pitfalls and challenges of the technique. The main tools available are presented with a focus on user friendly open source software which can be directly applied in everyday proteomic workflows.

  7. A near-infrared survey for pre-main sequence stars in Taurus

    NASA Technical Reports Server (NTRS)

    Gomez, Mercedes; Kenyon, Scott J.; Hartmann, Lee

    1994-01-01

    We present a near-infrared survey of approximately 2 sq deg covering parts of L1537, L1538, and Heiles cloud 2 in the Taurus-Auriga molecular cloud. Although this study is more sensitive than previous attempts to identify pre-main sequence stars in Taurus-Auriga, our survey regions contain only one new optically visible, young star. We did find several candidate embedded protostars; additional 10 micrometer photometry is necessary to verify the pre-main sequence nature of these sources. Our results--combined with those of previous surveys--show that the L1537/L1538 clouds contain no pre-main sequence stars. These two clouds are less dense than the active star formation sites in Taurus-Auriga, which suggests a cloud must achieve a threshold density to form stars.

  8. Sequence protein identification by randomized sequence database and transcriptome mass spectrometry (SPIDER-TMS): from manual to automatic application of a 'de novo sequencing' approach.

    PubMed

    Pascale, Raffaella; Grossi, Gerarda; Cruciani, Gabriele; Mecca, Giansalvatore; Santoro, Donatello; Sarli Calace, Renzo; Falabella, Patrizia; Bianco, Giuliana

    Sequence protein identification by a randomized sequence database and transcriptome mass spectrometry software package has been developed at the University of Basilicata in Potenza (Italy) and designed to facilitate the determination of the amino acid sequence of a peptide as well as an unequivocal identification of proteins in a high-throughput manner with enormous advantages of time, economical resource and expertise. The software package is a valid tool for the automation of a de novo sequencing approach, overcoming the main limits and a versatile platform useful in the proteomic field for an unequivocal identification of proteins, starting from tandem mass spectrometry data. The strength of this software is that it is a user-friendly and non-statistical approach, so protein identification can be considered unambiguous.

  9. Empirical tests of pre-main-sequence stellar evolution models with eclipsing binaries

    NASA Astrophysics Data System (ADS)

    Stassun, Keivan G.; Feiden, Gregory A.; Torres, Guillermo

    2014-06-01

    We examine the performance of standard pre-main-sequence (PMS) stellar evolution models against the accurately measured properties of a benchmark sample of 26 PMS stars in 13 eclipsing binary (EB) systems having masses 0.04-4.0 M⊙ and nominal ages ≈1-20 Myr. We provide a definitive compilation of all fundamental properties for the EBs, with a careful and consistent reassessment of observational uncertainties. We also provide a definitive compilation of the various PMS model sets, including physical ingredients and limits of applicability. No set of model isochrones is able to successfully reproduce all of the measured properties of all of the EBs. In the H-R diagram, the masses inferred for the individual stars by the models are accurate to better than 10% at ≳1 M⊙, but below 1 M⊙ they are discrepant by 50-100%. Adjusting the observed radii and temperatures using empirical relations for the effects of magnetic activity helps to resolve the discrepancies in a few cases, but fails as a general solution. We find evidence that the failure of the models to match the data is linked to the triples in the EB sample; at least half of the EBs possess tertiary companions. Excluding the triples, the models reproduce the stellar masses to better than ∼10% in the H-R diagram, down to 0.5 M⊙, below which the current sample is fully contaminated by tertiaries. We consider several mechanisms by which a tertiary might cause changes in the EB properties and thus corrupt the agreement with stellar model predictions. We show that the energies of the tertiary orbits are comparable to that needed to potentially explain the scatter in the EB properties through injection of heat, perhaps involving tidal interaction. It seems from the evidence at hand that this mechanism, however it operates in detail, has more influence on the surface properties of the stars than on their internal structure, as the lithium abundances are broadly in good agreement with model predictions. The

  10. The SFR-M∗ main sequence archetypal star-formation history and analytical models

    NASA Astrophysics Data System (ADS)

    Ciesla, L.; Elbaz, D.; Fensch, J.

    2017-12-01

    The star-formation history (SFH) of galaxies is a key assumption to derive their physical properties and can lead to strong biases. In this work, we derive the SFH of main sequence (MS) galaxies and show how the peak SFH of a galaxy depends on its seed mass at, for example, z = 5. This seed mass reflects the galaxy's underlying dark matter (DM) halo environment. We show that, following the MS, galaxies undergo a drastic slow down of their stellar mass growth after reaching the peak of their SFH. According to abundance matching, these masses correspond to hot and massive DM halos which state could result in less efficient gas inflows on the galaxies and thus could be the origin of limited stellar mass growth. As a result, we show that galaxies, still on the MS, can enter the passive region of the UVJ diagram while still forming stars. The best fit to the MS SFH is provided by a right skew peak function for which we provide parameters depending on the seed mass of the galaxy. The ability of the classical analytical SFHs to retrieve the star-formation rate (SFR) of galaxies from spectral energy distribution (SED) fitting is studied. Due to mathematical limitations, the exponentially declining and delayed SFH struggle to model high SFR, which starts to be problematic at z > 2. The exponentially rising and log-normal SFHs exhibit the opposite behavior with the ability to reach very high SFR, and thus model starburst galaxies, but they are not able to model low values such as those expected at low redshift for massive galaxies. By simulating galaxies SED from the MS SFH, we show that these four analytical forms recover the SFR of MS galaxies with an error dependent on the model and the redshift. They are, however, sensitive enough to probe small variations of SFR within the MS, with an error ranging from 5 to 40% depending on the SFH assumption and redshift; but all the four fail to recover the SFR of rapidly quenched galaxies. However, these SFHs lead to an artificial

  11. EXPORT: Optical photometry and polarimetry of Vega-type and pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Oudmaijer, R. D.; Palacios, J.; Eiroa, C.; Davies, J. K.; de Winter, D.; Ferlet, R.; Garzón, F.; Grady, C. A.; Collier Cameron, A.; Deeg, H. J.; Harris, A. W.; Horne, K.; Merín, B.; Miranda, L. F.; Montesinos, B.; Mora, A.; Penny, A.; Quirrenbach, A.; Rauer, H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.

    2001-11-01

    This paper presents optical UBVRI broadband photo-polarimetry of the EXPORT sample obtained at the 2.5 m Nordic Optical Telescope. The database consists of multi-epoch photo-polarimetry of 68 pre-main-sequence and main-sequence stars. An investigation of the polarization variability indicates that 22 objects are variable at the 3sigma level in our data. All these objects are pre-main sequence stars, consisting of both T Tauri and Herbig Ae/Be objects while the main sequence, Vega type and post-T Tauri type objects are not variable. The polarization properties of the variable sources are mostly indicative of the UXOR-type behaviour; the objects show highest polarization when the brightness is at minimum. We add seven new objects to the class of UXOR variables (BH Cep, VX Cas, DK Tau, HK Ori, LkHα 234, KK Oph and RY Ori). The main reason for their discovery is the fact that our data-set is the largest in its kind, indicating that many more young UXOR-type pre-main sequence stars remain to be discovered. The set of Vega-like systems has been investigated for the presence of intrinsic polarization. As they lack variability, this was done using indirect methods, and apart from the known case of BD+31o643, the following stars were found to be strong candidates to exhibit polarization due to the presence of circumstellar disks: 51 Oph, BD+31o643C, HD 58647 and HD 233517. Table A1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/379/564

  12. Main-sequence Stars Masquerading as Young Stellar Objects in the Central Molecular Zone

    NASA Astrophysics Data System (ADS)

    Koepferl, Christine M.; Robitaille, Thomas P.; Morales, Esteban F. E.; Johnston, Katharine G.

    2015-01-01

    In contrast to most other galaxies, star formation rates in the Milky Way can be estimated directly from young stellar objects (YSOs). In the central molecular zone the star formation rate calculated from the number of YSOs with 24 μm emission is up to an order of magnitude higher than the value estimated from methods based on diffuse emission (such as free-free emission). Whether this effect is real or whether it indicates problems with either or both star formation rate measures is not currently known. In this paper, we investigate whether estimates based on YSOs could be heavily contaminated by more evolved objects such as main-sequence stars. We present radiative transfer models of YSOs and of main-sequence stars in a constant ambient medium which show that the main-sequence objects can indeed mimic YSOs at 24 μm. However, we show that in some cases the main-sequence models can be marginally resolved at 24 μm, whereas the YSO models are always unresolved. Based on the fraction of resolved MIPS 24 μm sources in the sample of YSOs previously used to compute the star formation rate, we estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the star formation rate previously determined from YSOs is likely to be at least a factor of three too high.

  13. MAIN-SEQUENCE STARS MASQUERADING AS YOUNG STELLAR OBJECTS IN THE CENTRAL MOLECULAR ZONE

    SciTech Connect

    Koepferl, Christine M.; Robitaille, Thomas P.; Morales, Esteban F. E.

    2015-01-20

    In contrast to most other galaxies, star formation rates in the Milky Way can be estimated directly from young stellar objects (YSOs). In the central molecular zone the star formation rate calculated from the number of YSOs with 24 μm emission is up to an order of magnitude higher than the value estimated from methods based on diffuse emission (such as free-free emission). Whether this effect is real or whether it indicates problems with either or both star formation rate measures is not currently known. In this paper, we investigate whether estimates based on YSOs could be heavily contaminated by moremore » evolved objects such as main-sequence stars. We present radiative transfer models of YSOs and of main-sequence stars in a constant ambient medium which show that the main-sequence objects can indeed mimic YSOs at 24 μm. However, we show that in some cases the main-sequence models can be marginally resolved at 24 μm, whereas the YSO models are always unresolved. Based on the fraction of resolved MIPS 24 μm sources in the sample of YSOs previously used to compute the star formation rate, we estimate the fraction of misclassified ''YSOs'' to be at least 63%, which suggests that the star formation rate previously determined from YSOs is likely to be at least a factor of three too high.« less

  14. Laser Desorption Mass Spectrometry for DNA Sequencing and Analysis

    NASA Astrophysics Data System (ADS)

    Chen, C. H. Winston; Taranenko, N. I.; Golovlev, V. V.; Isola, N. R.; Allman, S. L.

    1998-03-01

    Rapid DNA sequencing and/or analysis is critically important for biomedical research. In the past, gel electrophoresis has been the primary tool to achieve DNA analysis and sequencing. However, gel electrophoresis is a time-consuming and labor-extensive process. Recently, we have developed and used laser desorption mass spectrometry (LDMS) to achieve sequencing of ss-DNA longer than 100 nucleotides. With LDMS, we succeeded in sequencing DNA in seconds instead of hours or days required by gel electrophoresis. In addition to sequencing, we also applied LDMS for the detection of DNA probes for hybridization LDMS was also used to detect short tandem repeats for forensic applications. Clinical applications for disease diagnosis such as cystic fibrosis caused by base deletion and point mutation have also been demonstrated. Experimental details will be presented in the meeting. abstract.

  15. Analysis of flares in the chromosphere and corona of main- and pre-main-sequence M-type stars

    NASA Astrophysics Data System (ADS)

    Crespo-Chacón, I.

    2015-11-01

    This Ph.D. Thesis revolves around flares on main- and pre-main-sequence M-type stars. We use observations in different wavelength ranges with the aim of analysing the effects of flares at different layers of stellar atmospheres. In particular, optical and X-ray observations are used so that we can study how flares affect, respectively, the chromosphere and the corona of stars. In the optical range we carry out a high temporal resolution spectroscopic monitoring of UV Ceti-type stars aimed at detecting non-white-light flares (the most typical kind of solar flares) in stars other than the Sun. With these data we confirm that non-white-light flares are a frequent phenomenon in UV Ceti-type stars, as observed in the Sun. We study and interpret the behaviour of different chromospheric lines during the flares detected on AD Leo. By using a simplified slab model of flares (Jevremović et al. 1998), we are able to determine the physical parameters of the chromospheric flaring plasma (electron density and electron temperature), the temperature of the underlying source, and the surface area covered by the flaring plasma. We also search for possible relationships between the physical parameters of the flaring plasma and other properties such as the flare duration, area, maximum flux and released energy. This work considerably extends the existing sample of stellar flares analysed with good quality spectroscopy in the optical range. In X-rays we take advantage of the great sensitivity, wide energy range, high energy resolution, and continuous time coverage of the EPIC detectors - on-board the XMMNewton satellite - in order to perform time-resolved spectral analysis of coronal flares. In particular, in the UV Ceti-type star CC Eri we study two flares that are weaker than those typically reported in the literature (allowing us to speculate about the role of flares as heating agents of stellar atmospheres); while in the pre-main-sequence M-type star TWA 11B (with no signatures of

  16. Dynamical Formation of Close Binaries during the Pre-main-sequence Phase

    NASA Astrophysics Data System (ADS)

    Moe, Maxwell; Kratter, Kaitlin M.

    2018-02-01

    Solar-type binaries with short orbital periods ({P}{close}\\equiv 1{--}10 days a ≲ 0.1 au) cannot form directly via fragmentation of molecular clouds or protostellar disks, yet their component masses are highly correlated, suggesting interaction during the pre-main-sequence (pre-MS) phase. Moreover, the close binary fraction of pre-MS stars is consistent with that of their MS counterparts in the field ({F}{close}=2.1 % ). Thus, we can infer that some migration mechanism operates during the early pre-MS phase (τ ≲ 5 Myr) that reshapes the primordial separation distribution. We test the feasibility of this hypothesis by carrying out a population synthesis calculation which accounts for two formation channels: Kozai–Lidov (KL) oscillations and dynamical instability in triple systems. Our models incorporate (1) more realistic initial conditions compared to previous studies, (2) octupole-level effects in the secular evolution, (3) tidal energy dissipation via weak-friction equilibrium tides at small eccentricities and via non-radial dynamical oscillations at large eccentricities, and (4) the larger tidal radius of a pre-MS primary. Given a 15% triple-star fraction, we simulate a close binary fraction from KL oscillations alone of {F}{close}≈ 0.4 % after τ = 5 Myr, which increases to {F}{close}≈ 0.8 % by τ = 5 Gyr. Dynamical ejections and disruptions of unstable coplanar triples in the disk produce solitary binaries with slightly longer periods P ≈ 10–100 days. The remaining ≈60% of close binaries with outer tertiaries, particularly those in compact coplanar configurations with log {P}{out} (days) ≈ 2–5 ({a}{out}< 50 au), can be explained only with substantial extra energy dissipation due to interactions with primordial gas.

  17. X-ray Emission from Pre-Main-Sequence Stars - Testing the Solar Analogy

    NASA Technical Reports Server (NTRS)

    Skinner, Stephen L.

    2000-01-01

    This LTSA award funded my research on the origin of stellar X-ray emission and the validity of the solar-stellar analogy. This research broadly addresses the relevance of our current understanding of solar X-ray physics to the interpretation of X-ray emission from stars in general. During the past five years the emphasis has been on space-based X-ray observations of very young stars in star-forming regions (T Tauri stars and protostars), cool solar-like G stars, and evolved high-mass Wolf-Rayet (WR) stars. These observations were carried out primarily with the ASCA and ROSAT space-based observatories (and most recently with Chandra), supplemented by ground-based observations. This research has focused on the identification of physical processes that are responsible for the high levels of X-ray emission seen in pre-main-sequence (PMS) stars, active cool stars, and WR stars. A related issue is how the X-ray emission of such stars changes over time, both on short timescales of days to years and on evolutionary timescales of millions of years. In the case of the Sun it is known that magnetic fields play a key role in the production of X-rays by confining the coronal plasma in loop-like structures where it is heated to temperatures of several million K. The extent to which the magnetically-confined corona interpretation can be applied to other X-ray emitting stars is the key issue that drives the research summarized here.

  18. X-ray emission from near-main-sequence B stars

    NASA Technical Reports Server (NTRS)

    Cassinelli, J. P.; Cohen, D. H.; Macfarlane, J. J.; Sanders, W. T.; Welsh, B. Y.

    1994-01-01

    Results of a Roengten Satellite (ROSAT) X-ray survey of 12 nearby near-main-sequence B stars are presented. Objects with very low interstellar hydrogen column density were chosen to study the soft X-ray emission properties of the stars. All of the stars were detected at the 3 sigma level. Spectral fits to seven of the stars are presented, and temperatures and source emission measures are derived. The spectra and characterized by emission from gas at a temperature of about 2 x 10(exp 6) K, which is lower than that typically observed for O stars. The ratio L(sub x)/L(sub Bol) decreases sharply with spectral types later than B1, reaching values of about 10(exp -9) at B3 V; much less than the value of 10(exp -7) that holds for O stars and early-B stars. The survey includes four beta Cephei stars and two Be stars. Our observations are consistent with the finding that beta Cephei variables have softer spectra than other stars of the same spectral type. The X-ray emission measures for the stars are compared with upper and lower limits derived using mass loss rates and terminal velocities from line-driven wind theory. It is concluded that if shocks embedded in the winds are the source of the X-ray emission then a significant fraction of the winds in B stars must be hot. One to a few shocks can account for the observed emission measures. As a function of spectral type, there appears to be a transition in X-ray emission properties at about B1 to B1.5, with later type stars having a smaller L(sub x)/L(sub Bol) ratio. Coronal and shock models are discussed in regards to the BO V star tau Sco which has an anomalously high source temperature.

  19. White dwarf-main sequence binaries from LAMOST: the DR5 catalogue

    NASA Astrophysics Data System (ADS)

    Ren, J.-J.; Rebassa-Mansergas, A.; Parsons, S. G.; Liu, X.-W.; Luo, A.-L.; Kong, X.; Zhang, H.-T.

    2018-03-01

    We present the data release (DR) 5 catalogue of white dwarf-main sequence (WDMS) binaries from the Large Area Multi-Object fiber Spectroscopic Telescope (LAMOST). The catalogue contains 876 WDMS binaries, of which 757 are additions to our previous LAMOST DR1 sample and 357 are systems that have not been published before. We also describe a LAMOST-dedicated survey that aims at obtaining spectra of photometrically-selected WDMS binaries from the Sloan Digital Sky Survey (SDSS) that are expected to contain cool white dwarfs and/or early type M dwarf companions. This is a population under-represented in previous SDSS WDMS binary catalogues. We determine the stellar parameters (white dwarf effective temperatures, surface gravities and masses, and M dwarf spectral types) of the LAMOST DR5 WDMS binaries and make use of the parameter distributions to analyse the properties of the sample. We find that, despite our efforts, systems containing cool white dwarfs remain under-represented. Moreover, we make use of LAMOST DR5 and SDSS DR14 (when available) spectra to measure the Na I λλ 8183.27, 8194.81 absorption doublet and/or Hα emission radial velocities of our systems. This allows identifying 128 binaries displaying significant radial velocity variations, 76 of which are new. Finally, we cross-match our catalogue with the Catalina Surveys and identify 57 systems displaying light curve variations. These include 16 eclipsing systems, two of which are new, and nine binaries that are new eclipsing candidates. We calculate periodograms from the photometric data and measure (estimate) the orbital periods of 30 (15) WDMS binaries.

  20. Comparison of the main sequence of reflexive saccades and the quick phases of optokinetic nystagmus.

    PubMed

    Garbutt, S; Harwood, M R; Harris, C M

    2001-12-01

    Abnormalities in the saccadic main sequence are an important finding and may indicate pathology of the ocular motor periphery or central neurological disorders. In young or uncooperative patients it can be difficult eliciting a sufficient number of saccades to measure the main sequence. It is often assumed that the quick phases of optokinetic nystagmus (OKN) are identical to saccades. If this were the case, it would be feasible to use OKN, an involuntary response that is easily evoked, as a simple way of eliciting many saccades. The aim of this study was to determine whether reflexive saccades and the quick phases of OKN are indeed identical, and whether OKN quick phases could have a clinical role in identifying patients with slow saccades. OKN and reflexive saccades were recorded from 10 healthy adults using an infrared limbus eye tracker and bitemporal DC electro-oculography simultaneously. OKN was stimulated by rotating a full field patterned curtain around the subject at 10-50 degrees /s. Reflexive saccades were elicited to red LED targets at 5-20 degrees eccentricity. OKN quick phases tended to have a longer duration compared to saccades, but these differences were not significant. OKN quick phases had a slightly lower peak velocity compared to saccades, which was statistically significant (p<0.05). The main sequence for duration is the same for reflexive saccades and OKN quick phases. The main sequence for peak velocity is slightly faster for reflexive saccades than OKN quick phases, but the difference is unlikely to be of clinical significance. As an illustration of the potential of this technique, the authors demonstrate that OKN quick phases show similar slowness to saccades in a child with brainstem pathology caused by Gaucher disease type III. It is concluded that recording OKN may be a simple clinical means for approximating the main sequence.

  1. EXPORT: Near-IR observations of Vega-type and pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Eiroa, C.; Garzón, F.; Alberdi, A.; de Winter, D.; Ferlet, R.; Grady, C. A.; Collier Cameron, A.; Davies, J. K.; Deeg, H. J.; Harris, A. W.; Horne, K.; Merín, B.; Miranda, L. F.; Montesinos, B.; Mora, A.; Oudmaijer, R.; Palacios, J.; Penny, A.; Quirrenbach, A.; Rauer, H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.

    2001-01-01

    We present near-IR JHK photometric data of a sample of 58 main-sequence, mainly Vega-type, and pre-main sequence stars. The data were taken during four observing runs in the period May 1998 to January 1999 and form part of a coordinated effort with simultaneous optical spectroscopy and photo-polarimetry. The near-IR colors of the MS stars correspond in most cases to photospheric colors, although noticeable reddening is present towards a few objects, and these stars show no brightness variability within the observational errors. On the other hand, the PMS stars show near-IR excesses and variability consistent with previous data. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/110

  2. Kepler-4b: A Hot Neptune-Like Planet of a G0 Star Near Main-Sequence Turnoff

    DTIC Science & Technology

    2010-04-20

    given model grid and performing a conventional (e.g., “ amoeba ”) hill- climbing optimization search. Estimating errors and verifying that the search has...considerably away from the zero-age main sequence. Applying the ρ∗ method confirms this conclusion, and in fact finds a range of model parameters, all of...planet has a 10% by mass envelope of H and He, and “non- irradiated” corresponds roughly to the case of GJ436b and cooler. The fact that Kepler-4b and

  3. Stellar Ages and Convective Cores in Field Main-sequence Stars: First Asteroseismic Application to Two Kepler Targets

    NASA Astrophysics Data System (ADS)

    Silva Aguirre, V.; Basu, S.; Brandão, I. M.; Christensen-Dalsgaard, J.; Deheuvels, S.; Doğan, G.; Metcalfe, T. S.; Serenelli, A. M.; Ballot, J.; Chaplin, W. J.; Cunha, M. S.; Weiss, A.; Appourchaux, T.; Casagrande, L.; Cassisi, S.; Creevey, O. L.; García, R. A.; Lebreton, Y.; Noels, A.; Sousa, S. G.; Stello, D.; White, T. R.; Kawaler, S. D.; Kjeldsen, H.

    2013-06-01

    Using asteroseismic data and stellar evolution models we obtain the first detection of a convective core in a Kepler field main-sequence star, putting a stringent constraint on the total size of the mixed zone and showing that extra mixing beyond the formal convective boundary exists. In a slightly less massive target the presence of a convective core cannot be conclusively discarded, and thus its remaining main-sequence lifetime is uncertain. Our results reveal that best-fit models found solely by matching individual frequencies of oscillations corrected for surface effects do not always properly reproduce frequency combinations. Moreover, slightly different criteria to define what the best-fit model is can lead to solutions with similar global properties but very different interior structures. We argue that the use of frequency ratios is a more reliable way to obtain accurate stellar parameters, and show that our analysis in field main-sequence stars can yield an overall precision of 1.5%, 4%, and 10% in radius, mass, and age, respectively. We compare our results with those obtained from global oscillation properties, and discuss the possible sources of uncertainties in asteroseismic stellar modeling where further studies are still needed.

  4. Candidate Main-Sequence Stars with Debris Disks: A New Sample of Vega-like Sources

    NASA Astrophysics Data System (ADS)

    Mannings, Vincent; Barlow, Michael J.

    1998-04-01

    Vega-like sources are main-sequence stars that exhibit IR fluxes in excess of expectations for stellar photospheres, most likely due to reradiation of stellar emission intercepted by orbiting dust grains. We have identified a large sample of main-sequence stars with possible excess IR radiation by cross-correlating the Michigan Catalog of Two-dimensional Spectral Types for the HD Stars with the IRAS Faint Source Survey Catalog. Some 60 of these Vega-like sources were not found during previous surveys of the IRAS database, the majority of which employed the lower sensitivity Point Source Catalog. Here, we provide details of our search strategy, together with a preliminary examination of the full sample of Vega-like sources.

  5. On the rate of destruction of lithium in late-type main-sequence stars

    NASA Technical Reports Server (NTRS)

    Christensen-Dalsgaard, J.; Gough, D. O.; Thompson, M. J.

    1992-01-01

    It it shown that the rate of destruction of lithium by nuclear reactions in the outer mixed layers of late-type main-sequence stars depends on both the depth of the region where mixing occurs and the stratification within it. The mixed region includes and probably extends beneath the base of the convection zone. As the star evolves on the main sequence, the properties of the convection zone vary in a simple manner. If the mixed layer behaves similarly, then the mean destruction rate can easily be related to the present local value evaluated at the base of the mixed layer. In the case of the sun, it is found that if mixing is rapid compared with the nuclear destruction rate, then the mean destruction rate is approximately equal to one-half the present local value.

  6. Searching for the signatures of terrestrial planets in F-, G-type main-sequence stars

    NASA Astrophysics Data System (ADS)

    González Hernández, J. I.; Delgado-Mena, E.; Sousa, S. G.; Israelian, G.; Santos, N. C.; Adibekyan, V. Zh.; Udry, S.

    2013-04-01

    Context. Detailed chemical abundances of volatile and refractory elements have been discussed in the context of terrestrial-planet formation during in past years. Aims: The HARPS-GTO high-precision planet-search program has provided an extensive database of stellar spectra, which we have inspected in order to select the best-quality spectra available for late type stars. We study the volatile-to-refractory abundance ratios to investigate their possible relation with the low-mass planetary formation. Methods: We present a fully differential chemical abundance analysis using high-quality HARPS and UVES spectra of 61 late F- and early G-type main-sequence stars, where 29 are planet hosts and 32 are stars without detected planets. Results: As for the previous sample of solar analogs, these stars slightly hotter than the Sun also provide very accurate Galactic chemical abundance trends in the metallicity range -0.3 < [Fe/H] < 0.4. Stars with and without planets show similar mean abundance ratios. Moreover, when removing the Galactic chemical evolution effects, these mean abundance ratios, Δ [X/Fe] SUN - STARS, against condensation temperature, tend to exhibit less steep trends with nearly zero or slightly negative slopes. We have also analyzed a subsample of 26 metal-rich stars, 13 with and 13 without known planets, with spectra at S/N ~ 850, on average, in the narrow metallicity range 0.04 < [Fe/H] < 0.19. We find the similar, although not equal, abundance pattern with negative slopes for both samples of stars with and without planets. Using stars at S/N ≥ 550 provides equally steep abundance trends with negative slopes for stars both with and without planets. We revisit the sample of solar analogs to study the abundance patterns of these stars, in particular, 8 stars hosting super-Earth-like planets. Among these stars having very low-mass planets, only four of them reveal clear increasing abundance trends versus condensation temperature. Conclusions: Finally, we

  7. The Surface Brightness of Late-Type Main-Sequence Stars and the Distances to CVs

    NASA Astrophysics Data System (ADS)

    Beuermann, Klaus; Weichhold, Marc

    We present new calibrations of the surface brightness S_K of single main-sequence M stars in the K band, and S_TiO in the narrow-band lambda 7165/7500 AA TiO flux deficit, as a function of spectral type. For the cases of Z Cha and AM Her, we demonstrate that using either S_K or S_TiO yields the same distances within the uncertainties.

  8. Evolution and detectability of comet clouds during post-main-sequence stellar evolution

    NASA Astrophysics Data System (ADS)

    Stern, S. A.; Shull, J. M.; Brandt, J. C.

    1990-05-01

    The destruction of volatile-rich comet disks and Oort-type clouds around luminous post-main-sequence stars is modeled. The models are in agreement with several aspects of existing observations of water and complex molecules in the envelopes of giant and supergiant stars. If confirmed, these results would establish the common existence of Oort-type clouds around other stars and would constitute indirect evidence for sites of past planetary formation.

  9. YSOVAR: Six Pre-main-sequence Eclipsing Binaries in the Orion Nebula Cluster

    DTIC Science & Technology

    2012-06-25

    reserved. Printed in the U.S.A. YSOVAR: SIX PRE-MAIN-SEQUENCE ECLIPSING BINARIES IN THE ORION NEBULA CLUSTER M. Morales-Calderón1,2, J. R. Stauffer1, K. G...accepted 2012 April 30; published 2012 June 25 ABSTRACT Eclipsing binaries (EBs) provide critical laboratories for empirically testing predictions...identified 12 stars whose light curves show eclipse features. Four of these 12 EBs are previously known. Supplementing our light curves with follow-up

  10. SDSS-IV MaNGA: Spatially Resolved Star Formation Main Sequence and LI(N)ER Sequence

    NASA Astrophysics Data System (ADS)

    Hsieh, B. C.; Lin, Lihwai; Lin, J. H.; Pan, H. A.; Hsu, C. H.; Sánchez, S. F.; Cano-Díaz, M.; Zhang, K.; Yan, R.; Barrera-Ballesteros, J. K.; Boquien, M.; Riffel, R.; Brownstein, J.; Cruz-González, I.; Hagen, A.; Ibarra, H.; Pan, K.; Bizyaev, D.; Oravetz, D.; Simmons, A.

    2017-12-01

    We present our study on the spatially resolved Hα and M * relation for 536 star-forming and 424 quiescent galaxies taken from the MaNGA survey. We show that the star formation rate surface density ({{{Σ }}}{SFR}), derived based on the Hα emissions, is strongly correlated with the M * surface density ({{{Σ }}}* ) on kiloparsec scales for star-forming galaxies and can be directly connected to the global star-forming sequence. This suggests that the global main sequence may be a consequence of a more fundamental relation on small scales. On the other hand, our result suggests that ∼20% of quiescent galaxies in our sample still have star formation activities in the outer region with lower specific star formation rate (SSFR) than typical star-forming galaxies. Meanwhile, we also find a tight correlation between {{{Σ }}}{{H}α } and {{{Σ }}}* for LI(N)ER regions, named the resolved “LI(N)ER” sequence, in quiescent galaxies, which is consistent with the scenario that LI(N)ER emissions are primarily powered by the hot, evolved stars as suggested in the literature.

  11. Can the helium-enriched main-sequence donor scenario hide enough hydrogen to explain Type Ia supernovae?

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Wei; Stancliffe, Richard J.

    2017-09-01

    Hydrodynamical simulations predict that a large amount of hydrogen (≳0.1 M⊙) is removed from a hydrogen-rich companion star by the SN explosion in the single-degenerate scenario of Type Ia supernovae (SNe Ia). However, non-detection of hydrogen-rich material in the late-time spectra of SNe Ia suggests that the hydrogen mass stripped from the progenitor system is ≲0.001-0.058 M⊙. In this Letter, we include thermohaline mixing into self-consistent binary evolution calculations for the helium-enriched main-sequence (HEMS) donor channel of SNe Ia for the first time. We find that the swept-up hydrogen masses expected in this channel are around 0.10-0.17 M⊙, which is higher than the observational limits, although the companion star is strongly helium-enriched when the SN explodes. This presents a serious challenge to the HEMS donor channel.

  12. Discovery of magnetic A supergiants: the descendants of magnetic main-sequence B stars

    NASA Astrophysics Data System (ADS)

    Neiner, Coralie; Oksala, Mary E.; Georgy, Cyril; Przybilla, Norbert; Mathis, Stéphane; Wade, Gregg; Kondrak, Matthias; Fossati, Luca; Blazère, Aurore; Buysschaert, Bram; Grunhut, Jason

    2017-10-01

    In the context of the high resolution, high signal-to-noise ratio, high sensitivity, spectropolarimetric survey BritePol, which complements observations by the BRITE constellation of nanosatellites for asteroseismology, we are looking for and measuring the magnetic field of all stars brighter than V = 4. In this paper, we present circularly polarized spectra obtained with HarpsPol at ESO in La Silla (Chile) and ESPaDOnS at CFHT (Hawaii) for three hot evolved stars: ι Car, HR 3890 and ɛ CMa. We detected a magnetic field in all three stars. Each star has been observed several times to confirm the magnetic detections and check for variability. The stellar parameters of the three objects were determined and their evolutionary status was ascertained employing evolution models computed with the Geneva code. ɛ CMa was already known and is confirmed to be magnetic, but our modelling indicates that it is located near the end of the main sequence, I.e. it is still in a core hydrogen burning phase. ι Car and HR 3890 are the first discoveries of magnetic hot supergiants located well after the end of the main sequence on the Hertzsprung-Russell diagram. These stars are probably the descendants of main-sequence magnetic massive stars. Their current field strength (a few G) is compatible with magnetic flux conservation during stellar evolution. These results provide observational constraints for the development of future evolutionary models of hot stars including a fossil magnetic field.

  13. Post-main-sequence Evolution of Icy Minor Planets. II. Water Retention and White Dwarf Pollution around Massive Progenitor Stars

    SciTech Connect

    Malamud, Uri; Perets, Hagai B., E-mail: uri.mal@tx.technion.ac.il, E-mail: hperets@physics.technion.ac.il

    2017-06-10

    Most studies suggest that the pollution of white dwarf (WD) atmospheres arises from the accretion of minor planets, but the exact properties of polluting material, and in particular the evidence for water in some cases, are not yet understood. Here we study the water retention of small icy bodies in exo-solar planetary systems, as their respective host stars evolve through and off the main sequence and eventually become WDs. We explore, for the first time, a wide range of star masses and metallicities. We find that the mass of the WD progenitor star is of crucial importance for the retentionmore » of water, while its metallicity is relatively unimportant. We predict that minor planets around lower-mass WD progenitors would generally retain more water and would do so at closer distances from the WD than compared with high-mass progenitors. The dependence of water retention on progenitor mass and other parameters has direct implications for the origin of observed WD pollution, and we discuss how our results and predictions might be tested in the future as more observations of WDs with long cooling ages become available.« less

  14. JUPITER WILL BECOME A HOT JUPITER: CONSEQUENCES OF POST-MAIN-SEQUENCE STELLAR EVOLUTION ON GAS GIANT PLANETS

    SciTech Connect

    Spiegel, David S.; Madhusudhan, Nikku, E-mail: dave@ias.edu, E-mail: Nikku.Madhusudhan@yale.edu

    2012-09-10

    When the Sun ascends the red giant branch (RGB), its luminosity will increase and all the planets will receive much greater irradiation than they do now. Jupiter, in particular, might end up more highly irradiated than the hot Neptune GJ 436b and, hence, could appropriately be termed a 'hot Jupiter'. When their stars go through the RGB or asymptotic giant branch stages, many of the currently known Jupiter-mass planets in several-AU orbits will receive levels of irradiation comparable to the hot Jupiters, which will transiently increase their atmospheric temperatures to {approx}1000 K or more. Furthermore, massive planets around post-main-sequence starsmore » could accrete a non-negligible amount of material from the enhanced stellar winds, thereby significantly altering their atmospheric chemistry as well as causing a significant accretion luminosity during the epochs of most intense stellar mass loss. Future generations of infrared observatories might be able to probe the thermal and chemical structure of such hot Jupiters' atmospheres. Finally, we argue that, unlike their main-sequence analogs (whose zonal winds are thought to be organized in only a few broad, planetary-scale jets), red-giant hot Jupiters should have multiple, narrow jets of zonal winds and efficient day-night redistribution.« less

  15. X-ray emission regimes and rotation sequences in M 35 . An updated model of stellar activity evolution on the main sequence

    NASA Astrophysics Data System (ADS)

    Gondoin, P.

    2013-08-01

    Context. Late-type stars in young open clusters show two kinds of dependence of their X-ray emission on rotation. They also tend to group into two main sub-populations that lie on narrow sequences in diagrams where their rotation periods are plotted against their (B - V) colour indices. A correlation between these two regimes of X-ray emission and the rotation sequences has been recently observed in the M 34 open cluster. Sun-like M 34 stars also show a drop of their X-ray to bolometric luminosity ratio by about one order of magnitude at a Rossby number of about 0.3. Aims: The present study looks for similar connections between X-ray activity and rotation in an other open cluster. The aim is to consolidate a model of X-ray activity evolution on the main sequence and to provide observational constraints on dynamo processes in the interiors of late-type stars. Methods: The paper compares XMM-Newton measurements of X-ray stellar emission in M 35 with X-ray luminosity distributions derived from rotation period measurements assuming either an X-ray regime transition at a critical Rossby number or a correlation between X-ray emission regimes and rotation sequences. Results: This second hypothesis could account for the low number of M 35 stars detected in X-rays. A model of X-ray activity evolution is proposed based on the correlation. One major output is that the transition from saturated to non-saturated X-ray emission occurs at Rossby numbers between about 0.13 and 0.4 for each star depending on its mass and initial period of rotation on the ZAMS. This prediction agrees with observations of stellar X-ray emission in M 34. It explains the large range of X-ray luminosities observed among Sun-like stars in young open clusters. Conclusions: I conclude that the correlation between X-ray emission regimes and rotation sequences could be a fundamental property of the early evolution of stellar magnetic activity on the main sequence. I argue that the angular momentum

  16. White dwarf-main sequence binaries from LAMOST: the DR1 catalogue

    NASA Astrophysics Data System (ADS)

    Ren, J. J.; Rebassa-Mansergas, A.; Luo, A. L.; Zhao, Y. H.; Xiang, M. S.; Liu, X. W.; Zhao, G.; Jin, G.; Zhang, Y.

    2014-10-01

    Context. White dwarf-main sequence (WDMS) binaries are used to study several different important open problems in modern astrophysics. Aims: The Sloan Digital Sky Survey (SDSS) identified the largest catalogue of WDMS binaries currently known. However, this sample is seriously affected by selection effects and the population of systems containing cool white dwarfs and early-type companions is under-represented. Here we search for WDMS binaries within the spectroscopic data release 1 of the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) survey. LAMOST and SDSS follow different target selection algorithms. Hence, LAMOST WDMS binaries may be drawn from a different parent population and thus help in overcoming the selection effects incorporated by SDSS on the current observed population. Methods: We develop a fast and efficient routine based on the wavelet transform to identify LAMOST WDMS binaries containing a DA white dwarf and a M dwarf companion, and apply a decomposition/fitting routine to their LAMOST spectra to estimate their distances and measure their stellar parameters, namely the white dwarf effective temperatures, surface gravities and masses, and the secondary star spectral types. Results: We identify 121 LAMOST WDMS binaries, 80 of which are new discoveries, and estimate the sample to be ~90 per cent complete. The LAMOST and SDSS WDMS binaries are found to be statistically different. However, this result is not due to the different target selection criteria of both surveys, but likely a simple consequence of the different observing conditions. Thus, the LAMOST population is found at considerably shorter distances (~50-450 pc) and is dominated by systems containing early-type companions and hot white dwarfs. Conclusions: Even though WDMS binaries containing cool white dwarfs are also missed by the LAMOST survey, the LAMOST WDMS binary sample dominated by systems containing early-type companions is an important addition to the current

  17. Optical Spectroscopic Monitoring of Pre-Main Sequence Stars: The UXOr Sub-Sample

    NASA Astrophysics Data System (ADS)

    Mendigutía, Ignacio; Montesinos, Benjamín; Eiroa, Carlos; Mora, Alcione

    The EXPORT consortium carried out in 1998-1999 photo-polarimetric and spectroscopic monitoring over 74 Pre-Main Sequence (PMS) and Main Sequence (MS) stars with infrared excesses, 43 of them showing the Hα line in emission. We have measured the equivalent widths (EWs) of the Hα, [OI]6300, HeI5876 and NaID lines in 370 intermediate resolution optical spectra, obtained along four different observing campaigns, of those 43 objects. In this contribution we focus on the simultaneous spectroscopic and photometric behaviour of 12 UX-Ori type variable stars included in the sample. The main results indicate that the EW(Hα)-V correlation is a main feature of UXOrs. This correlation is also found in the [OI]6300 line in most of the objects. The variability in EW(HeI5876)-but not in the flux (F) in several cases-does not depend on the V -behaviour, as well as the complex patterns displayed in the NaI D lines. We interpret these results according to the dusty obscuration effect generated by the disks surrounding these stars, and propose that different accretion mechanisms could operate in different objects, depending on their F(HeI5876) - V behaviour.

  18. Absolute Properties of the Main-Sequence Eclipsing Binary Star GX Geminorum: Constraints on Convective Core Overshooting

    NASA Astrophysics Data System (ADS)

    Lacy, Claud H. Sandberg; Torres, Guillermo; Claret, Antonio

    2008-05-01

    We present 12,155 new differential photometric observations in the V filter made with the Undergraduate Research Studies in Astronomy and NF\\Observatory WebScopes, as well as 33 radial velocities from spectroscopic observations of the detached, 4.04 day double-lined eclipsing binary star GX Gem. Absolute dimensions of the components are determined from these new, and also from previously published, data with high precision (less than 0.7% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 1.488 ± 0.011 solar masses and 2.327 ± 0.012 solar radii for the primary, and 1.467 ± 0.010 solar masses and 2.238 ± 0.012 solar radii for the secondary. The effective temperatures and interstellar reddening of the stars are accurately determined from the spectra, uvbyβ, and UBV photometry: 6195 ± 100 K for the primary, 6165 ± 100 K for the secondary, corresponding to spectral types of F7 and F7 V, and 0.068 mag for the color excess Eb - y . Spectral line widths give rotational velocities that are synchronous with the mean orbital motion in a circular orbit. The components of GX Gem are relatively old main-sequence stars with an age of about 2.8 billion years according to models. Because the components are located right at the end of their main-sequence evolutionary paths, we can place good limits on the convective core overshooting parameter. The lowest value of αov consistent with the observations would appear to be approximately αov = 0.18. Two different theories of tidal synchronization and circularization agree that the components should be synchronously rotating, but disagree about whether or not the orbits should be circular.

  19. POST-MAIN SEQUENCE EVOLUTION OF ICY MINOR PLANETS: IMPLICATIONS FOR WATER RETENTION AND WHITE DWARF POLLUTION

    SciTech Connect

    Malamud, Uri; Perets, Hagai B., E-mail: uri.mal@tx.technion.ac.il, E-mail: hperets@physics.technion.ac.il

    2016-12-01

    Most observations of polluted white dwarf atmospheres are consistent with accretion of water-depleted planetary material. Among tens of known cases, merely two involve accretion of objects that contain a considerable mass fraction of water. The purpose of this study is to investigate the relative scarcity of these detections. Based on a new and highly detailed model, we evaluate the retention of water inside icy minor planets during the high-luminosity stellar evolution that follows the main sequence. Our model fully considers the thermal, physical, and chemical evolution of icy bodies, following their internal differentiation as well as water depletion, from themore » moment of their birth and through all stellar evolution phases preceding the formation of the white dwarf. We also account for different initial compositions and formation times. Our results differ from previous studies, which have either underestimated or overestimated water retention. We show that water can survive in a variety of circumstances and in great quantities, and therefore other possibilities are discussed in order to explain the infrequency of water detection. We predict that the sequence of accretion is such that water accretes earlier, and more rapidly, than the rest of the silicate disk, considerably reducing the chance of its detection in H-dominated atmospheres. In He-dominated atmospheres, the scarcity of water detections could be observationally biased. It implies that the accreted material is typically intrinsically dry, which may be the result of the inside-out depopulation sequence of minor planets.« less

  20. Discovery of Extended Main-sequence Turnoffs in Four Young Massive Clusters in the Magellanic Clouds

    SciTech Connect

    Li, Chengyuan; De Grijs, Richard; Deng, Licai

    2017-08-01

    An increasing number of young massive clusters (YMCs) in the Magellanic Clouds have been found to exhibit bimodal or extended main sequences (MSs) in their color–magnitude diagrams (CMDs). These features are usually interpreted in terms of a coeval stellar population with different stellar rotational rates, where the blue and red MS stars are populated by non- (or slowly) and rapidly rotating stellar populations, respectively. However, some studies have shown that an age spread of several million years is required to reproduce the observed wide turnoff regions in some YMCs. Here we present the ultraviolet–visual CMDs of four Large and Smallmore » Magellanic Cloud YMCs, NGC 330, NGC 1805, NGC 1818, and NGC 2164, based on high-precision Hubble Space Telescope photometry. We show that they all exhibit extended main-sequence turnoffs (MSTOs). The importance of age spreads and stellar rotation in reproducing the observations is investigated. The observed extended MSTOs cannot be explained by stellar rotation alone. Adopting an age spread of 35–50 Myr can alleviate this difficulty. We conclude that stars in these clusters are characterized by ranges in both their ages and rotation properties, but the origin of the age spread in these clusters remains unknown.« less

  1. X-ray sources in regions of star formation. II - The pre-main-sequence G star HDE 283572

    NASA Technical Reports Server (NTRS)

    Walter, F. M.; Brown, A.; Linsky, J. L.; Rydgren, A. E.; Vrba, F.

    1987-01-01

    This paper reports the detection of HDE 283572, a ninth-magnitude G star 8 arcmin south of RY Tau, as a bright X-ray source. The observations reveal this object to be a fairly massive (about 2 solar masses) pre-main-sequence star associated with the Taurus-Auriga star formation complex. It exhibits few of the characteristics of the classical T Tauri stars and is a good example of a 'naked' T Tauri star. The star is a mid-G subgiant, of about three solar radii and rotates with a period of 1.5 d. The coronal and chromospheric surface fluxes are similar to those of the most active late type stars (excluding T Tauri stars). The X-ray and UV lines most likely arise in different atmospheric structures. Radiative losses are some 1000 times the quiet solar value and compare favorably with those of T Tauri stars.

  2. ASCA X-ray observations of pre-main-sequence stars

    NASA Technical Reports Server (NTRS)

    Skinner, S. L.; Walter, F. M.; Yamauchi, S.

    1996-01-01

    The results of recent Advanced Satellite for Cosmology and Astrophysics (ASCA) X-ray observations of two pre-main sequence stars are presented: the weak emission line T Tauri star HD 142361, and the Herbig Ae star HD 104237. The solid state imaging spectrometer spectra for HD 142361 shows a clear emission line from H-like Mg 7, and spectral fits reveal a multiple temperature plasma with a hot component of at least 16 MK. The spectra of HD 104237 show a complex temperature structure with the hottest plasma at temperatures of greater than 30 MK. It is concluded that mechanisms that predict only soft X-ray emission can be dismissed for Herbig Ae stars.

  3. Stellar vs. Solar Activity: The Case of Pre-main Sequence Stars

    NASA Astrophysics Data System (ADS)

    Montmerle, Th.

    X-rays have proved a powerful tool in discovering, or monitoring, the activity of any kinds of stars. Among these, the T Tauri stars and other pre-main sequence objects are particularly interesting in that, based on X-rays, the activity seems to be of solar type. Also, in the radio range, follow-up observation have allowed to discover a few flaring PMS stars. Optical results have recently confirmed the solar nature of this activity. However, in the microwave range, exotic phenomena like jets or bipolar flows appear to be widespread. In the radio cm range, the emission is non-solar in most cases. The reasons for this may lie in the specific nature of PMS objects, i.e., very young and perhaps still surrounded by circumstellar material (e.g., accretion disks), drawn from their parent molecular cloud.

  4. New radio detections of early-type pre-main-sequence stars

    NASA Technical Reports Server (NTRS)

    Skinner, Stephen L.; Brown, Alexander; Linsky, Jeffrey L.

    1990-01-01

    Results of VLA radio continuum observations of 13 early-type pre-main-sequence stars selected from the 1984 catalog of Finkenzeller and Mundt are presented. The stars HD 259431 and MWC 1080 were detected at 3.6 cm, while HD 200775 and TY CrA were detected at both 3.6 and 6 cm. The flux density of HD 200775 has a frequency dependence consistent with the behavior expected for free-free emission originating in a fully ionized wind. However, an observation in A configuration suggests that the source geometry may not be spherically symmetric. In contrast, the spectral index of TY CrA is negative with a flux behavior implying nonthermal emission. The physical mechanism responsible for the nonthermal emission has not yet been identified, although gyrosynchrotron and synchrotron processes cannot be ruled out.

  5. A surprise at the bottom of the main sequence: Rapid rotation and NO H-alpha emission

    NASA Technical Reports Server (NTRS)

    Basri, Gibor; Marcy, Geoffrey W.

    1995-01-01

    We report Kech Observatory high-resolution echelle spectra from 640-850 nm for eight stars near the faint end of the main sequence. These spectra are the highest resolution spectra of such late-type stars, and clearly resolve the TiO, VO, and atomic lines. The sample includes the field brown-dwarf candidate, BRI 0021-0214 (M9.5+). Very unexpectedly, it shows the most rapid rotation in the entire samples, v sin i approximately 40 km/s, which is 20x faster than typical field nonemission M stars. Equally surprising is that BRI 0021 exhibits no emission or absorptionat H-alpha. We argue that this absence is not simply due to its cool photosphere, but that stellar activity declines in a fundamental way at the end of the main sequence. As it is the first very late M dwarf observed at high spectral resolution, BRI 0021 may be signaling a qualitative change in the angular momentum loss rate among the lowest mass stars. Conventionally, its rapid rotation would have marked BRI 0021 as very young, consistent with the selection effect which arises if the latest-type dwarfs are really brown dwarfs on cooling curves. In any case, it is unprecedented to find no sign of stellar activity in such a rapidly rotating convective star. We also discuss the possible conflict between this observation and the extremely strong H-alpha seen in another very cool star, PC 0025+0447. Extrapolation of M-L relations for BRI 0021 yields M approximately 0.065 solar mass, and the other sample objects have expected masses near the H-burning limit. These include two Pleiades brown-dwarf candidates, four field M6 dwarfs and one late-type T Tauri star. The two Pleiades M6 dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radial velocities consistent with Pleiades M6 dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radial velocities consistent with Pleiades membership. Similarly, the late-type T Tauri star has v sin i approximately 30 km/s and H alpha emission indicate of its

  6. The slowly pulsating B-star 18 Pegasi: A testbed for upper main sequence stellar evolution

    NASA Astrophysics Data System (ADS)

    Irrgang, A.; Desphande, A.; Moehler, S.; Mugrauer, M.; Janousch, D.

    2016-06-01

    The predicted width of the upper main sequence in stellar evolution models depends on the empirical calibration of the convective overshooting parameter. Despite decades of discussions, its precise value is still unknown and further observational constraints are required to gauge it. Based on a photometric and preliminary asteroseismic analysis, we show that the mid B-type giant 18 Peg is one of the most evolved members of the rare class of slowly pulsating B-stars and, thus, bears tremendous potential to derive a tight lower limit for the width of the upper main sequence. In addition, 18 Peg turns out to be part of a single-lined spectroscopic binary system with an eccentric orbit that is greater than 6 years. Further spectroscopic and photometric monitoring and a sophisticated asteroseismic investigation are required to exploit the full potential of this star as a benchmark object for stellar evolution theory. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 265.C-5038(A), 069.C-0263(A), and 073.D-0024(A). Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC), proposals H2005-2.2-016 and H2015-3.5-008. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, proposal W15BN015. Based on observations obtained with telescopes of the University Observatory Jena, which is operated by the Astrophysical Institute of the Friedrich-Schiller-University.

  7. LESSONS IN DE NOVO PEPTIDE SEQUENCING BY TANDEM MASS SPECTROMETRY

    PubMed Central

    Medzihradszky, Katalin F.; Chalkley, Robert J.

    2015-01-01

    Mass spectrometry has become the method of choice for the qualitative and quantitative characterization of protein mixtures isolated from all kinds of living organisms. The raw data in these studies are MS/MS spectra, usually of peptides produced by proteolytic digestion of a protein. These spectra are “translated” into peptide sequences, normally with the help of various search engines. Data acquisition and interpretation have both been automated, and most researchers look only at the summary of the identifications without ever viewing the underlying raw data used for assignments. Automated analysis of data is essential due to the volume produced. However, being familiar with the finer intricacies of peptide fragmentation processes, and experiencing the difficulties of manual data interpretation allow a researcher to be able to more critically evaluate key results, particularly because there are many known rules of peptide fragmentation that are not incorporated into search engine scoring. Since the most commonly used MS/MS activation method is collision-induced dissociation (CID), in this article we present a brief review of the history of peptide CID analysis. Next, we provide a detailed tutorial on how to determine peptide sequences from CID data. Although the focus of the tutorial is de novo sequencing, the lessons learned and resources supplied are useful for data interpretation in general. PMID:25667941

  8. Return to [Log-]Normalcy: Rethinking Quenching, The Star Formation Main Sequence, and Perhaps Much More

    NASA Astrophysics Data System (ADS)

    Abramson, Louis E.; Gladders, Michael D.; Dressler, Alan; Oemler, Augustus, Jr.; Poggianti, Bianca; Vulcani, Benedetta

    2016-11-01

    Knowledge of galaxy evolution rests on cross-sectional observations of different objects at different times. Understanding of galaxy evolution rests on longitudinal interpretations of how these data relate to individual objects moving through time. The connection between the two is often assumed to be clear, but we use a simple “physics-free” model to show that it is not and that exploring its nuances can yield new insights. Comprising nothing more than 2094 loosely constrained lognormal star formation histories (SFHs), the model faithfully reproduces the following data it was not designed to match: stellar mass functions at z≤slant 8; the slope of the star formation rate/stellar mass relation (the SFR “Main Sequence”) at z≤slant 6; the mean {sSFR}(\\equiv {SFR}/{M}* ) of low-mass galaxies at z≤slant 7; “fast-” and “slow-track” quenching; downsizing; and a correlation between formation timescale and {sSFR}({M}* ,t) similar to results from simulations that provides a natural connection to bulge growth. We take these findings—which suggest that quenching is the natural downturn of all SFHs affecting galaxies at rates/times correlated with their densities—to mean that: (1) models in which galaxies are diversified on Hubble timescales by something like initial conditions rival the dominant grow-and-quench framework as good descriptions of the data; or (2) absent spatial information, many metrics of galaxy evolution are too undiscriminating—if not inherently misleading—to confirm a unique explanation. We outline future tests of our model but stress that, even if ultimately incorrect, it illustrates how exploring different paradigms can aid learning and, we hope, more detailed modeling efforts.

  9. Extended main sequence turnoffs in intermediate-age star clusters: a correlation between turnoff width and early escape velocity

    SciTech Connect

    Goudfrooij, Paul; Kozhurina-Platais, Vera; Kalirai, Jason S.

    2014-12-10

    We present a color-magnitude diagram analysis of deep Hubble Space Telescope imaging of a mass-limited sample of 18 intermediate-age (1-2 Gyr old) star clusters in the Magellanic Clouds, including eight clusters for which new data were obtained. We find that all star clusters in our sample feature extended main-sequence turnoff (eMSTO) regions that are wider than can be accounted for by a simple stellar population (including unresolved binary stars). FWHM widths of the MSTOs indicate age spreads of 200-550 Myr. We evaluate the dynamical evolution of clusters with and without initial mass segregation. Our main results are (1) the fractionmore » of red clump (RC) stars in secondary RCs in eMSTO clusters scales with the fraction of MSTO stars having pseudo-ages of ≲1.35 Gyr; (2) the width of the pseudo-age distributions of eMSTO clusters is correlated with their central escape velocity v {sub esc}, both currently and at an age of 10 Myr. We find that these two results are unlikely to be reproduced by the effects of interactive binary stars or a range of stellar rotation velocities. We therefore argue that the eMSTO phenomenon is mainly caused by extended star formation within the clusters; and (3) we find that v {sub esc} ≥ 15 km s{sup –1} out to ages of at least 100 Myr for all clusters featuring eMSTOs, and v {sub esc} ≤ 12 km s{sup –1} at all ages for two lower-mass clusters in the same age range that do not show eMSTOs. We argue that eMSTOs only occur for clusters whose early escape velocities are higher than the wind velocities of stars that provide material from which second-generation stars can form. The threshold of 12-15 km s{sup –1} is consistent with wind velocities of intermediate-mass asymptotic giant branch stars and massive binary stars in the literature.« less

  10. Delayed gratification habitable zones: when deep outer solar system regions become balmy during post-main sequence stellar evolution.

    PubMed

    Stern, S Alan

    2003-01-01

    Like all low- and moderate-mass stars, the Sun will burn as a red giant during its later evolution, generating of solar luminosities for some tens of millions of years. During this post-main sequence phase, the habitable (i.e., liquid water) thermal zone of our Solar System will lie in the region where Triton, Pluto-Charon, and Kuiper Belt objects orbit. Compared with the 1 AU habitable zone where Earth resides, this "delayed gratification habitable zone" (DGHZ) will enjoy a far less biologically hazardous environment - with lower harmful radiation levels from the Sun, and a far less destructive collisional environment. Objects like Triton, Pluto-Charon, and Kuiper Belt objects, which are known to be rich in both water and organics, will then become possible sites for biochemical and perhaps even biological evolution. The Kuiper Belt, with >10(5) objects > or =50 km in radius and more than three times the combined surface area of the four terrestrial planets, provides numerous sites for possible evolution once the Sun's DGHZ reaches it. The Sun's DGHZ might be thought to only be of academic interest owing to its great separation from us in time. However, approximately 10(9) Milky Way stars burn as luminous red giants today. Thus, if icy-organic objects are common in the 20-50 AU zones of these stars, as they are in our Solar System (and as inferred in numerous main sequence stellar disk systems), then DGHZs may form a niche type of habitable zone that is likely to be numerically common in the Galaxy.

  11. The pre-main-sequence binary HK Ori: spectro-astrometry and EXPORT data

    NASA Astrophysics Data System (ADS)

    Baines, D.; Oudmaijer, R. D.; Mora, A.; Eiroa, C.; Porter, John M.; Merín, B.; Montesinos, B.; de Winter, D.; Collier Cameron, A.; Davies, J. K.; Deeg, H. J.; Ferlet, R.; Grady, C. A.; Harris, A. W.; Hoare, M. G.; Horne, K.; Lumsden, S. L.; Miranda, L. F.; Penny, A.; Quirrenbach, A.

    2004-09-01

    In this paper we present multi-epoch observations of the pre-main-sequence binary HK Ori. These data have been drawn from the EXPORT data base and are complemented by high-quality spectro-astrometric data of the system. The spectroscopic data appear to be very well represented by a combination of an A dwarf star spectrum superposed on a (sub)giant G-type spectrum. The radial velocity of the system is consistent with previous determinations, and does not reveal binary motion, as expected for a wide binary. The spectral, photometric and polarimetric properties and variability of the system indicate that the active object in the system is a T Tauri star with UX Ori characteristics. The spectro-astrometry of HK Ori is sensitive down to milliarcsecond scales and confirms the speckle interferometric results from Leinert et al. The spectro-astrometry allows the identification, with fair certainty, of the active star within the binary, which we suggest to be a G-type T Tauri star based on its spectral characteristics.

  12. THE EVOLVED MAIN-SEQUENCE CHANNEL: HST AND LBT OBSERVATIONS OF CSS 120422:111127+571239

    SciTech Connect

    Kennedy, M.; Callanan, P.; Garnavich, P.

    2015-12-20

    The “evolved main-sequence (EMS)” channel is thought to contribute significantly to the population of AM CVn-type systems in the Galaxy, and also to the number of cataclysmic variables (CVs) detected below the period minimum for hydrogen rich systems. CSS 120422:J111127+571239 was discovered by the Catalina Sky Survey in 2012 April. Its period was found to be 56 minutes, well below the minimum, and the optical spectrum is clearly depleted in hydrogen relative to helium, but still has two orders of magnitude more hydrogen than AM CVn stars. Doppler tomography of the Hα line hinted at a spiral structure existing inmore » the disk. Here we present spectroscopy of CSS 120422:J111127+571239 using the Cosmic Origins Spectrograph FUV instrument on the Hubble Space Telescope and using the MODS spectrograph on the Large Binocular Telescope. The UV spectrum shows Si iv, N v, and He ii, but no detectable C iv. The anomalous nitrogen/carbon ratio is seen in a small number of other CVs and confirms a unique binary evolution. We also present and compare the optical spectrum of V418 Ser and advocate that it is also an EMS system.« less

  13. Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

    NASA Technical Reports Server (NTRS)

    Feigelson, Eric D.; Kriss, Gerard A.

    1987-01-01

    Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

  14. Detailed Iron-Group Abundances in a Very Metal-Poor Main Sequence Turnoff Star

    NASA Astrophysics Data System (ADS)

    Sneden, Chris; Roederer, Ian U.; Boesgaard, Ann M.; Lawler, James E.; Den Hartog, Elizabeth; Cowan, John J.; Sobeck, Jennifer

    2017-01-01

    We have obtained Keck HIRES and HST STIS high resolution, high signal-to-noise spectra of the very metal-poor ([Fe/H] ~ -2.9) main-sequence turnoff star BD+03 740. A detailed chemical composition analysis based on synthetic spectrum computations has been conducted. Our initial focus has been on the iron-group elements in the Z = 21-28 range. This study takes advantage of recent improvements in neutral and ionzied species transition data for all of these elements except Sc (Z = 21) by the Wisconsin atomic physics group (see a companion presentation on Cr II at this meeting). Several metal-poor abundance surveys have concluded that there are large overabundances of Co and underabundances of Cr with respect to Fe for stars with [Fe/H] < -2.5. Neither of these anomalies is seen in BD+03 740. We discuss the implications of this result for early iron-group synthesis in the Galaxy.This work has been supported by HST STScI Program GO-14232; and NSF grants AST-1211585 and AST-1616040 to CS; AST-1516182 to JEL and EDH; NASA grant NNX16AE96G to JEL

  15. MAGNETIC ACTIVITY ANALYSIS FOR A SAMPLE OF G-TYPE MAIN SEQUENCE KEPLER TARGETS

    SciTech Connect

    Mehrabi, Ahmad; He, Han; Khosroshahi, Habib, E-mail: mehrabi@basu.ac.ir

    2017-01-10

    The variation of a stellar light curve owing to rotational modulation by magnetic features (starspots and faculae) on the star’s surface can be used to investigate the magnetic properties of the host star. In this paper, we use the periodicity and magnitude of the light-curve variation as two proxies to study the stellar magnetic properties for a large sample of G-type main sequence Kepler targets, for which the rotation periods were recently determined. By analyzing the correlation between the two magnetic proxies, it is found that: (1) the two proxies are positively correlated for most of the stars in ourmore » sample, and the percentages of negative, zero, and positive correlations are 4.27%, 6.81%, and 88.91%, respectively; (2) negative correlation stars cannot have a large magnitude of light-curve variation; and (3) with the increase of rotation period, the relative number of positive correlation stars decreases and the negative correlation one increases. These results indicate that stars with shorter rotation period tend to have positive correlation between the two proxies, and a good portion of the positive correlation stars have a larger magnitude of light-curve variation (and hence more intense magnetic activities) than negative correlation stars.« less

  16. Evolution of Orbit and Rotation of a Pseudo-Synchronous Binary System on the Main Sequence

    NASA Astrophysics Data System (ADS)

    Li, Lin-Sen

    2018-02-01

    We study pseudo-synchronous orbital motion has been studied for the binary system on the main sequence. The equations of the pseudo-synchronous orbit are derived up to O(e^4) where e is the eccentricy of the orbit. We integrate the equations to present their solutions. The theoretical results are applied to the evolution of the orbit and spin of binary star Y Cygni, which has the current eccentricity of e_0=0.142. We tabulate our numerical results for the evolution of the orbit and spin per century. The numerical results for the semi-major axes and rotational angular velocities in the evolutional time scales of three stages (synchronization, circularization and collapse time scale) are also tabulated, where synchronization is achieved in about 5× 10^3 years followed by circularization lasting about 1× 10^5 years before decaying in 2× 10^5 years. Some conclusions are inferred from the results obtained.

  17. Phylogenetic reconstruction of Bantu kinship challenges Main Sequence Theory of human social evolution.

    PubMed

    Opie, Christopher; Shultz, Susanne; Atkinson, Quentin D; Currie, Thomas; Mace, Ruth

    2014-12-09

    Kinship provides the fundamental structure of human society: descent determines the inheritance pattern between generations, whereas residence rules govern the location a couple moves to after they marry. In turn, descent and residence patterns determine other key relationships such as alliance, trade, and marriage partners. Hunter-gatherer kinship patterns are viewed as flexible, whereas agricultural societies are thought to have developed much more stable kinship patterns as they expanded during the Holocene. Among the Bantu farmers of sub-Saharan Africa, the ancestral kinship patterns present at the beginning of the expansion are hotly contested, with some arguing for matrilineal and matrilocal patterns, whereas others maintain that any kind of lineality or sex-biased dispersal only emerged much later. Here, we use Bayesian phylogenetic methods to uncover the history of Bantu kinship patterns and trace the interplay between descent and residence systems. The results suggest a number of switches in both descent and residence patterns as Bantu farming spread, but that the first Bantu populations were patrilocal with patrilineal descent. Across the phylogeny, a change in descent triggered a switch away from patrifocal kinship, whereas a change in residence triggered a switch back from matrifocal kinship. These results challenge "Main Sequence Theory," which maintains that changes in residence rules precede change in other social structures. We also indicate the trajectory of kinship change, shedding new light on how this fundamental structure of society developed as farming spread across the globe during the Neolithic.

  18. A search for pre-main sequence stars in the high-latitude molecular clouds. II - A survey of the Einstein database

    NASA Technical Reports Server (NTRS)

    Caillault, Jean-Pierre; Magnani, Loris

    1990-01-01

    The preliminary results are reported of a survey of every EINSTEIN image which overlaps any high-latitude molecular cloud in a search for X-ray emitting pre-main sequence stars. This survey, together with complementary KPNO and IRAS data, will allow the determination of how prevalent low mass star formation is in these clouds in general and, particularly, in the translucent molecular clouds.

  19. Gaia-ESO Survey: Analysis of pre-main sequence stellar spectra

    NASA Astrophysics Data System (ADS)

    Lanzafame, A. C.; Frasca, A.; Damiani, F.; Franciosini, E.; Cottaar, M.; Sousa, S. G.; Tabernero, H. M.; Klutsch, A.; Spina, L.; Biazzo, K.; Prisinzano, L.; Sacco, G. G.; Randich, S.; Brugaletta, E.; Delgado Mena, E.; Adibekyan, V.; Montes, D.; Bonito, R.; Gameiro, J. F.; Alcalá, J. M.; González Hernández, J. I.; Jeffries, R.; Messina, S.; Meyer, M.; Gilmore, G.; Asplund, M.; Binney, J.; Bonifacio, P.; Drew, J. E.; Feltzing, S.; Ferguson, A. M. N.; Micela, G.; Negueruela, I.; Prusti, T.; Rix, H.-W.; Vallenari, A.; Alfaro, E. J.; Allende Prieto, C.; Babusiaux, C.; Bensby, T.; Blomme, R.; Bragaglia, A.; Flaccomio, E.; Francois, P.; Hambly, N.; Irwin, M.; Koposov, S. E.; Korn, A. J.; Smiljanic, R.; Van Eck, S.; Walton, N.; Bayo, A.; Bergemann, M.; Carraro, G.; Costado, M. T.; Edvardsson, B.; Heiter, U.; Hill, V.; Hourihane, A.; Jackson, R. J.; Jofré, P.; Lardo, C.; Lewis, J.; Lind, K.; Magrini, L.; Marconi, G.; Martayan, C.; Masseron, T.; Monaco, L.; Morbidelli, L.; Sbordone, L.; Worley, C. C.; Zaggia, S.

    2015-04-01

    Context. The Gaia-ESO Public Spectroscopic Survey is obtaining high-quality spectroscopy of some 100 000 Milky Way stars using the FLAMES spectrograph at the VLT, down to V = 19 mag, systematically covering all the main components of the Milky Way and providing the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. Observations of young open clusters, in particular, are giving new insights into their initial structure, kinematics, and their subsequent evolution. Aims: This paper describes the analysis of UVES and GIRAFFE spectra acquired in the fields of young clusters whose population includes pre-main sequence (PMS) stars. The analysis is applied to all stars in such fields, regardless of any prior information on membership, and provides fundamental stellar atmospheric parameters, elemental abundances, and PMS-specific parameters such as veiling, accretion, and chromospheric activity. Methods: When feasible, different methods were used to derive raw parameters (e.g. line equivalent widths) fundamental atmospheric parameters and derived parameters (e.g. abundances). To derive some of these parameters, we used methods that have been extensively used in the past and new ones developed in the context of the Gaia-ESO survey enterprise. The internal precision of these quantities was estimated by inter-comparing the results obtained by these different methods, while the accuracy was estimated by comparison with independent external data, such as effective temperature and surface gravity derived from angular diameter measurements, on a sample of benchmarks stars. A validation procedure based on these comparisons was applied to discard spurious or doubtful results and produce recommended parameters. Specific strategies were implemented to resolve problems of fast rotation, accretion signatures, chromospheric activity, and veiling. Results: The analysis carried out on spectra acquired in young cluster fields during

  20. On the simultaneous optical and near-infrared variability of pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Eiroa, C.; Oudmaijer, R. D.; Davies, J. K.; de Winter, D.; Garzón, F.; Palacios, J.; Alberdi, A.; Ferlet, R.; Grady, C. A.; Collier Cameron, A.; Deeg, H. J.; Harris, A. W.; Horne, K.; Merín, B.; Miranda, L. F.; Montesinos, B.; Mora, A.; Penny, A.; Quirrenbach, A.; Rauer, H.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.

    2002-03-01

    For a complete understanding of the physical processes causing the photometric variability of pre-main sequence systems, simultaneous optical and near-IR observations are required to disentangle the emission from the stars and that from their associated circumstellar disks. Data of this sort are extremely rare and little systematic work has been reported to date. The work presented in this paper is a systematic attempt in this direction. It presents an analysis of the simultaneous optical and near-IR photometric variability of 18 Herbig Ae/Be and T Tauri stars which were observed in October 98 by the EXPORT collaboration. The time difference between the UBVRI and JHK measurements is less than 1 hour in ~50% of the data and the largest difference is around 2 hours in only ~10% of the data. Twelve stars appear to show a correlation between the optical and near-IR variability trends, which suggests a common physical origin such as spots and/or variable extinction. The optical and near-IR variability is uncorrelated in the rest of the objects, which suggests it originates in distinctly different regions. In general, the optical variability qualitatively follows the predictions of starspots or variable extinction. As far as the near-IR is concerned, the simultaneity of the observations demonstrates that for most objects the flux is largely produced by their circumstellar disks and, consequently, in many cases the near-IR fluctuations must be attributed to structural variations of such disks producing variations of their thermal emission and/or scattered light. The observed near-IR changes of up to around 1 mag on timescales of 1-2 days provide interesting challenges for understanding the mechanisms generating such remarkable variabilities, an issue insufficiently investigated until now but one which deserves further theoretical and modeling efforts.

  1. Time Variability of the Dust Sublimation Zones in Pre-Main Sequence Disk Systems

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Carpenter, W. J.; Grady, C. A.; Russel, R. W.; Lynch, D. K.; Rudy, R. J.; Mazuk, S. M.; Venturini, C. C.; Kimes, R. L.; Beerman, L. C.; hide

    2007-01-01

    The dust sublimation zone (DSZ) is the region of pre-main sequence (PMS) disks where dust grains most easily anneal, sublime, and condense out of the gas. Because of this, it is a location where crystalline material may be enhanced and redistributed throughout the rest of the disk. A decade-long program to monitor the thermal emission of the grains located in this region demonstrates that large changes in emitted flux occur in many systems. Changes in the thermal emission between 3 and 13.5 microns were observed in HD 31648 (MWC 480), HD 163296 (MWC 275), and DG Tau. This emission is consistent with it being produced at the DSZ, where the transition from a disk of gas to one of gas+dust occurs. In the case of DG Tau, the outbursts were accompanied by increased emission on the 10 micron silicate band on one occasion, while on another occasion it went into absorption. This requires lofting of the material above the disk into the line of sight. Such changes will affect the determination of the inner disk structure obtained through interferometry measurements, and this has been confirmed in the case of HD 163296. Cyclic variations in the heating of the DSZ will lead to the annealing of large grains, the sublimation of smaller grains, possibly followed by re-condensation as the zone enters a cooling phase. Lofting of dust above the disk plane, and outward acceleration by stellar winds and radiation pressure, can re-distribute the processed material to cooler regions of the disk, where cometesimals form. This processing is consistent with the detection of the preferential concentration of large crystalline grains in the inner few AU of PMS disks using interferometric spectroscopy with the VLTI.

  2. Mid-IR observations of circumstellar disks. I. Pre-main sequence objects

    NASA Astrophysics Data System (ADS)

    Schütz, O.; Meeus, G.; Sterzik, M. F.

    2005-02-01

    We present new N-band photometry and spectroscopy for a sample of eight pre-main sequence stars including T Tauri, Herbig Ae/Be stars and FU Ori objects using the ESO TIMMI2 camera at the La Silla observatory (Chile). For some objects this is their first N-band spectroscopic observation ever. The FU Ori stars V 346 Nor, V 883 Ori and Z CMa show a broad absorption band which we attribute to silicates, while for BBW 76 we find silicate emission. A comparison with ISO-SWS spectra of V 346 Nor and Z CMa taken in 1996/1997 reveals no differences in spectral shape. All T Tauri and Herbig Ae/Be stars possess N-band emission features. We model the emission spectra with a mixture of silicates consisting of different grain sizes and composition. The Herbig Ae star HD 34282 shows strong features of PAHs but none of silicate, while the emission spectrum of the Herbig Ae star HD 72106 resembles those of solar-system comets and known Herbig sources of evolved dust. We demonstrate that HD 72106 is host to highly processed silicates and find evidence for enstatite, which is not common in young objects. Evolved dust is also seen in the T Tauri stars HD 98800 and MP Mus. We further detected MP Mus at 1200 μm with the bolometer array SIMBA at the SEST in La Silla. The findings of our analysis are given in the context of previous dust studies of young stellar objects. Based on observations collected at the European Southern Observatory, La Silla, Chile (69.C-0073, 70.C-0468, 71.C-0001, 73.C-0372).

  3. Linear Relation for Wind-blown Bubble Sizes of Main-sequence OB Stars in a Molecular Environment and Implication for Supernova Progenitors

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Zhou, Ping; Chu, You-Hua

    2013-05-01

    We find a linear relationship between the size of a massive star's main-sequence bubble in a molecular environment and the star's initial mass: R b ≈ 1.22 M/M ⊙ - 9.16 pc, assuming a constant interclump pressure. Since stars in the mass range of 8 to 25-30 M ⊙ will end their evolution in the red supergiant phase without launching a Wolf-Rayet wind, the main-sequence wind-blown bubbles are mainly responsible for the extent of molecular gas cavities, while the effect of the photoionization is comparatively small. This linear relation can thus be used to infer the masses of the massive star progenitors of supernova remnants (SNRs) that are discovered to evolve in molecular cavities, while few other means are available for inferring the properties of SNR progenitors. We have used this method to estimate the initial masses of the progenitors of eight SNRs: Kes 69, Kes 75, Kes 78, 3C 396, 3C 397, HC 40, Vela, and RX J1713-3946.

  4. The environmental impacts on the star formation main sequence: An Hα study of the newly discovered rich cluster at z = 1.52

    SciTech Connect

    Koyama, Yusei; Kodama, Tadayuki; Tadaki, Ken-ichi

    2014-07-01

    We report the discovery of a strong over-density of galaxies in the field of a radio galaxy at z = 1.52 (4C 65.22) based on our broadband and narrow-band (Hα) photometry with the Subaru Telescope. We find that Hα emitters are located in the outskirts of the density peak (cluster core) dominated by passive red-sequence galaxies. This resembles the situation in lower-redshift clusters, suggesting that the newly discovered structure is a well-evolved rich galaxy cluster at z = 1.5. Our data suggest that the color-density and stellar mass-density relations are already in place at z ∼ 1.5, mostly driven bymore » the passive red massive galaxies residing within r{sub c} ≲ 200 kpc from the cluster core. These environmental trends almost disappear when we consider only star-forming (SF) galaxies. We do not find SFR-density or SSFR-density relations amongst SF galaxies, and the location of the SF main sequence does not significantly change with environment. Nevertheless, we find a tentative hint that star-bursting galaxies (up-scattered objects from the main sequence) are preferentially located in a small group at ∼1 Mpc away from the main body of the cluster. We also argue that the scatter of the SF main sequence could be dependent on the distance to the nearest neighboring galaxy.« less

  5. Evidence for a Significant Intermediate-Age Population in the M31 Halo from Main Sequence Photometry

    NASA Technical Reports Server (NTRS)

    Brown, Thomas M.; Ferguson, Henry C.; Smith, Ed; Kimble, Randy A.; Sweigart, Allen V.; Renzini, Alvio; Rich, R. Michael; Vandenberg, Don A.

    2003-01-01

    We present a color-magnitude diagram (CMD) for a minor-axis field in the halo of the Andromeda galaxy (M3l), 51 arcmin (11 kpc) from the nucleus. These observations, taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope, are the deepest optical images yet obtained, attaining 50% completeness at m(sub v) = 30.7 mag. The CMD, constructed from approx. 3 x 10(exp 5) stars, reaches more than 1.5 mag fainter than the old main-sequence turnoff. Our analysis is based on direct comparisons to ACS observations of four globular clusters through the same filters, as well as chi square fitting to a finely-spaced grid of calibrated stellar-population models. We find that the M31 halo contains a major (approx. 30% by mass) intermediate-age (6-8 Gyr) metal-rich ([Fe/H] greater than -0.5) population, as well as a significant globular-cluster age (11-13.5 Gyr) metal-poor population. These findings support the idea that galaxy mergers played an important role in the formation of the M31 halo.

  6. Rotation-induced YORP break-up of small bodies to produce post-main-sequence debris

    NASA Astrophysics Data System (ADS)

    Veras, D.; Jacobson, S. A.; Gänsicke, B. T.

    2017-09-01

    We hypothesize that the in situ break-up of small bodies such as asteroids spun to fission during the giant branch phases of stellar evolution provides an important contribution to the debris orbiting and ultimately polluting white dwarfs. The YORP (Yarkovsky-O'Keefe-Radviesvki-Paddock) effect, which arises from radiation pressure, accelerates the spin rate of asymmetric asteroids, which can eventually shear themselves apart. This pressure is maintained and enhanced around dying stars because the outward push of an asteroid due to stellar mass loss is insignificant compared to the resulting stellar luminosity increase. Consequently, giant star radiation will destroy nearly all bodies with radii in the range 100 m-10 km that survive their parent star's main-sequence lifetime within a distance of about 7 au; smaller bodies are spun apart to their strongest, competent components. This estimate is conservative and would increase for highly asymmetric shapes or incorporation of the inward drag due to giant star stellar wind. The resulting debris field, which could extend to thousands of au, may be perturbed by remnant planetary systems to reproduce the observed dusty and gaseous discs which accompany polluted white dwarfs.

  7. The PTF Open Cluster Survey: Tracking the Evolution of Rotation and Activity on the Lower Main Sequence

    NASA Astrophysics Data System (ADS)

    Agueros, Marcel A.; Bochanski, J. J.; Bowsher, E. C.; Cargile, P.; Covey, K. R.; Kraus, A. L.; Kundert, A.; Law, N. M.; PTF Collaboration

    2013-01-01

    A star's age is one of its most fundamental parameters. It is also, for isolated field stars, notoriously difficult to measure. Skumanich (1972) first proposed the existence of a relation between a star's age, rotation, and magnetic activity, but in the intervening 40 years, observational limitations have hampered the assembly of complete and uniform samples of rotation and activity measurements for stars spanning a wide range of ages and masses. We are still far from being able to describe fully the evolution of either rotation or activity for stars of a given mass, or from being able to use rotation or activity measurements to determine precisely the ages of isolated field stars. Fortunately, recent advances have transformed our ability to characterize open clusters, which provide the optimal environment for obtaining robust age estimates for individual stars. Robotic surveys such as the Palomar Transient Factory (PTF) now enable high cadence, long baseline monitoring of large-angular-sized clusters. And multi-object spectrographs and sensitive X-ray detectors make it possible to extend activity measurements to fainter stars in distant, older, and more populous clusters. Here we present recent results from our efforts to assemble a complete, uniform sample of rotation and activity measurements for sub-solar stars in six open clusters ranging in age from 35 Myr to 2.5 Gyr (Alpha Per, the Pleiades, Praesepe, M37, NGC 752, and Ruprecht 147). This sample will be used to derive a description of the age-rotation-activity relation for sub-solar stars from their arrival on the zero-age main-sequence to when they are a significant fraction of the age of the Sun.

  8. KEPLER-4b: A HOT NEPTUNE-LIKE PLANET OF A G0 STAR NEAR MAIN-SEQUENCE TURNOFF

    SciTech Connect

    Borucki, William J.; Koch, David G.; Caldwell, Douglas A.

    2010-04-20

    Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19{sup h}02{sup m}27.{sup s}68, {delta} = +50{sup 0}08'08.''7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10{sup -3} and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3{sup +1.1} {sub -1.9} m s{sup -1}, consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companionmore » star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223{sup +0.053} {sub -0.091} M {sub sun} and 1.487{sup +0.071} {sub -0.084} R {sub sun}. We estimate the planet mass and radius to be {l_brace}M {sub P}, R {sub P}{r_brace} = {l_brace}24.5 {+-} 3.8 M {sub +}, 3.99 {+-} 0.21 R {sub +}{r_brace}. The planet's density is near 1.9 g cm{sup -3}; it is thus slightly denser and more massive than Neptune, but about the same size.« less

  9. An Observational Study of Accretion Dynamics in Short-Period Pre-Main Sequence Binaries

    NASA Astrophysics Data System (ADS)

    Tofflemire, Benjamin; Mathieu, Robert; Herczeg, Greg; Johns-Krull, Christopher; Akeson, Rachel; Ciardi, David

    2018-01-01

    Over the past thirty years, a detailed picture of star formation has emerged that highlights the importance of the interaction between a pre-main sequence (pre-MS) star and its protoplanetary disk. The properties of an emergent star, the lifetime of a protoplanetary disk, and the formation of planets are all, in part, determined by this star-disk interaction. Many stars, however, form in binary or higher-order systems where orbital dynamics are capable of fundamentally altering this star-disk interaction. Orbital resonances, especially in short-period systems, are capable of clearing the central region of a protoplanetary disk, leaving the possibility for three stable accretion disks: a circumstellar disk around each star and a circumbinary disk. In this model, accretion onto the stars is predicted to proceed in periodic streams that form at the inner edge of the circumbinary disk, cross the dynamically cleared gap, and feed circumstellar disks or accrete directly onto the stars themselves. This pulsed-accretion paradigm predicts bursts of accretion that are periodic with the orbital period, where the duration, amplitude, location in orbital phase, and which star if preferentially fed, all depend on the orbital parameters. To test these predictions, we have carried out intensive observational campaigns combining time-series, optical and near-infrared photometry with time-series, optical spectroscopy. These data are capable of monitoring the stellar accretion rate, the properties of warm circumstellar dust, and the kinematics of accretion flows, all as a function of orbital phase. In our sample of 9 pre-MS binaries with diverse orbital parameters, we search for evidence of periodic accretion events and seek to determine the role orbital parameters have on the characteristics of accretion events. Two results from our campaign will be highlighted: 1) the detection of periodic pulsed accretion events in DQ Tau and TWA 3A, and 2) evidence that the TWA 3A primary is the

  10. Does the upper main sequence extend across the whole H-R diagram. [radiative opacities of stellar evolution models

    NASA Technical Reports Server (NTRS)

    Stothers, R.; Chin, C.-W.

    1977-01-01

    The effect of using Carson's (1976) radiative opacities in evolutionary sequences of stellar models has been studied over the mass range from 7 to 60 solar masses. The opacities are very large in the outer part of the envelope and induce such enormous radii for masses greater than about 30 solar masses for a heavy-element fraction of 0.02 or about 20 solar masses for a heavy-element fraction of 0.04 that the evolutionary tracks during the phase of core hydrogen burning extend across the whole H-R diagram. The choice of the Schwarschild or Ledoux criterion for convection makes very little difference for the behavior of the tracks. Evolution through the effective-temperature range (in logarithms) of 3.6 to 4.0 occurs in all cases on a rapid (secular) time scale. Core helium burning takes place exclusively in the red-supergiant configuration for stellar masses exceeding 8 solar masses (heavy-element fraction of 0.02) or 6 solar masses (heavy-element fraction of 0.04). These stellar models seem to be in significantly better agreement with the observed distribution of bright stars on the H-R diagram than are the older models based on the Cox-Stewart opacities. It can be inferred that a large envelope opacity (e.g., Carson's) exists and that substantial mass loss takes place in very massive late-type supergiants.

  11. A Wide-field Survey for Transiting Hot Jupiters and Eclipsing Pre-main-sequence Binaries in Young Stellar Associations

    NASA Astrophysics Data System (ADS)

    Oelkers, Ryan J.; Macri, Lucas M.; Marshall, Jennifer L.; DePoy, Darren L.; Lambas, Diego G.; Colazo, Carlos; Stringer, Katelyn

    2016-09-01

    The past two decades have seen a significant advancement in the detection, classification, and understanding of exoplanets and binaries. This is due, in large part, to the increase in use of small-aperture telescopes (<20 cm) to survey large areas of the sky to milli-mag precision with rapid cadence. The vast majority of the planetary and binary systems studied to date consists of main-sequence or evolved objects, leading to a dearth of knowledge of properties at early times (<50 Myr). Only a dozen binaries and one candidate transiting Hot Jupiter are known among pre-main-sequence objects, yet these are the systems that can provide the best constraints on stellar formation and planetary migration models. The deficiency in the number of well characterized systems is driven by the inherent and aperiodic variability found in pre-main-sequence objects, which can mask and mimic eclipse signals. Hence, a dramatic increase in the number of young systems with high-quality observations is highly desirable to guide further theoretical developments. We have recently completed a photometric survey of three nearby (<150 pc) and young (<50 Myr) moving groups with a small-aperture telescope. While our survey reached the requisite photometric precision, the temporal coverage was insufficient to detect Hot Jupiters. Nevertheless, we discovered 346 pre-main-sequence binary candidates, including 74 high-priority objects for further study. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.

  12. Persistent Sub-Yearly Chromospheric Variations in Lower Main-Sequence Stars: Tau Booe and alpha Com

    NASA Technical Reports Server (NTRS)

    Maulik, Davesh; Donahue, Robert A.; Baliunas, Sallie L.

    1997-01-01

    The recent discoveries of extrasolar planetary systems around lower main-sequence stars such as tau Booe (HD 120136) has prompted further investigation into their stellar activity. A cursory analysis of tau Booe for cyclic chromospheric activity, based on its 30-yr record of Ca 2 H and K fluxes obtained as part of the HK Project from Mount Wilson Observatory, finds an intermediate, sub-yearly period (approximately 117 d) in chromospheric activity in addition to, and separate from, both its rotation (3.3 d) and long-term variability. As a persistent subyearly period in surface magnetic activity is unprecedented, we investigate this apparent anomaly further by examining chromospheric activity levels of other stars with similar mass, searching for variability in chromospheric activity with periods of less than one year, but longer than measured or predicted rotation. An examination of the time series of 40 mid-to-late F dwarfs yielded one other star for further analysis: alpha Com (HD 114378, P approximately 132 d). The variations for these two stars were checked for persistence and coherence. Based on these determinations, we eliminate the possibilities of rotation, long-term activity cycle, and the evolution of active regions as the cause of this variation in both stars. In particular, for tau Booe we infer that the phenomenon may be chromospheric in origin; however, beyond this, it is difficult to identify anything further regarding the cause of the activity variations, or even whether the observed modulation in the two stars have the same origin.

  13. The dot{M}-M_* relation of pre-main-sequence stars: a consequence of X-ray driven disc evolution

    NASA Astrophysics Data System (ADS)

    Ercolano, B.; Mayr, D.; Owen, J. E.; Rosotti, G.; Manara, C. F.

    2014-03-01

    We analyse current measurements of accretion rates on to pre-main-sequence stars as a function of stellar mass, and conclude that the steep dependence of accretion rates on stellar mass is real and not driven by selection/detection threshold, as has been previously feared. These conclusions are reached by means of statistical tests including a survival analysis which can account for upper limits. The power-law slope of the dot{M}-M_* relation is found to be in the range of 1.6-1.9 for young stars with masses lower than 1 M⊙. The measured slopes and distributions can be easily reproduced by means of a simple disc model which includes viscous accretion and X-ray photoevaporation. We conclude that the dot{M}-M_* relation in pre-main-sequence stars bears the signature of disc dispersal by X-ray photoevaporation, suggesting that the relation is a straightforward consequence of disc physics rather than an imprint of initial conditions.

  14. Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry.

    PubMed

    Asara, John M; Schweitzer, Mary H; Freimark, Lisa M; Phillips, Matthew; Cantley, Lewis C

    2007-04-13

    Fossilized bones from extinct taxa harbor the potential for obtaining protein or DNA sequences that could reveal evolutionary links to extant species. We used mass spectrometry to obtain protein sequences from bones of a 160,000- to 600,000-year-old extinct mastodon (Mammut americanum) and a 68-million-year-old dinosaur (Tyrannosaurus rex). The presence of T. rex sequences indicates that their peptide bonds were remarkably stable. Mass spectrometry can thus be used to determine unique sequences from ancient organisms from peptide fragmentation patterns, a valuable tool to study the evolution and adaptation of ancient taxa from which genomic sequences are unlikely to be obtained.

  15. 76 FR 55161 - Boston and Maine Corporation-Abandonment Exemption-Middlesex County, Mass.; Springfield Terminal...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-06

    ..., Mass.; Springfield Terminal Railway Company; Discontinuance of Service Exemption; Middlesex County, MA... Middlesex County, Mass. The line traverses United States Postal Service Zip Codes 02471 and 02138...

  16. Prospects for detecting decreasing exoplanet frequency with main-sequence age using PLATO

    NASA Astrophysics Data System (ADS)

    Veras, D.; Brown, D. J. A.; Mustill, A. J.; Pollacco, D.

    2017-09-01

    The space mission PLATO will usher in a new era of exoplanetary science by expanding our current inventory of transiting systems and constraining host star ages, which are currently highly uncertain. This capability might allow PLATO to detect changes in planetary system architecture with time, particularly because planetary scattering due to Lagrange instability may be triggered long after the system was formed. Here, we utilize previously published instability time-scale prescriptions to determine PLATO's capability to detect a trend of decreasing planet frequency with age for systems with equal- mass planets. For two-planet systems, our results demonstrate that PLATO may detect a trend for planet masses which are at least as massive as super-Earths. For systems with three or more planets, we link their initial compactness to potentially detectable frequency trends in order to aid future investigations when these populations will be better characterized.

  17. A frozen super-Earth orbiting a star at the bottom of the main sequence

    NASA Astrophysics Data System (ADS)

    Kubas, D.; Beaulieu, J. P.; Bennett, D. P.; Cassan, A.; Cole, A.; Lunine, J.; Marquette, J. B.; Dong, S.; Gould, A.; Sumi, T.; Batista, V.; Fouqué, P.; Brillant, S.; Dieters, S.; Coutures, C.; Greenhill, J.; Bond, I.; Nagayama, T.; Udalski, A.; Pompei, E.; Nürnberger, D. E. A.; Le Bouquin, J. B.

    2012-04-01

    Context. Microlensing is a unique method to probe low mass exoplanets beyond the snow line. However, the scientific potential of the new microlensing planet discovery is often unfulfilled due to lack of knowledge of the properties of the lens and source stars. The discovery light curve of the super Earth MOA-2007-BLG-192Lb suffers from significant degeneracies that limit what can be inferred about its physical properties. Aims: High resolution adaptive optics images allow us to solve this problem by resolving the microlensing target from all unrelated background stars, yielding the unique determination of magnified source and lens fluxes. This estimation permits the solution of our microlens model for the mass of the planet and its host and their physical projected separation. Methods: We observed the microlensing event MOA-2007-BLG-192 at high angular resolution in JHKs with the NACO adaptive optics system on the VLT while the object was still amplified by a factor 1.23 and then at baseline 18 months later. We analyzed and calibrated the NACO photometry in the standard 2MASS system in order to accurately constrain the source and the lens star fluxes. Results: We detect light from the host star of MOA-2007-BLG-192Lb, which significantly reduces the uncertainties in its characteristics as compared to earlier analyses. We find that MOA-2007-BLG-192L is most likely a very low mass late type M-dwarf (0.084-0.012+0.015 M⊙) at a distance of 660-70+100 pc orbited by a 3.2-1.8+5.2 M⊕ super-Earth at 0.66-0.22+0.51 AU. We then discuss the properties of this cold planetary system. Based on observations under ESO Prog.IDs: 279.C-5044(A) and 383-C.0495(A).

  18. THE DUSTIEST POST-MAIN SEQUENCE STARS IN THE MAGELLANIC CLOUDS

    SciTech Connect

    Jones, Olivia C.; Meixner, Margaret; Roman-Duval, Julia

    2015-10-01

    Using observations from the Herschel Inventory of The Agents of Galaxy Evolution (HERITAGE) survey of the Magellanic Clouds (MC), we have found 35 evolved stars and stellar end products that are bright in the far-infrared. These 28 (LMC) and 7 (SMC) sources were selected from the 529 evolved star candidates in the HERITAGE far-infrared point source catalogs. Our source identification method is based on spectral confirmation, spectral energy distribution characteristics, careful examination of the multiwavelength images and includes constraints on the luminosity, resulting in a thoroughly vetted list of evolved stars. These sources span a wide range in luminosity andmore » hence initial mass. We found 13 low- to intermediate-mass evolved stars, including asymptotic giant branch (AGB) stars, post-AGB stars, planetary nebulae, and a symbiotic star. We also identify 10 high mass stars, including 4 of the 15 known B[e] stars in the MC, 3 extreme red supergiants that are highly enshrouded by dust, a Luminous Blue Variable, a Wolf–Rayet star, and two supernova remnants. Further, we report the detection of 9 probable evolved objects which were previously undescribed in the literature. These sources are likely to be among the dustiest evolved objects in the MC. The Herschel emission may either be due to dust produced by the evolved star or it may arise from swept-up interstellar medium material.« less

  19. Deccan Volcanism: a main trigger of environmental changes leading to the KTB mass extinction?

    NASA Astrophysics Data System (ADS)

    Adatte, Thierry; Fantasia, Alicia; Samant, Bandana; Mohabey, Dhananjay; Keller, Gerta; Gertsch, Brian

    2014-05-01

    The nature and causes of mass extinctions in the geological past have remained topics of intense scientific debate for the past three decades. Central to this debate is the question of whether the eruption of large igneous provinces (LIP) was the primary mechanism driving the environmental changes that are commonly regarded as the proximate causes for four of the five major Phanerozoic extinction events. Model results predict that Deccan Traps emplacement was responsible for a strong increase in atmospheric pCO2 accompanied by rapid warming of 4°C that was followed by global cooling. During the warming phase, increased continental weathering of silicates associated with consumption of atmospheric CO2 likely resulted in the drawdown of greenhouse gases that reversed the warming trend leading to global cooling at the end of the Maastrichtian. Massive CO2 input together with massive release of SO2 may thus have triggered the mass extinctions in the marine realm as a result of ocean acidification leading to a carbon crisis and in the terrestrial realms due to acid rains. Global stress conditions related to these climatic changes are well known and documented in planktic foraminifera by a diversity decrease, species dwarfing, dominance of opportunistic species and near disappearance of specialized species. Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (base C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (Phase-2) occurred over a relatively short time interval in magnetic polarity C29r, whereas multiproxy studies from central and southeastern India place the Cretaceous-Tertiary (KT) mass extinction near the end of this main phase of Deccan volcanism suggesting a cause-and-effect relationship. In India a strong floral response is observed as a direct response to Deccan volcanic phase-2. In Lameta (infratrappean) sediments preceding the volcanic eruptions

  20. Limited-sequence magnetic resonance imaging in the evaluation of the ultrasonographically indeterminate pelvic mass.

    PubMed

    Chang, Silvia D; Cooperberg, Peter L; Wong, Anthony D; Llewellyn, Patrick A; Bilbey, James H

    2004-04-01

    To evaluate the usefulness of limited-sequence magnetic resonance imaging (MRI) in the elucidation of ultrasonographically indeterminate pelvic masses. This study focused only on pelvic masses in which the origin of the mass (uterine v. extrauterine) could not be determined by ultrasonography (US). The origin of a pelvic mass has clinical implications. A mass arising from the uterus is most likely to be a leiomyoma, which is a benign lesion, whereas an extrauterine mass will have a higher likelihood of malignancy and usually requires surgery. Eighty-one female patients whose pelvic mass was of indeterminate origin on US also underwent limited-sequence MRI of the pelvis. Most of the MRI examinations were performed on the same day as the US. Limited-sequence MRI sequences included a quick gradient-echo T1-weighted localizer and a fast spin-echo T2-weighted sequence. Final diagnoses were established by surgical pathology or by clinical and imaging follow-up. Limited-sequence MRI was helpful in 79 of the 81 cases (98%). Fifty-two of the 81 masses (64%) were leiomyomas. One was a leiomyosarcoma. The extrauterine masses (26/81 [32%]) were identified as 14 ovarian malignancies, 4 endometriomas, 3 dermoids, an ovarian fibroma, an infarcted fibrothecoma, an infarcted hemorrhagic cyst, a sigmoid diverticular abscess and a gastrointestinal stromal tumour of the ileum. In the other 2 cases (2/81 [2%]), the origin of the pelvic mass remained indeterminate. Both of these indeterminate masses showed low signal on T2-weighted images and were interpreted as probable leiomyomas. They were not surgically removed but were followed clinically and had a stable course. Limited-sequence MRI is a quick and efficient way to further evaluate ultrasonographically indeterminate pelvic masses. Limited-sequence MRI of the pelvis can suffice, in these cases, without requiring a full MRI examination.

  1. Understanding the scatter in the spatially resolved star formation main sequence of local massive spiral galaxies

    NASA Astrophysics Data System (ADS)

    Abdurro'uf; Akiyama, Masayuki

    2017-08-01

    We investigate the relation between star formation rate (SFR) and stellar mass (M*) at the sub-galactic scale (˜1 kpc) of 93 local (0.01 < z < 0.02) massive (M* > 1010.5 M⊙) spiral galaxies. To derive a spatially resolved SFR and stellar mass, we perform the so-called pixel-to-pixel spectral energy distribution (SED) fitting, which fits an observed spatially resolved multiband SED with a library of model SEDs using Bayesian statistics. We use two bands (far-ultraviolet or FUV and near-ultraviolet or NUV) and five bands (u, g, r, I and z) of imaging data from Galaxy Evolution Explorer (GALEX) and Sloan Digital Sky Survey (SDSS), respectively. We find a tight nearly linear relation between the local surface density of SFR (ΣSFR) and stellar mass (Σ*), which is flattened at high Σ*. The near linear relation between Σ* and ΣSFR suggests a constant specific SFR (sSFR) throughout the galaxies, and the scatter of the relation is directly related to that of the sSFR. Therefore, we analyse the variation of the sSFR in various scales. More massive galaxies on average have lower sSFR throughout them than less massive galaxies. We also find that barred galaxies have a lower sSFR in the core region than non-barred galaxies. However, in the outer region, the sSFRs of barred and non-barred galaxies are similar and lead to a similar total sSFR.

  2. Tidal Disruptions of Main Sequence Stars: Inferences from the Composition of the Fallback Material

    NASA Astrophysics Data System (ADS)

    Gallegos, Monica; Law-Smith, Jamie; Ramírez-Ruiz, Enrico

    2018-01-01

    We study black holes within galactic nuclei by analyzing the motions of stars swarming around them. When the conditions are right we can observe and analyze characteristics of the black hole’s destructive power. In this paper we analyze the case when a star lurks close enough to these gravity giants to be ripped apart. After disruption, material that is bound to the supermassive black hole accretes onto it and creates a powerful flare. The standard light curve of these flares is classically described by a t-5/3 power law in time. In this paper we adopt an analytical method to calculate the fallback rate and use Modules for Experiments in Stellar Astrophysics (MESA) to study the disruption of stars with masses between 0.8-3 M⊙ at various evolutionary stages. We move beyond the analysis of the light curve and peer into the interiors of the disrupted stars by studying the compositional features of the fallback material. With this work we can begin to constrain the nature of the stars that are tidally disrupted. We find that most stars develop nitrogen (14N) enhancements with carbon (12C) and oxygen (16O) depletion relative to solar abundance and find that these features are more pronounced for higher mass stars. We also find that these features become prominent only after the time of maximum fallback rate, tpeak, and are observed to appear at earlier times for stars of increasing mass. This work provides a clear spectral method to help classify the transient events we observe at the centers of galaxies.

  3. A tale of two anomalies: Depletion, dispersion, and the connection between the stellar lithium spread and inflated radii on the pre-main sequence

    SciTech Connect

    Somers, Garrett; Pinsonneault, Marc H., E-mail: somers@astronomy.ohio-state.edu, E-mail: pinsono@astronomy.ohio-state.edu

    2014-07-20

    We investigate lithium depletion in standard stellar models (SSMs) and main sequence (MS) open clusters, and explore the origin of the Li dispersion in young, cool stars of equal mass, age, and composition. We first demonstrate that SSMs accurately predict the Li abundances of solar analogs at the zero-age main sequence (ZAMS) within theoretical uncertainties. We then measure the rate of MS Li depletion by removing the [Fe/H]-dependent ZAMS Li pattern from three well-studied clusters, and comparing the detrended data. MS depletion is found to be mass-dependent, in the sense of more depletion at low mass. A dispersion in Limore » abundance at fixed T{sub eff} is nearly universal, and sets in by ∼200 Myr. We discuss mass and age dispersion trends, and the pattern is mixed. We argue that metallicity impacts the ZAMS Li pattern, in agreement with theoretical expectations but contrary to the findings of some previous studies, and suggest Li as a test of cluster metallicity. Finally, we argue that a radius dispersion in stars of fixed mass and age, during the epoch of pre-MS Li destruction, is responsible for the spread in Li abundances and the correlation between rotation and Li in young cool stars, most well known in the Pleiades. We calculate stellar models, inflated to match observed radius anomalies in magnetically active systems, and the resulting range of Li abundances reproduces the observed patterns of young clusters. We discuss ramifications for pre-MS evolutionary tracks and age measurements of young clusters, and suggest an observational test.« less

  4. The rich dynamics of planets in post-main-sequence systems

    NASA Astrophysics Data System (ADS)

    Veras, Dimitri

    2014-05-01

    Mounting observations of ongoing and abundant ingestion of rocky and watery circumstellar material into white dwarf atmospheres have reinvigorated several subfields of dynamical astronomy. These observations demonstrate the importance of modeling planetary systems through the giant branch and white dwarf phases of stellar evolution. Consequently, dynamicists have renewed interest in the few-body problem with mass loss, tidal interactions of bloated stars, disrupted asteroids, sublimating accretion discs, and long-term stability analyses. Here, I outline these developments as well as remaining outstanding questions.

  5. Mass spectrometry sequencing of long digital polymers facilitated by programmed inter-byte fragmentation.

    PubMed

    Al Ouahabi, Abdelaziz; Amalian, Jean-Arthur; Charles, Laurence; Lutz, Jean-François

    2017-10-17

    In the context of data storage miniaturization, it was recently shown that digital information can be stored in the monomer sequences of non-natural macromolecules. However, the sequencing of such digital polymers is currently limited to short chains. Here, we report that intact multi-byte digital polymers can be sequenced in a moderate resolution mass spectrometer and that full sequence coverage can be attained without requiring pre-analysis digestion or the help of sequence databases. In order to do so, the polymers are designed to undergo controlled fragmentations in collision-induced dissociation conditions. Each byte of the sequence is labeled by an identification tag and a weak alkoxyamine group is placed between 2 bytes. As a consequence of this design, the NO-C bonds break first upon collisional activation, thus leading to a pattern of mass tag-shifted intact bytes. Afterwards, each byte is individually sequenced in pseudo-MS 3 conditions and the whole sequence is found.Digital information can be stored in monomer sequences of non-natural macromolecules, but only short chains can be read. Here the authors show long multi-byte digital polymers sequenced in a moderate resolution mass spectrometer. Full sequence coverage can be attained without pre-analysis digestion or the help from sequence databases.

  6. VizieR Online Data Catalog: Lower main-sequence stars fundamental param. (Casagrande+, 2006)

    NASA Astrophysics Data System (ADS)

    Casagrande, L.; Portinari, L.; Flynn, C.

    2007-06-01

    To recover accurate bolometric fluxes and temperatures for the stars, we have obtained accurate and homogeneous Johnson-Cousins BV(RI)C and JHKs photometry for all the 186 stars in our initial sample. For most of the stars in our sample with declination north of DE=-25{deg}, we have made our own photometric observations from April to December 2004. Observations were done from Finland in full remote mode, using the 35-cm telescope piggybacked on the Swedish 60-cm telescope located at La Palma in the Canary Islands. A SBIG charge-coupled device was used through all the observations. Johnson-Cousins BV(RI)C colours were obtained for all stars. Infrared JHKs photometry for the sample has been taken from the Two-Micron All-Sky Survey (2MASS) catalogue. (1 data file).

  7. VizieR Online Data Catalog: Lower main-sequence stars fundamental param. (Casagrande+, 2006)

    NASA Astrophysics Data System (ADS)

    Casagrande, L.; Portinari, L.; Flynn, C.

    2007-06-01

    To recover accurate bolometric fluxes and temperatures for the stars, we have obtained accurate and homogeneous Johnson-Cousins BV(RI)C and JHKs photometry for all the 186 stars in our initial sample. For most of the stars in our sample with declination north of DE=-25°, we have made our own photometric observations from April to December 2004. Observations were done from Finland in full remote mode, using the 35-cm telescope piggybacked on the Swedish 60-cm telescope located at La Palma in the Canary Islands. A SBIG charge-coupled device was used through all the observations. Johnson-Cousins BV(RI)C colours were obtained for all stars. Infrared JHKs photometry for the sample has been taken from the Two-Micron All-Sky Survey (2MASS) catalogue. (1 data file).

  8. [The Main Gate Syndrome: a new format in mass-casualty victim "surge" management?].

    PubMed

    Sockeel, P; De Saint Roman, C; Massoure, M-P; Nadaud, J; Cinquetti, G; Chatelain, E

    2008-01-01

    Recent suicide bombings pose the novel problem for Trauma Centers of the massive simultaneous arrival of many gravely wounded patients. We report the experience of the French-German Military Trauma Group, a Level 2 Trauma Center, in Afghanistan during the wave of suicide bombings in February 2007. Fourteen casualties were received. A first triage was carried out by the U S Army Level I group prior to evacuation. A second surgical triage was carried out with systematic ultrasound exam. Four cases (ISS>25) were re-categorized and underwent emergency surgical procedures. Suicide bombing in crowded locations near an evacuation hospital may overwhelm the medical resources of the receiving center. It has been referred to as "The Main Gate Syndrome." We introduced the novel concept of a semi-evacuation hospital or receiving center where a second surgical triage was carried out. These exceptional circumstances require open-minded flexibility, a tailored approach, and close cooperation between surgeons and anesthetists to share experience, opinions, and ideas. In the setting of mass casualties, emergency ultrasound exam was shown to be a valuable and effective tool by virtue of its mobility, reproducibility, and immediate results.

  9. Detection of methamphetamine and its main metabolite in fingermarks by liquid chromatography-mass spectrometry.

    PubMed

    Zhang, Ting; Chen, Xueguo; Yang, Ruiqin; Xu, Yingjian

    2015-03-01

    A sensitive and efficient method applying liquid chromatography-mass spectrometry for the analysis of methamphetamine and its main metabolite in fingermark deposits was described. Using this method, good linear relationship of methamphetamine was obtained in the range of 0.005μg to 0.5μg per cotton swab, the limit of detection was 1.5ng per cotton swab, the limit of quantitation was 5.0ng per cotton swab and the average values of recovery ratios were above 70.1%. Moreover, the influence factors for the detection of methamphetamine in fingermarks, such as kinds of substrates, development methods and extraction methods, were all discussed in details. The results showed that good recovery ratios could be obtained on painted wood and smooth substrates surfaces. Development methods in commercial powder could not influence the quality of examination of exogenous drug in latent fingermark. Furthermore, the results indicated that the method mentioned here could be applied in the analysis of forensic trace evidences and samples obtained in clinically addicted cases. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  10. OLD MAIN-SEQUENCE TURNOFF PHOTOMETRY IN THE SMALL MAGELLANIC CLOUD. II. STAR FORMATION HISTORY AND ITS SPATIAL GRADIENTS

    SciTech Connect

    Noel, Noelia E. D.; Gallart, Carme; Hidalgo, Sebastian L.

    2009-11-10

    We present a quantitative analysis of the star formation history (SFH) of 12 fields in the Small Magellanic Cloud (SMC) based on unprecedented deep [(B - R), R] color-magnitude diagrams (CMDs). Our fields reach down to the oldest main-sequence turnoff with a high photometric accuracy, which is vital for obtaining accurate SFHs, particularly at intermediate and old ages. We use the IAC-pop code to obtain the SFH, using synthetic CMDs generated with IAC-star. We obtain the SFH as a function psi(t, z) of age and metallicity. We also consider several auxiliary functions: the initial mass function (IMF), phi(m), and amore » function accounting for the frequency and relative mass distribution of binary stars, beta(f, q). We find that there are several main periods of enhancement of star formation: a young one peaked at approx0.2-0.5 Gyr old, only present in the eastern and in the central-most fields; two at intermediate ages present in all fields: a conspicuous one peaked at approx4-5 Gyr, and a less significant one peaked at approx1.5-2.5; and an old one, peaked at approx10 Gyr in all fields but the western ones. In the western fields, this old enhancement splits into two, one peaked at approx8 Gyr old and another at approx12 Gyr old. This 'two-enhancement' zone is unaffected by our choice of stellar evolutionary library but more data covering other fields of the SMC are necessary in order to ascertain its significancy. Correlation between star formation rate enhancements and SMC-Milky Way encounters is not clear. Some correlation could exist with encounters taken from the orbit determination of Kallivayalil et al. But our results would also fit in a first pericenter passage scenario like the one claimed by Besla et al. For SMC-Large Magellanic Cloud encounters, we find a correlation only for the most recent encounter approx0.2 Gyr ago. This coincides with the youngest psi(t) enhancement peaked at these ages in our eastern fields. The population younger than 1 Gyr

  11. On the determination of the He abundance distribution in globular clusters from the width of the main sequence

    NASA Astrophysics Data System (ADS)

    Cassisi, Santi; Salaris, Maurizio; Pietrinferni, Adriano; Hyder, David

    2017-01-01

    One crucial piece of information to study the origin of multiple stellar populations in globular clusters is the range of initial helium abundances ΔY amongst the sub-populations hosted by each cluster. These estimates are commonly obtained by measuring the width in colour of the unevolved main sequence in an optical colour-magnitude diagram (CMD). The measured colour spread is then compared with predictions from theoretical stellar isochrones with varying initial He abundances to determine ΔY. The availability of UV/optical magnitudes, thanks to the Hubble Space Telescope UV Legacy Survey of Galactic GCs project, will allow the homogeneous determination of ΔY for a large Galactic globular cluster sample. From a theoretical point of view, accurate UV CMDs can efficiently disentangle the various sub-populations, and main sequence colour differences in the ACS F606W - (F606W - F814W) diagram allow an estimate of ΔY. We demonstrate that from a theoretical perspective, the (F606W - F814W) colour is an extremely reliable He-abundance indicator. The derivative dY/d(F606W - F814W), computed at a fixed luminosity along the unevolved main sequence, is largely insensitive to the physical assumptions made in stellar model computations, being more sensitive to the choice of the bolometric correction scale, and is only slightly dependent on the adopted set of stellar models. From a theoretical point of view, the (F606W - F814W) colour width of the cluster main sequence is therefore a robust diagnostic of the ΔY range.

  12. Searching for gas giant planets on Solar system scales - a NACO/APP L'-band survey of A- and F-type main-sequence stars

    NASA Astrophysics Data System (ADS)

    Meshkat, T.; Kenworthy, M. A.; Reggiani, M.; Quanz, S. P.; Mamajek, E. E.; Meyer, M. R.

    2015-11-01

    We report the results of a direct imaging survey of A- and F-type main-sequence stars searching for giant planets. A/F stars are often the targets of surveys, as they are thought to have more massive giant planets relative to solar-type stars. However, most imaging is only sensitive to orbital separations >30 au, where it has been demonstrated that giant planets are rare. In this survey, we take advantage of the high-contrast capabilities of the Apodizing Phase Plate coronagraph on NACO at the Very Large Telescope. Combined with optimized principal component analysis post-processing, we are sensitive to planetary-mass companions (2-12 MJup) at Solar system scales (≤30 au). We obtained data on 13 stars in the L' band and detected one new companion as part of this survey: an M6.0 ± 0.5 dwarf companion around HD 984. We re-detect low-mass companions around HD 12894 and HD 20385, both reported shortly after the completion of this survey. We use Monte Carlo simulations to determine new constraints on the low-mass (<80 MJup) companion frequency, as a function of mass and separation. Assuming solar-type planet mass and separation distributions, normalized to the planet frequency appropriate for A-stars, and the observed companion mass-ratio distribution for stellar companions extrapolated to planetary masses, we derive a truncation radius for the planetary mass companion surface density of <135 au at 95 per cent confidence.

  13. Deep water masses and sediments are main compartments for polychlorinated biphenyls in the Arctic Ocean.

    PubMed

    Sobek, Anna; Gustafsson, Örjan

    2014-06-17

    There is a wealth of studies of polychlorinated biphenyls (PCB) in surface water and biota of the Arctic Ocean. Still, there are no observation-based assessments of PCB distribution and inventories in and between the major Arctic Ocean compartments. Here, the first water column distribution of PCBs in the central Arctic Ocean basins (Nansen, Amundsen, and Makarov) is presented, demonstrating nutrient-like vertical profiles with 5-10 times higher concentrations in the intermediate and deep water masses than in surface waters. The consistent vertical profiles in all three Arctic Ocean basins likely reflect buildup of PCBs transported from the shelf seas and from dissolution and/or mineralization of settling particles. Combined with measurement data on PCBs in other Arctic Ocean compartments collected over the past decade, the total Arctic Ocean inventory of ∑7PCB was estimated to 182 ± 40 t (±1 standard error of the mean), with sediments (144 ± 40 t), intermediate (5 ± 1 t) and deep water masses (30 ± 2 t) storing 98% of the PCBs in the Arctic Ocean. Further, we used hydrographic and carbon cycle parametrizations to assess the main pathways of PCBs into and out of the Arctic Ocean during the 20th century. River discharge appeared to be the major pathway for PCBs into the Arctic Ocean with 115 ± 11 t, followed by ocean currents (52 ± 17 t) and net atmospheric deposition (30 ± 28 t). Ocean currents provided the only important pathway out of the Arctic Ocean, with an estimated cumulative flux of 22 ± 10 t. The observation-based inventory of ∑7PCB of 182 ± 40 t is consistent with the contemporary inventory based on cumulative fluxes for ∑7PCB of 173 ± 36 t. Information on the concentration and distribution of PCBs in the deeper compartments of the Arctic Ocean improves our understanding of the large-scale fate of POPs in the Arctic and may also provide a means to test and improve models used to assess the fate of organic pollutants in the Arctic.

  14. Extreme value statistics for two-dimensional convective penetration in a pre-main sequence star

    NASA Astrophysics Data System (ADS)

    Pratt, J.; Baraffe, I.; Goffrey, T.; Constantino, T.; Viallet, M.; Popov, M. V.; Walder, R.; Folini, D.

    2017-08-01

    Context. In the interior of stars, a convectively unstable zone typically borders a zone that is stable to convection. Convective motions can penetrate the boundary between these zones, creating a layer characterized by intermittent convective mixing, and gradual erosion of the density and temperature stratification. Aims: We examine a penetration layer formed between a central radiative zone and a large convection zone in the deep interior of a young low-mass star. Using the Multidimensional Stellar Implicit Code (MUSIC) to simulate two-dimensional compressible stellar convection in a spherical geometry over long times, we produce statistics that characterize the extent and impact of convective penetration in this layer. Methods: We apply extreme value theory to the maximal extent of convective penetration at any time. We compare statistical results from simulations which treat non-local convection, throughout a large portion of the stellar radius, with simulations designed to treat local convection in a small region surrounding the penetration layer. For each of these situations, we compare simulations of different resolution, which have different velocity magnitudes. We also compare statistical results between simulations that radiate energy at a constant rate to those that allow energy to radiate from the stellar surface according to the local surface temperature. Results: Based on the frequency and depth of penetrating convective structures, we observe two distinct layers that form between the convection zone and the stable radiative zone. We show that the probability density function of the maximal depth of convective penetration at any time corresponds closely in space with the radial position where internal waves are excited. We find that the maximal penetration depth can be modeled by a Weibull distribution with a small shape parameter. Using these results, and building on established scalings for diffusion enhanced by large-scale convective motions, we

  15. A new method to disentangle the rotational velocities of stars: Application to main-sequence field Stars

    NASA Astrophysics Data System (ADS)

    Curé, M.; Rial, D. F.; Cassetti, J.; Christen, A.

    2014-10-01

    The projected rotational velocity v sin i is a fundamental observable quantity. In order to obtain the rotational velocity distribution of a sample of v sin i, Chandrasekhar & Münch (1950) developed a formalism to obtain this distribution under the assumption that rotational axes are uniformly distributed, but this method is not usually applied due to an intrinsic numerical problem associated to the derivative of an Abel's integral. An alternative iterative method was developed by Lucy (1974) to disentangle the distribution function of this kind of inverse problem, but this method has no convergence criteria. Here we present a new method to disentangle the distribution of rotational velocities, based on Chandrasekhar & Münch (1950) formalism. We obtain the cumulative distribution function (CDF) of the rotational velocities from projected velocities (v sin i) under the standard assumption of uniform distributed rotational axes. Through simulations the method is tested using a) theoretical Maxwellian distribution functions for the rotational velocity distribution and b) with a sample of about 12.500 main-sequence field stars. Our main results are: The method is robust and in just one step gives the cumulative distribution function of rotational velocities. When applied to theoretical distributions it recovers the CDF with very high confidence. When applied to real data, we recover the results from Carvalho et al. (2009) proving that the velocity distribution function of main-sequence field stars is non-Maxwellian and are better described by Tsallis or Kaniadakis distribution functions.

  16. EXPORT: Spectral classification and projected rotational velocities of Vega-type and pre-main sequence stars

    NASA Astrophysics Data System (ADS)

    Mora, A.; Merín, B.; Solano, E.; Montesinos, B.; de Winter, D.; Eiroa, C.; Ferlet, R.; Grady, C. A.; Davies, J. K.; Miranda, L. F.; Oudmaijer, R. D.; Palacios, J.; Quirrenbach, A.; Harris, A. W.; Rauer, H.; Collier Cameron, A.; Deeg, H. J.; Garzón, F.; Penny, A.; Schneider, J.; Tsapras, Y.; Wesselius, P. R.

    2001-10-01

    In this paper we present the first comprehensive results extracted from the spectroscopic campaigns carried out by the EXPORT (EXoPlanetary Observational Research Team) consortium. During 1998-1999, EXPORT carried out an intensive observational effort in the framework of the origin and evolution of protoplanetary systems in order to obtain clues on the evolutionary path from the early stages of the pre-main sequence to stars with planets already formed. The spectral types of 70 stars, and the projected rotational velocities, v sin i, of 45 stars, mainly Vega-type and pre-main sequence, have been determined from intermediate- and high-resolution spectroscopy, respectively. The first part of the work is of fundamental importance in order to accurately place the stars in the HR diagram and determine the evolutionary sequences; the second part provides information on the kinematics and dynamics of the stars and the evolution of their angular momentum. The advantage of using the same observational configuration and methodology for all the stars is the homogeneity of the set of parameters obtained. Results from previous work are revised, leading in some cases to completely new determinations of spectral types and projected rotational velocities; for some stars no previous studies were available. Tables 1 and 2 are only, and Table 6 also, available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/378/116 Based on observations made with the Isaac Newton and the William Herschel telescopes operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  17. 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

    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.

  18. Extended Star-formation and Disk-like Kinematics in a z~3 Massive ``Main-Sequence'' Galaxy through [CII] Imaging and Multi-J CO Line Observations

    NASA Astrophysics Data System (ADS)

    Leung, Tsz Kuk Daisy; Riechers, Dominik A.; Clements, David; Cooray, Asantha; Ivison, Rob; Perez-Fournon, Ismael; Wardlow, Julie

    2018-01-01

    Dusty star-forming galaxies (SFG) at high redshifts are the main contributors to the comoving star formation rate (SFR) density, which peaks between the redshift of z=1-3 (``Cosmic Noon''). Yet, new insights into their gas dynamics, and thus, structural evolution are awaiting spatially resolved observations. I will present the latest results from our kpc-scale [CII] imaging and multi-J CO line observations obtained with ALMA, CARMA, PdBI, and the VLA in one of the most massive ``main-sequence'' disk galaxy known. XMM03 (z=2.9850) is an extremely IR-luminous galaxy with a SFR of ~3000 Msun/yr, but its molecular gas excitation is surprisingly similar to the Milky Way up to J=5, which is in stark contrast with most high-z galaxies studied to date. The monotonic velocity gradient seen in the [CII] line emission suggest that it is a rotating disk galaxy. Based on the molecular gas surface density and the far-UV radiation flux determined from photo-dissociation region (PDR) modeling, the star-forming environment of XMM03 is similar to nearby SFGs. These findings together with the ~1100 km/s wide CO(1-0) line across the entire disk of ~8 kpc in radius showcase the different interstellar medium (ISM) environment that we are probing at the most massive end of galaxies in the early Universe. With a stellar mass of M*~10^12, its specific SFR is consistent with an extrapolation of the ``star-forming main-sequence'' up to M*~10^12 Msun at z~3. Our findings therefore confirm the prevalence of disk-wide star formation responsible for assembling most of the stellar masses toward the ``Cosmic Noon''.

  19. High resolution X-ray spectroscopy of pre-main-sequence stars: TWA 5 and PZ Tel

    NASA Astrophysics Data System (ADS)

    Argiroffi, C.; Drake, J. J.; Harnden, F. R.; Maggio, A.; Peres, G.; Sciortino, S.; Stelzer, B.; Neuhäuser, R.

    2005-03-01

    We report on the analysis of high resolution X-ray spectra of two pre-main-sequence stars: TWA 5 (observed with XMM-Newton) and PZ Telescopii (observed with Chandra/HETGS). TWA 5 is a classical T Tauri star in the TW Hydrae association while PZ Tel is a rapidly rotating weak-lined T Tauri star in the beta-Pictoris moving group. For both stars we have reconstructed the emission measure distribution and derived the coronal abundances to check for possible patterns of the abundances related to the first ionization potential of the various elements. We have also derived estimates of the plasma density from the analysis of the He-like triplets. We compare the characteristics of our targets with those of other pre-main sequence stars previously analyzed by other authors: TW Hya, HD 98800 and HD 283572. Our findings suggest that X-ray emission from classical T Tauri and weak-lined T Tauri stars is produced in all cases by magnetically-heated coronae, except for TW Hya which has unique plasma temperatures and densities. Moreover we derive that TWA 5 has the same peculiar Ne/Fe abundance ratio as TW Hya.

  20. How Dusty Is Alpha Centauri? Excess or Non-excess over the Infrared Photospheres of Main-sequence Stars

    NASA Technical Reports Server (NTRS)

    Wiegert, J.; Liseau, R.; Thebault, P.; Olofsson, G.; Mora, A.; Bryden, G.; Marshall, J. P.; Eiroa, C.; Montesinos, B.; Ardila, D.; hide

    2014-01-01

    Context. Debris discs around main-sequence stars indicate the presence of larger rocky bodies. The components of the nearby, solar-type binary Centauri have metallicities that are higher than solar, which is thought to promote giant planet formation. Aims. We aim to determine the level of emission from debris around the stars in the Cen system. This requires knowledge of their photospheres.Having already detected the temperature minimum, Tmin, of CenA at far-infrared wavelengths, we here attempt to do the same for the moreactive companion Cen B. Using the Cen stars as templates, we study the possible eects that Tmin may have on the detectability of unresolveddust discs around other stars. Methods.We used Herschel-PACS, Herschel-SPIRE, and APEX-LABOCA photometry to determine the stellar spectral energy distributions in thefar infrared and submillimetre. In addition, we used APEX-SHeFI observations for spectral line mapping to study the complex background around Cen seen in the photometric images. Models of stellar atmospheres and of particulate discs, based on particle simulations and in conjunctionwith radiative transfer calculations, were used to estimate the amount of debris around these stars. Results. For solar-type stars more distant than Cen, a fractional dust luminosity fd LdustLstar 2 107 could account for SEDs that do not exhibit the Tmin eect. This is comparable to estimates of fd for the Edgeworth-Kuiper belt of the solar system. In contrast to the far infrared,slight excesses at the 2:5 level are observed at 24 m for both CenA and B, which, if interpreted as due to zodiacal-type dust emission, wouldcorrespond to fd (13) 105, i.e. some 102 times that of the local zodiacal cloud. Assuming simple power-law size distributions of the dustgrains, dynamical disc modelling leads to rough mass estimates of the putative Zodi belts around the Cen stars, viz.4106 M$ of 4 to 1000 msize grains, distributed according to n(a) a3:5. Similarly, for filled-in Tmin

  1. The rate and efficiency of high-mass star formation along the Hubble sequence

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas A.; Young, Judith S.

    1991-01-01

    Data obtained with IRAS are used to compare and contrast the global star formation rates for a galactic sample which represents essentially all known noninteracting spiral and lenticular galaxies within 40 Mpc. The distribution of 60 micron luminosity is similar for spirals of types Sa-Scd inclusively, although the luminosities of the very early and very late types are, on average, one order of magnitude lower. High-mass star formation rates are similar for early, intermediate, and late type spirals, and the average high-mass star formation rate per unit molecular gas mass is independent of type for spiral galaxies. A remarkable homogeneity exists in the high-mass star-forming capabilities of spiral galaxies, particularly among the Sa-Scd types. The Hubble sequence is therefore not a sequence in the present-day rate or production efficiency of high-mass stars.

  2. Texture analysis of common renal masses in multiple MR sequences for prediction of pathology

    NASA Astrophysics Data System (ADS)

    Hoang, Uyen N.; Malayeri, Ashkan A.; Lay, Nathan S.; Summers, Ronald M.; Yao, Jianhua

    2017-03-01

    This pilot study performs texture analysis on multiple magnetic resonance (MR) images of common renal masses for differentiation of renal cell carcinoma (RCC). Bounding boxes are drawn around each mass on one axial slice in T1 delayed sequence to use for feature extraction and classification. All sequences (T1 delayed, venous, arterial, pre-contrast phases, T2, and T2 fat saturated sequences) are co-registered and texture features are extracted from each sequence simultaneously. Random forest is used to construct models to classify lesions on 96 normal regions, 87 clear cell RCCs, 8 papillary RCCs, and 21 renal oncocytomas; ground truths are verified through pathology reports. The highest performance is seen in random forest model when data from all sequences are used in conjunction, achieving an overall classification accuracy of 83.7%. When using data from one single sequence, the overall accuracies achieved for T1 delayed, venous, arterial, and pre-contrast phase, T2, and T2 fat saturated were 79.1%, 70.5%, 56.2%, 61.0%, 60.0%, and 44.8%, respectively. This demonstrates promising results of utilizing intensity information from multiple MR sequences for accurate classification of renal masses.

  3. Automated identification of amino acid sequence variations in proteins by HPLC/microspray tandem mass spectrometry.

    PubMed

    Gatlin, C L; Eng, J K; Cross, S T; Detter, J C; Yates, J R

    2000-02-15

    Amino acid sequence variations resulting from single-nucleotide polymorphisms (SNPs) were identified using a novel mass spectrometric method. This method obtains 99+% protein sequence coverage for human hemoglobin in a single LC-microspray tandem mass spectrometry (microLC-MS/MS) experiment. Tandem mass spectrometry data was analyzed using a modified version of the computer program SEQUEST to identify the sequence variations. Conditions of sample preparation, chromatographic separation, and data collection were optimized to correctly identify amino acid changes in six variants of human hemoglobin (Hb C, Hb E, Hb D-Los Angeles, Hb G-Philadelphia, Hb Hope, and Hb S). Hemoglobin proteins were isolated and purified, dehemed, (S)-carboxyami-domethylated, and then subjected to a combination proteolytic digestion to obtain a complex peptide mixture with multiple overlaps in sequence. Reversed-phase chromatographic separation of peptides was achieved on-line with MS utilizing a robust fritless microelectrospray interface. Tandem mass spectrometry was performed on an ion trap mass spectrometer using automated data-dependent MS/MS procedures. Tandem mass spectra were collected from the five most abundant ions in each scan using dynamic and isotopic exclusion to minimize redundancy. The spectra were analyzed by a version of the SEQUEST algorithm modified to identify amino acid substations resulting from SNPs.

  4. A dynamic programming approach to de novo peptide sequencing via tandem mass spectrometry.

    PubMed

    Chen, T; Kao, M Y; Tepel, M; Rush, J; Church, G M

    2001-01-01

    Tandem mass spectrometry fragments a large number of molecules of the same peptide sequence into charged molecules of prefix and suffix peptide subsequences and then measures mass/charge ratios of these ions. The de novo peptide sequencing problem is to reconstruct the peptide sequence from a given tandem mass spectral data of k ions. By implicitly transforming the spectral data into an NC-spectrum graph G (V, E) where /V/ = 2k + 2, we can solve this problem in O(/V//E/) time and O(/V/2) space using dynamic programming. For an ideal noise-free spectrum with only b- and y-ions, we improve the algorithm to O(/V/ + /E/) time and O(/V/) space. Our approach can be further used to discover a modified amino acid in O(/V//E/) time. The algorithms have been implemented and tested on experimental data.

  5. Detection of a dozen X-ray-emitting main-sequence B6-A3 stars in Orion

    NASA Technical Reports Server (NTRS)

    Caillault, Jean-Pierre; Zoonematkermani, Saeid

    1989-01-01

    The detection of 12 X-ray-emitting main-sequence B6-A3 stars in the Orion Nebula is reported. The luminosity of these stars in the 0.2-3.5 keV band is considerably in excess of field stars of the same spectral type. Consideration is given to the possibilities that these stars may not actually be the source of the X-rays, but that the emission may be attributable to T Tauri or 'naked' T Tauri star companions, or that these hot stars are indeed the sources of emission and that current theories of X-ray emission from early-type stars must be amended.

  6. Using the phase shift to asymptotically characterize the dipolar mixed modes in post-main-sequence stars

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Christensen-Dalsgaard, J.; Cunha, M.

    2018-03-01

    Mixed modes have been extensively observed in post-main-sequence stars by the Kepler and CoRoT space missions. The mixture of the p and g modes can be measured by the dimensionless coefficient q, the so-called coupling strength factor. In this paper, we discuss the utility of the phase shifts θ from the eigenvalue condition for mixed modes as a tool to characterize dipolar mixed modes from the theoretical as well as the practical point of view. Unlike the coupling strength, whose variation in a given star is very small over the relevant frequency range, the phase shifts vary significantly for different modes. The analysis in terms of θ can also provide a better understanding of the pressure and gravity radial order for a given mixed mode. Observed frequencies of the Kepler red-giant star KIC 3744043 are used to test the method. The results are very promising.

  7. The Solar Neighborhood. XLI. A Study of the Wide Main Sequence for M Dwarfs—Long-term Photometric Variability

    SciTech Connect

    Clements, Tiffany D.; Jao, Wei-Chun; Silverstein, Michele L.

    2017-09-01

    We report findings from a long-term photometric variability study of M dwarfs carried out at the SMARTS 0.9 m telescope at the Cerro Tololo Inter-American Observatory. As part of a multi-faceted effort to investigate the range of luminosities of M dwarfs of a given color on the Hertzsprung–Russell Diagram, 76 M dwarfs have been observed for 3–17 years in the Johnson–Kron–Cousins V band. We find that stars elevated above the center of the main sequence distribution tend to have higher levels of variability, likely caused by magnetic activity, than their fainter counterparts below the center. This study provides insight intomore » how the long-term magnetic activity of these stars may be affecting their sizes, luminosities, and thus positions on the H-R Diagram.« less

  8. The Solar Neighborhood. XLI. A Study of the Wide Main Sequence for M Dwarfs—Long-term Photometric Variability

    NASA Astrophysics Data System (ADS)

    Clements, Tiffany D.; Henry, Todd J.; Hosey, Altonio D.; Jao, Wei-Chun; Silverstein, Michele L.; Winters, Jennifer G.; Dieterich, Sergio B.; Riedel, Adric R.

    2017-09-01

    We report findings from a long-term photometric variability study of M dwarfs carried out at the SMARTS 0.9 m telescope at the Cerro Tololo Inter-American Observatory. As part of a multi-faceted effort to investigate the range of luminosities of M dwarfs of a given color on the Hertzsprung-Russell Diagram, 76 M dwarfs have been observed for 3-17 years in the Johnson-Kron-Cousins V band. We find that stars elevated above the center of the main sequence distribution tend to have higher levels of variability, likely caused by magnetic activity, than their fainter counterparts below the center. This study provides insight into how the long-term magnetic activity of these stars may be affecting their sizes, luminosities, and thus positions on the H-R Diagram.

  9. Main results of the analyses related to a few Reference Accident Sequences of NET/ITER tritium systems

    NASA Astrophysics Data System (ADS)

    Ciattaglia, S.; Di Pace, L.; Rizzello, C.; Visca, E.

    1993-06-01

    Based on the existing conceptual design, a set of Reference Accident Sequences (RAS) has been defined by tritium system experts. This paper presents the main results related to a preliminary analysis of the following RAS for fuel cycle systems: hydrogen detonation in the isotopic separation system, rupture of a cryoline in a cryopump, fire in the long-term storage beds, and mechanical faulty operation in the pellet injector. The systems and the component mode of operation have been analyzed, as well as the characteristics of all streams, the inventory of T, D, and H, and the energy released under accident conditions. Failures that could give rise to the release of tritium and/or to the formation and ignition of oxygen/hydrogen mixtures and failures that could lead to containment pressure transients are discussed and examined.

  10. Proteogenomics: Integrating Next-Generation Sequencing and Mass Spectrometry to Characterize Human Proteomic Variation

    NASA Astrophysics Data System (ADS)

    Sheynkman, Gloria M.; Shortreed, Michael R.; Cesnik, Anthony J.; Smith, Lloyd M.

    2016-06-01

    Mass spectrometry-based proteomics has emerged as the leading method for detection, quantification, and characterization of proteins. Nearly all proteomic workflows rely on proteomic databases to identify peptides and proteins, but these databases typically contain a generic set of proteins that lack variations unique to a given sample, precluding their detection. Fortunately, proteogenomics enables the detection of such proteomic variations and can be defined, broadly, as the use of nucleotide sequences to generate candidate protein sequences for mass spectrometry database searching. Proteogenomics is experiencing heightened significance due to two developments: (a) advances in DNA sequencing technologies that have made complete sequencing of human genomes and transcriptomes routine, and (b) the unveiling of the tremendous complexity of the human proteome as expressed at the levels of genes, cells, tissues, individuals, and populations. We review here the field of human proteogenomics, with an emphasis on its history, current implementations, the types of proteomic variations it reveals, and several important applications.

  11. Stellar Variability at the Main-sequence Turnoff of the Intermediate-age LMC Cluster NGC 1846

    NASA Astrophysics Data System (ADS)

    Salinas, R.; Pajkos, M. A.; Vivas, A. K.; Strader, J.; Contreras Ramos, R.

    2018-04-01

    Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. Here we present Gemini-S/Gemini Multi-Object Spectrometer (GMOS) time series observations of the IA cluster NGC 1846. Using differential image analysis, we identified 73 new variable stars, with 55 of those being of the Delta Scuti type, that is, pulsating variables close the MSTO for the cluster age. Considering completeness and background contamination effects, we estimate the number of δ Sct belonging to the cluster between 40 and 60 members, although this number is based on the detection of a single δ Sct within the cluster half-light radius. This amount of variable stars at the MSTO level will not produce significant broadening of the MSTO, albeit higher-resolution imaging will be needed to rule out variable stars as a major contributor to the extended MSTO phenomenon. Though modest, this amount of δ Sct makes NGC 1846 the star cluster with the highest number of these variables ever discovered. Lastly, our results present a cautionary tale about the adequacy of shallow variability surveys in the LMC (like OGLE) to derive properties of its δ Sct population. 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 National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

  12. THE EFFECTS OF ROTATION ON THE MAIN-SEQUENCE TURNOFF OF INTERMEDIATE-AGE MASSIVE STAR CLUSTERS

    SciTech Connect

    Yang, Wuming; Bi, Shaolan; Liu, Zhie

    2013-10-20

    The double or extended main-sequence turnoffs (MSTOs) in the color-magnitude diagram (CMD) of intermediate-age massive star clusters in the Large Magellanic Cloud are generally interpreted as age spreads of a few hundred Myr. However, such age spreads do not exist in younger clusters (i.e., 40-300 Myr), which challenges this interpretation. The effects of rotation on the MSTOs of star clusters have been studied in previous works, but the results obtained are conflicting. Compared with previous works, we consider the effects of rotation on the main-sequence lifetime of stars. Our calculations show that rotating models have a fainter and redder MSTOmore » with respect to non-rotating counterparts with ages between about 0.8 and 2.2 Gyr, but have a brighter and bluer MSTO when age is larger than 2.4 Gyr. The spread of the MSTO caused by a typical rotation rate is equivalent to the effect of an age spread of about 200 Myr. Rotation could lead to the double or extended MSTOs in the CMD of the star clusters with ages between about 0.8 and 2.2 Gyr. However, the extension is not significant, and it does not even exist in younger clusters. If the efficiency of the mixing were high enough, the effects of the mixing would counteract the effect of the centrifugal support in the late stage of evolution, and the rotationally induced extension would disappear in the old intermediate-age star clusters, but younger clusters would have an extended MSTO. Moreover, the effects of rotation might aid in understanding the formation of some 'multiple populations' in globular clusters.« less

  13. Identification of main-sequence stars with mid-infrared excesses: Frequency of beta Pictoris analogs and transition disk systems

    NASA Astrophysics Data System (ADS)

    Uzpen, Brian Robert

    There is solid evidence of life on only one planet in the Universe: Earth. Since current technologies are not capable of directly observing planets, we must rely on secondary indicators, such as circumstellar disks to detect them. Circumstellar disks are commonplace around pre-main-sequence stars; it is believed these disks are a natural byproduct of star formation where planets can form. The general theoretical evolutionary sequence from the optically thick pre-main-sequence stars (T-Tauri and Herbig AeBe) to optically thin "debris disks", is as follows: After particles grow through condensation, they reach a critical value and form planetary cores; these cores accrete the gas around them and form planets. As the available circumstellar material decreases, the inner disk will develop a hole. Circumstellar material dissipates in the outer disk, while particles collide creating a population of grains that re-radiate stellar energy in the far-IR, a characteristic of debris disks. These debris disks represent a final stage of planet formation. Given that most stars originally have circumstellar disks, it is likely that planetary systems are common. Material similar in temperature to Earth emits primarily at ~10 mm (mid-IR wavelengths). By identifying stars with circumstellar material that emits in the mid-IR, it may be possible to locate Earth-like planetary systems; mid-IR excesses may also be an indicator of disks undergoing clearing processes with inner disk holes of a few AU. The purpose of this work is to identify and characterize a large sample of stellar sources with circumstellar disks that re-radiate energy at mid-IR wavelengths and place them in the greater context of disk evolution and planet formation. To achieve this goal, a large number of stellar sources with mid-IR excesses are identified through wide-area Galactic surveys. Far-IR photometry is utilized to confirm the mid-IR excess in a majority of the newly identified sources. Follow-up optical

  14. New clues to the cause of extended main-sequence turnoffs in intermediate-age star clusters in the Magellanic Clouds

    SciTech Connect

    Correnti, Matteo; Goudfrooij, Paul; Kalirai, Jason S.

    2014-10-01

    We use the Wide Field Camera 3 on board the Hubble Space Telescope (HST) to obtain deep, high-resolution images of two intermediate-age star clusters in the Large Magellanic Cloud of relatively low mass (≈10{sup 4} M {sub ☉}) and significantly different core radii, namely NGC 2209 and NGC 2249. For comparison purposes, we also reanalyzed archival HST images of NGC 1795 and IC 2146, two other relatively low-mass star clusters. From the comparison of the observed color-magnitude diagrams with Monte Carlo simulations, we find that the main-sequence turnoff (MSTO) regions in NGC 2209 and NGC 2249 are significantly wider thanmore » that derived from simulations of simple stellar populations, while those in NGC 1795 and IC 2146 are not. We determine the evolution of the clusters' masses and escape velocities from an age of 10 Myr to the present age. We find that differences among these clusters can be explained by dynamical evolution arguments if the currently extended clusters (NGC 2209 and IC 2146) experienced stronger levels of initial mass segregation than the currently compact ones (NGC 2249 and NGC 1795). Under this assumption, we find that NGC 2209 and NGC 2249 have estimated escape velocities, V {sub esc} ≳ 15 km s{sup –1} at an age of 10 Myr, large enough to retain material ejected by slow winds of first-generation stars, while the two clusters that do not feature extended MSTOs have V {sub esc} ≲ 12 km s{sup –1} at that age. These results suggest that the extended MSTO phenomenon can be better explained by a range of stellar ages rather than a range of stellar rotation velocities or interacting binaries.« less

  15. Deep Amino Acid Sequencing of Native Brain GABAA Receptors Using High-Resolution Mass Spectrometry*

    PubMed Central

    Chen, Zi-Wei; Fuchs, Karoline; Sieghart, Werner; Townsend, R. Reid; Evers, Alex S.

    2012-01-01

    Mass spectrometric sequencing of low abundance, integral membrane proteins, particularly the transmembrane domains, presents challenges that span the multiple phases of sample preparation including solubilization, purification, enzymatic digestion, peptide extraction, and chromatographic separation. We describe a method through which we have obtained high peptide coverage for 12 γ-aminobutyric acid type A receptor (GABAA receptor) subunits from 2 picomoles of affinity-purified GABAA receptors from rat brain neocortex. Focusing on the α1 subunit, we identified peptides covering 96% of the protein sequence from fragmentation spectra (MS2) using a database searching algorithm and deduced 80% of the amino acid residues in the protein from de novo sequencing of Orbitrap spectra. The workflow combined microscale membrane protein solubilization, protein delipidation, in-solution multi-enzyme digestion, multiple stationary phases for peptide extraction, and acquisition of high-resolution full scan and fragmentation spectra. For de novo sequencing of peptides containing the transmembrane domains, timed digestions with chymotrypsin were utilized to generate peptides with overlapping sequences that were then recovered by sequential solid phase extraction using a C4 followed by a porous graphitic carbon stationary phase. The specificity of peptide identifications and amino acid residue sequences was increased by high mass accuracy and charge state assignment to parent and fragment ions. Analysis of three separate brain samples demonstrated that 78% of the sequence of the α1 subunit was observed in all three replicates with an additional 13% covered in two of the three replicates, indicating a high degree of sequence coverage reproducibility. Label-free quantitative analysis was applied to the three replicates to determine the relative abundances of 11 γ-aminobutyric acid type A receptor subunits. The deep sequence MS data also revealed two N-glycosylation sites on the α1

  16. Can Two-Dimensional IR-ECD Mass Spectrometry Improve Peptide de Novo Sequencing?

    PubMed

    van Agthoven, Maria A; Lynch, Alice M; Morgan, Tomos E; Wootton, Christopher A; Lam, Yuko P Y; Chiron, Lionel; Barrow, Mark P; Delsuc, Marc-André; O'Connor, Peter B

    2018-03-06

    Two-dimensional mass spectrometry (2D MS) correlates precursor and fragment ions without ion isolation in a Fourier transform ion cyclotron resonance mass spectrometer (FTICR MS) for tandem mass spectrometry. Infrared activated electron capture dissociation (IR-ECD), using a hollow cathode configuration, generally yields more information for peptide sequencing in tandem mass spectrometry than ECD (electron capture dissociation) alone. The effects of the fragmentation zone on the 2D mass spectrum are investigated as well as the structural information that can be derived from it. The enhanced structural information gathered from the 2D mass spectrum is discussed in terms of how de novo peptide sequencing can be performed with increased confidence. 2D IR-ECD MS is shown to sequence peptides, to distinguish between leucine and isoleucine residues through the production of w ions as well as between C-terminal ( b/ c) and N-terminal ( y/ z) fragments through the use of higher harmonics, and to assign and locate peptide modifications.

  17. CAN WE PREDICT THE GLOBAL MAGNETIC TOPOLOGY OF A PRE-MAIN-SEQUENCE STAR FROM ITS POSITION IN THE HERTZSPRUNG-RUSSELL DIAGRAM?

    SciTech Connect

    Gregory, S. G.; Hillenbrand, L. A.; Donati, J.-F.

    2012-08-20

    Zeeman-Doppler imaging studies have shown that the magnetic fields of T Tauri stars can be significantly more complex than a simple dipole and can vary markedly between sources. We collect and summarize the magnetic field topology information obtained to date and present Hertzsprung-Russell (H-R) diagrams for the stars in the sample. Intriguingly, the large-scale field topology of a given pre-main-sequence (PMS) star is strongly dependent upon the stellar internal structure, with the strength of the dipole component of its multipolar magnetic field decaying rapidly with the development of a radiative core. Using the observational data as a basis, we arguemore » that the general characteristics of the global magnetic field of a PMS star can be determined from its position in the H-R diagram. Moving from hotter and more luminous to cooler and less luminous stars across the PMS of the H-R diagram, we present evidence for four distinct magnetic topology regimes. Stars with large radiative cores, empirically estimated to be those with a core mass in excess of {approx}40% of the stellar mass, host highly complex and dominantly non-axisymmetric magnetic fields, while those with smaller radiative cores host axisymmetric fields with field modes of higher order than the dipole dominant (typically, but not always, the octupole). Fully convective stars above {approx}> 0.5 M{sub Sun} appear to host dominantly axisymmetric fields with strong (kilo-Gauss) dipole components. Based on similarities between the magnetic properties of PMS stars and main-sequence M-dwarfs with similar internal structures, we speculate that a bistable dynamo process operates for lower mass stars ({approx}< 0.5 M{sub Sun} at an age of a few Myr) and that they will be found to host a variety of magnetic field topologies. If the magnetic topology trends across the H-R diagram are confirmed, they may provide a new method of constraining PMS stellar evolution models.« less

  18. Rotational and Candidate-Eclipsing-Binary Light Curves for Pre-Main-Sequence Stars in the Chamaeleon I Star-Forming Cloud

    NASA Astrophysics Data System (ADS)

    Lawson, Warrick A.; Crause, Lisa A.

    2009-04-01

    We present the results of a photometric survey for variability in ten X-ray-emitting low-mass stars in the Chamaeleon region. Eight of the stars we observed are bona fide pre-main-sequence members of the ~2 Myr-old Chamaeleon I star-forming cloud. The other two stars are young with high levels of relative X-ray emission, but with discordant proper motions they are probable non-members of the cloud. In six of the stars we monitored, periodic variations on timescales of 2.5-11.5 d were detected, that we ascribe to stellar rotation and the presence of cool starspots. Two other stars, CHXR 20 and CHXR 85, show large amplitude variations at visual and near-infrared wavelengths and are candidate eclipsing binaries. Compared to the rotational properties of low-mass stars in the ~8 Myr-old η Chamaeleontis cluster, we find that the older η Chamaeleontis stars have several times higher surface specific angular momentum than the younger Chamaeleon I stars. The apparent increase in angular momentum between ~2 and 8 Myr might be due to changes in stellar internal structure as the stars evolve, or evidence for a different rotational history between members of the two star-forming regions.

  19. Identification of staphylococcal species based on variations in protein sequences (mass spectrometry) and DNA sequence (sodA microarray).

    PubMed

    Kooken, Jennifer; Fox, Karen; Fox, Alvin; Altomare, Diego; Creek, Kim; Wunschel, David; Pajares-Merino, Sara; Martínez-Ballesteros, Ilargi; Garaizar, Javier; Oyarzabal, Omar; Samadpour, Mansour

    2014-02-01

    This report is among the first using sequence variation in newly discovered protein markers for staphylococcal (or indeed any other bacterial) speciation. Variation, at the DNA sequence level, in the sodA gene (commonly used for staphylococcal speciation) provided excellent correlation. Relatedness among strains was also assessed using protein profiling using microcapillary electrophoresis and pulsed field electrophoresis. A total of 64 strains were analyzed including reference strains representing the 11 staphylococcal species most commonly isolated from man (Staphylococcus aureus and 10 coagulase negative species [CoNS]). Matrix assisted time of flight ionization/ionization mass spectrometry (MALDI TOF MS) and liquid chromatography-electrospray ionization tandem mass spectrometry (LC ESI MS/MS) were used for peptide analysis of proteins isolated from gel bands. Comparison of experimental spectra of unknowns versus spectra of peptides derived from reference strains allowed bacterial identification after MALDI TOF MS analysis. After LC-MS/MS analysis of gel bands bacterial speciation was performed by comparing experimental spectra versus virtual spectra using the software X!Tandem. Finally LC-MS/MS was performed on whole proteomes and data analysis also employing X!tandem. Aconitate hydratase and oxoglutarate dehydrogenase served as marker proteins on focused analysis after gel separation. Alternatively on full proteomics analysis elongation factor Tu generally provided the highest confidence in staphylococcal speciation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Preserving the Sequence of a Biopolymer's Monomers as They Enter an Electrospray Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Maulbetsch, William; Wiener, Benjamin; Poole, William; Bush, Joseph; Stein, Derek

    2016-11-01

    This paper investigates how faithfully an electrospray mass spectrometer reports the order of monomers of a single biopolymer in the context of two sequencing strategies. We develop a simplified one-dimensional theoretical model of the dynamics of Brownian particles in the Taylor cone of an electropray source, where free monomers drift towards the apex in an elongational force gradient. The likelihood that neighboring particles will invert their order decreases near the apex because the strength of the force gradient increases. Neighboring monomers on a stretched biopolymer should be cleaved by photofragmentation within about 3 nm of the apex if they are to enter the mass spectrometer in sequence with 95% probability under typical experimental conditions. Alternatively, if the monomers are cleaved processively at milliseconds-long intervals by an enzyme, their sequence will be faithfully reported with 95% confidence if the enzyme is within about 117 nm of the apex.

  1. [Mass spectrometry identification of secreted proteins from Bacillus firmus and analysis of its secretive sequences].

    PubMed

    Liu, Sun; Song, Xiaoling; Huang, Jie

    2011-07-01

    Bacillus firmus was a common probiotics bacteria in nature and widely used in the shrimp aquaculture. In order to construct expression vectors for secretive proteins, we identified several major secretive proteins of Bacillus firmus by mass spectrometry and analyzed their gene sequences to find signal peptide sequences. The secreted proteins of Bacillus firmus were extracted and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The 3 highly expressed protein bands in the SDS-PAGE were identified by mass spectrometry Matrix Assisted Laser Desorption Ionization (MALDI)-Time of Flight (TOF)/Time of Flight (TOF) and the sequences were downloaded from National Center for Biotechnology Information (NCBI) database. Then Polymerase Chain Reaction (PCR) primers were designed according to the downloaded sequences and specific DNA bands were amplified sequenced and bioinformatics analyzed. The proteins were identified as the putative chitinase, enterotoxin A and protein BCG9842 of Bacillus firmus. Three signal peptides were conformed by using the online software SignaIP 3.0, namely bf-43, bf-37 and bf-16. The cellular localization of the secreted sequences were analyzed by PSORT. And we found that bf-43 located in the outer membrane of cells, bf-37 and bf-16 located in the extracellular cell. 3 major secreted proteins of Bacillus firmus have been identified. 3 possible signal peptides were obtained and will be useful for the construction of expression vectors for secretive proteins.

  2. The evolution of surface magnetic fields in young solar-type stars II: the early main sequence (250-650 Myr)

    NASA Astrophysics Data System (ADS)

    Folsom, C. P.; Bouvier, J.; Petit, P.; Lèbre, A.; Amard, L.; Palacios, A.; Morin, J.; Donati, J.-F.; Vidotto, A. A.

    2018-03-01

    There is a large change in surface rotation rates of sun-like stars on the pre-main sequence and early main sequence. Since these stars have dynamo-driven magnetic fields, this implies a strong evolution of their magnetic properties over this time period. The spin-down of these stars is controlled by interactions between stellar and magnetic fields, thus magnetic evolution in turn plays an important role in rotational evolution. We present here the second part of a study investigating the evolution of large-scale surface magnetic fields in this critical time period. We observed stars in open clusters and stellar associations with known ages between 120 and 650 Myr, and used spectropolarimetry and Zeeman Doppler Imaging to characterize their large-scale magnetic field strength and geometry. We report 15 stars with magnetic detections here. These stars have masses from 0.8 to 0.95 M⊙, rotation periods from 0.326 to 10.6 d, and we find large-scale magnetic field strengths from 8.5 to 195 G with a wide range of geometries. We find a clear trend towards decreasing magnetic field strength with age, and a power law decrease in magnetic field strength with Rossby number. There is some tentative evidence for saturation of the large-scale magnetic field strength at Rossby numbers below 0.1, although the saturation point is not yet well defined. Comparing to younger classical T Tauri stars, we support the hypothesis that differences in internal structure produce large differences in observed magnetic fields, however for weak-lined T Tauri stars this is less clear.

  3. Planetary Construction Zones in Occultation: Eclipses by Circumsecondary and Circumplanetary Disks and a Candidate Eclipse of a Pre-Main Sequence Star in Sco-Cen

    NASA Astrophysics Data System (ADS)

    Mamajek, Eric E.; Quillen, A. C.; Pecaut, M.; Moolekamp, F.; Scott, E. L.; Kenworthy, M. A.; Collier Cameron, A.; Parley, N.

    2012-01-01

    The large relative sizes of circumplanetary and circumstellar disks imply that they might be seen in eclipse in stellar light curves. We present photometric and spectroscopic data for a complex disk eclipse of a post-accretion, solar-mass pre-main sequence star. The star 1SWASP J140747.93-394542.6 is a 16 Myr-old member of the Upper Centaurus-Lupus subgroup of Sco-Cen at 130 pc, and was discovered in a spectroscopic survey for new low-mass Sco-Cen members by Pecaut & Mamajek. SuperWASP and ASAS V-band time series photometry reveal that this star exhibited a remarkably long, deep, and complex eclipse event in April 2007. At least 5 multi-day dimming events of >0.5 mag are identified, with an asymmetric >3.3 mag deep eclipse bracketed by two pairs of 1 mag eclipses symmetrically occurring +-12 days and +-26 days before and after. We place a firm lower limit on the period of the eclipser of 850 days. We hypothesize that this star is being eclipsed by a low-mass object with an orbiting dust disk with significant radial substructure ("rings" and gaps) and mass on the order of lunar masses. Combining theoretical predictions of the sizes and masses of circumplanetary disks around young gas giants with observational constraints on the incidence of such planets, shows that their eclipses should be of sufficient optical depth and duration to be plausibly detectable, albeit extraordinarily rarely. LSST surveys of post-accretion stars ( 10 Myr) should yield disk eclipses around at least 10-4 of the stars. Eclipses by circumplanetary and circumsecondary disks will provide us fine-scale observational constraints on the physical and chemical conditions of the dust and gas which spawn satellite systems around gas giant planets and planetary systems around stars. This research was supported by NSF grant AST-1008908 and funds from the School of Arts and Sciences at the University of Rochester.

  4. The properties and environment of primitive solar nebulae as deduced from observations of solar-type pre-main sequence stars

    NASA Technical Reports Server (NTRS)

    Strom, Stephen E.; Edwards, Suzan; Strom, Karen M.

    1991-01-01

    The following topics were discussed: (1) current observation evidence for the presence of circumstellar disks associated with solar type pre-main sequence (PMS) stars; (2) the properties of such disks; and (3) the disk environment.

  5. Using A New Model for Main Sequence Turnoff Absolute Magnitudes to Measure Stellar Streams in the Milky Way Halo

    NASA Astrophysics Data System (ADS)

    Weiss, Jake; Newberg, Heidi Jo; Arsenault, Matthew; Bechtel, Torrin; Desell, Travis; Newby, Matthew; Thompson, Jeffery M.

    2016-01-01

    Statistical photometric parallax is a method for using the distribution of absolute magnitudes of stellar tracers to statistically recover the underlying density distribution of these tracers. In previous work, statistical photometric parallax was used to trace the Sagittarius Dwarf tidal stream, the so-called bifurcated piece of the Sagittaritus stream, and the Virgo Overdensity through the Milky Way. We use an improved knowledge of this distribution in a new algorithm that accounts for the changes in the stellar population of color-selected stars near the photometric limit of the Sloan Digital Sky Survey (SDSS). Although we select bluer main sequence turnoff stars (MSTO) as tracers, large color errors near the survey limit cause many stars to be scattered out of our selection box and many fainter, redder stars to be scattered into our selection box. We show that we are able to recover parameters for analogues of these streams in simulated data using a maximum likelihood optimization on MilkyWay@home. We also present the preliminary results of fitting the density distribution of major Milky Way tidal streams in SDSS data. This research is supported by generous gifts from the Marvin Clan, Babette Josephs, Manit Limlamai, and the MilkyWay@home volunteers.

  6. THE OVERLOOKED ROLE OF STELLAR VARIABILITY IN THE EXTENDED MAIN SEQUENCE OF LMC INTERMEDIATE-AGE CLUSTERS

    SciTech Connect

    Salinas, R.; Pajkos, M. A.; Strader, J.

    2016-11-20

    Intermediate-age star clusters in the Large Magellanic Cloud show extended main sequence turnoffs (MSTOs) that are not consistent with a canonical single stellar population. These broad turnoffs have been interpreted as evidence for extended star formation and/or stellar rotation. Since most of these studies use single frames per filter to do the photometry, the presence of variable stars near the MSTO in these clusters has remained unnoticed and their impact has been totally ignored. We model the influence of Delta Scuti using synthetic CMDs, adding variable stars following different levels of incidence and amplitude distributions. We show that Delta Scutimore » observed at a single phase will produce a broadening of the MSTO without affecting other areas of a CMD such as the upper MS or the red clump; furthermore, the amount of spread introduced correlates with cluster age, as observed. This broadening is constrained to ages ∼1–3 Gyr when the MSTO area crosses the instability strip, which is also consistent with observations. Variable stars cannot explain bifurcarted MSTOs or the extended MSTOs seen in some young clusters, but they can make an important contribution to the extended MSTOs in intermediate-age clusters.« less

  7. Chemically-dissected Rotation Curves of the Galactic Bulge from Hubble Space Telescope Proper Motions on the Main Sequence

    NASA Astrophysics Data System (ADS)

    Clarkson, William I.; Calamida, Annalisa; Sahu, Kailash C.; Gennaro, Mario; Brown, Thomas M.; Avila, Roberto J.; Rich, R. Michael; Debattista, Victor P.

    2018-01-01

    We report results from a pilot study using archival Hubble Space Telescope imaging observations in seven filters over a multi-year time-baseline to probe the co-dependence of chemical abundance and kinematics, using proper motion-based rotation curves selected on relative metallicity. With spectroscopic studies suggesting the metallicity distribution of the Bulge may be bimodal, we follow a data-driven approach to classify stars as belonging to metal-rich or metal-poor ends of the observed relative photometric metallicity distribution, with classification implemented using standard unsupervised learning techniques. We detect clear differences in both slope and amplitude of the proper motion-based rotation curve as traced by the more “metal-rich” and “metal-poor” samples. The sense of the discrepancy is qualitatively in agreement both with recent observational and theoretical indications; the “metal-poor” sample does indeed show a weaker rotation signature.This is the first study to dissect the proper motion rotation curve of the Bulge by chemical abundance using main-sequence targets, which are orders of magnitude more common on the sky than bright giants. These techniques thus offer a pencil-beam complement to wide-field studies that use more traditional tracer populations.

  8. Rates and delay times of Type Ia supernovae in the helium-enriched main-sequence donor scenario

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Wei; Stancliffe, Richard J.

    2018-04-01

    The nature of the progenitors of Type Ia supernovae (SNe Ia) remains a mystery. Comparing theoretical rates and delay-time distributions of SNe Ia with those inferred observationally can constrain their progenitor models. In this work, taking thermohaline mixing into account in the helium-enriched main-sequence (HEMS) donor scenario, we address rates and delay times of SNe Ia in this channel by combining the results of self-consistent binary evolution calculations with population synthesis models. We find that the Galactic SN Ia rate from the HEMS donor scenario is around 0.6-1.2 × 10-3 yr-1, which is about 30 per cent of the observed rate. Delay times of SNe Ia in this scenario cover a wide range of 0.1-1.0 Gyr. We also present the pre-explosion properties of companion stars in the HEMS donor scenario, which will be helpful for placing constraints on SN Ia progenitors through analysing their pre-explosion images.

  9. First discovery of a magnetic field in a main-sequence δ Scuti star: the Kepler star HD 188774

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Lampens, P.

    2015-11-01

    The Kepler space mission provided a wealth of δ Sct-γ Dor hybrid candidates. While some may be genuine hybrids, others might be misclassified due to the presence of a binary companion or to rotational modulation caused by magnetism and related surface inhomogeneities. In particular, the Kepler δ Sct-γ Dor hybrid candidate HD 188774 shows a few low frequencies in its light and radial velocity curves, whose origin is unclear. In this work, we check for the presence of a magnetic field in HD 188774. We obtained two spectropolarimetric measurements with an Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) at Canada-France-Hawaii Telescope. The data were analysed with the least-squares deconvolution (LSD) method. We detected a clear magnetic signature in the Stokes V LSD profiles. The origin of the low frequencies detected in HD 188774 is therefore most probably the rotational modulation of surface spots possibly related to the presence of a magnetic field. Consequently, HD 188774 is not a genuine hybrid δ Sct-γ Dor star, but the first known magnetic main-sequence δ Sct star. This makes it a prime target for future asteroseismic and spot modelling. This result casts new light on the interpretation of the Kepler results for other δ Sct-γ Dor hybrid candidates.

  10. GOODS-Herschel: Star Formation, Dust Attenuation, and the FIR-radio Correlation on the Main Sequence of Star-forming Galaxies up to z ≃4

    NASA Astrophysics Data System (ADS)

    Pannella, M.; Elbaz, D.; Daddi, E.; Dickinson, M.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Buat, V.; Charmandaris, V.; Cibinel, A.; Juneau, S.; Ivison, R. J.; Le Borgne, D.; Le Floc'h, E.; Leiton, R.; Lin, L.; Magdis, G.; Morrison, G. E.; Mullaney, J.; Onodera, M.; Renzini, A.; Salim, S.; Sargent, M. T.; Scott, D.; Shu, X.; Wang, T.

    2015-07-01

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate-M* correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR-radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5-4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts. Based on observations collected at the Herschel, Spitzer, Keck, NRAO-VLA, Subaru, KPNO, and CFHT observatories. Herschel is an European Space Agency Cornerstone Mission with science instruments provided by European-led Principal Investigator consortia and

  11. Multilocus sequence typing of Streptococcus pneumoniae by use of mass spectrometry.

    PubMed

    Dunne, Eileen M; Ong, Eng Kok; Moser, Ralf J; Siba, Peter M; Phuanukoonnon, Suparat; Greenhill, Andrew R; Robins-Browne, Roy M; Mulholland, E Kim; Satzke, Catherine

    2011-11-01

    Multilocus sequence typing (MLST) is an important tool for the global surveillance of bacterial pathogens that is performed by comparing the sequences of designated housekeeping genes. We developed and tested a novel mass spectrometry-based method for MLST of Streptococcus pneumoniae. PCR amplicons were subjected to in vitro transcription and base-specific cleavage, followed by analysis of the resultant fragments by using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Comparison of the cleavage fragment peak patterns to a reference sequence set permitted automated identification of alleles. Validation experiments using 29 isolates of S. pneumoniae revealed that the results of MALDI-TOF MS MLST matched those obtained by traditional sequence-based MLST for 99% of alleles and that the MALDI-TOF MS method accurately identified two single-nucleotide variations. The MADLI-TOF MS method was then used for MLST analysis of 43 S. pneumoniae isolates from Papua New Guinean children. The majority of the isolates present in this population were not clonal and contained seven new alleles and 30 previously unreported sequence types.

  12. Polarimetric Variations of Binary Stars. IV. Pre-Main-Sequence Spectroscopic Binaries Located in Taurus, Auriga, and Orion

    NASA Astrophysics Data System (ADS)

    Manset, N.; Bastien, P.

    2002-08-01

    We present polarimetric observations of 14 pre-main-sequence (PMS) binaries located in the Taurus, Auriga, and Orion star-forming regions. The majority of the average observed polarizations are below 0.5%, and none are above 0.9%. After removal of estimates of the interstellar polarization, about half the binaries have an intrinsic polarization above 0.5%, even though most of them do not present other evidences for the presence of circumstellar dust. Various tests reveal that 77% of the PMS binaries have or possibly have a variable polarization. LkCa 3, Par 1540, and Par 2494 present detectable periodic and phase-locked variations. The periodic polarimetric variations are noisier and of a lesser amplitude (~0.1%) than for other types of binaries, such as hot stars. This could be due to stochastic events that produce deviations in the average polarization, a nonfavorable geometry (circumbinary envelope), or the nature of the scatterers (dust grains are less efficient polarizers than electrons). Par 1540 is a weak-line T Tauri star but nonetheless has enough dust in its environment to produce detectable levels of polarization and variations. A fourth interesting case is W134, which displays rapid changes in polarization that could be due to eclipses. We compare the observations with some of our numerical simulations and also show that an analysis of the periodic polarimetric variations with the Brown, McLean, & Emslie (BME) formalism to find the orbital inclination is for the moment premature: nonperiodic events introduce stochastic noise that partially masks the periodic low-amplitude variations and prevents the BME formalism from finding a reasonable estimate of the orbital inclination.

  13. Double-ramp on the Main Himalayan Thrust revealed by broadband waveform modeling of the 2015 Gorkha earthquake sequence

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Wei, Shengji; Wu, Wenbo

    2017-09-01

    The 2015Mw 7.8 Gorkha earthquake sequence that unzipped the lower edge of the Main Himalayan Thrust (MHT) in central Nepal provides an exceptional opportunity to understand the fault geometry in this region. However, the limited number of focal mechanisms and the poor horizontal locations and depths of earthquakes in the global catalog impede us from clearly imaging the ruptured MHT. In this study, we generalized the Amplitude Amplification Factor (AAF) method to teleseismic distance that allows us to model the teleseismic P-waves up to 1.5 Hz. We used well-constrained medium-sized earthquakes to establish AAF corrections for teleseismic stations that were later used to invert the high-frequency waveforms of other nearby events. This new approach enables us to invert the focal mechanisms of some early aftershocks, which is challenging by using other long-period methods. With this method, we obtained 12 focal mechanisms more than that in the GCMT catalog. We also modeled the high-frequency teleseismic P-waves and the surface reflection phases (pP and sP) to precisely constrain the depths of the earthquakes. Our results indicate that the uncertainty of the depth estimation is as small as 1-2 km. Finally, we refined the horizontal locations of these aftershocks using carefully hand-picked arrivals. The refined aftershock mechanisms and locations delineate a clear double-ramp geometry of the MHT, with an almost flat décollement sandwiched in between. The flat (dip ∼7 degrees) portion of the MHT is consistent with the coseismic rupture of the mainshock, which has a well-constrained slip distribution. The fault morphology suggests that the ramps, both along the up-dip and down-dip directions, play a significant role in stopping the rupture of the 2015 Gorkha earthquake. Our method can be applied to general subduction zone earthquakes and fault geometry studies.

  14. The pre-main-sequence star V1184 Tauri (CB 34V) at the end of prolonged eclipse

    NASA Astrophysics Data System (ADS)

    Semkov, E. H.; Peneva, S. P.; Ibryamov, S. I.

    2015-10-01

    Aims: V1184 Tau (CB 34V) lies in the field of the Bok globule CB 34 and was discovered as a large amplitude variable in 1993. According to the first hypothesis of the variability of the star, it is a FU Orionis candidate erupted between 1951 and 1993. During subsequent observations, the star manifests large amplitude variability interpreted as obscuration from circumstellar clouds of dust. We included V1184 Tau (CB 34V) in our target list of highly variable pre-main-sequence stars to determine the reasons for the variations in the brightness of this object. Methods: Data from BVRI photometric observations of the young stellar object V1184 Tau, obtained in the period 2008-2015, are presented in the paper. These data are a continuation of our optical photometric monitoring of the star began in 2000 and continuing to date. The photometric observations of V1184 Tau were performed in two observatories with two medium-sized and two small telescopes. Results: Our results indicate that during periods of maximum light the star shows characteristics typical of T Tauri stars. During the observed deep minimum in brightness, however, V1184 Tau is rather similar to UX Orionis objects. The deep drop in brightness began in 2003 ended in 2015 as the star has returned to maximum light. The light curve during the drop is obviously asymmetric as the decrease in brightness lasts two times longer than the rise. The observed colour reverse on the colour-magnitude diagrams is also confirmation of obscuration from circumstellar clouds of dust as a reason for the large amplitude variability in the brightness. Appendix A is available in electronic form at http://www.aanda.org

  15. The Problem of Hipparcos Distances to Open Clusters. Report 1; Constraints from Multicolor a Main-Sequence Fitting

    NASA Technical Reports Server (NTRS)

    Pinsonneault, Marc H.; Stauffer, John; Soderblom, David R.; King, Jeremy R.; Hanson, Robert B.

    1998-01-01

    Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main-sequence (MS) fitting. There are surprising differences between the two distance measurements. indicating either the need for changes in the cluster compositions or reddening, underlying problems with the technique of MS fitting, or systematic errors in the Hipparcos parallaxes at the 1 mas level. We examine the different possibilities, focusing on MS fitting in both metallicity-sensitive B-V and metallicity-insensitive V-I for five well-studied systems (the Hyades, Pleiades, alpha Per, Praesepe, and Coma Ber). The Hipparcos distances to the Hyades and alpha Per are within 1 sigma of the MS-fitting distance in B-V and V-I, while the Hipparcos distances to Coma Ber and the Pleiades are in disagreement with the MS-fitting distance at more than the 3 sigma level. There are two Hipparcos measurements of the distance to Praesepe; one is in good agreement with the MS-fitting distance and the other disagrees at the 2 sigma level. The distance estimates from the different colors are in conflict with one another for Coma but in agreement for the Pleiades. Changes in the relative cluster metal abundances, age related effects, helium, and reddening are shown to be unlikely to explain the puzzling behavior of the Pleiades. We present evidence for spatially dependent systematic errors at the 1 mas level in the parallaxes of Pleiades stars. The implications of this result are discussed.

  16. Effects of temperature and mass conservation on the typical chemical sequences of hydrogen oxidation.

    PubMed

    Nicholson, Schuyler B; Alaghemandi, Mohammad; Green, Jason R

    2018-01-28

    Macroscopic properties of reacting mixtures are necessary to design synthetic strategies, determine yield, and improve the energy and atom efficiency of many chemical processes. The set of time-ordered sequences of chemical species are one representation of the evolution from reactants to products. However, only a fraction of the possible sequences is typical, having the majority of the joint probability and characterizing the succession of chemical nonequilibrium states. Here, we extend a variational measure of typicality and apply it to atomistic simulations of a model for hydrogen oxidation over a range of temperatures. We demonstrate an information-theoretic methodology to identify typical sequences under the constraints of mass conservation. Including these constraints leads to an improved ability to learn the chemical sequence mechanism from experimentally accessible data. From these typical sequences, we show that two quantities defining the variational typical set of sequences-the joint entropy rate and the topological entropy rate-increase linearly with temperature. These results suggest that, away from explosion limits, data over a narrow range of thermodynamic parameters could be sufficient to extrapolate these typical features of combustion chemistry to other conditions.

  17. Method and apparatus for enhanced sequencing of complex molecules using surface-induced dissociation in conjunction with mass spectrometric analysis

    DOEpatents

    Laskin, Julia [Richland, WA; Futrell, Jean H [Richland, WA

    2008-04-29

    The invention relates to a method and apparatus for enhanced sequencing of complex molecules using surface-induced dissociation (SID) in conjunction with mass spectrometric analysis. Results demonstrate formation of a wide distribution of structure-specific fragments having wide sequence coverage useful for sequencing and identifying the complex molecules.

  18. A NEW METHOD FOR THE ASSESSMENT OF AGE AND AGE SPREAD OF PRE-MAIN-SEQUENCE STARS IN YOUNG STELLAR ASSOCIATIONS OF THE MAGELLANIC CLOUDS

    SciTech Connect

    Da Rio, Nicola; Gennaro, Mario; Gouliermis, Dimitrios A., E-mail: dario@mpia-hd.mpg.d, E-mail: dgoulier@mpia-hd.mpg.d, E-mail: gennaro@mpia-hd.mpg.d

    2010-11-01

    We present a new method for the evaluation of the age and age spread among pre-main-sequence (PMS) stars in star-forming regions in the Magellanic Clouds, accounting simultaneously for photometric errors, unresolved binarity, differential extinction, stellar variability, accretion, and crowding. The application of the method is performed with the statistical construction of synthetic color-magnitude diagrams (CMDs) using isochrones from two families of PMS evolutionary models. We convert each isochrone into two-dimensional probability distributions of artificial PMS stars in the CMD by applying the aforementioned biases that dislocate these stars from their original CMD positions. A maximum-likelihood technique is then applied tomore » derive the probability for each observed star to have a certain age as well as the best age for the entire cluster. We apply our method to the photometric catalog of {approx}2000 PMS stars in the young association LH 95 in the Large Magellanic Cloud, based on the deepest HST/ACS imaging ever performed toward this galaxy, with a detection limit of V {approx} 28, corresponding to M {approx} 0.2 M o-dot. We assume the initial mass function and reddening distribution for the system, as they have been previously derived by us. Our treatment shows that the age determination is very sensitive to the considered grid of evolutionary models and the assumed binary fraction. The age of LH 95 is found to vary from 2.8 Myr to 4.4 Myr, depending on these factors. We evaluate the accuracy of our age estimation and find that the method is fairly accurate in the PMS regime, while the precision of the measurement of the age is lower at higher luminosities. Our analysis allows us to disentangle a real age spread from the apparent CMD broadening caused by the physical and observational biases. We find that LH 95 hosts an age spread that is represented well by a Gaussian distribution with an FWHM of the order of 2.8-4.4 Myr depending on the model and

  19. CycLS: Accurate, whole-library sequencing of cyclic peptides using tandem mass spectrometry.

    PubMed

    Townsend, Chad; Furukawa, Akihiro; Schwochert, Joshua; Pye, Cameron R; Edmondson, Quinn; Lokey, R Scott

    2018-03-15

    Cyclic peptides are of great interest as therapeutic compounds due to their potential for specificity and intracellular activity, but specific compounds can be difficult to identify from large libraries without resorting to molecular encoding techniques. Large libraries of cyclic peptides are often DNA-encoded or linearized before sequencing, but both of those deconvolution strategies constrain the chemistry, assays, and quantification methods which can be used. We developed an automated sequencing program, CycLS, to identify cyclic peptides contained within large synthetic libraries. CycLS facilitates quick and easy identification of all library-members via tandem mass spectrometry data without requiring any specific chemical moieties or modifications within the library. Validation of CycLS against a library of 400 cyclic hexapeptide peptoid hybrids (peptomers) of unique mass yielded a result of 95% accuracy when compared against a simulated library size of 234,256 compounds. CycLS was also evaluated by resynthesizing pure compounds from a separate 1800-member library of cyclic hexapeptides and hexapeptomers with high mass redundancy. Of 22 peptides resynthesized, 17 recapitulated the retention times and fragmentation patterns assigned to them from the whole-library bulk assay results. Implementing a database-matching approach, CycLS is fast and provides a robust method for sequencing cyclic peptides that is particularly applicable to the deconvolution of synthetic libraries. Copyright © 2018 Elsevier Ltd. All rights reserved.

  20. Sequence microheterogeneity of parvalbumin pI 5.0 of pike: a mass spectrometric study.

    PubMed

    Permyakov, Sergei E; Karnoup, Anton S; Bakunts, Anush G; Permyakov, Eugene A

    2009-01-01

    Parvalbumin (PA) is a muscle and neuronal calcium-binding protein, the major fish and frog allergen. Its characteristic feature is the presence of multiple isoforms with significantly different amino acid sequences. Here we show that the major isoform of northern pike muscle PA (pI 5.0, alpha-PA) exhibits microheterogeneity of amino acid sequence. ESI Q-TOF mass-spectrometry (MS) analysis of alpha-PA sample showed the presence of two components with mass difference of 71 Da. Analysis of tryptic and endoproteinase Asp-N digests of alpha-PA by MALDI-TOF MS revealed peptides, corresponding to two different amino acid sequences. The sequence differences between variant proteins are limited to AB-domain and include substitutions K27A and L31K, and an extra Leu residue between K11 and K12. Since the affected residues comprise a cluster on the surface of PA, an involvement of the identified region into target recognition is suggested. The substitutions at positions 27 and 31 are located in the region of previously identified epitopes of parvalbumin relevant for PA-specific IgE and IgG binding, which suggests different immunoactivities of the variants. The found microheterogeneity of PA is suggested to be of importance for physiological adaptation of the propulsive musculature to developmental and/or environmental requirements and may contribute to PA allergenicity.

  1. Zodiacal Exoplanets in Time (ZEIT). III. A Short-period Planet Orbiting a Pre-main-sequence Star in the Upper Scorpius OB Association

    NASA Astrophysics Data System (ADS)

    Mann, Andrew W.; Newton, Elisabeth R.; Rizzuto, Aaron C.; Irwin, Jonathan; Feiden, Gregory A.; Gaidos, Eric; Mace, Gregory N.; Kraus, Adam L.; James, David J.; Ansdell, Megan; Charbonneau, David; Covey, Kevin R.; Ireland, Michael J.; Jaffe, Daniel T.; Johnson, Marshall C.; Kidder, Benjamin; Vanderburg, Andrew

    2016-09-01

    We confirm and characterize a close-in ({P}{{orb}} = 5.425 days), super-Neptune sized ({5.04}-0.37+0.34 {R}\\oplus ) planet transiting K2-33 (2MASS J16101473-1919095), a late-type (M3) pre-main-sequence (11 Myr old) star in the Upper Scorpius subgroup of the Scorpius-Centaurus OB association. The host star has the kinematics of a member of the Upper Scorpius OB association, and its spectrum contains lithium absorption, an unambiguous sign of youth (\\lt 20 Myr) in late-type dwarfs. We combine photometry from K2 and the ground-based MEarth project to refine the planet’s properties and constrain the host star’s density. We determine K2-33’s bolometric flux and effective temperature from moderate-resolution spectra. By utilizing isochrones that include the effects of magnetic fields, we derive a precise radius (6%-7%) and mass (16%) for the host star, and a stellar age consistent with the established value for Upper Scorpius. Follow-up high-resolution imaging and Doppler spectroscopy confirm that the transiting object is not a stellar companion or a background eclipsing binary blended with the target. The shape of the transit, the constancy of the transit depth and periodicity over 1.5 yr, and the independence with wavelength rule out stellar variability or a dust cloud or debris disk partially occulting the star as the source of the signal; we conclude that it must instead be planetary in origin. The existence of K2-33b suggests that close-in planets can form in situ or migrate within ˜10 Myr, e.g., via interactions with a disk, and that long-timescale dynamical migration such as by Lidov-Kozai or planet-planet scattering is not responsible for all short-period planets.

  2. Polarimetric Variations of Binary Stars. V. Pre-Main-Sequence Spectroscopic Binaries Located in Ophiuchus and Scorpius

    NASA Astrophysics Data System (ADS)

    Manset, N.; Bastien, P.

    2003-06-01

    We present polarimetric observations of seven pre-main-sequence (PMS) spectroscopic binaries located in the ρ Ophiuchus and Upper Scorpius star-forming regions (SFRs). The average observed polarizations at 7660 Å are between 0.5% and 3.5%. After estimates of the interstellar polarization are removed, all binaries have an intrinsic polarization above 0.4%, even though most of them do not present other evidences for circumstellar dust. Two binaries, NTTS 162814-2427 and NTTS 162819-2423S, present high levels of intrinsic polarization between 1.5% and 2.1%, in agreement with the fact that other observations (photometry, spectroscopy) indicate the presence of circumstellar dust. Tests reveal that all seven PMS binaries have a statistically variable or possibly variable polarization. Combining these results with our previous sample of binaries located in the Taurus, Auriga, and Orion SFRs, 68% of the binaries have an intrinsic polarization above 0.5%, and 90% of the binaries are polarimetrically variable or possibly variable. NTTS 160814-1857, 162814-2427, and 162819-2423S are clearly polarimetrically variable. The first two also exhibit phase-locked variations over ~10 and ~40 orbits, respectively. Statistically, NTTS 160905-1859 is possibly variable, but it shows periodic variations not detected by the statistical tests; those variations are not phased locked and only present for short intervals of time. The amplitudes of the variations reach a few tenths of a percent, greater than for the previously studied PMS binaries located in the Taurus, Orion, and Auriga SFRs. The high-eccentricity system NTTS 162814-2427 shows single-periodic variations, in agreement with our previous numerical simulations. We compare the observations with some of our numerical simulations and also show that an analysis of the periodic polarimetric variations with the Brown, McLean, & Emslie (BME) formalism to find the orbital inclination is for the moment premature: nonperiodic events

  3. CONSTRAINING THE EXOZODIACAL LUMINOSITY FUNCTION OF MAIN-SEQUENCE STARS: COMPLETE RESULTS FROM THE KECK NULLER MID-INFRARED SURVEYS

    SciTech Connect

    Mennesson, B.; Serabyn, E.; Colavita, M. M.

    2014-12-20

    Forty-seven nearby main-sequence stars were surveyed with the Keck Interferometer mid-infrared Nulling instrument (KIN) between 2008 and 2011, searching for faint resolved emission from exozodiacal dust. Observations of a subset of the sample have already been reported, focusing essentially on stars with no previously known dust. Here we extend this previous analysis to the whole KIN sample, including 22 more stars with known near- and/or far-infrared excesses. In addition to an analysis similar to that of the first paper of this series, which was restricted to the 8-9 μm spectral region, we present measurements obtained in all 10 spectral channelsmore » covering the 8-13 μm instrumental bandwidth. Based on the 8-9 μm data alone, which provide the highest signal-to-noise measurements, only one star shows a large excess imputable to dust emission (η Crv), while four more show a significant (>3σ) excess: β Leo, β UMa, ζ Lep, and γ Oph. Overall, excesses detected by KIN are more frequent around A-type stars than later spectral types. A statistical analysis of the measurements further indicates that stars with known far-infrared (λ ≥ 70 μm) excesses have higher exozodiacal emission levels than stars with no previous indication of a cold outer disk. This statistical trend is observed regardless of spectral type and points to a dynamical connection between the inner (zodi-like) and outer (Kuiper-Belt-like) dust populations. The measured levels for such stars are clustering close to the KIN detection limit of a few hundred zodis and are indeed consistent with those expected from a population of dust that migrated in from the outer belt by Poynting-Robertson drag. Conversely, no significant mid-infrared excess is found around sources with previously reported near-infrared resolved excesses, which typically have levels of the order of 1% over the photospheric flux. If dust emission is really at play in these near-infrared detections, the absence of a strong

  4. Revisiting the pre-main-sequence evolution of stars. I. Importance of accretion efficiency and deuterium abundance

    NASA Astrophysics Data System (ADS)

    Kunitomo, Masanobu; Guillot, Tristan; Takeuchi, Taku; Ida, Shigeru

    2017-03-01

    Context. Protostars grow from the first formation of a small seed and subsequent accretion of material. Recent theoretical work has shown that the pre-main-sequence (PMS) evolution of stars is much more complex than previously envisioned. Instead of the traditional steady, one-dimensional solution, accretion may be episodic and not necessarily symmetrical, thereby affecting the energy deposited inside the star and its interior structure. Aims: Given this new framework, we want to understand what controls the evolution of accreting stars. Methods: We use the MESA stellar evolution code with various sets of conditions. In particular, we account for the (unknown) efficiency of accretion in burying gravitational energy into the protostar through a parameter, ξ, and we vary the amount of deuterium present. Results: We confirm the findings of previous works that, in terms of evolutionary tracks on an Hertzprung-Russell (H-R) diagram, the evolution changes significantly with the amount of energy that is lost during accretion. We find that deuterium burning also regulates the PMS evolution. In the low-entropy accretion scenario, the evolutionary tracks in the H-R diagram are significantly different from the classical tracks and are sensitive to the deuterium content. A comparison of theoretical evolutionary tracks and observations allows us to exclude some cold accretion models (ξ 0) with low deuterium abundances. Conclusions: We confirm that the luminosity spread seen in clusters can be explained by models with a somewhat inefficient injection of accretion heat. The resulting evolutionary tracks then become sensitive to the accretion heat efficiency, initial core entropy, and deuterium content. In this context, we predict that clusters with a higher D/H ratio should have less scatter in luminosity than clusters with a smaller D/H. Future work on this issue should include radiation-hydrodynamic simulations to determine the efficiency of accretion heating and further

  5. The Quenched Mass Portion of Star-forming Galaxies and the Origin of the Star Formation Sequence Slope

    NASA Astrophysics Data System (ADS)

    Pan, Zhizheng; Zheng, Xianzhong; Kong, Xu

    2017-01-01

    Observationally, a massive disk galaxy can harbor a bulge component that is comparably inactive as a quiescent galaxy. It has been speculated that the quenched component contained in star-forming galaxies (SFGs) is the reason why the star formation main sequence (MS) has a shallow slope at high masses. In this paper, we present a toy model to quantify the quenched mass portion of SFGs (fQ) at fixed stellar mass (M*) and to reconcile the MS slopes in both the low- and the high-mass regimes. In this model, each SFG is composed of a star-forming plus a quenched component. The mass of the star-forming component (MSF) correlates with the star formation rate (SFR) following a relation SFR \\propto {M}{SF}{α {SF}}, where αSF ˜ 1.0. The quenched component contributes to the stellar mass but not to the SFR. It is thus possible to quantify fQ based on the departure of the observed MS slope α from αSF. Adopting the redshift-dependent MS slope reported by Whitaker et al., we explore the evolution of the {f}{{Q}}{--}{M}* relations over z = [0.5, 2.5]. We find that Milky Way-like SFGs (with {M}* ≈ {10}10.7 {M}⊙ ) typically have an fQ = 30%-40% at z ˜ 2.25, whereas this value rapidly rises up to 70%-80% at z ˜ 0.75. The origin of an α ˜ 1.0 MS slope seen in the low-mass regime is also discussed. We argue for a scenario in which the majority of low-mass SFGs stay in a “steady-stage” star formation phase. In this phase, the SFR is mainly regulated by stellar feedback and not significantly influenced by the quenching mechanisms, thus remaining roughly constant over cosmic time. This scenario successfully produces an α ˜ 1.0 MS slope, as well as the observed MS evolution from z = 2.5 to z = 0 at low masses.

  6. Effects of temperature and mass conservation on the typical chemical sequences of hydrogen oxidation

    NASA Astrophysics Data System (ADS)

    Nicholson, Schuyler B.; Alaghemandi, Mohammad; Green, Jason R.

    2018-01-01

    Macroscopic properties of reacting mixtures are necessary to design synthetic strategies, determine yield, and improve the energy and atom efficiency of many chemical processes. The set of time-ordered sequences of chemical species are one representation of the evolution from reactants to products. However, only a fraction of the possible sequences is typical, having the majority of the joint probability and characterizing the succession of chemical nonequilibrium states. Here, we extend a variational measure of typicality and apply it to atomistic simulations of a model for hydrogen oxidation over a range of temperatures. We demonstrate an information-theoretic methodology to identify typical sequences under the constraints of mass conservation. Including these constraints leads to an improved ability to learn the chemical sequence mechanism from experimentally accessible data. From these typical sequences, we show that two quantities defining the variational typical set of sequences—the joint entropy rate and the topological entropy rate—increase linearly with temperature. These results suggest that, away from explosion limits, data over a narrow range of thermodynamic parameters could be sufficient to extrapolate these typical features of combustion chemistry to other conditions.

  7. Estimation of submarine mass failure probability from a sequence of deposits with age dates

    USGS Publications Warehouse

    Geist, Eric L.; Chaytor, Jason D.; Parsons, Thomas E.; ten Brink, Uri S.

    2013-01-01

    The empirical probability of submarine mass failure is quantified from a sequence of dated mass-transport deposits. Several different techniques are described to estimate the parameters for a suite of candidate probability models. The techniques, previously developed for analyzing paleoseismic data, include maximum likelihood and Type II (Bayesian) maximum likelihood methods derived from renewal process theory and Monte Carlo methods. The estimated mean return time from these methods, unlike estimates from a simple arithmetic mean of the center age dates and standard likelihood methods, includes the effects of age-dating uncertainty and of open time intervals before the first and after the last event. The likelihood techniques are evaluated using Akaike’s Information Criterion (AIC) and Akaike’s Bayesian Information Criterion (ABIC) to select the optimal model. The techniques are applied to mass transport deposits recorded in two Integrated Ocean Drilling Program (IODP) drill sites located in the Ursa Basin, northern Gulf of Mexico. Dates of the deposits were constrained by regional bio- and magnetostratigraphy from a previous study. Results of the analysis indicate that submarine mass failures in this location occur primarily according to a Poisson process in which failures are independent and return times follow an exponential distribution. However, some of the model results suggest that submarine mass failures may occur quasiperiodically at one of the sites (U1324). The suite of techniques described in this study provides quantitative probability estimates of submarine mass failure occurrence, for any number of deposits and age uncertainty distributions.

  8. THE CLUSTERED NATURE OF STAR FORMATION. PRE-MAIN-SEQUENCE CLUSTERS IN THE STAR-FORMING REGION NGC 602/N90 IN THE SMALL MAGELLANIC CLOUD

    SciTech Connect

    Gouliermis, Dimitrios A.; Gennaro, Mario; Schmeja, Stefan

    2012-03-20

    Located at the tip of the wing of the Small Magellanic Cloud (SMC), the star-forming region NGC 602/N90 is characterized by the H II nebular ring N90 and the young cluster of pre-main-sequence (PMS) and early-type main-sequence stars NGC 602, located in the central area of the ring. We present a thorough cluster analysis of the stellar sample identified with Hubble Space Telescope/Advanced Camera for Surveys in the region. We show that apart from the central cluster low-mass PMS stars are congregated in 13 additional small, compact sub-clusters at the periphery of NGC 602, identified in terms of their highermore » stellar density with respect to the average background density derived from star counts. We find that the spatial distribution of the PMS stars is bimodal, with an unusually large fraction ({approx}60%) of the total population being clustered, while the remaining is diffusely distributed in the intercluster area, covering the whole central part of the region. From the corresponding color-magnitude diagrams we disentangle an age difference of {approx}2.5 Myr between NGC 602 and the compact sub-clusters, which appear younger, on the basis of comparison of the brighter PMS stars with evolutionary models, which we accurately calculated for the metal abundance of the SMC. The diffuse PMS population appears to host stars as old as those in NGC 602. Almost all detected PMS sub-clusters appear to be centrally concentrated. When the complete PMS stellar sample, including both clustered and diffused stars, is considered in our cluster analysis, it appears as a single centrally concentrated stellar agglomeration, covering the whole central area of the region. Considering also the hot massive stars of the system, we find evidence that this agglomeration is hierarchically structured. Based on our findings, we propose a scenario according to which the region NGC 602/N90 experiences an active clustered star formation for the last {approx}5 Myr. The central cluster NGC

  9. The Gaia-ESO Survey: the present-day radial metallicity distribution of the Galactic disc probed by pre-main-sequence clusters

    NASA Astrophysics Data System (ADS)

    Spina, L.; Randich, S.; Magrini, L.; Jeffries, R. D.; Friel, E. D.; Sacco, G. G.; Pancino, E.; Bonito, R.; Bravi, L.; Franciosini, E.; Klutsch, A.; Montes, D.; Gilmore, G.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Donati, P.; Frasca, A.; Hourihane, A.; Jofré, P.; Lewis, J.; Lind, K.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

    2017-05-01

    Context. The radial metallicity distribution in the Galactic thin disc represents a crucial constraint for modelling disc formation and evolution. Open star clusters allow us to derive both the radial metallicity distribution and its evolution over time. Aims: In this paper we perform the first investigation of the present-day radial metallicity distribution based on [Fe/H] determinations in late type members of pre-main-sequence clusters. Because of their youth, these clusters are therefore essential for tracing the current interstellar medium metallicity. Methods: We used the products of the Gaia-ESO Survey analysis of 12 young regions (age < 100 Myr), covering Galactocentric distances from 6.67 to 8.70 kpc. For the first time, we derived the metal content of star forming regions farther than 500 pc from the Sun. Median metallicities were determined through samples of reliable cluster members. For ten clusters the membership analysis is discussed in the present paper, while for other two clusters (I.e. Chamaeleon I and Gamma Velorum) we adopted the members identified in our previous works. Results: All the pre-main-sequence clusters considered in this paper have close-to-solar or slightly sub-solar metallicities. The radial metallicity distribution traced by these clusters is almost flat, with the innermost star forming regions having [Fe/H] values that are 0.10-0.15 dex lower than the majority of the older clusters located at similar Galactocentric radii. Conclusions: This homogeneous study of the present-day radial metallicity distribution in the Galactic thin disc favours models that predict a flattening of the radial gradient over time. On the other hand, the decrease of the average [Fe/H] at young ages is not easily explained by the models. Our results reveal a complex interplay of several processes (e.g. star formation activity, initial mass function, supernova yields, gas flows) that controlled the recent evolution of the Milky Way. Based on observations

  10. "Polymeromics": Mass spectrometry based strategies in polymer science toward complete sequencing approaches: a review.

    PubMed

    Altuntaş, Esra; Schubert, Ulrich S

    2014-01-15

    Mass spectrometry (MS) is the most versatile and comprehensive method in "OMICS" sciences (i.e. in proteomics, genomics, metabolomics and lipidomics). The applications of MS and tandem MS (MS/MS or MS(n)) provide sequence information of the full complement of biological samples in order to understand the importance of the sequences on their precise and specific functions. Nowadays, the control of polymer sequences and their accurate characterization is one of the significant challenges of current polymer science. Therefore, a similar approach can be very beneficial for characterizing and understanding the complex structures of synthetic macromolecules. MS-based strategies allow a relatively precise examination of polymeric structures (e.g. their molar mass distributions, monomer units, side chain substituents, end-group functionalities, and copolymer compositions). Moreover, tandem MS offer accurate structural information from intricate macromolecular structures; however, it produces vast amount of data to interpret. In "OMICS" sciences, the software application to interpret the obtained data has developed satisfyingly (e.g. in proteomics), because it is not possible to handle the amount of data acquired via (tandem) MS studies on the biological samples manually. It can be expected that special software tools will improve the interpretation of (tandem) MS output from the investigations of synthetic polymers as well. Eventually, the MS/MS field will also open up for polymer scientists who are not MS-specialists. In this review, we dissect the overall framework of the MS and MS/MS analysis of synthetic polymers into its key components. We discuss the fundamentals of polymer analyses as well as recent advances in the areas of tandem mass spectrometry, software developments, and the overall future perspectives on the way to polymer sequencing, one of the last Holy Grail in polymer science. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Negative Electron Transfer Dissociation Sequencing of Increasingly Sulfated Glycosaminoglycan Oligosaccharides on an Orbitrap Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Leach, Franklin E.; Riley, Nicholas M.; Westphall, Michael S.; Coon, Joshua J.; Amster, I. Jonathan

    2017-09-01

    The structural characterization of sulfated glycosaminoglycan (GAG) carbohydrates remains an important target for analytical chemists attributable to challenges introduced by the natural complexity of these mixtures and the defined need for molecular-level details to elucidate biological structure-function relationships. Tandem mass spectrometry has proven to be the most powerful technique for this purpose. Previously, electron detachment dissociation (EDD), in comparison to other methods of ion activation, has been shown to provide the largest number of useful cleavages for de novo sequencing of GAG oligosaccharides, but such experiments are restricted to Fourier transform ion cyclotron resonance mass spectrometers (FTICR-MS). Negative electron transfer dissociation (NETD) provides similar fragmentation results, and can be achieved on any mass spectrometry platform that is designed to accommodate ion-ion reactions. Here, we examine for the first time the effectiveness of NETD-Orbitrap mass spectrometry for the structural analysis of GAG oligosaccharides. Compounds ranging in size from tetrasaccharides to decasaccharides were dissociated by NETD, producing both glycosidic and cross-ring cleavages that enabled the location of sulfate modifications. The highly-sulfated, heparin-like synthetic GAG, ArixtraTM, was also successfully sequenced by NETD. In comparison to other efforts to sequence GAG chains without fully ionized sulfate constituents, the occurrence of sulfate loss peaks is minimized by judicious precursor ion selection. The results compare quite favorably to prior results with electron detachment dissociation (EDD). Significantly, the duty cycle of the NETD experiment is sufficiently short to make it an effective tool for on-line separations, presenting a straightforward path for selective, high-throughput analysis of GAG mixtures. [Figure not available: see fulltext.

  12. Observation and modelling of main-sequence star chromospheres - XII. Two-component model chromospheres for five active dM1e stars

    NASA Astrophysics Data System (ADS)

    Houdebine, E. R.

    2009-08-01

    We aim to constrain the Hα, CaII H and CaII K profiles from quiescent and active regions on active dM1e stars. A preliminary analysis of all the data available for dM1e stars shows that the Hα/CaII equivalent width (EW) ratio varies by up to a factor of 7 for different stars in our sample. We find that spectroscopic binaries have a significantly smaller ratio than single dM1e stars. We also find that the pre-main-sequence stars Gl 616.2, GJ 1264 and Gl 803 have a ratio lower than main-sequence single dM1e stars. These differences imply that different chromospheric structures are present on different stars, notably the temperature minimum must decrease with an increasing Hα/CaII EW ratio. For these reasons, it is impossible to reproduce all observations with only one grid of model chromospheres. We show that the grid of model chromospheres of Paper VI is adequate to describe the physical conditions that prevail in the chromospheres of spectroscopic binaries and pre-main-sequence M1e stars, but not for the conditions in single dM1e stars. One or more additional grids of model chromospheres will be necessary to reproduce all observations. We use the method developed in Paper XI in this series, in order to build two-component model chromospheres for five M1e field stars: FF And A, FF And B, GJ 1264, AU Mic and Gl 815A. Our solutions provide an exact match of the Hα and the mean CaII H & K EWs within measurement uncertainties. We compare the theoretical profiles and the observed profiles of Hα and the CaII H & K resonance lines. On the one hand, our fits to the CaII lines are reasonably good. On the other hand, our models tend to produce Hα profiles with a central absorption that is too deep. This suggests that the column mass at the transition region for plages is underestimated, but this would imply that the contrast factor between quiescent and active regions in the CaII lines is larger than 5. We find that, except in the cases of FF And A and AU Mic, the total

  13. Double-Blind Characterization of Non-Genome-Sequenced Bacteria by Mass Spectrometry-Based Proteomics▿

    PubMed Central

    Jabbour, Rabih E.; Deshpande, Samir V.; Wade, Mary Margaret; Stanford, Michael F.; Wick, Charles H.; Zulich, Alan W.; Skowronski, Evan W.; Snyder, A. Peter

    2010-01-01

    Due to the possibility of a biothreat attack on civilian or military installations, a need exists for technologies that can detect and accurately identify pathogens in a near-real-time approach. One technology potentially capable of meeting these needs is a high-throughput mass spectrometry (MS)-based proteomic approach. This approach utilizes the knowledge of amino acid sequences of peptides derived from the proteolysis of proteins as a basis for reliable bacterial identification. To evaluate this approach, the tryptic digest peptides generated from double-blind biological samples containing either a single bacterium or a mixture of bacteria were analyzed using liquid chromatography-tandem mass spectrometry. Bioinformatic tools that provide bacterial classification were used to evaluate the proteomic approach. Results showed that bacteria in all of the double-blind samples were accurately identified with no false-positive assignment. The MS proteomic approach showed strain-level discrimination for the various bacteria employed. The approach also characterized double-blind bacterial samples to the respective genus, species, and strain levels when the experimental organism was not in the database due to its genome not having been sequenced. One experimental sample did not have its genome sequenced, and the peptide experimental record was added to the virtual bacterial proteome database. A replicate analysis identified the sample to the peptide experimental record stored in the database. The MS proteomic approach proved capable of identifying and classifying organisms within a microbial mixture. PMID:20363779

  14. De Novo Sequencing of Peptides from Top-Down Tandem Mass Spectra

    SciTech Connect

    Vyatkina, Kira; Wu, Si; Dekker, Lennard J. M.

    2015-11-06

    De novo sequencing of proteins and peptides is one of the most important problems in mass spectrometry-driven proteomics. A variety of methods have been developed to accomplish this task from a set of bottom-up tandem (MS/MS) mass spectra. However, a more recently emerged top-down technology, now gaining more and more popularity, opens new perspectives for protein analysis and characterization, implying a need in efficient algorithms for processing this kind of MS/MS data. Here we describe a method that allows to retrieve from a set of top-down MS/MS spectra long and accurate sequence fragments of the proteins contained in a sample.more » To this end, we outline a strategy for generating high-quality sequence tags from top-down spectra, and introduce the concept of a T-Bruijn graph by adapting to the case of tags the notion of an A-Bruijn graph widely used in genomics. The output of the proposed approach represents the set of amino acid strings spelled out by optimal paths in the connected components of a T-Bruijn graph. We illustrate its performance on top-down datasets acquired from carbonic anhydrase 2 (CAH2) and the Fab region of alemtuzumab.« less

  15. Sources and mass fluxes of the main contaminants in a heavily polluted and modified river of the North China Plain.

    PubMed

    Li, Wenzan; Li, Xuyong; Su, Jingjun; Zhao, Hongtao

    2014-04-01

    Many rivers in China and other newly industrialized countries have suffered from severe degradation of water quality in the context of rapid economic growth. An accounting method was developed to investigate the source and mass fluxes of the main contaminants in the Ziya River, a severely polluted and heavily modified river in a semiarid area of the North China Plain, where chemical oxygen demand (COD) and ammonia nitrogen (NH4-N) were the most important indicators of pollution. The results showed that the urban sewage with high concentration of COD and NH4-N dominated the streams, contributing to 80.7 % of the streamflow, 92.2 % of COD, and 94.5 % of NH4-N. The concentrations of COD and NH4-N in streams varied from 24.0-195.0 to 5.8-43.8 mg/L, respectively. Mass fluxes of COD and NH4-N of all pathways were quantified. Much of the polluted water was diverted to irrigation, and some eventually flowed into the Bohai Sea. Installation of adequate wastewater treatment facilities and making strict discharge standards can help improve the water quality. Our findings imply that a simple accounting method provides an extremely well-documented example for load estimation and can be useful for intervention strategies in heavily polluted and modified rivers in newly industrialized countries.

  16. Relative Stability of Peptide Sequence Ions Generated by Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Bythell, Benjamin J.; Hendrickson, Christopher L.; Marshall, Alan G.

    2012-04-01

    We report the use of unimolecular dissociation by infrared radiation for gaseous multiphoton energy transfer to determine relative activation energy (Ea,laser) for dissociation of peptide sequence ions. The sequence ions of interest are mass-isolated; the entire ion cloud is then irradiated with a continuous wave CO2 laser, and the first order rate constant, kd, is determined for each of a series of laser powers. Provided these conditions are met, a plot of the natural logarithm of kd versus the natural logarithm of laser power yields a straight line, whose slope provides a measure of Ea,laser. This method reproduces the Ea values from blackbody radiative dissociation (BIRD) for the comparatively large, singly and doubly protonated bradykinin ions (nominally y 9 and y 9 2+ ). The comparatively small sequence ion systems produce Ea,laser values that are systematic underestimates of theoretical barriers calculated with density functional theory (DFT). However, the relative Ea,laser values are in qualitative agreement with the mobile proton model and available theory. Additionally, novel protonated cyclic-dipeptide (diketopiperazine) fragmentation reactions are analyzed with DFT. FT-ICR MS provides access to sequence ions generated by electron capture dissociation, infrared multiphoton dissociation, and collisional activation methods (i.e., b n , y m , c n , z m • ions).

  17. Tracking down a critical halo mass for killing galaxies through the growth of the red sequence

    NASA Astrophysics Data System (ADS)

    Gilbank, David G.; Balogh, Michael L.

    2008-03-01

    Red-sequence galaxies record the history of terminated star formation in the Universe and can thus provide important clues to the mechanisms responsible for this termination. We construct composite samples of published cluster and field galaxy photometry in order to study the build-up of galaxies on the red sequence, as parametrized by the dwarf-to-giant ratio (DGR). We find that the DGR in clusters is higher than that of the field at all redshifts, implying that the faint end of the red sequence was established first in clusters. We find that the DGR evolves with redshift for both samples, consistent with the `down-sizing' picture of star formation. We examine the predictions of semi-analytic models for the DGR and find that neither the magnitude of its environmental dependence nor its evolution is correctly predicted in the models. Red-sequence DGRs are consistently too high in the models, the most likely explanation being that the strangulation mechanism used to remove hot gas from satellite galaxies is too efficient. Finally, we present a simple toy model including a threshold mass, below which galaxies are not strangled, and show that this can predict the observed evolution of the field DGR.

  18. Sequencing Lys-N Proteolytic Peptides by ESI and MALDI Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Dupré, Mathieu; Cantel, Sonia; Verdié, Pascal; Martinez, Jean; Enjalbal, Christine

    2011-02-01

    In this study, we explored the MS/MS behavior of various synthetic peptides that possess a lysine residue at the N-terminal position. These peptides were designed to mimic peptides produced upon proteolysis by the Lys-N enzyme, a metalloendopeptidase issued from a Japanese fungus Grifola frondosa that was recently investigated in proteomic studies as an alternative to trypsin digestion, as a specific cleavage at the amide X-Lys chain is obtained that provides N-terminal lysine peptide fragments. In contrast to tryptic peptides exhibiting a lysine or arginine residue solely at the C-terminal position, and are thus devoid of such basic amino acids within the sequence, these Lys-N proteolytic peptides can contain the highly basic arginine residue anywhere within the peptide chain. The fragmentation patterns of such sequences with the ESI-QqTOF and MALDI-TOF/TOF mass spectrometers commonly used in proteomic bottom-up experiments were investigated.

  19. The position of confirmed pre-main sequence pulsators in the H-R diagram and an overview of their properties

    NASA Astrophysics Data System (ADS)

    Zwintz, Konstanze; Casey, Mike; Guenther, David

    2014-02-01

    Pre-main sequence (PMS) stars can become vibrationally unstable during their evolution to the zero-age main sequence (ZAMS). As they gain their energy from gravitational contraction and have not started nuclear fusion in their cores yet, their inner structures are significantly different to those of (post-) main sequence stars and can be probed by asteroseismology. Using photometric time series from ground and from space (MOST, CoRoT & Spitzer) the number of confirmed pulsating pre-main sequence stars has increased significantly within the last years and allowed to find members of new classes of PMS pulsators. Apart from the well-established group of δ Scuti type PMS stars, members of the groups of PMS γ Doradus, PMS δ Scuti - γ Doradus hybrid and PMS slowly pulsating B (SPB) stars have been discovered. For five PMS δ Scuti candidates, space photometry has revealed that they only show irregular variability, but no pulsations. The unique high-precision space data were combined with dedicated high-resolution spectra to probe the parameter space in the H-R diagram and study the properties of PMS pulsators in comparison to their evolutionary stage.

  20. Bimodality of light and s-elements in M4 (NGC 6121). A hint for the massive main-sequence star pollution scenario

    NASA Astrophysics Data System (ADS)

    Villanova, S.; Geisler, D.

    2011-11-01

    Context. All globular clusters (GCs) studied in detail host two or more populations of stars (the multiple population phenomenon). Theoretical models suggest that the second population is formed from gas polluted by processed material produced by massive stars of the first generation. However the nature of the polluters is matter of strong debate. Several candidates have been proposed: massive main-sequence stars (fast rotating or binaries), intermediate-mass AGB stars, or SNeII. Aims: We studied red giant branch (RGB) stars in the GC M4 (NGC 6121) to measure their chemical signature. Our goal is to measure abundances for many key elements (from Li to Eu) in order to derive constraints on the polluters responsible for the multiple populations. Methods: We observed 23 RGB stars below the RGB-bump using the GIRAFFE spectroscopic facility installed on VLT2. Spectra cover a wide range and allowed us to measure light (Li, C, 12C/13C, N, O, Na, Mg, Al), α (Si, Ca, Ti), iron-peak (Cr, Fe, Ni), light-s (Y), heavy-s (Ba), and r (Eu) elements. We supplemented this study by analyzing an additional subsample of the UVES spectra in order to gather further clues about light s-elements of different atomic number (Y and Zr). Results: We confirm the presence of a bimodal population. Stars can be easily separated according to their N content. The two groups have different C, 12C/13C, N, O, Na content, but share the same Li, C+N+O, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zr, Ba and Eu abundance. Quite surprisingly the two groups differ also in their Y abundance. This result is strongly supported also by the analysis of the UVES spectra. Conclusions: The absence of a spread in α-elements, Eu and Ba makes SNeII and AGB stars unlikely as polluters. On the other hand, massive main-sequence stars can explain the bimodality of Y through the weak s-process. This statement is confirmed independently also by literature data on Rb and Pb. The lack of a Mg/Al spread and the extension of the [O

  1. The Distances to Open Clusters from Main-sequence Fitting. V. Extension of Color Calibration and Test Using Cool and Metal-rich Stars in NGC 6791

    NASA Astrophysics Data System (ADS)

    An, Deokkeun; Terndrup, Donald M.; Pinsonneault, Marc H.; Lee, Jae-Woo

    2015-09-01

    We extend our effort to calibrate stellar isochrones in the Johnson-Cousins ({{BVI}}C) and the 2MASS ({{JHK}}s) filter systems based on observations of well-studied open clusters. Using cool main-sequence (MS) stars in Praesepe, we define empirical corrections to the Lejeune et al. color-effective temperature ({T}{eff}) relations down to {T}{eff}˜ 3600 {{K}}, complementing our previous work based on the Hyades and the Pleiades. We apply empirically corrected isochrones to existing optical and near-infrared photometry of cool ({T}{eff}≲ 5500 {{K}}) and metal-rich ([{Fe}/{{H}}]= +0.37) MS stars in NGC 6791. The current methodology relies on an assumption that color-{T}{eff} corrections are independent of metallicity, but we find that estimates of color excess and distance from color-magnitude diagrams with different color indices converge on each other at the precisely known metallicity of the cluster. Along with a satisfactory agreement with eclipsing binary data in the cluster, we view the improved internal consistency as a validation of our calibrated isochrones at super-solar metallicities. For very cool stars ({T}{eff}≲ 4800 {{K}}), however, we find that B - V colors of our models are systematically redder than the cluster photometry by ˜0.02 mag. We use color-{T}{eff} transformations from the infrared flux method and alternative photometry to examine a potential color-scale error in the input cluster photometry. After excluding B - V photometry of these cool MS stars, we derive E(B\\-\\V)=0.105+/- 0.014, [M/H]\\=\\+0.42+/- 0.07, {(m\\-\\M)}0=13.04+/- 0.08, and the age of 9.5 ± 0.3 Gyr for NGC 6791.

  2. A HIGHER EFFICIENCY OF CONVERTING GAS TO STARS PUSHES GALAXIES AT z ∼ 1.6 WELL ABOVE THE STAR-FORMING MAIN SEQUENCE

    SciTech Connect

    Silverman, J. D.; Rujopakarn, W.; Daddi, E.

    2015-10-20

    Local starbursts have a higher efficiency of converting gas into stars, as compared to typical star-forming galaxies at a given stellar mass, possibly indicative of different modes of star formation. With the peak epoch of galaxy formation occurring at z > 1, it remains to be established whether such an efficient mode of star formation is occurring at high redshift. To address this issue, we measure the molecular gas content of seven high-redshift (z ∼ 1.6) starburst galaxies with the Atacama Large Millimeter/submillimeter Array and IRAM/Plateau de Bure Interferometer. Our targets are selected from the sample of Herschel far-infrared-detected galaxiesmore » having star formation rates (∼300–800 M{sub ⊙} yr{sup −1}) elevated (≳4×) above the star-forming main sequence (MS) and included in the FMOS-COSMOS near-infrared spectroscopic survey of star-forming galaxies at z ∼ 1.6 with Subaru. We detect CO emission in all cases at high levels of significance, indicative of high gas fractions (∼30%–50%). Even more compelling, we firmly establish with a clean and systematic selection that starbursts, identified as MS outliers, at high redshift generally have a lower ratio of CO to total infrared luminosity as compared to typical MS star-forming galaxies, although with a smaller offset than expected based on past studies of local starbursts. We put forward a hypothesis that there exists a continuous increase in star formation efficiency with elevation from the MS with galaxy mergers as a possible physical driver. Along with a heightened star formation efficiency, our high-redshift sample is similar in other respects to local starbursts, such as being metal rich and having a higher ionization state of the interstellar medium.« less

  3. Three-Site Photometric Monitoring of the δ Sct-Type Pulsating Star V1162 Orionis: Period Change and its Implications for Pre-Main Sequence Evolution

    NASA Astrophysics Data System (ADS)

    Kim, Seung-Lee; Cha, Sang-Mok; Lim, Beomdu; Lee, Jae Woo; Lee, Chung-Uk; Lee, Yongseok; Kim, Dong-Jin; Lee, Dong-Joo; Koo, Jae-Rim; Hong, Kyeongsoo; Ryu, Yoon-Hyun; Park, Byeong-Gon

    2016-10-01

    We present photometric results of the δ Sct star V1162 Ori, which is extensively monitored for a total of 49 nights from mid-December 2014 to early-March 2015. The observations are made with three KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes installed in Chile, South Africa, and Australia. Multiple frequency analysis is applied to the data and resulted in clear detection of seven frequencies without an alias problem: five known frequencies and two new ones with small amplitudes of 1.2-1.7 mmag. The amplitudes of all but one frequency are significantly different from previous results, confirming the existence of long-term amplitude changes. We examine the variations in pulsation timings of V1162 Ori for about 30 years by using the times of maximum light obtained from our data and collected from the literatures. The O-C (Observed minus Calculated) timing diagram shows a combination of a downward parabolic variation with a period decreasing rate of (1/P)dP/dt = -4.22 × 10^{-6} year^{-1} and a cyclic change with a period of about 2780 days. The most probable explanation for this cyclic variation is the light-travel-time effect caused by an unknown binary companion, which has a minimum mass of 0.69 M_⊙. V1162 Ori is the first δ Sct-type pulsating star of which the observed fast period decrease can be interpreted as an evolutionary effect of a pre-main sequence star, considering its membership of the Orion OB 1c association.}

  4. Measurement of Spin-orbit Misalignment and Nodal Precession for the Planet around Pre-main-sequence Star PTFO 8-8695 from Gravity Darkening

    NASA Astrophysics Data System (ADS)

    Barnes, Jason W.; van Eyken, Julian C.; Jackson, Brian K.; Ciardi, David R.; Fortney, Jonathan J.

    2013-09-01

    PTFO 8-8695b represents the first transiting exoplanet candidate orbiting a pre-main-sequence star (van Eyken et al. 2012, ApJ, 755, 42). We find that the unusual lightcurve shapes of PTFO 8-8695 can be explained by transits of a planet across an oblate, gravity-darkened stellar disk. We develop a theoretical framework for understanding precession of a planetary orbit's ascending node for the case when the stellar rotational angular momentum and the planetary orbital angular momentum are comparable in magnitude. We then implement those ideas to simultaneously and self-consistently fit two separate lightcurves observed in 2009 December and 2010 December. Our two self-consistent fits yield Mp = 3.0 M Jup and Mp = 3.6 M Jup for assumed stellar masses of M * = 0.34 M ⊙ and M * = 0.44 M ⊙ respectively. The two fits have precession periods of 293 days and 581 days. These mass determinations (consistent with previous upper limits) along with the strength of the gravity-darkened precessing model together validate PTFO 8-8695b as just the second hot Jupiter known to orbit an M-dwarf. Our fits show a high degree of spin-orbit misalignment in the PTFO 8-8695 system: 69° ± 2° or 73.°1 ± 0.°5, in the two cases. The large misalignment is consistent with the hypothesis that planets become hot Jupiters with random orbital plane alignments early in a system's lifetime. We predict that as a result of the highly misaligned, precessing system, the transits should disappear for months at a time over the course of the system's precession period. The precessing, gravity-darkened model also predicts other observable effects: changing orbit inclination that could be detected by radial velocity observations, changing stellar inclination that would manifest as varying vsin i, changing projected spin-orbit alignment that could be seen by the Rossiter-McLaughlin effect, changing transit shapes over the course of the precession, and differing lightcurves as a function of wavelength

  5. Hydrodynamic simulations of the interaction between an AGB star and a main-sequence companion in eccentric orbits

    NASA Astrophysics Data System (ADS)

    Staff, Jan E.; De Marco, Orsola; Macdonald, Daniel; Galaviz, Pablo; Passy, Jean-Claude; Iaconi, Roberto; Low, Mordecai-Mark Mac

    2016-02-01

    The Rotten Egg Nebula has at its core a binary composed of a Mira star and an A-type companion at a separation >10 au. It has been hypothesized to have formed by strong binary interactions between the Mira and a companion in an eccentric orbit during periastron passage ˜800 yr ago. We have performed hydrodynamic simulations of an asymptotic giant branch (AGB) star interacting with companions with a range of masses in orbits with a range of initial eccentricities and periastron separations. For reasonable values of the eccentricity, we find that Roche lobe overflow can take place only if the periods are ≪100 yr. Moreover, mass transfer causes the system to enter a common envelope phase within several orbits. Since the central star of the Rotten Egg nebula is an AGB star, we conclude that such a common envelope phase must have lead to a merger, so the observed companion must have been a tertiary companion of a binary that merged at the time of nebula ejection. Based on the mass and time-scale of the simulated disc formed around the companion before the common envelope phase, we analytically estimate the properties of jets that could be launched. Allowing for super-Eddington accretion rates, we find that jets similar to those observed are plausible, provided that the putative lost companion was relatively massive.

  6. Explaining the luminosity spread in young clusters: proto and pre-main sequence stellar evolution in a molecular cloud environment

    NASA Astrophysics Data System (ADS)

    Jensen, Sigurd S.; Haugbølle, Troels

    2018-02-01

    Hertzsprung-Russell diagrams of star-forming regions show a large luminosity spread. This is incompatible with well-defined isochrones based on classic non-accreting protostellar evolution models. Protostars do not evolve in isolation of their environment, but grow through accretion of gas. In addition, while an age can be defined for a star-forming region, the ages of individual stars in the region will vary. We show how the combined effect of a protostellar age spread, a consequence of sustained star formation in the molecular cloud, and time-varying protostellar accretion for individual protostars can explain the observed luminosity spread. We use a global magnetohydrodynamic simulation including a sub-scale sink particle model of a star-forming region to follow the accretion process of each star. The accretion profiles are used to compute stellar evolution models for each star, incorporating a model of how the accretion energy is distributed to the disc, radiated away at the accretion shock, or incorporated into the outer layers of the protostar. Using a modelled cluster age of 5 Myr, we naturally reproduce the luminosity spread and find good agreement with observations of the Collinder 69 cluster, and the Orion Nebular Cluster. It is shown how stars in binary and multiple systems can be externally forced creating recurrent episodic accretion events. We find that in a realistic global molecular cloud model massive stars build up mass over relatively long time-scales. This leads to an important conceptual change compared to the classic picture of non-accreting stellar evolution segmented into low-mass Hayashi tracks and high-mass Henyey tracks.

  7. Sequence and Conformational Analysis of Peptide-Polymer Bioconjugates by Multidimensional Mass Spectrometry.

    PubMed

    Sallam, Sahar; Dolog, Ivan; Paik, Bradford A; Jia, Xinqiao; Kiick, Kristi L; Wesdemiotis, Chrys

    2018-03-19

    The sequence and helical content of two alanine-rich peptides (AQK18 and GpAQK18, Gp: L-propargylglycine) and their conjugates with poly(ethylene glycol) (PEG) have been investigated by multidimensional mass spectrometry (MS), encompassing electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI) interfaced with tandem mass spectrometry (MS 2 ) fragmentation and shape-sensitive separation via ion mobility mass spectrometry (IM-MS). The composition, sequence, and molecular weight distribution of the peptides and bioconjugates were identified by MS and MS 2 experiments, which also confirmed the attachment of PEG at the C-terminus of the peptides. ESI coupled with IM-MS revealed the existence of random coil and α-helical conformers for the peptides in the gas phase. More importantly, the proportion of the helical conformation increased substantially after PEG attachment, suggesting that conjugation adds stability to this conformer. The conformational assemblies detected in the gas phase were largely formed in solution, as corroborated by independent circular dichroism (CD) experiments. The collision cross-sections (rotationally averaged forward moving arears) of the random coil and helical conformers of the peptides and their PEG conjugates were simulated for comparison with the experimental values deduced by IM-MS in order to confirm the identity of the observed architectures and understand the stabilizing effect of the polymer chain. C-terminal PEGylation is shown to increase the positive charge density and to solvate intra-molecular positive charges at the conjugation site, thereby enhancing the stability of α-helices, preserving their conformation, and increasing helical propensity.

  8. Association of dysfunctional uterine bleeding with high body mass index and obesity as a main predisposing factor.

    PubMed

    Nouri, Mahnaz; Tavakkolian, Abbas; Mousavi, Seyede Roya

    2014-01-01

    Dysfunctional uterine bleeding (DUB) defined as abnormal uterine bleeding in the absence of underlying structural abnormalities. Recently, obesity has been suggested as a main underling risk factor for DUB; however, evidences on the role of this predisposing factor are not adequate. The current study aimed to assess status of obesity in women who suffered from DUB. In an observational case series study conducted at a referral endocrinology clinic in Shahrood city, Samnan, 20 consecutive women with the final diagnosis of DUB referred from 2009 to 2011 were evaluated. Obesity was assessed using calculation of body mass index (BMI) and waist circumference. The mean waist circumference was estimated 102.95±9.77 cm in the range of 90-119 cm. With respect to BMI measurement, the mean of BMI was 32.63±3.34 kg/m(2) ranged between 26.92 and 39.06 that two-third of studied women suffered from overweight status and other one-third cases were obese. There is a strong association between obesity and DUB and therefore weight reduction should be considered as a conservative treatment besides of other medical or surgical treatment approaches. Copyright © 2013. Published by Elsevier Ltd.

  9. Dried blood spots: liquid chromatography-mass spectrometry analysis of Δ9-tetrahydrocannabinol and its main metabolites.

    PubMed

    Mercolini, Laura; Mandrioli, Roberto; Sorella, Vittorio; Somaini, Lorenzo; Giocondi, Daniele; Serpelloni, Giovanni; Raggi, Maria Augusta

    2013-01-04

    A sensitive and selective HPLC-MS/MS method has been developed for the first time for the analysis of Δ(9)-tetrahydrocannabinol (the most important active cannabinoid) and its hydroxylated and carboxylated metabolites in human Dried Blood Spots (DBSs). The simultaneous determination of Δ(9)-tetrahydrocannabinol and its two main metabolites allows assessing the time elapsed after the drug intake and distinguishing between acute or former consumption. This is an important information in specific contexts such as "on street" controls by police forces. DBSs have been chosen as the optimal biological matrix for this kind of testing, since they provide information on the actual state of intoxication, without storage and transportation problems usually associated with classical blood testing. The analysis is carried out on a C8 reversed phase column with a mobile phase composed of 0.1% formic acid in a water/methanol mixture and an electrospray ionisation (ESI) source, coupled to a triple quadrupole mass spectrometer. The method was validated according to international guidelines, with satisfactory results in terms of extraction yields, precision, stability and accuracy. Application to real DBS samples from Cannabis abusers gave reliable results, thus confirming the methodology suitability for roadside testing. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Changing environments of pre-main-sequence stars and their effect on the 3 microns ice feature

    NASA Technical Reports Server (NTRS)

    Graham, J. A.; Chen, W. P.

    1991-01-01

    Three micron spectra of three premain-sequence stellar objects are presented. The heavily embedded infrared source HH100-IR, and two optically visible stars that apparently power the Herbig-Haro objects HH52, 53, 54, and HH57, are likely to represent different stages during early stellar evolution. The medium-resolution spectra of HH100-IR confirm the existence of a very strong ice band absorption (optical depth 0.8-1.2 at 3.07 microns) discovered by Whittet & Blades MNRAS, 191, 309 (1980) with lower resolution. Each of the visible stars shows a weaker (optical depth 0.2-0.4) water-ice feature but with a relatively prominent absorption dip at 2.97 microns which it is believed is due to ammonia ice. A detailed inspection of the line profiles suggests that the environment around the optically visible stars is significantly warmer (about 100 K) than that around HH100-IR (about 10-20 K) and that processing of remnant circumstellar dust is already underway.

  11. A search for pre-main-sequence stars in high-latitude molecular clouds. 3: A survey of the Einstein database

    NASA Technical Reports Server (NTRS)

    Caillault, Jean-Pierre; Magnani, Loris; Fryer, Chris

    1995-01-01

    In order to discern whether the high-latitude molecular clouds are regions of ongoing star formation, we have used X-ray emission as a tracer of youthful stars. The entire Einstein database yields 18 images which overlap 10 of the clouds mapped partially or completely in the CO (1-0) transition, providing a total of approximately 6 deg squared of overlap. Five previously unidentified X-ray sources were detected: one has an optical counterpart which is a pre-main-sequence (PMS) star, and two have normal main-sequence stellar counterparts, while the other two are probably extragalactic sources. The PMS star is located in a high Galactic latitude Lynds dark cloud, so this result is not too suprising. The translucent clouds, though, have yet to reveal any evidence of star formation.

  12. Water mass-specificity of bacterial communities in the North Atlantic revealed by massively parallel sequencing

    PubMed Central

    Agogué, Hélène; Lamy, Dominique; Neal, Phillip R.; Sogin, Mitchell L.; Herndl, Gerhard J.

    2011-01-01

    Bacterial assemblages from subsurface (100 m depth), meso- (200–1000 m depth) and bathy-pelagic (below 1000 m depth) zones at 10 stations along a North Atlantic Ocean transect from 60°N to 5°S were characterized using massively parallel pyrotag sequencing of the V6 region of the 16S rRNA gene (V6 pyrotags). In a dataset of more than 830,000 pyrotags we identified 10,780 OTUs of which 52% were singletons. The singletons accounted for less than 2% of the OTU abundance, while the 100 and 1,000 most abundant OTUs represented 80% and 96%, respectively, of all recovered OTUs. Non-metric Multi-Dimensional Scaling and Canonical Correspondence Analysis of all the OTUs excluding the singletons revealed a clear clustering of the bacterial communities according to the water masses. More than 80% of the 1,000 most abundant OTUs corresponded to Proteobacteria of which 55% were Alphaproteobacteria, mostly composed of the SAR11 cluster. Gammaproteobacteria increased with depth and included a relatively large number of OTUs belonging to Alteromonadales and Oceanospirillales. The bathypelagic zone showed higher taxonomic evenness than the overlying waters, albeit bacterial diversity was remarkably variable. Both abundant and low-abundance OTUs were responsible for the distinct bacterial communities characterizing the major deep-water masses. Taken together, our results reveal that deep-water masses act as bio-oceanographic islands for bacterioplankton leading to water mass-specific bacterial communities in the deep waters of the Atlantic. PMID:21143328

  13. Variable extinction in HD 45677 and the evolution of dust grains in pre-main-sequence disks

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Halbedel, Elaine M.; Lawrence, Geoffrey F.; Smith, J. Allyn; Yanow, Ken

    1994-01-01

    Changes in the UV extinction and IR emission were sought in the Herbig Ae/Be star candidate HD 45677 (= FS CMa) by comparing UV, optical, and IR observations made approximately 10 yr apart. HD 45677 varied significantly, becoming more than 50% brighter in the UV and optical than it was a decade ago. A comparison of the observations between epochs indicates that if the variations are due to changes in dust obscuration, the dust acts as a gray absorber into the near-IR and must be depleted in grains smaller than 1 micron. This is similar to the results obtained on the circumstellar disks of stars like Vega and Beta Pic, and suggests that radiation pressure may be responsible for the small-grain depletion. In addition, the total IR flux seems to have declined, indicating a decrease in the total mass of the dust envelope that contributes to the IR emission in this part of the spectrum. Due to the anomalous nature of the extinction, the use of normal extinction curves to deredden the spectral energy distributions of stars with circumstellar dust may lead to significant errors and should be used with great caution.

  14. Accretion and outflow activity on the late phases of pre-main-sequence evolution. The case of RZ Piscium

    NASA Astrophysics Data System (ADS)

    Potravnov, I. S.; Mkrtichian, D. E.; Grinin, V. P.; Ilyin, I. V.; Shakhovskoy, D. N.

    2017-03-01

    RZ Psc is an isolated high-latitude post-T Tauri star that demonstrates a UX Ori-type photometric activity. The star shows very weak spectroscopic signatures of accretion, but at the same time possesses the unusual footprints of the wind in Na I D lines. In the present work we investigate new spectroscopic observations of RZ Psc obtained in 2014 during two observation runs. We found variable blueshifted absorption components (BACs) in lines of the other alcali metals, K I 7699 Å and Ca II IR triplet. We also confirmed the presence of a weak emission component in the Hα line, which allowed us to estimate the mass accretion rate on the star as Ṁ ≤ 7 × 10-12M⊙ yr-1. We could not reveal any clear periodicity in the appearance of BACs in sodium lines. Nevertheless, the exact coincidence of the structure and velocities of the Na I D absorptions observed with the interval of about one year suggests that such a periodicity should exist.

  15. Extending the Substellar Sequence to Planetary Masses with Distances from Spitzer Parallaxes

    NASA Astrophysics Data System (ADS)

    Dupuy, Trent

    A major goal in contemporary astrophysics is to extend the study of stellar atmospheres to the much cooler atmospheres of gas-giant extrasolar planets. One key pathway is the identification of free-floating substellar objects that not only share common temperatures with exoplanets but also common masses and thus surface gravities. In recent years, searches for ever colder freefloating objects have steadily pushed the census to ever lower masses and finally into this longsought planetary-mass regime (5-15 Jupiter masses; Y dwarfs). The empirical backbone of the exploration of these new substellar samples is the accurate measurement of distances via trigonometric parallaxes. Distances allow us to make empirical sequences of absolute magnitude versus color and spectral type to compare to better studied normal brown dwarfs, as well as providing absolute bolometric fluxes and thereby luminosities and temperatures. However, unlike simple photometry or spectroscopy, parallax measurements are time consuming and prone to large systematic errors when attempted by combining data from multiple telescopes and bandpasses. Spitzer/IRAC is poised to deliver the definitive sample of parallax distances for the coldest brown dwarfs. It is the only facility capable of measuring high-precision astrometry efficiently for a large sample of such faint substellar objects, as validated by our past work. Spitzer was never intended to deliver high quality astrometry, but using our custom built astrometric pipeline we have successfully produced the first precise IRAC astrometry and measured distances for a small initial sample of the coldest brown dwarfs (Dupuy & Kraus 2013). We showed that in spite of the seemingly subtle spectral changes from T8 to Y0 (only 2 subtypes), the mean effective temperature plummets by almost a factor of 2, from 700 K for T8 dwarfs to 400 K for Y0 dwarfs. Even in this small sample, we found some objects that seemed to defy the expectation that later spectral type

  16. XMM-NEWTON MONITORING OF THE CLOSE PRE-MAIN-SEQUENCE BINARY AK SCO. EVIDENCE OF TIDE-DRIVEN FILLING OF THE INNER GAP IN THE CIRCUMBINARY DISK

    SciTech Connect

    Gomez de Castro, Ana Ines; Lopez-Santiago, Javier; Talavera, Antonio

    2013-03-20

    AK Sco stands out among pre-main-sequence binaries because of its prominent ultraviolet excess, the high eccentricity of its orbit, and the strong tides driven by it. AK Sco consists of two F5-type stars that get as close as 11 R{sub *} at periastron passage. The presence of a dense (n{sub e} {approx} 10{sup 11} cm{sup -3}) extended envelope has been unveiled recently. In this article, we report the results from an XMM-Newton-based monitoring of the system. We show that at periastron, X-ray and UV fluxes are enhanced by a factor of {approx}3 with respect to the apastron values. The X-raymore » radiation is produced in an optically thin plasma with T {approx} 6.4 Multiplication-Sign 10{sup 6} K and it is found that the N{sub H} column density rises from 0.35 Multiplication-Sign 10{sup 21} cm{sup -2} at periastron to 1.11 Multiplication-Sign 10{sup 21} cm{sup -2} at apastron, in good agreement with previous polarimetric observations. The UV emission detected in the Optical Monitor band seems to be caused by the reprocessing of the high-energy magnetospheric radiation on the circumstellar material. Further evidence of the strong magnetospheric disturbances is provided by the detection of line broadening of 278.7 km s{sup -1} in the N V line with Hubble Space Telescope/Space Telescope Imaging Spectrograph. Numerical simulations of the mass flow from the circumbinary disk to the components have been carried out. They provide a consistent scenario with which to interpret AK Sco observations. We show that the eccentric orbit acts like a gravitational piston. At apastron, matter is dragged efficiently from the inner disk border, filling the inner gap and producing accretion streams that end as ring-like structures around each component of the system. At periastron, the ring-like structures come into contact, leading to angular momentum loss, and thus producing an accretion outburst.« less

  17. Proteomics of Soil and Sediment: Protein Identification by De Novo Sequencing of Mass Spectra Complements Traditional Database Searching

    NASA Astrophysics Data System (ADS)

    Miller, S.; Rizzo, A. I.; Waldbauer, J.

    2014-12-01

    Proteomics has the potential to elucidate the metabolic pathways and taxa responsible for in situ biogeochemical transformations. However, low rates of protein identification from high resolution mass spectra have been a barrier to the development of proteomics in complex environmental samples. Much of the difficulty lies in the computational challenge of linking mass spectra to their corresponding proteins. Traditional database search methods for matching peptide sequences to mass spectra are often inadequate due to the complexity of environmental proteomes and the large database search space, as we demonstrate with soil and sediment proteomes generated via a range of extraction methods. One alternative to traditional database searching is de novo sequencing, which identifies peptide sequences without the need for a database. BLAST can then be used to match de novo sequences to similar genetic sequences. Assigning confidence to putative identifications has been one hurdle for the implementation of de novo sequencing. We found that accurate de novo sequences can be screened by quality score and length. Screening criteria are verified by comparing the results of de novo sequencing and traditional database searching for well-characterized proteomes from simple biological systems. The BLAST hits of screened sequences are interrogated for taxonomic and functional information. We applied de novo sequencing to organic topsoil and marine sediment proteomes. Peak-rich proteomes, which can result from various extraction techniques, yield thousands of high-confidence protein identifications, an improvement over previous proteomic studies of soil and sediment. User-friendly software tools for de novo metaproteomics analysis have been developed. This "De Novo Analysis" Pipeline is also a faster method of data analysis than constructing a tailored sequence database for traditional database searching.

  18. Proteomics of Soil and Sediment: Protein Identification by De Novo Sequencing of Mass Spectra Complements Traditional Database Searching

    NASA Astrophysics Data System (ADS)

    Miller, S.; Rizzo, A. I.; Waldbauer, J.

    2015-12-01

    Proteomics has the potential to elucidate the metabolic pathways and taxa responsible for in situ biogeochemical transformations. However, low rates of protein identification from high resolution mass spectra have been a barrier to the development of proteomics in complex environmental samples. Much of the difficulty lies in the computational challenge of linking mass spectra to their corresponding proteins. Traditional database search methods for matching peptide sequences to mass spectra are often inadequate due to the complexity of environmental proteomes and the large database search space, as we demonstrate with soil and sediment proteomes generated via a range of extraction methods. One alternative to traditional database searching is de novo sequencing, which identifies peptide sequences without the need for a database. BLAST can then be used to match de novo sequences to similar genetic sequences. Assigning confidence to putative identifications has been one hurdle for the implementation of de novo sequencing. We found that accurate de novo sequences can be screened by quality score and length. Screening criteria are verified by comparing the results of de novo sequencing and traditional database searching for well-characterized proteomes from simple biological systems. The BLAST hits of screened sequences are interrogated for taxonomic and functional information. We applied de novo sequencing to organic topsoil and marine sediment proteomes. Peak-rich proteomes, which can result from various extraction techniques, yield thousands of high-confidence protein identifications, an improvement over previous proteomic studies of soil and sediment. User-friendly software tools for de novo metaproteomics analysis have been developed. This "De Novo Analysis" Pipeline is also a faster method of data analysis than constructing a tailored sequence database for traditional database searching.

  19. Observation and modelling of main-sequence star chromospheres - XIX. FIES and FEROS observations of dM1 stars

    NASA Astrophysics Data System (ADS)

    Houdebine, E. R.; Butler, C. J.; Garcia-Alvarez, D.; Telting, J.

    2012-10-01

    magnetic activity in M1 dwarfs increases with the radius. For the first time, we investigate the Wilson-Bappu correlation for a given spectral type. We find a rather linear correlation for stars of absolute magnitude greater than 9.6, but below this value the FWHM seems to saturate. In fact, we show that these Wilson-Bappu type correlations are activity-FWHM correlations and are due to the diminishing column mass of the transition region with decreasing activity level. Based on observations available at the European Southern Observatory data bases and on Hipparcos parallax measurements.

  20. Observation and modelling of main-sequence star chromospheres - XIV. Rotation of dM1 stars

    NASA Astrophysics Data System (ADS)

    Houdebine, E. R.

    2010-09-01

    We have measured v sin i for a selected sample of dM1-type stars. We give 114 measurements of v sin i for 88 different stars, and six upper detection limits. These are the first measurements of v sin i for most of the stars studied here. This represents the largest sample of v sin i measurements for M dwarfs at a given spectral type. For these measurements, we used four different spectrographs: HARPS (ESO), SOPHIE (OHP), ÉLODIE (OHP) and UVES (ESO). Two of these spectrographs (HARPS and SOPHIE) are particularly stable in wavelength since they were designed for exoplanet searches. We measured v sin i down to an accuracy of 0.3kms-1 for the highest resolution spectrographs and a detection limit of about 1kms-1. We show that this unprecedented accuracy for M dwarfs in our data set is possible because all the targets have the same spectral type. This is an advantage and it facilitates the determination of the narrowest line profiles for v sin i ~ 0. Although it is possible to derive the zero-point profiles using several spectral types at a time. These values were combined with other measurements taken from the literature. The total sample represents detected rotation for 100 stars (10 dM1e and 90 dM1 stars). We confirm our finding of Paper VII that the distribution of the projected rotation period is bimodal for dM1 stars with a much larger sample, i.e. there are two groups of stars: the fast rotators with P/sin i ~ 4.5d and the slow rotators with P/sin i ~ 14.4d. There is a gap between these two groups. We find that the distribution of stars as a function of P/sin i has two very abrupt cuts, below 10d and above 18d. There are very few stars observed out of this range 10-18d. We also observe that the distribution increases slightly from 18 to 10d. We find that the M1 subdwarfs (very low metallicity dwarfs) rotate with an average period of P/sin i ~ 7.2d, which is about twice faster as the main group of normal M1 dwarfs. We also find a correlation for P/sin i to

  1. The Intrinsic Characteristics of Galaxies on the SFR–M ∗ Plane at 1.2 < z < 4: I. The Correlation between Stellar Age, Central Density, and Position Relative to the Main Sequence

    NASA Astrophysics Data System (ADS)

    Lee, Bomee; Giavalisco, Mauro; Whitaker, Katherine; Williams, Christina C.; Ferguson, Henry C.; Acquaviva, Viviana; Koekemoer, Anton M.; Straughn, Amber N.; Guo, Yicheng; Kartaltepe, Jeyhan S.; Lotz, Jennifer; Pacifici, Camilla; Croton, Darren J.; Somerville, Rachel S.; Lu, Yu

    2018-02-01

    We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M *), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the mass-weighted stellar age, in galaxies at 1.2< z< 4. We do this by making new measures of M *, SFR, and stellar age thanks to an improved SED fitting procedure that allows various star formation history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the ({M}* ;{SFR}) plane bends at high mass. We observe clear morphological differences among galaxies across the MS, which also correlate with stellar age. At all redshifts, galaxies that are quenching or quenched, and thus old, have high {{{Σ }}}1 (the projected density within the central 1 kpc), while younger, star-forming galaxies span a much broader range of {{{Σ }}}1, which includes the high values observed for quenched galaxies, but also extends to much lower values. As galaxies age and quench, the stellar age and the dispersion of {{{Σ }}}1 for fixed values of M * shows two different regimes: one at the low-mass end, where quenching might be driven by causes external to the galaxies; the other at the high-mass end, where quenching is driven by internal causes, very likely the mass given the low scatter of {{{Σ }}}1 (mass quenching). We suggest that the monotonic increase of central density as galaxies grow is one manifestation of a more general phenomenon of structural transformation that galaxies undergo as they evolve.

  2. The association between p,p'-DDE levels and left ventricular mass is mainly mediated by obesity.

    PubMed

    La Merrill, M A; Lind, P M; Salihovic, S; van Bavel, B; Lind, L

    2018-01-01

    The pesticide metabolite p,p'-DDE has been associated with left ventricular (LV) mass and known risk factors for LV hypertrophy in humans and in experimental models. We hypothesized that the associations of p,p'-DDE with LV hypertrophy risk factors, namely elevated glucose, adiposity and hypertension, mediate the association of p,p'-DDE with LV mass. p,p'-DDE was measured in plasma from 70-year-old subjects (n = 988) of the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS). When these subjects were 70-, 75- and 80- years old, LV characteristics were measured by echocardiography, while fasting glucose, body mass index (BMI) and blood pressure were assessed with standard clinical techniques. We found that p,p'-DDE levels were associated with increased fasting glucose, BMI, hypertension and LV mass in separate models adjusted for sex. Structural equation modeling revealed that the association between p,p'-DDE and LV mass was almost entirely mediated by BMI (70%), and also by hypertension (19%). The obesogenic effect of p,p'-DDE is a major determinant responsible for the association of p,p'-DDE with LV mass. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Peptide Mass Fingerprinting and N-Terminal Amino Acid Sequencing of Glycosylated Cysteine Protease of Euphorbia nivulia Buch.-Ham.

    PubMed Central

    Badgujar, Shamkant B.; Mahajan, Raghunath T.

    2013-01-01

    A new cysteine protease named Nivulian-II has been purified from the latex of Euphorbia nivulia Buch.-Ham. The apparent molecular mass of Nivulian-II is 43670.846 Da (MALDI TOF/MS). Peptide mass fingerprint analysis revealed peptide matches to Maturase K (Q52ZV1_9MAGN) of Banksia quercifolia. The N-terminal sequence (DFPPNTCCCICC) showed partial homology with those of other cysteine proteinases of biological origin. This is the first paper to characterize a Nivulian-II of E. nivulia latex with respect to amino acid sequencing. PMID:23476742

  4. STELLAR DIAMETERS AND TEMPERATURES. III. MAIN-SEQUENCE A, F, G, AND K STARS: ADDITIONAL HIGH-PRECISION MEASUREMENTS AND EMPIRICAL RELATIONS

    SciTech Connect

    Boyajian, Tabetha S.; Jones, Jeremy; White, Russel

    2013-07-01

    Based on CHARA Array measurements, we present the angular diameters of 23 nearby, main-sequence stars, ranging from spectral types A7 to K0, 5 of which are exoplanet host stars. We derive linear radii, effective temperatures, and absolute luminosities of the stars using Hipparcos parallaxes and measured bolometric fluxes. The new data are combined with previously published values to create an Angular Diameter Anthology of measured angular diameters to main-sequence stars (luminosity classes V and IV). This compilation consists of 125 stars with diameter uncertainties of less than 5%, ranging in spectral types from A to M. The large quantity ofmore » empirical data is used to derive color-temperature relations to an assortment of color indices in the Johnson (BVR{sub J} I{sub J} JHK), Cousins (R{sub C} I{sub C}), Kron (R{sub K} I{sub K}), Sloan (griz), and WISE (W{sub 3} W{sub 4}) photometric systems. These relations have an average standard deviation of {approx}3% and are valid for stars with spectral types A0-M4. To derive even more accurate relations for Sun-like stars, we also determined these temperature relations omitting early-type stars (T{sub eff} > 6750 K) that may have biased luminosity estimates because of rapid rotation; for this subset the dispersion is only {approx}2.5%. We find effective temperatures in agreement within a couple of percent for the interferometrically characterized sample of main-sequence stars compared to those derived via the infrared flux method and spectroscopic analysis.« less

  5. Development of a host blood meal database: de novo sequencing of hemoglobin from nine small mammals using mass spectrometry.

    PubMed

    Laskay, Ünige A; Burg, Jennifer; Kaleta, Erin J; Vilcins, Inger-Marie E; Telford Iii, Sam R; Barbour, Alan G; Wysocki, Vicki H

    2012-03-01

    We report the successful de novo sequencing of hemoglobin using a mass spectrometry-based approach combined with automatic data processing and manual validation for nine North American species with currently unsequenced genomes. The complete α and β chain of all nine mammalian hemoglobin samples used in this study were successfully sequenced. These sequences will be appended to the existing database containing all known hemoglobins to be used for identification of the mammalian host species that provided the last blood meal for the tick vector of Lyme disease, Ixodes scapularis.

  6. Global microbial carbonate proliferation after the end-Devonian mass extinction: Mainly controlled by demise of skeletal bioconstructors

    PubMed Central

    Yao, Le; Aretz, Markus; Chen, Jitao; Webb, Gregory E.; Wang, Xiangdong

    2016-01-01

    Microbial carbonates commonly flourished following mass extinction events. The end-Devonian (Hangenberg) mass extinction event is a first-order mass extinction on the scale of the ‘Big Five’ extinctions. However, to date, it is still unclear whether global microbial carbonate proliferation occurred after the Hangenberg event. The earliest known Carboniferous stromatolites on tidal flats are described from intertidal environments of the lowermost Tournaisian (Qianheishan Formation) in northwestern China. With other early Tournaisian microbe-dominated bioconstructions extensively distributed on shelves, the Qianheishan stromatolites support microbial carbonate proliferation after the Hangenberg extinction. Additional support comes from quantitative analysis of the abundance of microbe-dominated bioconstructions through the Famennian and early Tournaisian, which shows that they were globally distributed (between 40° latitude on both sides of the palaeoequator) and that their abundance increased distinctly in the early Tournaisian compared to the latest Devonian (Strunian). Comparison of variations in the relative abundance of skeleton- versus microbe-dominated bioconstructions across the Hangenberg and ‘Big Five’ extinctions suggests that changes in abundance of skeletal bioconstructors may play a first-order control on microbial carbonate proliferation during extinction transitions but that microbial proliferation is not a general necessary feature after mass extinctions. PMID:28009013

  7. Global microbial carbonate proliferation after the end-Devonian mass extinction: Mainly controlled by demise of skeletal bioconstructors.

    PubMed

    Yao, Le; Aretz, Markus; Chen, Jitao; Webb, Gregory E; Wang, Xiangdong

    2016-12-23

    Microbial carbonates commonly flourished following mass extinction events. The end-Devonian (Hangenberg) mass extinction event is a first-order mass extinction on the scale of the 'Big Five' extinctions. However, to date, it is still unclear whether global microbial carbonate proliferation occurred after the Hangenberg event. The earliest known Carboniferous stromatolites on tidal flats are described from intertidal environments of the lowermost Tournaisian (Qianheishan Formation) in northwestern China. With other early Tournaisian microbe-dominated bioconstructions extensively distributed on shelves, the Qianheishan stromatolites support microbial carbonate proliferation after the Hangenberg extinction. Additional support comes from quantitative analysis of the abundance of microbe-dominated bioconstructions through the Famennian and early Tournaisian, which shows that they were globally distributed (between 40° latitude on both sides of the palaeoequator) and that their abundance increased distinctly in the early Tournaisian compared to the latest Devonian (Strunian). Comparison of variations in the relative abundance of skeleton- versus microbe-dominated bioconstructions across the Hangenberg and 'Big Five' extinctions suggests that changes in abundance of skeletal bioconstructors may play a first-order control on microbial carbonate proliferation during extinction transitions but that microbial proliferation is not a general necessary feature after mass extinctions.

  8. Global microbial carbonate proliferation after the end-Devonian mass extinction: Mainly controlled by demise of skeletal bioconstructors

    NASA Astrophysics Data System (ADS)

    Yao, Le; Aretz, Markus; Chen, Jitao; Webb, Gregory E.; Wang, Xiangdong

    2016-12-01

    Microbial carbonates commonly flourished following mass extinction events. The end-Devonian (Hangenberg) mass extinction event is a first-order mass extinction on the scale of the ‘Big Five’ extinctions. However, to date, it is still unclear whether global microbial carbonate proliferation occurred after the Hangenberg event. The earliest known Carboniferous stromatolites on tidal flats are described from intertidal environments of the lowermost Tournaisian (Qianheishan Formation) in northwestern China. With other early Tournaisian microbe-dominated bioconstructions extensively distributed on shelves, the Qianheishan stromatolites support microbial carbonate proliferation after the Hangenberg extinction. Additional support comes from quantitative analysis of the abundance of microbe-dominated bioconstructions through the Famennian and early Tournaisian, which shows that they were globally distributed (between 40° latitude on both sides of the palaeoequator) and that their abundance increased distinctly in the early Tournaisian compared to the latest Devonian (Strunian). Comparison of variations in the relative abundance of skeleton- versus microbe-dominated bioconstructions across the Hangenberg and ‘Big Five’ extinctions suggests that changes in abundance of skeletal bioconstructors may play a first-order control on microbial carbonate proliferation during extinction transitions but that microbial proliferation is not a general necessary feature after mass extinctions.

  9. Genotyping-by-sequencing approach indicates geographic distance as the main factor affecting genetic structure and gene flow in Brazilian populations of Grapholita molesta (Lepidoptera, Tortricidae)

    PubMed Central

    Silva-Brandão, Karina Lucas; Silva, Oscar Arnaldo Batista Neto e; Brandão, Marcelo Mendes; Omoto, Celso; Sperling, Felix A H

    2015-01-01

    The oriental fruit moth Grapholita molesta is one of the major pests of stone and pome fruit species in Brazil. Here, we applied 1226 SNPs obtained by genotyping-by-sequencing to test whether host species associations or other factors such as geographic distance structured populations of this pest. Populations from the main areas of occurrence of G. molesta were sampled principally from peach and apple orchards. Three main clusters were recovered by neighbor-joining analysis, all defined by geographic proximity between sampling localities. Overall genetic structure inferred by a nonhierarchical amova resulted in a significant ΦST value = 0.19109. Here, we demonstrate for the first time that SNPs gathered by genotyping-by-sequencing can be used to infer genetic structure of a pest insect in Brazil; moreover, our results indicate that those markers are very informative even over a restricted geographic scale. We also demonstrate that host plant association has little effect on genetic structure among Brazilian populations of G. molesta; on the other hand, reduced gene flow promoted by geographic isolation has a stronger impact on population differentiation. PMID:26029261

  10. Viridans Group Streptococci clinical isolates: MALDI-TOF mass spectrometry versus gene sequence-based identification.

    PubMed

    Angeletti, Silvia; Dicuonzo, Giordano; Avola, Alessandra; Crea, Francesca; Dedej, Etleva; Vailati, Francesca; Farina, Claudio; De Florio, Lucia

    2015-01-01

    Viridans Group Streptococci (VGS) species-level identification is fundamental for patients management. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been used for VGS identification but discrimination within the Mitis group resulted difficult. In this study, VGS identifications with two MALDI-TOF instruments, the Biotyper (Bruker) and the VITEK MS (bioMérieux) have been compared to those derived from tuf, soda and rpoB genes sequencing. VGS isolates were clustered and a dendrogram constructed using the Biotyper 3.0 software (Bruker). RpoB gene sequencing resulted the most sensitive and specific molecular method for S. pneumonia identification and was used as reference method. The sensitivity and the specificity of the VITEK MS in S. pneumonia identification were 100%, while the Biotyper resulted less specific (92.4%). In non pneumococcal VGS strains, the group-level correlation between rpoB and the Biotyper was 100%, while the species-level correlation was 61% after database upgrading (than 37% before upgrading). The group-level correlation between rpoB and the VITEK MS was 100%, while the species-level correlation was 36% and increases at 69% if isolates identified as S. mitis/S. oralis are included. The less accurate performance of the VITEK MS in VGS identification within the Mitis group was due to the inability to discriminate between S. mitis and S. oralis. Conversely, the Biotyper, after the release of the upgraded database, was able to discriminate between the two species. In the dendrogram, VGS strains from the same group were grouped into the same cluster and had a good correspondence with the gene-based clustering reported by other authors, thus confirming the validity of the upgraded version of the database. Data from this study demonstrated that MALDI-TOF technique can represent a rapid and cost saving method for VGS identification even within the Mitis group but improvements of spectra database are

  11. Viridans Group Streptococci Clinical Isolates: MALDI-TOF Mass Spectrometry versus Gene Sequence-Based Identification

    PubMed Central

    Angeletti, Silvia; Dicuonzo, Giordano; Avola, Alessandra; Crea, Francesca; Dedej, Etleva; Vailati, Francesca; Farina, Claudio; De Florio, Lucia

    2015-01-01

    Viridans Group Streptococci (VGS) species-level identification is fundamental for patients management. Matrix-assisted laser desorption ionization—time of flight mass spectrometry (MALDI-TOF MS) has been used for VGS identification but discrimination within the Mitis group resulted difficult. In this study, VGS identifications with two MALDI-TOF instruments, the Biotyper (Bruker) and the VITEK MS (bioMérieux) have been compared to those derived from tuf, soda and rpoB genes sequencing. VGS isolates were clustered and a dendrogram constructed using the Biotyper 3.0 software (Bruker). RpoB gene sequencing resulted the most sensitive and specific molecular method for S. pneumonia identification and was used as reference method. The sensitivity and the specificity of the VITEK MS in S. pneumonia identification were 100%, while the Biotyper resulted less specific (92.4%). In non pneumococcal VGS strains, the group-level correlation between rpoB and the Biotyper was 100%, while the species-level correlation was 61% after database upgrading (than 37% before upgrading). The group-level correlation between rpoB and the VITEK MS was 100%, while the species-level correlation was 36% and increases at 69% if isolates identified as S. mitis/S. oralis are included. The less accurate performance of the VITEK MS in VGS identification within the Mitis group was due to the inability to discriminate between S. mitis and S. oralis. Conversely, the Biotyper, after the release of the upgraded database, was able to discriminate between the two species. In the dendrogram, VGS strains from the same group were grouped into the same cluster and had a good correspondence with the gene-based clustering reported by other authors, thus confirming the validity of the upgraded version of the database. Data from this study demonstrated that MALDI-TOF technique can represent a rapid and cost saving method for VGS identification even within the Mitis group but improvements of spectra database are

  12. A Quantitative Tool to Distinguish Isobaric Leucine and Isoleucine Residues for Mass Spectrometry-Based De Novo Monoclonal Antibody Sequencing

    NASA Astrophysics Data System (ADS)

    Poston, Chloe N.; Higgs, Richard E.; You, Jinsam; Gelfanova, Valentina; Hale, John E.; Knierman, Michael D.; Siegel, Robert; Gutierrez, Jesus A.

    2014-07-01

    De novo sequencing by mass spectrometry (MS) allows for the determination of the complete amino acid (AA) sequence of a given protein based on the mass difference of detected ions from MS/MS fragmentation spectra. The technique relies on obtaining specific masses that can be attributed to characteristic theoretical masses of AAs. A major limitation of de novo sequencing by MS is the inability to distinguish between the isobaric residues leucine (Leu) and isoleucine (Ile). Incorrect identification of Ile as Leu or vice versa often results in loss of activity in recombinant antibodies. This functional ambiguity is commonly resolved with costly and time-consuming AA mutation and peptide sequencing experiments. Here, we describe a set of orthogonal biochemical protocols, which experimentally determine the identity of Ile or Leu residues in monoclonal antibodies (mAb) based on the selectivity that leucine aminopeptidase shows for n-terminal Leu residues and the cleavage preference for Leu by chymotrypsin. The resulting observations are combined with germline frequencies and incorporated into a logistic regression model, called Predictor for Xle Sites (PXleS) to provide a statistical likelihood for the identity of Leu at an ambiguous site. We demonstrate that PXleS can generate a probability for an Xle site in mAbs with 96% accuracy. The implementation of PXleS precludes the expression of several possible sequences and, therefore, reduces the overall time and resources required to go from spectra generation to a biologically active sequence for a mAb when an Ile or Leu residue is in question.

  13. A quantitative tool to distinguish isobaric leucine and isoleucine residues for mass spectrometry-based de novo monoclonal antibody sequencing.

    PubMed

    Poston, Chloe N; Higgs, Richard E; You, Jinsam; Gelfanova, Valentina; Hale, John E; Knierman, Michael D; Siegel, Robert; Gutierrez, Jesus A

    2014-07-01

    De novo sequencing by mass spectrometry (MS) allows for the determination of the complete amino acid (AA) sequence of a given protein based on the mass difference of detected ions from MS/MS fragmentation spectra. The technique relies on obtaining specific masses that can be attributed to characteristic theoretical masses of AAs. A major limitation of de novo sequencing by MS is the inability to distinguish between the isobaric residues leucine (Leu) and isoleucine (Ile). Incorrect identification of Ile as Leu or vice versa often results in loss of activity in recombinant antibodies. This functional ambiguity is commonly resolved with costly and time-consuming AA mutation and peptide sequencing experiments. Here, we describe a set of orthogonal biochemical protocols, which experimentally determine the identity of Ile or Leu residues in monoclonal antibodies (mAb) based on the selectivity that leucine aminopeptidase shows for n-terminal Leu residues and the cleavage preference for Leu by chymotrypsin. The resulting observations are combined with germline frequencies and incorporated into a logistic regression model, called Predictor for Xle Sites (PXleS) to provide a statistical likelihood for the identity of Leu at an ambiguous site. We demonstrate that PXleS can generate a probability for an Xle site in mAbs with 96% accuracy. The implementation of PXleS precludes the expression of several possible sequences and, therefore, reduces the overall time and resources required to go from spectra generation to a biologically active sequence for a mAb when an Ile or Leu residue is in question.

  14. 16S rRNA Gene Sequencing, Multilocus Sequence Analysis, and Mass Spectrometry Identification of the Proposed New Species “Clostridium neonatale”

    PubMed Central

    Bouvet, Philippe; Ferraris, Laurent; Dauphin, Brunhilde; Popoff, Michel-Robert; Butel, Marie Jose

    2014-01-01

    In 2002, an outbreak of necrotizing enterocolitis in a Canadian neonatal intensive care unit was associated with a proposed novel species of Clostridium, “Clostridium neonatale.” To date, there are no data about the isolation, identification, or clinical significance of this species. Additionally, C. neonatale has not been formally classified as a new species, rendering its identification challenging. Indeed, the C. neonatale 16S rRNA gene sequence shows high similarity to another Clostridium species involved in neonatal necrotizing enterocolitis, Clostridium butyricum. By performing a polyphasic study combining phylogenetic analysis (16S rRNA gene sequencing and multilocus sequence analysis) and phenotypic characterization with mass spectrometry, we demonstrated that C. neonatale is a new species within the Clostridium genus sensu stricto, for which we propose the name Clostridium neonatale sp. nov. Now that the status of C. neonatale has been clarified, matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) can be used for better differential identification of C. neonatale and C. butyricum clinical isolates. This is necessary to precisely define the role and clinical significance of C. neonatale, a species that may have been misidentified and underrepresented during previous neonatal necrotizing enterocolitis studies. PMID:25232167

  15. Gas chromatographic-mass spectrometric identification of main metabolites of stanozolol in cattle after oral and subcutaneous administration.

    PubMed

    Ferchaud, V; Le Bizec, B; Montrade, M P; Maume, D; Monteau, F; André, F

    1997-08-01

    An analytical method has been developed in order to control the illegal use of stanozolol as growth promoter in livestock. The procedure was based on enzymatic hydrolysis, purification on a Clean Screen DAU column and derivatization with heptafluorobutyric anhydride prior to GC-MS analysis. This method allowed us to study the metabolism of stanozolol in cattle after oral and subcutaneous administrations. Urinary metabolites were identified by mass spectrometry. Stanozolol and 16-hydroxystanozolol were detected after oral administration, while 16-hydroxystanozolol and 4,16-dihydroxystanozolol were found after subcutaneous administration.

  16. DNA sequencing by delayed extraction-matrix-assisted laser desorption/ionization time of flight mass spectrometry.

    PubMed Central

    Roskey, M T; Juhasz, P; Smirnov, I P; Takach, E J; Martin, S A; Haff, L A

    1996-01-01

    Matrix-assisted laser desorption/ionization (MALDI) time of flight mass spectrometry was used to detect and order DNA fragments generated by Sanger dideoxy cycle sequencing. This was accomplished by improving the sensitivity and resolution of the MALDI method using a delayed ion extraction technique (DE-MALDI). The cycle sequencing chemistry was optimized to produce as much as 100 fmol of each specific dideoxy terminated fragment, generated from extension of a 13-base primer annealed on 40- and 50-base templates. Analysis of the resultant sequencing mixture by DE-MALDI identified the appropriate termination products. The technique provides a new non-gel-based method to sequence DNA which may ultimately have considerable speed advantages over traditional methodologies. Images Fig. 4 PMID:8643470

  17. The local mass density

    NASA Technical Reports Server (NTRS)

    Veeder, G. J.

    1974-01-01

    An improved mass-luminosity relation for faint main-sequence stars derived from recently revised masses for some faint double stars is presented. The total local mass density is increased to nearly 0.2 solar masses per cu pc. This estimate is as large as the mass density required by Oort's (1965) dynamical analysis of stellar motions perpendicular to the galactic plane if the mass is concentrated in a narrow layer.

  18. Fluid mass and thermal loading effects on the modal characteristics of space shuttle main engine liquid oxygen inlet splitter vanes

    NASA Technical Reports Server (NTRS)

    Panossian, H. V.; Boehnlein, J. J.

    1987-01-01

    An analysis and evaluation of experimental modal survey test data on the variations of modal characteristics induced by pressure and thermal loading events are presented. Extensive modal survey tests were carried out on a Space Shuttle Main Engine (SSME) test article using liquid nitrogen under cryogenic temperatures and high pressures. The results suggest that an increase of pressure under constant cryogenic temperature or a decrease of temperature under high pressure induces an upward shift of frequencies of various modes of the structures.

  19. Oligosaccharide sequences in Quillaja saponins by electrospray ionization ion trap multiple-stage mass spectrometry.

    PubMed

    Broberg, Susanna; Nord, Lars I; Kenne, Lennart

    2004-06-01

    Ten different samples with 13 previously identified saponin structures from Quillaja saponaria Molina were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMS(n)) in positive and negative ion modes. Both positive and negative ion mode MS(1)-MS(4) spectra were analyzed, showing that structural information on the two oligosaccharide parts in the saponin can be obtained from positive ion mode spectra whereas negative ion mode spectra mainly gave information on one of the oligosaccharide parts. Analysis of MS(1)-MS(4) spectra identified useful key fragment ions important for the structural elucidation of Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from MS(1)-MS(3) spectra was constructed for the identification of structural elements in the saponin. Peak intensity ratios in MS(3) spectra were found to be correlated with structural features of the investigated saponins and are therefore of value for the identification of terminal monosaccharide residues. Copyright 2004 John Wiley & Sons, Ltd.

  20. Rapid and deep proteomes by faster sequencing on a benchtop quadrupole ultra-high-field Orbitrap mass spectrometer.

    PubMed

    Kelstrup, Christian D; Jersie-Christensen, Rosa R; Batth, Tanveer S; Arrey, Tabiwang N; Kuehn, Andreas; Kellmann, Markus; Olsen, Jesper V

    2014-12-05

    Shotgun proteomics is a powerful technology for global analysis of proteins and their post-translational modifications. Here, we investigate the faster sequencing speed of the latest Q Exactive HF mass spectrometer, which features an ultra-high-field Orbitrap mass analyzer. Proteome coverage is evaluated by four different acquisition methods and benchmarked across three generations of Q Exactive instruments (ProteomeXchange data set PXD001305). We find the ultra-high-field Orbitrap mass analyzer to be capable of attaining a sequencing speed above 20 Hz, and it routinely exceeds 10 peptide spectrum matches per second or up to 600 new peptides sequenced per gradient minute. We identify 4400 proteins from 1 μg of HeLa digest using a 1 h gradient, which is an approximately 30% improvement compared to that with previous instrumentation. In addition, we show that very deep proteome coverage can be achieved in less than 24 h of analysis time by offline high-pH reversed-phase peptide fractionation, from which we identify more than 140,000 unique peptide sequences. This is comparable to state-of-the-art multiday, multienzyme efforts. Finally, the acquisition methods are evaluated for single-shot phosphoproteomics, where we identify 7600 unique HeLa phosphopeptides in one gradient hour and find the quality of fragmentation spectra to be more important than quantity for accurate site assignment.

  1. Microwave-assisted acid and base hydrolysis of intact proteins containing disulfide bonds for protein sequence analysis by mass spectrometry.

    PubMed

    Reiz, Bela; Li, Liang

    2010-09-01

    Controlled hydrolysis of proteins to generate peptide ladders combined with mass spectrometric analysis of the resultant peptides can be used for protein sequencing. In this paper, two methods of improving the microwave-assisted protein hydrolysis process are described to enable rapid sequencing of proteins containing disulfide bonds and increase sequence coverage, respectively. It was demonstrated that proteins containing disulfide bonds could be sequenced by MS analysis by first performing hydrolysis for less than 2 min, followed by 1 h of reduction to release the peptides originally linked by disulfide bonds. It was shown that a strong base could be used as a catalyst for microwave-assisted protein hydrolysis, producing complementary sequence information to that generated by microwave-assisted acid hydrolysis. However, using either acid or base hydrolysis, amide bond breakages in small regions of the polypeptide chains of the model proteins (e.g., cytochrome c and lysozyme) were not detected. Dynamic light scattering measurement of the proteins solubilized in an acid or base indicated that protein-protein interaction or aggregation was not the cause of the failure to hydrolyze certain amide bonds. It was speculated that there were some unknown local structures that might play a role in preventing an acid or base from reacting with the peptide bonds therein. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  2. Extended Main-sequence Turn-offs in Intermediate-age Star Clusters: Stellar Rotation Diminishes, but Does Not Eliminate, Age Spreads

    SciTech Connect

    Goudfrooij, Paul; Correnti, Matteo; Girardi, Léo, E-mail: goudfroo@stsci.edu

    2017-09-01

    Extended main-sequence turn-off (eMSTO) regions are a common feature in color–magnitude diagrams of young- and intermediate-age star clusters in the Magellanic Clouds. The nature of eMSTOs remains debated in the literature. The currently most popular scenarios are extended star formation activity and ranges of stellar rotation rates. Here we study details of differences in main-sequence turn-off (MSTO) morphology expected from spreads in age versus spreads in rotation rates, using Monte Carlo simulations with the Geneva syclist isochrone models that include the effects of stellar rotation. We confirm a recent finding of Niederhofer et al. that a distribution of stellar rotationmore » velocities yields an MSTO extent that is proportional to the cluster age, as observed. However, we find that stellar rotation yields MSTO crosscut widths that are generally smaller than observed ones at a given age. We compare the simulations with high-quality Hubble Space Telescope data of NGC 1987 and NGC 2249, which are the two only relatively massive star clusters with an age of ∼1 Gyr for which such data is available. We find that the distribution of stars across the eMSTOs of these clusters cannot be explained solely by a distribution of stellar rotation velocities, unless the orientations of rapidly rotating stars are heavily biased toward an equator-on configuration. Under the assumption of random viewing angles, stellar rotation can account for ∼60% and ∼40% of the observed FWHM widths of the eMSTOs of NGC 1987 and NGC 2249, respectively. In contrast, a combination of distributions of stellar rotation velocities and stellar ages fits the observed eMSTO morphologies very well.« less

  3. Numerical Investigation of the Main Characteristics of Heat and Mass Transfer while Heating the Heterogeneous Water Droplet in the Hot Gases

    NASA Astrophysics Data System (ADS)

    Piskunov, Maxim V.; Shcherbinina, Anastasia A.; Vysokomornaya, Olga V.

    2016-02-01

    The processes of heat and evaporation of heterogeneous water droplet with solid (by the example of carbon) inclusion in hot (from 800 K to 1500 K) gases were investigated by the developed models of heat and mass transfer. We defined the limited conditions, characteristics of the droplet and the gas medium which are sufficient for implementing the "explosive" destruction of heterogeneous droplet due to intensive vaporization on an inner interface, and intensive evaporation of liquid from an external (free) droplet surface. The values of the main characteristic of the process (period from start of heating to "explosive" destruction) obtained in response to using various heat and mass transfer models were compared.

  4. Constraining the low-mass Slope of the star formation sequence at 0.5 < z < 2.5

    SciTech Connect

    Whitaker, Katherine E.; Henry, Alaina; Rigby, Jane R.

    2014-11-10

    We constrain the slope of the star formation rate (SFR; log Ψ) to stellar mass (log M {sub *}) relation down to log (M {sub *}/M {sub ☉}) = 8.4 (log (M {sub *}/M {sub ☉}) = 9.2) at z = 0.5 (z = 2.5) with a mass-complete sample of 39,106 star-forming galaxies selected from the 3D-HST photometric catalogs, using deep photometry in the CANDELS fields. For the first time, we find that the slope is dependent on stellar mass, such that it is steeper at low masses (log Ψ∝log M {sub *}) than at high masses (log Ψ∝(0.3-0.6)log Mmore » {sub *}). These steeper low-mass slopes are found for three different star formation indicators: the combination of the ultraviolet (UV) and infrared (IR), calibrated from a stacking analysis of Spitzer/MIPS 24 μm imaging; β-corrected UV SFRs; and Hα SFRs. The normalization of the sequence evolves differently in distinct mass regimes as well: for galaxies less massive than log (M {sub *}/M {sub ☉}) < 10 the specific SFR (Ψ/M {sub *}) is observed to be roughly self-similar with Ψ/M {sub *}∝(1 + z){sup 1.9}, whereas more massive galaxies show a stronger evolution with Ψ/M {sub *}∝(1 + z){sup 2.2-3.5} for log (M {sub *}/M {sub ☉}) = 10.2-11.2. The fact that we find a steep slope of the star formation sequence for the lower mass galaxies will help reconcile theoretical galaxy formation models with the observations.« less

  5. Identification and verification of hybridoma-derived monoclonal antibody variable region sequences using recombinant DNA technology and mass spectrometry.

    PubMed

    Babrak, Lmar; McGarvey, Jeffery A; Stanker, Larry H; Hnasko, Robert

    2017-10-01

    Antibody engineering requires the identification of antigen binding domains or variable regions (VR) unique to each antibody. It is the VR that define the unique antigen binding properties and proper sequence identification is essential for functional evaluation and performance of recombinant antibodies (rAb). This determination can be achieved by sequence analysis of immunoglobulin (Ig) transcripts obtained from a monoclonal antibody (MAb) producing hybridoma and subsequent expression of a rAb. However the polyploidy nature of a hybridoma cell often results in the added expression of aberrant immunoglobulin-like transcripts or even production of anomalous antibodies which can confound production of rAb. An incorrect VR sequence will result in a non-functional rAb and de novo assembly of Ig primary structure without a sequence map is challenging. To address these problems, we have developed a methodology which combines: 1) selective PCR amplification of VR from both the heavy and light chain IgG from hybridoma, 2) molecular cloning and DNA sequence analysis and 3) tandem mass spectrometry (MS/MS) on enzyme digests obtained from the purified IgG. Peptide analysis proceeds by evaluating coverage of the predicted primary protein sequence provided by the initial DNA maps for the VR. This methodology serves to both identify and verify the primary structure of the MAb VR for production as rAb. Published by Elsevier Ltd.

  6. Mass balances of mercury and nitrogen in burned and unburned forested watersheds at Acadia National Park, Maine, USA.

    PubMed

    Nelson, S J; Johnson, K B; Kahl, J S; Haines, T A; Fernandez, I J

    2007-03-01

    Precipitation and streamwater samples were collected from 16 November 1999 to 17 November 2000 in two watersheds at Acadia National Park, Maine, and analyzed for mercury (Hg) and dissolved inorganic nitrogen (DIN, nitrate plus ammonium). Cadillac Brook watershed burned in a 1947 fire that destroyed vegetation and soil organic matter. We hypothesized that Hg deposition would be higher at Hadlock Brook (the reference watershed, 10.2 microg/m(2)/year) than Cadillac (9.4 microg/m(2)/year) because of the greater scavenging efficiency of the softwood vegetation in Hadlock. We also hypothesized the Hg and DIN export from Cadillac Brook would be lower than Hadlock Brook because of elemental volatilization during the fire, along with subsequently lower rates of atmospheric deposition in a watershed with abundant bare soil and bedrock, and regenerating vegetation. Consistent with these hypotheses, Hg export was lower from Cadillac Brook watershed (0.4 microg/m(2)/year) than from Hadlock Brook watershed (1.3 microg/m(2)/year). DIN export from Cadillac Brook (11.5 eq/ha/year) was lower than Hadlock Brook (92.5 eq/ha/year). These data show that approximately 50 years following a wildfire there was lower atmospheric deposition due to changes in forest species composition, lower soil pools, and greater ecosystem retention for both Hg and DIN.

  7. Mass balances of mercury and nitrogen in burned and unburned forested watersheds at Acadia National Park, Maine, USA

    USGS Publications Warehouse

    Nelson, S.J.; Johnson, K.B.; Kahl, J.S.; Haines, T.A.; Fernandez, I.J.

    2007-01-01

    Precipitation and streamwater samples were collected from 16 November 1999 to 17 November 2000 in two watersheds at Acadia National Park, Maine, and analyzed for mercury (Hg) and dissolved inorganic nitrogen (DIN, nitrate plus ammonium). Cadillac Brook watershed burned in a 1947 fire that destroyed vegetation and soil organic matter. We hypothesized that Hg deposition would be higher at Hadlock Brook (the reference watershed, 10.2 ??g/m2/year) than Cadillac (9.4 ??g/m2/year) because of the greater scavenging efficiency of the softwood vegetation in Hadlock. We also hypothesized the Hg and DIN export from Cadillac Brook would be lower than Hadlock Brook because of elemental volatilization during the fire, along with subsequently lower rates of atmospheric deposition in a watershed with abundant bare soil and bedrock, and regenerating vegetation. Consistent with these hypotheses, Hg export was lower from Cadillac Brook watershed (0.4 ??g/m2/year) than from Hadlock Brook watershed (1.3 ??g/m2/year). DIN export from Cadillac Brook (11.5 eq/ ha/year) was lower than Hadlock Brook (92.5 eq/ha/year). These data show that ??50 years following a wildfire there was lower atmospheric deposition due to changes in forest species composition, lower soil pools, and greater ecosystem retention for both Hg and DIN. ?? Springer Science + Business Media B.V. 2006.

  8. Reprint of "Identification of staphylococcal species based on variations in protein sequences (mass spectrometry) and DNA sequence (sodA microarray)".

    PubMed

    Kooken, Jennifer; Fox, Karen; Fox, Alvin; Altomare, Diego; Creek, Kim; Wunschel, David; Pajares-Merino, Sara; Martínez-Ballesteros, Ilargi; Garaizar, Javier; Oyarzabal, Omar; Samadpour, Mansour

    2014-01-01

    This report is among the first using sequence variation in newly discovered protein markers for staphylococcal (or indeed any other bacterial) speciation. Variation, at the DNA sequence level, in the sodA gene (commonly used for staphylococcal speciation) provided excellent correlation. Relatedness among strains was also assessed using protein profiling using microcapillary electrophoresis and pulsed field electrophoresis. A total of 64 strains were analyzed including reference strains representing the 11 staphylococcal species most commonly isolated from man (Staphylococcus aureus and 10 coagulase negative species [CoNS]). Matrix assisted time of flight ionization/ionization mass spectrometry (MALDI TOF MS) and liquid chromatography-electrospray ionization tandem mass spectrometry (LC ESI MS/MS) were used for peptide analysis of proteins isolated from gel bands. Comparison of experimental spectra of unknowns versus spectra of peptides derived from reference strains allowed bacterial identification after MALDI TOF MS analysis. After LC-MS/MS analysis of gel bands bacterial speciation was performed by comparing experimental spectra versus virtual spectra using the software X!Tandem. Finally LC-MS/MS was performed on whole proteomes and data analysis also employing X!tandem. Aconitate hydratase and oxoglutarate dehydrogenase served as marker proteins on focused analysis after gel separation. Alternatively on full proteomics analysis elongation factor Tu generally provided the highest confidence in staphylococcal speciation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. A novel tandem mass spectrometry method for first-line screening of mainly beta-thalassemia from dried blood spots.

    PubMed

    Yu, Chaowen; Huang, Shuodan; Wang, Ming; Zhang, Juan; Liu, Hao; Yuan, Zhaojian; Wang, Xingbin; He, Xiaoyan; Wang, Jie; Zou, Lin

    2017-02-10

    Traditional methods for thalassemia screening are time-consuming and easily affected by cell hemolysis or hemoglobin degradation in stored blood samples. Tandem mass spectrometry (MS/MS) proved to be an effective technology for sickle cell disorders (SCD) screening. Here, we developed a novel MS/MS method for β-thalassemia screening from dried blood spots (DBS). Stable isotopic-labeled peptides were used as internal standards for quantification and calculation of the α:β-globin ratios. We used the α:β-globin ratio cutoffs to differentiate between normal individuals and patients with thalassemia. About 781 patients and 300 normal individuals were analyzed. The α:β-globin ratios showed significant difference between normal and β-thalassemia patients (P<0.01), particularly when the disease was homozygous or double heterozygous with another α- or β-thalassemia mutation. In the parallel study, all cases screened for suspected thalassemia from six hundred DBS samples by using this MS/MS method were successfully confirmed by genotyping. The intra-assay and inter-assay CVs of the ratios ranged from 2.4% to 3.9% and 4.7% to 7.1%, and there was no significant sample carryover or matrix effect for this MS/MS method. Combined with SCD screening, this MS/MS method could be used as a first-line screening assay for both structural and expression abnormalities of human hemoglobin. Traditional methods for thalassemia screening were depending on the structural integrity of tetramers and could be affected by hemolysis and degradation of whole blood samples, especially when stored. We used proteospecific peptides produced by the tryptic digestion of each globin to evaluate the production ratio between α- and β-globin chains, which turned out to be quite stable even when stored for more than two months. Though most of the peptides were specific to α-globin or β-globin, we only chose four most informative peptides and its stable isotopic-labeled peptides as internal

  10. A Search for Coronal Emission at the Bottom of the Main-Sequence: Stars and Brown Dwarf Candidates with Spectral Types Later than M7 and the Rotation-Activity Relation

    NASA Technical Reports Server (NTRS)

    Stringfellow, Guy

    2004-01-01

    This program intended to test whether the lowest mass stars at the bottom end of the main sequence and the lower mass brown dwarfs have coronae. If they have coronae, what are the coronal characteristics and what drives them? In the classical dynamo picture, the closed magnetic loop structure is generated near the boundary of the convective envelope and the radiative core. Stars with mass below 0.30 Msun however are fully convective, and the nature of the dynamo responsible for the generation of the coronae in this regime is poorly understood. Previous results from the ROSAT mission (e.g., Fleming et al. 1993, 1995; Schmitt et al. 1995) had confirmed three very important characteristics of M-star coronae: (1) a very high percentage of all M dwarfs have coronae (of order 85% in the local 7 pc sample), (2) those M dwarfs showing high chromospheric activity, such as having the Balmer series in emission or large/numerous optical flaring, indeed exhibit the highest coronal activity, and (3) that the maximum saturation boundary in X-ray luminosity, which amounts to 0.0001-0.001 for Lx/Lbol for the dMe stars, extends down to the current detection limit, through spectral types M7. It was likely that the incompleteness noted for result (1) above was simply a detection limit problem; for more distant sources, the X-ray fainter dM stars will drop below detection thresholds before the more X-ray luminous dMe stars. The latest stars for which direct detection of the corona had been successful were of spectral type dM7 (e.g., VB8, LHS 3003). This program proposed to obtain ROSAT HRI observations for a large number of the coolest known (at that time) stars at the bottom of the main-sequence, which had spectral types of M9 or later. Three stars were approved for observations with ROSAT-HRI totaling 180 ksec. The goal was to obtain X-ray detections or low upper limits for the three approved stars.

  11. Comment on "Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry".

    PubMed

    Buckley, Mike; Walker, Angela; Ho, Simon Y W; Yang, Yue; Smith, Colin; Ashton, Peter; Oates, Jane Thomas; Cappellini, Enrico; Koon, Hannah; Penkman, Kirsty; Elsworth, Ben; Ashford, Dave; Solazzo, Caroline; Andrews, Phillip; Strahler, John; Shapiro, Beth; Ostrom, Peggy; Gandhi, Hasand; Miller, Webb; Raney, Brian; Zylber, Maria Ines; Gilbert, M Thomas P; Prigodich, Richard V; Ryan, Michael; Rijsdijk, Kenneth F; Janoo, Anwar; Collins, Matthew J

    2008-01-04

    We used authentication tests developed for ancient DNA to evaluate claims by Asara et al. (Reports, 13 April 2007, p. 280) of collagen peptide sequences recovered from mastodon and Tyrannosaurus rex fossils. Although the mastodon samples pass these tests, absence of amino acid composition data, lack of evidence for peptide deamidation, and association of alpha1(I) collagen sequences with amphibians rather than birds suggest that T. rex does not.

  12. Identification of single amino acid substitutions (SAAS) in neuraminidase from influenza a virus (H1N1) via mass spectrometry analysis coupled with de novo peptide sequencing.

    PubMed

    Peng, Qisheng; Wang, Zijian; Wu, Donglin; Li, Xiaoou; Liu, Xiaofeng; Sun, Wanchun; Liu, Ning

    2016-08-01

    Amino acid substitutions in the neuraminidase of the influenza virus are the main cause of the emergence of resistance to zanamivir or oseltamivir during seasonal influenza treatment; they are the result of non-synonymous mutations in the viral genome that can be successfully detected by polymer chain reaction (PCR)-based approaches. There is always an urgent need to detect variation in amino acid sequences directly at the protein level. Mass spectrometry coupled with de novo sequencing has been explored as an alternative and straightforward strategy for detecting amino acid substitutions, as well - this approach is the primary focus of the present study. Influenza virus (A/Puerto Rico/8/1934 H1N1) propagated in embryonated chicken eggs was purified by ultracentrifugation, followed by PNGase F treatment. The deglycosylated virion was lysed and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The gel band corresponding to neuraminidase was picked up and subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. LC-MS/MS analyses, coupled with manual de novo sequencing, allowed the determination of three amino acid substitutions: R346K, S349 N, and S370I/L, in the neuraminidase from the influenza virus (A/Puerto Rico/8/1934 H1N1), which were located in three mutated peptides of the neuraminidase: YGNGVWIGK, TKNHSSR, and PNGWTETDI/LK, respectively. We found that the amino acid substitutions in the proteins of RNA viruses (including influenza A virus) resulting from non-synonymous gene mutations can indeed be directly analyzed via mass spectrometry, and that manual interpretation of the MS/MS data may be beneficial. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Nutrients and water masses in the Gulf of Maine - Georges Bank region: Variability and importance to blooms of the toxic dinoflagellate Alexandrium fundyense

    PubMed Central

    Townsend, D.W.; McGillicuddy, D.J.; Thomas, M.A.; Rebuck, N.R.

    2015-01-01

    We report here the results of ten oceanographic survey cruises carried out in the Gulf of Maine - Georges Bank region of the Northwest Atlantic during the late spring to summer period in 2007, 2008 and 2010, for which we examine and characterize relationships among dissolved inorganic nutrient fields, water mass dynamics and cell densities of the toxic dinoflagellate Alexandrium fundyense. Nutrients are supplied to continental shelf waters of the Gulf of Maine - Georges Bank region by inflows of deep offshore water masses; once in the Gulf they are transported with the residual circulation and mix with surface waters, both in the Gulf and on the Bank. Those fluxes of offshore water masses and their nutrient loads are the major source of nutrients for phytoplankton production in the region, including annual blooms of A. fundyense in the Gulf and on Georges Bank. This much is already known. We suggest here that the locations and magnitude of A. fundyense blooms are controlled in part by variable nutrient fluxes to the interior Gulf of Maine from offshore, and, those interior Gulf of Maine waters are, in turn, the main nutrient source to Georges Bank, which are brought onto the Bank by tidal pumping on the Northern Flank. We present evidence that nitrate is the initial form of nitrogenous nutrient for A. fundyense blooms, but it is quickly depleted to limiting concentrations of less than 0.5 μM, at which time continued growth and maintenance of the population is likely fueled by recycled ammonium. We also show that phosphate may be the limiting nutrient over much of Georges Bank in summer, allowing recycled ammonium concentrations to increase. Our temperature-salinity analyses reveal spatial and temporal (seasonal and interannual) variability in the relative proportions of two deep source waters that enter the Gulf of Maine at depth through the Northeast Channel: Warm Slope Water (WSW) and Labrador Slope Water (LSW). Those two source waters are known to vary in their

  14. Nutrients and water masses in the Gulf of Maine-Georges Bank region: Variability and importance to blooms of the toxic dinoflagellate Alexandrium fundyense

    NASA Astrophysics Data System (ADS)

    Townsend, D. W.; McGillicuddy, D. J.; Thomas, M. A.; Rebuck, N. D.

    2014-05-01

    We report here the results of ten oceanographic survey cruises carried out in the Gulf of Maine-Georges Bank region of the Northwest Atlantic during the late spring to summer period in 2007, 2008 and 2010, for which we examine and characterize relationships among dissolved inorganic nutrient fields, water mass dynamics and cell densities of the toxic dinoflagellate Alexandrium fundyense. Nutrients are supplied to continental shelf waters of the Gulf of Maine-Georges Bank region by inflows of deep offshore water masses; once in the Gulf they are transported with the residual circulation and mix with surface waters, both in the Gulf and on the Bank. Those fluxes of offshore water masses and their nutrient loads are the major source of nutrients for phytoplankton production in the region, including annual blooms of A. fundyense in the Gulf and on Georges Bank. This much is already known. We suggest here that the locations and magnitude of A. fundyense blooms are controlled in part by variable nutrient fluxes to the interior Gulf of Maine from offshore, and, those interior Gulf of Maine waters are, in turn, the main nutrient source to Georges Bank, which are brought onto the Bank by tidal pumping on the Northern Flank. We present evidence that nitrate is the initial form of nitrogenous nutrient for A. fundyense blooms, but it is quickly depleted to limiting concentrations of less than 0.5 μM, at which time continued growth and maintenance of the population is likely fueled by recycled ammonium. We also show that phosphate may be the limiting nutrient over much of Georges Bank in summer, allowing recycled ammonium concentrations to increase. Our temperature-salinity analyses reveal spatial and temporal (seasonal and interannual) variability in the relative proportions of two deep source waters that enter the Gulf of Maine at depth through the Northeast Channel: Warm Slope Water (WSW) and Labrador Slope Water (LSW). Those two source waters are known to vary in their

  15. Nutrients and water masses in the Gulf of Maine - Georges Bank region: Variability and importance to blooms of the toxic dinoflagellate Alexandrium fundyense.

    PubMed

    Townsend, D W; McGillicuddy, D J; Thomas, M A; Rebuck, N R

    2014-05-01

    We report here the results of ten oceanographic survey cruises carried out in the Gulf of Maine - Georges Bank region of the Northwest Atlantic during the late spring to summer period in 2007, 2008 and 2010, for which we examine and characterize relationships among dissolved inorganic nutrient fields, water mass dynamics and cell densities of the toxic dinoflagellate Alexandrium fundyense . Nutrients are supplied to continental shelf waters of the Gulf of Maine - Georges Bank region by inflows of deep offshore water masses; once in the Gulf they are transported with the residual circulation and mix with surface waters, both in the Gulf and on the Bank. Those fluxes of offshore water masses and their nutrient loads are the major source of nutrients for phytoplankton production in the region, including annual blooms of A. fundyense in the Gulf and on Georges Bank. This much is already known. We suggest here that the locations and magnitude of A. fundyense blooms are controlled in part by variable nutrient fluxes to the interior Gulf of Maine from offshore, and, those interior Gulf of Maine waters are, in turn, the main nutrient source to Georges Bank, which are brought onto the Bank by tidal pumping on the Northern Flank. We present evidence that nitrate is the initial form of nitrogenous nutrient for A. fundyense blooms, but it is quickly depleted to limiting concentrations of less than 0.5 μM, at which time continued growth and maintenance of the population is likely fueled by recycled ammonium. We also show that phosphate may be the limiting nutrient over much of Georges Bank in summer, allowing recycled ammonium concentrations to increase. Our temperature-salinity analyses reveal spatial and temporal (seasonal and interannual) variability in the relative proportions of two deep source waters that enter the Gulf of Maine at depth through the Northeast Channel: Warm Slope Water (WSW) and Labrador Slope Water (LSW). Those two source waters are known to vary in

  16. Multilocus sequence typing of Australian Streptococcus suis type 2 by MALDI-TOF mass spectrometry analysis of PCR amplicons.

    PubMed

    Groves, Mitchell D; Jordan, David; Chapman, Toni A; Jassim, Rafat Al

    2015-06-12

    Streptococcus suis serotype 2 is a ubiquitous pathogen of swine and is known to cause severe disease in humans. Multilocus sequence typing (MLST) is ideal for characterising this organism because it permits isolates to be compared on a national and international scale. A novel approach to MLST using matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MS-MLST) provides a more rapid alternative to dideoxy sequencing. This study used MS-MLST to define the multilocus sequence types (STs) present among a collection of Australian S. suis type 2, and thus, delivered a basis for comparison of Australian isolates with international strains already well characterised for virulence attributes. A collection of 45 isolates recovered from infected humans (n=3) and diseased pigs (n=42) was genotyped using MS-MLST and conventional MLST. Both methods were 100% concordant in their classification of sequence types (STs), although MS-MLST permitted much quicker analysis of sequence data. The collection contained ST25 (n=31), ST1 (n=10), ST28 (n=3) and ST369 (n=1). These results are consistent with the population structure of S. suis type 2 observed in diseased pigs and humans in Canada and the United Kingdom. MS-MLST may have utility for studying the population structure and epidemiology of S. suis in countries where the diversity of S. suis is greater and human disease is more common. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

  17. STELLAR BORON ABUNDANCES NEAR THE MAIN-SEQUENCE TURNOFF OF THE OPEN CLUSTER NGC 3293 AND IMPLICATIONS FOR THE EFFICIENCY OF ROTATIONALLY DRIVEN MIXING IN STELLAR ENVELOPES

    SciTech Connect

    Proffitt, Charles R.; Lennon, Daniel J.; Langer, Norbert

    2016-06-10

    Spectra from the Hubble Space Telescope Cosmic Origins Spectrograph and the Space Telescope Imaging Spectrograph covering the B iii resonance line have been obtained for 10 early-B stars near the turnoff of the young Galactic open cluster NGC 3293. This is the first sample of boron abundance determinations in a single, clearly defined population of early-B stars that also covers a substantial range of projected rotational velocities. In most of these stars we detect partial depletion of boron at a level consistent with that expected for rotational mixing in single stars, but inconsistent with expectations for depletion from close binarymore » evolution. However, our results do suggest that the efficiency of rotational mixing is at or slightly below the low end of the range predicted by the available theoretical calculations. The two most luminous targets observed have a very large boron depletion and may be the products of either binary interactions or post-main-sequence evolution.« less

  18. High Resolution X-ray Spectroscopy and Star Formation: HETG Observations of the Pre-Main Sequence Stellar Cluster IC 348

    NASA Astrophysics Data System (ADS)

    Principe, David; Huenemoerder, David P.; Schulz, Norbert; Kastner, Joel H.; Weintraub, David; Preibisch, Thomas

    2018-01-01

    We present Chandra High Energy Transmission Grating (HETG) observations of the ∼3 Myr old pre-main sequence (pre-MS) stellar cluster IC 348. With 400-500 cluster members at a distance of ∼300 pc, IC 348 is an ideal target to observe a large number of X-ray sources in a single pointing and is thus an extremely efficient use of Chandra-HETG. High resolution X-ray spectroscopy offers a means to investigate detailed spectral characteristic of X-ray emitting plasmas and their surrounding environments. We present preliminary results where we compare X-ray spectral signatures (e.g., luminosity, temperature, column density, abundance) of the X-ray brightest pre-MS stars in IC 348 with spectral type, multiwavelength signatures of accretion, and the presence of circumstellar disks at multiple stages of pre-MS stellar evolution. Assuming all IC 348 members formed from the same primordial molecular cloud, any disparity between coronal abundances of individual members, as constrained by the identification and strength of emission lines, will constrain the source(s) of coronal chemical evolution at a stage of pre-MS evolution vital to the formation of planets.

  19. RADIO PROPERTIES OF THE BAT AGNs: THE FIR–RADIO RELATION, THE FUNDAMENTAL PLANE, AND THE MAIN SEQUENCE OF STAR FORMATION

    SciTech Connect

    Smith, Krista Lynne; Mushotzky, Richard F.; Vogel, Stuart

    2016-12-01

    We conducted 22 GHz 1″ JVLA imaging of 70 radio-quiet active galactic nuclei (AGNs) from the Swift -BAT survey. We find radio cores in all but three objects. The radio morphologies of the sample fall into three groups: compact and core-dominated, extended, and jet-like. We spatially decompose each image into core flux and extended flux, and compare the extended radio emission with that predicted from previous Herschel observations using the canonical FIR–radio relation. After removing the AGN contribution to the FIR and radio flux densities, we find that the relation holds remarkably well despite the potentially different star formation physics inmore » the circumnuclear environment. We also compare our core radio flux densities with predictions of coronal models and scale-invariant jet models for the origin of radio emission in radio-quiet AGNs, and find general consistency with both models. However, we find that the L {sub R}/ L {sub X} relation does not distinguish between star formation and non-relativistic AGN-driven outflows as the origin of radio emission in radio-quiet AGNs. Finally, we examine where objects with different radio morphologies fall in relation to the main sequence (MS) of star formation, and conclude that those AGNs that fall below the MS, as X-ray selected AGNs have been found to do, have core-dominated or jet-like 22 GHz morphologies.« less

  20. Sequence Elucidation of an Unknown Cyclic Peptide of High Doping Potential by ETD and CID Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Guan, Fuyu; Uboh, Cornelius E.; Soma, Lawrence R.; Rudy, Jeffrey

    2011-04-01

    Identification of an unknown substance without any information remains a daunting challenge despite advances in chemistry and mass spectrometry. However, an unknown cyclic peptide in a sample with very limited volume seized at a Pennsylvania racetrack has been successfully identified. The unknown sample was determined by accurate mass measurements to contain a small unknown peptide as the major component. Collision-induced dissociation (CID) of the unknown peptide revealed the presence of Lys (not Gln, by accurate mass), Phe, and Arg residues, and absence of any y-type product ion. The latter, together with the tryptic digestion results of the unusual deamidation and absence of any tryptic cleavage, suggests a cyclic structure for the peptide. Electron-transfer dissociation (ETD) of the unknown peptide indicated the presence of Gln (not Lys, by the unusual deamidation), Phe, and Arg residues and their connectivity. After all the results were pieced together, a cyclic tetrapeptide, cyclo[Arg-Lys-N(C6H9)Gln-Phe], is proposed for the unknown peptide. Observations of different amino acid residues from CID and ETD experiments for the peptide were interpreted by a fragmentation pathway proposed, as was preferential CID loss of a Lys residue from the peptide. ETD was used for the first time in sequencing of a cyclic peptide; product ions resulting from ETD of the peptide identified were categorized into two types and named pseudo-b and pseudo-z ions that are important for sequencing of cyclic peptides. The ETD product ions were interpreted by fragmentation pathways proposed. Additionally, multi-stage CID mass spectrometry cannot provide complete sequence information for cyclic peptides containing adjacent Arg and Lys residues. The identified cyclic peptide has not been documented in the literature, its pharmacological effects are unknown, but it might be a "designer" drug with athletic performance-enhancing effects.

  1. Comment on "Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry".

    PubMed

    Pevzner, Pavel A; Kim, Sangtae; Ng, Julio

    2008-08-22

    Asara et al. (Reports, 13 April 2007, p. 280) reported sequencing of Tyrannosaurus rex proteins and used them to establish the evolutionary relationships between birds and dinosaurs. We argue that the reported T. rex peptides may represent statistical artifacts and call for complete data release to enable experimental and computational verification of their findings.

  2. A simplified soil extraction sequence to monitor the main and trace element speciation in soil after compost and mineral fertilizer additions upon the composition of wheat grains

    NASA Astrophysics Data System (ADS)

    Sager, Manfred; Erhart, Eva

    2016-04-01

    High quality biological waste treatment aims at producing compost in order to maintain a clean environment and to sustain soil organic carbon levels. Fertilization with compost as a source of organic carbon, nutrients, and accessory elements, as well as fertilization with mineral N- and PK fertilizer have been tested in a field experiment on a calcaric Fluvisol in the Danube wetlands, at 4 levels each. Yields of wheat were recorded, and grains and soils were sampled from each treatment, and analyzed for main and trace element composition. The corresponding soils were characterized by mobile phases, obtained by leaching with 0,16M acetic acid to cover exchangeables plus carbonates, and subsequently by 0,1M oxalate buffer pH 3 to dissolve the pedogenic oxides. Total amounts were obtained from digests with perchloric- nitric-hydrofluoric acid. For quasi-total amounts, aqua regia was replaced by pressure decomposition with KClO3 in dilute nitric acid. The proposed extraction sequence permits to analyze and interpret soil for main elements, trace elements, nutrients and anions simultaneously. Factor analyses of soil extracts obtained from dilute acetic acid revealed Ba-Be-Cd-Cu-Li-S (traces), Ca-Mg-Mn (main carbonates), Al-Fe-B, Y, and P-K (nutrients) as chemically feasible principal components. Subsequent soil extracts from oxalate contained Al-B-Co-K-Na-Pb-Si-V-S (maybe acid silicate weathering), Cr-Li-Ni-Sr-Ti (maybe basic silicate weathering), Be-Cu-Fe-P, Co-Mg-Mn-Zn (Mn-oxides) and Ba-Sc as principal components. Factor analyses of total element data distinguished the principal components Ce-La-Li-Sc-Y-P (rare earths), Al-Ca-Fe-K-Mg-Na-P (main elements), Cd-Co-Cr-Cu-Ni-Zn (trace elements), As-Pb (contaminants), Ba-Mn-Sr, and Ti, which looks chemically feasible also. Factor analyses of those soil fractions which presumably form the main fractions of exchangeables, carbonates, pedogenic oxides and silicates, showed no cross connections, except for P. Oxalate

  3. Mass transfer kinetics of biosorption of nitrogenous matter from palm oil mill effluent by aerobic granules in sequencing batch reactor.

    PubMed

    Fulazzaky, Mohamad Ali; Nuid, Maria; Aris, Azmi; Muda, Khalida

    2017-07-13

    Understanding of mass transfer kinetics is important for biosorption of nitrogen compounds from palm oil mill effluent (POME) to gain a mechanistic insight into future biological processes for the treatment of high organic loading wastewater. In this study, the rates of global and sequential mass transfer were determined using the modified mass transfer factor equations for the experiments to remove nitrogen by aerobic granular sludge accumulation in a sequencing batch reactor (SBR). The maximum efficiencies as high as 97% for the experiment run at [k L a] g value of 1421.8 h -1 and 96% for the experiment run at [k L a] g value of 9.6 × 10 37  h -1 were verified before and after the addition of Serratia marcescens SA30, respectively. The resistance of mass transfer could be dependent on external mass transfer that controls the transport of nitrogen molecule along the experimental period of 256 days. The increase in [k L a] g value leading to increased performance of the SBR was verified to contribute to the future applications of the SBR because this phenomenon provides new insight into the dynamic response of biological processes to treat POME.

  4. Where Stars Form: Inside-out Growth and Coherent Star Formation from HST Hα Maps of 3200 Galaxies across the Main Sequence at 0.7 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Nelson, Erica June; van Dokkum, Pieter G.; Förster Schreiber, Natascha M.; Franx, Marijn; Brammer, Gabriel B.; Momcheva, Ivelina G.; Wuyts, Stijn; Whitaker, Katherine E.; Skelton, Rosalind E.; Fumagalli, Mattia; Hayward, Christopher C.; Kriek, Mariska; Labbé, Ivo; Leja, Joel; Rix, Hans-Walter; Tacconi, Linda J.; van der Wel, Arjen; van den Bosch, Frank C.; Oesch, Pascal A.; Dickey, Claire; Ulf Lange, Johannes

    2016-09-01

    We present Hα maps at 1 kpc spatial resolution for star-forming galaxies at z ˜ 1, made possible by the Wide Field Camera 3 grism on Hubble Space Telescope (HST). Employing this capability over all five 3D-HST/CANDELS fields provides a sample of 3200 galaxies enabling a division into subsamples based on stellar mass and star formation rate (SFR). By creating deep stacked Hα images, we reach surface brightness limits of 1 × 10-18 erg s-1 cm-2 arcsec-2, allowing us to map the distribution of ionized gas to ˜10 kpc for typical L* galaxies at this epoch. We find that the spatial extent of the Hα distribution increases with stellar mass as {r}{{H}α }=1.5{({M}* /{10}10{M}⊙ )}0.23 kpc. The Hα emission is more extended than the stellar continuum emission, consistent with inside-out assembly of galactic disks. This effect grows stronger with mass as {r}{{H}α }/{r}* =1.1 {({M}* /{10}10{M}⊙ )}0.054. We map the Hα distribution as a function of SFR(IR+UV) and find evidence for “coherent star formation” across the SFR-M * plane: above the main sequence (MS), Hα is enhanced at all radii; below the MS, Hα is depressed at all radii. This suggests that at all masses the physical processes driving the enhancement or suppression of star formation act throughout the disks of galaxies. At high masses ({10}10.5\\lt {M}* /{M}⊙ \\lt {10}11), above the MS, Hα is particularly enhanced in the center, potentially building bulges and/or supermassive black holes. Below the MS, a strong central dip in the EW(Hα), as well as the inferred specific SFR, appears. Importantly, though, across the entirety of the SFR-M * plane, the absolute SFR as traced by Hα is always centrally peaked, even in galaxies below the MS.

  5. Escherichia coli Sequence Type 131 H30 Is the Main Driver of Emerging Extended-Spectrum-β-Lactamase-Producing E. coli at a Tertiary Care Center.

    PubMed

    Johnson, James R; Johnston, Brian; Thuras, Paul; Launer, Bryn; Sokurenko, Evgeni V; Miller, Loren G

    2016-01-01

    The H 30 strain of Escherichia coli sequence type 131 (ST131- H 30) is a recently emerged, globally disseminated lineage associated with fluoroquinolone resistance and, via its H 30Rx subclone, the CTX-M-15 extended-spectrum beta-lactamase (ESBL). Here, we studied the clonal background and resistance characteristics of 109 consecutive recent E. coli clinical isolates (2015) and 41 historical ESBL-producing E. coli blood isolates (2004 to 2011) from a public tertiary care center in California with a rising prevalence of ESBL-producing E. coli isolates. Among the 2015 isolates, ST131, which was represented mainly by ST131- H 30, was the most common clonal lineage (23% overall). ST131- H 30 accounted for 47% (8/17) of ESBL-producing, 47% (14/30) of fluoroquinolone-resistant, and 33% (11/33) of multidrug-resistant isolates. ST131- H 30 also accounted for 53% (8/14) of dually fluoroquinolone-resistant, ESBL-producing isolates, with the remaining 47% comprised of diverse clonal groups that contributed a single isolate each. ST131- H 30Rx, with CTX-M-15, was the major ESBL producer (6/8) among ST131- H 30 isolates. ST131- H 30 and H 30Rx also dominated (46% and 37%, respectively) among the historical ESBL-producing isolates (2004 to 2011), without significant temporal shifts in relative prevalence. Thus, this medical center's recently emerging ESBL-producing E. coli strains, although multiclonal, are dominated by ST131- H 30 and H 30Rx, which are the only clonally expanded fluoroquinolone-resistant, ESBL-producing lineages. Measures to rapidly and effectively detect, treat, and control these highly successful lineages are needed. IMPORTANCE The ever-rising prevalence of resistance to first-line antibiotics among clinical Escherichia coli isolates leads to worse clinical outcomes and higher health care costs, thereby creating a need to discover its basis so that effective interventions can be developed. We found that the H 30 subset within E. coli sequence type 131

  6. First determination of s-process element abundances in pre-main sequence clusters. Y, Zr, La, and Ce in IC 2391, the Argus association, and IC 2602

    NASA Astrophysics Data System (ADS)

    D'Orazi, V.; De Silva, G. M.; Melo, C. F. H.

    2017-02-01

    Context. Several high-resolution spectroscopic studies have provided compelling observational evidence that open clusters display a decreasing trend of their barium abundances as a function of the cluster's age. Young clusters (ages ≲ 200 Myr) exhibit significant enhancement in the [Ba/Fe] ratios, at variance with solar-age clusters where the Ba content has been found to be [Ba/Fe] 0 dex. Different viable solutions have been suggested in the literature; nevertheless, a conclusive interpretation of such a peculiar trend has not been found. Interestingly, it is debated whether the other species produced with Ba via s-process reactions follow the same trend with age. Aims: Pre-main sequence clusters (≈10-50 Myr) show the most extreme behaviour in this respect: their [Ba/Fe] ratios can reach 0.65 dex, which is higher than the solar value by a factor of four. Crucially, there are no investigations of the other s-process species for these young stellar populations. In this paper we present the first determination of Y, Zr, La, and Ce in clusters IC 2391, IC 2602, and the Argus association. The main objective of our work is to ascertain whether these elements reveal the same enhancement as Ba. Methods: We have exploited high-resolution, high signal-to-noise spectra in order to derive abundances for Y, Zr, La, and Ce via spectral synthesis calculations. Our sample includes only stars with very similar atmospheric parameters so that internal errors due to star-to-star inhomogeneity are negligible. The chemical analysis was carried out in a strictly differential way, as done in all our previous investigations, to minimise the impact of systematic uncertainties. Results: Our results indicate that, at variance with Ba, all the other s-process species exhibit a solar scaled pattern; these clusters confirm a similar trend discovered in the slightly older local associations (e.g. AB Doradus, Carina-Near), where only Ba exhibit enhanced value with all other s-process species

  7. Theory and evidence of global Rossby waves in upper main-sequence stars: r-mode oscillations in many Kepler stars

    NASA Astrophysics Data System (ADS)

    Saio, Hideyuki; Kurtz, Donald W.; Murphy, Simon J.; Antoci, Victoria L.; Lee, Umin

    2018-02-01

    Asteroseismic inference from pressure modes (p modes) and buoyancy, or gravity, modes (g modes) is ubiquitous for stars across the Hertzsprung-Russell diagram. Until now, however, discussion of r modes (global Rossby waves) has been rare. Here we derive the expected frequency ranges of r modes in the observational frame by considering the visibility of these modes. We find that the frequencies of r modes of azimuthal order m appear as groups at slightly lower frequency than m times the rotation frequency. Comparing the visibility curves for r modes with Fourier amplitude spectra of Kepler light curves of upper main-sequence B, A, and F stars, we find that r modes are present in many γ Dor stars (as first discovered by Van Reeth et al.), spotted stars, and so-called heartbeat stars, which are highly eccentric binary stars. We also find a signature of r modes in a frequently bursting Be star observed by Kepler. In the amplitude spectra of moderately to rapidly rotating γ Dor stars, r-mode frequency groups appear at lower frequency than prograde g-mode frequency groups, while in the amplitude spectra of spotted early A to B stars, groups of symmetric (with respect to the equator) r-mode frequencies appear just below the frequency of a structured peak that we suggest represents an approximate stellar rotation rate. In many heartbeat stars, a group of frequencies can be fitted with symmetric m = 1 r modes, which can be used to obtain rotation frequencies of these stars.

  8. POPULATION PARAMETERS OF INTERMEDIATE-AGE STAR CLUSTERS IN THE LARGE MAGELLANIC CLOUD. I. NGC 1846 AND ITS WIDE MAIN-SEQUENCE TURNOFF

    SciTech Connect

    Goudfrooij, Paul; Kozhurina-Platais, Vera; Puzia, Thomas H.

    2009-06-15

    The Advanced Camera for Surveys onboard the Hubble Space Telescope has been used to obtain deep, high-resolution images of the intermediate-age star cluster NGC 1846 in the Large Magellanic Cloud. We present new color-magnitude diagrams (CMDs) based on F435W, F555W, and F814W imaging. We test the previously observed broad main-sequence turnoff (MSTO) region for 'contamination' by field stars and (evolved) binary star systems. We find that while these impact the number of objects in this region, none can fully account for the large color spread. Our results therefore solidify the recent finding that stars in the MSTO region of thismore » cluster have a large spread in color which is unrelated to measurement errors or contamination by field stars, and likely due to a {approx} 300 Myr range in the ages of cluster stars. An unbiased estimate of the stellar density distribution across the MSTO region shows that the spread is fairly continuous rather than strongly bimodal, as suggested previously. We fit the CMDs with several different sets of theoretical isochrones, and determine systematic uncertainties for population parameters when derived using any one set of isochrones. We note a degeneracy between age and [{alpha}/Fe], which can be lifted by matching the shape (curvature) of the full red giant branch (RGB) in the CMD. We find that stars in the upper part of the MSTO region are more centrally concentrated than those in any other region, including more massive RGB and asymptotic giant branch stars. We consider several possible formation scenarios which account for the unusual features observed in the CMD of NGC 1846.« less

  9. Oxygen 6156-8 Angstroms Triplet in Chemically Peculiar Stars of the Upper Main Sequence: Do HgMn Stars Show an Oxygen Anomaly?

    NASA Astrophysics Data System (ADS)

    Takeda, Yoichi; Takada-Hidai, Masahide; Jugaku, Jun; Sakaue, Akihiko; Sadakane, Kozo

    1999-12-01

    An extensive spectrum-fitting analysis in the lambda ~ 6150 Angstroms region was performed for forty late-B and A chemically peculiar (HgMn, Ap, Am, weak-lined) and normal stars of the upper main sequence, in order to quantitatively establish the abundance of oxygen from the O I 6156-8 triplet and to study its behavior/anomaly for each peculiarity group, where special attention was paid to HgMn-type stars. Magnetic Ap variables (Si or SrCrEu type) generally show a remarkably large oxygen depletion (by ~ -1.6 dex to ~ -0.4 dex relative to the solar abundance), and classical Am stars also show a clear underabundance (by ~ -0.6 dex on the average). In contrast, the oxygen abundance in HgMn stars, exhibiting only a mild deficiency relative to the Sun typically by ~ 0.3-0.4 dex, is not markedly different from the tendency of normal stars, also showing a subsolar abundance ([O/H] =~ -0.2). In view of the recent observational implication that the present solar oxygen abundance is enriched by ~ 0.2-0.3 dex relative to the interstellar gas (from which young stars are formed), and thus unsuitable for the comparison standard, we concluded that the extent of the average O-deficiency in HgMn stars is appreciably reduced down to only ~ 0.1-0.2 dex (i.e., not much different from the initial composition), which contrasts with their well-known drastically large N-depletion. Yet, as can be seen from the delicate and tight O vs. Fe anticorrelation, this marginal deficiency should be real, and thus some physical process simultaneously producing O-depletion/Fe-enrichment must have actually worked in the atmosphere of HgMn stars.

  10. The State-of-the-art HST Astro-photometric Analysis of the Core of ω Centauri. III. The Main Sequence's Multiple Populations Galore

    SciTech Connect

    Bellini, A.; Anderson, J.; Van der Marel, R. P.

    2017-08-01

    We take advantage of the exquisite quality of the Hubble Space Telescope 26-filter astro-photometric catalog of the core of ω Cen presented in the first paper of this series and the empirical differential-reddening correction presented in the second paper in order to distill the main sequence into its constituent populations. To this end, we restrict ourselves to the five most useful filters: the magic “trio” of F275W, F336W, and F438W, along with F606W and F814W. We develop a strategy for identifying color systems where different populations stand out most distinctly, then we isolate those populations and examine them in othermore » filters where their subpopulations also come to light. In this way, we have identified at least 15 subpopulations, each of which has a distinctive fiducial curve through our five-dimensional photometric space. We confirm the MSa to be split into two subcomponents, and find that both the bMS and the rMS are split into three subcomponents. Moreover, we have discovered two additional MS groups: the MSd (which has three subcomponents) shares similar properties with the bMS, and the MSe (which has four subcomponents) has properties more similar to those of the rMS. We examine the fiducial curves together and use synthetic spectra to infer relative heavy-element, light-element, and helium abundances for the populations. Our findings show that the stellar populations and star formation history of ω Cen are even more complex than inferred previously. Finally, we provide as a supplement to the original catalog a list that identifies for each star which population it is most likely associated with.« less

  11. The State-of-the-art HST Astro-photometric Analysis of the Core of ω Centauri. III. The Main Sequence's Multiple Populations Galore

    NASA Astrophysics Data System (ADS)

    Bellini, A.; Milone, A. P.; Anderson, J.; Marino, A. F.; Piotto, G.; van der Marel, R. P.; Bedin, L. R.; King, I. R.

    2017-08-01

    We take advantage of the exquisite quality of the Hubble Space Telescope 26-filter astro-photometric catalog of the core of ω Cen presented in the first paper of this series and the empirical differential-reddening correction presented in the second paper in order to distill the main sequence into its constituent populations. To this end, we restrict ourselves to the five most useful filters: the magic “trio” of F275W, F336W, and F438W, along with F606W and F814W. We develop a strategy for identifying color systems where different populations stand out most distinctly, then we isolate those populations and examine them in other filters where their subpopulations also come to light. In this way, we have identified at least 15 subpopulations, each of which has a distinctive fiducial curve through our five-dimensional photometric space. We confirm the MSa to be split into two subcomponents, and find that both the bMS and the rMS are split into three subcomponents. Moreover, we have discovered two additional MS groups: the MSd (which has three subcomponents) shares similar properties with the bMS, and the MSe (which has four subcomponents) has properties more similar to those of the rMS. We examine the fiducial curves together and use synthetic spectra to infer relative heavy-element, light-element, and helium abundances for the populations. Our findings show that the stellar populations and star formation history of ω Cen are even more complex than inferred previously. Finally, we provide as a supplement to the original catalog a list that identifies for each star which population it is most likely associated with. Based on archival observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  12. Hot ammonia around young O-type stars. III. High-mass star formation and hot core activity in W51 Main

    NASA Astrophysics Data System (ADS)

    Goddi, C.; Ginsburg, A.; Zhang, Q.

    2016-05-01

    Context. This paper is the third in a series of NH3 multilevel imaging studies in well-known, high-mass star-forming regions. The main goal is to characterize kinematics and physical conditions of (hot and dense) circumstellar molecular gas around O-type young stars. Aims: We want to map at subarcsecond resolution highly excited inversion lines of NH3 in the high-mass star-forming region W51 Main (distance = 5.4 kpc), which is an ideal target to constrain theoretical models of high-mass star formation. Methods: Using the Karl Jansky Very Large Array (JVLA), we mapped the hot and dense molecular gas in W51 Main with ~0.2 arcsec-0.3 arcsec angular resolution in five metastable (J = K) inversion transitions of ammonia (NH3): (J,K) = (6, 6), (7, 7), (9, 9), (10, 10), and (13, 13). These lines arise from energy levels between ~400 K and ~1700 K above the ground state. We also made maps of the (free-free) continuum emission at frequencies between 25 and 36 GHz. Results: We have identified and characterized two main centers of high-mass star formation in W51 Main, which excite hot cores and host one or multiple high-mass young stellar objects (YSOs) at their centers: the W51e2 complex and the W51e8 core (~6'' southward of W51e2). The former breaks down into three further subcores: W51e2-W, which surrounds the well-known hypercompact (HC) HII region, where hot NH3 is observed in absorption, and two additional dusty cores, W51e2-E (~0.8 arcsec to the East) and W51e2-NW (~1'' to the North), where hot NH3 is observed in emission. The velocity maps toward the HC HII region show a clear velocity gradient along the east-west in all lines. The gradient may indicate rotation, although any Keplerian motion must be on smaller scales (<1000 AU) as we do not directly observe a Keplerian velocity profile. The absence of outflow and/or maser activity and the low amount of molecular gas available for accretion (~5 M⊙, assuming [NH3]/[H2] = 10-7) with respect to the mass of the central

  13. Sequencing of Isotope-Labeled Small RNA Using Femtosecond Laser Ablation Time-of-Flight Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Kurata-Nishimura, Mizuki; Ando, Yoshinari; Kobayashi, Tohru; Matsuo, Yukari; Suzuki, Harukazu; Hayashizaki, Yoshihide; Kawai, Jun

    2010-04-01

    A novel method for the analysis of sequences of small RNAs using nucleotide triphosphates labeled with stable isotopes has been developed using time-of-flight mass spectroscopy combined with femtosecond laser ablation (fsLA-TOF-MS). Small RNAs synthesized with nucleotides enriched in 13C and 15N were efficiently atomized and ionized by single-shot fsLA and the isotope ratios 13C/12C and 15N/14N were evaluated using the TOF-MS method. By comparing the isotope ratios among four different configurations, the number of nucleotide contents of the control RNA sample were successfully reproduced.

  14. Gene Expression Analysis in the Age of Mass Sequencing: An Introduction.

    PubMed

    Pilarsky, Christian; Nanduri, Lahiri Kanth; Roy, Janine

    2016-01-01

    During the last years the technology used for gene expression analysis has changed dramatically. The old mainstay, DNA microarray, has served its due course and will soon be replaced by next-generation sequencing (NGS), the Swiss army knife of modern high-throughput nucleic acid-based analysis. Therefore preparation technologies have to adapt to suit the emerging NGS technology platform. Moreover, interpretation of the results is still time consuming and employs the use of high-end computers usually not found in molecular biology laboratories. Alternatively, cloud computing might solve this problem. Nevertheless, these new challenges have to be embraced for gene expression analysis in general.

  15. Mass

    SciTech Connect

    Quigg, Chris

    2007-12-05

    In the classical physics we inherited from Isaac Newton, mass does not arise, it simply is. The mass of a classical object is the sum of the masses of its parts. Albert Einstein showed that the mass of a body is a measure of its energy content, inviting us to consider the origins of mass. The protons we accelerate at Fermilab are prime examples of Einsteinian matter: nearly all of their mass arises from stored energy. Missing mass led to the discovery of the noble gases, and a new form of missing mass leads us to the notion of darkmore » matter. Starting with a brief guided tour of the meanings of mass, the colloquium will explore the multiple origins of mass. We will see how far we have come toward understanding mass, and survey the issues that guide our research today.« less

  16. Evaluation of two main RNA-seq approaches for gene quantification in clinical RNA sequencing: polyA+ selection versus rRNA depletion.

    PubMed

    Zhao, Shanrong; Zhang, Ying; Gamini, Ramya; Zhang, Baohong; von Schack, David

    2018-03-19

    To allow efficient transcript/gene detection, highly abundant ribosomal RNAs (rRNA) are generally removed from total RNA either by positive polyA+ selection or by rRNA depletion (negative selection) before sequencing. Comparisons between the two methods have been carried out by various groups, but the assessments have relied largely on non-clinical samples. In this study, we evaluated these two RNA sequencing approaches using human blood and colon tissue samples. Our analyses showed that rRNA depletion captured more unique transcriptome features, whereas polyA+ selection outperformed rRNA depletion with higher exonic coverage and better accuracy of gene quantification. For blood- and colon-derived RNAs, we found that 220% and 50% more reads, respectively, would have to be sequenced to achieve the same level of exonic coverage in the rRNA depletion method compared with the polyA+ selection method. Therefore, in most cases we strongly recommend polyA+ selection over rRNA depletion for gene quantification in clinical RNA sequencing. Our evaluation revealed that a small number of lncRNAs and small RNAs made up a large fraction of the reads in the rRNA depletion RNA sequencing data. Thus, we recommend that these RNAs are specifically depleted to improve the sequencing depth of the remaining RNAs.

  17. Batch-processing of imaging or liquid-chromatography mass spectrometry datasets and De Novo sequencing of polyketide siderophores.

    PubMed

    Novák, Jiří; Sokolová, Lucie; Lemr, Karel; Pluháček, Tomáš; Palyzová, Andrea; Havlíček, Vladimír

    2017-07-01

    The open-source and cross-platform software CycloBranch was utilized for dereplication of organic compounds from mass spectrometry imaging imzML datasets and its functions were illustrated on microbial siderophores. The pixel-to-pixel batch-processing was analogous to liquid chromatography mass spectrometry data. Each data point represented here by accurate m/z values and the corresponding ion intensities was matched against integrated compound libraries. The fine isotopic structure matching was also embedded into CycloBranch dereplication process. The siderophores' characterization from single-pixel mass spectra was further supported by their de novo sequencing. New ketide building block library was utilized by CycloBranch to characterize the siderophores in images and mixtures and nomenclature of fragment ion series of linear and cyclic polyketide siderophores was proposed. The software is freely available at http://ms.biomed.cas.cz/cyclobranch. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. E/S0 Galaxies on the Blue Color-Stellar Mass Sequence at z = 0: Fading Mergers or Future Spirals?

    NASA Astrophysics Data System (ADS)

    Kannappan, Sheila J.; Guie, Jocelly M.; Baker, Andrew J.

    2009-08-01

    We identify a population of morphologically defined E/S0 galaxies lying on the locus of late-type galaxies in color-stellar mass space—the "blue sequence"—at the present epoch. Using three samples (from the Nearby Field Galaxy Survey or NFGS, a merged HyperLeda/Sloan Digital Sky Survey/Two Micron All Sky Survey catalog, and the NYU Value-Added Galaxy Catalog), we analyze blue-sequence E/S0s with stellar masses gsim108 M sun, arguing that individual objects may be evolving either up toward the red sequence or down into the blue sequence. Blue-sequence E/S0 galaxies become more common with decreasing stellar mass, comprising lsim2% of E/S0s near the "shutdown mass" Ms ~ 1-2 × 1011 M sun, increasing to gsim5% near the "bimodality mass" Mb ~ 3 × 1010 M sun, and sharply rising to gsim 20%-30% below the "threshold mass" Mt ~ 4-6 × 109 M sun, down to our completeness analysis limit at ~109 M sun. The strong emergence of blue-sequence E/S0s below Mt coincides with a previously reported global increase in mean atomic gas fractions below Mt for galaxies of all types on both sequences, suggesting that the availability of cold gas may be basic to blue-sequence E/S0s' existence. Environmental analysis reveals that many sub-Mb blue-sequence E/S0s reside in low-to-intermediate density environments. Thus, the bulk of the population we analyze appears distinct from the generally lower-mass cluster dE population; S0 morphologies with a range of bulge sizes are typical. In mass-radius and mass-σ scaling relations, blue-sequence E/S0s are more similar to red-sequence E/S0s than to late-type galaxies, but they represent a transitional class. While some of them, especially in the high-mass range from Mb to Ms , resemble major-merger remnants that will likely fade onto the red sequence, most blue-sequence E/S0s below Mb show signs of disk and/or pseudobulge building, which may be enhanced by companion interactions. The blue overall colors of blue-sequence E/S0s are most clearly

  19. Pseudo-Random Sequence Modifications for Ion Mobility Orthogonal Time of Flight Mass Spectrometry

    PubMed Central

    Clowers, Brian H.; Belov, Mikhail E.; Prior, David C.; Danielson, William F.; Ibrahim, Yehia; Smith, Richard D.

    2008-01-01

    Due to the inherently low duty cycle of ion mobility spectrometry (IMS) experiments that sample from continuous ion sources, a range of experimental advances have been developed to maximize ion utilization efficiency. The use of ion trapping mechanisms prior to the ion mobility drift tube has demonstrated significant gains over discrete sampling from continuous sources; however, these technologies have traditionally relied upon a signal averaging to attain analytically relevant signal-to-noise ratios (SNR). Multiplexed (MP) techniques based upon the Hadamard transform offer an alternative experimental approach by which ion utilization efficiency can be elevated to ∼ 50 %. Recently, our research group demonstrated a unique multiplexed ion mobility time-of-flight (MP-IMS-TOF) approach that incorporates ion trapping and can extend ion utilization efficiency beyond 50 %. However, the spectral reconstruction of the multiplexed signal using this experiment approach requires the use of sample-specific weighing designs. Though general weighing designs have been shown to significantly enhance ion utilization efficiency using this MP technique, such weighing designs cannot be applied to all samples. By modifying both the ion funnel trap and the pseudo random sequence (PRS) used for the MP experiment we have eliminated the need for complex weighing matrices. For both simple and complex mixtures SNR enhancements of up to 13 were routinely observed as compared to the SA-IMS-TOF experiment. In addition, this new class of PRS provides a two fold enhancement in ion throughput compared to the traditional HT-IMS experiment. PMID:18311942

  20. Main differences between volatiles of sparkling and base wines accessed through comprehensive two dimensional gas chromatography with time-of-flight mass spectrometric detection and chemometric tools.

    PubMed

    Welke, Juliane Elisa; Zanus, Mauro; Lazzarotto, Marcelo; Pulgati, Fernando Hepp; Zini, Cláudia Alcaraz

    2014-12-01

    The main changes in the volatile profile of base wines and their corresponding sparkling wines produced by traditional method were evaluated and investigated for the first time using headspace solid-phase microextraction combined with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC×GC/TOFMS) and chemometric tools. Fisher ratios helped to find the 119 analytes that were responsible for the main differences between base and sparkling wines and principal component analysis explained 93.1% of the total variance related to the selected 78 compounds. It was also possible to observe five subclusters in base wines and four subclusters in sparkling wines samples through hierarchical cluster analysis, which seemed to have an organised distribution according to the regions where the wines came from. Twenty of the most important volatile compounds co-eluted with other components and separation of some of them was possible due to GC×GC/TOFMS performance. Copyright © 2014. Published by Elsevier Ltd.

  1. Complete and Draft Genome Sequences of Nine Lactobacillus sakei Strains Selected from the Three Known Phylogenetic Lineages and Their Main Clonal Complexes.

    PubMed

    Loux, Valentin; Coeuret, Gwendoline; Zagorec, Monique; Champomier Vergès, Marie-Christine; Chaillou, Stéphane

    2018-04-19

    We present here the complete and draft genome sequences of nine Lactobacillus sakei strains, selected from the entire range of clonal complexes from the three known lineages of the species. The strains were chosen to provide a wide view of pangenomic and plasmidic diversity for this important foodborne species. Copyright © 2018 Loux et al.

  2. Profiling and sequencing of gangliosides from human caudate nucleus by chip-nanoelectrospray mass spectrometry.

    PubMed

    Serb, Alina F; Sisu, Eugen; Vukelić, Zeljka; Zamfir, Alina D

    2012-12-01

    Gangliosides (GGs), sialic acid-containing glycosphingolipids are involved in many brain functions at the cell and molecular level. Compositional and structural elucidation of GGs in mixtures extracted from human brain is essential for correlating their profile with the specialized function of each brain area in health and disease. As a part of our ongoing study on GG expression and structure in different healthy and diseased brain regions, in this work, a preliminary investigation of GGs in a specimen of human caudate nucleus (CN) was carried out using an advanced mass spectrometry (MS) technique. By chip-nanoelectrospray MS performed on a NanoMate robot coupled to a high capacity ion trap instrument, 81 GG components were detected in human CN in only 1.5 min of signal acquisition. Although the native GG mixture from CN was found dominated by mono-, di- and trisialylated GGs with a slight dominance of disialylated forms (GD), four tetrasialylated structures (GQ) and two pentasialylated (GP) species were also identified. Additionally, species with unusually long fatty acid chains, exceeding 30 carbon atoms in their ceramide (Cer) composition, and several glycoforms modified by fucosyl (Fuc), O-acetyl (O-Ac) and/or lactonization were discovered. By tandem MS (MS(2) ) using collision-induced dissociation, two atypical mono and disialylated species with long-chain fatty acids in their Cer could be confirmed and structurally characterized. These results may be a starting point for new GG-based approaches in the study of CN functions and ethiopathogenesis of CN-related neurodegenerative disorders. Copyright © 2012 John Wiley & Sons, Ltd.

  3. Comparison of A+T-rich oligonucleotides with and without self-complementary sequence using ion-pair reversed-phase high-performance liquid chromatography/tandem electrospray ionization mass spectrometry.

    PubMed

    Song, Renfang; Zhang, Wenbing; Chen, Huayong; Ma, Huimin; Dong, Yulian; Sheng, Guoying; Zhou, Zhen; Fu, Jiamo

    2005-01-01

    Both A+T-rich oligonucleotides with and without self-complementary sequences were analyzed using ion- pair reversed-phase liquid chromatography/electrospray ionization mass spectrometry (IP-RP-HPLC/ESI-MS) by tryethylammonium acetate (TEAA) and hexafluoroisopropanol (HFIP) buffer systems to study the characteristics of their retention behavior and electrospray ionization tandem mass spectrometry (ESI-MS/MS) response. The results indicated that the chain length had the same effect on the retention of A+T-rich oligonucleotides in both of TEAA and HFIP buffer systems but the sequence had a different impact on the retention in the two buffer systems. A+T- rich oligonucleotides with a self-complementary sequence were much shorter than those without in the TEAA buffer system whereas a slight difference was observed in the HFIP buffer system. Similar total ion current (TIC) intensity was observed both in oligonucleotides with or without self-complementary sequence. The opposite trend of a change in the TIC intensities with increasing chain length were observed in both the TEAA and HFIP buffer systems. A lower charge state was predominant in the TEAA buffer system whereas a higher charge state was mainly distributed in the HFIP buffer system. The oligonucleotides without self-complementary sequences had a higher charge state than those with self-complementary sequences. A- and T- are more esily formed at a higher charge state whereas the sequence fragments will be formed more easily at a lower charge state in both A+T-rich oligonucleotides with and without self-complementary sequences.

  4. Hydrogen Exchange Mass Spectrometry of Related Proteins with Divergent Sequences: A Comparative Study of HIV-1 Nef Allelic Variants

    NASA Astrophysics Data System (ADS)

    Wales, Thomas E.; Poe, Jerrod A.; Emert-Sedlak, Lori; Morgan, Christopher R.; Smithgall, Thomas E.; Engen, John R.

    2016-06-01

    Hydrogen exchange mass spectrometry can be used to compare the conformation and dynamics of proteins that are similar in tertiary structure. If relative deuterium levels are measured, differences in sequence, deuterium forward- and back-exchange, peptide retention time, and protease digestion patterns all complicate the data analysis. We illustrate what can be learned from such data sets by analyzing five variants (Consensus G2E, SF2, NL4-3, ELI, and LTNP4) of the HIV-1 Nef protein, both alone and when bound to the human Hck SH3 domain. Regions with similar sequence could be compared between variants. Although much of the hydrogen exchange features were preserved across the five proteins, the kinetics of Nef binding to Hck SH3 were not the same. These observations may be related to biological function, particularly for ELI Nef where we also observed an impaired ability to downregulate CD4 surface presentation. The data illustrate some of the caveats that must be considered for comparison experiments and provide a framework for investigations of other protein relatives, families, and superfamilies with HX MS.

  5. Discovery of Chromatin-Associated Proteins via Sequence-Specific Capture and Mass Spectrometric Protein Identification in Saccharomyces cerevisiae

    PubMed Central

    2015-01-01

    DNA–protein interactions play critical roles in the control of genome expression and other fundamental processes. An essential element in understanding how these systems function is to identify their molecular components. We present here a novel strategy, Hybridization Capture of Chromatin Associated Proteins for Proteomics (HyCCAPP), to identify proteins that are interacting with any given region of the genome. This technology identifies and quantifies the proteins that are specifically interacting with a genomic region of interest by sequence-specific hybridization capture of the target region from in vivo cross-linked chromatin, followed by mass spectrometric identification and quantification of associated proteins. We demonstrate the utility of HyCCAPP by identifying proteins associated with three multicopy and one single-copy loci in yeast. In each case, a locus-specific pattern of target-associated proteins was revealed. The binding of previously unknown proteins was confirmed by ChIP in 11 of 17 cases. The identification of many previously known proteins at each locus provides strong support for the ability of HyCCAPP to correctly identify DNA-associated proteins in a sequence-specific manner, while the discovery of previously unknown proteins provides new biological insights into transcriptional and regulatory processes at the target locus. PMID:24999558

  6. Characterization of Pseudomonas chlororaphis myovirus 201{phi}2-1 via genomic sequencing, mass spectrometry, and electron microscopy

    SciTech Connect

    Thomas, Julie A.; Rolando, Mandy R.; Carroll, Christopher A.

    2008-07-05

    Pseudomonas chlororaphis phage 201{phi}2-1 is a relative of Pseudomonas aeruginosa myovirus {phi}KZ. Phage 201{phi}2-1 was examined by complete genomic sequencing (316,674 bp), by a comprehensive mass spectrometry survey of its virion proteins and by electron microscopy. Seventy-six proteins, of which at least 69 have homologues in {phi}KZ, were identified by mass spectrometry. Eight proteins, in addition to the major head, tail sheath and tail tube proteins, are abundant in the virion. Electron microscopy of 201{phi}2-1 revealed a multitude of long, fine fibers apparently decorating the tail sheath protein. Among the less abundant virion proteins are three homologues to RNA polymerasemore » {beta} or {beta}' subunits. Comparison between the genomes of 201{phi}2-1 and {phi}KZ revealed substantial conservation of the genome plan, and a large region with an especially high rate of gene replacement. The {phi}KZ-like phages exhibited a two-fold higher rate of divergence than for T4-like phages or host genomes.« less

  7. Sequencing of mitochondrial genomes of nine Aspergillus and Penicillium species identifies mobile introns and accessory genes as main sources of genome size variability.

    PubMed

    Joardar, Vinita; Abrams, Natalie F; Hostetler, Jessica; Paukstelis, Paul J; Pakala, Suchitra; Pakala, Suman B; Zafar, Nikhat; Abolude, Olukemi O; Payne, Gary; Andrianopoulos, Alex; Denning, David W; Nierman, William C

    2012-12-12

    The genera Aspergillus and Penicillium include some of the most beneficial as well as the most harmful fungal species such as the penicillin-producer Penicillium chrysogenum and the human pathogen Aspergillus fumigatus, respectively. Their mitochondrial genomic sequences may hold vital clues into the mechanisms of their evolution, population genetics, and biology, yet only a handful of these genomes have been fully sequenced and annotated. Here we report the complete sequence and annotation of the mitochondrial genomes of six Aspergillus and three Penicillium species: A. fumigatus, A. clavatus, A. oryzae, A. flavus, Neosartorya fischeri (A. fischerianus), A. terreus, P. chrysogenum, P. marneffei, and Talaromyces stipitatus (P. stipitatum). The accompanying comparative analysis of these and related publicly available mitochondrial genomes reveals wide variation in size (25-36 Kb) among these closely related fungi. The sources of genome expansion include group I introns and accessory genes encoding putative homing endonucleases, DNA and RNA polymerases (presumed to be of plasmid origin) and hypothetical proteins. The two smallest sequenced genomes (A. terreus and P. chrysogenum) do not contain introns in protein-coding genes, whereas the largest genome (T. stipitatus), contains a total of eleven introns. All of the sequenced genomes have a group I intron in the large ribosomal subunit RNA gene, suggesting that this intron is fixed in these species. Subsequent analysis of several A. fumigatus strains showed low intraspecies variation. This study also includes a phylogenetic analysis based on 14 concatenated core mitochondrial proteins. The phylogenetic tree has a different topology from published multilocus trees, highlighting the challenges still facing the Aspergillus systematics. The study expands the genomic resources available to fungal biologists by providing mitochondrial genomes with consistent annotations for future genetic, evolutionary and population

  8. "De-novo" amino acid sequence elucidation of protein G'e by combined "Top-Down" and "Bottom-Up" mass spectrometry

    NASA Astrophysics Data System (ADS)

    Yefremova, Yelena; Al-Majdoub, Mahmoud; Opuni, Kwabena F. M.; Koy, Cornelia; Cui, Weidong; Yan, Yuetian; Gross, Michael L.; Glocker, Michael O.

    2015-03-01

    Mass spectrometric de-novo sequencing was applied to review the amino acid sequence of a commercially available recombinant protein Ǵ with great scientific and economic importance. Substantial deviations to the published amino acid sequence (Uniprot Q54181) were found by the presence of 46 additional amino acids at the N-terminus, including a so-called "His-tag" as well as an N-terminal partial α- N-gluconoylation and α- N-phosphogluconoylation, respectively. The unexpected amino acid sequence of the commercial protein G' comprised 241 amino acids and resulted in a molecular mass of 25,998.9 ± 0.2 Da for the unmodified protein. Due to the higher mass that is caused by its extended amino acid sequence compared with the original protein G' (185 amino acids), we named this protein "protein G'e." By means of mass spectrometric peptide mapping, the suggested amino acid sequence, as well as the N-terminal partial α- N-gluconoylations, was confirmed with 100% sequence coverage. After the protein G'e sequence was determined, we were able to determine the expression vector pET-28b from Novagen with the Xho I restriction enzyme cleavage site as the best option that was used for cloning and expressing the recombinant protein G'e in E. coli. A dissociation constant ( K d ) value of 9.4 nM for protein G'e was determined thermophoretically, showing that the N-terminal flanking sequence extension did not cause significant changes in the binding affinity to immunoglobulins.

  9. Functional expression, purification and high sequence coverage mass spectrometric characterization of human excitatory amino acid transporter EAAT2

    PubMed Central

    Ye, Ran; Rhoderick, Joseph F.; Thompson, Charles M.; Bridges, Richard J.

    2015-01-01

    The glial excitatory amino acid transporter 2 (EAAT2) mediates a majority of glutamate re-uptake in human CNS and, consequently, is associated with a variety of signaling and pathological processes. While our understanding of the function, mechanism and structure of this integral membrane protein is increasing, little if any mass spectrometric (MS) data is available for any of the EAATs specifically, and for only a few mammalian plasma membrane transporters in general. A protocol to express and purify functional EAAT2 in sufficient quantities to carry out MS-based peptide mapping as needed to study ligand–transporter interactions is described. A 6×HIS epitope was incorporated into the N-terminus of human EAAT2. The recombinant protein was expressed in high levels in mammalian HEK 293T cells, where it exhibited the pharmacological properties of the native transporter. EAAT2 was purified from isolated cell membranes in a single step using nickel affinity chromatography. In-gel and in-solution trypsin digestions were conducted on the isolated protein and then analyzed by MALDI-TOF and LC-MS/MS mass spectrometry. Overall, 89% sequence coverage of the protein was achieved with these methods. In particular, an 88 amino acid tryptic peptide covering the presumed substrate binding domains HP1, TMD7, HP2, and TMD8 domains of EAAT2 was also identified after N-deglycosylation. Beyond the specific applicability to EAAT2, this study provides an efficient, simple and scalable approach to express, purify, digest and characterize integral membrane transporter proteins by mass spectrometry. PMID:20399272

  10. High sedimentation rates in the Early Triassic after latest Permian mass extinction: Carbonate production is main factor in non-Arctic regions

    NASA Astrophysics Data System (ADS)

    Horacek, Micha; Brandner, Rainer

    2016-04-01

    A substantial change in sedimentation rates towards higher values has been documented from the Late Permian to the Lower Triassic. Although it is assumed and also has been shown that the deposition of siliciclastic material increased in the Lower Triassic due to stronger erosion because of loss of land cover and increased chemical and physical weathering with extreme climate warming, the main sediment production occurred by marine carbonate production. Still, carbonate production might have been significantly influenced by weathering and erosion in the hinterland, as the transport of dust by storms into the ocean water probably was a main nutrient source for microbial carbonate producers, because "normal" nutrient supply by ocean circulation, i. e. upwelling was strongly reduced due to the elevated temperatures resulting in water-column stratification . Sediment accumulation was also clearly influenced by the paleo-geographic and latitudinal position, with lower carbonate production and sedimentation rates in moderate latitudes. The existence of a "boundary clay" and microbial carbonate mounds and layers in the immediate aftermath of the latest Permian mass extinction points towards a development from a short-timed acid ocean water - resulting in a carbonate production gap and the deposition of the boundary clay towards the deposition of the microbial mounds and layers due to the microbial production of micro-environments with higher alkalinity allowing the production of carbonate. After the return of the ocean water to normal alkalinity planktic production of carbonate resulted in a very high sedimentation rate, especially taking into account the absence of carbonate producing eukaryotic algae and animals.

  11. Mass Spectrometric Imaging of Wheat (Triticum spp.) and Barley (Hordeum vulgare L.) Cultivars: Distribution of Major Cell Wall Polysaccharides According to Their Main Structural Features.

    PubMed

    Veličković, Dušan; Saulnier, Luc; Lhomme, Margot; Damond, Aurélie; Guillon, Fabienne; Rogniaux, Hélène

    2016-08-17

    Arabinoxylans (AX) and (1→3),(1→4)-β-glucans (BG) are the main components of cereal cell walls and influence many aspects of their end uses. Important variations in the composition and structure of these polysaccharides have been reported among cereals and cultivars of a given species. In this work, the spatial distribution of AX and BG in the endosperm of mature grains was established for nine wheat varieties and eight barley varieties using enzymatically assisted mass spectrometry imaging (MSI). Important structural features of the AX and BG polymers that were previously shown to influence their physicochemical properties were assessed. Differences in the distribution of AX and BG structures were observed, both within the endosperm of a given cultivar and between wheat and barley cultivars. This study provides a unique picture of the structural heterogeneity of AX and BG polysaccharides at the scale of the whole endosperm in a series of wheat and barley cultivars. Thus, it can participate meaningfully in a strategy aiming at understanding the structure-function relationships of these two polymers.

  12. Post-main-sequence Evolution of Icy Minor Planets. III. Water Retention in Dwarf Planets and Exomoons and Implications for White Dwarf Pollution

    SciTech Connect

    Malamud, Uri; Perets, Hagai B., E-mail: uri.mal@tx.technion.ac.il, E-mail: hperets@physics.technion.ac.il

    2017-11-01

    Studies suggest that the pollution of white dwarf (WD) atmospheres arises from the accretion of minor planets, but the exact properties of polluting material, and in particular the evidence for water in some cases are not yet understood. Several previous works studied the possibility of water surviving inside minor planets around evolving stars. However, they all focused on small, comet-sized to moonlet-sized minor planets, when the inferred mass inside the convection zones of He-dominated WDs could actually be compatible with much more massive minor planets. Here we explore for the first time, the water retention inside exoplanetary dwarf planets, ormore » moderate-sized moons, with radii of the order of hundreds of kilometers. This paper concludes a series of papers that has now covered nearly the entire potential mass range of minor planets, in addition to the full mass range of their host stars. We find that water retention is (a) affected by the mass of the WD progenitor, and (b) it is on average at least 5%, irrespective of the assumed initial water composition, if it came from a single accretion event of an icy dwarf planet or moon. The latter prediction strengthens the possibility of habitability in WD planetary systems, and it may also be used in order to distinguish between pollution originating from multiple small accretion events and singular large accretion events. To conclude our work, we provide a code that calculates ice and water retention by interpolation and may be freely used as a service to the community.« less

  13. Post-main-sequence Evolution of Icy Minor Planets. III. Water Retention in Dwarf Planets and Exomoons and Implications for White Dwarf Pollution

    NASA Astrophysics Data System (ADS)

    Malamud, Uri; Perets, Hagai B.

    2017-11-01

    Studies suggest that the pollution of white dwarf (WD) atmospheres arises from the accretion of minor planets, but the exact properties of polluting material, and in particular the evidence for water in some cases are not yet understood. Several previous works studied the possibility of water surviving inside minor planets around evolving stars. However, they all focused on small, comet-sized to moonlet-sized minor planets, when the inferred mass inside the convection zones of He-dominated WDs could actually be compatible with much more massive minor planets. Here we explore for the first time, the water retention inside exoplanetary dwarf planets, or moderate-sized moons, with radii of the order of hundreds of kilometers. This paper concludes a series of papers that has now covered nearly the entire potential mass range of minor planets, in addition to the full mass range of their host stars. We find that water retention is (a) affected by the mass of the WD progenitor, and (b) it is on average at least 5%, irrespective of the assumed initial water composition, if it came from a single accretion event of an icy dwarf planet or moon. The latter prediction strengthens the possibility of habitability in WD planetary systems, and it may also be used in order to distinguish between pollution originating from multiple small accretion events and singular large accretion events. To conclude our work, we provide a code that calculates ice and water retention by interpolation and may be freely used as a service to the community.

  14. Variations on Debris Disks: Icy Planet Formation at 30-150 AU for 1-3 M⊙ Main-Sequence Stars

    NASA Astrophysics Data System (ADS)

    Kenyon, Scott J.; Bromley, Benjamin C.

    2008-12-01

    We describe calculations for the formation of icy planets and debris disks at 30-150 AU around 1-3 M⊙ stars. Debris disk formation coincides with the formation of planetary systems. As protoplanets grow, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk. Stellar lifetimes and the collisional cascade limit the growth of protoplanets. The maximum radius of icy planets, rmax ≈ 1750 km, is remarkably independent of initial disk mass, stellar mass, and stellar age. These objects contain lesssim3%-4% of the initial mass in solid material. Collisional cascades produce debris disks with maximum luminosity ~2 × 10-3 times the stellar luminosity. The peak 24 μm excess varies from ~1% times the stellar photospheric flux for 1 M⊙ stars to ~50 times the stellar photospheric flux for 3 M⊙ stars. The peak 70-850 μm excesses are ~30-100 times the stellar photospheric flux. For all stars, the 24-160 μm excesses rise at stellar ages of 5-20 Myr, peak at 10-50 Myr, and then decline. The decline is roughly a power law, f propto t-n with n ≈ 0.6-1.0. This predicted evolution agrees with published observations of A-type and solar-type stars. The observed far-IR color evolution of A-type stars also matches model predictions.

  15. Pattern of phylogenetic diversification of the Cychrini ground beetles in the world as deduced mainly from sequence comparisons of the mitochondrial genes.

    PubMed

    Su, Zhi-Hui; Imura, Yûki; Okamoto, Munehiro; Osawa, Syozo

    2004-02-04

    The phylogenetic position of the tribe Cychrini within the subfamily Carabinae (the family Carabidae) was estimated by comparing the nucleotide sequences of the mitochondrial NADH dehydrogenase subunit 5 (ND5) gene and the nuclear 28S ribosomal DNA (rDNA). The phylogenetic trees suggest that the Cychrini would most probably be the oldest line within the Carabinae. Phylogenetic trees were constructed by comparing the mitochondrial cytochrome C oxidase subunit I (COI) gene sequences from 33 species of the Cychrini from various localities that include the whole distribution ranges of the representative species within all the known genera in the world. The trees suggest that the Cychrini members radiated into a number of phylogenetic lineages within a short period, starting about 44 million years ago (MYA). Most of the phylogenetic lineages or sublineages are geographically linked, each consisting of a single or only a few species without scarce morphological differentiation in spite of their long evolutionary histories (silent or near-silent evolution [see Adv. Biophys. 36 (1999) 65; J. Mol. Evol. 53 (2001) 517]). The fact suggests that the geographic isolation per se did not bring about conspicuous morphological differentiation. The phylogenetic lineages of the Cychrini well correspond to the taxonomically defined genera and the subgenera.

  16. The optical + infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association

    NASA Astrophysics Data System (ADS)

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

    2018-01-01

    We present the results of photometric and spectroscopic follow-ups of the lowest mass member candidates in the nearest OB association, Upper Scorpius (∼5-10 Myr; 145 ± 17 pc), with the Gran Telescopio de Canarias (GTC) and European Southern Observatory (ESO) Very Large Telescope (VLT). We confirm the membership of the large majority (>80 per cent) of candidates originally selected photometrically and astrometrically based on their spectroscopic features, weak equivalent widths of gravity-sensitive doublets and radial velocities. Confirmed members follow a sequence over a wide magnitude range (J = 17.0-19.3 mag) in several colour-magnitude diagrams with optical, near- and mid-infrared photometry and have near-infrared spectral types in the L1-L7 interval with likely masses below 15 Jupiter masses. We find that optical spectral types tend to be earlier than near-infrared spectral types by a few subclasses for spectral types later than M9. We investigate the behaviour of spectral indices, defined in the literature as a function of spectral type and gravity, by comparison with values reported in the literature for young and old dwarfs. We also derive effective temperatures in the 1900-1600 K range from fits of synthetic model-atmosphere spectra to the observed photometry, but we caution that the procedure carries large uncertainties. We determine bolometric corrections for young L dwarfs with ages of ∼5-10 Myr (Upper Sco association) and find them to be similar in the J band but larger by 0.1-0.4 mag in the K band with respect to field L dwarfs. Finally, we discover two faint young L dwarfs, Visible and Infrared Survey Telescope for Astronomy (VISTA) J1607-2146 (L4.5) and VISTA J1611-2215 (L5), that have Hα emission and possible flux excesses at 4.5 μm, pointing to the presence of accretion from a disc on to the central objects of mass below ∼15MJup at an age of 5-10 Myr.

  17. X-SHOOTER OBSERVATIONS OF MAIN-SEQUENCE STARS IN THE GLOBULAR CLUSTER NGC 2808: FIRST CHEMICAL TAGGING OF A He-NORMAL AND A He-RICH DWARF

    SciTech Connect

    Bragaglia, A.; Carretta, E.; Gratton, R. G.

    2010-09-01

    We present the first chemical composition study of two unevolved stars in the globular cluster NGC 2808, obtained with the X-shooter spectrograph at VLT. NGC 2808 shows three discrete, well-separated main sequences. The most accepted explanation for this phenomenon is that their stars have different helium contents. We observed one star on the bluest main sequence (bMS, claimed to have a high helium content, Y {approx}0.4) and the other on the reddest main sequence (rMS, consistent with a canonical helium content, Y = 0.245). We analyzed features of NH, CH, Na, Mg, Al, and Fe. While Fe, Ca, and othermore » elements have the same abundances in the two stars, the bMS star shows a huge enhancement of N, a depletion of C, an enhancement of Na and Al, and a small depletion of Mg with respect to the rMS star. This is exactly what is expected if stars on the bMS formed from the ejecta produced by an earlier stellar generation in the complete CNO and MgAl cycles whose main product is helium. The elemental abundance pattern differences in these two stars are consistent with the differences in the helium content suggested by the color-magnitude diagram positions of the stars.« less

  18. Identification and quantification of the main isoflavones and other phytochemicals in soy based nutraceutical products by liquid chromatography-orbitrap high resolution mass spectrometry.

    PubMed

    López-Gutiérrez, Noelia; Romero-González, Roberto; Garrido Frenich, Antonia; Martínez Vidal, José Luis

    2014-06-27

    The specific phytochemicals composition of soy nutritional supplements is usually not labelled. Hence, 12 dietary supplements were analyzed in order to detect and identify the main phytochemicals present in these samples, using a database containing 60 compounds. Ultra-high performance liquid chromatography coupled to single-stage Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap-MS) has been used. Two consecutive extractions, using as extraction solvent a mixture of methanol:water (80:20, v/v), were employed, followed by two dilutions (10 or 100 times depending on the concentration of the components in the sample) with a mixture of an aqueous solution of ammonium acetate 30mM:methanol (50:50, v/v). The method was validated, obtaining adequate recovery and precision values. Limits of detection (LODs) and quantification (LOQs) were calculated, ranging from 2 to 150μgL(-1). Isoflavones were the predominant components present in the analyzed supplements with values higher than 93% of the total amount of phytochemicals in all cases. The aglycones (genistein, daidzein, glycitein and biochanin A) as well as their three conjugated forms, β-glucosides (genistin, daizin and glycitin) were detected and quantified, being daidzein the isoflavone detected at higher concentration in 8 out of 12 samples reported, with values ranging from 684 to 35,970mgkg(-1), whereas biochanin A was detected at very low concentrations, ranging from 18 to 50mgkg(-1). Moreover, other phytochemicals as flavones, flavonols, flavanones and phenolic acids were also detected and quantified. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Simultaneous analysis of the main markers of nitrogen status in dairy cow's urine using hydrophilic interaction chromatography and tandem mass spectrometry detection.

    PubMed

    Boudra, H; Doreau, M; Noziere, P; Pujos-Guillot, E; Morgavi, D P

    2012-09-21

    Microbial protein synthesis and nitrogen balance status in ruminants can be evaluated by the presence of metabolites in urine. This work aims to develop and validate a simple and sensitive method for simultaneous determination of nine markers of nitrogen status in ruminant's urine using hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The LC-ESI-MS/MS system, operated in multiple reaction monitoring (MRM) in positive mode, was used for determining selected purine (allantoin, uric acid, xanthine, and hypoxanthine) and pyrimidine derivatives (β-aminobutyric acid and β-alanine), which are used to estimate rumen microbial protein synthesis - the main source of protein for ruminants. Creatinine, creatine and urea, three other metabolites involved in nitrogen metabolism were also measured by this method. The procedure was based on a simple dilution of urine samples in acetonitrile, followed by LC-ESI-MS/MS analysis. Chromatographic separation was tested with three different columns. A zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) column provided an optimal separation for all metabolites. Precision of the method was typically below 10%, and accuracy was above 90% with the exceptions of allantoin and urea at pH 6 and 3, and β-alanine at pH 3. Metabolites were stable after 3 months of storage at -20°C, except for xanthine, hypoxanthine and β-aminobutyric acid that lost up to 48, 50 and 39% of initial concentration after only 1month of storage in acidified urine. This LC-ESI-MS/MS method is more specific, unequivocally detecting target metabolites at lower detection limits than methods using UV detection. The method was suitable for the determination of all metabolites tested. The developed method was subsequently used to compare total and spot urine sampling obtained from dairy cows fed diets with contrasting levels of protein. Copyright © 2012 Elsevier B.V. All rights

  20. Sensitive determination of THC and main metabolites in human plasma by means of microextraction in packed sorbent and gas chromatography-tandem mass spectrometry.

    PubMed

    Rosado, T; Fernandes, L; Barroso, M; Gallardo, E

    2017-02-01

    Cannabis is one of the most available and consumed illicit drug in the world and its identification and quantification in biological specimens can be a challenge given its low concentrations in body fluids. The present work describes a fast and fully validated procedure for the simultaneous detection and quantification of ▵ 9 -tetrahydrocannabinol (▵ 9_ THC) and its two main metabolites 11-hydroxy ▵ 9_ tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-▵ 9 - tetrahydrocannbinol (THC-COOH) in plasma samples using microextraction by packed sorbent (MEPS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). A small plasma volume (0.25mL) pre-diluted (1:20), was extracted with MEPS M1 sorbent as follows: conditioning (4 cycles of 250μL methanol and 4 cycles of 250μL 0.1% formic acid in water); sample load (26 cycles of 250μL); wash (100μL of 3% acetic acid in water followed by 100μL 5% methanol in water); and elution (6 cycles of 100μL of 10% ammonium hydroxide in methanol). The procedure allowed the quantification of all analytes in the range of 0.1-30ng/mL. Recoveries ranged from 53 to 78% (THC), 57 to 66% (11-OH-THC) and 62 to 65% (THC-COOH), allowing the limits of detection and quantification to be set at 0.1ng/mL for all compounds. Intra-day precision and accuracy revealed coefficients of variation (CVs) lower than 10% at the studied concentrations, with a mean relative error within±9%, while inter-day precision and accuracy showed CVs lower than 15% for all analytes at the tested concentrations, with an inaccuracy within±8%. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. UVnovo: A De Novo Sequencing Algorithm Using Single Series of Fragment Ions via Chromophore Tagging and 351 nm Ultraviolet Photodissociation Mass Spectrometry

    PubMed Central

    Robotham, Scott A.; Horton, Andrew P.; Cannon, Joe R.; Cotham, Victoria C.; Marcotte, Edward M.; Brodbelt, Jennifer S.

    2016-01-01

    De novo peptide sequencing by mass spectrometry represents an important strategy for characterizing novel peptides and proteins, in which a peptide’s amino acid sequence is inferred directly from the precursor peptide mass and tandem mass spectrum (MS/MS or MS3) fragment ions, without comparison to a reference proteome. This method is ideal for organisms or samples lacking a complete or well-annotated reference sequence set. One of the major barriers to de novo spectral interpretation arises from confusion of N- and C-terminal ion series due to the symmetry between b and y ion pairs created by collisional activation methods (or c, z ions for electron-based activation methods). This is known as the ‘antisymmetric path problem’ and leads to inverted amino acid subsequences within a de novo reconstruction. Here, we combine several key strategies for de novo peptide sequencing into a single high-throughput pipeline: high efficiency carbamylation blocks lysine side chains, and subsequent tryptic digestion and N-terminal peptide derivatization with the ultraviolet chromophore AMCA yields peptides susceptible to 351 nm ultraviolet photodissociation (UVPD). UVPD-MS/MS of the AMCA-modified peptides then predominantly produces y ions in the MS/MS spectra, specifically addressing the antisymmetric path problem. Finally, the program UVnovo applies a random forest algorithm to automatically learn from and then interpret UVPD mass spectra, passing results to a hidden Markov model for de novo sequence prediction and scoring. We show this combined strategy provides high performance de novo peptide sequencing, enabling the de novo sequencing of thousands of peptides from an E. coli lysate at high confidence. PMID:26938041

  2. Variability of Disk Emission in Pre-Main Sequence and Related Stars. II. Variability in the Gas and Dust Emission of the Herbig Fe Star SAO 206462

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Day, Amanda N.; Kimes, Robin L.; Beerman, Lori C.; Martus, Cameron; Lynch, David K.; Russell, Ray W.; Grady, Carol A.; Schneider, Glenn; Lisse, Carey M.; hide

    2011-01-01

    We present thirteen epochs of near-infrared (0.8-5 microns) spectroscopic observations of the pre-transitional, "gapped" disk system in SAO 206462 (=HD 135344B). In all, six gas emission lines (Br(alpha) , Br(gamma), Pa(beta), Pa(delta), Pa(epsilon), and the 0.8446 microns line of O I) along with continuum measurements made near the standard J, H, K, and L photometric bands were measured. A mass accretion rate of approximately 2 x 10(exp 8)Solar Mass/yr was derived from the Br(gamma) and Pa(beta) lines. However, the fluxes of these lines varied by a factor of over two during the course of a few months. The continuum also varied, but by only approx.30%, and even decreased at a time when the gas emission was increasing. The H I line at 1.083 microns was also found to vary in a manner inconsistent with that of either the hydrogen lines or the dust. Both the gas and dust variabilities indicate significant changes in the region of the inner gas and the inner dust belt that may be common to many young disk systems. If planets are responsible for defining the inner edge of the gap, they could interact with the material on time scales commensurate with what is observed for the variations in the dust, while other disk instabilities (thermal, magneto-rotational) would operate there on longer time scales than we observe for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3 years. If the changes are being induced in the disk material closer to the star than the gap, a variety of mechanisms (disk instabilities, interactions via planets) might be responsible for the changes seen. The He I feature is most likely due to a wind whose orientation changes with respect to the observer on time scales of a day or less. To further constrain the origin of the gas and dust emission will require multiple spectroscopic and interferometric observations on both shorter and longer time scales that have been sampled so far.

  3. Photospheric Acne at The Bottom of the Main-Sequence: Doppler Images of M4.5 - M9V Stars

    NASA Astrophysics Data System (ADS)

    Barnes, John R.; Haswell, Carole A.; Jeffers, Sandra V.; Jones, Hugh R. A.; Pavlenko, Yakiv V.; Lohr, Marcus E.; Jenkins, James S.

    2016-07-01

    Starspots are an important manifestation of stellar activity and yet their distribution patterns on the lowest mass stars is notwell known. Time series spectra of fullyconvective M dwarfs taken in the red-optical with UVES reveal numerous line profiledistortions which are interpreted as starspots. New Doppler images of HU Del (GJ 791.2A; M4.5V), BL Ceti (GJ 65A; M5.5V)and UV Ceti (GJ 65B; M6V) attwoepochs separated by three nights are presented. We find that contrastratioscorrespondingto photosphere-spot temperature differences of only 100-400 Kare sufficient to model the time series spectra of M4.5V - M9Vstars. Starspotsare reconstructed at a range of phases and latitudes with mean spot filling factors of only a few per cent.The distribution and low-contrast of the spots/spot-groups that we recover are likely to be responsible for the low amplitudephotometric variability seen in late-M dwarfs. The stability of the spot patterns in the two sets of timeseries observationsenables us to measure the latitude dependent differential rotation, which we find to be consistent with zero.

  4. Variability of Disk Emission in Pre-main-sequence and Related Stars. IV. Investigating the Structural Changes in the Inner Disk Region of MWC 480

    NASA Astrophysics Data System (ADS)

    Fernandes, Rachel B.; Long, Zachary C.; Pikhartova, Monika; Sitko, Michael L.; Grady, Carol A.; Russell, Ray W.; Luria, David M.; Tyler, Dakotah B.; Bayyari, Ammar; Danchi, William; Wisniewski, John P.

    2018-04-01

    We present five epochs of near-IR observations of the protoplanetary disk around MWC 480 (HD 31648) obtained with the SpeX spectrograph on NASA’s Infrared Telescope Facility between 2007 and 2013, inclusive. Using the measured line fluxes in the Pa β and Br γ lines, we found the mass accretion rates to be (1.26–2.30) × 10‑7 M ⊙ yr‑1 and (1.4–2.01) × 10‑7 M ⊙ yr‑1, respectively, but which varied by more than 50% from epoch to epoch. The spectral energy distribution reveals a variability of about 30% between 1.5 and 10 μm during this same period of time. We investigated the variability using of the continuum emission of the disk in using the Monte-Carlo Radiative Transfer Code HOCHUNK3D. We find that varying the height of the inner rim successfully produces a change in the NIR flux but lowers the far-IR emission to levels below all measured fluxes. Because the star exhibits bipolar flows, we utilized a structure that simulates an inner disk wind to model the variability in the near-IR, without producing flux levels in the far-IR that are inconsistent with existing data. For this object, variable near-IR emission due to such an outflow is more consistent with the data than changing the scale height of the inner rim of the disk.

  5. Purification, characterization, sequence determination, and mass spectrometric analysis of a trypsin inhibitor from seeds of the Brazilian tree Dipteryx alata (Leguminosae).

    PubMed

    Kalume, D E; Sousa, M V; Morhy, L

    1995-11-01

    Dipteryx alata trypsin inhibitor (DATI) has been purified and completely sequenced. It showed homology to members of the Bowman-Birk family of inhibitors. The last step of DATI purification by RP-HPLC (narrow-borc C18 column) suggested the existence of some isoforms of the inhibitor due to the presence of a cluster of very close peaks in the chromatogram. By using electrospray ionization mass spectrometry (ESIMS) and laser desorption mass spectrometry (LDIMS), the identification of DATI isoforms was made possible. From the ESIMS data, the following molecular masses were found: 6803.22 +/- 0.92 for isoform a; 6890.94 +/- 0.73 for b; 6977.58 +/- 0.39 for c; 7065.07 +/- 0.67 for d; 7151.42 +/- 0.86 for e; and 7291.70 +/- 0.43 for f. Similar masses were found when using LDIMS. Isoform b was the most abundant and its molecular mass matched the molecular mass of 6893 calculated from the sequence of DATI. The mass differences between a and b, b and c, c and d, and d and e were equal to 87, which corresponds to Ser. Isoform a might not have the N-terminal Ser present in isoform b, while the other additional Ser residues might comprise a row localized in the C- or N-terminal. The appearance of all these isoforms could result from posttranslational N- and C-terminal processing.

  6. Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67

    NASA Astrophysics Data System (ADS)

    Souto, Diogo; Cunha, Katia; Smith, Verne V.; Allende Prieto, C.; García-Hernández, D. A.; Pinsonneault, Marc; Holzer, Parker; Frinchaboy, Peter; Holtzman, Jon; Johnson, J. A.; Jönsson, Henrik; Majewski, Steven R.; Shetrone, Matthew; Sobeck, Jennifer; Stringfellow, Guy; Teske, Johanna; Zamora, Olga; Zasowski, Gail; Carrera, Ricardo; Stassun, Keivan; Fernandez-Trincado, J. G.; Villanova, Sandro; Minniti, Dante; Santana, Felipe

    2018-04-01

    Detailed chemical abundance distributions for 14 elements are derived for eight high-probability stellar members of the solar metallicity old open cluster M67 with an age of ∼4 Gyr. The eight stars consist of four pairs, with each pair occupying a distinct phase of stellar evolution: two G dwarfs, two turnoff stars, two G subgiants, and two red clump (RC) K giants. The abundance analysis uses near-IR high-resolution spectra (λ1.5–1.7 μm) from the Apache Point Observatory Galactic Evolution Experiment survey and derives abundances for C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe. Our derived stellar parameters and metallicity for 2M08510076+1153115 suggest that this star is a solar twin, exhibiting abundance differences relative to the Sun of ≤0.04 dex for all elements. Chemical homogeneity is found within each class of stars (∼0.02 dex), while significant abundance variations (∼0.05–0.20 dex) are found across the different evolutionary phases; the turnoff stars typically have the lowest abundances, while the RCs tend to have the largest. Non-LTE corrections to the LTE-derived abundances are unlikely to explain the differences. A detailed comparison of the derived Fe, Mg, Si, and Ca abundances with recently published surface abundances from stellar models that include chemical diffusion provides a good match between the observed and predicted abundances as a function of stellar mass. Such agreement would indicate the detection of chemical diffusion processes in the stellar members of M67.

  7. Simultaneous quantification of 5 main components of Psoralea corylifolia L. in rats' plasma by utilizing ultra high pressure liquid chromatography tandem mass spectrometry.

    PubMed

    Gao, Qianqian; Xu, Zisheng; Zhao, Genhua; Wang, Heng; Weng, Zebin; Pei, Ke; Wu, Li; Cai, Baochang; Chen, Zhipeng; Li, Weidong

    2016-02-01

    Psoralea corylifolia L. has long been used in traditional Chinese medicine for treating and preventing many diseases. A group of flavonoid components are regarded as the active principals within the seeds. In this research, a rapid, accurate and sensitive ultra high pressure liquid chromatography tandem mass spectrometry (UHPLC/MS/MS) method has been established for simultaneous quantification of its 5 main components, namely, neobavaisoflavone, bavachin, isobavachalcone, bavachinin and corylifol A in rats' plasma after the rats were orally administrated with Buguzhi extract. Negative ion electrospray mode was applied in the detection process. Multiple reactions monitoring (MRM) mode was utilized for simultaneous quantitative analyzing of neobavaisoflavone (m/z 321.1→m/z 265.1), bavachin (m/z 323.1→m/z 119.0), isobavachalcone (m/z 323.2→m/z 119.0), bavachinin (m/z 337.2→m/z 119.0), corylifol A (m/z 389.2→m/z 277.0) and liquiritigenin (Internal Standard, m/z 255.1→m/z 119.0). Chromatographic separation of the above mentioned components was conducted on a Waters BEH-C18 column (100 mm×2.1mm, 1.7μm) with gradient elution system at flow rate of 0.3mL/min. The mobile phase was composed of acetonitrile and 0.1% formic acid solution. The lower limit of quantification (LLOQ) for each of the above analytes was 0.5ng/mL. Each of the analytes exhibited good linearity within the concentration range of 0.5-100ng/mL. The method was fully validated for its selectivity, accuracy, precision, stability, matrix effect and extraction recovery. The validated method has been successfully applied for simultaneous determination of the 5 flavonoids in rat plasma for the first time. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Distribution of net-collected planktonic cnidarians along the northern Mid-Atlantic Ridge and their associations with the main water masses

    NASA Astrophysics Data System (ADS)

    Hosia, A.; Stemmann, L.; Youngbluth, M.

    2008-01-01

    Planktonic cnidarians and ctenophores were sampled with a multiple opening-closing net (Multinet) as well as a non-quantitative plankton net along the northern Mid-Atlantic Ridge (MAR) between Iceland and the Azores. Sixty-four species or genera of planktonic cnidarians (38 siphonophora, 21 hydromedusae, 5 scyphomedusae) and one genus of ctenophore were collected. Of these, Leuckartiara adnata and Clausophyes laetmata were new records for the area. Multinet samples collected from depths of 0-100, 100-500, 500-1000, 1000-1500 and 1500-2500 m at 11 stations were compared. Multivariate analysis of the data indicated that species composition and abundance along the ridge varied with the dominant water masses, with changes in the cnidarian zooplankton assemblage observed with regard to geographic location as well as depth. The surface waters of the two northernmost stations characterized by modified North Atlantic Water (MNAW) as well as the three southernmost stations characterized by North Atlantic Central Water (NACW) exhibited relatively high abundances (3284-13,915 individuals·1000 m -3) in the upper 100 m. No such peak was evident at the middle stations characterized by Subarctic Intermediate Water (SAIW), where the abundances in the upper three depth strata were consistently lower (57-863 individuals·1000 m -3). Across the study area, the lowest abundances were found in the 1500-2500 m stratum (0-56 ind.·1000 m -3). The main divergence in the species composition and abundance of planktonic cnidarians was observed at the Subpolar Front (SPF), which marked the boundary for the distribution of many species. The divergence at the SPF was strongest in the upper 500 m but observable down to 1500 m. Profoundly different epipelagic species assemblages were observed in SAIW and NACW on opposite sides of the SPF, with the distribution of several species of calycophoran siphonophores confined to the southern NACW. At mid-water depths, the species composition north of the

  9. Atypical yeasts identified as Saccharomyces cerevisiae by MALDI-TOF MS and gene sequencing are the main responsible of fermentation of chicha, a traditional beverage from Peru.

    PubMed

    Vallejo, Juan Andrés; Miranda, Patricia; Flores-Félix, José David; Sánchez-Juanes, Fernando; Ageitos, José M; González-Buitrago, José Manuel; Velázquez, Encarna; Villa, Tomás G

    2013-12-01

    Chicha is a drink prepared in several Andean countries from Inca's times by maize fermentation. Currently this fermentation is carried out in familiar artesanal "chicherías" that make one of the most known types of chicha, the "chicha de jora". In this study we isolate and identify the yeasts mainly responsible of the fermentation process in this type of chicha in 10 traditional "chicherías" in Cusco region in Peru. We applied by first time MALDI-TOF MS analysis for the identification of yeast of non-clinic origin and the results showed that all of yeast strains isolated belong to the species Saccharomyces cerevisiae. These results agree with those obtained after the analysis of the D1/D2 and 5.8S-ITS regions. However the chicha strains have a phenotypic profile that differed in more than 40% as compared to that of current S. cerevisiae strains. To the best of our knowledge this is the first report concerning the yeasts involved in chicha fermentation. Copyright © 2013 Elsevier GmbH. All rights reserved.

  10. Mouse liver NAD(P)H:quinone acceptor oxidoreductase: protein sequence analysis by tandem mass spectrometry, cDNA cloning, expression in Escherichia coli, and enzyme activity analysis.

    PubMed Central

    Chen, S.; Clarke, P. E.; Martino, P. A.; Deng, P. S.; Yeh, C. H.; Lee, T. D.; Prochaska, H. J.; Talalay, P.

    1994-01-01

    The amino acid sequence of mouse liver NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2) has been determined by tandem mass spectrometry and deduced from the nucleotide sequence of the cDNA encoding for the enzyme. The electrospray mass spectral analyses revealed, as previously reported (Prochaska HJ, Talalay P, 1986, J Biol Chem 261:1372-1378), that the 2 forms--the hydrophilic and hydrophobic forms--of the mouse liver quinone reductase have the same molecular weight. No amino acid sequence differences were found by tandem mass spectral analyses of tryptic peptides of the 2 forms. Moreover, the amino-termini of the mouse enzymes are acetylated as determined by tandem mass spectrometry. Further, only 1 cDNA species encoding for the quinone reductase was found. These results suggest that the 2 forms of the mouse quinone reductase have the same primary sequences, and that any difference between the 2 forms may be attributed to a labile posttranslational modification. Analysis of the mouse quinone reductase cDNA revealed that the enzyme is 273 amino acids long and has a sequence homologous to those of rat and human quinone reductases. In this study, the mouse quinone reductase cDNA was also ligated into a prokaryotic expression plasmid pKK233.2, and the constructed plasmid was used to transform Escherichia coli strain JM109. The E. coli-expressed mouse quinone reductase was purified and characterized. Although mouse quinone reductase has an amino acid sequence similar to those of the rat and human enzymes, the mouse enzyme has a higher NAD(P)H-menadione reductase activity and is less sensitive to flavones and dicoumarol, 2 known inhibitors of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7527260

  11. Front-End Electron Transfer Dissociation Coupled to a 21 Tesla FT-ICR Mass Spectrometer for Intact Protein Sequence Analysis

    NASA Astrophysics Data System (ADS)

    Weisbrod, Chad R.; Kaiser, Nathan K.; Syka, John E. P.; Early, Lee; Mullen, Christopher; Dunyach, Jean-Jacques; English, A. Michelle; Anderson, Lissa C.; Blakney, Greg T.; Shabanowitz, Jeffrey; Hendrickson, Christopher L.; Marshall, Alan G.; Hunt, Donald F.

    2017-09-01

    High resolution mass spectrometry is a key technology for in-depth protein characterization. High-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) enables high-level interrogation of intact proteins in the most detail to date. However, an appropriate complement of fragmentation technologies must be paired with FTMS to provide comprehensive sequence coverage, as well as characterization of sequence variants, and post-translational modifications. Here we describe the integration of front-end electron transfer dissociation (FETD) with a custom-built 21 tesla FT-ICR mass spectrometer, which yields unprecedented sequence coverage for proteins ranging from 2.8 to 29 kDa, without the need for extensive spectral averaging (e.g., 60% sequence coverage for apo-myoglobin with four averaged acquisitions). The system is equipped with a multipole storage device separate from the ETD reaction device, which allows accumulation of multiple ETD fragment ion fills. Consequently, an optimally large product ion population is accumulated prior to transfer to the ICR cell for mass analysis, which improves mass spectral signal-to-noise ratio, dynamic range, and scan rate. We find a linear relationship between protein molecular weight and minimum number of ETD reaction fills to achieve optimum sequence coverage, thereby enabling more efficient use of instrument data acquisition time. Finally, real-time scaling of the number of ETD reactions fills during method-based acquisition is shown, and the implications for LC-MS/MS top-down analysis are discussed. [Figure not available: see fulltext.

  12. VARIABILITY OF DISK EMISSION IN PRE-MAIN SEQUENCE AND RELATED STARS. II. VARIABILITY IN THE GAS AND DUST EMISSION OF THE HERBIG Fe STAR SAO 206462

    SciTech Connect

    Sitko, Michael L.; Day, Amanda N.; Kimes, Robin L.

    2012-01-20

    We present 13 epochs of near-infrared (0.8-5 {mu}m) spectroscopic observations of the pre-transitional, 'gapped' disk system in SAO 206462 (=HD 135344B). In all, six gas emission lines (Br{alpha}, Br{gamma}, Pa{beta}, Pa{gamma}, Pa{delta}, Pa{epsilon}, and the 0.8446 {mu}m line of O I) along with continuum measurements made near the standard J, H, K, and L photometric bands were measured. A mass accretion rate of approximately 2 Multiplication-Sign 10{sup -8} M{sub Sun} yr{sup -1} was derived from the Br{gamma} and Pa{beta} lines. However, the fluxes of these lines varied by a factor of over two during the course of a few months.more » The continuum also varied, but by only {approx}30%, and even decreased at a time when the gas emission was increasing. The H I line at 1.083 {mu}m was also found to vary in a manner inconsistent with that of either the hydrogen lines or the dust. Both the gas and dust variabilities indicate significant changes in the region of the inner gas and the inner dust belt that may be common to many young disk systems. If planets are responsible for defining the inner edge of the gap, they could interact with the material on timescales commensurate with what is observed for the variations in the dust, while other disk instabilities (thermal, magnetorotational) would operate there on longer timescales than we observe for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3 years. If the changes are being induced in the disk material closer to the star than the gap, a variety of mechanisms (disk instabilities, interactions via planets) might be responsible for the changes seen. The He I feature is most likely due to a wind whose orientation changes with respect to the observer on timescales of a day or less. To further constrain the origin of the gas and dust emission will require multiple spectroscopic and interferometric observations on both shorter and longer timescales that have been sampled so far.« less

  13. Variability in stellar granulation and convective blueshift with spectral type and magnetic activity . II. From young to old main-sequence K-G-F stars

    NASA Astrophysics Data System (ADS)

    Meunier, N.; Mignon, L.; Lagrange, A.-M.

    2017-11-01

    Context. The inhibition of small-scale convection in the Sun dominates the long-term radial velocity (RV) variability: it therefore has a critical effect on light exoplanet detectability using RV techniques. Aims: We here extend our previous analysis of stellar convective blueshift and its dependence on magnetic activity to a larger sample of stars in order to extend the Teff range, to study the impact of other stellar properties, and finally to improve the comparison between observed RV jitter and expected RV variations. Methods: We estimate a differential velocity shift for Fe and Ti lines of different depths and derive an absolute convective blueshift using the Sun as a reference for a sample of 360 F7-K4 stars with different properties (age, Teff, metallicity). Results: We confirm the strong variation in convective blueshift with Teff and its dependence on (as shown in the line list in Paper I) activity level. Although we do not observe a significant effect of age or cyclic activity, stars with a higher metallicity tend to have a lower convective blueshift, with a larger effect than expected from numerical simulations. Finally, we estimate that for 71% of the stars in our sample the RV and Log R' _HK variations are compatible with the effect of activity on convection, as observed in the solar case, while for the other stars, other sources (such as binarity or companions) must be invoked to explain the large RV variations. We also confirm a relationship between Log R' _HK and metallicity, which may affect discussions of the possible relationship between metallicity and exoplanets, as RV surveys are biased toward low Log R' _HK and possibly toward high-metallicity stars. Conclusions: We conclude that activity and metallicity strongly affect the small-scale convection levels in stars in the F7-K4 range, with a lower amplitude for the lower mass stars and a larger amplitude for low-metallicity stars. Full Table A.1 is only available at the CDS via anonymous ftp to

  14. Main Report

    PubMed Central

    2006-01-01

    Background: States vary widely in their use of newborn screening tests, with some mandating screening for as few as three conditions and others mandating as many as 43 conditions, including varying numbers of the 40+ conditions that can be detected by tandem mass spectrometry (MS/MS). There has been no national guidance on the best candidate conditions for newborn screening since the National Academy of Sciences report of 19751 and the United States Congress Office of Technology Assessment report of 1988,2 despite rapid developments since then in genetics, in screening technologies, and in some treatments. Objectives: In 2002, the Maternal and Child Health Bureau (MCHB) of the Health Resources and Services Administration (HRSA) of the United States Department of Health and Human Services (DHHS) commissioned the American College of Medical Genetics (ACMG) to: Conduct an analysis of the scientific literature on the effectiveness of newborn screening.Gather expert opinion to delineate the best evidence for screening for specified conditions and develop recommendations focused on newborn screening, including but not limited to the development of a uniform condition panel.Consider other components of the newborn screening system that are critical to achieving the expected outcomes in those screened. Methods: A group of experts in various areas of subspecialty medicine and primary care, health policy, law, public health, and consumers worked with a steering committee and several expert work groups, using a two-tiered approach to assess and rank conditions. A first step was developing a set of principles to guide the analysis. This was followed by developing criteria by which conditions could be evaluated, and then identifying the conditions to be evaluated. A large and broadly representative group of experts was asked to provide their opinions on the extent to which particular conditions met the selected criteria, relying on supporting evidence and references from the

  15. Maine Ingredients

    ERIC Educational Resources Information Center

    Waters, John K.

    2009-01-01

    This article features Maine Learning Technology Initiative (MLTI), the nation's first-ever statewide 1-to-1 laptop program which marks its seventh birthday by expanding into high schools, providing an occasion to celebrate--and to examine the components of its success. The plan to put laptops into the hands of every teacher and student in grades 7…

  16. The evolution of massive stars and their spectra. I. A non-rotating 60 M⊙ star from the zero-age main sequence to the pre-supernova stage

    NASA Astrophysics Data System (ADS)

    Groh, Jose H.; Meynet, Georges; Ekström, Sylvia; Georgy, Cyril

    2014-04-01

    For the first time, the interior and spectroscopic evolution of a massive star is analyzed from the zero-age main sequence (ZAMS) to the pre-supernova (SN) stage. For this purpose, we combined stellar evolution models using the Geneva code and stellar atmospheric/wind models using CMFGEN. With our approach, we were able to produce observables, such as a synthetic high-resolution spectrum and photometry, thereby aiding the comparison between evolution models and observed data. Here we analyze the evolution of a non-rotating 60 M⊙ star and its spectrum throughout its lifetime. Interestingly, the star has a supergiant appearance (luminosity class I) even at the ZAMS. We find the following evolutionary sequence of spectral types: O3 I (at the ZAMS), O4 I (middle of the H-core burning phase), B supergiant (BSG), B hypergiant (BHG), hot luminous blue variable (LBV; end of H-core burning), cool LBV (H-shell burning through the beginning of the He-core burning phase), rapid evolution through late WN and early WN, early WC (middle of He-core burning), and WO (end of He-core burning until core collapse). We find the following spectroscopic phase lifetimes: 3.22 × 106 yr for the O-type, 0.34 × 105 yr (BSG), 0.79 × 105 yr (BHG), 2.35 × 105 yr (LBV), 1.05 × 105 yr (WN), 2.57 × 105 yr (WC), and 3.80 × 104 yr (WO). Compared to previous studies, we find a much longer (shorter) duration for the early WN (late WN) phase, as well as a long-lived LBV phase. We show that LBVs arise naturally in single-star evolution models at the end of the MS when the mass-loss rate increases as a consequence of crossing the bistability limit. We discuss the evolution of the spectra, magnitudes, colors, and ionizing flux across the star's lifetime, and the way they are related to the evolution of the interior. We find that the absolute magnitude of the star typically changes by ~6 mag in optical filters across the evolution, with the star becoming significantly fainter in optical filters at

  17. Atlas of the Immune Cell Repertoire in Mouse Atherosclerosis Defined by Single-Cell RNA-Sequencing and Mass Cytometry.

    PubMed

    Winkels, Holger; Ehinger, Erik; Vassallo, Melanie; Buscher, Konrad; Dinh, Huy; Kobiyama, Kouji; Hamers, Anouk; Cochain, Clément; Vafadarnejad, Ehsan; Saliba, Antoine-Emmanuel; Zernecke, Alma; Pramod, Akula; Ghosh, Amlan; Anto Michel, Nathaly; Hoppe, Natalie; Hilgendorf, Ingo; Zirlik, Andreas; Hedrick, Catherine; Ley, Klaus; Wolf, Dennis

    2018-03-15

    Rationale: Atherosclerosis is a chronic inflammatory disease that is driven by the interplay of pro- and anti-inflammatory leukocytes in the aorta. Yet, the phenotypic and transcriptional diversity of aortic leukocytes is only poorly understood. Objective: We characterized leukocytes from healthy and atherosclerotic mouse aortas in-depth by single cell RNA-sequencing (scRNAseq) and mass cytometry (CyTOF) to define an atlas of the immune cell landscape in atherosclerosis. Methods and Results: Employing scRNAseq of aortic leukocytes from chow (CD) and western diet (WD) fed Apoe -/- and Ldlr -/- mice, we detected 11 principal leukocyte clusters with distinct phenotypical and spatial characteristics, while the cellular repertoire in healthy aortas was less diverse. Gene set enrichment analysis on a single cell level established that multiple pathways, such as for lipid metabolism, proliferation, and cytokine secretion, were confined to particular leukocyte clusters. Leukocyte populations were differentially regulated in atherosclerotic Apoe -/- and Ldlr -/- mice. We confirmed the phenotypic diversity of these clusters with a novel CyTOF 35-marker panel with metal-labelled antibodies and conventional flow cytometry. Cell populations retrieved by these protein-based approaches were highly correlated to transcriptionally defined clusters. In an integrated screening strategy of scRNAseq, CyTOF, and FACS, we detected three principal B-cell subsets with alterations in surface markers, functional pathways, and in vitro cytokine secretion. Finally, we used leukocyte cluster gene signatures to enumerate leukocyte frequencies in 126 human plaques by a genetic deconvolution strategy. This approach revealed that human carotid plaques and microdissected mouse plaques were mostly populated by macrophages, T-cells, and monocytes. In addition, the frequency of genetically defined leukocyte populations in carotid plaques predicted cardiovascular events in patients. Conclusions: The

  18. Constraining the Low-Mass Slope of the Star Formation Sequence at 0.5≤z≤2.5

    NASA Astrophysics Data System (ADS)

    Whitaker, Katherine E.; Franx, Marijn; Leja, Joel; Van Dokkum, Pieter G.; Henry, Alaina L.; Skelton, Rosalind; Fumagalli, Mattia; Momcheva, Ivelina G.; Brammer, Gabriel; Labbe, Ivo; Nelson, Erica; Rigby, Jane R.; 3D-HST Collaboration

    2015-01-01

    A wealth of data from deep extragalactic surveys have revealed a picture where star-forming galaxies follow a tight relation between star formation rate and stellar mass. This observed star formation sequence encapsulates information about feedback, gas density and gas accretion rates over cosmic time. I will present a self-consistent empirical study measuring the slope of this relation for a complete sample of galaxies selected from the 3D-HST photometric catalogs at 0.5≤z≤2.5, using deep photometry in the CANDELS fields. Probing a factor of ten lower in stellar mass than previous high-redshift studies, we show that the slope of the star formation rate - stellar mass relation is mass-dependent; we measure a steep slope of order unity out to z=2.5 for low mass galaxies, and a slope that becomes increasingly flatter with time at the highest masses. These observations of the star formation sequence help reconcile existing tensions with theoretical galaxy formation models.

  19. The mass-lifetime relation

    NASA Astrophysics Data System (ADS)

    LoPresto, Michael C.

    2018-05-01

    In a recent "AstroNote," I described a simple exercise on the mass-luminosity relation for main sequence stars as an example of exposing students in a general education science course of lower mathematical level to the use of quantitative skills such as collecting and analyzing data. Here I present another attempt at a meaningful experience for such students that again involves both the gathering and analysis of numerical data and comparison with accepted result, this time on the relationship of the mass and lifetimes of main sequence stars. This experiment can stand alone or be used as an extension of the previous mass-luminosity relationship experiment.

  20. Serum betaine is inversely associated with low lean mass mainly in men in a Chinese middle-aged and elderly community-dwelling population.

    PubMed

    Huang, Bi-Xia; Zhu, Ying-Ying; Tan, Xu-Ying; Lan, Qiu-Ye; Li, Chun-Lei; Chen, Yu-Ming; Zhu, Hui-Lian

    2016-06-01

    Previous studies have demonstrated that betaine supplements increase lean body mass in livestock and improve muscle performance in human beings, but evidence for its effect on human lean mass is limited. Our study assessed the association of circulating betaine with lean mass and its composition in Chinese adults. A community-based study was conducted on 1996 Guangzhou residents (weight/mass: 1381/615) aged 50-75 years between 2008 and 2010. An interviewer-administered questionnaire was used to collect general baseline information. Fasting serum betaine was assessed using HPLC-MS. A total of 1590 participants completed the body composition analysis performed using dual-energy X-ray absorptiometry during a mean of 3·2 years of follow-up. After adjustment for age, regression analyses demonstrated a positive association of serum betaine with percentage of lean mass (LM%) of the entire body, trunk and limbs in men (all P<0·05) and LM% of the trunk in women (P=0·016). Each sd increase in serum betaine was associated with increases in LM% of 0·609 (whole body), 0·811 (trunk), 0·422 (limbs), 0·632 (arms) and 0·346 (legs) in men and 0·350 (trunk) in women. Multiple logistic regression analysis revealed that the prevalence of lower LM% decreased by 17 % (whole body) and 14 % (trunk) in women and 23 % (whole body), 28 % (trunk), 22 % (arms) and 26 % (percentage skeletal muscle index) in men with each sd increment in serum betaine. Elevated circulating betaine was associated with a higher LM% and lower prevalence of lower LM% in middle-aged and elderly Chinese adults, particularly men.

  1. Mass spectrometry-based sequencing and SRM-based quantitation of two novel vitellogenin isoforms in the leatherback sea turtle (Dermochelys coriacea).

    PubMed

    Plumel, Marine I; Wasselin, Thierry; Plot, Virginie; Strub, Jean-Marc; Van Dorsselaer, Alain; Carapito, Christine; Georges, Jean-Yves; Bertile, Fabrice

    2013-09-06

    No biomarker has yet been discovered to identify the reproductive status of the endangered leatherback sea turtle (Dermochelys coriacea). Although vitellogenin (VTG) could be used for this, its sequence is not known in D. coriacea and no quantitative assay has been carried out in this species to date. Using de novo sequencing-based proteomics, we unambiguously characterized sequences of two different VTG isoforms that we named Dc-VTG1 and Dc-VTG2. To our knowledge, this is the first clear evidence of different VTG isoforms and the structural characterization of derived yolk proteins in reptiles. This work illustrates how massive de novo sequencing can characterize novel sequences when working on "exotic" nonmodel species in which even nucleotide sequences are not available. We developed assays for absolute quantitation of these two isoforms using selected reaction monitoring (SRM) mass spectrometry, thus providing the first SRM assays developed specifically for a nonsequenced species. Plasma levels of Dc-VTG1 and Dc-VTG2 decreased as the nesting season proceeded, and were closely related to the increased levels of reproductive effort. The SRM assays developed here therefore provide an original and efficient approach for the reliable monitoring of reproduction cycles not only in D. coriacea, but potentially in other turtle species.

  2. Quantifying Differential Rotation Across the Main Sequence

    NASA Astrophysics Data System (ADS)

    Ule, Nicholas M.

    We have constructed a sample of eight stars from the Kepler field covering a broad range of spectral types, from F7 to K3. These stars have well defined rotation rates and show evidence of differential rotation in their lightcurves. In order to robustly determine differential rotation the inclination of a star must first be known. Thus, we have obtained moderate resolution spectra of these targets and obtained their radial velocities (v sin i), which is then used to determine inclinations. The photometric variations often seen in stars are created by star spots which we model in order to determine differential rotation. We have adapted the starspotz model developed by Croll (2006) with an asexual genetic algorithm to measure the strength of differential rotation (described with the parameter k). The photometric data was broken into 167 segments which were modeled for 6--8 values of k, with each model producing 50,000+ solutions. The value of k with a solution which produced the closest fit to the data was determined to be the most correct value of k for that lightcurve segment. With this data we also performed signal analysis which indicated the presence of long lived, latitudinally dependant active regions on stars. For our eight targets we successfully determined differential rotation rates and evaluated those values in relation to stellar temperature and rotational period. Coupled with previously published values for nine additional targets we find no temperature relation with differential rotation, but we do find a strong trend with rotation rates.

  3. The effect of starvation stress on Lactobacillus brevis L62 protein profile determined by de novo sequencing in positive and negative mass spectrometry ion mode.

    PubMed

    Butorac, Ana; Dodig, Ivana; Bačun-Družina, Višnja; Tishbee, Arye; Mrvčić, Jasna; Hock, Karlo; Diminić, Janko; Cindrić, Mario

    2013-05-15

    We describe a novel negative chemically activated fragmentation/positive chemically activated fragmentation (CAF-/CAF+) technique for protein identification. The technique was used to investigate Lactobacillus brevis adaptation to nutrient deprivation. The CAF-/CAF+ method enables de novo sequencing of derivate peptides with negative and positive ion mode matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry (MS/MS). Peptide sequences obtained from MS/MS spectra were matched against the National Center for Biotechnology Information (NCBI) non-redundant (nr) database and confirmed by the mass spectrometry data of elucidated peptide mass sequences derived from the annotated genome. This improved protein identification method highlighted 36 differentially expressed proteins in the proteome of L. brevis after 75 days of starvation. The results revealed the key differences in the metabolic pathways that are responsible for the survival of L. brevis in a hostile environment. Proteomics analysis demonstrated that numerous proteins engaged in glucose and amino-acid catabolizing pathways, glycerolipid metabolizing pathways, and stress-response mechanisms are differentially expressed after long-term starvation. Amino acid and proteomics analysis indicated that starved L. brevis metabolized arginine, glycine, and histidine from dead cells as alternative nutrient sources. The production of lactic acid also varied between the parent cells and the starved cells. Differentially expressed proteins identified exclusively by peptide sequence reading provided promising results for CAF-/CAF+ implementation in a standard proteomics workflow (e.g., biomarker and mutation discovery and biotyping). The practical performance of a reliable de novo sequencing technique in routine proteomics analysis is emphasized in this article. Copyright © 2013 John Wiley & Sons, Ltd.

  4. Protein-sequence polymorphisms and post-translational modifications in proteins from human saliva using top-down Fourier-transform ion cyclotron resonance mass spectrometry

    NASA Astrophysics Data System (ADS)

    Whitelegge, Julian P.; Zabrouskov, Vlad; Halgand, Frederic; Souda, Puneet; Bassilian, Sara; Yan, Weihong; Wolinsky, Larry; Loo, Joseph A.; Wong, David T. W.; Faull, Kym F.

    2007-12-01

    Single nucleotide polymorphisms (SNPs) can result in protein-sequence polymorphisms (PSPs) when codon translations are altered. Both top-down and bottom-up proteomics strategies can identify PSPs, but only if databases and software are used with this in mind. A 14,319 Da protein from human saliva was characterized using the top-down approach on a hybrid linear ion-trap Fourier-transform ion cyclotron resonance mass spectrometer equipped for both collisionally activated (CAD) and electron-capture (ECD) dissociation. Sequence tags identified the protein as Cystatin SN, and defined the N-terminal signal peptide cleavage site, as well as two disulfide bonds, in agreement with previous studies. The mass of the intact protein (<5 ppm error) deviated from that calculated from the published gene sequence by 16.031 Da, and, based on CAD and ECD fragment ion assignments, it was concluded that the isoform of the protein analyzed carried a PSP at residue 11 such that the Pro translated from the genome was in fact Leu/Ile. An independently determined SNP (rs2070856) subsequently confirmed the genetic basis of the mass spectral interpretation and defined the residue as Leu. In another example, the PRP3 protein with mass ~10,999 Da was found to be an isomeric/isobaric mixture of the reported sequence with PSPs D4N or D50N (rs1049112). Both CAD and ECD datasets support two phosphorylation sites at residues Ser8 and Ser22, rather than Ser17. In the context of discovery proteomics, previously undefined PSPs and PTMs will only be detected if the logic of data processing strategies considers their presence in an unbiased fashion.

  5. Identification of clinically relevant fungi and prototheca species by rRNA gene sequencing and multilocus PCR coupled with electrospray ionization mass spectrometry.

    PubMed

    Wang, Xuan; Fu, Yong-Feng; Wang, Rui-Ying; Li, Li; Cao, Ya-Hui; Chen, Yan-Qiong; Zhao, Hua-Zhen; Zhang, Qiang-Qiang; Wu, Ji-Qin; Weng, Xin-Hua; Cheng, Xun-Jia; Zhu, Li-Ping

    2014-01-01

    Multilocus PCR coupled with electrospray ionization mass spectrometry (PCR/ESI-MS) is a new strategy for pathogen identification, but information about its application in fungal identification remains sparse. One-hundred and twelve strains and isolates of clinically important fungi and Prototheca species were subjected to both rRNA gene sequencing and PCR/ESI-MS. Three regions of the rRNA gene were used as targets for sequencing: the 5' end of the large subunit rRNA gene (D1/D2 region), and the internal transcribed spacers 1 and 2 (ITS1 and ITS2 regions). Microbial identification (Micro ID), acquired by combining results of phenotypic methods and rRNA gene sequencing, was used to evaluate the results of PCR/ESI-MS. For identification of yeasts and filamentous fungi, combined sequencing of the three regions had the best performance (species-level identification rate of 93.8% and 81.8% respectively). The highest species-level identification rate was achieved by sequencing of D1/D2 for yeasts (92.2%) and ITS2 for filamentous fungi (75.8%). The two Prototheca species could be identified to species level by D1/D2 sequencing but not by ITS1 or ITS2. For the 102 strains and isolates within the coverage of PCR/ESI-MS identification, 87.3% (89/102) achieved species-level identification, 100% (89/89) of which were concordant to Micro ID on species/complex level. The species-level identification rates for yeasts and filamentous fungi were 93.9% (62/66) and 75% (27/36) respectively. rRNA gene sequencing provides accurate identification information, with the best results obtained by a combination of ITS1, ITS2 and D1/D2 sequencing. Our preliminary data indicated that PCR/ESI-MS method also provides a rapid and accurate identification for many clinical relevant fungi.

  6. De Novo Sequencing of Tryptic Phosphopeptides Using Matrix-Assisted Laser Desorption/Ionization Based Tandem Mass Spectrometry with Hydrogen Atom Attachment.

    PubMed

    Asakawa, Daiki; Takahashi, Hidenori; Iwamoto, Shinichi; Tanaka, Koichi

    2018-02-20

    Phosphorylation is the most abundant protein modification, and tandem mass spectrometry (MS/MS) with radical-based fragmentation techniques has proven to be a promising method for phosphoproteomic applications, owing to its ability to determine phosphorylation sites on proteins. The radical-induced fragmentation technique involves the attachment or abstraction of hydrogen to peptides in an ion trap mass spectrometer, in a process called hydrogen attachment/abstraction dissociation (HAD), which has only been recently developed. In the present investigation, we have analyzed model phosphopeptides and phosphoprotein digests using HAD-MS/MS, combined with matrix-assisted laser desorption/ionization (MALDI), in order to demonstrate the usefulness of the HAD-MS/MS-based analytical method. The tryptic peptides were categorized as arginine- and lysine-terminated peptides, and MALDI HAD-MS/MS is found to facilitate the sequencing of arginine-terminated tryptic peptides, because of the selective observation of C-terminal side fragment ions. In contrast, MALDI HAD-MS/MS of lysine-terminated tryptic peptides produced both N- and C-terminal side fragments, such that the mass spectra were complex. The guanidination of peptide converted lysine into homoarginine, which facilitated the interpretation of MALDI HAD-MS/MS mass spectra. The present method was useful for de novo sequencing of tryptic phosphopeptides.

  7. MALDI-TOF Mass Spectrometry for Multilocus Sequence Typing of Escherichia coli Reveals Diversity among Isolates Carrying blaCMY₋₂-Like Genes.

    PubMed

    Tagg, Kaitlin A; Ginn, Andrew N; Partridge, Sally R; Iredell, Jonathan R

    2015-01-01

    Effective surveillance and management of pathogenic Escherichia coli relies on robust and reproducible typing methods such as multilocus sequence typing (MLST). Typing of E. coli by MLST enables tracking of pathogenic clones that are known to carry virulence factors or spread resistance, such as the globally-prevalent ST131 lineage. Standard MLST for E. coli requires sequencing of seven alleles, or a whole genome, and can take several days. Here, we have developed and validated a nucleic-acid-based MALDI-TOF mass spectrometry (MS) method for MLST as a rapid alternative to sequencing that requires minimal operator expertise. Identification of alleles was 99.6% concordant with sequencing. We employed MLST by MALDI-TOF MS to investigate diversity among 62 E. coli isolates from Sydney, Australia, carrying a blaCMY-2-like gene on an IncI1 plasmid to determine whether any dominant clonal lineages are associated with the spread of this globally-disseminated resistance gene. Thirty-four known sequence types were identified, including lineages associated with human disease, animal and environmental sources. This suggests that the dissemination of blaCMY-2-like-genes is more complex than the simple spread of successful pathogenic clones. E. coli MLST by MALDI-TOF MS, employed here for the first time, can be utilised as an automated tool for large-scale population analyses or for targeted screening for known high-risk clones in a diagnostic setting.

  8. Seasonal variations in the profile of main phospholipids in Mytilus galloprovincialis mussels: A study by hydrophilic interaction liquid chromatography-electrospray ionization Fourier transform mass spectrometry.

    PubMed

    Facchini, Laura; Losito, Ilario; Cataldi, Tommaso R I; Palmisano, Francesco

    2018-01-01

    A systematic characterization of phosphatidylcholines and phosphatidylethanolamines in mussels of sp Mytilus galloprovincialis was performed by high-efficiency hydrophilic interaction liquid chromatography combined with electrospray ionization and Fourier transform mass spectrometry (FTMS), based on a quadrupole-Orbitrap hybrid spectrometer. The FTMS/MS experiments under high collisional energy dissociation conditions, complemented by low-energy collisionally induced dissociation MS n (n = 2,3) experiments, performed in a linear ion trap mass spectrometer, were exploited for structural elucidation purposes. The described approach led to an unprecedented characterization of the mussel phospholipidome, with 185 phosphatidylcholines and 131 phosphatidylethanolamines species recognized, distributed among diacylic, plasmanylic, and plasmenylic forms. This was the starting point for the evaluation of the effects of season (in particular, of sea temperature) on the profile of those phospholipids. To this aim, a set of mussel samples retrieved from commercial sources in different periods of the year was considered. Principal component analysis revealed a clear separation between samples collected in periods characterized by cold, intermediate, or warm sea temperatures, respectively. In particular, an enrichment in phospholipids containing unsaturated side chains was observed in mussels collected from cold seawaters (winter-early spring), thus confirming the general model previously elaborated to explain the adaptation of marine invertebrates, including some bivalve molluscs, to low temperatures. On the other hand, relevant levels of plasma(e)nylic and acylic phospholipids bearing either saturated or non-methylene-interrupted side chains were found in mussels collected in warm seawaters (typical of summer and early autumn, at Italian latitudes). This finding opened interesting perspectives towards the development of strategies able to prevent global warming-related mussel

  9. A comparison between conventional and AMS [sup 14]C dates on basal salt marsh peats from coastal Maine. [Accelerator Mass Spectroscopy

    SciTech Connect

    Gehrels, R.W.; Belknap, D.F.

    1992-01-01

    This study reports AMS dates from four Maine salt marshes: Webbannet Marsh (Wells), Morse and Sprague River marshes (Phippsburg), and Sanborn Cove marsh (Machiasport). The AMS dates are compared with conventional dates on bulk samples obtained from either the same cores or from other cores at comparable depths. Four AMS dates from the Webhannet and Sanborn Cove marshes were considerably older than their conventional counterparts, by as much as 1,000 years. Three causes for this age discrepancy are suggested. First, under slow rates of marsh accretion, peats remain within the root zone of modern plants for a relatively long period,more » causing a continued input of younger carbon. Intruded roots are undetectable in the highly macerated, 4,000--5,000 C-14 year old peats. Another source of contamination is the percolation of mobile humic acids along the impermeable Pleistocene substrate. Finally, a date on a bulk peat of 10 cm vertical extent represents an average age for a portion of peat that spans a time interval possibly of several centuries. The age difference between the bulk date and the AMS date from the base of the peat increases with decreasing rates of marsh accretion. The forested steep slopes of the upland surrounding the marsh seem a likely source of old carbon that can easily be washed onto the marsh surface. The slow rate of late-Holocene sea-level rise in Maine, as well as the geologic and hydrologic setting of the salt marshes, make conventional C-14 dating of salt marsh peats in Maine a problematic affair. This study implies that AMS dates may be needed to verify Holocene sea-level curves from other coastal areas that have hitherto been based solely on conventional C-14 peat dates.« less

  10. Identification and verification of hybridoma-derived monoclonal antibody variable region sequences using recombinant DNA technology and mass spectrometry

    USDA-ARS?s Scientific Manuscript database

    Antibody engineering requires the identification of antigen binding domains or variable regions (VR) unique to each antibody. It is the VR that define the unique antigen binding properties and proper sequence identification is essential for functional evaluation and performance of recombinant antibo...

  11. Differentiation of species of the Streptococcus bovis/equinus-complex by MALDI-TOF Mass Spectrometry in comparison to sodA sequence analyses.

    PubMed

    Hinse, D; Vollmer, T; Erhard, M; Welker, M; Moore, E R B; Kleesiek, K; Dreier, J

    2011-02-01

    The Streptococcus bovis/equinus complex is a heterogeneous group within the group D streptococci with important clinical relevance regarding infective endocarditis, sepsis and colon carcinoma. The taxonomic identification of species and sub-species of this complex, by the standard methods remains difficult. In the present study, we compared the cluster analysis of 88 strains of species of the S. bovis/equinus complex by sequence analysis of the manganese-dependent superoxide dismutase gene (sodA) and by Matrix Assisted Laser Desorption/Ionization-Time Of Flight Mass Spectrometry (MALDI-TOF MS). We observed a high congruence of strain grouping by MALDI-TOF MS in comparison with sodA sequence analyses, demonstrating the accuracy and reliability of MALDI-TOF MS in comparison to DNA sequence-based method. By generating mass spectra for each species and sub-species, we were able to discriminate all members of the S. bovis/equinus complex. Furthermore, we demonstrated reliable identifications to the species level by MALDI-TOF MS, independently of cultivation conditions. Copyright © 2010 Elsevier GmbH. All rights reserved.

  12. Metabolism studies of the Kratom alkaloid speciociliatine, a diastereomer of the main alkaloid mitragynine, in rat and human urine using liquid chromatography-linear ion trap mass spectrometry.

    PubMed

    Philipp, Anika A; Wissenbach, Dirk K; Weber, Armin A; Zapp, Josef; Maurer, Hans H

    2011-03-01

    Mitragyna speciosa (Kratom) is currently used as a drug of abuse. When monitoring its abuse in urine, several alkaloids and their metabolites must be considered. In former studies, mitragynine (MG), its diastereomer speciogynine (SG), and paynantheine and their metabolites could be identified in rat and human urine using LC-MS(n). In Kratom users' urines, besides MG and SG, further isomeric compounds were detected. To elucidate whether the MG and SG diastereomer speciociliatine (SC) and its metabolites represent further compounds, the phase I and II metabolites of SC were identified first in rat urine after the administration of the pure alkaloid. Then, the identified rat metabolites were screened for in the urine of Kratom users using the above-mentioned LC-MS(n) procedure. Considering the mass spectra and retention times, it could be confirmed that SC and its metabolites are so far the unidentified isomers in human urine. In conclusion, SC and its metabolites can be used as further markers for Kratom use, especially by consumption of raw material or products that contain a high amount of fruits of the Malaysian plant M. speciosa.

  13. Studies on the metabolism of mitragynine, the main alkaloid of the herbal drug Kratom, in rat and human urine using liquid chromatography-linear ion trap mass spectrometry.

    PubMed

    Philipp, Anika A; Wissenbach, Dirk K; Zoerntlein, Siegfried W; Klein, Oliver N; Kanogsunthornrat, Jidapha; Maurer, Hans H

    2009-08-01

    Mitragynine (MG) is an indole alkaloid of the Thai medicinal plant Mitragyna speciosa (Kratom in Thai) and reported to have opioid agonistic properties. Because of its stimulant and euphoric effects, Kratom is used as a herbal drug of abuse. The aim of the presented study is to identify the phase I and II metabolites of MG in rat and human urine after solid-phase extraction (SPE) using liquid chromatography-linear ion trap mass spectrometry providing detailed structure information in the MSn mode particularly with high resolution. The seven identified phase I metabolites indicated that MG was metabolized by hydrolysis of the methylester in position 16, O-demethylation of the 9-methoxy group and of the 17-methoxy group, followed, via the intermediate aldehydes, by oxidation to carboxylic acids or reduction to alcohols and combinations of some steps. In rats, four metabolites were additionally conjugated to glucuronides and one to sulfate, but in humans, three metabolites to glucuronides and three to sulfates. Copyright 2009 John Wiley & Sons, Ltd.

  14. Negative Ion In-Source Decay Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for Sequencing Acidic Peptides.

    PubMed

    McMillen, Chelsea L; Wright, Patience M; Cassady, Carolyn J

    2016-05-01

    Matrix-assisted laser desorption/ionization (MALDI) in-source decay was studied in the negative ion mode on deprotonated peptides to determine its usefulness for obtaining extensive sequence information for acidic peptides. Eight biological acidic peptides, ranging in size from 11 to 33 residues, were studied by negative ion mode ISD (nISD). The matrices 2,5-dihydroxybenzoic acid, 2-aminobenzoic acid, 2-aminobenzamide, 1,5-diaminonaphthalene, 5-amino-1-naphthol, 3-aminoquinoline, and 9-aminoacridine were used with each peptide. Optimal fragmentation was produced with 1,5-diaminonphthalene (DAN), and extensive sequence informative fragmentation was observed for every peptide except hirudin(54-65). Cleavage at the N-Cα bond of the peptide backbone, producing c' and z' ions, was dominant for all peptides. Cleavage of the N-Cα bond N-terminal to proline residues was not observed. The formation of c and z ions is also found in electron transfer dissociation (ETD), electron capture dissociation (ECD), and positive ion mode ISD, which are considered to be radical-driven techniques. Oxidized insulin chain A, which has four highly acidic oxidized cysteine residues, had less extensive fragmentation. This peptide also exhibited the only charged localized fragmentation, with more pronounced product ion formation adjacent to the highly acidic residues. In addition, spectra were obtained by positive ion mode ISD for each protonated peptide; more sequence informative fragmentation was observed via nISD for all peptides. Three of the peptides studied had no product ion formation in ISD, but extensive sequence informative fragmentation was found in their nISD spectra. The results of this study indicate that nISD can be used to readily obtain sequence information for acidic peptides.

  15. Evaluation of tramadol and its main metabolites in horse plasma by high-performance liquid chromatography/fluorescence and liquid chromatography/electrospray ionization tandem mass spectrometry techniques.

    PubMed

    De Leo, Marinella; Giorgi, Mario; Saccomanni, Giuseppe; Manera, Clementina; Braca, Alessandra

    2009-01-01

    Tramadol is a centrally acting analgesic drug that has been used clinically for the last two decades to treat pain in humans. The clinical response of tramadol is strictly correlated to its metabolism, because of the different analgesic activity of its metabolites. O-Desmethyltramadol (M1), its major active metabolite, is 200 times more potent at the micro-receptor than the parent drug. In recent years tramadol has been widely introduced in veterinary medicine but its use has been questioned in some species. The aim of the present study was to develop a new sensible method to detect the whole metabolic profile of the drug in horses, through plasma analyses by high-performance liquid chromatography (HPLC) coupled with fluorimetric (FL) and photodiode array electrospray ionization mass spectrometric (PDA-ESI-MS) detection, after its sustained release by oral administration (5 mg/kg). In HPLC/FL experiments the comparison of the horse plasma chromatogram profile with that of a standard mixture suggested the identification of the major peaks as tramadol and its metabolites M1 and N,O-desmethyltramadol (M5). LC/PDA-ESI-MS/MS analysis confirmed the results obtained by HPLC/FL and also provided the identification of two more metabolites, N-desmethyltramadol (M2), and N,N-didesmethyltramadol (M3). Another metabolite, M6, was also detected and identified. The present findings demonstrate the usefulness and the advantage of LC/ESI-MS/MS techniques in a search for tramadol metabolites in horse plasma samples. Copyright (c) 2008 John Wiley & Sons, Ltd.

  16. Identification of the main by-products of the developing agent N-hydroxyethyl-N-ethyl-3-methyl-p-phenylenediamine in photographic effluents by liquid chromatography/mass spectrometry.

    PubMed

    Lunar, Loreto; Rubio, Soledad; Pérez-Bendito, Dolores; Jiménez, César

    2002-01-01

    N-Hydroxyethyl-N-ethyl-3-methyl-p-phenylenediamine (CD(4)) is commonly used as a developing agent in color photographic processes. The main by-products formed in developer baths used in the process were separated and identified by liquid chromatography/electron ionization mass spectrometry (LC/EI-MS) and liquid chromatography/atmospheric pressure ionization mass spectrometry (LC/API-MS). A number of side reactions, in addition to the main reactions involved in the developing process, were found to occur. Such side reactions involved in the formation of CD(4) by-products included oxidation, hydroxylation, sulfonation and the formation of coupling products. A reaction pathway for the degradation of CD(4) based on the nature of the by-products identified is proposed and discussed. Copyright 2002 John Wiley & Sons, Ltd.

  17. High quality draft genome sequence of Brachymonas chironomi AIMA4T (DSM 19884T) isolated from a Chironomus sp. egg mass

    DOE PAGES

    Laviad, Sivan; Lapidus, Alla; Han, James; ...

    2015-05-27

    Brachymonas chironomi strain AIMA4T (Halpern et al., 2009) is a Gram-negative, non-motile, aerobic, chemoorganotroph bacterium. B. chironomi is a member of the Comamonadaceae, a family within the class Betaproteobacteria. This species was isolated from a chironomid (Diptera; Chironomidae) egg mass, sampled from a waste stabilization pond in northern Israel. Phylogenetic analysis based on the 16S rRNA gene sequences placed strain AIMA4T in the genus Brachymonas. Here we describe the features of this organism, together with the complete genome sequence and annotation. We find the DNA GC content is 63.5%. The chromosome length is 2,509,395 bp. It encodes 2,382 proteins andmore » 68 RNA genes. Brachymonas chironomi genome is part of the Genomic Encyclopedia of Type Strains, Phase I: the one thousand microbial genomes (KMG) project.« less

  18. An integrated native mass spectrometry and top-down proteomics method that connects sequence to structure and function of macromolecular complexes

    NASA Astrophysics Data System (ADS)

    Li, Huilin; Nguyen, Hong Hanh; Ogorzalek Loo, Rachel R.; Campuzano, Iain D. G.; Loo, Joseph A.

    2018-02-01

    Mass spectrometry (MS) has become a crucial technique for the analysis of protein complexes. Native MS has traditionally examined protein subunit arrangements, while proteomics MS has focused on sequence identification. These two techniques are usually performed separately without taking advantage of the synergies between them. Here we describe the development of an integrated native MS and top-down proteomics method using Fourier-transform ion cyclotron resonance (FTICR) to analyse macromolecular protein complexes in a single experiment. We address previous concerns of employing FTICR MS to measure large macromolecular complexes by demonstrating the detection of complexes up to 1.8 MDa, and we demonstrate the efficacy of this technique for direct acquirement of sequence to higher-order structural information with several large complexes. We then summarize the unique functionalities of different activation/dissociation techniques. The platform expands the ability of MS to integrate proteomics and structural biology to provide insights into protein structure, function and regulation.

  19. Use of Ultraviolet Photodissociation Coupled with Ion Mobility Mass Spectrometry To Determine Structure and Sequence from Drift Time Selected Peptides and Proteins.

    PubMed

    Theisen, Alina; Yan, Bin; Brown, Jeffery M; Morris, Michael; Bellina, Bruno; Barran, Perdita E

    2016-10-03

    We demonstrate the capabilities of a laser-coupled ion mobility mass spectrometer for analysis of peptide sequence and structure showing ultraviolet photodissociation (UVPD) spectra of mass and mobility selected ions. A Synapt G2-S mass spectrometer has been modified to allow photointeraction of ions post the mobility cell. For this work, we have employed a single wavelength laser, which irradiates at 266 nm. We present the unique capabilities of this instrument and demonstrate several key features. Irradiation of luteinizing hormone releasing hormone (LHRH), growth hormone releasing hexapeptide (GHRP-6), and TrpCage (sequence NLYIQWLKDGGPSSGRPPPS) yields extensive b- and y-type fragmentation as well as a- and c-type ions. In addition, we observe side chain losses, including the indole group from tryptophan, and immonium ions. For negatively charged ions, we show the advantage of using collision-induced dissociation (CID) post-UVPD: radical ions are produced following irradiation, and these fragment with higher efficiency. Further, we have incorporated ion mobility and subsequent drift time gating into the UVPD method allowing the separate analysis of m/z-coincident species, both conformers and multimers. To demonstrate, we selectively dissociate the singly charged dimer or doubly charged monomer of the peptide gramicidin A and conformers of the [M + 5H] 5+ form of the peptide melittin. Each mobility selected form has a different "fingerprint" dissociation spectrum, both predominantly containing b and y fragments. Differences in the intensities of various loss channels between the two species were revealed. The smaller conformer of melittin has fewer cleavage sites along the peptide backbone than the larger conformer suggesting considerable structural differences. For gramicidin, a single laser shot UVPD discriminates between primary photodissociation and subsequent fragmentation of fragments. We also show how this modified instrument facilitates activated electron

  20. Accurate Identification of Common Pathogenic Nocardia Species: Evaluation of a Multilocus Sequence Analysis Platform and Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

    PubMed Central

    Chen, Sharon C-A.; Fan, Xin; Zhang, Li; Li, Hai-Xia; Hou, Xin; Cheng, Jing-Wei; Kong, Fanrong; Zhao, Yu-Pei; Xu, Ying-Chun

    2016-01-01

    Species identification of Nocardia is not straightforward due to rapidly evolving taxonomy, insufficient discriminatory power of conventional phenotypic methods and also of single gene locus analysis including 16S rRNA gene sequencing. Here we evaluated the ability of a 5-locus (16S rRNA, gyrB, secA1, hsp65 and rpoB) multilocus sequence analysis (MLSA) approach as well as that of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in comparison with sequencing of the 5’-end 606 bp partial 16S rRNA gene to provide identification of 25 clinical isolates of Nocardia. The 5’-end 606 bp 16S rRNA gene sequencing successfully assigned 24 of 25 (96%) clinical isolates to species level, namely Nocardia cyriacigeorgica (n = 12, 48%), N. farcinica (n = 9, 36%), N. abscessus (n = 2, 8%) and N. otitidiscaviarum (n = 1, 4%). MLSA showed concordance with 16S rRNA gene sequencing results for the same 24 isolates. However, MLSA was able to identify the remaining isolate as N. wallacei, and clustered N. cyriacigeorgica into three subgroups. None of the clinical isolates were correctly identified to the species level by MALDI-TOF MS analysis using the manufacturer-provided database. A small “in-house” spectral database was established incorporating spectra of five clinical isolates representing the five species identified in this study. After complementation with the “in-house” database, of the remaining 20 isolates, 19 (95%) were correctly identified to species level (score ≥ 2.00) and one (an N. abscessus strain) to genus level (score ≥ 1.70 and < 2.00). In summary, MLSA showed superior discriminatory power compared with the 5’-end 606 bp partial 16S rRNA gene sequencing for species identification of Nocardia. MALDI-TOF MS can provide rapid and accurate identification but is reliant on a robust mass spectra database. PMID:26808813

  1. The H-Index of `An Approach to Correlate Tandem Mass Spectral Data of Peptides with Amino Acid Sequences in a Protein Database'

    NASA Astrophysics Data System (ADS)

    Washburn, Michael P.

    2015-11-01

    Over 20 years ago a remarkable paper was published in the Journal of American Society for Mass Spectrometry. This paper from Jimmy Eng, Ashley McCormack, and John Yates described the use of protein databases to drive the interpretation of tandem mass spectra of peptides. This paper now has over 3660 citations and continues to average more than 260 per year over the last decade. This is an amazing scientific achievement. The reason for this is the paper was a cutting edge development at the moment in time when genomes of organisms were being sequenced, protein and peptide mass spectrometry was growing into the field of proteomics, and the power of computing was growing quickly in accordance with Moore's law. This work by the Yates lab grew in importance as genomics, proteomics, and computation all advanced and eventually resulted in the widely used SEQUEST algorithm and platform for the analysis of tandem mass spectrometry data. This commentary provides an analysis of the impact of this paper by analyzing the citations it has generated and the impact of these citing papers.

  2. TEMPO-Assisted Free Radical-Initiated Peptide Sequencing Mass Spectrometry (FRIPS MS) in Q-TOF and Orbitrap Mass Spectrometers: Single-Step Peptide Backbone Dissociations in Positive Ion Mode

    NASA Astrophysics Data System (ADS)

    Jang, Inae; Lee, Sun Young; Hwangbo, Song; Kang, Dukjin; Lee, Hookeun; Kim, Hugh I.; Moon, Bongjin; Oh, Han Bin

    2017-01-01

    The present study demonstrates that one-step peptide backbone fragmentations can be achieved using the TEMPO [2-(2,2,6,6-tetramethyl piperidine-1-oxyl)]-assisted free radical-initiated peptide sequencing (FRIPS) mass spectrometry in a hybrid quadrupole time-of-flight (Q-TOF) mass spectrometer and a Q-Exactive Orbitrap instrument in positive ion mode, in contrast to two-step peptide fragmentation in an ion-trap mass spectrometer (reference Anal. Chem. 85, 7044-7051 (30)). In the hybrid Q-TOF and Q-Exactive instruments, higher collisional energies can be applied to the target peptides, compared with the low collisional energies applied by the ion-trap instrument. The higher energy deposition and the additional multiple collisions in the collision cell in both instruments appear to result in one-step peptide backbone dissociations in positive ion mode. This new finding clearly demonstrates that the TEMPO-assisted FRIPS approach is a very useful tool in peptide mass spectrometry research.

  3. TEMPO-Assisted Free Radical-Initiated Peptide Sequencing Mass Spectrometry (FRIPS MS) in Q-TOF and Orbitrap Mass Spectrometers: Single-Step Peptide Backbone Dissociations in Positive Ion Mode.

    PubMed

    Jang, Inae; Lee, Sun Young; Hwangbo, Song; Kang, Dukjin; Lee, Hookeun; Kim, Hugh I; Moon, Bongjin; Oh, Han Bin

    2017-01-01

    The present study demonstrates that one-step peptide backbone fragmentations can be achieved using the TEMPO [2-(2,2,6,6-tetramethyl piperidine-1-oxyl)]-assisted free radical-initiated peptide sequencing (FRIPS) mass spectrometry in a hybrid quadrupole time-of-flight (Q-TOF) mass spectrometer and a Q-Exactive Orbitrap instrument in positive ion mode, in contrast to two-step peptide fragmentation in an ion-trap mass spectrometer (reference Anal. Chem. 85, 7044-7051 (30)). In the hybrid Q-TOF and Q-Exactive instruments, higher collisional energies can be applied to the target peptides, compared with the low collisional energies applied by the ion-trap instrument. The higher energy deposition and the additional multiple collisions in the collision cell in both instruments appear to result in one-step peptide backbone dissociations in positive ion mode. This new finding clearly demonstrates that the TEMPO-assisted FRIPS approach is a very useful tool in peptide mass spectrometry research. Graphical Abstract ᅟ.

  4. Extensive de novo sequencing of new parvalbumin isoforms using a novel combination of bottom-up proteomics, accurate molecular mass measurement by FTICR-MS, and selected MS/MS ion monitoring.

    PubMed

    Carrera, Mónica; Cañas, Benito; Vázquez, Jesús; Gallardo, José M

    2010-09-03

    Parvalbumins (PRVB) (11.20-11.55 kDa) are considered the major fish allergens. In this work, we propose a novel strategy for extensive characterization of this group of proteins based on the integration of a classical Bottom-Up proteomics approach with accurate Mr determination by FTICR-MS of intact proteins and selected MS/MS ion monitoring (SMIM) of peptide mass gaps. For each PRVB, mass spectra obtained by LC-ESI-IT-MS/MS from two digests (trypsin, Glu-C) were de novo sequenced manually with help of two programs (PEAKS, DeNovoX). The deduced peptide sequences were arranged and the theoretical Mr for the resulting sequences was calculated. Experimental Mr for each PRVB was measured with high mass accuracy by FTICR-MS (0.05-4.47 ppm). The masses of several missing peptide gaps were estimated by comparing the theoretical and experimental Mr, and the MS/MS spectra corresponding to these ions were obtained by LC-ESI-IT-MS/MS in the SMIM scanning mode. Finally, all peptide sequences were combined to generate the final protein sequences. This approach allowed the complete de novo MS-sequencing of 25 new PRVB isoforms. These new sequences belong to 11 different species from the Merlucciidae family, organisms for which genomes remain unsequenced. This study constitutes the report accounting for the higher number of new proteins completely sequenced making use of MS-based techniques only.

  5. Whole-Genome Sequencing and iPLEX MassARRAY Genotyping Map an EMS-Induced Mutation Affecting Cell Competition in Drosophila melanogaster.

    PubMed

    Lee, Chang-Hyun; Rimesso, Gerard; Reynolds, David M; Cai, Jinlu; Baker, Nicholas E

    2016-10-13

    Cell competition, the conditional loss of viable genotypes only when surrounded by other cells, is a phenomenon observed in certain genetic mosaic conditions. We conducted a chemical mutagenesis and screen to recover new mutations that affect cell competition between wild-type and RpS3 heterozygous cells. Mutations were identified by whole-genome sequencing, making use of software tools that greatly facilitate the distinction between newly induced mutations and other sources of apparent sequence polymorphism, thereby reducing false-positive and false-negative identification rates. In addition, we utilized iPLEX MassARRAY for genotyping recombinant chromosomes. These approaches permitted the mapping of a new mutation affecting cell competition when only a single allele existed, with a phenotype assessed only in genetic mosaics, without the benefit of complementation with existing mutations, deletions, or duplications. These techniques expand the utility of chemical mutagenesis and whole-genome sequencing for mutant identification. We discuss mutations in the Atm and Xrp1 genes identified in this screen. Copyright © 2016 Lee et al.

  6. CSI 2264: Simultaneous optical and X-ray variability in pre-main sequence stars. I. Time resolved X-ray spectral analysis during optical dips and accretion bursts in stars with disks

    NASA Astrophysics Data System (ADS)

    Guarcello, M. G.; Flaccomio, E.; Micela, G.; Argiroffi, C.; Sciortino, S.; Venuti, L.; Stauffer, J.; Rebull, L.; Cody, A. M.

    2017-06-01

    Context. Pre-main sequence stars are variable sources. The main mechanisms responsible for their variability are variable extinction, unsteady accretion, and rotational modulation of both hot and dark photospheric spots and X-ray-active regions. In stars with disks, this variability is related to the morphology of the inner circumstellar region (≤0.1 AU) and that of the photosphere and corona, all impossible to be spatially resolved with present-day techniques. This has been the main motivation for the Coordinated Synoptic Investigation of NGC 2264, a set of simultaneous observations of NGC 2264 with 15 different telescopes. Aims: In this paper, we focus on the stars with disks. We analyze the X-ray spectral properties extracted during optical bursts and dips in order to unveil the nature of these phenomena. Stars without disks are studied in a companion paper. Methods: We analyze simultaneous CoRoT and Chandra/ACIS-I observations to search for coherent optical and X-ray flux variability in stars with disks. Then, star