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Sample records for dwarf companion twa

  1. Finding orbital motion of sub-stellar companions - the case of TWA 5B

    NASA Astrophysics Data System (ADS)

    Schmidt, T.; Neuhäuser, R.; Mugrauer, M.

    2008-07-01

    TWA 5B is a brown dwarf companion of H=12 mag, 2″ off the ~5 mag brighter triple star CoD-33° 7795 (=TWA 5), a member of the TW Hydrae association of T Tauri stars at ~55 pc. This object is the first brown dwarf around a pre-main-sequence star (confirmed by common proper motion) ever found. In the last year we have newly reduced VLT NaCo data originally taken in 2003 and combined it with all the available astrometric data of the system to investigate possibly detectable orbital motion of the system. Indeed we were able to find linear orbital motion of the system combining data from HST, VLT and Gemini-North.

  2. The Coolest Isolated Brown Dwarf Candidate Member of TWA

    NASA Astrophysics Data System (ADS)

    Gagné, Jonathan; Faherty, Jacqueline K.; Cruz, Kelle; Lafrenière, David; Doyon, René; Malo, Lison; Artigau, Étienne

    2014-04-01

    We present two new late-type brown dwarf candidate members of the TW Hydrae association (TWA): 2MASS J12074836-3900043 and 2MASS J12474428-3816464, which were found as part of the BANYAN all-sky survey (BASS) for brown dwarf members of nearby young associations. We obtained near-infrared (NIR) spectroscopy for both objects (NIR spectral types are respectively L1 and M9), as well as optical spectroscopy for J1207-3900 (optical spectral type is L0γ), and show that both display clear signs of low gravity, and thus youth. We use the BANYAN II Bayesian inference tool to show that both objects are candidate members to TWA with a very low probability of being field contaminants, although the kinematics of J1247-3816 seem slightly at odds with that of other TWA members. J1207-3900 is currently the latest-type and the only isolated L-type candidate member of TWA. Measuring the distance and radial velocity of both objects is still required to claim them as bona fide members. Such late-type objects are predicted to have masses down to 11-15 M Jup at the age of TWA, which makes them compelling targets to study atmospheric properties in a regime similar to that of currently known imaged extrasolar planets.

  3. THE COOLEST ISOLATED BROWN DWARF CANDIDATE MEMBER OF TWA

    SciTech Connect

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Malo, Lison; Artigau, Étienne; Faherty, Jacqueline K.; Cruz, Kelle E-mail: jfaherty17@gmail.com

    2014-04-10

    We present two new late-type brown dwarf candidate members of the TW Hydrae association (TWA): 2MASS J12074836-3900043 and 2MASS J12474428-3816464, which were found as part of the BANYAN all-sky survey (BASS) for brown dwarf members of nearby young associations. We obtained near-infrared (NIR) spectroscopy for both objects (NIR spectral types are respectively L1 and M9), as well as optical spectroscopy for J1207-3900 (optical spectral type is L0γ), and show that both display clear signs of low gravity, and thus youth. We use the BANYAN II Bayesian inference tool to show that both objects are candidate members to TWA with a very low probability of being field contaminants, although the kinematics of J1247-3816 seem slightly at odds with that of other TWA members. J1207-3900 is currently the latest-type and the only isolated L-type candidate member of TWA. Measuring the distance and radial velocity of both objects is still required to claim them as bona fide members. Such late-type objects are predicted to have masses down to 11-15 M {sub Jup} at the age of TWA, which makes them compelling targets to study atmospheric properties in a regime similar to that of currently known imaged extrasolar planets.

  4. A Candidate Substellar Companion to CoD -33(deg) 7795 (TWA 5)

    NASA Astrophysics Data System (ADS)

    Lowrance, P. J.; McCarthy, C. M.; Becklin, E. E.; Zuckerman, B.; Schneider, G.; Webb, R. A.; Hines, D. C.; Low, F. J.; Rieke, M. J.; Thompson, R. I.; Smith, B. A.; Meier, R.; Terrile, R. J.; Kirkpatrick, J. D.; Koerner, D. W.

    1998-12-01

    We present the discovery of a candidate substellar object as part of the NICMOS Instrument Design Team's survey of young stars in the solar vicinity using the sensitivity and spatial resolution afforded by the NICMOS coronagraph on the Hubble Space Telescope. The H=12.1 mag object was discovered approximately 2'' from the TW Hydrae Association member CoD -33(deg) 7795 (TWA 5), and the infrared photometry implies a spectral type M8-M8.5, with a temperature of ~ 2650K. We estimate that the probability of a chance alignment with a background object of this nature is < 2 x 10(-5) , and therefore postulate the object (TWA 5B) is physically associated at a projected separation of 100 AU. Given the youth of the primary ( ~ 10 Myr), current brown dwarf cooling models predict a mass of approximately 20 Jupiter masses for the companion. This work is supported in part by NASA grant NAG 5-3042 to the University of Arizona NICMOS Instrument Design Team. This poster is based on observations obtained 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.

  5. MICROLENSING BINARIES WITH CANDIDATE BROWN DWARF COMPANIONS

    SciTech Connect

    Shin, I.-G.; Han, C.; Gould, A.; Skowron, J.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Soszynski, I.; Pietrzynski, G.; Poleski, R.; Ulaczyk, K.; Pietrukowicz, P.; Kozlowski, S.; Wyrzykowski, L.; Sumi, T.; Dominik, M.; Beaulieu, J.-P.; Tsapras, Y.; Bozza, V.; Abe, F.; Collaboration: OGLE Collaboration; MOA Collaboration; muFUN Collaboration; and others

    2012-12-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during the 2004-2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found seven candidate events: OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured masses of the brown dwarf companions are 0.02 {+-} 0.01 M {sub Sun} and 0.019 {+-} 0.002 M {sub Sun} for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low-mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events with well-covered light curves increases with new-generation searches.

  6. FIRST DIRECT EVIDENCE THAT BARIUM DWARFS HAVE WHITE DWARF COMPANIONS

    SciTech Connect

    Gray, R. O.; McGahee, C. E.; Griffin, R. E. M.; Corbally, C. J. E-mail: cmcgahe@g.clemson.edu E-mail: corbally@as.arizona.edu

    2011-05-15

    Barium II (Ba) stars are chemically peculiar F-, G-, and K-type objects that show enhanced abundances of s-process elements. Since s-process nucleosynthesis is unlikely to take place in stars prior to the advanced asymptotic giant branch (AGB) stage, the prevailing hypothesis is that each present Ba star was contaminated by an AGB companion which is now a white dwarf (WD). Unless the initial mass ratio of such a binary was fairly close to unity, the receiving star is thus at least as likely to be a dwarf as a giant. So although most known Ba stars appear to be giants, the hypothesis requires that Ba dwarfs be comparably plentiful and moreover that they should all have WD companions. However, despite dedicated searches with the IUE satellite, no WD companions have been directly detected to date among the classical Ba dwarfs, even though some 90% of those stars are spectroscopic binaries, so the contamination hypothesis is therefore presently in some jeopardy. In this paper, we analyze recent deep, near-UV and far-UV Galaxy Evolution Explorer (GALEX) exposures of four of the brightest of the class (HD 2454, 15360, 26367, and 221531), together with archived GALEX data for two newly recognized Ba dwarfs: HD 34654 and HD 114520 (which also prove to be spectroscopic binaries). The GALEX observations of the Ba dwarfs as a group show a significant far-UV excess compared to a control sample of normal F-type dwarfs. We suggest that this ensemble far-UV excess constitutes the first direct evidence that Ba dwarfs have WD companions.

  7. Clandestine Companions of Nearby Red Dwarfs

    NASA Astrophysics Data System (ADS)

    Henry, Todd J.; Koerner, D. W.; Jao, W. C.; Subasavage, J. P.; Ianna, P. A.; RECONS

    2006-12-01

    During the RECONS parallax program at the CTIO 0.9m, we have accumulated more than six years of astrometric data on red dwarfs in the southern sky. Eighty red dwarfs within 10 pc, including more than two dozen new discoveries by our team, are being followed to reveal the telltale perturbations caused by unseen companions. The advent of modern CCD technology yields substantial improvement in the detection of low mass companions over the classic studies done using photographic plates. The current ASPENS (Astrometric Search for Planets Encircling Nearby Stars) program is capable of finding hidden companions with masses as low as 10 Jupiters. Here we report the first results of the ASPENS effort, including a few intriguing systems with orbital periods of several years. Nearby red dwarfs are prime candidates for NASA's Space Interferometry Mission (SIM) because the astrometric perturbations are largest for planets orbiting nearby stars of low mass. In addition, new multiple red dwarf systems can be targeted for mass determinations, thereby providing points on a comprehensive mass-luminosity relation for the most populous members of the Galaxy. These long-term observations began in 1999 as an NOAO Surveys program, and are continuing via the SMARTS Consortium. This work has been supported by the National Science Foundation (AST 98-20711 and 05-07711), NASA's Space Interferometry Mission, Georgia State University, and Northern Arizona University.

  8. Brown dwarfs as close companions to white dwarfs

    SciTech Connect

    Stringfellow, G.S.; Bodenheimer, P.; Black, D.C. Lunar and Planetary Institute, Houston, TX )

    1990-02-01

    The influence of the radiation flux emitted by a white dwarf primary on the evolution of a closely orbiting brown dwarf (BD) companion is investigated. Full stellar evolutionary calculations are presented for both isolated and thermal bath cases, including effects of large variations in the atmospheric grain opacities. High grain opacities significantly increase the radii of the BDs, but the thermal bath does not. The major influence of the thermal bath is to increase substantially the surface temperature and luminosity of the BD at a given age. These results are compared with the observational properties of the possible BD companion of the white dwarf G29-38. Inclusion of both physical effects, high grain opacities and thermal bath, increases the mass range (0.034-0.063 solar masses) of viable models significantly, yet the final determination of whether the object is indeed a BD requires improvements in the observations of the system's properties. 37 refs.

  9. Brown dwarfs as close companions to white dwarfs

    NASA Technical Reports Server (NTRS)

    Stringfellow, Guy S.; Bodenheimer, Peter; Black, David C.

    1990-01-01

    The influence of the radiation flux emitted by a white dwarf primary on the evolution of a closely orbiting brown dwarf (BD) companion is investigated. Full stellar evolutionary calculations are presented for both isolated and thermal bath cases, including effects of large variations in the atmospheric grain opacities. High grain opacities significantly increase the radii of the BDs, but the thermal bath does not. The major influence of the thermal bath is to increase substantially the surface temperature and luminosity of the BD at a given age. These results are compared with the observational properties of the possible BD companion of the white dwarf G29-38. Inclusion of both physical effects, high grain opacities and thermal bath, increases the mass range (0.034-0.063 solar masses) of viable models significantly, yet the final determination of whether the object is indeed a BD requires improvements in the observations of the system's properties.

  10. Be stars with white dwarf companions

    NASA Astrophysics Data System (ADS)

    Orio, Marina; Luna, Gerardo; Zemko, Polina; Kotulla, Ralf; Gallagher, Jay; Harbeck, Daniel

    2016-07-01

    A handful of supersoft X-ray sources in the Magellanic Clouds that could not be identified with transient nova outbursts turned out to be mainly massive close binaries. Recently, we have clearly identified a Be binary in M31, and are currently collecting data for another candidate in that galaxy. Work is in progress to assess whether the compact object companion really is a hydrogen burning white dwarf (the alternative being a massive stellar-mass black hole). If we can prove that Be+white dwarf interacting close binaries are common, and that hydrogen is often ignited on the white dwarf in these systems, we have discovered a new promising channel towards the explosion of supernovae of type Ia in star forming regions, without invoking double degenerate systems

  11. A low-temperature companion to a white dwarf star

    NASA Technical Reports Server (NTRS)

    Becklin, E. E.; Zuckerman, B.

    1988-01-01

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

  12. Cool white dwarf companions to four millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Bassa, C. G.; Antoniadis, J.; Camilo, F.; Cognard, I.; Koester, D.; Kramer, M.; Ransom, S. R.; Stappers, B. W.

    2016-02-01

    We report on photometric and spectroscopic observations of white dwarf companions to four binary radio millisecond pulsars, leading to the discovery of companions to PSRs J0614-3329, J1231-1411 and J2017+0603. We place limits on the brightness of the companion to PSR J0613-0200. Optical spectroscopy of the companion to PSR J0614-3329 identifies it as a DA-type white dwarf with a temperature of Teff = 6460 ± 80 K, a surface gravity log g = 7.0 ± 0.2 cgs and a mass of MWD = 0.24 ± 0.04 M⊙. We find that the distance to PSR J0614-3329 is smaller than previously estimated, removing the need for the pulsar to have an unrealistically high γ-ray efficiency. Comparing the photometry with predictions from white dwarf cooling models allows us to estimate temperatures and cooling ages of the companions to PSRs J0613-0200, J1231-1411 and J2017+0603. We find that the white dwarfs in these systems are cool Teff < 4000 K and old ≳ 5 Gyr. Thin hydrogen envelopes are required for these white dwarfs to cool to the observed temperatures, and we suggest that besides hydrogen shell flashes, irradiation driven mass loss by the pulsar may have been important.

  13. An unsuccessful search for brown dwarf companions to white dwarf stars

    NASA Technical Reports Server (NTRS)

    Shipman, Harry L.

    1986-01-01

    The results of a survey to detect excess infrared emission from white dwarf stars which would be attributable to a low mass companion are reviewed. Neither a simple comparison of spectroscopically identified white dwarf stars with the IRAS Point Source Catalog nor the coadding of IRAS survey data resulted in a detection of a brown dwarf. The seven nearest stars where the most stringent limits to the presence of a brown dwarf were obtained are listed, and an effort to detect brown dwarfs in the solar neighborhood is discussed.

  14. A USNO Search for Astrometric Companions to Brown Dwarfs IV

    NASA Astrophysics Data System (ADS)

    Bartlett, Jennifer L.; Vrba, F. J.; Munn, J. A.; Luginbuhl, C. B.; Tilleman, T.; Henden, A. A.

    2014-01-01

    Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no clear indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m (61-in) Kaj Strand Astrometric Reflector from 2000 September through 2006 June over periods from 2.0 to 5.3 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method. The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures. The brown dwarfs in this subsample have spectral types that range from late M through mid-T. None of them are known binaries. Distance estimates place six of these objects within the 25-pc limit of the Solar Neighborhood, and preliminary parallaxes place another three between 25 and 35 pc. These substellar objects are located north of -15° Dec. The brown dwarfs evaluated are 2MASS J00325937+1410371, 2MASS J01514155+1244300 (BF Ari) 2MASS J02074284+0000564, 2MASS J03095345-0753156, SDSS J083717.21-000018.0, 2MASS J11101001+0116130, 2MASS J13262981-0038314 (2MUCD 11143), 2MASS J17502385+4222373, 2MASS J23391025+1352284, and 2MASS J23565477-1553111. Analyses of another 30 brown dwarfs were presented earlier and the analyses of 19 more brown dwarfs are planned.

  15. A USNO Search for Astrometric Companions to Brown Dwarfs III

    NASA Astrophysics Data System (ADS)

    Bartlett, Jennifer L.; Vrba, F. J.; Munn, J. A.; Luginbuhl, C. B.; Tillman, T.; Henden, A. A.

    2013-01-01

    Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no clear indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m Strand Astrometric Reflector from 2000 October through 2006 June over periods from 1.3 to 5.4 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method. The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures. The brown dwarfs in this subsample have spectral types that range from early L through mid-T. None are known binaries. Distance estimates place all but two within the 25-pc limit of the Solar Neighborhood; one outlier has a distance of approximately 62 pc based on its preliminary parallax. These substellar objects are located north of -25° Dec. and lie between 13h and 23h in R.A. The brown dwarfs evaluated are 2MASS J13464634-0031501, SDSS J144600.60+002452.0, 2MASS J16241436+0029158, 2MASS J17580545+4633099, 2MASS J19010601+4718136, 2MASS J21241387+0059599, 2MASS J22425317+2542573, 2MASS J22443167+2043433, 2MASS J22541892+3123498, and 2MASS J22552907-0034336. Analyses of another 20 brown dwarfs were presented earlier and the analyses of 19 more brown dwarfs are planned.

  16. Do all barium stars have a white dwarf companion?

    NASA Technical Reports Server (NTRS)

    Dominy, J. F.; Lambert, D. L.

    1983-01-01

    International Ultraviolet Explorer short-wavelength, low-dispersion spectra were analyzed for four barium, two mild barium, and one R-type carbon star in order to test the hypothesis that the barium and related giants are produced by mass transfer from a companion now present as a white dwarf. An earlier tentative identification of a white dwarf companion to the mild barium star Zeta Cyg is confirmed. For the other stars, no ultraviolet excess attributable to a white dwarf is seen. Limits are set on the bolometric magnitude and age of a possible white dwarf companion. Since the barium stars do not have obvious progenitors among main-sequence and subgiant stars, mass transfer must be presumed to occur when the mass-gaining star is already on the giant branch. This restriction, and the white dwarf's minimum age, which is greater than 8 x 10 to the 8th yr, determined for several stars, effectively eliminates the hypothesis that mass transfer from an asymptotic giant branch star creates a barium star. Speculations are presented on alternative methods of producing a barium star in a binary system.

  17. Search for wide, ultracool companions of nearby T dwarfs

    NASA Astrophysics Data System (ADS)

    Osorio, M. R. Zapatero; Béjar, V. J. S.; Goldman, B.; Rebolo, R.; Bihain, G.; Bouy, H.

    2009-02-01

    We report on our on-going proper motion survey of very low-mass (>=5 MJup), ultracool (Teff>=350 K) companions of nearby, field T-type brown dwarfs in the Solar neighborhood. Our project is intended to provide seeing-limited images of the targets to find companion candidates at wide separations (>=15 AU) and within an area of 3'×3' around the primaries, thus complementing previous searches that explored the inner-most regions. Data are collected in the J-band with 2-4-m class telescopes; the completeness magnitude of our survey goes from ~19.5 to ~21 mag (depending on seeing and transparency conditions). So far we have studied 11 late-L and T-type brown dwarfs located at d<=16 pc of the Sun. Only one faint, proper motion companion candidate is found; its definitive confirmation highly requires third epoch data.

  18. The White Dwarf Binary Pathways Survey I: A sample of FGK stars with white dwarf companions

    NASA Astrophysics Data System (ADS)

    Parsons, S. G.; Rebassa-Mansergas, A.; Schreiber, M. R.; Gänsicke, B. T.; Zorotovic, M.; Ren, J. J.

    2016-08-01

    The number of spatially unresolved white dwarf plus main-sequence star binaries has increased rapidly in the last decade, jumping from only ˜30 in 2003 to over 3000. However, in the majority of known systems the companion to the white dwarf is a low mass M dwarf, since these are relatively easy to identify from optical colours and spectra. White dwarfs with more massive FGK type companions have remained elusive due to the large difference in optical brightness between the two stars. In this paper we identify 934 main-sequence FGK stars from the Radial Velocity Experiment (RAVE) survey in the southern hemisphere and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey in the northern hemisphere, that show excess flux at ultraviolet wavelengths which we interpret as the likely presence of a white dwarf companion. We obtained Hubble Space Telescope ultraviolet spectra for nine systems which confirmed that the excess is indeed caused, in all cases, by a hot compact companion, eight being white dwarfs and one a hot subdwarf or pre-helium white dwarf, demonstrating that this sample is very clean. We also address the potential of this sample to test binary evolution models and type Ia supernovae formation channels.

  19. The Frequency of Wide Companions to Planet-Host Stars: A New Wide Brown Dwarf Companion

    NASA Astrophysics Data System (ADS)

    Lodieu, N.; Pérez-Garrido, A.; Béjar, V. J. S.; Gauza, B.; Ruiz, M. T.; Rebolo, R.

    2015-07-01

    The aim of the project is to improve our knowledge of the multiplicity of planet-host stars at wide physical separations. We cross-matched approximately 6,200 square degrees imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We report two new stellar M dwarf companions as well as a T4.5 dwarf companion, at 6.3 arcmin (˜9,000 au) from the K7V star HIP 70849, yielding stellar and substellar frequencies of 5.4±3.8% and 2.7±2.7% (1σ), respectively. We refer the reader to our refereed paper (Lodieu et al. 2014) for more detailed information on the results.

  20. Do Some X-ray Stars Have White Dwarf Companions?

    NASA Technical Reports Server (NTRS)

    McCollum, Bruce

    1995-01-01

    Some Be stars which are intermittent C-ray sources may have white dwarf companions rather than neutron stars. It is not possible to prove or rule out the existence of Be+WD systems using X-ray or optical data. However, the presence of a white dwarf could be established by the detection of its EUV continuum shortward of the Be star's continuum turnover at 1OOOA. Either the detection or the nondetection of Be+WD systems would have implications for models of Be star variability, models of Be binary system formation and evolution, and models of wind-fed accretion.

  1. Do some x-ray stars have white dwarf companions

    NASA Technical Reports Server (NTRS)

    Mccollum, Bruce

    1995-01-01

    Some Be stars which are intermittent X-ray sources may have white dwarf companions rather than neutron stars. It is not possible to prove or rule out the existence of Be + WD systems using X-ray or optical data. However, the presence of a white dwarf could be established by the detection of its EUV continuum shortward of the Be star's continuum turnover at 100 A. Either the detection or the nondetection of Be + WD systems would have implications for models of Be star variability, models of Be binary system formation and evolution, and models of wind-fed accretion.

  2. Search for white dwarf companions of cool stars with peculiar element abundances

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, E.

    1984-01-01

    A search for a white dwarf companions of cool stars with peculiar element abundances was undertaken. One additional star the xi Cet, was found with a white dwarf companion. It was found that HR 1016, 56Uma, 16 Ser, have high excitation emission lines which indicate a high temperature object in the system. It is suggested that since these indications for high temperature companions were seen for all nearby Ba stars, it is highly probable that all Ba stars have white dwarf companions, and that the peculiar element abundances seen in the Ba stars are due to mass transfer. Observations, arguments and conclusions are presented. White dwarf companions were not found. Together with the Li and Be abundances and the chromospheric emission line spectra in these stars were studied. No white dwarf companions were seen for subgiant CH stars.

  3. DETECTION OF A WHITE DWARF COMPANION TO THE WHITE DWARF SDSSJ125733.63+542850.5

    SciTech Connect

    Marsh, T. R.; Gaensicke, B. T.; Steeghs, D.; Southworth, J.; Koester, D.; Harris, V.; Merry, L.

    2011-08-01

    SDSSJ125733.63+542850.5 (hereafter SDSSJ1257+5428) is a compact white dwarf binary from the Sloan Digital Sky Survey that exhibits high-amplitude radial velocity variations on a period of 4.56 hr. While an initial analysis suggested the presence of a neutron star or black hole binary companion, a follow-up study concluded that the spectrum was better understood as a combination of two white dwarfs. Here we present optical spectroscopy and ultraviolet fluxes which directly reveal the presence of the second white dwarf in the system. SDSSJ1257+5428's spectrum is a composite, dominated by the narrow-lined spectrum from a cool, low-gravity white dwarf (T{sub eff} {approx_equal} 6300 K, log g = 5-6.6) with broad wings from a hotter, high-mass white dwarf companion (11, 000-14, 000 K; {approx}1 M{sub sun}). The high-mass white dwarf has unusual line profiles which lack the narrow central core to H{alpha} that is usually seen in white dwarfs. This is consistent with rapid rotation with vsin i = 500-1750 km s{sup -1}, although other broadening mechanisms such as magnetic fields, pulsations, or a helium-rich atmosphere could also be contributory factors. The cool component is a puzzle since no evolutionary model matches its combination of low gravity and temperature. Within the constraints set by our data, SDSSJ1257+5428 could have a total mass greater than the Chandrasekhar limit and thus be a potential Type Ia supernova progenitor. However, SDSSJ1257+5428's unusually low-mass ratio q {approx} 0.2 suggests that it is more likely that it will evolve into an accreting double white dwarf (AM CVn star).

  4. RE 0044+09: A new K dwarf rapid rotator with a white dwarf companion

    NASA Technical Reports Server (NTRS)

    Kellett, Barry J.; Bromage, Gordon E.; Brown, Alexander; Jeffries, Robin D.; James, David J.; Kilkenny, David; Robb, Russell M.; Wonnacott, David; Lloyd, Christopher; Clayton, C.

    1995-01-01

    We report the discovery of a new K dwarf rapid rotator with a potential white dwarf companion. The white dwarf accounts for over 90% of the observed extreme ultraviolet flux detected from this system. Analysis of ROSAT Wide Field Camera (WFC) and IUE data both suggest a white dwarf temperature of approximately 28,700 K. Optical photometry and the IUE long wavelength prime (LWP) spectrum (with the white dwarf contribution removed) imply that the late-type star has a spectral type of K1-3 V, and a distance of 55 +/- 5 pc. Using this distance, the observed IUE SWP flux, and the best-fit temperature results in a white dwarf radius of 0.0088 solar radius. The estimated white dwarf mass is then approximately 0.91 solar mass; somewhat over-massive compared to field white dwarfs. Optical photometry of the K star reveals a 'spot' modulation period of approximately 10 hr (now observed over 3 yr). However, radial velocity observations have revealed no significant variations. Spectroscopic observations place a low limit on the lithium abundance, but do show rapid rotation with a v sin i of 90 +/- 10 km/s. The K star was detected as a radio source at 3.6 cm (on two occasions) and 6 cm by the Very Large Array (VLA). The most likely evolutionary scenario is that the K star and hot white dwarf from either a wide binary or common proper motion pair with an age of 0.1-0.1 Gyr-consistent with the evolutionary timescale of the white dwarf and the rapid rotation of the K star. However, from the proper motion of the K star, this system does not seem to be associated with any of the known young stellar groups.

  5. Faint Companions in the Close Environment of Starforming Dwarf Galaxies: possible overlooked starburst triggers? (Oral Contribution)

    NASA Astrophysics Data System (ADS)

    Noeske, K. G.; Iglesias-Páramo, J.; Vílchez, J. M.; Papaderos, P.; Fricke, K. J.

    Using the NASA Extragalactic Database, we have searched the close environment of 98 star-forming dwarf galaxies (SFDGs) from field- and low density environments for companion galaxies. Most of the found companions are dwarf galaxies, previously disregarded in environmental studies of SFDGs. Using a subsample at low redshifts, cz < 2000 km/s, i.e. less biased against dwarf companions, we find that 30% of the SFDGs have close companions within a projected linear separation s_p < 100 kpc and a redshift difference of (Delta cz) < 500 km/s. This fraction must be considered a lower limit, given the incompleteness of the available data sets and the non-negligible frequency of HI clouds in the vicinity of SFDGs, so that the majority of SFDGs should not be considered isolated. The redshift differences between companion candidates and sample SFDGs are typically smaller than ~250 km/s and concentrated towards lower values. This is similarly observed for dwarf satellites of spiral galaxies and suggests a physical association between the companion candidates and the sample SFDGs. SFDGs with a close companion do not show significant differences in their H(beta) equivalent widths and B-V colours as compared to isolated ones. However, the available data do not allow to rule out close dwarf companions as an influencing factor for star formation activity.

  6. LIMITS ON UNRESOLVED PLANETARY COMPANIONS TO WHITE DWARF REMNANTS OF 14 INTERMEDIATE-MASS STARS

    SciTech Connect

    Kilic, Mukremin; Gould, Andrew; Koester, Detlev

    2009-11-10

    We present Spitzer IRAC photometry of white dwarf remnants of 14 stars with M = 3-5 M{sub sun}. We do not detect mid-infrared excess around any of our targets. By demanding a 3sigma photometric excess at 4.5 mum for unresolved companions, we rule out planetary mass companions down to 5, 7, or 10 M {sub J} for 13 of our targets based on the Burrows et al. substellar cooling models. Combined with previous IRAC observations of white dwarf remnants of intermediate-mass stars, we rule out >=10M {sub J} companions around 40 white dwarfs and >=5M {sub J} companions around 10 white dwarfs.

  7. Stars of type MS with evidence of white dwarf companions. [IUE, Main Sequence (MS)

    NASA Technical Reports Server (NTRS)

    Peery, Benjamin F., Jr.

    1986-01-01

    A search for white dwarf companions of MS-type stars was conducted, using IUE. The overendowments of these stars in typical S-process nuclides suggest that they, like the Ba II stars, may owe their peculiar compositions to earlier mass transfer. Short-wavelength IUE spectra show striking emission line variability in HD35155, HD61913, and 4 Ori; HD35155 and 4 Ori show evidence of white dwarf companions.

  8. A SUBSTELLAR COMPANION TO THE WHITE DWARF-RED DWARF ECLIPSING BINARY NN Ser

    SciTech Connect

    Qian, S.-B.; Dai, Z.-B.; Liao, W.-P.; Zhu, L.-Y.; Liu, L.; Zhao, E. G.

    2009-11-20

    NN Ser is a short-period (P = 3.12 hr) close binary containing a very hot white dwarf primary with a mass of 0.535 M{sub sun} and a fully convective secondary with a mass of 0.111 M{sub sun}. The changes in the orbital period of the eclipsing binary were analyzed based on our five newly determined eclipse times together with those compiled from the literature. A small-amplitude (0fd00031) cyclic period variation with a period of 7.56 years was discovered to be superimposed on a possible long-term decrease. The periodic change was plausibly explained as the light-travel time effect via the presence of a tertiary companion. The mass of the tertiary companion is determined to be M{sub 3}sin i' = 0.0107(+-0.0017) M{sub sun} when a total mass of 0.646 M{sub sun} for NN Ser is adopted. For orbital inclinations i' >= 49.{sup 0}56, the mass of the tertiary component was calculated to be M {sub 3} <= 0.014 M{sub sun}; thus it would be an extrasolar planet. The third body is orbiting the white dwarf-red dwarf eclipsing binary at a distance shorter than 3.29 AU. Since the observed decrease rate of the orbital period is about two orders larger than that caused by gravitational radiation, it can be plausibly interpreted by magnetic braking of the fully convective component, which is driving this binary to evolve into a normal cataclysmic variable.

  9. DISCOVERY OF A PLANETARY-MASS COMPANION TO A BROWN DWARF IN TAURUS

    SciTech Connect

    Todorov, K.; Luhman, K. L.; McLeod, K. K.

    2010-05-01

    We have performed a survey for substellar companions to young brown dwarfs in the Taurus star-forming region using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. In these data, we have discovered a candidate companion at a projected separation of 0.''105 from one of the brown dwarfs, corresponding to 15 AU at the distance of Taurus. To determine if this object is a companion, we have obtained images of the pair at a second epoch with the adaptive optics system at Gemini Observatory. The astrometry from the Hubble and Gemini data indicates that the two objects share similar proper motions and thus are likely companions. We estimate a mass of 5-10 M {sub Jup} for the secondary based on a comparison of its bolometric luminosity to the predictions of theoretical evolutionary models. This object demonstrates that planetary-mass companions to brown dwarfs can form on a timescale of {tau} {approx}< 1 Myr. Companion formation on such a rapid timescale is more likely to occur via gravitational instability in a disk or fragmentation of a cloud core than through core accretion. The Gemini images also reveal a possible substellar companion ({rho} = 0.''23) to a young low-mass star that is 12.''4 from the brown dwarf targeted by Hubble. If these four objects comprise a quadruple system, then its hierarchical configuration would suggest that the fragmentation of molecular cloud cores can produce companions below 10 M {sub Jup}.

  10. 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.

  11. Combing the Brown Dwarf Desert with the APOGEE Catalog of Stellar and Substellar Companion Candidates

    NASA Astrophysics Data System (ADS)

    Troup, Nicholas William; De Lee, Nathan M.; Carlberg, Joleen K.; Nidever, David L.; Majewski, Steven R.; Stassun, Keivan; Covey, Kevin R.; Skrutskie, Michael F.; Allende-Prieto, Carlos; Hearty, Fred R.; APOGEE Substellar Companions Working Group

    2016-01-01

    While both exoplanets and stellar-mass companions have been found in extremely short-period orbits, there has been a paucity of brown dwarf (BD) companions orbiting Sun-like stars, a phenomenon known as the "Brown Dwarf Desert." However, more recent work has shown that this Desert might be limited in extent, only existing for small separation (a < 5-10 AU) companions, and may not be as "dry" as initially thought. It has been previously suggested that there may be an "F Dwarf Oasis," where the BD Desert observed for Solar-like stars ceases to exist for F dwarf stars. The Sloan Digital Sky Survey (SDSS-III) Apache Point Galactic Evolution Experiment (APOGEE) has compiled a catalog of ~400 of its most compelling stellar and substellar companion candidates orbiting host stars of various spectral types and evolutionary states. Among these candidates, approximately 100 had a derived companion mass in the BD regime (13-80 MJup), which is a significant increase compared to the number of known small separation (a < 1 AU) BD companions. Our sample appears to manifest the BD desert, but only for seperations < 0.2 AU rather than the previously held 5 AU. This is explained by one of the unique qualities of our sample when compared to previous companions surveys: Two-thirds of the BD candidates in our sample are orbiting evolved stars, most of which were F dwarfs during their main sequence lifetime, consistent with the notion of an F Dwarf Oasis. Using this sample, we further test this hypothesis by constraining the formation mechanisms of BD companions, and exploring their orbital evolution as their host evolves off the main sequence.

  12. Infrared spectrum and proper motion of the brown dwarf companion of HR 7329 in Tucanae

    NASA Astrophysics Data System (ADS)

    Guenther, E. W.; Neuhäuser, R.; Huélamo, N.; Brandner, W.; Alves, J.

    2001-01-01

    Up to now only four brown dwarf companions to normal stars have been found and confirmed by both spectroscopy and proper motion (namely Gl 229 B, G 196-3 B, Gl 570 D, and CoD-33 deg 7795 B). On the basis of an optical spectrum taken with HST/STIS Lowrance et al. (2000) recently pointed out another possible candidate companion. The companion candidate is located at a distance of 4{' '} from the A0-star HR 7329, which is considered as a member of a moving group of young stars in Tucanae located at a distance of only ~ 48 pc. In order to confirm or disregard the companion nature of the candidate, we have determined the proper motion of the brown dwarf candidate with an epoch difference of 1.8 years, and found that it is consistent with a co-moving companion of HR 7329. Additional to the proper motion measurement, we have also taken an H-band spectrum using ISAAC on the ESO-VLT. From this spectrum, we conclude that the companion candidate has spectral type M 7 to M 8, which is in agreement with the optical spectrum. We thus conclude that HR 7329 B is most likely a brown dwarf companion. The mass ratio of this pair (A0 to M 7-8, i.e. ~ 100:1) is the largest known among brown dwarf companions, which is relevant for studying the formation of brown dwarfs as companions. Based on observations obtained at the European Southern Observatory on Cerro Paranal and La Silla in program\\break 65.L-0144.

  13. Planets and Brown Dwarfs and Stars, Oh My! --- Companions Along the Road to the Nearest Stars

    NASA Astrophysics Data System (ADS)

    Henry, Todd J.; Davison, C. L.; Dieterich, S. B.; Ianna, P. A.; Jao, W. C.; Koerner, D. W.; Subasavage, J. P.; Tanner, A. M.; White, R. J.; RECONS

    2012-01-01

    RECONS (www.recons.org, REsearch Consortium On Nearby Stars) has been using astrometric techniques since 1999 to search for massive planets orbiting more than 130 nearby red and white dwarfs. Because of their proximity, nearby stars are natural locations to search for other solar systems --- the stars provide increased fluxes, larger astrometric perturbations, and higher probabilities for eventual resolution of planets than similar stars at larger distances. Unlike radial velocity searches, our astrometric effort is most sensitive to Jovian planets in Jovian orbits, i.e. those that span decades. We have discovered stellar companions with masses of a few hundred Jupiters, brown dwarf companions with masses of a few tens of Jupiters, and are now pushing into the realm of planets with masses of a few Jupiters around the nearest red dwarfs. Several previously unknown companions have been imaged via Gemini-AO observations, but we have also detected perturbations caused by enigmatic companions that elude direct detection. As we sweep through the mass regimes of stars to exoplanets for companions, we are now able to assess the various populations --- stars are common as companions, whereas brown dwarfs and massive planets are rare. We outline what we have discovered so far and place our exoplanet search results in context with an overview of the census of more than 60 stars with exoplanets known within 25 pc. This effort is supported by the NSF through grant AST-0908402 and via observations made possible by the SMARTS Consortium.

  14. Spectrum and proper motion of a brown dwarf companion of the T Tauri star CoD-33̂7795

    NASA Astrophysics Data System (ADS)

    Neuhäuser, R.; Guenther, E. W.; Petr, M. G.; Brandner, W.; Huélamo, N.; Alves, J.

    2000-08-01

    We present optical and infrared spectra as well as the proper motion of an H=12 mag object 2'' off the ~ 5 mag brighter spectroscopic binary star CoD-33̂7795 (=TWA-5), a member of the TW Hya association of T Tauri stars at ~ 55 pc. It was suggested as companion candidate by Lowrance et al. (1999) and Webb et al. (1999), but neither a spectrum nor the proper motion of the faint object were available before. Our spectra taken with FORS2 and ISAAC at the ESO-VLT reveal that the companion candidate has spectral type M8.5 to M9. It shows strong Hα emission and weak Na I absorption, both indicative of a young age. The faint object is clearly detected and resolved in our optical and infrared images, with a FWHM of 0.18'' in the FORS2 image. The faint object's proper motion, based on two year epoch difference, is consistent with the proper motion of CoD-33̂7795 by 5 Gaussian σ significance. From three different theoretical pre-main sequence models, we estimate the companion mass to be between ~ 15 and 40 Mjup, assuming the distance and age of the primary. A slight offset between the VLT and HST images with an epoch difference of two years can be interpreted as orbital motion. The probability for chance alignment of such a late-type object that close to CoD-33̂7795 with the correct proper motion is below 7.10-9. Hence, the faint object is physically associated with CoD-33̂7795, the 4th brown dwarf companion around a normal star confirmed by both spectrum and proper motion, the first around a pre-main sequence star. Based on observations obtained at the European Southern Observatory, Cerro Paranal, partly from program 65.L-0144 and partly based on public data released from FORS2 technical observations at the VLT Kueyen telescope

  15. An M Dwarf Companion and Its Induced Spiral Arms in the HD 100453 Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Dong, Ruobing; Zhu, Zhaohuan; Fung, Jeffrey; Rafikov, Roman; Chiang, Eugene; Wagner, Kevin

    2016-01-01

    Recent VLT/SPHERE near-infrared imaging observations revealed two spiral arms with a near m = 2 rotational symmetry in the protoplanetary disk around the ˜1.7 M⊙ Herbig star HD 100453. A ˜0.3 M⊙ M dwarf companion, HD 100453 B, was also identified at a projected separation of 120 AU from the primary. In this Letter, we carry out hydrodynamic and radiative transfer simulations to examine the scattered light morphology of the HD 100453 disk as perturbed by the companion on a circular and coplanar orbit. We find that the companion truncates the disk at ˜45 AU in scattered light images, and excites two spiral arms in the remaining (circumprimary) disk with a near m = 2 rotational symmetry. Both the truncated disk size and the morphology of the spirals are in excellent agreement with the SPHERE observations at Y, J, H, and K1-bands, suggesting that the M dwarf companion is indeed responsible for the observed double-spiral-arm pattern. Our model suggests that the disk is close to face on (inclination angle ˜5°), and that the entire disk-companion system rotates counterclockwise on the sky. The HD 100453 observations, along with our modeling work, demonstrate that double spiral arm patterns in near-infrared scattered light images can be generically produced by companions, and support future observations to identify the companions responsible for the arms observed in the MWC 758 and SAO 206462 systems.

  16. The white dwarf companion of the B a 2 star zeta Cap

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, E.

    1981-01-01

    The Ba II star zeta Cap has a white dwarf companion. Its T (sub eff) is determined to be 22000 K, its mass is approximately one solar mass. The importance of this finding for the explanation of abundance peculiarities is discussed.

  17. A SPITZER SEARCH FOR SUBSTELLAR COMPANIONS TO LOW-MASS WHITE DWARFS

    SciTech Connect

    Kilic, Mukremin; Brown, Warren R.; McLeod, B.

    2010-01-01

    The formation scenarios for single low-mass (M < 0.45 M{sub sun}) white dwarfs (WDs) include enhanced mass loss from a metal-rich progenitor star or a common envelope phase of a solar-like star with a close-in massive planet or a brown dwarf. Both scenarios suggest that low-mass WDs may have planets. Here, we present a Spitzer IRAC search for substellar and planetary mass companions to 14 low-mass WDs. One of our targets, HS 1653+7753, displays near- and mid-infrared flux excess. However, follow-up MMT observations show that this excess is due to a nearby resolved source, which is mostly likely a background object. Another target, PG 2257+162, shows flux excess compatible with a late-type stellar companion. We do not detect substellar companions to any of the remaining targets. In addition, eight of these stars do not show any radial velocity variations, ruling out stellar mass companions including other WDs. We conclude that a significant fraction of the low-mass WDs in our sample do not have stellar or massive brown dwarf companions.

  18. Detection of a white dwarf companion to the Hyades stars HD 27483

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1993-01-01

    We observed with IUE a white dwarf (WD) companion to the Hyades F6 V binary stars HD 27483. This system is known to be a close binary of two nearly equal stars with an orbital period of 3.05 days. Our IUE observations revealed the presence of a third star, a white dwarf with an effective temperature of 23,000 +/- 1000 K and a mass of approximately 0.6 solar mass. Its presence in the Hyades cluster with a known age permits me to derive the mass of its progenitor, which must have been about 2.3 solar masses. The presence of the white dwarf in a binary system opens the possibility that some of the envelope material, which was expelled by the WD progenitor, may have been collected by the F6 stars. We may thus be able to study abundance anomalies of the WD progenitor with known mass on the surface of the F6 companions.

  19. On the absence of young white dwarf companions to five technetium stars

    NASA Technical Reports Server (NTRS)

    Smith, Verne V.; Lambert, David L.

    1987-01-01

    A search for hot companions to five stars of type MS and S has been carried out using the IUE satellite. No hot companions were detected for the MS stars HR 85, 4647, 6702, and 8062, and the S star HR 8714. Limits on the luminosities of possible white dwarf companions provide lower limits of 2-5x10 to the 8th yr to the ages of any degenerate companions. All five stars exhibit strong Tc I lines, and the presence of technetium, with a half-life of 2.1x10 to the 5th yr, signifies recent nucleosynthesis. The limits on the ages of possible white dwarf companions that are equal to or greater than 1000 half-lives of Tc exclude the possibility that the s-process elemental enhancement seen in these MS and S stars resulted from mass transfer from a more highly evolved companion (as is probably the mechanism by which barium stars are created). These MS and S stars represent a sample of true thermally pulsing asymptotic giant-branch stars.

  20. A RADIO SEARCH FOR PULSAR COMPANIONS TO SLOAN DIGITAL SKY SURVEY LOW-MASS WHITE DWARFS

    SciTech Connect

    Agueeros, Marcel A.; Camilo, Fernando; Silvestri, Nicole M.; Anderson, Scott F.; Kleinman, S. J.; Liebert, James W.

    2009-05-20

    We have conducted a search for pulsar companions to 15 low-mass white dwarfs (LMWDs; M <0.4 M {sub sun}) at 820 MHz with the NRAO Green Bank Telescope (GBT). These LMWDs were spectroscopically identified in the Sloan Digital Sky Survey (SDSS), and do not show the photometric excess or spectroscopic signature associated with a companion in their discovery data. However, LMWDs are believed to evolve in binary systems and to have either a more massive white dwarf (WD) or a neutron star (NS) as a companion. Indeed, evolutionary models of low-mass X-ray binaries, the precursors of millisecond pulsars (MSPs), produce significant numbers of LMWDs, suggesting that the SDSS LMWDs may have NS companions. No convincing pulsar signal is detected in our data. This is consistent with the findings of van Leeuwen et al., who conducted a GBT search for radio pulsations at 340 MHz from unseen companions to eight SDSS WDs (five are still considered LMWDs; the three others are now classified as 'ordinary' WDs). We discuss the constraints our nondetections place on the probability P {sub MSP} that the companion to a given LMWD is a radio pulsar in the context of the luminosity and acceleration limits of our search; we find that P {sub MSP} < 10{sup +4} {sub -2}%.

  1. THE EFFECTS OF CLOSE COMPANIONS (AND ROTATION) ON THE MAGNETIC ACTIVITY OF M DWARFS

    SciTech Connect

    Morgan, Dylan P.; West, Andrew A.; Dhital, Saurav; Fuchs, Miriam; Garces, Ane; Catalan, Silvia; Silvestri, Nicole M.

    2012-10-01

    We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf main-sequence binaries from Rebassa-Mansergas et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space. Then using the SDSS Data Release 8 spectroscopic database, we construct a sample of 1756 WD+dM high-quality pairs from our color cuts and previous catalogs. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the H{alpha} emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types {<=} M7. Our results show that early-type M dwarfs ({<=}M4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just past the onset of full convection in M dwarfs), the activity fraction and lifetimes of WD+dM binary systems become more comparable to that of the field M dwarfs. One of the implications of having a close binary companion is presumed to be increased stellar rotation through disk disruption, tidal effects, or angular momentum exchange. Thus, we interpret the similarity in activity behavior between late-type dMs in WD+dM pairs and late-type field dMs to be due to a decrease in sensitivity in close binary companions (or stellar rotation), which has implications for the nature of magnetic activity in fully convective stars. Using the WD components of the pairs, we find WD cooling ages to use as an additional constraint on the age-activity relation for our sample. We find that, on average, active early-type dMs tend to be younger and that active late-type dMs span a much broader age regime making them

  2. The Mass Distribution of Companions to Low-mass White Dwarfs

    NASA Astrophysics Data System (ADS)

    Andrews, Jeff J.; Price-Whelan, Adrian M.; Agüeros, Marcel A.

    2014-12-01

    Measuring the masses of companions to single-line spectroscopic binary stars is (in general) not possible because of the unknown orbital plane inclination. Even when the mass of the visible star can be measured, only a lower limit can be placed on the mass of the unseen companion. However, since these inclination angles should be isotropically distributed, for a large enough, unbiased sample, the companion mass distribution can be deconvolved from the distribution of observables. In this work, we construct a hierarchical probabilistic model to infer properties of unseen companion stars given observations of the orbital period and projected radial velocity of the primary star. We apply this model to three mock samples of low-mass white dwarfs (LMWDs; M <~ 0.45 M ⊙) and a sample of post-common-envelope binaries. We use a mixture of two Gaussians to model the WD and neutron star (NS) companion mass distributions. Our model successfully recovers the initial parameters of these test data sets. We then apply our model to 55 WDs in the extremely low-mass (ELM) WD Survey. Our maximum a posteriori model for the WD companion population has a mean mass μWD = 0.74 M ⊙, with a standard deviation σWD = 0.24 M ⊙. Our model constrains the NS companion fraction f NS to be <16% at 68% confidence. We make samples from the posterior distribution publicly available so that future observational efforts may compute the NS probability for newly discovered LMWDs.

  3. NEW M, L, AND T DWARF COMPANIONS TO NEARBY STARS FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER

    SciTech Connect

    Luhman, Kevin L.; Loutrel, Nicholas P.; McCurdy, Nicholas S.; Melso, Nicole D.; Star, Kimberly M.; Terrien, Ryan C.; Mace, Gregory N.; McLean, Ian S.; Young, Michael D.; Rhode, Katherine L.; Davy Kirkpatrick, J.

    2012-12-01

    We present 11 candidate late-type companions to nearby stars identified with data from the Wide-field Infrared Survey Explorer (WISE) and the Two Micron All Sky Survey (2MASS). Eight of the candidates are likely to be companions based on their common proper motions with the primaries. The remaining three objects are rejected as companions, one of which is a free-floating T7 dwarf. Spectral types are available for five of the companions, which consist of M2V, M8.5V, L5, T8, and T8. Based on their photometry, the unclassified companions are probably two mid-M dwarfs and one late-M/early-L dwarf. One of the T8 companions, WISE J142320.84+011638.0, has already been reported by Pinfield and coworkers. The other T8 companion, ULAS J095047.28+011734.3, was discovered by Burningham and coworkers through the United Kingdom Infrared Telescope Infrared Deep Sky Survey, but its companionship has not been previously recognized in the literature. The L5 companion, 2MASS J17430860+8526594, is a new member of a class of L dwarfs that exhibit unusually blue near-IR colors. Among the possible mechanisms that have been previously proposed for the peculiar colors of these L dwarfs, low metallicity does not appear to be a viable explanation for 2MASS J17430860+8526594 since our spectrum of the primary suggests that its metallicity is not significantly subsolar.

  4. The dwarf galaxy UGC 5272 and its small companion galaxy

    NASA Technical Reports Server (NTRS)

    Hopp, U.; Schulte-Ladbeck, R. E.

    1991-01-01

    The present study of optical images and spectroscopy of the dwarf irregular galaxy UGC 5272 notes the presence, at 3.6 kpc, of a small neighboring galaxy which is also of irregular type and has a Holmberg diameter of 0.6 kpc. Attention is given to the possibility that the two galaxies, which are resolved into single stars, may form a physical pair. It is suggested that the blue-to-red supergiant ratio of UGC 5272 is high due to its low metallicity. While its extremely blue colors are suggestive of a recent starburst, the structural parameters of the galaxy are surprisingly normal. The gas contribution to total mass is high.

  5. A young white dwarf companion to pulsar B1620-26: evidence for early planet formation.

    PubMed

    Sigurdsson, Steinn; Richer, Harvey B; Hansen, Brad M; Stairs, Ingrid H; Thorsett, Stephen E

    2003-07-11

    The pulsar B1620-26 has two companions, one of stellar mass and one of planetary mass. We detected the stellar companion with the use of Hubble Space Telescope observations. The color and magnitude of the stellar companion indicate that it is an undermassive white dwarf (0.34 +/- 0.04 solar mass) of age 480 x 10(6) +/- 140 x 10(6) years. This places a constraint on the recent history of this triple system and supports a scenario in which the current configuration arose through a dynamical exchange interaction in the cluster core. This implies that planets may be relatively common in low-metallicity globular clusters and that planet formation is more widespread and has happened earlier than previously believed. PMID:12855802

  6. NO NEUTRON STAR COMPANION TO THE LOWEST MASS SDSS WHITE DWARF

    SciTech Connect

    Agueeros, Marcel A.; Camilo, Fernando; Heinke, Craig; Kilic, Mukremin; Anderson, Scott F.; Silvestri, Nicole M.; Freire, Paulo; Kleinman, Scot J.; Liebert, James W.

    2009-08-01

    SDSS J091709.55+463821.8 (hereafter J0917+4638) is the lowest surface gravity white dwarf (WD) currently known, with log g = 5.55 {+-} 0.05 (M {approx} 0.17 M{sub sun}). Such low-mass white dwarfs (LMWDs) are believed to originate in binaries that evolve into WD/WD or WD/neutron star (NS) systems. An optical search for J0917+4638's companion showed that it must be a compact object with a mass {>=}0.28 M{sub sun}. Here we report on Green Bank Telescope 820 MHz and XMM-Newton X-ray observations of J0917+4638 intended to uncover a potential NS companion to the LMWD. No convincing pulsar signal is detected in our radio data. Our X-ray observation also failed to detect X-ray emission from J0917+4638's companion, while we would have detected any of the millisecond radio pulsars in 47 Tuc. We conclude that the companion is almost certainly another WD.

  7. THE HYPERACTIVE L DWARF 2MASS J13153094-2649513: CONTINUED EMISSION AND A BROWN DWARF COMPANION

    SciTech Connect

    Burgasser, Adam J.; Sitarski, Breann N.; Logsdon, Sarah E.; Gelino, Christopher R.; Perrin, Marshall D.

    2011-09-20

    We report new observations of the unusually active, high proper motion L5e dwarf 2MASS J13153094-2649513. Optical spectroscopy with Magellan/MagE reveals persistent nonthermal emission, with narrow H I Balmer, Na I and K I lines all observed in emission. Low-resolution near-infrared spectroscopy with the Infrared Telescope Facility/SpeX Spectrograph indicates the presence of a low-temperature companion, which is resolved through multi-epoch laser guide star adaptive optics imaging at the W. M. Keck Observatory. The co-moving companion is separated by 338 {+-} 4 mas, and its relative brightness ({Delta}K{sub s} = 5.09 {+-} 0.10) makes this system the second-most-extreme flux ratio very-low-mass binary identified to date. Resolved near-infrared spectroscopy with Keck/OSIRIS identifies the companion as a T7 dwarf. The absence of Li I absorption in combined-light optical spectroscopy constrains the system age to {approx}>0.8-1.0 Gyr, while the system's kinematics and unusually low mass ratio (M{sub 2}/M{sub 1} = 0.3-0.6) suggest that it is even older. A coevality test of the components also indicates an older age, but reveals discrepancies between evolutionary and atmosphere model fits of the secondary, which are likely attributable to poor reproduction of its near-infrared spectrum. With a projected separation of 6.6 {+-} 0.9 AU, the 2MASS J1315-2649 system is too widely separated for mass exchange or magnetospheric interactions to be powering its persistent nonthermal emission. Rather, the emission is probably chromospheric in nature, consistent with an inversion in the age-activity relation in which strong magnetic fields are maintained by relatively old and massive ultracool dwarfs.

  8. A Keck LGS AO Search for Brown Dwarf and Planetary Mass Companions to Upper Scorpius Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Biller, Beth; Allers, Katelyn; Liu, Michael; Close, Laird M.; Dupuy, Trent

    2011-03-01

    We searched for binary companions to 20 young brown dwarfs in the Upper Scorpius association (145 pc, 5 Myr, nearest OB association) with the Laser Guide Star adaptive optics system and the facility infrared camera NIRC2 on the 10 m Keck II telescope. We discovered a 0farcs14 companion (20.9 ± 0.4 AU) to the <0.1 M sun object SCH J16091837-20073523. From spectral deconvolution of integrated-light near-IR spectroscopy of SCH1609 using the SpeX spectrograph (Rayner et al. 2003), we estimate primary and secondary spectral types of M6 ± 0.5 and M7 ± 1.0, corresponding to masses of 79 ± 17 M Jup and 55 ± 25 M Jup at an age of 5 Myr and masses of 84 ± 15 M Jup and 60 ± 25 M Jup at an age of 10 Myr. For our survey objects with spectral types later than M8, we find an upper limit on the binary fraction of <9% (1σ) at separations of 10-500 AU. We combine the results of our survey with previous surveys of Upper Sco and similar young regions to set the strongest constraints to date on binary fraction for young substellar objects and very low mass stars. The binary fraction for low-mass (<40 M Jup) brown dwarfs in Upper Sco is similar to that for T dwarfs in the field; for higher mass brown dwarfs and very low mass stars, there is an excess of medium-separation (10-50 AU projected separation) young binaries with respect to the field. These medium-separation binaries will likely survive to late ages.

  9. New neighbours. III. 21 new companions to nearby dwarfs, discovered with adaptive optics

    NASA Astrophysics Data System (ADS)

    Beuzit, J.-L.; Ségransan, D.; Forveille, T.; Udry, S.; Delfosse, X.; Mayor, M.; Perrier, C.; Hainaut, M.-C.; Roddier, C.; Roddier, F.; Martín, E. L.

    2004-10-01

    We present some results of a CFHT adaptive optics search for companions to nearby dwarfs. We identify 21 new components in solar neighbourhood systems, of which 13 were found while surveying a volume-limited sample of M dwarfs within 12 pc. We are obtaining complete observations for this subsample, to derive unbiased multiplicity statistics for the very-low-mass disk population. Additionally, we resolve for the first time 6 known spectroscopic or astrometric binaries, for a total of 27 newly resolved companions. A significant fraction of the new binaries has favourable parameters for accurate mass determinations. The newly resolved companion of Gl 120.1C was thought to have a spectroscopic minimum mass in the brown-dwarf range (Duquennoy & Mayor \\cite{duquennoy91}), and it contributed to the statistical evidence that a few percent of solar-type stars might have close-in brown-dwarf companions. We find that Gl 120.1C actually is an unrecognised double-lined spectroscopic pair. Its radial-velocity amplitude had therefore been strongly underestimated by Duquennoy & Mayor (\\cite{duquennoy91}), and it does not truly belong to their sample of single-lined systems with minimum spectroscopic mass below the substellar limit. We also present the first direct detection of Gl 494B, an astrometric brown-dwarf candidate. Its luminosity straddles the substellar limit, and it is a brown dwarf if its age is less than ˜300 Myr. A few more years of observations will ascertain its mass and status from first principles. Based on observations made at Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France and the University of Hawaii. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The

  10. THE MASS DISTRIBUTION OF COMPANIONS TO LOW-MASS WHITE DWARFS

    SciTech Connect

    Andrews, Jeff J.; Price-Whelan, Adrian M.; Agüeros, Marcel A.

    2014-12-20

    Measuring the masses of companions to single-line spectroscopic binary stars is (in general) not possible because of the unknown orbital plane inclination. Even when the mass of the visible star can be measured, only a lower limit can be placed on the mass of the unseen companion. However, since these inclination angles should be isotropically distributed, for a large enough, unbiased sample, the companion mass distribution can be deconvolved from the distribution of observables. In this work, we construct a hierarchical probabilistic model to infer properties of unseen companion stars given observations of the orbital period and projected radial velocity of the primary star. We apply this model to three mock samples of low-mass white dwarfs (LMWDs; M ≲ 0.45 M {sub ☉}) and a sample of post-common-envelope binaries. We use a mixture of two Gaussians to model the WD and neutron star (NS) companion mass distributions. Our model successfully recovers the initial parameters of these test data sets. We then apply our model to 55 WDs in the extremely low-mass (ELM) WD Survey. Our maximum a posteriori model for the WD companion population has a mean mass μ{sub WD} = 0.74 M {sub ☉}, with a standard deviation σ{sub WD} = 0.24 M {sub ☉}. Our model constrains the NS companion fraction f {sub NS} to be <16% at 68% confidence. We make samples from the posterior distribution publicly available so that future observational efforts may compute the NS probability for newly discovered LMWDs.

  11. Detection limits for close eclipsing and transiting substellar and planetary companions to white dwarfs in the WASP survey

    NASA Astrophysics Data System (ADS)

    Faedi, F.; West, R. G.; Burleigh, M. R.; Goad, M. R.; Hebb, L.

    2011-01-01

    We have performed extensive simulations to explore the possibility of detecting eclipses and transits of close, substellar and planetary companions to white dwarfs in WASP (the UK Wide-Angle Search for Planets) light curves. Our simulations cover companions ˜0.3 < Rpl < 12 R? and orbital periods 2 < P < 15 d, equivalent to orbital radii 0.003 < a < 0.1 au. For Gaussian random noise, WASP is sensitive to transits by companions as small as the Moon orbiting a V≃ 12 white dwarf. For fainter white dwarfs, WASP is sensitive to increasingly larger radius bodies. However, in the presence of correlated noise structure in the light curves, the sensitivity drops, although Earth-sized companions remain detectable, in principle, even in low signal-to-noise data. Mars-sized, and even Mercury-sized, bodies yield reasonable detection rates in high-quality light curves with little residual noise. We searched for eclipses and transit signals in long-term light curves of a sample of 194 white dwarfs resulting from a cross-correlation of the McCook & Sion catalogue and the WASP archive. No evidence for eclipsing or transiting substellar and planetary companions was found. We used this non-detection and results from our simulations to place tentative upper limits to the frequency of such objects in close orbits at white dwarfs. While only weak limits can be placed on the likely frequency of Earth-sized or smaller companions, brown dwarfs and gas giants (radius ≈Rjup) with periods <0.1-0.2 d must certainly be rare (<10 per cent). More stringent constraints likely require significantly larger white dwarf samples, higher observing cadence and continuous coverage. The short duration of eclipses and transits of white dwarfs compared to the cadence of WASP observations appears to be one of the main factors limiting the detection rate in a survey optimized for planetary transits of main-sequence stars.

  12. The hot white-dwarf companions of HR 1608, HR 8210, and HD 15638

    NASA Technical Reports Server (NTRS)

    Landsman, Wayne; Simon, Theodore; Bergeron, P.

    1993-01-01

    We have obtained low-dispersion IUE spectra of the late-type stars HD 15638 (F3 V), HR 1608 (=63 Eridani, KO IV), and HR 8210 (A8m). Each of these stars had been detected as a strong EUV source with the Wide Field Camera aboard the ROSAT satellite. The short-wavelength IUE spectrum of each star reveals the presence of a hot white-dwarf companion. We have fit the Lyman-alpha profile and UV continuum of each white dwarf using pure hydrogen models. The excellent fit of the data to the models provides confirmation of the Finley and Koester absolute calibration of the SWP camera of IUE. The UV data alone are insufficient to constrain the model gravity, but an additional constraint is provided by the photometric distance to the late-type primary. The most interesting of the three white dwarfs is the companion to HR 8210 for which our results imply a mass of 1.15 +0.05/-0.15 solar mass. This result is in good agreement with the lower limit on the mass derived from the spectroscopic orbit (greater than 1.1 solar mass), provided that the inclination is close to 90 deg.

  13. A SPITZER IRAC IMAGING SURVEY FOR T DWARF COMPANIONS AROUND M, L, AND T DWARFS: OBSERVATIONS, RESULTS, AND MONTE CARLO POPULATION ANALYSES

    SciTech Connect

    Carson, J. C.; Marengo, M.; Patten, B. M.; Hora, J. L.; Schuster, M. T.; Fazio, G. G.; Luhman, K. L.; Sonnett, S. M.; Allen, P. R.; Stauffer, J. R.; Schnupp, C.

    2011-12-20

    We report observational techniques, results, and Monte Carlo population analyses from a Spitzer Infrared Array Camera imaging survey for substellar companions to 117 nearby M, L, and T dwarf systems (median distance of 10 pc, mass range of 0.6 to {approx}0.05 M{sub Sun }). The two-epoch survey achieves typical detection sensitivities to substellar companions of [4.5 {mu}m] {<=} 17.2 mag for angular separations between about 7'' and 165''. Based on common proper motion analysis, we find no evidence for new substellar companions. Using Monte Carlo orbital simulations (assuming random inclination, random eccentricity, and random longitude of pericenter), we conclude that the observational sensitivities translate to an ability to detect 600-1100 K brown dwarf companions at semimajor axes {approx}>35 AU and to detect 500-600 K companions at semimajor axes {approx}>60 AU. The simulations also estimate a 600-1100 K T dwarf companion fraction of <3.4% for 35-1200 AU separations and <12.4% for the 500-600 K companions for 60-1000 AU separations.

  14. KOI 1224: A FOURTH BLOATED HOT WHITE DWARF COMPANION FOUND WITH KEPLER

    SciTech Connect

    Breton, R. P.; Van Kerkwijk, M. H.; Rappaport, S. A.; Carter, J. A.

    2012-04-01

    We present an analysis and interpretation of the Kepler binary system KOI 1224. This is the fourth binary found with Kepler that consists of a thermally bloated, hot white dwarf in a close orbit with a more or less normal star of spectral class A or F. As we show, KOI 1224 contains a white dwarf with T{sub eff} = 14, 700 {+-} 1000 K, mass = 0.22 {+-} 0.02 M{sub Sun }, and radius = 0.103 {+-} 0.002 R{sub Sun }, and an F-star companion of mass 1.59 {+-} 0.06 M{sub Sun} that is somewhat beyond its terminal-age main sequence. The orbital period is quite short at 2.69802 days. The ingredients that are used in the analysis are the Kepler binary light curve, including the detection of the Doppler boosting effect; the NUV and FUV fluxes from the GALEX images of this object; an estimate of the spectral type of the F-star companion; and evolutionary models of the companion designed to match its effective temperature and mean density. The light curve is modeled with a new code named Icarus which we describe in detail. Its features include the full treatment of orbital phase-resolved spectroscopy, Doppler boosting, irradiation effects, and transits/eclipses, which are particularly suited to irradiated eclipsing binaries. We interpret the KOI 1224 system in terms of its likely evolutionary history. We infer that this type of system, containing a bloated hot white dwarf, is the direct descendant of an Algol-type binary. In spite of this basic understanding of the origin of KOI 1224, we discuss a number of problems associated with producing a system with an orbital period this short.

  15. THE WHITE DWARF COMPANION OF A 2 M{sub sun} NEUTRON STAR

    SciTech Connect

    Bhalerao, Varun B.; Kulkarni, S. R.

    2011-08-10

    We report the optical discovery of the companion to the 2 M{sub sun} millisecond pulsar PSR J1614-2230. The optical colors show that the 0.5 M{sub sun} companion is a 2.2 Gyr old He-CO white dwarf. We infer that M-dot during the accretion phase is <10{sup -2} M-dot{sub edd}. We show that the pulsar was born with a spin close to its current value, well below the rebirth line. The spin-down parameters, the mass of the pulsar, and the age of the system challenge the simple recycling model for the formation of millisecond pulsars.

  16. PARALLACTIC MOTION FOR COMPANION DISCOVERY: AN M-DWARF ORBITING ALCOR

    SciTech Connect

    Zimmerman, Neil; Oppenheimer, Ben R.; Hinkley, Sasha; Hillenbrand, Lynne; Crepp, Justin R.; Brenner, Douglas; Sivaramakrishnan, Anand; Parry, Ian R.; King, David L.; Hunt, Stephanie; Beichman, Charles; Vasisht, Gautam; Roberts, Lewis C.; Burruss, Rick; Shao, Michael; Roberts, Jennifer E.; Soummer, Remi; Dekany, Richard; Bouchez, Antonin E-mail: bro@amnh.or

    2010-02-01

    The A5V star Alcor has an M3-M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point source at a contrast of approx6 J- and H-band magnitudes and separation of 1'' from the primary star. The use of an astrometric pupil plane grid allowed us to determine the projected separations between the companion and the coronagraphically occulted primary star to <=3 mas precision at two observation epochs. Our measurements demonstrate common parallactic and proper motion over the course of 103 days, significantly shorter than the period of time needed for most companion confirmations through proper motion measurements alone. This common parallax method is potentially more rigorous than common proper motion, ensuring that the neighboring bodies lie at the same distance, rather than relying on the statistical improbability that two objects in close proximity to each other on the sky move in the same direction. The discovery of a low-mass (approx0.25 M{sub sun}) companion around a bright (V = 4.0 mag), nearby (d= 25 pc) star highlights a region of binary star parameter space that to date has not been fully probed.

  17. New M, L, and T Dwarf Companions to Nearby Stars from the Wide-field Infrared Survey Explorer

    NASA Astrophysics Data System (ADS)

    Luhman, Kevin L.; Loutrel, Nicholas P.; McCurdy, Nicholas S.; Mace, Gregory N.; Melso, Nicole D.; Star, Kimberly M.; Young, Michael D.; Terrien, Ryan C.; McLean, Ian S.; Kirkpatrick, J. Davy; Rhode, Katherine L.

    2012-12-01

    We present 11 candidate late-type companions to nearby stars identified with data from the Wide-field Infrared Survey Explorer (WISE) and the Two Micron All Sky Survey (2MASS). Eight of the candidates are likely to be companions based on their common proper motions with the primaries. The remaining three objects are rejected as companions, one of which is a free-floating T7 dwarf. Spectral types are available for five of the companions, which consist of M2V, M8.5V, L5, T8, and T8. Based on their photometry, the unclassified companions are probably two mid-M dwarfs and one late-M/early-L dwarf. One of the T8 companions, WISE J142320.84+011638.0, has already been reported by Pinfield and coworkers. The other T8 companion, ULAS J095047.28+011734.3, was discovered by Burningham and coworkers through the United Kingdom Infrared Telescope Infrared Deep Sky Survey, but its companionship has not been previously recognized in the literature. The L5 companion, 2MASS J17430860+8526594, is a new member of a class of L dwarfs that exhibit unusually blue near-IR colors. Among the possible mechanisms that have been previously proposed for the peculiar colors of these L dwarfs, low metallicity does not appear to be a viable explanation for 2MASS J17430860+8526594 since our spectrum of the primary suggests that its metallicity is not significantly subsolar. Based on data from the Wide-field Infrared Survey Explorer, 2MASS, the W.M. Keck Observatory, the NASA Infrared Telescope Facility, the Hobby-Eberly Telescope, the WIYN Observatory at Kitt Peak National Observatory, the Spitzer Space Telescope, the Canada-France-Hawaii Telescope, and the European Southern Observatory New Technology Telescope.

  18. An irradiated brown-dwarf companion to an accreting white dwarf

    NASA Astrophysics Data System (ADS)

    Hernández Santisteban, Juan V.; Knigge, Christian; Littlefair, Stuart P.; Breton, Rene P.; Dhillon, Vikram S.; Gänsicke, Boris T.; Marsh, Thomas R.; Pretorius, Magaretha L.; Southworth, John; Hauschildt, Peter H.

    2016-05-01

    Interacting compact binary systems provide a natural laboratory in which to study irradiated substellar objects. As the mass-losing secondary (donor) in these systems makes a transition from the stellar to the substellar regime, it is also irradiated by the primary (compact accretor). The internal and external energy fluxes are both expected to be comparable in these objects, providing access to an unexplored irradiation regime. The atmospheric properties of donors are largely unknown, but could be modified by the irradiation. To constrain models of donor atmospheres, it is necessary to obtain accurate observational estimates of their physical properties (masses, radii, temperatures and albedos). Here we report the spectroscopic detection and characterization of an irradiated substellar donor in an accreting white-dwarf binary system. Our near-infrared observations allow us to determine a model-independent mass estimate for the donor of 0.055 ± 0.008 solar masses and an average spectral type of L1 ± 1, supporting both theoretical predictions and model-dependent observational constraints that suggest that the donor is a brown dwarf. Our time-resolved data also allow us to estimate the average irradiation-induced temperature difference between the dayside and nightside of the substellar donor (57 kelvin) and the maximum difference between the hottest and coolest parts of its surface (200 kelvin). The observations are well described by a simple geometric reprocessing model with a bolometric (Bond) albedo of less than 0.54 at the 2σ confidence level, consistent with high reprocessing efficiency, but poor lateral heat redistribution in the atmosphere of the brown-dwarf donor. These results add to our knowledge of binary evolution, in that the donor has survived the transition from the stellar to the substellar regime, and of substellar atmospheres, in that we have been able to test a regime in which the irradiation and the internal energy of a brown dwarf are

  19. An irradiated brown-dwarf companion to an accreting white dwarf.

    PubMed

    Santisteban, Juan V Hernández; Knigge, Christian; Littlefair, Stuart P; Breton, Rene P; Dhillon, Vikram S; Gänsicke, Boris T; Marsh, Thomas R; Pretorius, Magaretha L; Southworth, John; Hauschildt, Peter H

    2016-05-19

    Interacting compact binary systems provide a natural laboratory in which to study irradiated substellar objects. As the mass-losing secondary (donor) in these systems makes a transition from the stellar to the substellar regime, it is also irradiated by the primary (compact accretor). The internal and external energy fluxes are both expected to be comparable in these objects, providing access to an unexplored irradiation regime. The atmospheric properties of donors are largely unknown, but could be modified by the irradiation. To constrain models of donor atmospheres, it is necessary to obtain accurate observational estimates of their physical properties (masses, radii, temperatures and albedos). Here we report the spectroscopic detection and characterization of an irradiated substellar donor in an accreting white-dwarf binary system. Our near-infrared observations allow us to determine a model-independent mass estimate for the donor of 0.055 ± 0.008 solar masses and an average spectral type of L1 ± 1, supporting both theoretical predictions and model-dependent observational constraints that suggest that the donor is a brown dwarf. Our time-resolved data also allow us to estimate the average irradiation-induced temperature difference between the dayside and nightside of the substellar donor (57 kelvin) and the maximum difference between the hottest and coolest parts of its surface (200 kelvin). The observations are well described by a simple geometric reprocessing model with a bolometric (Bond) albedo of less than 0.54 at the 2σ confidence level, consistent with high reprocessing efficiency, but poor lateral heat redistribution in the atmosphere of the brown-dwarf donor. These results add to our knowledge of binary evolution, in that the donor has survived the transition from the stellar to the substellar regime, and of substellar atmospheres, in that we have been able to test a regime in which the irradiation and the internal energy of a brown dwarf are

  20. A 3D Search for Companions to 12 Nearby M Dwarfs

    NASA Astrophysics Data System (ADS)

    Davison, Cassy L.; White, R. J.; Henry, T. J.; Riedel, A. R.; Jao, W.-C.; Bailey, J. I., III; Quinn, S. N.; Cantrell, J. R.; Subasavage, J. P.; Winters, J. G.

    2015-03-01

    We present a carefully vetted equatorial (±30\\circ decl.) sample of all known single (within 4″) mid M dwarfs (M2.5 V-M8.0 V) extending out to 10 pc; their proximity and low masses make them ideal targets for planet searches. For this sample of 58 stars, we provide VJ, RKC, and IKC photometry, new low-dispersion optical (6000-9000 Å) spectra from which uniform spectral types are determined, multi-epoch Hα equivalent widths, and gravity-sensitive Na i indices. For 12 of these 58 stars, strict limits are placed on the presence of stellar and substellar companions based on a pioneering program described here that utilizes precise infrared radial velocities (RVs) and optical astrometric measurements in an effort to search for Jupiter-mass, brown dwarf, and stellar-mass companions. Our infrared RV precision using CSHELL at NASA’s Infrared Telescope Facility is ˜90 m s-1 over timescales from 13 days to 5 yr. With our spectroscopic results the mean companion masses that we rule out of existence are 1.5 MJUP or greater in 10 day orbital periods and 7 MJUP or greater in 100 day orbital periods. We use these spectra to determine rotational velocities and absolute RVs of these 12 stars. Our mean astrometric precision using Research Consortium on Nearby Stars (RECONS; www.recons.org) data from the 0.9 m telescope at Cerro Tololo Inter-American Observatory is ˜3 mas over baselines ranging from 9 to 13 yr. With our astrometric results the mean companion masses that we rule out of existence are greater than 11.5 MJUP with an orbital period of 4 yr and greater than 7.5 MJUP with an orbital period of 8 yr. Although we do not detect companions around our subsample of 12 stars, we demonstrate that our two techniques probe a regime that is commonly missed in other companion searches of late-type stars.

  1. THE TRENDS HIGH-CONTRAST IMAGING SURVEY. III. A FAINT WHITE DWARF COMPANION ORBITING HD 114174

    SciTech Connect

    Crepp, Justin R.; Johnson, John Asher; Howard, Andrew W.; Marcy, Geoffrey W.; Gianninas, Alexandros; Kilic, Mukremin; Wright, Jason T.

    2013-09-01

    The nearby Sun-like star HD 114174 exhibits a strong and persistent Doppler acceleration indicating the presence of an unseen distant companion. We have acquired high-contrast imaging observations of this star using NIRC2 at Keck and report the direct detection of the body responsible for causing the ''trend''. HD 114174 B has a projected separation of 692 {+-} 9 mas (18.1 AU) and is 10.75 {+-} 0.12 mag (contrast of 5 Multiplication-Sign 10{sup -5}) fainter than its host in the K-band, requiring aggressive point-spread function subtraction to identify. Our astrometric time baseline of 1.4 yr demonstrates physical association through common proper motion. We find that the companion has absolute magnitude, M{sub J} = 13.97 {+-} 0.11, and colors, J - K = 0.12 {+-} 0.16 mag. These characteristics are consistent with an Almost-Equal-To T3 dwarf, initially leading us to believe that HD 114174 B was a substellar object. However, a dynamical analysis that combines radial velocity measurements with available imaging data indicates a minimum mass of 0.260 {+-} 0.010 M{sub Sun }. We conclude that HD 114174 B must be a white dwarf. Assuming a hydrogen-rich composition, atmospheric and evolutionary model fits yield an effective temperature T{sub eff} = 8200 {+-} 4000 K, surface gravity log g = 8.90 {+-} 0.02, and cooling age of t{sub c} Almost-Equal-To 3.4 Gyr, which is consistent with the 4.7{sup +2.3}{sub -2.6} Gyr host star isochronal age estimate. HD 114174 B is a benchmark object located only 26.14 {+-} 0.37 pc from the Sun. It may be studied at a level of detail comparable to Sirius and Procyon, and used to understand the link between the mass of white dwarf remnants with that of their progenitors.

  2. Is beryllium ultra-depletion in solar-type stars linked to the presence of a white dwarf companion?

    NASA Astrophysics Data System (ADS)

    Desidera, S.; D'Orazi, V.; Lugaro, M.

    2016-03-01

    Context. Abundance studies of solar-type stars revealed a small fraction of objects with extreme depletion of beryllium. Aims: We investigate the possible link between the beryllium depletion and the presence of companions. Methods: The classical methods (radial velocity, astrometry, imaging) used to search for binary companions were exploited. We also performed a chemical analysis to identify binaries by the alteration in abundances that is produced by the accretion of material lost by a former evolved companion. Results: We found that all the four previously investigated stars that were found to be ultra-depleted in Be are binaries. In two cases the companion is a white dwarf, and in the other two cases the companion might be a white dwarf or a main-sequence star. One new barium star was identified. Conclusions: We speculate that the interaction with the white dwarf progenitor caused an alteration in the abundance pattern of the star, which resulted in severe beryllium depletion. Possible mechanisms such as thermohaline mixing, episodic accretion, and rotational mixing are discussed. We also briefly discuss predictions for validating this scenario.

  3. MOA-2010-BLG-073L: AN M-DWARF WITH A SUBSTELLAR COMPANION AT THE PLANET/BROWN DWARF BOUNDARY

    SciTech Connect

    Street, R. A.; Tsapras, Y.; Choi, J.-Y.; Han, C.; Furusawa, K.; Hundertmark, M.; Horne, K.; Dominik, M.; Browne, P.; Bajek, D.; Sumi, T.; Bond, I. A.; Wouters, D.; Zellem, R.; Udalski, A.; Snodgrass, C.; Kains, N.; Bramich, D. M.; Steele, I. A.; Collaboration: RoboNet Collaboration; MOA Collaboration; OGLE Collaboration; muFUN Collaboration; PLANET Collaboration; MiNDSTEp Collaboration; and others

    2013-01-20

    We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales >200 days. Its dereddened color, (V - I) {sub S,0}, is 1.221 {+-} 0.051 mag, and from our lens model we derive a source radius of 14.7 {+-} 1.3 R {sub Sun }, suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 {+-} 0.0006. The Einstein crossing time of the event, t {sub E} = 44.3 {+-} 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, D{sub L} = 2.8 {+-} 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with M {sub L,1} = 0.16 {+-} 0.03 M {sub Sun }, while the companion has M {sub L,2} = 11.0 {+-} 2.0 M {sub J}, putting it in the boundary zone between planets and brown dwarfs.

  4. ULAS J141623.94+134836.3: A Blue T Dwarf Companion to a Blue L Dwarf

    NASA Astrophysics Data System (ADS)

    Burgasser, Adam J.; Looper, Dagny; Rayner, John T.

    2010-06-01

    We confirm the substellar nature of ULAS J141623.94+134836.3 (aka SDSS J1416+1348B), a common proper motion companion to the blue L dwarf SDSS J141624.08+134826.7 identified by Burningham et al. and Scholz. Low-resolution 0.8-2.4 μm spectroscopy obtained with the Infrared Telescope Facility/SpeX shows strong H2O and CH4 absorption bands, consistent with a T7.5 spectral type, and we see possible indications of NH3 absorption in the 1.0-1.3 μm region. More importantly, the spectrum of SDSS J1416+1348B shows a broadened Y-band peak and highly suppressed K-band flux, both indicative of high surface gravity and/or subsolar metallicity. These traits are verified through spectral model fits, from which we derive atmospheric parameters T eff = 650 ± 60 K, log g = 5.2 ± 0.4 cgs, [M/H] <= -0.3, and Kzz = 104 cm2 s-1, the temperature being significantly warmer than that estimated by Burningham et al. These fits also indicate a model-dependent spectroscopic distance of 10.6+3.0 -2.8 pc for SDSS J1416+1348B, formally consistent with the 7.9 ± 1.7 pc astrometric distance for SDSS J1416+1348A from Scholz. The common peculiarities of these two co-spatial, co-moving sources suggest that their unusual blue colors—and those of other blue L and T dwarfs in general—arise from age/gravity or metallicity effects, rather than cloud properties alone.

  5. DETECTION OF WHITE DWARF COMPANIONS TO BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 188: DIRECT EVIDENCE FOR RECENT MASS TRANSFER

    SciTech Connect

    Gosnell, Natalie M.; Mathieu, Robert D.; Geller, Aaron M.; Sills, Alison; Leigh, Nathan; Knigge, Christian

    2014-03-01

    Several possible formation pathways for blue straggler stars have been developed recently, but no one pathway has yet been observationally confirmed for a specific blue straggler. Here we report the first findings from a Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel far-UV photometric program to search for white dwarf companions to blue straggler stars. We find three hot and young white dwarf companions to blue straggler stars in the 7 Gyr open cluster NGC 188, indicating that mass transfer in these systems ended less than 300 Myr ago. These companions are direct and secure observational evidence that these blue straggler stars were formed through mass transfer in binary stars. Their existence in a well-studied cluster environment allows for observational constraints of both the current binary system and the progenitor binary system, mapping the entire mass transfer history.

  6. Microarcsecond VLBI Pulsar Astrometry with PSRπ. I. Two Binary Millisecond Pulsars with White Dwarf Companions

    NASA Astrophysics Data System (ADS)

    Deller, A. T.; Vigeland, S. J.; Kaplan, D. L.; Goss, W. M.; Brisken, W. F.; Chatterjee, S.; Cordes, J. M.; Janssen, G. H.; Lazio, T. J. W.; Petrov, L.; Stappers, B. W.; Lyne, A.

    2016-09-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars and multiwavelength observations of their companion stars. Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145–0750, over a two-year period and measured their distances to be {700}-10+14 pc and {613}-14+16 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M∼ 0.85 {M}ȯ ) white dwarf companions. Finally, we show that several measurements of the parallax and proper motion of PSR J1022+1001 and PSR J2145–0750 obtained by pulsar timing array projects are incorrect, differing from the more precise VLBI values by up to 5σ. We investigate possible causes for the discrepancy, and find that imperfect modeling of the solar wind is a likely candidate for the errors in the timing model given the low ecliptic latitude of these two pulsars.

  7. Formation of millisecond pulsars with low-mass helium white dwarf companions in very compact binaries

    SciTech Connect

    Jia, Kun; Li, X.-D.

    2014-08-20

    Binary millisecond pulsars (BMSPs) are thought to have evolved from low-mass X-ray binaries (LMXBs). If the mass transfer in LMXBs is driven by nuclear evolution of the donor star, the final orbital period is predicted to be well correlated with the mass of the white dwarf (WD), which is the degenerate He core of the donor. Here we show that this relation can be extended to very small WD mass (∼0.14-0.17 M {sub ☉}) and narrow orbital period (about a few hours), depending mainly on the metallicities of the donor stars. There is also discontinuity in the relation, which is due to the temporary contraction of the donor when the H-burning shell crosses the hydrogen discontinuity. BMSPs with low-mass He WD companions in very compact binaries can be accounted for if the progenitor binary experienced very late Case A mass transfer. The WD companion of PSR J1738+0333 is likely to evolve from a Pop II star. For PSR J0348+0432, to explain its extreme compact orbit in the Roche-lobe-decoupling phase, even lower metallicity (Z = 0.0001) is required.

  8. Microarcsecond VLBI Pulsar Astrometry with PSRπ. I. Two Binary Millisecond Pulsars with White Dwarf Companions

    NASA Astrophysics Data System (ADS)

    Deller, A. T.; Vigeland, S. J.; Kaplan, D. L.; Goss, W. M.; Brisken, W. F.; Chatterjee, S.; Cordes, J. M.; Janssen, G. H.; Lazio, T. J. W.; Petrov, L.; Stappers, B. W.; Lyne, A.

    2016-09-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars and multiwavelength observations of their companion stars. Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145–0750, over a two-year period and measured their distances to be {700}-10+14 pc and {613}-14+16 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M˜ 0.85 {M}ȯ ) white dwarf companions. Finally, we show that several measurements of the parallax and proper motion of PSR J1022+1001 and PSR J2145–0750 obtained by pulsar timing array projects are incorrect, differing from the more precise VLBI values by up to 5σ. We investigate possible causes for the discrepancy, and find that imperfect modeling of the solar wind is a likely candidate for the errors in the timing model given the low ecliptic latitude of these two pulsars.

  9. BANYAN. VI. Discovery of a Companion at the Brown Dwarf/Planet-Mass Limit to a Tucana–Horologium M Dwarf

    NASA Astrophysics Data System (ADS)

    Artigau, Étienne; Gagné, Jonathan; Faherty, Jacqueline; Malo, Lison; Naud, Marie-Eve; Doyon, René; Lafrenière, David; Beletsky, Yuri

    2015-06-01

    We report the discovery of a substellar companion to 2MASS J02192210–3925225, a young M6 γ candidate member of the Tucana–Horologium association (30–40 Myr). This L4 γ companion has been discovered with seeing-limited direct imaging observations; at a 4″ separation (160 AU) and a modest contrast ratio, it joins the very short list of young low-mass companions amenable to study without the aid of adaptive optics, enabling its characterization with a much wider suite of instruments than is possible for companions uncovered by high-contrast imaging surveys. With a model-dependent mass of 12–15 {M}{Jup}, it straddles the boundary between the planet and brown dwarf mass regimes. We present near-infrared spectroscopy of this companion and compare it to various similar objects uncovered in the last few years. The J0219–3925 system falls in a sparsely populated part of the host mass versus mass ratio diagram for binaries; the dearth of known similar companions may be due to observational biases in previous low-mass companion searches.

  10. Follow-up spectroscopic observations of HD 107148 B: A new white dwarf companion of an exoplanet host star

    NASA Astrophysics Data System (ADS)

    Mugrauer, M.; Dinçel, B.

    2016-07-01

    We report on our follow-up spectroscopy of HD 1071478 B, a recently detected faint co-moving companion of the exoplanet host star HD 107148 A. The companion is separated from its primary star by about 35 arcsec (or 1790 AU of projected separation) and its optical and near infrared photometry is consistent with a white dwarf, located at the distance of HD 107148 A. In order to confirm the white dwarf nature of the co-moving companion, we obtained follow-up spectroscopic observations of HD 107148 B with CAFOS at the CAHA 2.2 m telescope. According to our CAFOS spectroscopy HD 107148 B is a DA white dwarf with an effective temperature in the range between 5900 and 6400 K. The properties of HD 107148 B can further be constrained with the derived effective temperature and the known visual and infrared photometry of the companion, using evolutionary models of DA white dwarfs. We obtain for HD 107148 B a mass of 0.56±0.05 M_ȯ, a luminosity of (2.0±0.2)×10-4 L_ȯ, log g [cm s-2])=7.95±0.09, and a cooling age of 2100±270 Myr. With its white dwarf companion the exoplanet host star HD 107148 A forms an evolved stellar system, which hosts at least one exoplanet. So far, only few of these evolved systems are known, which represent only about 5 % of all known exoplanet host multiple stellar systems. HD 107148 B is the second confirmed white dwarf companion of an exoplanet host star with a projected separation to its primary star of more than 1000 AU. 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).

  11. Timing of a young mildly recycled pulsar with a massive white dwarf companion

    NASA Astrophysics Data System (ADS)

    Lazarus, P.; Tauris, T. M.; Knispel, B.; Freire, P. C. C.; Deneva, J. S.; Kaspi, V. M.; Allen, B.; Bogdanov, S.; Chatterjee, S.; Stairs, I. H.; Zhu, W. W.

    2014-01-01

    We report on timing observations of the recently discovered binary pulsar PSR J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is in a 9.4-h orbit with a massive, MWD > 0.93 M⊙, white dwarf (WD) companion. We present, for the first time, a phase-coherent timing solution, with precise spin, astrometric and Keplerian orbital parameters. This shows that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order of magnitude than any other recycled pulsar-massive WD system. We derive an upper limit on the true age of the system of 150 Myr. We investigate the formation of PSR J1952+2630 using detailed modelling of the mass-transfer process from a naked helium star on to the neutron star following a common-envelope phase (Case BB Roche lobe overflow). From our modelling of the progenitor system, we constrain the accretion efficiency of the neutron star, which suggests a value between 100 and 300 per cent of the Eddington accretion limit. We present numerical models of the chemical structure of a possible oxygen-neon-magnesium WD companion. Furthermore, we calculate the past and the future spin evolution of PSR J1952+2630, until the system merges in about 3.4 Gyr due to gravitational wave emission. Although we detect no relativistic effects in our timing analysis, we show that several such effects will become measurable with continued observations over the next 10 yr; thus, PSR J1952+2630 has potential as a testbed for gravitational theories.

  12. Point Source Polarimetry with the Gemini Planet Imager: Sensitivity Characterization with T5.5 Dwarf Companion HD 19467 B

    NASA Technical Reports Server (NTRS)

    Jensen-Clem, Rebecca; Millar-Blanchaer, Max; Mawet, Dimitri; Graham, James R.; Wallace, J. Kent; Macintosh, Bruce; Hinkley, Sasha; Wiktorowicz, Sloane J.; Perrin, Marshall D.; Marley, Mark S.; Fitzgerald, Michael P.; Oppenheimer, Rebecca; Ammons, S. Mark; Rantakyro, Fredrik T.; Marchis, Franck

    2016-01-01

    Detecting polarized light from self-luminous exoplanets has the potential to provide key information about rotation, surface gravity, cloud grain size, and cloud coverage. While field brown dwarfs with detected polarized emission are common, no exoplanet or substellar companion has yet been detected in polarized light. With the advent of high contrast imaging spectro-polarimeters such as GPI and SPHERE, such a detection may now be possible with careful treatment of instrumental polarization. In this paper, we present 28 minutes of H-band GPI polarimetric observations of the benchmark T5.5 companion HD 19467 B. We detect no polarization signal from the target, and place an upper limit on the degree of linear polarization of pCL99:73% less than 1:7%. We discuss our results in the context of T dwarf cloud models and photometric variability.

  13. Point Source Polarimetry with the Gemini Planet Imager: Sensitivity Characterization with T5.5 Dwarf Companion HD 19467 B

    NASA Astrophysics Data System (ADS)

    Jensen-Clem, Rebecca; Millar-Blanchaer, Max; Mawet, Dimitri; Graham, James R.; Wallace, J. Kent; Macintosh, Bruce; Hinkley, Sasha; Wiktorowicz, Sloane J.; Perrin, Marshall D.; Marley, Mark S.; Fitzgerald, Michael P.; Oppenheimer, Rebecca; Ammons, S. Mark; Rantakyrö, Fredrik T.; Marchis, Franck

    2016-04-01

    Detecting polarized light from self-luminous exoplanets has the potential to provide key information about rotation, surface gravity, cloud grain size, and cloud coverage. While field brown dwarfs with detected polarized emission are common, no exoplanet or substellar companion has yet been detected in polarized light. With the advent of high contrast imaging spectro-polarimeters such as GPI and SPHERE, such a detection may now be possible with careful treatment of instrumental polarization. In this paper, we present 28 minutes of H-band GPI polarimetric observations of the benchmark T5.5 companion HD 19467 B. We detect no polarization signal from the target, and place an upper limit on the degree of linear polarization of {p}{CL99.73%}≤slant 2.4%. We discuss our results in the context of T dwarf cloud models and photometric variability.

  14. OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?

    SciTech Connect

    Dong, S; Gould, A; Udalski, A; Anderson, J; Christie, G W; Gaudi, B S; Jaroszynski, M; Kubiak, M; Szymanski, M K; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; DePoy, D L; Fox, D B; Gal-Yam, A; Han, C; Lepine, S; McCormick, J; Ofek, E; Park, B; Pogge, R W; Abe, F; Bennett, D P; Bond, I A; Britton, T R; Gilmore, A C; Hearnshaw, J B; Itow, Y; Kamiya, K; Kilmartin, P M; Korpela, A; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Ohnishi, K; Okada, C; Rattenbury, N; Saito, T; Sako, T; Sasaki, M; Sullivan, D; Sumi, T; Tristram, P J; Yanagisawa, T; Yock, P M; Yoshoika, T; Albrow, M D; Beaulieu, J P; Brillant, S; Calitz, H; Cassan, A; Cook, K H; Coutures, C; Dieters, S; Prester, D D; Donatowicz, J; Fouque, P; Greenhill, J; Hill, K; Hoffman, M; Horne, K; J?rgensen, U G; Kane, S; Kubas, D; Marquette, J B; Martin, R; Meintjes, P; Menzies, J; Pollard, K R; Sahu, K C; Vinter, C; Wambsganss, J; Williams, A; Bode, M; Bramich, D M; Burgdorf, M; Snodgrass, C; Steele, I; Doublier, V; Foelmi, C

    2008-04-18

    We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher-order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is a foreground M dwarf, with mass M = 0.46 {+-} 0.04M{sub {circle_dot}}, distance D{sub l} = 3.3 {+-} 0.4 kpc, and thick-disk kinematics {nu}{sub LSR} {approx} 103 km s{sup -1}. From the best-fit model, the planet has mass M{sub p} = 3.5 {+-} 0.3 M{sub Jupiter}, lies at a projected separation r{sub {perpendicular}} = 3.6 {+-} 0.2 AU from its host and has an equilibrium temperature of T {approx} 50 K, i.e., similar to Neptune. A degenerate model less favored by {Delta}{sub {chi}}{sup 2} {approx} 4 gives essentially the same planetary mass M{sub p} = 3.3 {+-} 0.3 M{sub Jupiter} with a smaller projected separation, r{sub {perpendicular}} = 2.1 {+-} 0.1 AU, and higher equilibrium temperature T {approx} 68 K. These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf. However, the formation of such high-mass planetary companions in the outer regions of M-dwarf planetary systems is predicted to be unlikely within the core-accretion scenario. There are a number of caveats to this analysis, but these could mostly be resolved by a single astrometric measurement a few years after the event.

  15. Discovery of a Young Planetary Mass Companion to the Nearby M Dwarf VHS J125601.92-125723.9

    NASA Astrophysics Data System (ADS)

    Gauza, Bartosz; Béjar, Victor J. S.; Pérez-Garrido, Antonio; Rosa Zapatero Osorio, Maria; Lodieu, Nicolas; Rebolo, Rafael; Pallé, Enric; Nowak, Grzegorz

    2015-05-01

    In a search for common proper motion companions using the VISTA Hemisphere Survey (VHS) and the 2MASS catalogs we have identified a very red (J-{{K}s}=2.47 mag) late-L dwarf companion of a previously unrecognized M dwarf VHS J125601.92-125723.9 (hereafter VHS 1256-1257), located at a projected angular separation of 8.″ 06 ± 0.″ 03. In this work we present a suite of astrometric, photometric, and spectroscopic observations of this new pair in an effort to confirm the companionship and characterize the components. From low-resolution (R ˜ 130-600) optical and near-infrared spectroscopy we classified the primary and the companion as M7.5 ± 0.5 and L7 ± 1.5, respectively. The primary shows slightly weaker alkali lines than field dwarfs of similar spectral type, but still consistent with either a high-gravity dwarf or a younger object of hundreds of millions of years. The secondary shows spectral features characteristic for low surface gravity objects at ages below several hundred million years, like the peaked triangular shape of the H-band continuum and alkali lines weaker than in field dwarfs of the same spectral type. The absence of lithium in the atmosphere of the primary and the likely kinematic membership to the Local Association allowed us to constrain the age of the system to the range of 150-300 Myr. We report a measurement of the trigonometric parallax π = 78.8 ± 6.4 mas, which translates into a distance of 12.7 ± 1.0 pc; the pair thus has a projected physical separation of 102 ± 9 AU. We derived the bolometric luminosities of the components and compared them with theoretical evolutionary models to estimate the masses and effective temperatures. For the primary, we determined a luminosity of log ({{L}bol}/{{L}⊙ })=-3.14 ± 0.10, and inferred a mass of 73-15+20 MJup at the boundary between stars and brown dwarfs and an effective temperature of 2620 ± 140 K. For the companion we obtained a luminosity of log ({{L}bol}/{{L}⊙ })=-5.05+/- 0.22 and

  16. Searching for Pulsations from a Helium White Dwarf Companion to a Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

    Bildsten, Lars

    2009-07-01

    The low mass white dwarf {WD} companion to the 3.26 ms pulsar PSR J1911-5958A offers an unprecedented opportunity for seismological study of the interior of a helium core WD. While much more massive carbon/oxygen core WDs are observed to pulsate in normal modes of oscillation called g-modes {known as ZZ Ceti stars}, no helium core pulsator is known. By extrapolating the boundaries of the ZZ Ceti instability strip downward in surface gravity by a factor of 20 below any known pulsator, we find that the effective temperature of this WD makes it an excellent candidate to search for pulsation. Detection of g-mode pulsations in the lightcurve would have a transformative effect on the field of WD pulsations, as this would allow the first seismological study of the interior of a helium core WD, and the low gravity strongly constrains theories for the driving and amplitudes of pulsations. We show that with 3 orbits of HST, we will detect photometric variations with amplitudes of 1%, lower than typically seen in other hydrogen-dominated ZZ Ceti stars. A set of measured mode periods would also constrain the thickness of the presumed stably hydrogen burning shell, and help us determine its age more securely.

  17. A 1.05 M{sub ☉} companion to PSR J2222–0137: The coolest known white dwarf?

    SciTech Connect

    Kaplan, David L.; Boyles, Jason; McLaughlin, Maura A.; Lorimer, Duncan R.; Dunlap, Bart H.; Tendulkar, Shriharsh P.; Deller, Adam T.; Ransom, Scott M.; Stairs, Ingrid H.

    2014-07-10

    The recycled pulsar PSR J2222–0137 is one of the closest known neutron stars (NSs) with a parallax distance of 267{sub −0.9}{sup +1.2} pc and an edge-on orbit. We measure the Shapiro delay in the system through pulsar timing with the Green Bank Telescope, deriving a low pulsar mass (1.20 ± 0.14 M{sub ☉}) and a high companion mass (1.05 ± 0.06 M{sub ☉}) consistent with either a low-mass NS or a high-mass white dwarf. We can largely reject the NS hypothesis on the basis of the system's extremely low eccentricity (3 × 10{sup –4})—too low to have been the product of two supernovae under normal circumstances. However, despite deep optical and near-infrared searches with Southern Astrophysical Research and the Keck telescopes we have not discovered the optical counterpart of the system. This is consistent with the white dwarf hypothesis only if the effective temperature is <3000 K, a limit that is robust to distance, mass, and atmosphere uncertainties. This would make the companion to PSR J2222–0137 one of the coolest white dwarfs ever observed. For the implied age to be consistent with the age of the Milky Way requires the white dwarf to have already crystallized and entered the faster Debye-cooling regime.

  18. A 1.05 M ⊙ Companion to PSR J2222-0137: The Coolest Known White Dwarf?

    NASA Astrophysics Data System (ADS)

    Kaplan, David L.; Boyles, Jason; Dunlap, Bart H.; Tendulkar, Shriharsh P.; Deller, Adam T.; Ransom, Scott M.; McLaughlin, Maura A.; Lorimer, Duncan R.; Stairs, Ingrid H.

    2014-07-01

    The recycled pulsar PSR J2222-0137 is one of the closest known neutron stars (NSs) with a parallax distance of 267_{-0.9}^{+1.2} pc and an edge-on orbit. We measure the Shapiro delay in the system through pulsar timing with the Green Bank Telescope, deriving a low pulsar mass (1.20 ± 0.14 M ⊙) and a high companion mass (1.05 ± 0.06 M ⊙) consistent with either a low-mass NS or a high-mass white dwarf. We can largely reject the NS hypothesis on the basis of the system's extremely low eccentricity (3 × 10-4)—too low to have been the product of two supernovae under normal circumstances. However, despite deep optical and near-infrared searches with Southern Astrophysical Research and the Keck telescopes we have not discovered the optical counterpart of the system. This is consistent with the white dwarf hypothesis only if the effective temperature is <3000 K, a limit that is robust to distance, mass, and atmosphere uncertainties. This would make the companion to PSR J2222-0137 one of the coolest white dwarfs ever observed. For the implied age to be consistent with the age of the Milky Way requires the white dwarf to have already crystallized and entered the faster Debye-cooling regime.

  19. Be stars with white dwarf companions: a new single degenerate binary channel to type Ia supernovae explosions

    NASA Astrophysics Data System (ADS)

    Orio, Marina; Luna, Gerardo; Zemko, Polina; Kotulla, Ralf; Gallagher, Jay; Harbeck, Daniel

    2016-07-01

    A handful of supersoft X-ray sources in the Magellanic Clouds that could not be identified with transient nova outbursts turned out to be mainly massive close binaries. 6 years ago we suggested that several such sources may exist in M31, because we found that a certain fraction of supersoft sources was located in star forming regions. Following that discovery, we clearly identified a Be binary in M31, and are currently collecting data for another candidate in that galaxy. Work is in progress to assess whether the compact object companion really is a hydrogen burning white dwarf (the alternative being a massive stellar-mass black hole). If we can demonstrate that Be+white dwarf interacting close binaries are common, and that hydrogen is often ignited on the white dwarf in these systems, we have discovered a new promising channel towards the explosion of supernovae of type Ia in star forming regions, without invoking double degenerate systems.

  20. A search for companions to nearby brown dwarfs: the binary DENIS-P J1228.2-1547

    PubMed

    Martin; Brandner; Basri

    1999-03-12

    Hubble Space Telescope imaging observations of two nearby brown dwarfs, DENIS-P J1228.2-1547 and Kelu 1, made with the near-infrared camera and multiobject spectrometer (NICMOS), show that the DENIS object is resolved into two components of nearly equal brightness with a projected separation of 0.275 arc second (5 astronomical units for a distance of 18 parsecs). This binary system will be able to provide the first dynamical measurement of the masses of two brown dwarfs in only a few years. Upper limits to the mass of any unseen companion in Kelu 1 yield a planet of 7 Jupiter masses aged 0. 5 x 10(9) years, which would have been detected at a separation larger than about 4 astronomical units. This example demonstrates that giant planets could be detected by direct imaging if they exist in Jupiter-like orbits around nearby young brown dwarfs. PMID:10073933

  1. The Temperature and Cooling Age of the White Dwarf Companion to the Millisecond Pulsar PSR B1855+09.

    PubMed

    van Kerkwijk MH; Bell; Kaspi; Kulkarni

    2000-02-10

    We report on Keck and Hubble Space Telescope observations of the binary millisecond pulsar PSR B1855+09. We detect its white dwarf companion and measure mF555W=25.90+/-0.12 and mF814W=24.19+/-0.11 (Vega system). From the reddening-corrected color, (mF555W-mF814W&parr0;0=1.06+/-0.21, we infer a temperature Teff=4800+/-800 K. The white dwarf mass is known accurately from measurements of the Shapiro delay of the pulsar signal, MC=0.258+0.028-0.016 M middle dot in circle. Hence, given a cooling model, one can use the measured temperature to determine the cooling age. The main uncertainty in the cooling models for such low-mass white dwarfs is the amount of residual nuclear burning, which is set by the thickness of the hydrogen layer surrounding the helium core. From the properties of similar systems, it has been inferred that helium white dwarfs form with thick hydrogen layers, with mass greater, similar3x10-3 M middle dot in circle, which leads to significant additional heating. This is consistent with expectations from simple evolutionary models of the preceding binary evolution. For PSR B1855+09, though, such models lead to a cooling age of approximately 10 Gyr, which is twice the spin-down age of the pulsar. It could be that the spin-down age were incorrect, which would call the standard vacuum dipole braking model into question. For two other pulsar companions, however, ages well over 10 Gyr are inferred, indicating that the problem may lie with the cooling models. There is no age discrepancy for models in which the white dwarfs are formed with thinner hydrogen layers ( less, similar3x10-4 M middle dot in circle). PMID:10642200

  2. ASYMMETRIC TRANSIT CURVES AS INDICATION OF ORBITAL OBLIQUITY: CLUES FROM THE LATE-TYPE DWARF COMPANION IN KOI-13

    SciTech Connect

    Szabo, Gy. M.; Szabo, R.; Benko, J. M.; Mezo, Gy.; Simon, A. E.; Kovari, Zs.; Hodosan, G.; Regaly, Zs.; Kiss, L. L.; Lehmann, H.

    2011-07-20

    KOI-13.01, a planet-sized companion in an optical double star, was announced as one of the 1235 Kepler planet candidates in 2011 February. The transit curves show significant distortion that was stable over the {approx}130 days time span of the data. Here we investigate the phenomenon via detailed analyses of the two components of the double star and a re-reduction of the Kepler data with pixel-level photometry. Our results indicate that KOI-13 is a common proper motion binary, with two rapidly rotating components (vsin i {approx} 65-70 km s{sup -1}). We identify the host star of KOI-13.01 and conclude that the transit curve asymmetry is consistent with a companion orbiting a rapidly rotating, possibly elongated star on an oblique orbit. The radius of the transiter is 2.2 R{sub J} , implying an irradiated late-type dwarf, probably a hot brown dwarf rather than a planet. KOI-13 is the first example for detecting orbital obliquity for a substellar companion without measuring the Rossiter-McLaughlin effect with spectroscopy.

  3. A HIGHLY INCLINED ORBIT FOR THE 110 DAY PERIOD M-DWARF COMPANION KOI-368.01

    SciTech Connect

    Zhou, George; Huang, Chelsea X.

    2013-10-20

    We report the detection of asymmetry in the transit light curves of the 110 day period companion to KOI-368, a rapidly rotating A-dwarf. The significant distortion in the transit light curve is attributed to spin-orbit misalignment between the transiting companion and the gravity darkened host star. Our analysis was based on 11 long cadence and 2 short cadence transits of KOI-368.01 from the Kepler mission, as well as stellar parameters determined from our follow-up spectroscopic observation. We measured the true obliquity between the orbit normal and the stellar rotation axis to be 69{sub -10}{sup +9o}. We also find a secondary eclipse event with depth 29 ± 3 ppm at phase 0.59, from which the temperature of the companion is constrained to 3060 ± 50 K, indicating that KOI-368.01 is a late M-dwarf. The eccentricity is also calculated from the eclipse to be 0.1429 ± 0.0007. The long period, high obliquity, and low eccentricity of KOI-368.01 allow us to limit a number of proposed theories for the misalignment of binary systems.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  5. Discovery of a companion at the brown dwarf limit to the solar-type star Gliese 29

    NASA Astrophysics Data System (ADS)

    Chini, R.; Fuhrmann, K.; Pozo Nuñez, F.; Ramolla, M.; Kaderhandt, L.; Niedworok, N.; Hodapp, K.-W.

    2016-07-01

    Gliese 29 is a 7 to 8 Gyr old, southern Population I turnoff star with a large proper motion of 1 arcsec/yr. Using recent direct imaging observations with the 0.8 m Infrared Imaging System (IRIS) of the Universitätssternwarte Bochum near Cerro Armazones in Chile, we demonstrate that the faint source 2MASS J00402651-5927168 at a projected angular separation ρ=6.35 arcsec is a common-proper-motion companion to Gl 29. Provided this source is not part of a further subsystem, the IRIS J- and K_s-band photometry either implies a spectral type of about L2, based on its absolute magnitude, or an approximate mass M_B ≃ 0.077 M⊙, suggesting that it may even be a brown dwarf. Assuming a face-on circular orbit this faint companion orbits Gl 29 in 1880 years.

  6. QATAR-2: A K DWARF ORBITED BY A TRANSITING HOT JUPITER AND A MORE MASSIVE COMPANION IN AN OUTER ORBIT

    SciTech Connect

    Bryan, Marta L.; Alsubai, Khalid A.; Latham, David W.; Quinn, Samuel N.; Carter, Joshua A.; Berlind, Perry; Brown, Warren R.; Calkins, Michael L.; Esquerdo, Gilbert A.; Furesz, Gabor; Stefanik, Robert P.; Torres, Guillermo; Parley, Neil R.; Collier Cameron, Andrew; Horne, Keith D.; Fulton, Benjamin J.; Street, Rachel A.; Buchhave, Lars A.; Jorgensen, Uffe Grae; West, Richard G.; and others

    2012-05-01

    We report the discovery and initial characterization of Qatar-2b, a hot Jupiter transiting a V = 13.3 mag K dwarf in a circular orbit with a short period, P{sub b} = 1.34 days. The mass and radius of Qatar-2b are M{sub P} = 2.49 M{sub J} and R{sub P} = 1.14 R{sub J}, respectively. Radial-velocity monitoring of Qatar-2 over a span of 153 days revealed the presence of a second companion in an outer orbit. The Systemic Console yielded plausible orbits for the outer companion, with periods on the order of a year and a companion mass of at least several M{sub J}. Thus, Qatar-2 joins the short but growing list of systems with a transiting hot Jupiter and an outer companion with a much longer period. This system architecture is in sharp contrast to that found by Kepler for multi-transiting systems, which are dominated by objects smaller than Neptune, usually with tightly spaced orbits that must be nearly coplanar.

  7. An M Dwarf Companion to an F-type Star in a Young Main-sequence Binary

    NASA Astrophysics Data System (ADS)

    Eigmüller, Ph.; Eislöffel, J.; Csizmadia, Sz.; Lehmann, H.; Erikson, A.; Fridlund, M.; Hartmann, M.; Hatzes, A.; Pasternacki, Th.; Rauer, H.; Tkachenko, A.; Voss, H.

    2016-03-01

    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⊙ and a radius of (1.474 ± 0.040) R⊙. The companion is an M dwarf with a mass of (0.188 ± 0.014) M⊙ and a radius of (0.234 ± 0.009) R⊙. 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.

  8. A search for companions to brown dwarfs in the Taurus and Chamaeleon star-forming regions

    SciTech Connect

    Todorov, K. O.; Luhman, K. L.; Konopacky, Q. M.; McLeod, K. K.; Apai, D.; Pascucci, I.; Ghez, A. M.; Robberto, M.

    2014-06-10

    We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M ∼ 0.01-0.1 M {sub ☉}). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 (ρ = 0.''105/15 AU), 2MASS J04221332+1934392 (ρ = 0.''05/7 AU), and ISO 217 (ρ = 0.''03/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco (τ ∼ 10 Myr), we measure binary fractions of 14/93 = 0.15{sub −0.03}{sup +0.05} for M4-M6 (M ∼ 0.1-0.3 M {sub ☉}) and 4/108 = 0.04{sub −0.01}{sup +0.03} for >M6 (M ≲ 0.1 M {sub ☉}) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming.

  9. Discovery of four new low-mass white-dwarf companions in the Kepler data

    NASA Astrophysics Data System (ADS)

    Faigler, Simchon; Kull, Ilya; Mazeh, Tsevi; Kiefer, Flavien; Latham, David W.; Bloemen, Steven

    2015-12-01

    We report the discovery of four new short-period eclipsing systems in the Kepler light curves, consisting of an A-star primary and a low-mass white-dwarf (WD) secondary (dA+WD) - KIC 4169521, KOI-3818, KIC 2851474 and KIC 9285587. These add to the 6 Kepler, and 19 non-Kepler, previously known short-period eclipsing dA+WD binaries.The discoveries were made through searching the light curves of bright Kepler stars for BEaming, Ellipsoidal and Reflection (BEER) modulations that are consistent with a compact companion, using the BEER search algorithm. This was followed by inspection of the search top hits, looking for eclipsing systems with a secondary eclipse deeper than the primary one, as expected for a WD that is hotter than the primary star. Follow-up spectroscopic radial-velocity (RV) observations confirmed the binarity of the systems. We derive the systems' parameters through analyses of the light curves' eclipses and phase modulations, combined with RV orbital solutions and stellar evolution models.The four systems' orbital periods of 1.17-3.82 days and WD masses of 0.19-0.22 Msun are similar to those reported for the previously known systems. These values are consistent with evolution models of such systems, that undergo a stable mass transfer from the WD progenitor to the current A star.For KIC 4169521 we derive a bloated WD radius of 0.09 Rsun that is well within the WD radius range of 0.04-0.43 Rsun of the known systems. For the remaining three systems we report WD radii of 0.026-0.035 Rsun, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries.As suggested before, the previously known systems, together with KIC 4169521, all with hot and bloated WD secondaries, represent young systems probably at a proto-WD, or initial WD cooling track stage. The other three new systems - KOI-3818, KIC 2851474, and KIC 9285587, are probably positioned further along the WD cooling track, and extend the known population to older systems with cooler

  10. A Search for Companions to Brown Dwarfs in the Taurus and Chamaeleon Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Todorov, K. O.; Luhman, K. L.; Konopacky, Q. M.; McLeod, K. K.; Apai, D.; Ghez, A. M.; Pascucci, I.; Robberto, M.

    2014-06-01

    We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M ~ 0.01-0.1 M ⊙). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 (ρ = 0.''105/15 AU), 2MASS J04221332+1934392 (ρ = 0.''05/7 AU), and ISO 217 (ρ = 0.''03/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco (τ ~ 10 Myr), we measure binary fractions of 14/93 = 0.15^{+0.05}_{-0.03} for M4-M6 (M ~ 0.1-0.3 M ⊙) and 4/108 = 0.04^{+0.03}_{-0.01} for >M6 (M <~ 0.1 M ⊙) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming. Based on observations performed with the NASA/ESA Hubble Space Telescope, Gemini Observatory, and the W. M. Keck Observatory. The Hubble observations are associated with proposal IDs 11203, 11204, and 11983 and were 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.

  11. Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: nine confirmed planets and two confirmed brown dwarfs

    NASA Astrophysics Data System (ADS)

    Reffert, S.; Quirrenbach, A.

    2011-03-01

    Context. The recently completed re-reduction of the Hipparcos data by van Leeuwen (2007a, Astrophysics and Space Science Library, 350) makes it possible to search for the astrometric signatures of planets and brown dwarfs known from radial velocity surveys in the improved Hipparcos intermediate astrometric data. Aims: Our aim is to put more significant constraints on the orbital parameters which cannot be derived from radial velocities alone, i.e. the inclination and the longitude of the ascending node, than was possible before. The determination of the inclination in particular allows to calculate an unambiguous companion mass, rather than the lower mass limit which can be obtained from radial velocity measurements. Methods: We fitted the astrometric orbits of 310 substellar companions around 258 stars, which were all discovered via the radial velocity method, to the Hipparcos intermediate astrometric data provided by van Leeuwen. Results: Even though the astrometric signatures of the companions cannot be detected in most cases, the Hipparcos data still provide lower limits on the inclination for all but 67 of the investigated companions, which translates into upper limits on the masses of the unseen companions. For nine companions the derived upper mass limit lies in the planetary and for 75 companions in the brown dwarf mass regime, proving the substellar nature of those objects. Two of those objects have minimum masses also in the brown dwarf regime and are thus proven to be brown dwarfs. The confirmed planets are the ones around Pollux (β Gem b), ɛ Eri b, ɛ Ret b, μ Ara b, υ And c and d, 47 UMa b, HD 10647 b and HD 147513 b. The confirmed brown dwarfs are HD 137510 b and HD 168443 c. In 20 cases, the astrometric signature of the substellar companion was detected in the Hipparcos data, resulting in reasonable constraints on inclination and ascending node. Of these 20 companions, three are confirmed as planets or lightweight brown dwarfs (HD 87833 b, ι Dra

  12. Astrometric follow-up observations of directly imaged sub-stellar companions to young stars and brown dwarfs

    NASA Astrophysics Data System (ADS)

    Ginski, C.; Schmidt, T. O. B.; Mugrauer, M.; Neuhäuser, R.; Vogt, N.; Errmann, R.; Berndt, A.

    2014-11-01

    The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios, we search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose, we utilized VLT/NACO to take several well-calibrated high-resolution images of six target systems and analyse them together with available literature data points of those systems as well as Hubble Space Telescope archival data. We used a statistical least-squares Monte Carlo approach to constrain the orbit elements of all systems that showed significant differential motion of the primary star and companion. We show for the first time that the GQ Lup system shows significant change in both separation and position angle. Our analysis yields best-fitting orbits for this system, which are eccentric (e between 0.21 and 0.69), but cannot rule out circular orbits at high inclinations. Given our astrometry, we discuss formation scenarios of the GQ Lup system. In addition, we detected an even fainter new companion candidate to GQ Lup, which is most likely a background object. We also updated the orbit constraints of the PZ Tel system, confirming that the companion is on a highly eccentric orbit with e > 0.62. Finally, we show with a high significance, that there is no orbital motion observed in the cases of the DH Tau, HD 203030 and 1RXS J160929.1-210524 systems, and give the most precise relative astrometric measurement of the UScoCTIO 108 system to date.

  13. LHS 2803B: A VERY WIDE MID-T DWARF COMPANION TO AN OLD M DWARF IDENTIFIED FROM PAN-STARRS1

    SciTech Connect

    Deacon, Niall R.; Liu, Michael C.; Magnier, Eugene A.; Bowler, Brendan P.; Mann, Andrew W.; Burgett, William S.; Chambers, Ken C.; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S.; Tonry, John L.; Wainscoat, Richard J.; Redstone, Joshua A.; Hodapp, Klaus W.; Price, Paul A.

    2012-09-20

    We report the discovery of a wide ({approx}1400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 and Two Micron All Sky Survey data. Using the Infrared Telescope Facility/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawaii 2.2 m/SuperNova Integral Field Spectrograph optical spectroscopy indicates that the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable H{alpha} emission. We use this lack of activity to set a lower age limit for the system of 3.5 Gyr. Using a comparison with chance alignments of brown dwarfs and nearby stars, we conclude that the two objects are unlikely to be a chance association. The primary's photometric distance of 21 pc and its proper motion implies thin disk kinematics. Based on these kinematics and its metallicity, we set an upper age limit for the system of 10 Gyr. Evolutionary model calculations suggest that the secondary has a mass of 72{+-}{sup 4}{sub 7} M{sub Jup}, temperature of 1120 {+-} 80 K, and log g = 5.4 {+-} 0.1 dex. Model atmosphere fitting to the near-IR spectrum gives similar physical parameters of 1100 K and log g = 5.0.

  14. A subsynchronously rotating pulsating subdwarf B star in a short-period binary with a white dwarf companion

    NASA Astrophysics Data System (ADS)

    Baran, A. S.; Telting, J. H.; Németh, P.; Østensen, R. H.; Reed, M. D.; Kiaeerad, F.

    2016-01-01

    We present our analysis of KIC 7664467, an sdB pulsator that we have found to be residing in a 1.56-day binary system with a white-dwarf companion. This system was observed photometrically with the Kepler spacecraft and spectroscopically with ground-based telescopes. We analyzed the amplitude spectra detecting 61 periods, rotationally split multiplets, and an equally spaced sequence in period. These two features helped with the mode identification. We derived both the binary and rotation periods showing that this is another binary system with a subsynchronous sdB star. From our spectroscopy of the sdB star, we determined Teff = 27440 ± 120 K, log g = 5.38 ± 0.02 dex. The abundance pattern follows the general trend observed in sdB stars, where light metals are subsolar, while the Fe abundance is very close to the solar value. We found the N enrichment and low abundances of C and O that resemble the equilibrium abundances of the CNO cycle. We could also measure the Mg and Si abundances. Using the radial velocity amplitude K1 = 57(3) km s-1 and the Doppler boosting-dominated photometric signal at the orbital period, we constrained the companion to be a compact object, almost certainly a white dwarf.

  15. SDSS J001641-000925: THE FIRST STABLE RED DWARF CONTACT BINARY WITH A CLOSE-IN STELLAR COMPANION

    SciTech Connect

    Qian, S.-B.; Jiang, L.-Q.; Zhu, L.-Y.; Zhao, E. G.; He, J.-J.; Liao, W.-P.; Wang, J.-J.; Liu, L.; Zhou, X.; Liu, N. P.; Fernández Lajús, E.; Soonthornthum, B.; Rattanasoon, S.; Aukkaravittayapun, S.

    2015-01-10

    SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of P-dot ∼8 s yr{sup −1}. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O–C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M {sub 3}sin i' ∼ 0.14 M {sub ☉}. The orbital separation between the third body and the central binary is about 2.8 AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary.

  16. SDSS J001641-000925: The First Stable Red Dwarf Contact Binary with a Close-in Stellar Companion

    NASA Astrophysics Data System (ADS)

    Qian, S.-B.; Jiang, L.-Q.; Fernández Lajús, E.; Soonthornthum, B.; Zhu, L.-Y.; Zhao, E. G.; He, J.-J.; Liao, W.-P.; Wang, J.-J.; Liu, L.; Rattanasoon, S.; Aukkaravittayapun, S.; Zhou, X.; Liu, N. P.

    2015-01-01

    SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of \\dot{P}˜ {8} s yr-1. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O-C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M 3sin i' ~ 0.14 M ⊙. The orbital separation between the third body and the central binary is about 2.8 AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary.

  17. The Brown Dwarf Kinematics Project. II. Details on Nine Wide Common Proper Motion Very Low Mass Companions to Nearby Stars

    NASA Astrophysics Data System (ADS)

    Faherty, Jacqueline K.; Burgasser, Adam J.; West, Andrew A.; Bochanski, John J.; Cruz, Kelle L.; Shara, Michael M.; Walter, Frederick M.

    2010-01-01

    We report on nine wide common proper motion systems containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new systems. The ages of these systems are determined using diagnostics for both stellar primaries and low-mass secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of ~25,000 AU making it one of the widest and lowest binding energy systems known to date. The system containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows Hα activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. Two of the nine systems have discrepant component ages that emerge from stellar or ultracool diagnostics indicating possible shortcomings in our understanding of the age diagnostics of stars and brown dwarfs. We find a resolved binary frequency for widely separated (>100 AU) low-mass companions (i.e., at least a triple system) which is at least twice the frequency found for the field ultracool dwarf population. The ratio of triples to binaries and quadruples to binaries is also high for this sample: 3:5 and 1:4, respectively, compared to 8 pc sample values of 1:4 and 1:26. The additional components in these wide companion systems indicates a formation mechanism that requires a third or fourth component to maintain gravitational stability or facilitate the exchange of angular momentum. The binding energies for the nine multiples discussed in this text are among the lowest known for wide low-mass systems, suggesting that weakly bound, low-to-intermediate mass (0.2 M sun < M tot< 1.0 M sun) multiples can form and survive to exist in the field (1-8 Gyr). This paper includes data

  18. THE BROWN DWARF KINEMATICS PROJECT. II. DETAILS ON NINE WIDE COMMON PROPER MOTION VERY LOW MASS COMPANIONS TO NEARBY STARS ,

    SciTech Connect

    Faherty, Jacqueline K.; Shara, Michael M.; Burgasser, Adam J.; West, Andrew A.; Bochanski, John J.; Cruz, Kelle L.; Walter, Frederick M.

    2010-01-15

    We report on nine wide common proper motion systems containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new systems. The ages of these systems are determined using diagnostics for both stellar primaries and low-mass secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of {approx}25,000 AU making it one of the widest and lowest binding energy systems known to date. The system containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows H{alpha} activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. Two of the nine systems have discrepant component ages that emerge from stellar or ultracool diagnostics indicating possible shortcomings in our understanding of the age diagnostics of stars and brown dwarfs. We find a resolved binary frequency for widely separated (>100 AU) low-mass companions (i.e., at least a triple system) which is at least twice the frequency found for the field ultracool dwarf population. The ratio of triples to binaries and quadruples to binaries is also high for this sample: 3:5 and 1:4, respectively, compared to 8 pc sample values of 1:4 and 1:26. The additional components in these wide companion systems indicates a formation mechanism that requires a third or fourth component to maintain gravitational stability or facilitate the exchange of angular momentum. The binding energies for the nine multiples discussed in this text are among the lowest known for wide low-mass systems, suggesting that weakly bound, low-to-intermediate mass (0.2 M {sub sun} < M {sub tot}< 1.0 M {sub sun}) multiples can form and survive to exist in the field (1-8 Gyr)

  19. A CLOSE COMPANION SEARCH AROUND L DWARFS USING APERTURE MASKING INTERFEROMETRY AND PALOMAR LASER GUIDE STAR ADAPTIVE OPTICS

    SciTech Connect

    Bernat, David; Bouchez, Antonin H.; Cromer, John L.; Dekany, Richard G.; Moore, Anna M.; Ireland, Michael; Tuthill, Peter; Martinache, Frantz; Angione, John; Burruss, Rick S.; Guiwits, Stephen R.; Henning, John R.; Hickey, Jeff; Kibblewhite, Edward; McKenna, Daniel L.; Petrie, Harold L.; Roberts, Jennifer; Shelton, J. Chris; Thicksten, Robert P.; Trinh, Thang

    2010-06-01

    We present a close companion search around 16 known early L dwarfs using aperture masking interferometry with Palomar laser guide star adaptive optics (LGS AO). The use of aperture masking allows the detection of close binaries, corresponding to projected physical separations of 0.6-10.0 AU for the targets of our survey. This survey achieved median contrast limits of {Delta}K {approx} 2.3 for separations between 1.2 {lambda}/D-4{lambda}/D and {Delta}K {approx} 1.4 at 2/3 {lambda}/D. We present four candidate binaries detected with moderate-to-high confidence (90%-98%). Two have projected physical separations less than 1.5 AU. This may indicate that tight-separation binaries contribute more significantly to the binary fraction than currently assumed, consistent with spectroscopic and photometric overluminosity studies. Ten targets of this survey have previously been observed with the Hubble Space Telescope as part of companion searches. We use the increased resolution of aperture masking to search for close or dim companions that would be obscured by full aperture imaging, finding two candidate binaries. This survey is the first application of aperture masking with LGS AO at Palomar. Several new techniques for the analysis of aperture masking data in the low signal-to-noise regime are explored.

  20. A Young Planetary Mass Companion to the Nearby M Dwarf VHS J125601.92-125723.9

    NASA Astrophysics Data System (ADS)

    Gauza, B.; Béjar, V. J. S.; Pérez-Garrido, A.; Osorio, M. R. Zapatero; Lodieu, N.; Rebolo, R.; Pallé, E.; Nowak, G.

    2016-01-01

    We have recently identified a young, very red (J - Ks = 2.47 mag) late L-type companion at 8.06'' +/- 0.03'' (~102 AU) from a previously unrecognized M dwarf. We determined the parallactic distance of the system to be 12.7+/-1.0 pc. Non-detection of lithium and the kinematics of the primary allowed us to constrain the age of the system in the range of 150-300 Myr. By comparison with theoretical evolutionary models we derived a mass of 73+20 -15 M Jup for the primary, at around the substellar mass regime and 11.2+9.7 -1.8 M Jup for the secondary, near the deuterium burning mass limit.

  1. Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System

    NASA Astrophysics Data System (ADS)

    Stone, Jordan M.; Skemer, Andrew J.; Kratter, Kaitlin M.; Dupuy, Trent J.; Close, Laird M.; Eisner, Josh A.; Fortney, Jonathan J.; Hinz, Philip M.; Males, Jared R.; Morley, Caroline V.; Morzinski, Katie M.; Ward-Duong, Kimberly

    2016-02-01

    Recently, Gauza et al. reported the discovery of a companion to the late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion’s absolute photometry suggests its mass and atmosphere are similar to the HR 8799 planets. However, as a wide companion to a late-type star, it is more accessible to spectroscopic characterization. We discovered that the primary of this system is an equal-magnitude binary. For an age ˜300 Myr the A and B components each have a mass of {64.6}-2.0+0.8 {M}{Jup}, and the b component has a mass of {11.2}-1.8+9.7, making VHS 1256-1257 only the third brown dwarf triple system. There exists some tension between the spectrophotometric distance of 17.2 ± 2.6 pc and the parallax distance of 12.7 ± 1.0 pc. At 12.7 pc VHS 1256-1257 A and B would be the faintest known M7.5 objects, and are even faint outliers among M8 types. If the larger spectrophotmetric distance is more accurate than the parallax, then the mass of each component increases. In particular, the mass of the b component increases well above the deuterium burning limit to ˜ 35 {M}{Jup} and the mass of each binary component increases to {73}-17+20 {M}{Jup}. At 17.1 pc, the UVW kinematics of the system are consistent with membership in the AB Dor moving group. The architecture of the system resembles a hierarchical stellar multiple suggesting it formed via an extension of the star formation process to low masses. Continued astrometric monitoring will resolve this distance uncertainty and will provide dynamical masses for a new benchmark system.

  2. A white dwarf companion to the main-sequence star 4 Omicron(1) Orionis and the binary hypothesis for the origin of peculiar red giants

    NASA Astrophysics Data System (ADS)

    Ake, Thomas B.; Johnson, Hollis R.

    1988-04-01

    In the course of an investigation with the IUE satellite of the ultraviolet spectra of peculiar red giants, the authors have discovered a white dwarf companion to the MS star 4 ο1Ori. They discuss the reductions performed for the ο1Ori IUE observations, and compare these with field white dwarfs to derive parameters of the white dwarf and the luminosity of the primary. Upper detection limits are derived for hot degenerate companions to four other bright MS stars, HR 363, RS Cnc, ST Her, and OP Her. Combined with the ο1Ori observations, it is argued that the nondetections for these stars are consistent with the statistics of field giant binaries and that either mass-transfer effects are not responsible for the incipient S-star nature of the MS stars, if their abundance peculiarities are recent, or that the MS stars must be older than 106yr.

  3. High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758

    NASA Technical Reports Server (NTRS)

    Currie, Thayne; Bailey, Vanessa; Fabrycky, Daniel; Murray-Clay, Ruth; Rodigas, Timothy; Hinz, Phil

    2010-01-01

    We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one -- possibly two-- faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \\textit(possible) detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 758B has a H-L'color redder than nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx. 10-20 Mj if it is approx. 1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 758B is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

  4. High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758

    NASA Technical Reports Server (NTRS)

    Currie, Thayne M.; Bailey, Vanessa; Fabrycky, Daniel; Murray-Clay, Ruth; Rodigas, Timothy; Hinz, Phil

    2011-01-01

    We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one - possibly two - faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \\textit{possible} detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 7588 has a H-L' color redder than nearly all known L-T8 dwarfs. 8ased on comparisons with the COND evolutionary models, GJ 7588 has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx.10-20 Mj if it is approx.1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 7588 is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 7588 is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

  5. EVOLUTION OF THE SYMBIOTIC NOVA PU VUL-OUTBURSTING WHITE DWARF, NEBULAE, AND PULSATING RED GIANT COMPANION

    SciTech Connect

    Kato, Mariko; Mikolajewska, Joanna; Hachisu, Izumi

    2012-05-01

    We present a composite light-curve model of the symbiotic nova PU Vul (Nova Vulpeculae 1979) that shows a long-lasting flat optical peak followed by a slow decline. Our model light curve consists of three components of emission, i.e., an outbursting white dwarf (WD), its M-giant companion, and the nebulae. The WD component dominates in the flat peak while the nebulae dominate after the photospheric temperature of the WD rises to log T (K) {approx}> 4.5, suggesting its WD origin. We analyze the 1980 and 1994 eclipses to be total eclipses of the WD occulted by the pulsating M-giant companion with two sources of the nebular emission; one is an unocculted nebula of the M-giant's cool-wind origin and the other is a partially occulted nebula associated to the WD. We confirmed our theoretical outburst model of PU Vul by new observational estimates, which spanned 32 yr, of the temperature and radius. Also our eclipse analysis confirmed that the WD photosphere decreased by two orders of magnitude between the 1980 and 1994 eclipses. We obtain the reddening E(B - V) {approx} 0.3 and distance to PU Vul d {approx} 4.7 kpc. We interpret the recent recovery of brightness in terms of eclipse of the hot nebula surrounding the WD, suggesting that hydrogen burning is ongoing. To detect supersoft X-rays, we recommend X-ray observations around 2014 June when absorption by neutral hydrogen is minimum.

  6. THE FIRST VLBI DETECTION OF AN ULTRACOOL DWARF: IMPLICATIONS FOR THE DETECTABILITY OF SUB-STELLAR COMPANIONS

    SciTech Connect

    Forbrich, Jan; Berger, Edo

    2009-12-01

    We present milliarcsecond-resolution radio very long baseline interferometry (VLBI) observations of the ultracool dwarfs TVLM 513-46546 (M8.5) and 2MASS J00361617+1821104 (L3.5) in an attempt to detect sub-stellar companions via direct imaging or reflex motion. Both objects are known radio emitters with strong evidence for periodic emission on timescales of about 2 hr and 3 hr, respectively. Using the inner seven VLBA antennas, we detect unresolved emission from TVLM 513-46546 on a scale of 2.5 mas (approx50 stellar radii), leading to a direct limit on the radio emission brightness temperature of T{sub B} approx> 4 x 10{sup 5} K. However, with the higher spatial resolution afforded by the full VLBA we find that the source appears to be marginally resolved at a low signal-to-noise ratio, possibly indicating that TVLM 513-46546 is a binary with a projected separation of approx1 mas (approx20 stellar radii). Using the 7 hr baseline of our observation, we find no astrometric shift in the position of TVLM 513-46546, with a 3sigma limit of about 0.6 mas. This is about three times larger than expected for an equal-mass companion with a few-hour orbital period. Future monitoring of its position on a range of timescales will provide the required astrometric sensitivity to detect a planetary companion with a mass of approx10 M {sub J} in a approx>15 day (approx>0.06 AU) orbit, or with a mass of approx2 M {sub J} in an orbit of approx>0.5 yr (approx>0.3 AU).

  7. Constraining the Evolution of Brown Dwarf Binarity as a Function of Age: A Keck LGS AO Search for Brown Dwarf and Planetary Mass Companions to Upper Scorpius Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Biller, B.; Allers, K.; Liu, M.; Close, L. M.; Dupuy, T.

    2011-12-01

    We searched for binary companions to 20 brown dwarfs in Upper Scorpius (145 pc, 5 Myr, nearest OB association) with the facility infrared camera NIRC2 and the Laser Guide Star adaptive optics system on the 10 m Keck II telescope. We discovered a close companion (0.14″, 20.9±0.4 AU) to the very low mass object SCH J16091837-20073523. From spectral deconvolution of integrated-light near-IR spectroscopy of SCH1609 using the SpeX spectrograph (Rayner et al. 2003), we estimate primary and secondary spectral types of M6±0.5 and M7±1.0, corresponding to masses of 79±17 MJup and 55±25 MJup at an age of 5 Myr and masses of 84±15 MJup and 60±25 MJup at an age of 10 Myr. For our survey objects with spectral types later than M8, we find an upper limit on the binary fraction of <9% (1-σ) at separations greater than 10 AU. We combine the results of our survey with previous surveys of Upper Sco and similar young regions to set the strongest constraints to date on binary fraction for young substellar objects and very low mass stars. The binary fraction for low mass (<40 MJup) brown dwarfs in Upper Sco is similar to that for T dwarfs in the field; for higher mass brown dwarfs and very low mass stars, there is an excess of medium-separation (10-50 AU projected separation) young binaries with respect to the field. These medium separation binaries will likely survive to late ages.

  8. What does an erupting nova do to its red dwarf companion

    SciTech Connect

    Kovetz, A.; Prialnik, D.; Shara, M.M.

    1988-02-01

    During nova eruptions and for decades afterward, the red dwards in cataclysmic binaries are irradiated with hundreds of times more luminosity than they themselves produce. Simulations of the time-dependent irradiation of three red dwarf models (0.25, 0.50, and 0.75 solar mass) are presented. The mass transfer rates forced by irradiation after nova eruption are found to be enhanced by two orders of magnitude because of the irradiation. The time scale for irradiation to become unimportant is that of the white dwarf cooling time scale, a few centuries. These two results support the hibernation scenario of novae, which suggests that novae remain bright for a few centuries after eruption because of irradiation-induced mass transfer. After irradiation decreases mass transfer slows, and some very old novae may then become extremely faint. 26 references.

  9. Youngest Brown Dwarf Yet in a Multiple Stellar System

    NASA Astrophysics Data System (ADS)

    2000-07-01

    Silla, as well as the 8.2-m VLT/ANTU telescope with the ISAAC multi-mode instrument at Paranal. The first step is to take high-resolution images of the stars from the ROSAT list to look for possible faint companions. However, any faint object found near one of the programme stars may of course be a completely unrelated fore- or background object and it is therefore imperative to check this by means of supplementary observations. Two methods are available. The first implies taking spectra of the companion candidates that demonstrate whether they are bona-fide Brown Dwarfs that display spectral lines typical for the cool atmospheres of this class, e.g., of Titanium Oxide (TiO) and Vanadium Oxide (VO). Infrared spectra are particularly useful for a measurement of the atmospheric temperature. The other involves obtaining a second image some years later. If the companion candidate and the brighter star belong to the same stellar system, they must move together on the sky or, as astronomers say, their measured "proper motions" must be (nearly) the same. If both checks are positive, the fainter object is most likely to be a bona-fide Brown Dwarf companion to the young and nearby star. To be absolutely certain, its orbital motion should also be detected, but it will be very slow and can only be perceived after several years of continued observations. VLT observations of TWA-5 B Two years ago, a faint companion candidate was found near one of the young and nearby stars included in the present programme and designated TWA-5 (also known as CoD -33 7795 ). It is about 12 million years old and is a member of a group of about a dozen young stars (of the "T Tauri"-type ), seen in the southern constellation Hydra (the Water-Snake) and grouped around the star TW Hya , the first to be found in this area ("TWA" means the "TW Hya Association"). The HIPPARCOS mission of the European Space Agency (ESA) measured a mean distance to some of these stars of ~ 180 light-years (55 parsec). This

  10. THE SPECTRUM OF THE RECYCLED PSR J0437-4715 AND ITS WHITE DWARF COMPANION

    SciTech Connect

    Durant, Martin; Kargaltsev, Oleg; Pavlov, George G.; Posselt, Bettina; Kowalski, Piotr M.; Van Kerkwijk, Marten H.; Kaplan, David L.

    2012-02-10

    We present extensive spectral and photometric observations of the recycled pulsar/white dwarf binary containing PSR J0437-4715, which we analyzed together with archival X-ray and gamma-ray data, to obtain the complete mid-infrared to gamma-ray spectrum. We first fit each part of the spectrum separately, and then the whole multi-wavelength spectrum. We find that the optical-infrared part of the spectrum is well fit by a cool white dwarf atmosphere model with pure hydrogen composition. The model atmosphere (T{sub eff} = 3950 {+-} 150 K, log g = 6.98 {+-} 0.15, R{sub WD} = (1.9 {+-} 0.2) Multiplication-Sign 10{sup 9} cm) fits our spectral data remarkably well for the known mass and distance (M = 0.25 {+-} 0.02 M{sub Sun }, d = 156.3 {+-} 1.3 pc), yielding the white dwarf age ({tau}{sub WD} = 6.0 {+-} 0.5 Gyr). In the UV, we find a spectral shape consistent with thermal emission from the bulk of the neutron star surface, with surface temperature between 1.25 Multiplication-Sign 10{sup 5} and 3.5 Multiplication-Sign 10{sup 5} K. The temperature of the thermal spectrum suggests that some heating mechanism operates throughout the life of the neutron star. The temperature distribution on the neutron star surface is non-uniform. In the X-rays, we confirm the presence of a high-energy tail which is consistent with a continuation of the cutoff power-law component ({Gamma} = 1.56 {+-} 0.01, E{sub cut} = 1.1 {+-} 0.2 GeV) that is seen in gamma rays and perhaps even extends to the near-UV.

  11. A nearby young M dwarf with a wide, possibly planetary-mass companion

    NASA Astrophysics Data System (ADS)

    Deacon, N. R.; Schlieder, J. E.; Murphy, S. J.

    2016-04-01

    We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the ˜45 Myr old Tucana-Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708 Å absorption consistent with M dwarfs younger than TucHor but older than the ˜10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the ˜24 Myr old β Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6-15 MJ for the secondary. It is thus likely 2MASS J2126-8140 is the widest orbit planetary-mass object known (>4500 au) and its estimated mass, age, spectral type, and Teff are similar to the well-studied planet β Pictoris b. Because of their extreme separation and youth, this low-mass pair provide an interesting case study for very wide binary formation and evolution.

  12. 8. DETAIL OF NORTHEAST ELEVATION SHOWING NEON TWA SIGN AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. DETAIL OF NORTHEAST ELEVATION SHOWING NEON TWA SIGN AND ROOF MASTS. LOOKING SOUTHWEST. - TWA Maintenance Hangar, South side of Tinicum Island Road, Philadelphia International Airport, Philadelphia, Philadelphia County, PA

  13. A Statistical Study of Brown Dwarf Companions from the SDSS-III MARVELS Survey

    NASA Astrophysics Data System (ADS)

    Grieves, Nolan; Ge, Jian; Thomas, Neil; Ma, Bo; De Lee, Nathan M.; Lee, Brian L.; Fleming, Scott W.; Sithajan, Sirinrat; Varosi, Frank; Liu, Jian; Zhao, Bo; Li, Rui; Agol, Eric; MARVELS Team

    2016-01-01

    We present 23 new Brown Dwarf (BD) candidates from the Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III (SDSS-III). The BD candidates were selected from the processed MARVELS data using the latest University of Florida 2D pipeline, which shows significant improvement and reduction of systematic errors over the 1D pipeline results included in the SDSS Data Release 12. This sample is the largest BD yield from a single radial velocity survey. Of the 23 candidates, 18 are around main sequence stars and 5 are around giant stars. Given a giant contamination rate of ~24% for the MARVELS survey, we find a BD occurrence rate around main sequence stars of ~0.7%, which agrees with previous studies and confirms the BD desert, while the BD occurrence rate around the MARVELS giant stars is ~0.6%. Preliminary results show that our new candidates around solar type stars support a two population hypothesis, where BDs are divided at a mass of ~42.5 MJup. BDs less massive than 42.5 MJup have eccentricity distributions consistent with planet-planet scattering models, where BDs more massive than 42.5 MJup have both period and eccentricity distributions similar to that of stellar binaries. Special Brown Dwarf systems such as multiple BD systems and highly eccentric BDs will also be presented.

  14. A faint type of supernova from a white dwarf with a helium-rich companion.

    PubMed

    Perets, H B; Gal-Yam, A; Mazzali, P A; Arnett, D; Kagan, D; Filippenko, A V; Li, W; Arcavi, I; Cenko, S B; Fox, D B; Leonard, D C; Moon, D-S; Sand, D J; Soderberg, A M; Anderson, J P; James, P A; Foley, R J; Ganeshalingam, M; Ofek, E O; Bildsten, L; Nelemans, G; Shen, K J; Weinberg, N N; Metzger, B D; Piro, A L; Quataert, E; Kiewe, M; Poznanski, D

    2010-05-20

    Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae. Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The 'old' environment near the supernova location, and the very low derived ejected mass ( approximately 0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous or a regular type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive (44)Ti. PMID:20485429

  15. Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.

    PubMed

    Tauris; van Den Heuvel EP; Savonije

    2000-02-20

    We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or Porb approximately 1 day (e.g., PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system. PMID:10655173

  16. A faint type of supernova from a white dwarf with a helium-rich companion

    NASA Astrophysics Data System (ADS)

    Perets, H. B.; Gal-Yam, A.; Mazzali, P. A.; Arnett, D.; Kagan, D.; Filippenko, A. V.; Li, W.; Arcavi, I.; Cenko, S. B.; Fox, D. B.; Leonard, D. C.; Moon, D.-S.; Sand, D. J.; Soderberg, A. M.; Anderson, J. P.; James, P. A.; Foley, R. J.; Ganeshalingam, M.; Ofek, E. O.; Bildsten, L.; Nelemans, G.; Shen, K. J.; Weinberg, N. N.; Metzger, B. D.; Piro, A. L.; Quataert, E.; Kiewe, M.; Poznanski, D.

    2010-05-01

    Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae. Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The `old' environment near the supernova location, and the very low derived ejected mass (~0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous or a regular type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive 44Ti.

  17. High-contrast Adaptive Optics and a Search for Late-type Companions to Hyades FGK Dwarfs

    NASA Astrophysics Data System (ADS)

    Morzinski, Katie M.

    2011-01-01

    The Hyades is an intermediate-age open cluster with hundreds of main-sequence stars and is thus well-suited to stellar formation and evolution studies. Being nearby with high proper motion, it is a choice cluster for direct-imaging surveys. We conduct a high-contrast adaptive optics (AO) search for late-type companions as faint as MH 15 (late-L/early-T) within 5-230 AU around 88 FGK main-sequence Hyades dwarfs. Departures from the ideal point-spread function (PSF) in the image plane are caused by phase and amplitude errors that redistribute stellar light and limit the achievable contrast. An AO system on a ground-based telescope mitigates the phase errors in the pupil, but constructive interference of spatially coherent light causes amplitude spikes in the PSF called speckles. The locally-optimized combination of images (LOCI) algorithm is used to identify and subtract the quasistatic speckles and static PSF structure, allowing imaging of faint point-source companions. We use LOCI on deep near-infrared AO Hyad imaging at Keck and Lick Observatories. Background objects are subsequently ruled out by comparing relative astrometry in two epochs separated by five years. We present our confirmed Hyades companions. Furthermore, we look ahead to AO for exoplanet-imaging wherein a ''dark hole'' in the PSF facilitates high-contrast imaging. The size of the dark hole is set by the highest spatial frequency controllable by the deformable mirror (DM). Decreasing rejection at increasing spatial frequencies reduces the correction efficiency within the high-contrast region, owing to the nature of the MEMS (micro-electro-mechanical systems) DM transfer function. This effect can be mitigated by a dual-DM ''woofer/tweeter'' AO system whereby each DM controls a different spatial frequency regime. We present empirical results on selecting a woofer DM in order to maintain the dark hole for the upcoming Gemini Planet Imager. (Supported by NASA Michelson Fellowship, NSF Center for

  18. Near-infrared integral-field spectra of the planet/brown dwarf companion AB Pictoris b

    NASA Astrophysics Data System (ADS)

    Bonnefoy, M.; Chauvin, G.; Rojo, P.; Allard, F.; Lagrange, A.-M.; Homeier, D.; Dumas, C.; Beuzit, J.-L.

    2010-03-01

    Context. We have already imaged a co-moving companion at a projected separation of ~260 AU from the young star AB Pic A. Evolutionary model predictions based on JHK photometry of AB Pic b suggest a mass of ~13-14 MJup, placing the object at the deuterium-burning boundary. Aims: We aim to determine the spectral type, the surface gravity, and the effective temperature of AB Pic b. From the comparison of our absolute photometry to surface fluxes generated by atmospheric models, we also aim at deriving mass and radius estimates that are independent of evolutionary model predictions to test and refine them. Methods: We used the adaptive-optics-fed integral field spectrograph SINFONI to obtain high-quality, medium-resolution spectra of AB Pic b (R_λ = 1500-2000) over the 1.1-2.5 μm range. Our analysis relie on comparing our spectra to young standard templates and to the latest libraries of synthetic spectra developed by the Lyon group. Results: AB Pic b is confirmed as a young early-L dwarf companion. We derive a spectral type L0-L1 and find several features indicative of an intermediate gravity atmosphere. A comparison to synthetic spectra yields Teff = 2000+100-300 K and log(g) = 4 ± 0.5 dex. Determination of the derived atmospheric parameters of AB Pic b is limited by an imperfect match of current atmosphere spectra with our near-infrared observations of AB Pic b. The current treatment of dust settling and the missing molecular opacity lines in the atmosphere models could be responsible. By combining the observed photometry, the surface fluxes from atmosphere models and the known distance of the system, we derive new mass, luminosity, and radius estimates of AB Pic b. They independently confirm the evolutionary model predictions. We finally review the current methods used for characterizing planetary mass companions and discuss them in the perspective of future planet deep-imaging surveys that will be faced with the same limitations. Based on service

  19. A white dwarf companion to the main-sequence star 4 Omicron(1) Orionis and the binary hypothesis for the origin of peculiar red giants

    NASA Technical Reports Server (NTRS)

    Ake, Thomas B.; Johnson, Hollis R.

    1988-01-01

    Ultraviolet spectra of the peculiar red giants (PRGs) called MS stars are investigated, and the discovery of a white dwarf (WD) companion to the MS star 4 Omicron(1) Orionis is reported. The observations and data analysis are discussed and compared with those for field WDs in order to derive parameters for the WD and the luminosity of the primary. Detection limits for the other MS stars investigated are derived, and the binary hypothesis for PRGs is reviewed.

  20. The SOPHIE search for northern extrasolar planets. VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

    NASA Astrophysics Data System (ADS)

    Bouchy, F.; Ségransan, D.; Díaz, R. F.; Forveille, T.; Boisse, I.; Arnold, L.; Astudillo-Defru, N.; Beuzit, J.-L.; Bonfils, X.; Borgniet, S.; Bourrier, V.; Courcol, B.; Delfosse, X.; Demangeon, O.; Delorme, P.; Ehrenreich, D.; Hébrard, G.; Lagrange, A.-M.; Mayor, M.; Montagnier, G.; Moutou, C.; Naef, D.; Pepe, F.; Perrier, C.; Queloz, D.; Rey, J.; Sahlmann, J.; Santerne, A.; Santos, N. C.; Sivan, J.-P.; Udry, S.; Wilson, P. A.

    2016-01-01

    Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-yr radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 MJup orbiting solar-type stars with periods longer than ten years. An upper mass limit of these companions is provided using astrometric Hipparcos data, high-angular resolution imaging made with PUEO, and a deep analysis of the cross-correlation function of the main stellar spectra to search for blend effects or faint secondary components. These objects double the number of known brown dwarf companions with orbital periods longer than ten years and reinforce the conclusion that the occurrence of such objects increases with orbital separation. With a projected separation larger than 100 mas, all these brown dwarf candidates are appropriate targets for high-contrast and high angular resolution imaging. Based on observations made with ELODIE and SOPHIE spectrographs on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS/AMU), France.Tables 5-9 (RV data) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A46

  1. Mass ratio of the 2 pc binary brown dwarf LUH 16 and limits on planetary companions from astrometry

    NASA Astrophysics Data System (ADS)

    Sahlmann, J.; Lazorenko, P. F.

    2015-10-01

    We analyse FORS2/VLT I-band imaging data to monitor the motions of both components in the nearest known binary brown dwarf WISE J104915.57-531906.1AB (LUH 16) over one year. The astrometry is dominated by parallax and proper motion, but with a precision of ˜0.2 mas per epoch we accurately measure the relative position change caused by the orbital motion of the pair. This allows us to directly measure a mass ratio of q = 0.78 ± 0.10 for this system. We also search for the signature of a planetary-mass companion around either of the A and B component and exclude at 3σ the presence of planets with masses larger than 2 MJ and orbital periods of 20-300 d. We update the parallax of LUH 16 to 500.51 ± 0.11 mas, i.e. just within 2 pc. This study yields the first direct constraint on the mass ratio of LUH 16 and shows that the system does not harbour any close-in giant planets.

  2. The Discovery of a Companion to the Very Cool Dwarf Gliese 569B with the Keck Adaptive Optics Facility.

    PubMed

    Martín; Koresko; Kulkarni; Lane; Wizinowich

    2000-01-20

    We report observations obtained with the Keck adaptive optics facility of the nearby (d=9.8 pc) binary Gl 569. The system was known to be composed of a cool primary (dM2) and a very cool secondary (dM8.5) with a separation of 5&arcsec; (49 AU). We have found that Gl 569B is itself double with a separation of only 0&farcs;101+/-0&farcs;002 (1 AU). This detection demonstrates the superb spatial resolution that can be achieved with adaptive optics at Keck. The difference in brightness between Gl 569B and the companion is approximately 0.5 mag in the J, H, and K&arcmin; bands. Thus, both objects have similarly red colors and very likely constitute a very low mass binary system. For reasonable assumptions about the age (0.12-1.0 Gyr) and total mass of the system (0.09-0.15 M middle dot in circle), we estimate that the orbital period is approximately 3 yr. Follow-up observations will allow us to obtain an astrometric orbit solution and will yield direct dynamical masses that can constrain evolutionary models of very low mass stars and brown dwarfs. PMID:10615031

  3. The NGC 3341 minor merger: a panchromatic view of the active galactic nucleus in a dwarf companion

    NASA Astrophysics Data System (ADS)

    Bianchi, Stefano; Piconcelli, Enrico; Pérez-Torres, Miguel Ángel; Fiore, Fabrizio; La Franca, Fabio; Mathur, Smita; Matt, Giorgio

    2013-11-01

    We present X-ray (Chandra), radio (Expanded Very Large Array and European VLBI Network) and archival optical data of the triple-merging system in NGC 3341. Our panchromatic analysis confirms the presence of a Seyfert 2 active galactic nucleus (AGN) in NGC 3341B, one of the secondary dwarf companions. On the other hand, the nucleus of the primary galaxy, consistent with a star-forming region of a few solar masses per year, and NGC 3341C are very unlikely to host an AGN. We therefore suggest that NGC 3341 is an exceptional example of an AGN triggered in the satellite galaxy of a minor-merging system. The existence of such a system can have important implications in the models of hierarchical growth of structures. Further observational and theoretical efforts on NGC 3341 and potentially similar sources are needed in order to understand the role of minor mergers on the onset of AGN activity, and in the evolution of massive galaxies.

  4. Mass ratio of the 2 pc binary brown dwarf LUH 16 and limits on planetary companions from astrometry

    NASA Astrophysics Data System (ADS)

    Sahlmann, Johannes; Lazorenko, Petro F.

    2016-01-01

    We analyse FORS2/VLT I-band imaging data to monitor the motions of both components in the nearest known binary brown dwarf WISE J104915.57-531906.1AB (LUH 16) over one year. The astrometry is dominated by parallax and proper motion, but with a precision of 0.2 mas per epoch we accurately measure the relative position change caused by the orbital motion of the pair. This allows us to directly measure a mass ratio of q = 0.78 ± 0.10 for this system. We also search for the signature of a planetary-mass companion around either of the A and B component and exclude at 3σ the presence of planets with masses larger than 2 MJ and orbital periods of 20-300 d. We update the parallax of LUH 16 to 500.51 ± 0.11 mas, i.e. just within 2 pc. This study yields the first direct constraint on the mass ratio of LUH 16 and shows that the system does not harbour any close-in giant planets.

  5. TWO NEW LONG-PERIOD HOT SUBDWARF BINARIES WITH DWARF COMPANIONS

    SciTech Connect

    Barlow, Brad N.; Wade, Richard A.; Liss, Sandra E.; Green, Elizabeth M.

    2013-07-01

    Hot subdwarf stars with F-K main sequence binary companions have been known for decades, but the first orbital periods for such systems were published just recently. Current observations suggest that most have long periods, on the order of years, and that some are or once were hierarchical triple systems. As part of a survey with the Hobby-Eberly Telescope, we have been monitoring the radial velocities of several composite-spectra binaries since 2005 in order to determine their periods, velocities, and eccentricities. Here we present observations and orbital solutions for two of these systems, PG 1449+653 and PG 1701+359. Similar to the other sdB+F/G/K binaries with solved orbits, their periods are long, 909 and 734 days, respectively, and pose a challenge to current binary population synthesis models of hot subdwarf stars. Intrigued by their relatively large systemic velocities, we also present a kinematical analysis of both targets and find that neither is likely a member of the Galactic thin disk.

  6. On the Formation of Eccentric Millisecond Pulsars with Helium White-dwarf Companions

    NASA Astrophysics Data System (ADS)

    Antoniadis, John

    2014-12-01

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire & Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (104-105 yr) disk can result in eccentricities of e ~= 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  7. ON THE FORMATION OF ECCENTRIC MILLISECOND PULSARS WITH HELIUM WHITE-DWARF COMPANIONS

    SciTech Connect

    Antoniadis, John

    2014-12-20

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (10{sup 4}-10{sup 5} yr) disk can result in eccentricities of e ≅ 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  8. SUBSTELLAR-MASS COMPANIONS TO THE K-DWARF BD+14 4559 AND THE K-GIANTS HD 240210 AND BD+20 2457

    SciTech Connect

    Niedzielski, A.; Nowak, G.; Adamow, M.; Wolszczan, A. E-mail: Grzegorz.Nowak@astri.uni.torun.p E-mail: alex@astro.psu.ed

    2009-12-10

    We present the discovery of substellar-mass companions to three stars by the ongoing Penn State-Torun Planet Search conducted with the 9.2 m Hobby-Eberly Telescope. The K2-dwarf, BD+14 4559, has a 1.5 M{sub J} minimum mass companion with the orbital period of 269 days and shows a non-linear, long-term radial velocity (RV) trend, which indicates a possible presence of another planet-mass body in the system. The K3-giant, HD 240210, exhibits RV variations that require modeling with multiple orbits, but the available data are not yet sufficient to do it unambiguously. A tentative, one-planet model calls for a 5.2 M{sub J} minimum mass planet in a 502 day orbit around the star. The most massive of the three stars, the K2-giant, BD+20 2457, whose estimated mass is 2.8 +- 1.5 M {sub sun}, has two companions with the respective minimum masses of 21.4 M{sub J} and 12.5 M{sub J} and orbital periods of 380 and 622 days. Depending on the unknown inclinations of the orbits, the currently very uncertain mass of the star, and the dynamical properties of the system, it may represent the first detection of two brown dwarf-mass companions orbiting a giant. The existence of such objects will have consequences for the interpretation of the so-called brown dwarf desert known to exist in the case of solar-mass stars.

  9. PLANETS AROUND LOW-MASS STARS (PALMS). I. A SUBSTELLAR COMPANION TO THE YOUNG M DWARF 1RXS J235133.3+312720

    SciTech Connect

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

    2012-07-10

    We report the discovery of a brown dwarf companion to the young M dwarf 1RXS J235133.3+312720 as part of a high contrast imaging search for planets around nearby young low-mass stars with Keck-II/NIRC2 and Subaru/HiCIAO. The 2.''4 ({approx}120 AU) pair is confirmed to be comoving from two epochs of high-resolution imaging. Follow-up low- and moderate-resolution near-infrared spectroscopy of 1RXS J2351+3127 B with IRTF/SpeX and Keck-II/OSIRIS reveals a spectral type of L0{sup +2}{sub -1}. The M2 primary star 1RXS J2351+3127 A exhibits X-ray and UV activity levels comparable to young moving group members with ages of {approx}10-100 Myr. UVW kinematics based the measured radial velocity of the primary and the system's photometric distance (50 {+-} 10 pc) indicate it is likely a member of the {approx}50-150 Myr AB Dor moving group. The near-infrared spectrum of 1RXS J2351+3127 B does not exhibit obvious signs of youth, but its H-band morphology shows subtle hints of intermediate surface gravity. The spectrum is also an excellent match to the {approx}200 Myr M9 brown dwarf LP 944-20. Assuming an age of 50-150 Myr, evolutionary models imply a mass of 32 {+-} 6 M{sub Jup} for the companion, making 1RXS J2351+3127 B the second lowest-mass member of the AB Dor moving group after the L4 companion CD-35 2722 B and one of the few benchmark brown dwarfs known at young ages.

  10. SPLAT: Using Spectral Indices to Identify and Characterize Ultracool Stars, Brown Dwarfs and Exoplanets in Deep Surveys and as Companions to Nearby Stars

    NASA Astrophysics Data System (ADS)

    Aganze, Christian; Burgasser, Adam J.; Martin, Eduardo; Konopacky, Quinn; Masters, Daniel C.

    2016-06-01

    The majority of ultracool dwarf stars and brown dwarfs currently known were identified in wide-field red optical and infrared surveys, enabling measures of the local, typically isolated, population in a relatively shallow (<100 pc radius) volume. Constraining the properties of the wider Galactic population (scale height, radial distribution, Population II sources), and close brown dwarf and exoplanet companions to nearby stars, requires specialized instrumentation, such as high-contrast, coronagraphic spectrometers (e.g., Gemini/GPI, VLT/Sphere, Project 1640); and deep spectral surveys (e.g., HST/WFC3 parallel fields, Euclid). We present a set of quantitative methodologies to identify and robustly characterize sources for these specific populations, based on templates and tools developed as part of the SpeX Prism Library Analysis Toolkit. In particular, we define and characterize specifically-tuned sets spectral indices that optimize selection of cool dwarfs and distinguish rare populations (subdwarfs, young planetary-mass objects) based on low-resolution, limited-wavelength-coverage spectral data; and present a template-matching classification method for these instruments. We apply these techniques to HST/WFC3 parallel fields data in the WISPS and HST-3D programs, where our spectral index set allows high completeness and low contamination for searches of late M, L and T dwarfs to distances out to ~3 kpc.The material presented here is based on work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  12. PLANETS AROUND LOW-MASS STARS. III. A YOUNG DUSTY L DWARF COMPANION AT THE DEUTERIUM-BURNING LIMIT ,

    SciTech Connect

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

    2013-09-01

    We report the discovery of an L-type companion to the young M3.5V star 2MASS J01225093-2439505 at a projected separation of 1.''45 ( Almost-Equal-To 52 AU) as part of our adaptive optics imaging search for extrasolar giant planets around young low-mass stars. 2MASS 0122-2439 B has very red near-infrared colors similar to the HR 8799 planets and the reddest known young/dusty L dwarfs in the field. Moderate-resolution (R Almost-Equal-To 3800) 1.5-2.4 {mu}m spectroscopy reveals a near-infrared spectral type of L4-L6 and an angular H-band shape, confirming its cool temperature and young age. The kinematics of 2MASS 0122-2439 AB are marginally consistent with members of the {approx}120 Myr AB Dor young moving group based on the photometric distance to the primary (36 {+-} 4 pc) and our radial velocity measurement of 2MASS 0122-2439 A from Keck/HIRES. We adopt the AB Dor group age for the system, but the high energy emission, lack of Li I {lambda}6707 absorption, and spectral shape of 2MASS 0122-2439 B suggest a range of {approx}10-120 Myr is possible. The age and luminosity of 2MASS 0122-2439 B fall in a strip where ''hot-start'' evolutionary model mass tracks overlap as a result of deuterium burning. Several known substellar companions also fall in this region (2MASS J0103-5515 ABb, AB Pic b, {kappa} And b, G196-3 B, SDSS 2249+0044 B, LP 261-75 B, HD 203030 B, and HN Peg B), but their dual-valued mass predictions have largely been unrecognized. The implied mass of 2MASS 0122-2439 B is Almost-Equal-To 12-13 M{sub Jup} or Almost-Equal-To 22-27 M{sub Jup} if it is an AB Dor member, or possibly as low as 11 M{sub Jup} if the wider age range is adopted. Evolutionary models predict an effective temperature for 2MASS 0122-2439 B that corresponds to spectral types near the L/T transition ( Almost-Equal-To 1300-1500 K) for field objects. However, we find a mid-L near-infrared spectral type, indicating that 2MASS 0122-2439 B represents another case of photospheric dust being

  13. TWO PLANETARY COMPANIONS AROUND THE K7 DWARF GJ 221: A HOT SUPER-EARTH AND A CANDIDATE IN THE SUB-SATURN DESERT RANGE

    SciTech Connect

    Arriagada, Pamela; Minniti, Dante; Anglada-Escude, Guillem; Butler, R. Paul; Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian; Wende, Sebastian

    2013-07-01

    We report two low-mass companions orbiting the nearby K7 dwarf GJ 221 that have emerged from reanalyzing 4.4 yr of publicly available HARPS spectra complemented with 2 years of high-precision Doppler measurements with Magellan/PFS. The HARPS measurements alone contain the clear signal of a low-mass companion with a period of 125 days and a minimum mass of 53.2 M{sub Circled-Plus} (GJ 221b), falling in a mass range where very few planet candidates have been found (sub-Saturn desert). The addition of 17 PFS observations allows the confident detection of a second low-mass companion (6.5 M{sub Circled-Plus }) in a hot orbit (3.87 day period, GJ 221c). Spectroscopic and photometric calibrations suggest that GJ 221 is slightly depleted ([Fe/H] {approx} -0.1) compared to the Sun, so the presence of two low-mass companions in the system confirms the trend that slightly reduced stellar metallicity does not prevent the formation of planets in the super-Earth to sub-Saturn mass regime.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We used the Magellan adaptive optics system and its VisAO CCD camera to image the young low mass brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r', i', z', and YS . With our new photometry and T eff ~ 2500 K derived from the shape of its K-band spectrum, we find that CT Cha B has AV = 3.4 ± 1.1 mag, and a mass of 14-24 MJ according to the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r' detection indicates that the companion has significant Hα emission and a mass accretion rate ~6 × 10-10 M ⊙ yr-1, similar to some substellar companions. Proper motion analysis shows that another point source within 2'' of CT Cha A is not physical. This paper demonstrates how visible wavelength adaptive optics photometry (r', i', z', YS ) allows for a better estimate of extinction, luminosity, and mass accretion rate of young substellar companions. This paper includes data gathered with the 6.5 m Magellan Clay Telescope at Las Campanas Observatory, Chile.

  15. First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Sand, David J.; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F.; Brodie, Jean P.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

    2016-09-01

    We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ∼35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has {M}g=-7.4+/- 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color–magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas ({M}{HI}/{L}V\\lt 0.69 {M}ȯ /{L}ȯ , based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ∼4–10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2–3 within our field of view, slightly more than the one such satellite observed in our footprint. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  16. First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Sand, David J.; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F.; Brodie, Jean P.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

    2016-09-01

    We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ˜35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has {M}g=-7.4+/- 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color–magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas ({M}{HI}/{L}V\\lt 0.69 {M}ȯ /{L}ȯ , based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ˜4–10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2–3 within our field of view, slightly more than the one such satellite observed in our footprint. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  17. PLANETS AROUND LOW-MASS STARS (PALMS). II. A LOW-MASS COMPANION TO THE YOUNG M DWARF GJ 3629 SEPARATED BY 0.''2

    SciTech Connect

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

    2012-09-01

    We present the discovery of a 0.''2 companion to the young M dwarf GJ 3629 as part of our high-contrast adaptive optics imaging search for giant planets around low-mass stars with the Keck-II and Subaru telescopes. Two epochs of imaging confirm that the pair is comoving and reveal signs of orbital motion. The primary exhibits saturated X-ray emission which, together with its UV photometry from GALEX, points to an age younger than {approx}300 Myr. At these ages the companion lies below the hydrogen burning limit with a model-dependent mass of 46 {+-} 16 M{sub Jup} based on the system's photometric distance of 22 {+-} 3 pc. Resolved YJHK photometry of the pair indicates a spectral type of M7 {+-} 2 for GJ 3629 B. With a projected separation of 4.4 {+-} 0.6 AU and an estimated orbital period of 21 {+-} 5 yr, GJ 3629 AB is likely to yield a dynamical mass in the next several years, making it one of only a handful of brown dwarfs to have a measured mass and an age constrained from the stellar primary.

  18. BINARIES DISCOVERED BY THE MUCHFUSS PROJECT: SDSS J08205+0008-AN ECLIPSING SUBDWARF B BINARY WITH A BROWN DWARF COMPANION

    SciTech Connect

    Geier, S.; Schaffenroth, V.; Drechsel, H.; Heber, U.; Kupfer, T.; Tillich, A.; Oestensen, R. H.; Smolders, K.; Degroote, P.; Maxted, P. F. L.; Barlow, B. N.; Gaensicke, B. T.; Marsh, T. R.; Napiwotzki, R.

    2011-04-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

  20. MagAO Imaging of Long-period Objects (MILO). I. A Benchmark M Dwarf Companion Exciting a Massive Planet around the Sun-like Star HD 7449

    NASA Astrophysics Data System (ADS)

    Rodigas, Timothy J.; Arriagada, Pamela; Faherty, Jackie; Anglada-Escudé, Guillem; Kaib, Nathan; Butler, R. Paul; Shectman, Stephen; Weinberger, Alycia; Males, Jared R.; Morzinski, Katie M.; Close, Laird M.; Hinz, Philip M.; Crane, Jeffrey D.; Thompson, Ian; Teske, Johanna; Díaz, Matías; Minniti, Dante; Lopez-Morales, Mercedes; Adams, Fred C.; Boss, Alan P.

    2016-02-01

    We present high-contrast Magellan adaptive optics images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6-2.15 μm at a separation of ˜0.″54. We use the object’s colors and spectral energy distribution to show that it is most likely an M4-M5 dwarf (mass ˜0.1-0.2 {M}⊙ ) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and Planet Finder Spectrograph spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass (\\gt 0.17 {M}⊙ at 99% confidence) and semimajor axis (˜18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is {1.09}-0.19+0.52 MJ, its semimajor axis is {2.33}-0.02+0.01 AU, and its eccentricity is {0.8}-0.06+0.08. We use N-body simulations to constrain the eccentricity of HD 7449B to ≲0.5. The M dwarf may be inducing Kozai oscillations on the planet, explaining its high eccentricity. If this is the case and its orbit was initially circular, the mass of the planet would need to be ≲1.5 MJ. This demonstrates that strong constraints on known planets can be made using direct observations of otherwise undetectable long-period companions. This paper includes data obtained at the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  1. Binary frequency of planet-host stars at wide separations. A new brown dwarf companion to a planet-host star

    NASA Astrophysics Data System (ADS)

    Lodieu, N.; Pérez-Garrido, A.; Béjar, V. J. S.; Gauza, B.; Ruiz, M. T.; Rebolo, R.; Pinfield, D. J.; Martín, E. L.

    2014-09-01

    Aims: The aim of the project is to improve our knowledge on the multiplicity of planet-host stars at wide physical separations. Methods: We cross-matched approximately 6200 square degree area of the southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. Results: We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3 arcmin (~9000 au) from HIP 70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5.4±3.8% and 2.7±2.7% (1σ confidence level), respectively, for projected physical separations larger than ~60-160 au assuming the range of distances of planet-host stars (24-75 pc). These values are comparable to the frequencies of non planet-host stars. We find that the period-eccentricity trend holds with a lack of multiple systems with planets at large eccentricities (e> 0.2) for periods less than 40 days. However, the lack of planets more massive than 2.5 Jupiter masses and short periods (<40 days) orbiting single stars is not so obvious due to recent discoveries by ground-based transit surveys and space missions. Appendix A is available in electronic form at http://www.aanda.orgSpectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/A120Based on observations collected at the European Organisation for Astronomical Research

  2. AN ASTROMETRIC SEARCH FOR A SUB-STELLAR COMPANION OF THE M8.5 DWARF TVLM 513–46546 USING VERY LONG BASELINE INTERFEROMETRY

    SciTech Connect

    Forbrich, Jan; Berger, Edo; Reid, Mark J.

    2013-11-01

    We conducted multi-epoch very long baseline interferometry observations to search for astrometric reflex motion that would be caused by a sub-stellar companion of the M8.5 dwarf TVLM 513–46546. The observations yield an absolute parallax corresponding to a distance of 10.762 ± 0.027 pc and a proper motion of 78.09 ± 0.17 mas yr{sup –1}. The averaged flux density per epoch varies by a factor of at least three. From the absence of significant residual motion, we place an upper limit on any reflex motion caused by a companion, extending the parameter space covered by previous near-infrared direct-imaging searches. The data exclude a phase space of companion masses and orbital periods ranging from 3.8 M{sub Jup} with an orbital radius of ∼0.05 AU (and an orbital period of 16 days) to 0.3 M{sub Jup} with an orbital radius of ∼0.7 AU (and an orbital period of 710 days)

  3. TWA Flight 800, explosion airblast unexplained

    NASA Astrophysics Data System (ADS)

    Reed, Jack W.

    2003-10-01

    TWA Flight 800 disintegrated off Long Island, NY, on 16 July 1996. Immediate reports from other flyers described what appeared as attacking missiles. Search for terrorists began quickly, with over 1000 FBI agents to collect debris, interview eyewitnesses, and analyze sightings to give a missile launch point. They found no evidence of criminal attack, and turned investigations over to the NTSB to find some accidental cause. The ``empty'' central fuel tank was determined to be the likely explosion source. On the other hand, early witnesses reported a ``loud'' bang after seeing a great fireball fall from the sky, but at 15 km or greater range, they saw and heard two different events. This acoustic discrepancy has not been adequately investigated. When finally released, FBI reports from more than 200 ``ear-witnesses'' give similar observations. Their loudness reports confirm that at least a ton of TNT equivalent explosion had occurred. NASA acousticians engaged by NTSB, however, through spectral analysis techniques for sonic booms, concluded that a 10-kg TNT explosion, from detonating fuel tank vapors, could be heard on Long Island. Evidence for a much larger yield is presented here, but its form remains a mystery.

  4. The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits . III. The frequency of brown dwarfs and giant planets as companions to solar-type stars

    NASA Astrophysics Data System (ADS)

    Reggiani, M.; Meyer, M. R.; Chauvin, G.; Vigan, A.; Quanz, S. P.; Biller, B.; Bonavita, M.; Desidera, S.; Delorme, P.; Hagelberg, J.; Maire, A.-L.; Boccaletti, A.; Beuzit, J.-L.; Buenzli, E.; Carson, J.; Covino, E.; Feldt, M.; Girard, J.; Gratton, R.; Henning, T.; Kasper, M.; Lagrange, A.-M.; Mesa, D.; Messina, S.; Montagnier, G.; Mordasini, C.; Mouillet, D.; Schlieder, J. E.; Segransan, D.; Thalmann, C.; Zurlo, A.

    2016-02-01

    Context. In recent years there have been many attempts to characterize the occurrence and distribution of stellar, brown dwarf (BD), and planetary-mass companions to solar-type stars with the aim of constraining formation mechanisms. From radial velocity observations a dearth of companions with masses between 10-40 MJupiter has been noticed at close separations, suggesting the possibility of a distinct formation mechanism for objects above and below this range. Aims: We present a model for the substellar companion mass function (CMF). This model consists of the superposition of the planet and BD companion mass distributions, assuming that we can extrapolate the radial velocity measured CMF for planets to larger separations and the stellar companion mass-ratio distribution over all separations into the BD mass regime. By using both the results of the VLT/NaCo large program (NaCo-LP) and the complementary archive datasets, which probe the occurrence of planets and BDs on wide orbits around solar-type stars, we place some constraints on the planet and BD distributions. Methods: We developed a Monte Carlo simulation tool to predict the outcome of a given survey, depending on the shape of the orbital parameter distributions (mass, semimajor axis, eccentricity, and inclination). Comparing the predictions with the results of the observations, we calculate the likelihood of different models and which models can be ruled out. Results: Current observations are consistent with the proposed model for the CMF, as long as a sufficiently small outer truncation radius (≲100 AU) is introduced for the planet separation distribution. Some regions of parameter space can be excluded by the observations. Conclusions: We conclude that the results of the direct imaging surveys searching for substellar companions around Sun-like stars are consistent with a combined substellar mass spectrum of planets and BDs. This mass distribution has a minimum between 10 and 50 MJupiter, in agreement

  5. A THERMAL INFRARED IMAGING STUDY OF VERY LOW MASS, WIDE-SEPARATION BROWN DWARF COMPANIONS TO UPPER SCORPIUS STARS: CONSTRAINING CIRCUMSTELLAR ENVIRONMENTS

    SciTech Connect

    Bailey, Vanessa; Hinz, Philip M.; Su, Kate Y. L.; Hoffmann, William F.; Rieke, George; Rodigas, Timothy; Skemer, Andrew; Vaitheeswaran, Vidhya; Currie, Thayne; Esposito, Simone; Pinna, Enrico; Puglisi, Alfio; Hill, John M.; Jones, Terry; Kim, Jihun; Leisenring, Jarron; Meyer, Michael; Murray-Clay, Ruth; Skrutskie, Michael F.; Nelson, Matthew J.; and others

    2013-04-10

    We present a 3-5 {mu}m LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low masses/mass ratios (M{sub BD} <25 M{sub Jup}; M{sub BD}/M{sub *} Almost-Equal-To 1%-2%) and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4 {mu}m and 24 {mu}m photometry to constrain the properties of the BDs and identify evidence for circumprimary/circumsecondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing that this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24 {mu}m excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4 {mu}m excess, nor does its primary; however, the system as a whole has a modest 24 {mu}m excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4 {mu}m colors of HIP 78530B match a spectral type of M3 {+-} 2, inconsistent with the M8 spectral type assigned based on its near-IR spectrum, indicating that it may be a low-mass star rather than a BD. We present new upper limits on additional low-mass companions in the system (<5 M{sub Jup} beyond 175 AU). Finally, we examine the utility of circumsecondary disks as probes of the formation histories of wide BD companions, finding that the presence of a disk may disfavor BD formation near the primary with subsequent outward scattering.

  6. DISCOVERY OF TWO VERY WIDE BINARIES WITH ULTRACOOL COMPANIONS AND A NEW BROWN DWARF AT THE L/T TRANSITION

    SciTech Connect

    Muzic, Koraljka; Radigan, Jacqueline; Jayawardhana, Ray; Ivanov, Valentin D.; Boffin, Henri M. J.; Jones, David; Tyndall, Amy; Faherty, Jacqueline K.; Kurtev, Radostin G.; Borissova, Jura; Nunez, Alejandro; Cruz, Kelle; Hainaut, Olivier; Metchev, Stanimir

    2012-12-01

    We present the discovery and spectroscopic follow-up of a nearby late-type L dwarf (2M0614+3950), and two extremely wide very low mass binary systems (2M0525-7425AB and 2M1348-1344AB), resulting from our search for common proper motion pairs containing ultracool components in the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer catalogs. The near-infrared spectrum of 2M0614+3950 indicates a spectral type L9 {+-} 1 object residing at a distance of 26.0 {+-} 1.8 pc. The optical spectrum of 2M0525-7425A reveals an M3.0 {+-} 0.5 dwarf primary, accompanied by a secondary previously classified as L2. The system has an angular separation of {approx}44'', equivalent to {approx}2000 AU at a distance of 46.0 {+-} 3.0 pc. Using optical and infrared spectra, respectively, we classify the components of 2M1348-1344AB as M4.5 {+-} 0.5 and T5.5 {+-} 1. The angular separation of {approx}68'' is equivalent to {approx}1400 AU at a distance of 20.7 {+-} 1.4 pc. 2M1348-1344AB is one of only six very wide (separation >1000 AU) systems containing late T dwarfs known to date.

  7. Pattern of crescendo TWA may disclose the underlying cardiac pathology.

    PubMed

    Nieminen, Tuomo; Verrier, Richard L; Nikus, Kjell; Viik, Jari; Lehtinen, Rami; Lehtimäki, Terho; Kaiser, Willi; Kähönen, Mika

    2010-01-01

    We present an exercise test case in which crescendo TWA preceded ventricular tachycardia (VT). The patient was examined due to suspicion of ischemic heart disease. The ST-segment became elevated simultaneously with a distinct alternation in the ST-segment and the first half of the T-wave, and the patient developed polymorphic VT. Coronary angiography disclosed marked stenoses. Earlier reports of TWA in patients with congenital long QT syndrome show a pattern in which the T wave frequently alternates above and below the isoelectric line without concomitant ST-segment changes. In Brugada syndrome patients, the signature ST-T wave pattern is the locus of alternation. Future investigation should elucidate whether specific TWA morphologies may expose underlying heart disease. PMID:20413129

  8. HIGH-CONTRAST 3.8 {mu}m IMAGING OF THE BROWN DWARF/PLANET-MASS COMPANION TO GJ 758

    SciTech Connect

    Currie, Thayne; Bailey, Vanessa; Rodigas, Timothy; Hinz, Phil; Fabrycky, Daniel; Murray-Clay, Ruth

    2010-10-01

    We present L'-band (3.8 {mu}m) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. to have one -- possibly two -- faint comoving companions (GJ 758B and 'C', respectively). GJ 758B is detected in two distinct data sets. Additionally, we report a possible detection of the object identified by Thalmann et al. as 'GJ 758C' in our more sensitive data set, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 758B has an H - L' color redder than nearly all known L-T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has T {sub e} {approx} 560 K{sup +150K}{sub -90 K}{sup +150 K) and a mass ranging from {approx}10-20 M{sub J} if it is {approx}1 Gyr old to {approx} 25-40 M{sub J} if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e {approx} 0.73{sup +0.12}{sub -0.21}, with a semimajor axis of {approx}44 AU{sup +32 AU){sub -14 AU}. Though GJ 758B is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of Jovian-mass planets.

  9. CROWDING-OUT OF GIANTS BY DWARFS: AN ORIGIN FOR THE LACK OF COMPANION PLANETS IN HOT JUPITER SYSTEMS

    SciTech Connect

    Ogihara, Masahiro; Inutsuka, Shu-ichiro; Kobayashi, Hiroshi

    2013-11-20

    We investigate the formation of close-in terrestrial planets from planetary embryos under the influence of a hot Jupiter (HJ) using gravitational N-body simulations that include gravitational interactions between the gas disk and the terrestrial planet (e.g., type I migration). Our simulations show that several terrestrial planets efficiently form outside the orbit of the HJ, making a chain of planets, and all of them gravitationally interact directly or indirectly with the HJ through resonance, which leads to inward migration of the HJ. We call this mechanism of induced migration of the HJ ''crowding-out''. The HJ is eventually lost through collision with the central star, and only several terrestrial planets remain. We also find that the efficiency of the crowding-out effect depends on the model parameters; for example, the heavier the disk is, the more efficient the crowding-out is. When planet formation occurs in a massive disk, the HJ can be lost to the central star and is never observed. On the other hand, for a less massive disk, the HJ and terrestrial planets can coexist; however, the companion planets may be below the detection limit of current observations. In both cases, systems with a HJ and terrestrial planets have little chance of detection. Therefore, our model naturally explains the lack of companion planets in HJ systems regardless of the disk mass. In effect, our model provides a theoretical prediction for future observations; additional planets can be discovered just outside the HJ, and their masses should generally be small.

  10. A Thermal Infrared Imaging Study of Very Low Mass, Wide-separation Brown Dwarf Companions to Upper Scorpius Stars: Constraining Circumstellar Environments

    NASA Astrophysics Data System (ADS)

    Bailey, Vanessa; Hinz, Philip M.; Currie, Thayne; Su, Kate Y. L.; Esposito, Simone; Hill, John M.; Hoffmann, William F.; Jones, Terry; Kim, Jihun; Leisenring, Jarron; Meyer, Michael; Murray-Clay, Ruth; Nelson, Matthew J.; Pinna, Enrico; Puglisi, Alfio; Rieke, George; Rodigas, Timothy; Skemer, Andrew; Skrutskie, Michael F.; Vaitheeswaran, Vidhya; Wilson, John C.

    2013-04-01

    We present a 3-5 μm LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low masses/mass ratios (M BD <25 M Jup; M BD/M sstarf ≈ 1%-2%) and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4 μm and 24 μm photometry to constrain the properties of the BDs and identify evidence for circumprimary/circumsecondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing that this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24 μm excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4 μm excess, nor does its primary; however, the system as a whole has a modest 24 μm excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4 μm colors of HIP 78530B match a spectral type of M3 ± 2, inconsistent with the M8 spectral type assigned based on its near-IR spectrum, indicating that it may be a low-mass star rather than a BD. We present new upper limits on additional low-mass companions in the system (<5 M Jup beyond 175 AU). Finally, we examine the utility of circumsecondary disks as probes of the formation histories of wide BD companions, finding that the presence of a disk may disfavor BD formation near the primary with subsequent outward scattering. Observations reported here were obtained at the LBT and MMT Observatories. The MMT Observatory is a joint facility of the University of Arizona and the Smithsonian Institution. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT

  11. Characterization of the atmosphere of the hot Jupiter HAT-P-32Ab and the M-dwarf companion HAT-P-32B

    SciTech Connect

    Zhao, Ming; Wright, Jason T.; Curtis, Jason; O'Rourke, Joseph G.; Knutson, Heather A.; Ngo, Henry; Burrows, Adam; Fortney, Johnathan; Fulton, Benjamin J.; Baranec, Christoph; Riddle, Reed; Hinkley, Sasha; Law, Nicholas M.; Muirhead, Philip S.; Showman, Adam P.; Burruss, Rick

    2014-12-01

    We report secondary eclipse photometry of the hot Jupiter HAT-P-32Ab, taken with Hale/Wide-field Infra-Red Camera (WIRC) in H and K{sub S} bands and with Spitzer/IRAC at 3.6 and 4.5 μm. We carried out adaptive optics imaging of the planet host star HAT-P-32A and its companion HAT-P-32B in the near-IR and the visible. We clearly resolve the two stars from each other and find a separation of 2.''923 ± 0.''004 and a position angle 110.°64 ± 0.°12. We measure the flux ratios of the binary in g'r'i'z' and H and K{sub S} bands, and determine T {sub eff}= 3565 ± 82 K for the companion star, corresponding to an M1.5 dwarf. We use PHOENIX stellar atmosphere models to correct the dilution of the secondary eclipse depths of the hot Jupiter due to the presence of the M1.5 companion. We also improve the secondary eclipse photometry by accounting for the non-classical, flux-dependent nonlinearity of the WIRC IR detector in the H band. We measure planet-to-star flux ratios of 0.090% ± 0.033%, 0.178% ± 0.057%, 0.364% ± 0.016%, and 0.438% ± 0.020% in the H, K{sub S} , 3.6 and 4.5 μm bands, respectively. We compare these with planetary atmospheric models, and find they prefer an atmosphere with a temperature inversion and inefficient heat redistribution. However, we also find that the data are equally well described by a blackbody model for the planet with T {sub p} = 2042 ± 50 K. Finally, we measure a secondary eclipse timing offset of 0.3 ± 1.3 minutes from the predicted mid-eclipse time, which constrains e = 0.0072{sub −0.0064}{sup +0.0700} when combined with radial velocity data and is more consistent with a circular orbit.

  12. Characterization of the Atmosphere of the Hot Jupiter HAT-P-32Ab and the M-dwarf Companion HAT-P-32B

    NASA Astrophysics Data System (ADS)

    Zhao, Ming; O'Rourke, Joseph G.; Wright, Jason T.; Knutson, Heather A.; Burrows, Adam; Fortney, Johnathan; Ngo, Henry; Fulton, Benjamin J.; Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Muirhead, Philip S.; Hinkley, Sasha; Showman, Adam P.; Curtis, Jason; Burruss, Rick

    2014-12-01

    We report secondary eclipse photometry of the hot Jupiter HAT-P-32Ab, taken with Hale/Wide-field Infra-Red Camera (WIRC) in H and KS bands and with Spitzer/IRAC at 3.6 and 4.5 μm. We carried out adaptive optics imaging of the planet host star HAT-P-32A and its companion HAT-P-32B in the near-IR and the visible. We clearly resolve the two stars from each other and find a separation of 2.''923 ± 0.''004 and a position angle 110.°64 ± 0.°12. We measure the flux ratios of the binary in g'r'i'z' and H and KS bands, and determine T eff= 3565 ± 82 K for the companion star, corresponding to an M1.5 dwarf. We use PHOENIX stellar atmosphere models to correct the dilution of the secondary eclipse depths of the hot Jupiter due to the presence of the M1.5 companion. We also improve the secondary eclipse photometry by accounting for the non-classical, flux-dependent nonlinearity of the WIRC IR detector in the H band. We measure planet-to-star flux ratios of 0.090% ± 0.033%, 0.178% ± 0.057%, 0.364% ± 0.016%, and 0.438% ± 0.020% in the H, KS , 3.6 and 4.5 μm bands, respectively. We compare these with planetary atmospheric models, and find they prefer an atmosphere with a temperature inversion and inefficient heat redistribution. However, we also find that the data are equally well described by a blackbody model for the planet with T p = 2042 ± 50 K. Finally, we measure a secondary eclipse timing offset of 0.3 ± 1.3 minutes from the predicted mid-eclipse time, which constrains e = 0.0072+0.0700-0.0064 when combined with radial velocity data and is more consistent with a circular orbit.

  13. FIRST RESULTS FROM THE SWARMS SURVEY. SDSS 1257+5428: A NEARBY, MASSIVE WHITE DWARF BINARY WITH A LIKELY NEUTRON STAR OR BLACK HOLE COMPANION

    SciTech Connect

    Badenes, Carles; Mullally, Fergal; Lupton, Robert H.; Thompson, Susan E. E-mail: mullally@astro.princeton.ed E-mail: sthomp@physics.udel.ed

    2009-12-20

    We present the first results from the SWARMS survey, an ongoing project to identify compact white dwarf (WD) binaries in the spectroscopic catalog of the Sloan Digital Sky Survey (SDSS). The first object identified by SWARMS, SDSS 1257+5428, is a single-lined spectroscopic binary in a circular orbit with a period of 4.56 hr and a semiamplitude of 322.7 +- 6.3 km s{sup -1}. From the spectrum and photometry, we estimate a WD mass of 0.92{sup +0.28}{sub -0.32} M{sub sun}. Together with the orbital parameters of the binary, this implies that the unseen companion must be more massive than 1.62{sup +0.20}{sub -0.25} M{sub sun}, and is in all likelihood either a neutron star or a black hole. At an estimated distance of 48{sup +10}{sub -19} pc, this would be the closest known stellar remnant of a supernova explosion.

  14. CARMENES science preparation: characterisation of M dwarfs with low-resolution spectroscopy and search for low-mass wide companions to young stars

    NASA Astrophysics Data System (ADS)

    Alonso-Floriano, F. J.

    2015-11-01

    This thesis is focused on the study of low-mass objects that can be targets of exoplanet searches with near-infrared spectrographs in general and CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs; see Quirrenbach et al. 2014) in particular. The CARMENES consortium comprises 11 institutions from Germany and Spain that are building a high-resolution spectrograph (R=82,000) with two channels, visible (0.55 - 1.05 um) and infrared (0.95 - 1.7 um), for the 3.5 m Calar Alto telescope. It will observe a sample of 300 M dwarfs in 600 nights of guaranteed time during at least three years, starting in January 2016. The final sample will be chosen from the 2200 M dwarfs included in the CARMENCITA input catalogue. For these stars, we have obtained and collected a large amount of data: spectral types, radial and rotational velocities, photometry in several bands, etc. Part of the e effort of the science preparation necessary for the final selection of targets for CARMENES and other near-infrared spectrographs has been collected in two publications, which are presented in this PhD thesis. In the first publication (Alonso-Floriano et al., 2015A&A...577A.128A), we obtained low-resolution spectra for 753 stars using the CAFOS spectrograph at the 2.2 m Calar Alto telescope. The main goal was to derive accurate spectral types, which are fundamental parameters for the sample selection. We used a grid of 49 standard stars, from spectral types K3V to M8V, together with a double least-square minimisation technique and 31 spectral indices previously defined by other authors. In addition, we quantified the surface gravity, metallicity and chromospheric activity of the sample, in order to detect low-gravity stars (giants and very young), metal-poor and very metal-poor stars (subdwarfs), and very active stars. In the second publication (Alonso-Floriano et al., 2015A&A...583A..85A), we searched for common proper

  15. Double-core evolution. 5: Three-dimensional effects in the merger of a red giant with a dwarf companion

    NASA Technical Reports Server (NTRS)

    Terman, James L.; Taam, Ronald E.; Hernquist, Lars

    1994-01-01

    The evolution of the common envelope phase of a binary system consisting of a 4.67 solar mass red giant and a 0.94 solar mass dwarf is studied using smoothed particle hydrodynamics. We demonstrate that the three-dimensional effects associated with the gravitational tidal torques lead to a rapid decay of the orbit on timescales approximately less than 1 yr. The relative orbit of the two cores in the common envelope is initally eccentric and tends to circularize as the orbital separation of the two cores decreases. The angular momentum lost from the orbital motion is distributed throughout the common envelope, and the double core does not evolve to a state of co-rotation for the evolutionary time followed. The energy dissipated from the relative orbit and deposited in the common envelope results in the ejection of approximately 13% of the mass of the envelope. The mass is ejected in all directions, but there is a preference for mass ejection in the orbital plane of the binary system. For example, approximately 80% of the ejected mass lies within 30 deg of the binary orbital plane. Because gravitational forces are long range, most of the energy and angular momentum is imparted to a small fraction of the common envelope resulting in an efficiency of the mass ejection process of approximately 15%. The core of the red giant executes significant displacement with respect to the center of mass of the system and contributes nearly equally to the total energy dissipation rate during the latter phases of the evolution. The degree of departure from synchronism of the initial binary system can be an important property of the system which can affect the outcome of the common envelope phase.

  16. Hot subdwarfs with degenerate companions

    NASA Astrophysics Data System (ADS)

    Mereghetti, Sandro

    2010-10-01

    Stellar evolutionary models predict that most of the hot sub-dwarfs in close binary systems have white dwarf companions. In a few cases even more massive compact objects (neutron stars or black holes) are suggested by the optical mass functions. The X-ray emission expected from accretion of the sub-dwarf's wind can reveal the nature of the compact companions and be used to derive other important information on these post-common envelope systems, as recently demonstrated by the discovery of a massive WD in HD 49798. We selected 3 promising targets from a sample of hot subdwarfs suspected to have degenerate companions. This proposal was accepted in AO9 with C priority.

  17. VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. V. A LOW ECCENTRICITY BROWN DWARF FROM THE DRIEST PART OF THE DESERT, MARVELS-6b

    SciTech Connect

    De Lee, Nathan; Stassun, Keivan G.; Cargile, Phillip; Ge, Jian; Fleming, Scott W.; Lee, Brian L.; Chang Liang; Crepp, Justin R.; Eastman, Jason; Gaudi, B. Scott; Esposito, Massimiliano; Femenia, Bruno; Gonzalez Hernandez, Jonay I.; Allende Prieto, Carlos; Ghezzi, Luan; Wisniewski, John P.; Wood-Vasey, W. Michael; Agol, Eric; Barnes, Rory; Bizyaev, Dmitry; and others

    2013-06-15

    We describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 {+-} 2.0 M{sub Jup} to GSC 03546-01452 from the MARVELS radial velocity survey, which we designate as MARVELS-6b. For reasonable priors, our analysis gives a probability of 72% that MARVELS-6b has a mass below the hydrogen-burning limit of 0.072 M{sub Sun }, and thus it is a high-confidence BD companion. It has a moderately long orbital period of 47.8929{sup +0.0063}{sub -0.0062} days with a low eccentricity of 0.1442{sup +0.0078}{sub -0.0073}, and a semi-amplitude of 1644{sup +12}{sub -13} m s{sup -1}. Moderate resolution spectroscopy of the host star has determined the following parameters: T{sub eff} = 5598 {+-} 63, log g = 4.44 {+-} 0.17, and [Fe/H] = +0.40 {+-} 0.09. Based upon these measurements, GSC 03546-01452 has a probable mass and radius of M{sub *} = 1.11 {+-} 0.11 M{sub Sun} and R{sub *} = 1.06 {+-} 0.23 R{sub Sun} with an age consistent with less than {approx}6 Gyr at a distance of 219 {+-} 21 pc from the Sun. Although MARVELS-6b is not observed to transit, we cannot definitively rule out a transiting configuration based on our observations. There is a visual companion detected with Lucky Imaging at 7.''7 from the host star, but our analysis shows that it is not bound to this system. The minimum mass of MARVELS-6b exists at the minimum of the mass functions for both stars and planets, making this a rare object even compared to other BDs. It also exists in an underdense region in both period/eccentricity and metallicity/eccentricity space.

  18. SEARCHING FOR YOUNG M DWARFS WITH GALEX

    SciTech Connect

    Shkolnik, Evgenya L.; Weinberger, Alycia J.; Liu, Michael C.; Dupuy, Trent; Reid, I. Neill E-mail: alycia@dtm.ciw.edu E-mail: tdupuy@ifa.hawaii.edu

    2011-01-20

    The census of young moving groups in the solar neighborhood is significantly incomplete in the low-mass regime. We have developed a new selection process to find these missing members based on the Galaxy Evolution Explorer (GALEX) All-Sky Imaging Survey (AIS). For stars with spectral types {approx}>K5 (R - J {approx}> 1.5) and younger than {approx}300 Myr, we show that near-UV (NUV) and far-UV (FUV) emission is greatly enhanced above the quiescent photosphere, analogous to the enhanced X-ray emission of young low-mass stars seen by ROSAT but detectable to much larger distances with GALEX. By combining GALEX data with optical (HST Guide Star Catalog) and near-IR (2MASS) photometry, we identified an initial sample of 34 young M dwarf candidates in a 1000 deg{sup 2} region around the {approx}10 Myr TW Hydra Association (TWA). Low-resolution spectroscopy of 30 of these found 16 which had H{alpha} in emission, which were then followed up at high resolution to search for spectroscopic evidence of youth and to measure their radial velocities. Four objects have low surface gravities, photometric distances and space motions consistent with TWA, but the non-detection of Li indicates that they may be too old to belong to this moving group. One object (M3.5, 93 {+-} 19 pc) appears to be the first known accreting low-mass member of the {approx}15 Myr Lower Centaurus Crux OB association. Two objects exhibit all the characteristics of the known TWA members, and thus we designate them as TWA 31 (M4.2, 110 {+-} 11 pc) and TWA 32 (M6.3, 53 {+-} 5 pc). TWA 31 shows extremely broad (447 km s{sup -1}) H{alpha} emission, making it the sixth member of TWA found to have ongoing accretion. TWA 32 is resolved into a 0.''6 binary in Keck laser guide star adaptive optics imaging. Our search should be sensitive down to spectral types of at least M4-M5 in TWA and thus the small numbers of new member is puzzling. This might indicate TWA has an atypical mass function or that the presence of

  19. The physical characteristics of surface Earth-like planets, dwarf and small (asteroids) planets, and their companions, according to distance studies

    NASA Astrophysics Data System (ADS)

    Vidmachenko, A. P.; Morozhenko, O. V.

    2014-01-01

    The history of exploration and cosmogony of Solar System bodies, the current state of the planetary cosmogony, the process of formation planets and their satellites; the features of the internal structure of terrestrial planets and of the Moon, magnetic fields of the terrestrial planets, satellites and asteroids; the general question of forming of diffusely reflected radiation of rough surfaces, lighting conditions, the parameters of reflected radiation fields (photometric, polarization and thermal properties), radar observations was considered. Given the main results of the study of the Moon, Earth-like planets (Mars, Mercury, Venus) dwarf and small (asteroids) planets Publication is targeted for teachers of higher educational institutions, students and graduate students and specialists who specialize in the study of physical methods, experimental physics and solar system bodies

  20. X-Rays Found From a Lightweight Brown Dwarf

    NASA Astrophysics Data System (ADS)

    2003-04-01

    Using NASA's Chandra X-ray Observatory, scientists have detected X-rays from a low mass brown dwarf in a multiple star system, which is as young as 12 million years old. This discovery is an important piece in an increasingly complex picture of how brown dwarfs - and perhaps the very massive planets around other stars - evolve. Chandra's observations of the brown dwarf, known as TWA 5B, clearly resolve it from a pair of Sun-like stars known as TWA 5A. The system is about 180 light years from the Sun and a member of a group of about a dozen young stars in the southern constellation Hydra. The brown dwarf orbits the binary stars at a distance about 2.75 times that of Pluto's orbit around the Sun. This is first time that a brown dwarf this close to its parent star(s) has been resolved in X-rays. "Our Chandra data show that the X-rays originate from the brown dwarf's coronal plasma which is some 3 million degrees Celsius," said Yohko Tsuboi of Chuo University in Tokyo and lead author of the April 10th issue of Astrophysical Journal Letters paper describing these results. "The brown dwarf is sufficiently far from the primary stars that the reflection of X-rays is unimportant, so the X-rays must come the brown dwarf itself." TWA 5B is estimated to be only between 15 and 40 times the mass of Jupiter, making it one of the least massive brown dwarfs known. Its mass is rather near the currently accepted boundary (about 12 Jupiter masses) between planets and brown dwarfs. Therefore, these results may also have implications for very massive planets, including those that have been discovered as extrasolar planets in recent years. Brown Dwarf size comparison schematic Brown Dwarf size comparison schematic "This brown dwarf is as bright as the Sun today in X-ray light, while it is fifty times less massive than the Sun," said Tsuboi. "This observation, thus, raises the possibility that even massive planets might emit X-rays by themselves during their youth!" This research on TWA 5

  1. Measuring M Dwarf Winds with DAZ White Dwarfs

    NASA Astrophysics Data System (ADS)

    Debes, John H.

    2006-11-01

    Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, show evidence for ongoing accretion of material onto their surfaces. Some DAZs are known to have unresolved M dwarf companions, which could account for the observed accretion through a stellar wind. I combine observed Ca abundances of the DAZs with information on the orbital separation of their M dwarf companions to infer the mass-loss rate of the M dwarfs. I find that for three of the six known DAZs with M dwarf companions, a stellar wind can plausibly explain the observed accretion on the white dwarfs assuming Bondi-Hoyle accretion of solar abundance stellar winds on the order of 10-14 to 10-16 Msolar yr-1. The rest of the sample have companions with orbits >~1 AU and require companion mass-loss rates of >10-11 Msolar yr-1. I conclude that there must be an alternative explanation for accretion of material onto DAZs with widely separated companions. The inferred winds for two of the close binaries are orders of magnitude smaller than typically assumed for the angular momentum loss of red dwarf-white dwarf pairs due to magnetic braking from a stellar wind and may seriously affect predictions for the formation rate of CVs with low-mass companions. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program 10255.

  2. BEER Analysis of Kepler and CoRoT Light Curves. IV. Discovery of Four New Low-mass White-Dwarf Companions in the Kepler Data

    NASA Astrophysics Data System (ADS)

    Faigler, S.; Kull, I.; Mazeh, T.; Kiefer, F.; Latham, D. W.; Bloemen, S.

    2015-12-01

    We report the discovery of four short-period eclipsing systems in the Kepler light curves, consisting of an A-star primary and a low-mass white dwarf (WD) secondary (dA+WD)—KIC 4169521, KOI-3818, KIC 2851474, and KIC 9285587. The systems show BEaming, Ellipsoidal and Reflection (BEER) phase modulations together with primary and secondary eclipses. These add to the 6 Kepler and 18 WASP short-period eclipsing dA+WD binaries that were previously known. The light curves, together with follow-up spectroscopic observations, allow us to derive the masses, radii, and effective temperatures of the two components of the four systems. The orbital periods, of 1.17-3.82 days, and WD masses, of 0.19-0.22 M⊙, are similar to those of the previously known systems. The WD radii of KOI-3818, KIC 2851474, and KIC 9285587 are 0.026, 0.035, and 0.026 R⊙, respectively, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries. These three binaries extend the previously known population to older systems with cooler and smaller WD secondaries. KOI-3818 displays evidence for a fast-rotating primary and a minute but significant eccentricity, ˜1.5 × 10-3. These features are probably the outcome of the mass-transfer process.

  3. Synthesizing Exoplanet Demographics: A Single Population of Long-period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys

    NASA Astrophysics Data System (ADS)

    Clanton, Christian; Gaudi, B. Scott

    2016-03-01

    We present the first study to synthesize results from five different exoplanet surveys using three independent detection methods: microlensing, radial velocity, and direct imaging. The constraints derived herein represent the most comprehensive picture of the demographics of large-separation (≳2 AU) planets orbiting the most common stars in our Galaxy that has been constructed to date. We assume a simple, joint power-law planet distribution function of the form {d}2{N}{{pl}}/(d{log} {m}p d{log} a)={ A }{({m}p/{M}{{Sat}})}α {(a/2.5{{AU}})}β with an outer cutoff radius of the separation distribution function of aout. Generating populations of planets from these models and mapping them into the relevant observables for each survey, we use actual or estimated detection sensitivities to determine the expected observations for each survey. Comparing with the reported results, we derive constraints on the parameters \\{α ,β ,{ A },{a}{{out}}\\} that describe a single population of planets that is simultaneously consistent with the results of microlensing, radial velocity, and direct imaging surveys. We find median and 68% confindence intervals of α =-{0.86}-0.19+0.21 (-{0.85}-0.19+0.21), β ={1.1}-1.4+1.9 ({1.1}-1.3+1.9), { A }={0.21}-0.15+0.20 {{dex}}-2 ({0.21}-0.15+0.20 {{dex}}-2), and {a}{{out}}={10}-4.7+26 AU ({12}-6.2+50 AU) assuming “hot-start” (“cold-start”) planet evolutionary models. These values are consistent with all current knowledge of planets on orbits beyond ∼2 AU around single M dwarfs.

  4. Wide cool and ultracool companions to nearby stars from Pan-STARRS 1

    SciTech Connect

    Deacon, Niall R.; Liu, Michael C.; Magnier, Eugene A.; Aller, Kimberly M.; Best, William M. J.; Bowler, Brendan P.; Burgett, William S.; Chambers, Kenneth C.; Flewelling, H.; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S.; Tonry, John L.; Dupuy, Trent; Mann, Andrew W.; Redstone, Joshua A.; Draper, Peter W.; Metcalfe, Nigel; Hodapp, Klaus W.; Price, Paul A.; and others

    2014-09-10

    We present the discovery of 57 wide (>5'') separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS 1 (PS1) data and the spectral classification of 31 previously known companions. Our companions represent a selective subsample of promising candidates and span a range in spectral type of K7-L9 with the addition of one DA white dwarf. These were identified primarily from a dedicated common proper motion search around nearby stars, along with a few as serendipitous discoveries from our Pan-STARRS 1 brown dwarf search. Our discoveries include 23 new L dwarf companions and one known L dwarf not previously identified as a companion. The primary stars around which we searched for companions come from a list of bright stars with well-measured parallaxes and large proper motions from the Hipparcos catalog (8583 stars, mostly A-K dwarfs) and fainter stars from other proper motion catalogs (79170 stars, mostly M dwarfs). We examine the likelihood that our companions are chance alignments between unrelated stars and conclude that this is unlikely for the majority of the objects that we have followed-up spectroscopically. We also examine the entire population of ultracool (>M7) dwarf companions and conclude that while some are loosely bound, most are unlikely to be disrupted over the course of ∼10 Gyr. Our search increases the number of ultracool M dwarf companions wider than 300 AU by 88% and increases the number of L dwarf companions in the same separation range by 82%. Finally, we resolve our new L dwarf companion to HIP 6407 into a tight (0.''13, 7.4 AU) L1+T3 binary, making the system a hierarchical triple. Our search for these key benchmarks against which brown dwarf and exoplanet atmosphere models are tested has yielded the largest number of discoveries to date.

  5. Wide Cool and Ultracool Companions to Nearby Stars from Pan-STARRS 1

    NASA Astrophysics Data System (ADS)

    Deacon, Niall R.; Liu, Michael C.; Magnier, Eugene A.; Aller, Kimberly M.; Best, William M. J.; Dupuy, Trent; Bowler, Brendan P.; Mann, Andrew W.; Redstone, Joshua A.; Burgett, William S.; Chambers, Kenneth C.; Draper, Peter W.; Flewelling, H.; Hodapp, Klaus W.; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S.; Metcalfe, Nigel; Price, Paul A.; Tonry, John L.; Wainscoat, Richard J.

    2014-09-01

    We present the discovery of 57 wide (>5'') separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS 1 (PS1) data and the spectral classification of 31 previously known companions. Our companions represent a selective subsample of promising candidates and span a range in spectral type of K7-L9 with the addition of one DA white dwarf. These were identified primarily from a dedicated common proper motion search around nearby stars, along with a few as serendipitous discoveries from our Pan-STARRS 1 brown dwarf search. Our discoveries include 23 new L dwarf companions and one known L dwarf not previously identified as a companion. The primary stars around which we searched for companions come from a list of bright stars with well-measured parallaxes and large proper motions from the Hipparcos catalog (8583 stars, mostly A-K dwarfs) and fainter stars from other proper motion catalogs (79170 stars, mostly M dwarfs). We examine the likelihood that our companions are chance alignments between unrelated stars and conclude that this is unlikely for the majority of the objects that we have followed-up spectroscopically. We also examine the entire population of ultracool (>M7) dwarf companions and conclude that while some are loosely bound, most are unlikely to be disrupted over the course of ~10 Gyr. Our search increases the number of ultracool M dwarf companions wider than 300 AU by 88% and increases the number of L dwarf companions in the same separation range by 82%. Finally, we resolve our new L dwarf companion to HIP 6407 into a tight (0.''13, 7.4 AU) L1+T3 binary, making the system a hierarchical triple. Our search for these key benchmarks against which brown dwarf and exoplanet atmosphere models are tested has yielded the largest number of discoveries to date.

  6. REVEALING COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION

    SciTech Connect

    Tokovinin, Andrei; Hartung, Markus; Hayward, Thomas L.; Makarov, Valeri V. E-mail: mhartung@gemini.edu E-mail: valeri.makarov@usno.navy.mil

    2012-07-15

    A subset of 51 Hipparcos astrometric binaries among FG dwarfs within 67 pc has been surveyed with the Near-Infrared Coronagraphic Imager adaptive optics system at Gemini-S, directly resolving for the first time 17 subarcsecond companions and 7 wider ones. Using these data together with published speckle interferometry of 57 stars, we compare the statistics of resolved astrometric companions with those of a simulated binary population. The fraction of resolved companions is slightly lower than expected from binary statistics. About 10% of astrometric companions could be 'dark' (white dwarfs and close pairs of late M-dwarfs). To our surprise, several binaries are found with companions too wide to explain the acceleration. Re-analysis of selected intermediate astrometric data shows that some acceleration solutions in the original Hipparcos catalog are spurious.

  7. Effects of the TWA Strategy on Expository Reading Comprehension of Students with Autism

    ERIC Educational Resources Information Center

    Howorth, Sarah; Lopata, Christopher; Thomeer, Marcus; Rodgers, Jonathan

    2016-01-01

    High-functioning students with autism spectrum disorder (ASD) have been shown to have significant reading comprehension difficulty. This multiple baseline study examined the effect of the think before reading, think while reading, and think after reading (TWA) strategy on expository text comprehension of four boys with ASD. Following baseline,…

  8. Overlooked wide companions of nearby F stars

    NASA Astrophysics Data System (ADS)

    Scholz, R.-D.

    2016-03-01

    Aims: We checked a sample of 545 F stars within 50 pc for wide companions using existing near-infrared and optical sky surveys. Methods: Applying the common proper motion (CPM) criterion, we detected wide companion candidates with 6-120 arcsec angular separations by visual inspection of multi-epoch finder charts and by searching in proper motion catalogues. Final proper motions were measured by involving positional measurements from up to eleven surveys. Spectral types of red CPM companions were estimated from their absolute J-band magnitudes based on the Hipparcos distances of the primaries. Results: In addition to about 100 known CPM objects, we found 19 new CPM companions and confirmed 31 previously known candidates. A few CPM objects are still considered as candidates according to their level of proper motion agreement. Among the new objects there are nine M0-M4, eight M5-M6, one ≈L3.5 dwarf (HD 3861B), and one white dwarf (WD) (HD 2726B), whereas we confirmed two K, 19 M0-M4, six M5-M6, two early-L dwarfs, and two DA WDs as CPM companions. In a few cases, previous spectral types were available that all agree well with our estimates. Two companions (HD 22879B and HD 49933B) are associated with moderately metal-poor Gaia benchmark stars. One doubtful CPM companion, spectroscopically classified as WD but found to be very bright (J = 11.1) by others, should either be a very nearby foreground WD or a different kind of object associated with HD 165670. Tables A.1, B.1, and C.1 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A51

  9. COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION. II

    SciTech Connect

    Tokovinin, Andrei; Hartung, Markus; Hayward, Thomas L. E-mail: mhartung@gemini.edu

    2013-07-01

    Hipparcos astrometric binaries were observed with the NICI adaptive optics system at Gemini-S, completing the work of Paper I. Among the 65 F, G, and K dwarfs within 67 pc of the Sun studied here, we resolve 18 new subarcsecond companions, remeasure 7 known astrometric pairs, and establish the physical nature of yet another 3 wider companions. The 107 astrometric binaries targeted at Gemini so far have 38 resolved companions with separations under 3''. Modeling shows that bright enough companions with separations on the order of an arcsecond can perturb the Hipparcos astrometry when they are not accounted for in the data reduction. However, the resulting bias of parallax and proper motion is generally below formal errors and such companions cannot produce fake acceleration. This work contributes to the multiplicity statistics of nearby dwarfs by bridging the gap between spectroscopic and visual binaries and by providing estimates of periods and mass ratios for many astrometric binaries.

  10. Rumen fermentation and acetogen population changes in response to an exogenous acetogen TWA4 strain and Saccharomyces cerevisiae fermentation product*

    PubMed Central

    Yang, Chun-lei; Guan, Le-luo; Liu, Jian-xin; Wang, Jia-kun

    2015-01-01

    The presence of yeast cells could stimulate hydrogen utilization of acetogens and enhance acetogenesis. To understand the roles of acetogens in rumen fermentation, an in vitro rumen fermentation experiment was conducted with addition of acetogen strain (TWA4) and/or Saccharomyces cerevisiae fermentation product (XP). A 2×2 factorial design with two levels of TWA4 (0 or 2×107 cells/ml) and XP (0 or 2 g/L) was performed. Volatile fatty acids (VFAs) were increased (P<0.05) in XP and TWA4XP, while methane was increased only in TWA4XP (P<0.05). The increase rate of microorganisms with formyltetrahydrofolate synthetase, especially acetogens, was higher than that of methanogens under all treatments. Lachnospiraceae was predominant in all acetogen communities, but without close acetyl-CoA synthase (ACS) amino acid sequences from cultured isolates. Low-Acetitomaculum ruminis-like ACS was predominant in all acetogen communities, while four unique phylotypes in XP treatment were all amino acid identified low-Eubacterium limosum-like acetogens. It differs to XP treatment that more low-A. ruminis-like and less low-E. limosum-like sequences were identified in TWA4 and TWA4XP treatments. Enhancing acetogenesis by supplementation with an acetogen strain and/or yeast cells may be an approach to mitigate methane, by targeting proper acetogens such as uncultured low-E. limosum-like acetogens. PMID:26238546

  11. Evidence for a solar companion star

    SciTech Connect

    Muller, R.A.

    1984-08-01

    Periodicity seen in both the mass extinctions and large impact cratering on earth can be explained if one postulates that the sun has a companion star, orbiting in a moderately eccentric orbit with a major axis of 2.8 light-years. No other explanations that have been suggested are compatible with known facts of physics and astronomy. If the companion is a red dwarf star, the most common kind in the galaxy, then no previous astronomical observations would have found it. A search for red objects with large parallax is now underway at Berkeley, and has a good chance of identifying the star in the near future.

  12. WHITE DWARF-RED DWARF SYSTEMS RESOLVED WITH THE HUBBLE SPACE TELESCOPE. II. FULL SNAPSHOT SURVEY RESULTS

    SciTech Connect

    Farihi, J.; Hoard, D. W.; Wachter, S.

    2010-10-15

    Results are presented for a Hubble Space Telescope Advanced Camera for Surveys high-resolution imaging campaign of 90 white dwarfs with known or suspected low-mass stellar and substellar companions. Of the 72 targets that remain candidate and confirmed white dwarfs with near-infrared excess, 43 are spatially resolved into two or more components, and a total of 12 systems are potentially triples. For 68 systems where a comparison is possible, 50% have significant photometric distance mismatches between their white dwarf and M dwarf components, suggesting that white dwarf parameters derived spectroscopically are often biased due to the cool companion. Interestingly, 9 of the 30 binaries known to have emission lines are found to be visual pairs and hence widely separated, indicating an intrinsically active cool star and not irradiation from the white dwarf. There is a possible, slight deficit of earlier spectral types (bluer colors) among the spatially unresolved companions, exactly the opposite of expectations if significant mass is transferred to the companion during the common envelope phase. Using the best available distance estimates, the low-mass companions to white dwarfs exhibit a bimodal distribution in projected separation. This result supports the hypothesis that during the giant phases of the white dwarf progenitor, any unevolved companions either migrate inward to short periods of hours to days, or outward to periods of hundreds to thousands of years. No intermediate projected separations of a few to several AU are found among these pairs. However, a few double M dwarfs (within triples) are spatially resolved in this range, empirically demonstrating that such separations were readily detectable among the binaries with white dwarfs. A straightforward and testable prediction emerges: all spatially unresolved, low-mass stellar and substellar companions to white dwarfs should be in short-period orbits. This result has implications for substellar companion and

  13. Common Proper Motion Companions to Nearby Stars: Ages and Evolution

    NASA Astrophysics Data System (ADS)

    Makarov, V. V.; Zacharias, N.; Hennessy, G. S.

    2008-11-01

    A set of 41 nearby stars (closer than 25 pc) is investigated which have very wide binary and common proper motion (CPM) companions at projected separations between 1000 and 200,000 AU. These companions are identified by astrometric positions and proper motions from the NOMAD catalog. Based mainly on measures of chromospheric and X-ray activity, age estimation is obtained for most of 85 identified companions. Color-absolute magnitude diagrams are constructed to test whether CPM companions are physically related to the primary nearby stars and have the same age. Our carefully selected sample includes three remote white dwarf companions to main-sequence stars and two systems (55 Cnc and GJ 777A) of multiple planets and distant stellar companions. Ten new CPM companions, including three of extreme separations, are found. Multiple hierarchical systems are abundant; more than 25% of CPM components are spectroscopic or astrometric binaries or multiples themselves. Two new astrometric binaries are discovered among nearby CPM companions, GJ 264 and HIP 59000, and preliminary orbital solutions are presented. The Hyades kinematic group (or stream) is presented broadly in the sample, but we find few possible thick-disk objects and no halo stars. It follows from our investigation that moderately young (age lesssim 1 Gyr) thin-disk dwarfs are the dominating species in the near CPM systems, in general agreement with the premises of the dynamical survival paradigm.

  14. A continuing search for companions to PRG stars

    NASA Technical Reports Server (NTRS)

    Johnson, Hollis R.; Ake, Thomas B.; Ameen, Mudhaffer M.; Brown, Jeffery A.

    1990-01-01

    Results are presented from observations, made with the SWP spectrograph at low resolution, of Tc-deficient S and C members of the group of chemically peculiar red giant (PRG) stars, which were carried out to search for possible companions to these stars. The results support the hypothesis of Little et al. (1987) and Smith and Lambert (1987, 1988) that the chemical peculiarities of T-deficient S and MS PRG stars have arisen due to mass transfer from white dwarf companions.

  15. Substellar companions to white dwarves

    NASA Astrophysics Data System (ADS)

    Mullally, Fergal Robert

    2007-08-01

    We search for planets and brown dwarves around white dwarves (WDs). Finding extra-solar planets is the first step toward establishing the existence and abundance of life in the Universe. The low mass and luminosity of WDs make them ideal stars to search for low mass companion objects. Theoretical predictions generally agree that a star will consume and destroy close-in, low mass planets as it ascends the red giant and asymptotic giant branch evolutionary tracks, but larger mass objects and those further out will survive. The matter ejected from the star as it evolves into a white dwarf may also be accreted onto daughter planets, or may coalesce into a disk from which planets can then form. We employ two techniques to search for planets and brown dwarves (BDs) around WDs. A subset of pulsating white dwarf stars have a pulsational stability that rivals pulsars and atomic clocks. When a planet is in orbit around a such a star the orbital motion of the star around the centre of mass is detectable as a change in arrival times of the otherwise stable pulsations. We search for, and find, a sample of suitable pulsators, monitor them for between three and four years, and place limits on companions by constraining the variation in the pulse arrival times. For one star, we detect a variation consistent with a 2.4M J planet in a 4.6 year orbit. We also observe a large sample of WDs to search for a mid-infrared excess caused by the presence of sub-stellar companions. We present evidence for a potential binary system consisting of a WD and a BD on the basis of an observed excess flux at near and mid-infrared wavelengths. We also place limits on the presence of planetary mass companions around these stars and compare our results to predictions of planetary survival theories. Our findings do not support suggestions of planet formation or accretion of extra mass during stellar death.

  16. Calibrating brown dwarf ages using white dwarfs in wide binaries

    NASA Astrophysics Data System (ADS)

    Catalán, S.

    Even though age is a critical parameter for all objects, it can also be one of the most difficult to measure, in particular for low-mass stars and brown dwarfs. Brown dwarf models suffer from degeneracy and are not useful to infer ages without well constrained atmospheric parameters \\citep{pin06}. However, there is a way to overcome this problem by studying brown dwarfs for which some external constraints are available, for example brown dwarfs in wide binary systems. Wide binary members share proper motion and are supposed to have been born simultaneously and with the same chemical composition. Since they are well separated (⪆ 1000 AU) we can assume that no interaction has occurred between them in the past and they have evolved as isolated objects. If the companion of the brown dwarfs is a white dwarf, we can use it to calibrate the age of the system. White dwarf evolution can be described as a cooling process which is relatively well understood \\citep[e.g.][]{sal00}. Thus, they yield robust age constraints from the use of cooling sequences \\citep{gar11}. White dwarf cooling ages will uniformally give age lower limits (despite some uncertainty on progenitor life-time), and in some cases yield ages to better than 10% accuracy. Hence, wide binary systems containing a white dwarf can have system age constraints inferred from the white dwarf component. There are not many white dwarf-brown dwarf systems known so far, but with the combination of optical and IR surveys, SDSS+UKIDSS and Gaia + UKIDSS/VHS, new systems will be detected.

  17. [An algorithm for detecting T-wave alternans (TWA) based on the maximum of T-waves].

    PubMed

    Zhao, Jie; Hua, Mei

    2005-10-01

    An algorithm of detecting the TWA (T-wave alternans) based on the maximum of T waves transformed by FFT (Fast Fourier Transform) is described in the paper. By using the method we can reduce the sampling rate, which means "smaller amount of calculation", and solve the problem "the sampling point of T wave changes with the rate of heart beat". The 128 maximum values of T wave in series normal ST-T complex are used to carry out FFT transforms. The TWA is detected by using the frequency of power spectrum. PMID:16294729

  18. A SUBSTELLAR COMPANION TO THE DUSTY PLEIADES STAR HD 23514

    SciTech Connect

    Rodriguez, David R.; Zuckerman, B.; Marois, Christian; Macintosh, Bruce; Melis, Carl

    2012-03-20

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

  19. A method for selecting M dwarfs with an increased likelihood of unresolved ultracool companionship

    NASA Astrophysics Data System (ADS)

    Cook, N. J.; Pinfield, D. J.; Marocco, F.; Burningham, B.; Jones, H. R. A.; Frith, J.; Zhong, J.; Luo, A. L.; Qi, Z. X.; Lucas, P. W.; Gromadzki, M.; Day-Jones, A. C.; Kurtev, R. G.; Guo, Y. X.; Wang, Y. F.; Bai, Y.; Yi, Z. P.; Smart, R. L.

    2016-04-01

    Locating ultracool companions to M dwarfs is important for constraining low-mass formation models, the measurement of substellar dynamical masses and radii, and for testing ultracool evolutionary models. We present an optimized method for identifying M dwarfs which may have unresolved ultracool companions. We construct a catalogue of 440 694 M dwarf candidates, from Wide-Field Infrared Survey Explorer, Two Micron All-Sky Survey and Sloan Digital Sky Survey, based on optical- and near-infrared colours and reduced proper motion. With strict reddening, photometric and quality constraints we isolate a subsample of 36 898 M dwarfs and search for possible mid-infrared M dwarf + ultracool dwarf candidates by comparing M dwarfs which have similar optical/near-infrared colours (chosen for their sensitivity to effective temperature and metallicity). We present 1082 M dwarf + ultracool dwarf candidates for follow-up. Using simulated ultracool dwarf companions to M dwarfs, we estimate that the occurrence of unresolved ultracool companions amongst our M dwarf + ultracool dwarf candidates should be at least four times the average for our full M dwarf catalogue. We discuss possible contamination and bias and predict yields of candidates based on our simulations.

  20. Exceptional Stars Origins, Companions, Masses and Planets

    NASA Technical Reports Server (NTRS)

    Kulkarni, Shrinivas R.; Hansen, Bradley M. S.; Phinney, Sterl; vanKerkwijk, Martin H.; Vasisht, Gautam

    2004-01-01

    As SIM Interdisciplinary Scientist, we will study the formation, nature and planetary companions of the exotic endpoints of stellar evolution. Our science begins with stars evolving from asymptotic branch giants into white dwarfs. We will determine the parallax and orbital inclination of several iron-deficient post-AGB stars, who peculiar abundances and infrared excesses are evidence that they are accreting gas depleted of dust from a circumbinary disk. Measurement of the orbital inclination, companion mass arid parallax will provide critical constraints. One of these stars is a prime candidate for trying nulling observations, which should reveal light reflected from both the circumbinary and Roche disks. The circumbinary disks seem favorable sites for planet formation. Next, we will search for planets around white dwarfs, both survivors froni the main-sequence stage, and ones newly formed from the circumbinary disks of post-AGB binaries or in white dwarf mergers. Moving up in mass, we will measure the orbital reflex of OB/Be companions to pulsars, determine natal kicks and presupernova orbits, and expand the sample of well-determined neutron star masses. We will obtain the parallax of a transient X-ray binary, whose quiescent emission may be thermal emission from the neutron star, aiming for precise measurement of the neutron star radius. Finally, black holes. We will measure the reflex motions of the companion of what appear to be the most massive stellar black holes. The visual orbits will determine natal kicks, and test the assumptions underlying mass estimates made from the radial velocity curves, projected rotation, and ellipsoidal variations. In addition, we will attempt to observe the visual orbit of SS 433, as well as the proper motion of the emission line clumps in its relativistic jets. Additional information is included in the original document.

  1. Terrorism on the Evening News: An Analysis of Coverage of the TWA Hostage Crisis on "NBC Nightly News."

    ERIC Educational Resources Information Center

    Atwater, Tony

    Noting that television network coverage of hostage crises tends to emphasize the same topics while depicting them in similar ways, and that networks may be unwittingly granting legitimacy to terrorist grievances, a study investigated the nature of "NBC Nightly News" coverage of the Trans World Airline (TWA) hostage crisis. Specific questions…

  2. The Construction, Enactment, and Maintenance of Power-as-Domination through an Acquisition: The Case of TWA and Ozark Airlines.

    ERIC Educational Resources Information Center

    Pierce, Tamyra; Dougherty, Debbie S.

    2002-01-01

    Explores how domination was created, enacted, and maintained in the acquisition of Ozark Airlines by TWA. Uses the concepts of resources, hegemony, and resistance from the functionalist, Marxist, and postmodern traditions, respectively, to understand power-as-domination as a complex communication process. Reveals how communication practices were…

  3. Detection of a compact companion of the mild barium star Xi-1 Ceti

    NASA Technical Reports Server (NTRS)

    Bohm-Vitense, E.; Johnson, H. R.

    1985-01-01

    In the present paper, the observation of a white dwarf companion of the mild Ba star Xi-1 Ceti (= 65 Ceti = HR 649 = HD 13611) is reported, taking into account also the properties of the mild Ba star and of its companion. The UV spectrum of Xi-1 Ceti is discussed along with an interpretation of this spectrum. Attention is given to the effective temperature of the companion, the absorption bands in the spectrum, the radius and mass of the Xi-1 Ceti companion, and questions regarding the obscuration of the companion by the atmosphere of the Ba star. It is found that the overall energy distribution of the Xi-1 Ceti companion can best be matched with a 14,000 K DA white dwarf of log g = 8 or less. However, the absolute intensity is too small and would require a radius too small and a mass too large for such a gravity.

  4. No surviving evolved companions of the progenitor of SN 1006.

    PubMed

    González Hernández, Jonay I; Ruiz-Lapuente, Pilar; Tabernero, Hugo M; Montes, David; Canal, Ramon; Méndez, Javier; Bedin, Luigi R

    2012-09-27

    Type Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type Ia supernovae, but the relative proportions of their contributions remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572 (refs 8, 9), although that has been questioned. More recently, observations have restricted surviving companions to be small, main-sequence stars, ruling out giant companions but still allowing the single-degenerate channel. Here we report the results of a search for surviving companions of the progenitor of SN 1006 (ref. 14). None of the stars within 4 arc minutes of the apparent site of the explosion is associated with the supernova remnant, and we can firmly exclude all giant and subgiant stars from being companions of the progenitor. In combination with previous results, our findings indicate that fewer than 20 per cent of type Ia supernovae occur through the single-degenerate channel. PMID:23018963

  5. No surviving evolved companions of the progenitor of SN 1006

    NASA Astrophysics Data System (ADS)

    González Hernández, Jonay I.; Ruiz-Lapuente, Pilar; Tabernero, Hugo M.; Montes, David; Canal, Ramon; Méndez, Javier; Bedin, Luigi R.

    2012-09-01

    Type Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type Ia supernovae, but the relative proportions of their contributions remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572 (refs 8, 9), although that has been questioned. More recently, observations have restricted surviving companions to be small, main-sequence stars, ruling out giant companions but still allowing the single-degenerate channel. Here we report the results of a search for surviving companions of the progenitor of SN 1006 (ref. 14). None of the stars within 4 arc minutes of the apparent site of the explosion is associated with the supernova remnant, and we can firmly exclude all giant and subgiant stars from being companions of the progenitor. In combination with previous results, our findings indicate that fewer than 20 per cent of type Ia supernovae occur through the single-degenerate channel.

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

    PubMed

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

    2006-08-01

    Many sub-stellar companions (usually planets but also some brown dwarfs) orbit solar-type stars. These stars can engulf their sub-stellar companions when they become red giants. This interaction may explain several outstanding problems in astrophysics but it is unclear under what conditions a low mass companion will evaporate, survive the interaction unchanged or gain mass. Observational tests of models for this interaction have been hampered by a lack of positively identified remnants-that is, white dwarf stars with close, sub-stellar companions. The companion to the pre-white dwarf AA Doradus may be a brown dwarf, but the uncertain history of this star and the extreme luminosity difference between the components make it difficult to interpret the observations or to put strong constraints on the models. The magnetic white dwarf SDSS J121209.31 + 013627.7 may have a close brown dwarf companion but little is known about this binary at present. Here we report the discovery of a brown dwarf in a short period orbit around a white dwarf. The properties of both stars in this binary can be directly observed and show that the brown dwarf was engulfed by a red giant but that this had little effect on it. PMID:16885979

  7. The search for companions to Epsilon Eridani.

    PubMed

    Lawton, A T; Wright, P

    1990-12-01

    The authors review efforts to examine the star Epsilon Eridani and determine the possibility for the existence of an Earth-like planet. Early data indicated that there must be a habitable ecosphere about 82.5 million Km from the primary. Research into the existence of another planetary system determined that Epsilon Eridani was a binary star with an Oort cloud system, indicating the possibility of planet formation. A review of the evidence suggests that the presence of the small red Dwarf companion star precludes the existence of a planetary system surrounding Epsilon Eridani. It is suggested that observations continue to provide further data about the formation of binary systems. PMID:11540498

  8. A Combustion Model for the TWA 800 Center-Wing Fuel Tank Explosion

    SciTech Connect

    Baer, M.R.; Gross, R.J.

    1998-10-02

    In support of the National Transportation Safety Board investigation of the TWA Flight 800 accident, a combined experimental/computational effort was conducted that focused on quarter-scale testing and simulation of the fuel-air explosion in the Boeing 747 center wing fuel tank. This report summarizes the modeling approach used at Sandia National Laboratories. In this approach approximations are introduced that capture the essential physics associated with turbulent flame propagation in multiple compartment fuel tanks. This model efficiently defines the pressure loading conditions during a jet-fuel air explosion in a fuel tank confinement. Modeling calculations compare favorably with a variety of experimental quarter-scale tests conducted in rigid confinement. The modeling describes well the overpressure history in several geometry configurations. Upon demonstrating a reasonable comparison to experimental observations, a parametric study of eight possible ignition sources is then discussed. Model calculations demonstrate that different loading conditions arise as the location of the ignition event is varied. By comparing the inferred damage and calculated impulses to that seen in the recovered tank, it maybe possible to reduce the number of likely sources. A possible extension of this work to better define tank damage includes coupling the combustion model as a pressure loading routine for structural failure analysis.

  9. Astronomy: Tycho's mystery companion

    NASA Astrophysics Data System (ADS)

    Branch, David

    2004-10-01

    A famous sixteenth century supernova, seen by Tycho Brahe, is still a hot topic. The stellar explosion might have been initiated by a companion star -- and modern astronomers have at last identified it.

  10. Discovery of a Low-mass Companion Around HR 3549

    NASA Astrophysics Data System (ADS)

    Mawet, D.; David, T.; Bottom, M.; Hinkley, S.; Stapelfeldt, K.; Padgett, D.; Mennesson, B.; Serabyn, E.; Morales, F.; Kuhn, J.

    2015-10-01

    We report the discovery of a low-mass companion to HR 3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 μm (10σ significance). We imaged HR 3549 B in the L band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in 2015 January. The companion is at a projected separation of ≃80 AU and position angle of ≃157°, so it is orbiting well beyond the warm disk inner edge of r > 10 AU. Our age estimate for this system corresponds to a companion mass in the range 15–80 MJ, spanning the brown dwarf regime, and so HR 3549 B is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios. The simultaneous presence of a warm disk and a brown dwarf around HR 3549 provides interesting empirical constraints on models of the formation of substellar companions.

  11. A wide binary trigger for white dwarf pollution

    NASA Astrophysics Data System (ADS)

    Bonsor, Amy; Veras, Dimitri

    2015-11-01

    Metal pollution in white dwarf atmospheres is commonly assumed to be a signature of remnant planetary systems. Most explanations for this pollution predict a sharp decrease in the number of polluted systems with white dwarf cooling age. Observations do not confirm this trend, and metal pollution in old (1-5 Gyr) white dwarfs is difficult to explain. We propose an alternative, time-independent mechanism to produce the white dwarf pollution. The orbit of a wide binary companion can be perturbed by Galactic tides, approaching close to the primary star for the first time after billions of years of evolution on the white dwarf branch. We show that such a close approach perturbs a planetary system orbiting the white dwarf, scattering planetesimals on to star-grazing orbits, in a manner that could pollute the white dwarf's atmosphere. Our estimates find that this mechanism is likely to contribute to metal pollution, alongside other mechanisms, in up to a few per cent of an observed sample of white dwarfs with wide binary companions, independent of white dwarf age. This age independence is the key difference between this wide binary mechanism and others mechanisms suggested in the literature to explain white dwarf pollution. Current observational samples are not large enough to assess whether this mechanism makes a significant contribution to the population of polluted white dwarfs, for which better constraints on the wide binary population are required, such as those that will be obtained in the near future with Gaia.

  12. Discovery of Low Mass Binary with Super Jupiter Companion

    NASA Astrophysics Data System (ADS)

    Anthes Rich, Evan; Wisniewski, John P.; Hashimoto, Jun; Brandt, Timothy; Kuzuhara, Masayuki; Tamura, Motohide

    2015-12-01

    Transit and radial velocity surveys have been prolific in detecting ~2000 confirmed planets to date. While few directly imaged planets have detected, such systems provide a unique scientific opportunity to probe exoplanets at larger angular separation, younger ages, and study their atmospheres. We present new L- and M-band AO observations, obtained with IRCS on Subaru, of a super Jupiter companion orbiting a cool dwarf. We show that the central object is likely a binary, thereby making this system the first likely directly imaged planetary mass companion surrounding a low mass binary system.

  13. Discovery of a cool brown dwarf

    NASA Astrophysics Data System (ADS)

    Nakajima, T.; Oppenheimer, B. R.; Kulkarni, S. R.; Golimowski, D. A.; Matthews, K.; Durrance, S. T.

    1995-11-01

    BROWN dwarfs are starlike objects with masses less than 0.08 times that of the Sun, which are unable to sustain hydrogen fusion in their interiors1-4. They are very hard to detect, as most of the energy of gravitational contraction is radiated away within ~108 yr, leaving only a very low residual luminosity. Accordingly, almost all searches for brown dwarfs have been directed towards clusters of young stars-a strategy that has recently proved successful5,6. But there are only modest observable differences between young brown dwarfs and very lowmass stars, making it difficult to identify the former without appealing to sophisticated models7. Older brown dwarfs should have a more distinctive appearance, and if they are companions to nearby stars, their luminosity can be determined unambiguously. Here we report the discovery of a probable companion to the nearby star G1229, with no more than onetenth the luminosity of the least luminous hydro-gen-burning star. We conclude that the companion, G1229B, is a brown dwarf with a temperature of less than 1,200 K, and a mass ~20-50 times that of Jupiter.

  14. Development of Companion Diagnostics

    PubMed Central

    Mankoff, David A.; Edmonds, Christine E.; Farwell, Michael D.; Pryma, Daniel A.

    2016-01-01

    The goal of individualized and targeted treatment and precision medicine requires the assessment of potential therapeutic targets to direct treatment selection. The biomarkers used to direct precision medicine, often termed companion diagnostics, for highly targeted drugs have thus far been almost entirely based on in vitro assay of biopsy material. Molecular imaging companion diagnostics offer a number of features complementary to those from in vitro assay, including the ability to measure the heterogeneity of each patient’s cancer across the entire disease burden and to measure early changes in response to treatment. We discuss the use of molecular imaging methods as companion diagnostics for cancer therapy with the goal of predicting response to targeted therapy and measuring early (pharmacodynamic) response as an indication of whether the treatment has “hit” the target. We also discuss considerations for probe development for molecular imaging companion diagnostics, including both small-molecule probes and larger molecules such as labeled antibodies and related constructs. We then describe two examples where both predictive and pharmacodynamic molecular imaging markers have been tested in humans: endocrine therapy for breast cancer and human epidermal growth factor receptor type 2–targeted therapy. The review closes with a summary of the items needed to move molecular imaging companion diagnostics from early studies into multicenter trials and into the clinic. PMID:26687857

  15. The Solar Neighborhood. XXXIV. a Search for Planets Orbiting Nearby M Dwarfs Using Astrometry

    NASA Astrophysics Data System (ADS)

    Lurie, John C.; Henry, Todd J.; Jao, Wei-Chun; Quinn, Samuel N.; Winters, Jennifer G.; Ianna, Philip A.; Koerner, David W.; Riedel, Adric R.; Subasavage, John P.

    2014-11-01

    Astrometric measurements are presented for seven nearby stars with previously detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ 1214) and one K dwarf (BD-10 -3166). Measurements are also presented for six additional nearby M dwarfs without known planets, but which are more favorable to astrometric detections of low mass companions, as well as three binary systems for which we provide astrometric orbit solutions. Observations have baselines of 3 to 13 years, and were made as part of the RECONS long-term astrometry and photometry program at the CTIO/SMARTS 0.9 m telescope. We provide trigonometric parallaxes and proper motions for all 16 systems, and perform an extensive analysis of the astrometric residuals to determine the minimum detectable companion mass for the 12 M dwarfs not having close stellar secondaries. For the six M dwarfs with known planets, we are not sensitive to planets, but can rule out the presence of all but the least massive brown dwarfs at periods of 2-12 years. For the six more astrometrically favorable M dwarfs, we conclude that none have brown dwarf companions, and are sensitive to companions with masses as low as 1 {{M}Jup} for periods longer than two years. In particular, we conclude that Proxima Centauri has no Jovian companions at orbital periods of 2-12 years. These results complement previously published M dwarf planet occurrence rates by providing astrometrically determined upper mass limits on potential super-Jupiter companions at orbits of two years and longer. As part of a continuing survey, these results are consistent with the paucity of super-Jupiter and brown dwarf companions we find among the over 250 red dwarfs within 25 pc observed longer than five years in our astrometric program.

  16. The solar neighborhood. XXXIV. A search for planets orbiting nearby M dwarfs using astrometry

    SciTech Connect

    Lurie, John C.; Henry, Todd J.; Ianna, Philip A.; Jao, Wei-Chun; Quinn, Samuel N.; Winters, Jennifer G.; Koerner, David W.; Riedel, Adric R.; Subasavage, John P.

    2014-11-01

    Astrometric measurements are presented for seven nearby stars with previously detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ 1214) and one K dwarf (BD-10 -3166). Measurements are also presented for six additional nearby M dwarfs without known planets, but which are more favorable to astrometric detections of low mass companions, as well as three binary systems for which we provide astrometric orbit solutions. Observations have baselines of 3 to 13 years, and were made as part of the RECONS long-term astrometry and photometry program at the CTIO/SMARTS 0.9 m telescope. We provide trigonometric parallaxes and proper motions for all 16 systems, and perform an extensive analysis of the astrometric residuals to determine the minimum detectable companion mass for the 12 M dwarfs not having close stellar secondaries. For the six M dwarfs with known planets, we are not sensitive to planets, but can rule out the presence of all but the least massive brown dwarfs at periods of 2–12 years. For the six more astrometrically favorable M dwarfs, we conclude that none have brown dwarf companions, and are sensitive to companions with masses as low as 1 M{sub Jup} for periods longer than two years. In particular, we conclude that Proxima Centauri has no Jovian companions at orbital periods of 2–12 years. These results complement previously published M dwarf planet occurrence rates by providing astrometrically determined upper mass limits on potential super-Jupiter companions at orbits of two years and longer. As part of a continuing survey, these results are consistent with the paucity of super-Jupiter and brown dwarf companions we find among the over 250 red dwarfs within 25 pc observed longer than five years in our astrometric program.

  17. Companion animal adoption study.

    PubMed

    Neidhart, Laura; Boyd, Renee

    2002-01-01

    To better understand the outcomes of companion animal adoptions, Bardsley & Neidhart Inc. conducted a series of 3 surveys over a 1-year period with dog and cat owners who had adopted their pet through either a (a) Luv-A-Pet location, (b) Adopt-a-thon, or (c) traditional shelter. This article suggests opportunities to improve owners' perceptions of their pets and the adoption process through (a) providing more information before adoption about pet health and behaviors, (b) providing counseling to potential adopters to place pets appropriately, and (c) educating adopters to promote companion animal health and retention. Results demonstrate that the pet's relationship to the family unit, such as where the pet sleeps and how much time is spent with the pet, is related to the amount of veterinary care the companion animal receives, and to long-term retention. Satisfaction and retention are attributed to the pet's personality, compatibility, and behavior, rather than demographic differences among adopters or between adoption settings. The age of the companion animal at adoption, the intended recipient, and presence of children in the home also play a role. Health problems were an issue initially for half of all adopted pets, but most were resolved within 12 months. Roughly one fourth of adopters who no longer have their companion animal said their pet died. Characteristics of pets that died support the contention that spaying and neutering profoundly affects a companion animal's life span. Although retention is similar for dogs and cats, mortality is higher among cats in the first year after adoption. PMID:12578739

  18. The history of KZ Hya and its unseen companions

    NASA Astrophysics Data System (ADS)

    Jiang, S. Y.

    2008-10-01

    KZ Hya is a short-period high amplitude metal pool population II pulsating variable. Its spectral type is B9-A7 III/IV. Its average effective temperature is 7640K. But its mass is only 0.97 solar mass. From normal stellar evolution and H-R diagram, we can not get such a solar mass star at post main sequence stage with so high effective temperature and so early type spectra. We observe this star since 1984 till now, 23years past. Finally we prove it is inside a binary with at least 2 unseen companions. The most massive companion has mass larger than 0.76 solar mass, mostly may be 0.99 to 3.99 solar mass. That means this companion must be a massive white dwarf. The distance between tow companions is about 10 AU. If the companion is white dwarf, this binary are fairly inside the nebula. This system is very old, older than 7.59 billion years. The nebula should be already diluted to very low density so that we can see the nebula directly. As its spectra type is B9III/VI at some time of maximum light and the visual absolute magnitude is 2.78, about 2 magnitudes higher than our sun. We can image that at the end of AGB stage of the companion, the strong fast winds from hot central core push away the outer atmosphere of KZ Hya. Later KZ Hya absorbed a part of Helium rich material from the companion. This will cause hydrogen content X decrease from 0.75 to about 0.62. Then KZ Hya looks like a hot post main sequence star

  19. No signature of ejecta interaction with a stellar companion in three type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Olling, Rob P.; Mushotzky, Richard; Shaya, Edward J.; Rest, Armin; Garnavich, Peter M.; Tucker, Brad E.; Kasen, Daniel; Margheim, Steve; Filippenko, Alexei V.

    2015-05-01

    Type Ia supernovae are thought to be the result of a thermonuclear runaway in carbon/oxygen white dwarfs, but it is uncertain whether the explosion is triggered by accretion from a non-degenerate companion star or by a merger with another white dwarf. Observations of a supernova immediately following the explosion provide unique information on the distribution of ejected material and the progenitor system. Models predict that the interaction of supernova ejecta with a companion star or circumstellar debris lead to a sudden brightening lasting from hours to days. Here we present data for three supernovae that are likely to be type Ia observed during the Kepler mission with a time resolution of 30 minutes. We find no signatures of the supernova ejecta interacting with nearby companions. The lack of observable interaction signatures is consistent with the idea that these three supernovae resulted from the merger of binary white dwarfs or other compact stars such as helium stars.

  20. No signature of ejecta interaction with a stellar companion in three type Ia supernovae.

    PubMed

    Olling, Rob P; Mushotzky, Richard; Shaya, Edward J; Rest, Armin; Garnavich, Peter M; Tucker, Brad E; Kasen, Daniel; Margheim, Steve; Filippenko, Alexei V

    2015-05-21

    Type Ia supernovae are thought to be the result of a thermonuclear runaway in carbon/oxygen white dwarfs, but it is uncertain whether the explosion is triggered by accretion from a non-degenerate companion star or by a merger with another white dwarf. Observations of a supernova immediately following the explosion provide unique information on the distribution of ejected material and the progenitor system. Models predict that the interaction of supernova ejecta with a companion star or circumstellar debris lead to a sudden brightening lasting from hours to days. Here we present data for three supernovae that are likely to be type Ia observed during the Kepler mission with a time resolution of 30 minutes. We find no signatures of the supernova ejecta interacting with nearby companions. The lack of observable interaction signatures is consistent with the idea that these three supernovae resulted from the merger of binary white dwarfs or other compact stars such as helium stars. PMID:25993963

  1. Companion Animals. [Information Packet.

    ERIC Educational Resources Information Center

    National Anti-Vivisection Society, Chicago, IL.

    This collection of articles reprinted from other National Anti-Vivisection Society (NAVS) publications was compiled to educate the public on issues of importance to NAVS concerning companion animals. Topics covered include spaying and neutering, animal safety, pet theft, and the use of cats and dogs in research. The article on spaying and…

  2. THE FORNAX DWARF GALAXY AS A REMNANT OF RECENT DWARF-DWARF MERGING IN THE LOCAL GROUP

    SciTech Connect

    Yozin, C.; Bekki, K.

    2012-09-01

    We present results from the first numerical analysis to support the hypothesis, first proposed in Coleman et al., that the Fornax dwarf galaxy was formed from the minor merging of two dwarfs about 2 Gyr ago. Using orbits for the Fornax dwarf that are consistent with the latest proper motion measurements, our dynamical evolution models show that the observed asymmetric shell-like substructures can be formed from the remnant of a smaller dwarf during minor merging. These models also predict the formation of diffuse stellar streams. We discuss how these stellar substructures depend on model parameters of dwarf-dwarf merging, and how the intermediate-age subpopulations found in the vicinity of these substructures may be formed from gas accretion in past merger events. We also suggest that one of Fornax's globular clusters originates from a merged dwarf companion, and demonstrate where as yet undetected tidal streams or H I gas formed from the dwarf merging may be found in the outer halo of the Galaxy.

  3. Dwarf novae

    NASA Technical Reports Server (NTRS)

    Ladous, Constanze

    1993-01-01

    Dwarf novae are defined on grounds of their semi-regular brightness variations of some two to five magnitudes on time scales of typically 10 to 100 days. Historically several different classification schemes have been used. Today, dwarf novae are divided into three sub-classes: the U Geminorum stars, the SU Ursae Majoris stars, and the Z Camelopardalis stars. Outbursts of dwarf novae occur at semi-periodic intervals of time, typically every 10 to 100 days; amplitudes range from typically 2 to 5 mag. Within certain limits values are characteristic for each object. Relations between the outburst amplitude, or the total energy released during outburst, and the recurrence time have been found, as well as relations between the orbital period and the outburst decay time, the absolute magnitude during outburst maximum, and the widths of long and short outbursts, respectively. Some dwarf novae are known to have suspended their normal outburst activity altogether for a while. They later resumed it without having undergone any observable changes. The optical colors of dwarf novae all are quite similar during outburst, considerably bluer than during the quiescent state. During the outburst cycle, characteristic loops in the two color diagram are performed. At a time resolution on the order of minutes, strictly periodic photometric changes due to orbital motion become visible in the light curves of dwarf novae. These are characteristic for each system. Remarkably little is known about orbital variations during the course of an outburst. On time-scales of minutes and seconds, further more or less periodic types of variability are seen in dwarf novae. Appreciable flux is emitted by dwarf novae at all wavelengths from the X-rays to the longest IR wavelengths, and in some cases even in the radio. Most dwarf novae exhibit strong emission line spectra in the optical and UV during quiescence, although some have only very weak emissions in the optical and/or weak absorptions at UV

  4. PROTOPLANETARY DISK MASSES FROM STARS TO BROWN DWARFS

    SciTech Connect

    Mohanty, Subhanjoy; Mortlock, Daniel; Greaves, Jane; Pascucci, Ilaria; Apai, Daniel; Scholz, Aleks; Thompson, Mark; Lodato, Giuseppe; Looper, Dagny

    2013-08-20

    We present SCUBA-2 850 {mu}m observations of seven very low mass stars (VLMS) and brown dwarfs (BDs). Three are in Taurus and four in the TW Hydrae Association (TWA), and all are classical T Tauri (cTT) analogs. We detect two of the three Taurus disks (one only marginally), but none of the TWA ones. For standard grains in cTT disks, our 3{sigma} limits correspond to a dust mass of 1.2 M{sub Circled-Plus} in Taurus and a mere 0.2 M{sub Circled-Plus} in the TWA (3-10 Multiplication-Sign deeper than previous work). We combine our data with other submillimeter/millimeter (sub-mm/mm) surveys of Taurus, {rho} Oph, and the TWA to investigate the trends in disk mass and grain growth during the cTT phase. Assuming a gas-to-dust mass ratio of 100:1 and fiducial surface density and temperature profiles guided by current data, we find the following. (1) The minimum disk outer radius required to explain the upper envelope of sub-mm/mm fluxes is {approx}100 AU for intermediate-mass stars, solar types, and VLMS, and {approx}20 AU for BDs. (2) While the upper envelope of apparent disk masses increases with M{sub *} from BDs to VLMS to solar-type stars, no such increase is observed from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporation around intermediate stellar masses. (3) Many of the disks around Taurus and {rho} Oph intermediate-mass and solar-type stars evince an opacity index of {beta} {approx} 0-1, indicating significant grain growth. Of the only four VLMS/BDs in these regions with multi-wavelength measurements, three are consistent with considerable grain growth, though optically thick disks are not ruled out. (4) For the TWA VLMS (TWA 30A and B), combining our 850 {mu}m fluxes with the known accretion rates and ages suggests substantial grain growth by 10 Myr, comparable to that in the previously studied TWA cTTs Hen 3-600A and TW Hya. The degree of grain growth in the TWA BDs (2M1207A and SSPM1102) remains largely unknown. (5) A

  5. Chromospherically active stars. 6: Giants with compact hot companions and the barium star scenario

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Henry, Gregory W.; Busby, Michael R.; Eitter, Joseph J.

    1993-01-01

    We have determined spectroscopic orbits for three chromospherically active giants that have hot compact companions. They are HD 160538 (K0 III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (K0 III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium star mass-transfer scenario. The long-period mild barium giant HD 165141 as well as HD 185510 and 39 Ceti, which have relatively short periods and normal abundance giants, appear to be consistent with this scenario. The last binary, HD 160538, a system with apparently near solar abundances, a white dwarf companion, and orbital characteristics similar to many barium stars, demonstrates that the existence of a white-dwarf companion is insufficient to produce a barium star. The paucity of systems with confirmed white-dwarf companions makes abundance analyses of HD 160538 and HD 165141 of great value in examining the role of metallicity in barium star formation.

  6. Chromospherically active stars. 11: Giant with compact hot companions and the barium star scenario

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Henry, Gregory W.; Busby, Michael R.; Eitter, Joseph J.

    1993-01-01

    We have determined spectroscopic orbits for three chromsopherically active giants that have hot compact companions. They are HD 160538 (KO III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (KO III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35,000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium star mass-transfer scenario. The long-period mild barium giant HD 165141 as well as HD 185510 and 39 Ceti, which have relatively short periods and normal abundance giants, appear to be consistent with this scenario. The last binary, HD 160538, a system with apparently near solar abundances, a white dwarf companion, and orbital characteristics similar to many barium stars, demonstrates that the existence of a white dwarf companion is insufficient to produce a barium star. The paucity of systems with confirmed white dwarf companions makes abundance analyses of HD 160538 and HD 165141 of great value in examining the role of metallicity in barium star formation.

  7. Wide Companions to Hipparcos Stars within 67 pc of the Sun

    NASA Astrophysics Data System (ADS)

    Tokovinin, Andrei; Lépine, Sébastien

    2012-10-01

    A catalog of common-proper-motion (CPM) companions to stars within 67 pc of the Sun is constructed based on the SUPERBLINK proper-motion survey. It contains 1392 CPM pairs with angular separations 30'' < ρ < 1800'', relative proper motion between the two components less than 25 mas yr-1, and magnitudes and colors of the secondaries consistent with those of dwarfs in the (MV , V - J) diagram. In addition, we list 21 candidate white dwarf CPM companions with separations under 300'', about half of which should be physical. We estimate a 0.31 fraction of pairs with red dwarf companions to be physical systems (about 425 objects), while the rest (mostly wide pairs) are chance alignments. For each candidate companion, the probability of a physical association is evaluated. The distribution of projected separations s of the physical pairs between 2 kAU and 64 kAU follows f(s)vprops -1.5, which decreases faster than Öpik's law. We find that solar-mass dwarfs have no less than 4.4% ± 0.3% companions with separations larger than 2 kAU, or 3.8% ± 0.3% per decade of orbital separation in the 2-16 kAU range. The distribution of mass ratio of those wide companions is approximately uniform in the 0.1 < q < 1.0 range, although we observe a dip at q ~= 0.5 which, if confirmed, could be evidence of bimodal distribution of companion masses. New physical CPM companions to two exoplanet host stars are discovered.

  8. WIDE COMPANIONS TO HIPPARCOS STARS WITHIN 67 pc OF THE SUN

    SciTech Connect

    Tokovinin, Andrei; Lepine, Sebastien E-mail: lepine@amnh.org

    2012-10-01

    A catalog of common-proper-motion (CPM) companions to stars within 67 pc of the Sun is constructed based on the SUPERBLINK proper-motion survey. It contains 1392 CPM pairs with angular separations 30'' < {rho} < 1800'', relative proper motion between the two components less than 25 mas yr{sup -1}, and magnitudes and colors of the secondaries consistent with those of dwarfs in the (M{sub V} , V - J) diagram. In addition, we list 21 candidate white dwarf CPM companions with separations under 300'', about half of which should be physical. We estimate a 0.31 fraction of pairs with red dwarf companions to be physical systems (about 425 objects), while the rest (mostly wide pairs) are chance alignments. For each candidate companion, the probability of a physical association is evaluated. The distribution of projected separations s of the physical pairs between 2 kAU and 64 kAU follows f(s){proportional_to}s {sup -1.5}, which decreases faster than Oepik's law. We find that solar-mass dwarfs have no less than 4.4% {+-} 0.3% companions with separations larger than 2 kAU, or 3.8% {+-} 0.3% per decade of orbital separation in the 2-16 kAU range. The distribution of mass ratio of those wide companions is approximately uniform in the 0.1 < q < 1.0 range, although we observe a dip at q {approx_equal} 0.5 which, if confirmed, could be evidence of bimodal distribution of companion masses. New physical CPM companions to two exoplanet host stars are discovered.

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

    SciTech Connect

    Farihi, J; Becklin, E; Macintosh, B

    2004-11-03

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

  10. Merging white dwarfs and thermonuclear supernovae.

    PubMed

    van Kerkwijk, M H

    2013-06-13

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and the suggestion that these supernovae instead result from mergers of carbon-oxygen white dwarfs, including those that produce sub-Chandrasekhar-mass remnants. I then turn to possible observational tests, in particular, those that test the absence or presence of electron captures during the burning. PMID:23630372

  11. A CHANDRA OBSERVATION OF THE TW HYDRAE ASSOCIATION BROWN DWARF 2MASSW J1139511-315921

    SciTech Connect

    Castro, Philip J.; Gizis, John E.; Gagne, Marc E-mail: gizis@udel.edu

    2011-07-20

    We report on a sequence of Chandra X-Ray Observatory observations of the TW Hydrae brown dwarf (BD) 2MASSW J1139511-315921 (2M1139). In the combined 31 ks ACIS-S exposure, 2M1139 is detected at the 3{sigma} confidence level. We find an X-ray luminosity of L{sub X} = 1.4{sup +2.7}{sub -1.0} x 10{sup 26} erg s{sup -1} or log L{sub X}/L{sub bol} = -4.8 {+-} 0.3. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B): both have H{alpha} emission, both show no signatures of accretion, and both have comparable ages and spectral types. TWA 5B was previously detected in X-rays with a luminosity of L{sub X} = 4 x 10{sup 27} erg s{sup -1} or log L{sub X}/L{sub bol} = -3.4, an order of magnitude more luminous in X-rays than 2M1139. We find that the discrepancy between the X-ray luminosity of 2M1139 and TWA 5B is consistent with the spread in X-ray luminosity in the Orion Nebula Cluster for BDs of similar spectral types. Though rotation may play a role in the X-ray activity of ultracool dwarfs like 2M1139 and TWA 5B, the discrepancy cannot be explained by rotation alone. We also examine two X-ray bright objects in the field of view of our Chandra observations and find one to be of spectral type K0IV and identify it as a possible RS Canum Venaticorum, and another X-ray bright object whose light curve clearly shows the decay phase of an X-ray flare.

  12. WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE

    SciTech Connect

    Casewell, S. L.; Burleigh, M. R.; Wynn, G. A.; Alexander, R. D.; Lawrie, K. A.; Jameson, R. F.; Napiwotzki, R.; Dobbie, P. D.; Hodgkin, S. T.

    2012-11-10

    There is a striking and unexplained dearth of brown dwarf companions in close orbits (<3 AU) around stars more massive than the Sun, in stark contrast to the frequency of stellar and planetary companions. Although rare and relatively short-lived, these systems leave detectable evolutionary end points in the form of white-dwarf-brown-dwarf binaries and these remnants can offer unique insights into the births and deaths of their parent systems. We present the discovery of a close (orbital separation {approx}0.006 AU) substellar companion to a massive white dwarf member of the Praesepe star cluster. Using the cluster age and the mass of the white dwarf, we constrain the mass of the white dwarf progenitor star to lie in the range 3.5-3.7 M{sub Sun} (B9). The high mass of the white dwarf means the substellar companion must have been engulfed by the B star's envelope while it was on the late asymptotic giant branch (AGB). Hence, the initial separation of the system was {approx}2 AU, with common envelope evolution reducing the separation to its current value. The initial and final orbital separations allow us to constrain the combination of the common envelope efficiency ({alpha}) and binding energy parameters ({lambda}) for the AGB star to {alpha}{lambda} {approx} 3. We examine the various formation scenarios and conclude that the substellar object was most likely captured by the white dwarf progenitor early in the life of the cluster, rather than forming in situ.

  13. Wide Low-Mass Tertiary Companions of Binary Star Systems as a Test of Star Formation Theories

    NASA Astrophysics Data System (ADS)

    Douglas, Stephanie; Allen, P.

    2012-01-01

    We will present the status of a common proper motion search for wide low-mass stellar and sub-stellar companions to known white dwarf-M dwarf binary systems. I-band observations were made using the 31" NURO telescope at Lowell Observatory. Candidate companions are selected using astrometry from our own data and 2MASS photometry. We have begun to spectroscopically confirm candidates that pass our selection criteria. The ultimate goal of the search is to test star formation theories which predict that close binary systems form by transferring angular momentum to a third companion. To this end, we will model the physical companion population and perform Bayesian statistical analysis to determine the best-fit population model to our data. Here we will present our spectroscopically confirmed companions as well as the preliminary results of our population models and statistical analysis.

  14. Discovery of a low-mass companion to the F7V star HD 984

    NASA Astrophysics Data System (ADS)

    Meshkat, T.; Bonnefoy, M.; Mamajek, E. E.; Quanz, S. P.; Chauvin, G.; Kenworthy, M. A.; Rameau, J.; Meyer, M. R.; Lagrange, A.-M.; Lannier, J.; Delorme, P.

    2015-11-01

    We report the discovery of a low-mass companion to the nearby (d = 47 pc) F7V star HD 984. The companion is detected 0.19 arcsec away from its host star in the L' band with the Apodized Phase Plate on NaCo/Very Large Telescope and was recovered by L'-band non-coronagraphic imaging data taken a few days later. We confirm the companion is comoving with the star with SINFONI integral field spectrograph H + K data. We present the first published data obtained with SINFONI in pupil-tracking mode. HD 984 has been argued to be a kinematic member of the 30 Myr-old Columba group, and its HR diagram position is not altogether inconsistent with being a zero-age main sequence star of this age. By consolidating different age indicators, including isochronal age, coronal X-ray emission, and stellar rotation, we independently estimate a main-sequence age of 115 ± 85 Myr (95 per cent CL) which does not rely on this kinematic association. The mass of directly imaged companions are usually inferred from theoretical evolutionary tracks, which are highly dependent on the age of the star. Based on the age extrema, we demonstrate that with our photometric data alone, the companion's mass is highly uncertain: between 33 and 96 MJup (0.03-0.09 M⊙) using the COND evolutionary models. We compare the companion's SINFONI spectrum with field dwarf spectra to break this degeneracy. Based on the slope and shape of the spectrum in the H band, we conclude that the companion is an M6.0 ± 0.5 dwarf. The age of the system is not further constrained by the companion, as M dwarfs are poorly fit on low-mass evolutionary tracks. This discovery emphasizes the importance of obtaining a spectrum to spectral type companions around F-stars.

  15. WHITE DWARF/M DWARF BINARIES AS SINGLE DEGENERATE PROGENITORS OF TYPE Ia SUPERNOVAE

    SciTech Connect

    Wheeler, J. Craig

    2012-10-20

    Limits on the companions of white dwarfs in the single-degenerate scenario for the origin of Type Ia supernovae (SNe Ia) have gotten increasingly tight, yet igniting a nearly Chandrasekhar mass C/O white dwarf from a condition of near hydrostatic equilibrium provides compelling agreement with observed spectral evolution. The only type of non-degenerate stars that survive the tight limits, M{sub V} {approx}> 8.4 on the SN Ia in SNR 0509-67.5 and M{sub V} {approx}> 9.5 in the remnant of SN 1572, are M dwarfs. While M dwarfs are observed in cataclysmic variables, they have special properties that have not been considered in most work on the progenitors of SNe Ia: they have small but finite magnetic fields and they flare frequently. These properties are explored in the context of SN Ia progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide, in principle, an adequate rate of explosions even with slow orbital evolution due to magnetic braking or gravitational radiation. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a 'magnetic bottle' connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the 'nova limit' and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.

  16. White Dwarf/M Dwarf Binaries as Single Degenerate Progenitors of Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Wheeler, J. Craig

    2012-10-01

    Limits on the companions of white dwarfs in the single-degenerate scenario for the origin of Type Ia supernovae (SNe Ia) have gotten increasingly tight, yet igniting a nearly Chandrasekhar mass C/O white dwarf from a condition of near hydrostatic equilibrium provides compelling agreement with observed spectral evolution. The only type of non-degenerate stars that survive the tight limits, MV >~ 8.4 on the SN Ia in SNR 0509-67.5 and MV >~ 9.5 in the remnant of SN 1572, are M dwarfs. While M dwarfs are observed in cataclysmic variables, they have special properties that have not been considered in most work on the progenitors of SNe Ia: they have small but finite magnetic fields and they flare frequently. These properties are explored in the context of SN Ia progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide, in principle, an adequate rate of explosions even with slow orbital evolution due to magnetic braking or gravitational radiation. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a "magnetic bottle" connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the "nova limit" and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.

  17. Keck Imaging of Binary L Dwarfs.

    PubMed

    Koerner; Kirkpatrick; McElwain; Bonaventura

    1999-11-20

    We present Keck near-infrared imaging of three binary L dwarf systems, all of which are likely to be substellar. Two are lithium dwarfs, and a third exhibits an L7 spectral type, making it the coolest binary known to date. All have component flux ratios near 1 and projected physical separations between 5 and 10 AU, assuming distances of 18-26 pc from recent measurements of trigonometric parallax. These surprisingly similar binaries represent the sole detections of companions in 10 L dwarf systems that were analyzed in the preliminary phase of a much larger dual-epoch imaging survey. The detection rate prompts us to speculate that binary companions to L dwarfs are common, that similar-mass systems predominate, and that their distribution peaks at radial distances in accord both with M dwarf binaries and with the radial location of Jovian planets in our own solar system. To fully establish these conjectures against doubts raised by biases inherent in this small preliminary survey, however, will require quantitative analysis of a larger volume-limited sample that has been observed with high resolution and dynamic range. PMID:10534453

  18. A coronagraphic search for brown dwarfs around nearby stars

    NASA Technical Reports Server (NTRS)

    Nakajima, T.; Durrance, S. T.; Golimowski, D. A.; Kulkarni, S. R.

    1994-01-01

    Brown dwarf companions have been searched for around stars within 10 pc of the Sun using the Johns-Hopkins University Adaptive Optics Coronagraph (AOC), a stellar coronagraph with an image stabilizer. The AOC covers the field around the target star with a minimum search radius of 1 sec .5 and a field of view of 1 arcmin sq. We have reached an unprecedented dynamic range of Delta m = 13 in our search for faint companions at I band. Comparison of our survey with other brown dwarf searches shows that the AOC technique is unique in its dynamic range while at the same time just as sensitive to brown dwarfs as the recent brown dwarf surveys. The present survey covered 24 target stars selected from the Gliese catalog. A total of 94 stars were detected in 16 fields. The low-latitude fields are completely dominated by background star contamination. Kolmogorov-Smirnov tests were carried out for a sample restricted to high latitudes and a sample with small angular separations. The high-latitude sample (b greater than or equal to 44 deg) appears to show spatial concentration toward target stars. The small separation sample (Delta Theta less than 20 sec) shows weaker dependence on Galactic coordinates than field stars. These statistical tests suggest that both the high-latitude sample and the small separation sample can include a substantial fraction of true companions. However, the nature of these putative companions is mysterious. They are too faint to be white dwarfs and too blue for brown dwarfs. Ignoring the signif icance of the statistical tests, we can reconcile most of the detections with distant main-sequence stars or white dwarfs except for a candidate next to GL 475. Given the small size of our sample, we conclude that considerably more targets need to be surveyed before a firm conclusion on the possibility of a new class of companions can be made.

  19. Andromeda and the Seven Dwarfs

    NASA Astrophysics Data System (ADS)

    Brasseur, C.; Rix, H.-W.; Martin, N.

    2011-07-01

    With the new generation of wide-field surveys, our understanding of the Andromeda satellite system has dramatically improved in recent years. Since 2004, 12 new dwarf galaxies have been discovered around Andromeda, doubling the number of previously known companions. What are the properties of these newly discovered dwarfs and what do they tell us about galaxy formation? Are these systems bound? Do they show evidence of multiple star formation epochs? To better understand the stellar populations of the faintest dwarfs around M 31, we have used the Large Binocular Camera (LBT) and Suprime-Cam (Subaru) to obtain photometric observations of And X, And XVII, And XVIII, And XIX, And XX, And XXI and And XXII. Reaching below the horizontal branch, these observations have allowed for accurate distance determinations to be made, together with metallicity estimates based on the red giant branch stars. Our analysis shows our 7 dwarfs to be metal poor and with large spreads in [Fe/H], it strongly suggests multiple generations of stars are present in And X, And XVII, And XVIII, and And XIX, And XXI.

  20. Dancing in the Dark --- Unseen Companions of Nearby Stars

    NASA Astrophysics Data System (ADS)

    Henry, Todd J.; Koerner, D. W.; Jao, W. C.; Subasavage, J. P.; Ianna, P. A.; Bean, J. L.; Benedict, G. F.; McArthur, B. E.; RECONS

    2007-12-01

    We are carrying out the ASPENS (Astrometric Search for Planets Encircling Nearby Stars) program using the CTIO 0.9m telescope in an effort to discover unseen companions to 100 nearby stars. The CCD camera used yields substantial improvement in the detection of low mass companions over the classic studies done using photographic plates. We have accumulated up to 8 years of astrometric data on 85 red dwarfs and 14 white dwarfs, primarily at southern declinations and within 10 parsecs. The target list includes 39 new solar neighbors revealed to be closer than 10 parsecs by the RECONS team. With consistent (and significant) observing time as part of the SMARTS Consortium, we have been able to discover new companions with masses between 0.20 Msun and 4 Mjup. The latter is the first confirmed discovery of an extrasolar planet via astrometry. We have also detected the planet through HET iodine cell radial velocity work. Nearby red dwarfs are prime candidates for NASA's SIM PlanetQuest because the astrometric perturbations are largest for planets orbiting nearby stars of low mass. In addition, new multiple red dwarf systems can be targeted for mass determinations, thereby providing points on a comprehensive mass-luminosity relation for the most populous members of the Galaxy. These long-term observations began in 1999 as an NOAO Surveys program, and are continuing via the SMARTS Consortium. This work has been supported by the National Science Foundation (AST 98-20711 and 05-07711), NASA's SIM PlanetQuest, Georgia State University, and Northern Arizona University.

  1. Can brown dwarfs survive on close orbits around convective stars?

    NASA Astrophysics Data System (ADS)

    Damiani, C.; Díaz, R. F.

    2016-05-01

    Context. The mass range of brown dwarfs extends across the planetary domain to stellar objects. There is a relative paucity of brown dwarfs companions around FGKM-type stars compared to exoplanets for orbital periods of less than a few years, but most of the short-period brown dwarf companions that are fully characterised by transits and radial velocities are found around F-type stars. Aims: We examine the hypothesis that brown dwarf companions could not survive on close orbit around stars with important convective envelopes because the tides and angular momentum loss, the result of magnetic braking, would lead to a rapid orbital decay with the companion being quickly engulfed. Methods: We use a classical Skumanich-type braking law and constant time-lag tidal theory to assess the characteristic timescale for orbital decay for the brown dwarf mass range as a function of the host properties. Results: We find that F-type stars may host massive companions for a significantly longer time than G-type stars for a given orbital period, which may explain the paucity of G-type hosts for brown dwarfs with an orbital period less than five days. On the other hand, we show that the small radius of early M-type stars contributes to orbital decay timescales that are only half those of F-type stars, despite their more efficient tidal dissipation and magnetic braking. For fully convective later type M-dwarfs, orbital decay timescales could be orders of magnitude greater than for F-type stars. Moreover, we find that, for a wide range of values of tidal dissipation efficiency and magnetic braking, it is safe to assume that orbital decay for massive companions can be neglected for orbital periods greater than ten days. Conclusions: For orbital periods greater than ten days, brown dwarf occurrence should largely be unaffected by tidal decay, whatever the mass of the host. On closer orbital periods, the rapid engulfment of massive companions could explain the lack of G and K-type hosts

  2. Can brown dwarfs survive on close orbits around convective stars?

    NASA Astrophysics Data System (ADS)

    Damiani, C.; Díaz, R. F.

    2016-04-01

    Context. The mass range of brown dwarfs extends across the planetary domain to stellar objects. There is a relative paucity of brown dwarfs companions around FGKM-type stars compared to exoplanets for orbital periods of less than a few years, but most of the short-period brown dwarf companions that are fully characterised by transits and radial velocities are found around F-type stars. Aims: We examine the hypothesis that brown dwarf companions could not survive on close orbit around stars with important convective envelopes because the tides and angular momentum loss, the result of magnetic braking, would lead to a rapid orbital decay with the companion being quickly engulfed. Methods: We use a classical Skumanich-type braking law and constant time-lag tidal theory to assess the characteristic timescale for orbital decay for the brown dwarf mass range as a function of the host properties. Results: We find that F-type stars may host massive companions for a significantly longer time than G-type stars for a given orbital period, which may explain the paucity of G-type hosts for brown dwarfs with an orbital period less than five days. On the other hand, we show that the small radius of early M-type stars contributes to orbital decay timescales that are only half those of F-type stars, despite their more efficient tidal dissipation and magnetic braking. For fully convective later type M-dwarfs, orbital decay timescales could be orders of magnitude greater than for F-type stars. Moreover, we find that, for a wide range of values of tidal dissipation efficiency and magnetic braking, it is safe to assume that orbital decay for massive companions can be neglected for orbital periods greater than ten days. Conclusions: For orbital periods greater than ten days, brown dwarf occurrence should largely be unaffected by tidal decay, whatever the mass of the host. On closer orbital periods, the rapid engulfment of massive companions could explain the lack of G and K-type hosts

  3. Signatures of a companion star in type Ia supernovae

    SciTech Connect

    Maeda, Keiichi; Kutsuna, Masamichi; Shigeyama, Toshikazu

    2014-10-10

    Although type Ia supernovae (SNe Ia) have been used as precise cosmological distance indicators, their progenitor systems remain unresolved. One of the key questions is whether there is a nondegenerate companion star at the time of a thermonuclear explosion of a white dwarf. In this paper, we investigate whether an interaction between the SN ejecta and the companion star may result in observable footprints around the maximum brightness and thereafter, by performing multidimensional radiation transfer simulations based on hydrodynamic simulations of the interaction. We find that such systems result in variations in various observational characteristics due to different viewing directions, and the predicted behaviors (redder and fainter for the companion direction) are the opposite of what were suggested by the previous study. The variations are generally modest and within observed scatters. However, the model predicts trends between some observables different from those observationally derived, so a large sample of SNe Ia with small calibration errors may be used to constrain the existence of such a companion star. The variations in different colors in optical band passes can be mimicked by external extinctions, so such an effect could be a source of scatter in the peak luminosity and derived distance. After the peak, hydrogen-rich materials expelled from the companion will manifest themselves in hydrogen lines, but Hα is extremely difficult to identify. Alternatively, we find that P{sub β} in postmaximum near-infrared spectra can potentially provide a powerful diagnostic.

  4. NLTT 41135: A FIELD M DWARF + BROWN DWARF ECLIPSING BINARY IN A TRIPLE SYSTEM, DISCOVERED BY THE MEARTH OBSERVATORY

    SciTech Connect

    Irwin, Jonathan; Buchhave, Lars; Berta, Zachory K.; Charbonneau, David; Latham, David W.; Burke, Christopher J.; Esquerdo, Gilbert A.; Everett, Mark E.; Holman, Matthew J.; Nutzman, Philip; Berlind, Perry; Calkins, Michael L.; Falco, Emilio E.; Winn, Joshua N.; Johnson, John A.; Gazak, J. Zachary

    2010-08-01

    We report the discovery of an eclipsing companion to NLTT 41135, a nearby M5 dwarf that was already known to have a wider, slightly more massive common proper motion companion, NLTT 41136, at 2.''4 separation. Analysis of combined-light and RV curves of the system indicates that NLTT 41135B is a (31-34) {+-} 3M{sub Jup} brown dwarf (where the range depends on the unknown metallicity of the host star) on a circular orbit. The visual M dwarf pair appears to be physically bound, so the system forms a hierarchical triple, with masses approximately in the ratio 8:6:1. The eclipses are grazing, preventing an unambiguous measurement of the secondary radius, but follow-up observations of the secondary eclipse (e.g., with the James Webb Space Telescope) could permit measurements of the surface brightness ratio between the two objects, and thus place constraints on models of brown dwarfs.

  5. Searching for substellar companions of young isolated neutron stars

    NASA Astrophysics Data System (ADS)

    Posselt, B.; Neuhäuser, R.; Haberl, F.

    2009-03-01

    Context: Only two planetary systems orbiting old ms-pulsars have been discovered. Young radio pulsars and radio-quiet neutron stars cannot be analysed by the usually-applied radio-pulse-timing technique. However, finding substellar companions orbiting these neutron stars would be of significant importance: the companion may have had an exotic formation, its observation may also enable us to study neutron-star physics. Aims: We investigate the closest young neutron stars to Earth to search for orbiting substellar companions. Methods: Young, thus warm substellar companions are visible in the Near infrared, in which the neutron star itself is much fainter. Four young neutron stars are at sufficient speed to enable a common proper-motion search for substellar companions within few years. Results: For Geminga, RX J0720.4-3125, RX J1856.6-3754, and PSR J1932+1059 we found no comoving companion of masses as low as 12, 15, 11, and 42 Jupiter masses, respectively, for assumed ages of 1, 1, 1, and 3.1 Myr, and distances of 250, 361, 167, and 361 pc, respectively. Near infrared limits are presented for these four and five additional neutron stars for which we have observations for only one epoch. Conclusions: We conclude that young, isolated neutron stars rarely have brown-dwarf companions. Based on observations made with ESO Telescopes at the La Silla or Paranal Observatories under programme IDs: 66.D-0135, 71.C-0189, 72.C-0051, 74.C-0596, 077.C-0162, 78.C-0686, 79.C-0570.

  6. A METAL-RICH LOW-GRAVITY COMPANION TO A MASSIVE MILLISECOND PULSAR

    SciTech Connect

    Kaplan, D. L.; Bhalerao, V. B.; Van Kerkwijk, M. H.; Koester, D.; Kulkarni, S. R.; Stovall, K. E-mail: mhvk@astro.utoronto.ca

    2013-03-10

    Most millisecond pulsars with low-mass companions are in systems with either helium-core white dwarfs or non-degenerate (''black widow'' or ''redback'') stars. A candidate counterpart to PSR J1816+4510 was identified by Kaplan et al. whose properties were suggestive of both types of companions although identical to neither. We have assembled optical spectroscopy of the candidate companion and confirm that it is part of the binary system with a radial velocity amplitude of 343 {+-} 7 km s{sup -1}, implying a high pulsar mass, M{sub psr}sin {sup 3} i = 1.84 {+-} 0.11 M{sub Sun }, and a companion mass M{sub c} sin {sup 3} i = 0.193 {+-} 0.012 M{sub Sun }, where i is the inclination of the orbit. The companion appears similar to proto-white dwarfs/sdB stars, with a gravity log{sub 10}(g) = 4.9 {+-} 0.3, and effective temperature 16, 000 {+-} 500 K. The strongest lines in the spectrum are from hydrogen, but numerous lines from helium, calcium, silicon, and magnesium are present as well, with implied abundances of roughly 10 times solar (relative to hydrogen). As such, while from the spectrum the companion to PSR J1816+4510 is superficially most similar to a low-mass white dwarf, it has much lower gravity, is substantially larger, and shows substantial metals. Furthermore, it is able to produce ionized gas eclipses, which had previously been seen only for low-mass, non-degenerate companions in redback or black widow systems. We discuss the companion in relation to other sources, but find that we understand neither its nature nor its origins. Thus, the system is interesting for understanding unusual stellar products of binary evolution, as well as, independent of its nature, for determining neutron-star masses.

  7. Multi-wavelength studies of pulsars and their companions

    NASA Astrophysics Data System (ADS)

    Antoniadis, John Ioannis

    2013-09-01

    Neutron stars are the degenerate relic cores of massive stars formed in the aftermath of a supernova explosion. Matter in their centes is believed to be condensed at densities as high as ten times that found in atomic nuclei. Thus, observational access to their properties provides the means to study the behavior of physical laws in extreme conditions, beyond the reach of terrestrial experiments. Rapidly rotating, highly magnetized neutron stars emit a narrow intense beam of radio emission from their magnetospheric poles. When this pulse happens to intersect our line of sight, it gives rise to the pulsar phenomenon. Regular radio-timing of pulse arrival times on earth, results in some of the most precise measurements in astrophysics. This thesis deals with the study of binary millisecond pulsars with white dwarf companions and is divided in 7 Chapters. Chapters 1 & 2 give a brief introduction to neutron stars, pulsars, and binary pulsars. Chapter 3 describes spectroscopic and optical observations of the low mass white dwarf companion to PSR J1909-3744. For this system, radio observations have yielded a precise mass measurement as well as distance information. Combined with the optical data, these provide the first observational test for theoretical white-dwarf cooling models and spectra. The latter, if reliable, can be used to infer theory-independent masses for similar systems. In Chapter 4, I discuss the measurement of the component masses in the short-orbit PSR J1738+0333 system based on spectroscopy of its white-dwarf companion. This system is particularly important for understanding the physics of pulsar recycling and binary evolution. Moreover, combined with the measurement of the orbital decay from radio-timing, the masses pose the most stringent constraints on Scalar-Tensor gravity. Chapter 5 describes radio and optical observations of PSR J0348+0432, a compact pulsar-white dwarf binary discovered recently with the 100-m Green-Bank Radio Telescope. Spectral

  8. Candidate Very-Low-Mass Companions to Nearby Stars Found in the WISE Survey

    NASA Astrophysics Data System (ADS)

    Mennen, Anne; Dutcher, D.; Lepine, S.; Faherty, J.

    2012-01-01

    We report the identification in the Wide-Field Survey Explorer (WISE) preliminary release of 36 probable very-low-mass companions to nearby stars from the SUPERBLINK proper motion catalogue. We examined all WISE sources within one arcminute of a subset of 156,000 SUPERBLINK stars with proper motions between 0.040 and 0.015 seconds of arc per year, photometric distances within 100 parsecs, and positions at least seven degrees from the galactic plane. Using proper motions calculated by comparing the WISE positions of the sources to those of their counterparts in the 2MASS Catalogue, we identified all WISE sources sharing a common proper motion with the SUPERBLINK star. We eliminated all sources detected in the Palomar Sky Survey blue plates, keeping only those red enough to be low-mass or brown dwarf companions. We used WISE and 2MASS colors to select only objects consistent with being M, L, or T dwarfs, leaving only 36 likely companions. Based on their color and assumed distances, we estimate the 36 low-mass companions to be either late M or early L dwarfs. Follow-up spectroscopic observations will be required for confirmation and formal spectral classification of the companions. We acknowledge the American Museum of Natural History and the National Science Foundation for their support.

  9. IZw18 has a Dynamically Associated Companion Galaxy

    NASA Astrophysics Data System (ADS)

    Dufour, R. J.; Castaneda, H. O.; Esteban, C.

    1996-09-01

    We present kinematical evidence that the irregular galaxy located 26'' northwest of IZw18 -the most metal-poor blue-compact-dwarf (BCD) galaxy known- is a dynamically associated companion system. Longslit CCD spectra were obtained in 1996 February using the 4.2m WHT+ISIS at La Palma, with the slit placed across the NW HII region of IZw18 and through an Hα knot in the center of the companion galaxy. Deep CCD spectra were acquired simultaneously in the blue and red spectral regions; with the blue covering Hβ and [OIII] 4959,5007 Angstroms, and the red covering Hα . The red spectra showed continuous Hα emission from the BCD main body of IZw18 to the Hα knot in the companion galaxy. The heliocentric radial velocity variation for the Hα line across a 50'' length of slit ( ~ 2.4 kpc for a distance of 10 Mpc for IZw18) shows a smooth double-sinusoidal variation ranging from +730 km/s just NW of the brightest star-forming region in IZw18 to +780 km/s in the SE extremity of the main body. The heliocentric velocity of the brightest Hα knot in the main body was measured as +741.0+/-0.1 km/s and that of the Hα knot in the companion was found to be +752+/-2 km/s (where the errors are the residuals of the gaussian fits; systematic errors are yet to be evaluated). In addition to the radial velocity information, we present an analysis of high velocity gas seen in the wings of Hα and other lines at several locations across IZw18 and in the Hα knot of the companion system (where we find the knot to be an expanding cloud, with vexp ~ 100 km/s). Previous HST WFPC2 imagery (Dufour et al. 1995, BAAS, 27, 86) indicated that the companion system (``C'') was a dwarf irregular galaxy of type Im that resolved into stars at the V~24.5 level. They also noted that it contained stars as young as ~ 40 Myr -if it were at the same distance as IZw18. Our new results prove that ``IZw18'' consists of a pair of dwarf irregulars, one currently undergoing a starburst (the BCD namesake) and

  10. Infrared Photometry of Late-M, L, and T Dwarfs

    NASA Astrophysics Data System (ADS)

    Leggett, S. K.; Golimowski, David A.; Fan, Xiaohui; Geballe, T. R.; Knapp, G. R.; Brinkmann, J.; Csabai, István; Gunn, James E.; Hawley, Suzanne L.; Henry, Todd J.; Hindsley, Robert; Ivezić, Željko; Lupton, Robert H.; Pier, Jeffrey R.; Schneider, Donald P.; Smith, J. Allyn; Strauss, Michael A.; Uomoto, Alan; York, D. G.

    2002-01-01

    We present ZJHKL'M' photometry of a sample of 58 late M, L, and T dwarfs, most of which are identified from the Sloan Digital Sky Survey and the Two Micron All-Sky Survey. Near-infrared spectra and spectral classifications for most of this sample are presented in a companion paper by Geballe et al. We derive the luminosities of 18 dwarfs in the sample with known parallaxes, and the results imply that the effective temperature range for the L dwarfs in our sample is approximately 2200-1300 K and for the T dwarfs 1300-800 K. We obtained new photometric data at the United Kingdom Infrared Telescope for: 42 dwarfs at Z, 34 dwarfs at JHK, 21 dwarfs at L', as well as M' data for two L dwarfs and two T dwarfs. The M' data provide the first accurate photometry for L and T dwarfs in this bandpass-for a T2 and a T5 dwarf, we find K-M'=1.2 and 1.6, respectively. These colors are much bluer than predicted by published models, suggesting that CO may be more abundant in these objects than expected, as has been found for the T6 dwarf Gl 229B. We also find that K-L' increases monotonically through most of the M, L, and T subclasses, but it is approximately constant between types L6 and T5, restricting its usefulness as a temperature indicator. The degeneracy is probably due to the onset of CH4 absorption at the blue edge of the L' bandpass. The JHK colors of L dwarfs show significant scatter, suggesting that the fluxes in these bandpasses are sensitive to variations in photospheric dust properties. The H-K colors of the later T dwarfs also show some scatter, which we suggest is due to variations in pressure-induced H2 opacity, which is sensitive to gravity and metallicity.

  11. GIANT GALAXIES, DWARFS, AND DEBRIS SURVEY. I. DWARF GALAXIES AND TIDAL FEATURES AROUND NGC 7331

    SciTech Connect

    Ludwig, Johannes; Pasquali, Anna; Grebel, Eva K.; Gallagher, John S. III

    2012-12-01

    The Giant GAlaxies, Dwarfs, and Debris Survey (GGADDS) concentrates on the nearby universe to study how galaxies have interacted in groups of different morphology, density, and richness. In these groups, we select the dominant spiral galaxy and search its surroundings for dwarf galaxies and tidal interactions. This paper presents the first results from deep wide-field imaging of NGC 7331, where we detect only four low-luminosity candidate dwarf companions and a stellar stream that may be evidence of a past tidal interaction. The dwarf galaxy candidates have surface brightnesses of {mu}{sub r} Almost-Equal-To 23-25 mag arcsec{sup -2} with (g - r){sub 0} colors of 0.57-0.75 mag in the Sloan Digital Sky Survey filter system, consistent with their being dwarf spheroidal (dSph) galaxies. A faint stellar stream structure on the western edge of NGC 7331 has {mu}{sub g} Almost-Equal-To 27 mag arcsec{sup -2} and a relatively blue color of (g - r){sub 0} = 0.15 mag. If it is tidal debris, then this stream could have formed from a rare type of interaction between NGC 7331 and a dwarf irregular or transition-type dwarf galaxy. We compare the structure and local environments of NGC 7331 to those of other nearby giant spirals in small galaxy groups. NGC 7331 has a much lower ({approx}2%) stellar mass in the form of early-type satellites than found for M31 and lacks the presence of nearby companions like luminous dwarf elliptical galaxies or the Magellanic Clouds. However, our detection of a few dSph candidates suggests that it is not deficient in low-luminosity satellites.

  12. Immunocontraception in companion animals.

    PubMed

    Purswell, B J; Kolster, Kara A

    2006-08-01

    There is real need worldwide to control the population growth of companion animals. Throughout the world and particularly in the United States, overpopulation of unwanted dogs and cats is a concern for many reasons. Feral populations pose risk to native species by spread of disease and predation. That unwanted animals are humanely eradicated is of concern to many persons. The need to control population growth has led to various approaches to contraception, including immunocontraception. Concerns regarding efficacy, duration of action, harm to the individual, and species specificity are among the issues being addressed. As new technologies emerge, ethical, political, and safety issues evoke differing opinions. It is hoped that in the near future, different strategies will be developed to solve this disturbing problem. PMID:16837035

  13. Evidence for variable, correlated X-ray and optical/IR extinction towards the nearby, pre-main-sequence binary TWA 30

    NASA Astrophysics Data System (ADS)

    Principe, David A.; Sacco, G.; Kastner, J. H.; Stelzer, B.; Alcalá, J. M.

    2016-06-01

    We present contemporaneous XMM-Newton X-ray and ground-based optical/near-IR spectroscopic observations of the nearby (D ≈ 42 pc), low-mass (mid-M) binary system TWA 30A and 30B. The components of this wide (separation ˜3400 au) binary are notable for their nearly edge-on disc viewing geometries, high levels of variability, and evidence for collimated stellar outflows. We obtained XMM-Newton X-ray observations of TWA 30A and 30B in 2011 June and July, accompanied (respectively) by Infrared Telescope Facility SpeX (near-IR) and VLT XSHOOTER (visible/near-IR) spectroscopy obtained within ˜20 h of the X-ray observations. TWA 30A was detected in both XMM-Newton observations at relatively faint intrinsic X-ray luminosities (LX ˜ 8 × 1027 erg s-1) compared to stars of similar mass and age. The intrinsic (0.15-2.0 keV) X-ray luminosities measured in 2011 had decreased by a factor 20-100 relative to a 1990 (ROSAT) X-ray detection. TWA 30B was not detected, and we infer an upper limit on its X-ray Luminosity of LX ≲ 3.0 × 1027 erg s-1. We measured a decrease in visual extinction towards TWA 30A (from AV ≈ 14.9 to AV ≈ 4.7) between the two 2011 observing epochs, and we find evidence for a corresponding significant decrease in X-ray absorbing column (NH). The apparent correlated change in AV and NH is suggestive of variable obscuration of the stellar photosphere by disc material composed of both gas and dust. However, in both observations, the inferred NH to AV ratio is lower than that typical of the interstellar medium, suggesting that the disc is either depleted of gas or is deficient in metals in the gas phase.

  14. Imaging Discovery of a Low-Mass Companion Around HR 3549

    NASA Astrophysics Data System (ADS)

    Stapelfeldt, Karl; Mawet, Dimitri; David, Trevor; Bottom, Michael; Hinkley, Sasha; Padgett, Deborah; Mennesson, Bertrand; Serabyn, Eugene; Morales, Farisa Y.; Kuhn, Jonas

    2015-12-01

    We report the discovery of a low-mass companion to HR 3549 , an A0V star surrounded by a debris disk with a warm excess detected by WISE. We imaged the companion at the Very Large Telescope with NAOS-CONICA in the L-band in January 2013 and January 2015. The companion is at a projected separation of 80 AU and position angle of 157° . Our age estimate for this object corresponds to a mass in the range 15-80 M J , spanning the brown dwarf regime, and so HR 3549 b is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios.

  15. Faint dwarfs in nearby groups

    SciTech Connect

    Speller, Ryan; Taylor, James E. E-mail: taylor@uwaterloo.ca

    2014-06-20

    The number and distribution of dwarf satellite galaxies remain a critical test of cold dark matter-dominated structure formation on small scales. Until recently, observational information about galaxy formation on these scales has been limited mainly to the Local Group. We have searched for faint analogues of Local Group dwarfs around nearby bright galaxies, using a spatial clustering analysis of the photometric catalog of the Sloan Digital Sky Survey (SDSS) Data Release 8. Several other recent searches of SDSS have detected clustered satellite populations down to Δm{sub r} ≡ (m{sub r,} {sub sat} – m{sub r,} {sub main}) ∼ 6-8, using photometric redshifts to reduce background contamination. SDSS photometric redshifts are relatively imprecise, however, for faint and nearby galaxies. Instead, we use angular size to select potential nearby dwarfs and consider only the nearest isolated bright galaxies as primaries. As a result, we are able to detect an excess clustering signal from companions down to Δm{sub r} = 12, 4 mag fainter than most recent studies. We detect an overdensity of objects at separations <400 kpc, corresponding to about 4.6 ± 0.5 satellites per central galaxy, consistent with the satellite abundance expected from the Local Group, given our selection function. Although the sample of satellites detected is incomplete by construction, since it excludes the least and most compact dwarfs, this detection provides a lower bound on the average satellite luminosity function, down to luminosities corresponding to the faintest ''classical'' dwarfs of the Local Group.

  16. Imaginary Companions of Preschool Children.

    ERIC Educational Resources Information Center

    Gleason, Tracy R.; Sebanc, Anne M.; Hartup, Willard W.

    2000-01-01

    Interviewed mothers to examine the developmental significance of preschoolers' imaginary companions. Found that relationships with invisible companions were described as sociable and friendly, whereas personified objects were usually nurtured. Object personification frequently occurred as a result of acquiring a toy; invisible friends were viewed…

  17. Recombination energy in double white dwarf formation

    NASA Astrophysics Data System (ADS)

    Nandez, J. L. A.; Ivanova, N.; Lombardi, J. C.

    2015-06-01

    In this Letter, we investigate the role of recombination energy during a common envelope event. We confirm that taking this energy into account helps to avoid the formation of the circumbinary envelope commonly found in previous studies. For the first time, we can model a complete common envelope event, with a clean compact double white dwarf binary system formed at the end. The resulting binary orbit is almost perfectly circular. In addition to considering recombination energy, we also show that between 1/4 and 1/2 of the released orbital energy is taken away by the ejected material. We apply this new method to the case of the double white dwarf system WD 1101+364, and we find that the progenitor system at the start of the common envelope event consisted of an ˜1.5 M⊙ red giant star in an ˜30 d orbit with a white dwarf companion.

  18. a Search for Companions around Stars Within Five Parsecs

    NASA Astrophysics Data System (ADS)

    Fazio, Giovanni; Megeath, Tom

    2004-09-01

    Each star known within 5 parsecs of the Sun will be observed with IRAC to discover very low mass companions. Simply because of their proximity, these targets promise to provide one of the most sensitive experiments possible with IRAC --- the detection of super-Jupiters around the nearest stars. Depending on distance and separation from the stars, companions with masses as low as 5-20 Mjup can be detected. The sample of 60 stars in 44 systems within 5 parsecs requires 45 IRAC pointings (Proxima Cen requires its own pointing because it is two degrees from alpha Cen). The sample includes 4 white dwarfs, 1 A star (Sirius), 1 F star (Procyon), 2 G stars (alpha Cen A and tau Ceti), 6 K stars, and 46 M stars. These stars comprise 30 single systems, 10 doubles, and 3 triples, as well as the nearest star with a probable extrasolar planet, Gl 876.

  19. VizieR Online Data Catalog: Overlooked wide companions of nearby F stars (Scholz, 2016)

    NASA Astrophysics Data System (ADS)

    Scholz, R.-D.

    2016-02-01

    We checked a sample of 545 F stars within 50pc for wide companions using existing near-infrared and optical sky surveys. Applying the common proper motion (CPM) criterion, we detected wide companion candidates with 6-120arcsec angular separations by visual inspection of multi-epoch finder charts and by searching in proper motion catalogues. Final proper motions were measured by involving positional measurements from up to eleven surveys. Spectral types of red CPM companions were estimated from their absolute J-band magnitudes based on the Hipparcos distances of the primaries. In addition to about 100 known CPM objects, we found 19 new CPM companions and confirmed 31 previously known candidates. A few CPM objects are still considered as candidates according to their level of proper motion agreement. Among the new objects there are nine M0-M4, eight M5-M6, one ~L3.5 dwarf (HD 3861B), and one white dwarf (WD) (HD 2726B), whereas we confirmed two K, 19 M0-M4, six M5-M6, two early-L dwarfs, and two DA WDs as CPM companions. In a few cases, previous spectral types were available that all agree well with our estimates. Two companions (HD 22879B and HD 49933B) are associated with moderately metal-poor Gaia benchmark stars. One doubtful CPM companion, spectroscopically classified as WD but found to be very bright (J=11.1) by others, should either be a very nearby foreground WD or a different kind of object associated with HD 165670. The main results of this research note, data on new, confirmed, and rejected CPM pairs, are listed in tablea1.dat, tableb1.dat, and tablec1.dat, respectively. (4 data files).

  20. M Dwarf Multiplicity in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Winters, Jennifer G.

    2015-01-01

    Stellar multiplicity provides fundamental clues about the nature of star formation, the evolution of stellar systems over time, and the distribution of baryonic mass in the Universe. How stars are parceled into singles, doubles, and higher order multiples also provides clues about the angular momentum distribution in stellar systems and constraints on whether or not planets may be found. Because of their large numbers, arguably the best sample that can be studied to understand stellar multiplicity are the nearby M dwarfs.Previous companion searches for M dwarfs have had sample sizes on the order of 100 stars, resulting in a weak statistical understanding of the distribution of companions. We have systematically surveyed ~1250 red dwarfs that have trigonometric parallaxes placing them within 25 pc of the Sun for stellar companions at separations of 1" to 10'. Because the systems all have accurate parallaxes, biases inherent to photometrically-selected samples are eliminated. We obtained I-band images using the CTIO/SMARTS 0.9m in the south and the Lowell 42in in the north, probing the environs of these systems for companions at separations of 1" to 3'. A complementary reconnaissance of wider companions out to 10' was also done via blinking of SuperCOSMOS archival BRI images. In addition, we have have long-term astrometric information on hundreds of the stars that can be used to estimate the number of companions closer than 1", and we have incorporated results from radial velocity work as well.The results allow statistical analyses of the nearby M dwarf population, refinement of the solar neighborhood membership roster, and improvement of the mass function for these objects at the end of the main sequence. This is the largest, most comprehensive study ever done of the multiplicity of the most common stars in the Galaxy.This work is supported by NSF grant AST 09-08402, the Sigma Xi Grants-in-Aid-of-Research Program, the SMARTS Consortium, and Georgia State University.

  1. Massive double white dwarfs and the AM CVn birthrate

    NASA Astrophysics Data System (ADS)

    Kilic, Mukremin; Brown, Warren R.; Heinke, Craig O.; Gianninas, A.; Benni, P.; Agüeros, M. A.

    2016-08-01

    We present Chandra and Swift X-ray observations of four extremely low-mass (ELM) white dwarfs with massive companions. We place stringent limits on X-ray emission from all four systems, indicating that neutron star companions are extremely unlikely and that the companions are almost certainly white dwarfs. Given the observed orbital periods and radial velocity amplitudes, the total masses of these binaries are greater than 1.02-1.39 M⊙. The extreme mass ratios between the two components make it unlikely that these binary white dwarfs will merge and explode as Type Ia or underluminous supernovae. Instead, they will likely go through stable mass transfer through an accretion disc and turn into interacting AM CVn. Along with three previously known systems, we identify two of our targets, J0811 and J2132, as systems that will definitely undergo stable mass transfer. In addition, we use the binary white dwarf sample from the ELM Survey to constrain the inspiral rate of systems with extreme mass ratios. This rate, 1.7 × 10-4 yr-1, is consistent with the AM CVn space density estimated from the Sloan Digital Sky Survey. Hence, stable mass transfer double white dwarf progenitors can account for the entire AM CVn population in the Galaxy.

  2. A CROSS-MATCH OF 2MASS AND SDSS. II. PECULIAR L DWARFS, UNRESOLVED BINARIES, AND THE SPACE DENSITY OF T DWARF SECONDARIES

    SciTech Connect

    Geissler, Kerstin; Metchev, Stanimir; Kirkpatrick, J. Davy; Berriman, G. Bruce; Looper, Dagny

    2011-05-01

    We present the completion of a program to cross-correlate the Sloan Digital Sky Survey Data Release 1 (SDSS DR1) and Two-Micron All-Sky Survey (2MASS) Point Source Catalog in search for extremely red L and T dwarfs. The program was initiated by Metchev and collaborators, who presented the findings on all newly identified T dwarfs in SDSS DR1 and estimated the space density of isolated T0-T8 dwarfs in the solar neighborhood. In the current work, we present most of the L dwarf discoveries. Our red-sensitive (z - J {>=} 2.75 mag) cross-match proves to be efficient in detecting peculiarly red L dwarfs, adding two new ones, including one of the reddest known L dwarfs. Our search also nets a new peculiarly blue L7 dwarf and, surprisingly, two M8 dwarfs. We further broaden our analysis to detect unresolved binary L or T dwarfs through spectral template fitting to all L and T dwarfs presented here and in the earlier work by Metchev and collaborators. We identify nine probable binaries, six of which are new and eight harbor likely T dwarf secondaries. We combine this result with current knowledge of the mass ratio distribution and frequency of substellar companions to estimate an overall space density of 0.005-0.05 pc{sup -3} for individual T0-T8 dwarfs.

  3. Measuring the mass of a pre-main sequence binary star through the orbit of TWA5A

    SciTech Connect

    Konopacky, Q; Ghez, A; Duchene, G; McCabe, C; Macintosh, B

    2007-01-18

    We present the results of a five year monitoring campaign of the close binary TWA 5Aab in the TW Hydrae association, using speckle and adaptive optics on the W.M. Keck 10 m telescopes. These measurements were taken as part of our ongoing monitoring of pre-main sequence (PMS) binaries in an effort to increase the number of dynamically determined PMS masses and thereby calibrate the theoretical PMS evolutionary tracks. Our observations have allowed us to obtain the first determination of this system's astrometric orbit. We find an orbital period of 5.94 {+-} 0.09 years and a semi-major axis of 0.''066 {+-} 0.''005. Combining these results with a kinematic distance, we calculate a total mass of 0.71 {+-} 0.14 M{sub {circle_dot}} (D/44 pc){sup 3}. for this system. This mass measurement, as well as the estimated age of this system, are consistent to within 2{sigma} of all theoretical models considered. In this analysis, we properly account for correlated uncertainties, and show that while these correlations are generally ignored, they increase the formal uncertainties by up to a factor of five and therefore are important to incorporate. With only a few more years of observation, this type of measurement will allow the theoretical models to be distinguished.

  4. A Common Proper Motion Stellar Companion to HAT-P-7

    NASA Astrophysics Data System (ADS)

    Narita, Norio; Takahashi, Yasuhiro H.; Kuzuhara, Masayuki; Hirano, Teruyuki; Suenaga, Takuya; Kandori, Ryo; Kudo, Tomoyuki; Sato, Bun'ei; Suzuki, Ryuji; Ida, Shigeru; Nagasawa, Makiko; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Egner, Sebastian E.; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hashimoto, Jun; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Janson, Markus; Knapp, Gillian R.; Kusakabe, Nobuhiko; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W.; Miyama, Shoken M.; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suto, Hiroshi; Takami, Michihiro; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Tomono, Daigo; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John P.; Yamada, Toru; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2012-12-01

    We report that HAT-P-7 has a common proper motion stellar companion. The companion is located at ˜3."9 to the east and estimated to be an M5.5V dwarf based on its colors. We also confirm the presence of a third companion, which was first reported by Winn et al. (2009, ApJ, 703, L99), based on long-term radial velocity measurements. We revisit the migration mechanism of HAT-P-7b given to the presence of those companions, and propose the sequential Kozai migration as a likely scenario in this system. This scenario may explain the reason for an outlier in the discussion of the spin-orbit alignment timescale for HAT-P-7b by Albrecht et al. (2012, ApJ, 757, 18).

  5. A Common Proper Motion Stellar Companion to HAT-P-7

    NASA Technical Reports Server (NTRS)

    Grady, Carol A.; McElwain, Michael W.; Narita, Norio; Takahashi, Yasuhiro H.; Kuzuhara, Masayuki; Hirano, Teruyuki; Suenaga, Takuya

    2012-01-01

    We report that HAT-P-7 has a common proper motion stellar companion. The companion is located at approx. 3.9 arcsec to the east and estimated as an M5.5V dwarf based on its colors. We also confirm the presence of the third companion, which was first reported by Winn et al. (2009), based on long-term radial velocity measurements. We revisit the migration mechanism of HAT-P-7b given the presence of those companions, and propose sequential Kozai migration as a likely scenario in this system. This scenario may explain the reason for an outlier in the discussion of the spin-orbit alignment timescale for HAT-P-7b by Albrecht et al. (2012).

  6. Formation of Brown Dwarfs LTSA 2001

    NASA Technical Reports Server (NTRS)

    Luhman, Kevin L.; Oliversen, Ronald J. (Technical Monitor)

    2003-01-01

    The goals of the work funded by this grant are: 1) The measurement of the mass function and minimum mass of free-floating brown dwarfs down to the mass of Jupiter; 2) The measurement of the frequency of wide brown dwarf and planetary companions down to the mass of Jupiter as function of primary mass (0.02-2 Msun), age (1-10 Myr), and environment (clusters vs. dispersed regions). For the first objective, we have completed the design of guaranteed SIRTF observations of nearby star-forming regions. With the successful launch of the SIRTF mission in August of 2003, we now await the execution of these observations, which should begin in early 2004. In support of these upcoming observations, in the fall of 2002 and spring of 2003 we obtained optical spectroscopy at the MMT, the 1.5 meter telescope at Fred Lawrence Whipple Observatory, and Magellan Observatory for several hundred candidate young low-mass stars and brown dwarfs in the IC348, Taurus, and Chamaeleon star-forming regions. All of these data have been published in three papers in The Astrophysical Journal. We also recently used the MMT to obtain deep near-IR images of IC348 to accompany the SIRTF images and have time in the next month at the IRTF and Keck for spectroscopy of candidate brown dwarfs in IC348 and Taurus. We have submitted proposals for deep optical and near-IR imaging of the SIRTF fields in Chamaeleon and Ophiuchus for spring 2004 with Magellan and the AAT. Results from this research have been presented in invited talks at UU Symposium 221 (July 2003) and at the SIRTF Galactic Science Workshop (August 2003). For the second objective, we have used deep HST WFPC2 images to search for young giant planets and brown dwarfs around approx. 100 low-mass stars and brown dwarfs in the nearby cluster IC348. We have completed all data reduction and have checked these data for candidate companions. We expect to submit the paper describing these observations to The Astrophysical Journal by the end of the year

  7. FINDING DWARF GALAXIES FROM THEIR TIDAL IMPRINTS

    SciTech Connect

    Chakrabarti, Sukanya; Bigiel, Frank; Chang, Philip; Blitz, Leo E-mail: chang65@uwm.edu

    2011-12-10

    We describe ongoing work on a new method that allows one to approximately determine the mass and relative position (in galactocentric radius and azimuth) of galactic companions purely from analysis of observed disturbances in gas disks. We demonstrate the validity of this method, which we call Tidal Analysis, by applying it to local spirals with known optical companions, namely M51 and NGC 1512. These galaxies span the range from having a very low mass companion ({approx}one-hundredth the mass of the primary galaxy) to a fairly massive companion ({approx}one-third the mass of the primary galaxy). This approach has broad implications for many areas of astrophysics-for the indirect detection of dark matter (or dark-matter-dominated dwarf galaxies), and for galaxy evolution in its use to decipher the dynamical impact of satellites on galactic disks. Here, we provide a proof of principle of the method by applying it to infer and quantitatively characterize optically visible galactic companions of local spirals, from the analysis of observed disturbances in outer gas disks.

  8. Prospecting in ultracool dwarfs: measuring the metallicities of mid- and late-M dwarfs

    SciTech Connect

    Mann, Andrew W.; Deacon, Niall R.; Gaidos, Eric; Ansdell, Megan; Liu, Michael C.; Magnier, Eugene A.; Aller, Kimberly M.; Brewer, John M.

    2014-06-01

    Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. The low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R ∼ 2000) K-band (≅ 2.2 μm) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early-M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early-M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to ∼0.07 dex for M4.5-M9.5 dwarfs with –0.58 < [Fe/H] < +0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolved binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.

  9. Companions to APOGEE Stars. I. A Milky Way-spanning Catalog of Stellar and Substellar Companion Candidates and Their Diverse Hosts

    NASA Astrophysics Data System (ADS)

    Troup, Nicholas W.; Nidever, David L.; De Lee, Nathan; Carlberg, Joleen; Majewski, Steven R.; Fernandez, Martin; Covey, Kevin; Chojnowski, S. Drew; Pepper, Joshua; Nguyen, Duy T.; Stassun, Keivan; Nguyen, Duy Cuong; Wisniewski, John P.; Fleming, Scott W.; Bizyaev, Dmitry; Frinchaboy, Peter M.; García-Hernández, D. A.; Ge, Jian; Hearty, Fred; Meszaros, Szabolcs; Pan, Kaike; Allende Prieto, Carlos; Schneider, Donald P.; Shetrone, Matthew D.; Skrutskie, Michael F.; Wilson, John; Zamora, Olga

    2016-03-01

    In its three years of operation, the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE-1) observed >14,000 stars with enough epochs over a sufficient temporal baseline for the fitting of Keplerian orbits. We present the custom orbit-fitting pipeline used to create this catalog, which includes novel quality metrics that account for the phase and velocity coverage of a fitted Keplerian orbit. With a typical radial velocity precision of ˜100-200 m s-1, APOGEE can probe systems with small separation companions down to a few Jupiter masses. Here we present initial results from a catalog of 382 of the most compelling stellar and substellar companion candidates detected by APOGEE, which orbit a variety of host stars in diverse Galactic environments. Of these, 376 have no previously known small separation companion. The distribution of companion candidates in this catalog shows evidence for an extremely truncated brown dwarf (BD) desert with a paucity of BD companions only for systems with a\\quad \\lt 0.1-0.2 AU, with no indication of a desert at larger orbital separation. We propose a few potential explanations of this result, some which invoke this catalog’s many small separation companion candidates found orbiting evolved stars. Furthermore, 16 BD and planet candidates have been identified around metal-poor ([Fe/H] < -0.5) stars in this catalog, which may challenge the core accretion model for companions \\gt 10{M}{Jup}. Finally, we find all types of companions are ubiquitous throughout the Galactic disk with candidate planetary-mass and BD companions to distances of ˜6 and ˜16 kpc, respectively.

  10. Naming Disney's Dwarfs.

    ERIC Educational Resources Information Center

    Sidwell, Robert T.

    1980-01-01

    Discusses Disney's version of the folkloric dwarfs in his production of "Snow White" and weighs the Disney rendition of the dwarf figure against the corpus of traits and behaviors pertaining to dwarfs in traditional folklore. Concludes that Disney's dwarfs are "anthropologically true." (HOD)

  11. Are All Dwarf Carbon Stars Binary?

    NASA Astrophysics Data System (ADS)

    Farihi, Jay; Harris, Hugh; Subasavage, John; Bergfors, Carolina; Green, Paul; Gansicke, Boris

    2014-08-01

    The origin of dwarf carbon stars is a persistent astrophysical curiosity dating back to 1977. Only giant stars dredge up interior carbon, and hence the discovery of an unevolved dwarf star with C/O >1 was a big surprise. Astronomers are no closer to understanding these rare and spectrally peculiar stars 37 years later(!). The bulk of dwarf carbon stars show no sign of an evolved companion necessary to account for their externally polluted atmospheres. These stars are sensitive tracers of Galactic chemical evolution and star formation, and provide strong constraints on the potential for carbon-dominated (single star) planetary systems. We propose to conclusively validate or refute the hypothetical binary nature of dwarf carbon stars, and hence their chemical and physical formation channel(s). For all binaries, we will initially constrain and eventually measure orbital periods. By determining their physical separation during the previous epoch of mass transfer, we will distinguish between the Roche lobe overflow and wind capture models for the creation of carbon dwarfs.

  12. KECK NIRSPEC RADIAL VELOCITY OBSERVATIONS OF LATE-M DWARFS

    SciTech Connect

    Tanner, Angelle; White, Russel; Bailey, John; Blake, Cullen; Blake, Geoffrey; Cruz, Kelle; Burgasser, Adam J.; Kraus, Adam

    2012-11-15

    We present the results of an infrared spectroscopic survey of 23 late-M dwarfs with the NIRSPEC echelle spectrometer on the Keck II telescope. Using telluric lines for wavelength calibration, we are able to achieve measurement precisions of down to 45 m s{sup -1} for our late-M dwarfs over a one- to four-year long baseline. Our sample contains two stars with radial velocity (RV) variations of >1000 m s{sup -1}. While we require more measurements to determine whether these RV variations are due to unseen planetary or stellar companions or are the result of starspots known to plague the surface of M dwarfs, we can place upper limits of <40 M{sub J} sin i on the masses of any companions around those two M dwarfs with RV variations of <160 m s{sup -1} at orbital periods of 10-100 days. We have also measured the rotational velocities for all the stars in our late-M dwarf sample and offer our multi-order, high-resolution spectra over 2.0-2.4 {mu}m to the atmospheric modeling community to better understand the atmospheres of late-M dwarfs.

  13. Metallicity determination of M dwarfs. High-resolution infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Lindgren, Sara; Heiter, Ulrike; Seifahrt, Andreas

    2016-02-01

    Context. Several new techniques to determine the metallicity of M dwarfs with better precision have been developed over the last decades. However, most of these studies were based on empirical methods. In order to enable detailed abundance analysis, standard methods established for warmer solar-like stars, i.e. model-dependent methods using fitting of synthetic spectra, still need to be used. Aims: In this work we continue the reliability confirmation and development of metallicity determinations of M dwarfs using high-resolution infrared spectra. The reliability was confirmed through analysis of M dwarfs in four binary systems with FGK dwarf companions and by comparison with previous optical studies of the FGK dwarfs. Methods: The metallicity determination was based on spectra taken in the J band (1.1-1.4 μm) with the CRIRES spectrograph. In this part of the infrared, the density of stellar molecular lines is limited, reducing the amount of blends with atomic lines enabling an accurate continuum placement. Lines of several atomic species were used to determine the stellar metallicity. Results: All binaries show excellent agreement between the derived metallicity of the M dwarf and its binary companion. Our results are also in good agreement with values found in the literature. Furthermore, we propose an alternative way to determine the effective temperature of M dwarfs of spectral types later than M2 through synthetic spectral fitting of the FeH lines in our observed spectra. Conclusions: We have confirmed that a reliable metallicity determination of M dwarfs can be achieved using high-resolution infrared spectroscopy. We also note that metallicites obtained with photometric metallicity calibrations available for M dwarfs only partly agree with the results we obtain from high-resolution spectroscopy. Based on data obtained at ESO-VLT, Paranal Observatory, Chile, Program ID 082.D-0838(A) and 084.D-1042(A).

  14. The M-dwarfs in Multiples (MinMs) Survey - Stellar Multiplicity within 15 pc

    NASA Astrophysics Data System (ADS)

    Ward-Duong, K.; Patience, J.; Rosa, R. J. De; Bulger, J.; Rajan, A.; McCarthy, D.; Kulesa, C.; Goodwin, S.; Parker, R.

    2015-01-01

    We present results from a large-scale, comprehensive M-dwarf companion study based on a volume-limited survey of 245 M-dwarfs within 15 pc. Diffraction-limited infrared archival data were analyzed to detect nearby companions to M-dwarfs from ˜1 to 100 AU. To supplement the high-resolution data, digitized wide-field archival plates were searched for companions with separations of 100 to 10,000 AU. The survey is fully sensitive to companions at the bottom of the main sequence over an unprecedented survey separation range of ˜3 to 10,000 AU, and the deepest images also reveal a number of substellar candidates. With multiple AO and wide-field epochs, follow-up observations have allowed us to confirm or reject companion candidates detected during our analysis. This provides confirmation of common proper motions, minimizes background contamination, and enables comprehensive statistics, including separation and mass ratio distributions, for M-dwarf binaries. Characterizations of the binary and multiple star frequency for M-dwarfs provide crucial insights into the low-mass star formation environment, and hold additional implications for the frequency and evolutionary histories of their associated disks and planets.

  15. Ultraviolet emission from main-sequence companions of AGB stars

    NASA Astrophysics Data System (ADS)

    Ortiz, Roberto; Guerrero, Martín A.

    2016-09-01

    Although the majority of known binary asymptotic giant branch (AGB) stars are symbiotic systems (i.e. with a white dwarf as a secondary star), main-sequence companions of AGB stars can be more numerous, even though they are more difficult to find because the primary high luminosity hampers the detection of the companion at visual wavelengths. However, in the ultraviolet the flux emitted by a secondary with Teff > 5500 ˜ 6000 K may prevail over that of the primary, and then it can be used to search for candidates to binary AGB stars. In this work, theoretical atmosphere models are used to calculate the UV excess in the GALEX near- and far-UV bands due to a main-sequence companion. After analysing a sample of confirmed binary AGB stars, we propose as a criterium for binarity: (1) the detection of the AGB star in the GALEX far-UV band and/or (2) a GALEX near-UV observed-to-predicted flux ratio >20. These criteria have been applied to a volume-limited sample of AGB stars within 500 pc of the Sun; 34 out of the sample of 58 AGB stars (˜60 per cent) fulfill them, implying to have a main-sequence companion of spectral type earlier than K0. The excess in the GALEX near- and far-UV bands cannot be attributed to a single temperature companion star, thus suggesting that the UV emission of the secondary might be absorbed by the extended atmosphere and circumstellar envelope of the primary or that UV emission is produced in accretion flows.

  16. WISE Y dwarfs as probes of the brown dwarf-exoplanet connection

    SciTech Connect

    Beichman, C.; Gelino, Christopher R.; Kirkpatrick, J. Davy; Cushing, Michael C.; Dodson-Robinson, Sally; Marley, Mark S.; Morley, Caroline V.; Wright, E. L.

    2014-03-10

    We have determined astrometric positions for 15 WISE-discovered late-type brown dwarfs (six T8-9 and nine Y dwarfs) using the Keck-II telescope, the Spitzer Space Telescope, and the Hubble Space Telescope. Combining data from 8 to 20 epochs we derive parallactic and proper motions for these objects, which puts the majority within 15 pc. For ages greater than a few Gyr, as suggested from kinematic considerations, we find masses of 10-30 M {sub Jup} based on standard models for the evolution of low-mass objects with a range of mass estimates for individual objects, depending on the model in question. Three of the coolest objects have effective temperatures ∼350 K and inferred masses of 10-15 M {sub Jup}. Our parallactic distances confirm earlier photometric estimates and direct measurements and suggest that the number of objects with masses below about 15 M {sub Jup} must be flat or declining, relative to higher mass objects. The masses of the coldest Y dwarfs may be similar to those inferred for recently imaged planet-mass companions to nearby young stars. Objects in this mass range, which appear to be rare in both the interstellar and protoplanetary environments, may both have formed via gravitational fragmentation—the brown dwarfs in interstellar clouds and companion objects in a protoplanetary disk. In both cases, however, the fact that objects in this mass range are relatively infrequent suggests that this mechanism must be inefficient in both environments.

  17. DISCOVERY AND CHARACTERIZATION OF A FAINT STELLAR COMPANION TO THE A3V STAR zeta VIRGINIS

    SciTech Connect

    Hinkley, Sasha; Hillenbrand, Lynne; Oppenheimer, Ben R.; Brenner, Douglas; Zimmerman, Neil; Sivaramakrishnan, Anand; Roberts, Lewis C.; Roberts, Jennifer E.; Burruss, Rick; Shao, Michael; Vasisht, Gautam; Parry, Ian R.; King, David L.; Soummer, Remi; Simon, Michal; Perrin, Marshall D.; Lloyd, James P.; Bouchez, Antonin; Dekany, Richard; Beichman, Charles

    2010-03-20

    Through the combination of high-order adaptive optics and coronagraphy, we report the discovery of a faint stellar companion to the A3V star zeta Virginis. This companion is {approx}7 mag fainter than its host star in the H band, and infrared imaging spanning 4.75 years over five epochs indicates this companion has common proper motion with its host star. Using evolutionary models, we estimate its mass to be 0.168{sup +0.012}{sub -0.016} M{sub sun}, giving a mass ratio for this system q = 0.082{sup +0.007}{sub -0.008}. Assuming the two objects are coeval, this mass suggests an M4V-M7V spectral type for the companion, which is confirmed through {integral} field spectroscopic measurements. We see clear evidence for orbital motion from this companion and are able to constrain the semimajor axis to be {approx}>24.9 AU, the period {approx}>124 yr, and eccentricity {approx}>0.16. Multiplicity studies of higher mass stars are relatively rare, and binary companions such as this one at the extreme low end of the mass ratio distribution are useful additions to surveys incomplete at such a low mass ratio. Moreover, the frequency of binary companions can help to discriminate between binary formation scenarios that predict an abundance of low-mass companions forming from the early fragmentation of a massive circumstellar disk. A system such as this may provide insight into the anomalous X-ray emission from A stars, hypothesized to be from unseen late-type stellar companions. Indeed, we calculate that the presence of this M-dwarf companion easily accounts for the X-ray emission from this star detected by ROSAT.

  18. The κ Andromedae system: new constraints on the companion mass, system age, and further multiplicity

    SciTech Connect

    Hinkley, Sasha; David, Trevor; Hillenbrand, Lynne A.; Pueyo, Laurent; Faherty, Jacqueline K.; Oppenheimer, Ben R.; Brenner, Douglas; Veicht, Aaron; Nilsson, Ricky; Mamajek, Eric E.; Kraus, Adam L.; Rice, Emily L.; Ireland, Michael J.; Vasisht, Gautam; Cady, Eric; Roberts, Jennifer E.; Zimmerman, Neil; Parry, Ian R.; Beichman, Charles; Dekany, Richard; and others

    2013-12-20

    κ Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 ± 2 AU was recently announced. In this work, we present the first spectrum of the companion, 'κ And B,' using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ∼2000 K as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and T {sub eff} measurements of the host star to argue that the κ And system has an isochronal age of 220 ± 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of κ And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to κ And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly 'pole-on' viewing angle coupled with extremely rapid rotation is unlikely. κ And A is thus consistent with its slightly evolved luminosity class (IV), and we propose here that κ And, with a revised age of 220 ± 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for κ And B combined with our reassessment of the system age implies a substellar companion mass of 50{sub −13}{sup +16} M {sub Jup}, consistent with a brown dwarf rather than a planetary-mass companion.

  19. The κ Andromedae System: New Constraints on the Companion Mass, System Age, and Further Multiplicity

    NASA Astrophysics Data System (ADS)

    Hinkley, Sasha; Pueyo, Laurent; Faherty, Jacqueline K.; Oppenheimer, Ben R.; Mamajek, Eric E.; Kraus, Adam L.; Rice, Emily L.; Ireland, Michael J.; David, Trevor; Hillenbrand, Lynne A.; Vasisht, Gautam; Cady, Eric; Brenner, Douglas; Veicht, Aaron; Nilsson, Ricky; Zimmerman, Neil; Parry, Ian R.; Beichman, Charles; Dekany, Richard; Roberts, Jennifer E.; Roberts, Lewis C., Jr.; Baranec, Christoph; Crepp, Justin R.; Burruss, Rick; Wallace, J. Kent; King, David; Zhai, Chengxing; Lockhart, Thomas; Shao, Michael; Soummer, Rémi; Sivaramakrishnan, Anand; Wilson, Louis A.

    2013-12-01

    κ Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 ± 2 AU was recently announced. In this work, we present the first spectrum of the companion, "κ And B," using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ~2000 K as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and T eff measurements of the host star to argue that the κ And system has an isochronal age of 220 ± 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of κ And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to κ And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly "pole-on" viewing angle coupled with extremely rapid rotation is unlikely. κ And A is thus consistent with its slightly evolved luminosity class (IV), and we propose here that κ And, with a revised age of 220 ± 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for κ And B combined with our reassessment of the system age implies a substellar companion mass of 50^{+16}_{-13} M Jup, consistent with a brown dwarf rather than a planetary-mass companion.

  20. Evidence for a Companion to BM Gem, a Silicate Carbon Star

    NASA Astrophysics Data System (ADS)

    Izumiura, Hideyuki; Noguchi, Kunio; Aoki, Wako; Honda, Satoshi; Ando, Hiroyasu; Takada-Hidai, Masahide; Kambe, Eiji; Kawanomoto, Satoshi; Sadakane, Kozo; Sato, Bun'ei; Tajitsu, Akito; Tanaka, Wataru; Okita, Ki'ichi; Watanabe, Etsuji; Yoshida, Michitoshi

    2008-07-01

    Balmer and Paschen continuum emission, as well as Balmer series lines of P Cygni-type profile from Hγ through H23, are revealed in the violet spectra of BM Gem, a carbon star associated with an oxygen-rich circumstellar shell ("silicate carbon star"). The blueshifted absorption in the Balmer lines indicates the presence of an outflow, the line-of-sight velocity of which is at least 400 km s-1. The Balmer lines show a significant change in profile over a period of 75 days. We argue that the observed unusual features in BM Gem are strong evidence for the presence of a companion, which should form an accretion disk that gives rise to both an ionized gas region and a high-velocity variable outflow. The estimated luminosity of ~0.2 (0.03-0.6) L⊙ for the ionized gas can be maintained by a mass accretion rate for a dwarf companion of ~10-8 M⊙ yr-1, while ~10-10 M⊙ yr-1 is sufficient for accretion to a white dwarf companion. These accretion rates are feasible for some detached binary configurations on the basis of the Bondi-Hoyle-type accretion process. Therefore, we conclude that the carbon star BM Gem is in a detached binary system with a companion of low mass and low luminosity. However, we are unable to determine whether this companion object is a dwarf or a white dwarf, although the gas outflow velocity of 400 km s-1, as well as the nondetection in the X-ray survey, favor its identity as a dwarf star. The upper limits for binary separation are 210 and 930 AU for a dwarf and a white dwarf, respectively, in the case of circular orbit. We also note that the observed features of BM Gem mimic those of Mira (ο Cet), which may suggest actual similarities in their binary configurations and circumstellar structures. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  1. AN H-BAND SPECTROSCOPIC METALLICITY CALIBRATION FOR M DWARFS

    SciTech Connect

    Terrien, Ryan C.; Mahadevan, Suvrath; Bender, Chad F.; Deshpande, Rohit; Ramsey, Lawrence W.; Bochanski, John J.

    2012-03-10

    We present an empirical near-infrared (NIR) spectroscopic method for estimating M dwarf metallicities, based on features in the H band, as well as an implementation of a similar published method in the K band. We obtained R {approx} 2000 NIR spectra of a sample of M dwarfs using the NASA IRTF-SpeX spectrograph, including 22 M dwarf metallicity calibration targets that have FGK companions with known metallicities. The H-band and K-band calibrations provide equivalent fits to the metallicities of these binaries, with an accuracy of {+-}0.12 dex. We derive the first empirically calibrated spectroscopic metallicity estimate for the giant planet-hosting M dwarf GJ 317, confirming its supersolar metallicity. Combining this result with observations of eight other M dwarf planet hosts, we find that M dwarfs with giant planets are preferentially metal-rich compared to those that host less massive planets. Our H-band calibration relies on strongly metallicity-dependent features in the H band, which will be useful in compositional studies using mid- to high-resolution NIR M dwarf spectra, such as those produced by multiplexed surveys like SDSS-III APOGEE. These results will also be immediately useful for ongoing spectroscopic surveys of M dwarfs.

  2. THE NIRSPEC ULTRACOOL DWARF RADIAL VELOCITY SURVEY

    SciTech Connect

    Blake, Cullen H.; Charbonneau, David; White, Russel J.

    2010-11-01

    We report the results of an infrared Doppler survey designed to detect brown dwarf and giant planetary companions to a magnitude-limited sample of ultracool dwarfs. Using the NIRSPEC spectrograph on the Keck II telescope, we obtained approximately 600 radial velocity (RV) measurements over a period of six years of a sample of 59 late-M and L dwarfs spanning spectral types M8/L0 to L6. A subsample of 46 of our targets has been observed on three or more epochs. We rely on telluric CH{sub 4} absorption features in Earth's atmosphere as a simultaneous wavelength reference and exploit the rich set of CO absorption features found in the K-band spectra of cool stars and brown dwarfs to measure RVs and projected rotational velocities. For a bright, slowly rotating M dwarf standard we demonstrate an RV precision of 50 m s{sup -1} and for slowly rotating L dwarfs we achieve a typical RV precision of approximately 200 m s{sup -1}. This precision is sufficient for the detection of close-in giant planetary companions to mid-L dwarfs as well as more equal mass spectroscopic binary systems with small separations (a < 2 AU). We present an orbital solution for the subdwarf binary LSR1610 - 0040 as well as an improved solution for the M/T binary 2M0320 - 04. We compare the distribution of our observed values for the projected rotational velocities, Vsin i, to those in the literature and find that our sample contains examples of slowly rotating mid-L dwarfs, which have not been seen in other surveys. We also combine our RV measurements with distance estimates and proper motions from the literature and estimate the dispersion of the space velocities of the objects in our sample. Using a kinematic age estimate, we conclude that our UCDs have an age of 5.0{sup +0.7}{sub -0.6} Gyr, similar to that of nearby sun-like stars. We simulate the efficiency with which we detect spectroscopic binaries and find that the rate of tight (a < 1 AU) binaries in our sample is 2.5{sup +8.6}{sub -1

  3. Population Synthesis of Rapidly Rotating Main-Sequence Stars with Companions

    NASA Astrophysics Data System (ADS)

    Raguzova, N. V.

    2003-05-01

    Usingthe “Scenario Machine” (a specialized numerical code formodeling the evolution of large ensembles of binary systems), we have studied the physical properties of rapidly rotating main-sequence binary stars (Be stars) with white-dwarf companions and their abundance in the Galaxy. The calculations are the first to take into account the cooling of the compact object and the effect of synchronization of the rotation on the evolution of Be stars in close binaries. The synchronization time scale can be shorter than the main-sequence lifetime of a Be star formed during the first mass transfer. This strongly influences the distribution of orbital periods for binary Be stars. In particular, it can explain the observed deficit of short-period Be binaries. According to our computations, the number of binary systems in the Galaxy containing a Be star and white dwarf is large: 70 80% of all Be stars in binaries should have degenerate dwarf companions. Based on our calculations, we conclude that the compact components in these systems have high surface temperatures. Despite their high surface temperatures, the detection of white dwarfs in such systems is hampered by the fact that the entire orbit of the white dwarf is embedded in the dense circumstellar envelope of the primary, and all the extreme-UV and soft X-ray emission of the compact object is absorbed by the Be star’s envelope. It may be possible to detect the white dwarfs via observations of helium emission lines of Be stars of not very early spectral types. The ultraviolet continuum energies of these stars are not sufficient to produce helium line emission. We also discuss numerical results for Be stars with other evolved companions, such as helium stars and neutron stars, and suggest an explanation for the absence of Be-black-hole binaries.

  4. Dwarf Galaxies in the Local Group and in the Local Volume (Invited Talk)

    NASA Astrophysics Data System (ADS)

    Grebel, E. K.

    After summarizing the characteristics of different types of dwarf galaxies I briefly review our current state of knowledge of dwarf galaxy evolution in the Local Group, for which we now have a fairly detailed although by no means comprehensive picture. All Local Group dwarfs studied to date contain an old population, though its fraction varies considerably. The majority of the dwarf companions of the Milky Way shows evidence for a common epoch of ancient star formation. Spatial variations in star formation are frequently observed in many dwarf galaxies in the Local Group and beyond. These spatial variations range from a seemingly stochastic distribution of star-forming regions in gas-rich, high-mass dwarfs to radial gradients in low-mass dwarfs. The global mode of star formation may be either continuous with amplitude variations or episodic. High-mass dwarf galaxies tend to form stars over a Hubble time, whereas low-mass dwarfs eventually cease to form stars, possibly aided by environmental effects. Much less is known about the content and properties of dwarf galaxies in the Local Volume, which we are trying to remedy through a large observational effort. Dwarf galaxies in the Local Volume follow a similar trend with absolute magnitude, mean metallicity, and central surface brightness as the Local Group dwarfs do, and appear to be subject to morphological segregation.

  5. White dwarf main-sequence binaries from SDSS DR 8: unveiling the cool white dwarf population

    NASA Astrophysics Data System (ADS)

    Rebassa-Mansergas, A.; Agurto-Gangas, C.; Schreiber, M. R.; Gänsicke, B. T.; Koester, D.

    2013-08-01

    The spectroscopic catalogue of white dwarf main-sequence (WDMS) binaries from the Sloan Digital Sky Survey (SDSS) is the largest and most homogeneous sample of compact binary stars currently known. However, because of selection effects, the current sample is strongly biased against systems containing cool white dwarfs and/or early-type companions, which are predicted to dominate the intrinsic population. In this study, we present colour selection criteria that combines optical (ugriz DR 8 SDSS) plus infrared (yjhk DR 9 UKIRT Infrared Sky Survey, JHK Two Micron All Sky Survey and/or w1w2 Wide-Field Infrared Survey Explorer) magnitudes to select 3419 photometric candidates of harbouring cool white dwarfs and/or dominant (M dwarf) companions. We demonstrate that 84 per cent of our selected candidates are very likely genuine WDMS binaries, and that the white dwarf effective temperatures and secondary star spectral types of 71 per cent of our selected sources are expected to be below ≲ 10 000-15 000 K, and concentrated at ˜M2-3, respectively. We also present an updated version of the spectroscopic SDSS WDMS binary catalogue, which incorporates 47 new systems from SDSS DR 8. The bulk of the DR 8 spectroscopy is made up of main-sequence stars and red giants that were targeted as part of the Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey, therefore the number of new spectroscopic WDMS binaries in DR 8 is very small compared to previous SDSS data releases. Despite their low number, DR 8 WDMS binaries are found to be dominated by systems containing cool white dwarfs and therefore represent an important addition to the spectroscopic sample. The updated SDSS DR 8 spectroscopic catalogue of WDMS binaries consists of 2316 systems. We compare our updated catalogue with recently published lists of WDMS binaries and conclude that it currently represents the largest, most homogeneous and cleanest sample of spectroscopic WDMS binaries from SDSS.

  6. Searching for Planets of Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Guenther, Eike; Wuchterl, Guenther

    2003-06-01

    Up to now, most planet search projects have concentrated on G and K stars. In order to considerably widen the view, we have stated a survey for planets of old, nearby brown dwarfs and very low-mass stars. Using UVES, we have observed 26 brown dwarfs and very low-mass stars. As it turned out these objects are very inactive and thus highly suitable for such a project. For 19 objects, we can exclude a planet with the mass of 3 M_J, and a period of 100 days or less with a probability of more than 60%. For these objects, we can also exclude Pegasi-planets with a high probability. For another 4 objects, we can exclude at least a brown dwarf companion. One object is a double line spectroscopic binary, and one object shows significant radial-velocity variations that can not be caused by a normal stellar-spot. This object either has a planetary-mass companion, or the variations are caused by surface structures that are quite different from normal star-spots. Based on observations obtained at the European Southern Observatory, Paranal (ESO). ESO Proposals 68.C-0063, 67.C-0160.

  7. Sirius B - A still mysterious white dwarf

    NASA Astrophysics Data System (ADS)

    Wesemael, F.; Fontaine, G.

    1982-02-01

    Observations and knowledge of Sirius B, the companion star to Sirius A are reviewed, noting the solar mass and terrestrial radius of the dwarf. The system is 2.65 pc distant, with separation between the stars oscillating from 8-32 AU. Spectral observations are best obtained when the stars are at maximum distance, and redshifts which affirm the theory of relativity have been detected. Copernicus satellite observations have also revealed the emissions of UV and X rays from the dwarf. It is noted that Grecian records over 2000 yr old cite Sirius as a red star, which implies that the dwarf was then a red star since Sirius A is a main sequence star, an implication which does not correspond with the known evolution of stars. Another mystery is cited, that of the tribal records of the Sudanese Dogon, which maintains an ancient legend of Sirius A having an invisible companion called Digitaria, composed of a substance called segala, which cannot be lifted by all the humans on earth combined.

  8. An astrometric search for a stellar companion to the sun

    SciTech Connect

    Perlmutter, S.

    1986-11-25

    A companion star within 0.8 pc of the Sun has been postulated to explain a possible 26 Myr periodicity in mass extinctions of species on the Earth. Such a star would already be catalogued in the Yale Bright Star catalogue unless it is fainter than m/sub nu/ = 6.5; this limits the possible stellar types for an unseen companion to red dwarfs, brown dwarfs, or compact objects. Red dwarfs account for about 75% of these possible stars. We describe here the design and development of an astrometric search for a nearby red dwarf companion with a six-month peak-to-peak parallax of greater than or equal to2.5 arcseconds. We are measuring the parallax of 2770 candidate faint red stars selected from the Dearborn Observatory catalogue. An automated 30-inch telescope and CCD camera system collect digitized images of the candidate stars, along with a 13' x 16' surrounding field of background stars. Second-epoch images, taken a few months later, are registered to the first epoch images using the background stars as fiducials. An apparent motion, m/sub a/, of the candidate stars is found to a precision of sigma/sub m//sub a/ approx. = 0.08 pixel approx. = 0.2 arcseconds for fields with N/sub fiducial/ greater than or equal to 10 fiducial stars visible above the background noise. This precision is sufficient to detect the parallactic motion of a star at 0.8 pc with a two month interval between the observation epochs. Images with fewer fiducial stars above background noise are observed with a longer interval between epochs. If a star is found with high parallactic motion, we will confirm its distance with further parallax measurements, photometry, and spectral studies, and will measure radial velocity and proper motion to establish its orbit. We have demonstrated the search procedure with observations of 41 stars, and have shown that none of these is a nearby star. 37 refs., 16 figs., 3 tabs.

  9. Exclusion of a luminous red giant as a companion star to the progenitor of supernova SN 2011fe.

    PubMed

    Li, Weidong; Bloom, Joshua S; Podsiadlowski, Philipp; Miller, Adam A; Cenko, S Bradley; Jha, Saurabh W; Sullivan, Mark; Howell, D Andrew; Nugent, Peter E; Butler, Nathaniel R; Ofek, Eran O; Kasliwal, Mansi M; Richards, Joseph W; Stockton, Alan; Shih, Hsin-Yi; Bildsten, Lars; Shara, Michael M; Bibby, Joanne; Filippenko, Alexei V; Ganeshalingam, Mohan; Silverman, Jeffrey M; Kulkarni, S R; Law, Nicholas M; Poznanski, Dovi; Quimby, Robert M; McCully, Curtis; Patel, Brandon; Maguire, Kate; Shen, Ken J

    2011-12-15

    Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are two classes of models: double-degenerate (involving two white dwarfs in a close binary system) and single-degenerate models. In the latter, the primary white dwarf accretes material from a secondary companion until conditions are such that carbon ignites, at a mass of 1.38 times the mass of the Sun. The type Ia supernova SN 2011fe was recently detected in a nearby galaxy. Here we report an analysis of archival images of the location of SN 2011fe. The luminosity of the progenitor system (especially the companion star) is 10-100 times fainter than previous limits on other type Ia supernova progenitor systems, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf. PMID:22170681

  10. Companions to peculiar red giants: HR 363 and HR 1105

    NASA Technical Reports Server (NTRS)

    Ake, Thomas B., III; Johnson, Hollis R.; Perry, Benjamin F., Jr.

    1988-01-01

    Recent IUE observations of two Tc-deficient S-type peculiar red giants that are also spectroscopic binaries, HR 363 and HR 1105 are reported. A 675 min SWP exposure of HR 363 shows emission lines of O I 1304 and Si II 1812 and a trace of continuum. Compared to the M giants, the far UV flux may be relatively larger, indicating a possible contribution from a white dwarf companion, but no high temperature emission lines are seen to indicate that this is an interacting system where mass-transfer recently occurred. However, HR 1105 appears to have a highly variable UV companion. In 1982, no UV flux was discerned for this system, but by 1986 C IV was strong, increasing by a factor of 3 in 1987 with prominent lines of Si III, C III, O III, Si IV, and N V. Using orbital parameters, these observations are consistent with high activity occuring when the side of the S-star primary illuminated by the companion faces the Earth, but since the IUE data were taken over 3 orbits, a secular change in the UV component cannot be excluded.

  11. Dark companions of stars - Astrometric commentary on the lower end of the Main Sequence

    NASA Astrophysics Data System (ADS)

    van de Kamp, P.

    1986-04-01

    The smaller the mass of a star, the lower its central temperature and the lower its luminosity. The zero-age Main Sequence is thus explained down to its lower, red dwarf section; there is, however, a critical mass value below which the central temperature is too low to permit conventional nuclear energy production, and the resulting objects are designated substellar, black, brown, or even 'dark red' stars. The present consideration of the dark companions of stars gives attention to visible and invisible dark dwarfs, as well as to the stars Sirius and Procyon, the planets Neptune and Pluto, spectroscopic, photometric, and eclipsing companion stars, the serendipitously discovered cases of Ross 614 and VW Cephei C, and astrometric study results for Barnard's star.

  12. SUB-STELLAR COMPANIONS AND STELLAR MULTIPLICITY IN THE TAURUS STAR-FORMING REGION

    SciTech Connect

    Daemgen, Sebastian; Bonavita, Mariangela; Jayawardhana, Ray; Lafrenière, David; Janson, Markus

    2015-02-01

    We present results from a large, high-spatial-resolution near-infrared imaging search for stellar and sub-stellar companions in the Taurus-Auriga star-forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at ∼3 M {sub ☉} and low-mass stars at ∼0.2 M {sub ☉}. We detected 74 companion candidates, 34 of these reported for the first time. Twenty-five companions are likely physically bound, partly confirmed by follow-up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as ∼2 M {sub Jup}. The inferred multiplicity frequency within our sensitivity limits between ∼10-1500 AU is 26.3{sub −4.9}{sup +6.6}%. Applying a completeness correction, 62% ± 14% of all Taurus stars between 0.7 and 1.4 M {sub ☉} appear to be multiple. Higher order multiples were found in 1.8{sub −1.5}{sup +4.2}% of the cases, in agreement with previous observations of the field. We estimate a sub-stellar companion frequency of ∼3.5%-8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low-mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub-populations in Taurus with ages of ∼2 Myr and ∼20 Myr, respectively.

  13. The Routledge Companion to Education

    ERIC Educational Resources Information Center

    Arthur, James, Ed.; Peterson, Andrew, Ed.

    2011-01-01

    "The Routledge Companion to Education" presents the most comprehensive, up-to-date guide available to the key theories, themes and topics in education. Forty specially commissioned chapters, covering all aspects of education, introduce you to the ideas, research and issues that have shaped this most diverse, dynamic and fluid field. Part one…

  14. K2 Survey of Ultracool Dwarfs

    NASA Astrophysics Data System (ADS)

    Gizis, John; Paudel, Rishi; Burgasser, Adam J.; Williams, Peter K. G.; Schmidt, Sarah J.

    2016-06-01

    We report on our ongoing survey using the Kepler/K2 telescope to monitor ultracool (late-M and L) dwarfs. The survey has three goals: To detect variability due to rotation, clouds and weather, to detect white light flares from magnetic reconnection events, and to detect transits from planetary companions. We discuss the challenges of observing faint, red source with a telescope originally designed for photometry of bright, solar-type stars. We discuss case studies from our initial sample, including evidence that a nearby (7.2 pc) brown dwarf is viewed pole-on, and the measurement of the white light flare rate from a 23-million-year 61-jupiter-mass.

  15. Observational Constraints on the White Dwarf Mass-Radius Relation

    NASA Astrophysics Data System (ADS)

    Dhital, Saurav; Oswalt, Terry D.; Holberg, J. B.; Zhao, Jingkun

    2014-08-01

    We propose to measure gravitational redshifts for white dwarf stars that have distant, non-interacting main-sequence companions. With independent radius constraints obtained from parallaxes and surface gravity determinations obtained by fitting the Balmer series from our spectra, we will make improved estimates of white dwarf masses and radii that can be critically compared with theoretical mass-radius relations specific to each star. These observations will allow us to examine serious discrepancies between the theoretical and empirical measurements of the white dwarf mass-radius relation and extend the range of masses over which it has been tested, spanning 0.5-1.2 Msun. Currently, the measured radius for only a single WD matches its predicted value within 5%. With the expected precision of ≲5% for over half the sample, we will also distinguish whether the white dwarfs have ``thick'' or ``thin'' H envelopes. Using the same spectra, we will also estimate the metallicity of the main-sequence companion and examine how the initial-final-mass ratio for WDs depends on metallicity. Thus, this project will put robust constraints on two fundamental relations that govern our understanding of white dwarfs: the mass-ratio and the initial-final-mass relations.

  16. THE ASTRALUX LARGE M-DWARF MULTIPLICITY SURVEY

    SciTech Connect

    Janson, Markus; Hormuth, Felix; Bergfors, Carolina; Brandner, Wolfgang; Hippler, Stefan; Kudryavtseva, Natalia; Schnupp, Carolin; Henning, Thomas; Daemgen, Sebastian; Schmalzl, Eva

    2012-07-20

    We present the results of an extensive high-resolution imaging survey of M-dwarf multiplicity using the Lucky Imaging technique. The survey made use of the AstraLux Norte camera at the Calar Alto 2.2 m telescope and the AstraLux Sur camera at the ESO New Technology Telescope in order to cover nearly the full sky. In total, 761 stars were observed (701 M-type and 60 late K-type), among which 182 new and 37 previously known companions were detected in 205 systems. Most of the targets have been observed during two or more epochs, and could be confirmed as physical companions through common proper motion, often with orbital motion being confirmed in addition. After accounting for various bias effects, we find a total M-dwarf multiplicity fraction of 27% {+-} 3% within the AstraLux detection range of 0.''08-6'' (semimajor axes of {approx}3-227 AU at a median distance of 30 pc). We examine various statistical multiplicity properties within the sample, such as the trend of multiplicity fraction with stellar mass and the semimajor axis distribution. The results indicate that M-dwarfs are largely consistent with constituting an intermediate step in a continuous distribution from higher-mass stars down to brown dwarfs. Along with other observational results in the literature, this provides further indications that stars and brown dwarfs may share a common formation mechanism, rather than being distinct populations.

  17. COULD THE PLANETS AROUND HR 8799 BE BROWN DWARFS?

    SciTech Connect

    Moro-Martin, Amaya; Rieke, George H.; Su, Kate Y. L.

    2010-10-01

    We consider the limiting case for orbital stability of the companions to HR 8799. This case is only consistent with ages for the system of {approx}100 Myr, not with the 1 Gyr age proposed from asteroseismology. The discrepancy probably arises because the inclination of the star is smaller than assumed in analyzing the asteroseismology data. Given this young age, the best estimates of the companion masses place them by a small margin on the planet side of the division between planets and brown dwarfs.

  18. The Brown Dwarf Kinematics Project (BDKP). III. Parallaxes for 70 Ultracool Dwarfs

    NASA Astrophysics Data System (ADS)

    Faherty, Jacqueline K.; Burgasser, Adam J.; Walter, Frederick M.; Van der Bliek, Nicole; Shara, Michael M.; Cruz, Kelle L.; West, Andrew A.; Vrba, Frederick J.; Anglada-Escudé, Guillem

    2012-06-01

    We report parallax measurements for 70 ultracool dwarfs (UCDs) including 11 late-M, 32 L, and 27 T dwarfs. In this sample, 14 M and L dwarfs exhibit low surface gravity features, 6 are close binary systems, and 2 are metal-poor subdwarfs. We combined our new measurements with 114 previously published UCD parallaxes and optical-mid-IR photometry to examine trends in spectral-type/absolute magnitude, and color-color diagrams. We report new polynomial relations between spectral type and MJHK . Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a "bright" (unresolved binary) and a "faint" (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0-T4 sources is prominent in MJ where there is a [1.2-1.4] mag difference. A similar yet dampened brightening of [0.3-0.5] mag happens at MH and a plateau or dimming of [-0.2 to -0.3] mag is seen in MK . Comparison with evolutionary models that vary gravity, metallicity, and cloud thickness verifies that for L into T dwarfs, decreasing cloud thickness reproduces brown dwarf near-IR color-magnitude diagrams. However we find that a near constant temperature of 1200 ±100 K along a narrow spectral subtype of T0-T4 is required to account for the brightening and color-magnitude diagram of the L-dwarf/T-dwarf transition. There is a significant population of both L and T dwarfs which are red or potentially "ultra-cloudy" compared to the models, many of which are known to be young indicating a correlation between enhanced photospheric dust and youth. For the low surface gravity or young companion L dwarfs we find that 8 out of 10 are at least [0.2-1.0] mag underluminous in MJH and/or MK compared to equivalent spectral type objects. We speculate that this is a consequence of increased dust opacity and conclude that low surface gravity L dwarfs require a completely new spectral-type/absolute magnitude polynomial for analysis.

  19. THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS

    SciTech Connect

    Faherty, Jacqueline K.; Shara, Michael M.; Cruz, Kelle L.; Burgasser, Adam J.; Walter, Frederick M.; Van der Bliek, Nicole; Vrba, Frederick J.; Anglada-Escude, Guillem

    2012-06-10

    We report parallax measurements for 70 ultracool dwarfs (UCDs) including 11 late-M, 32 L, and 27 T dwarfs. In this sample, 14 M and L dwarfs exhibit low surface gravity features, 6 are close binary systems, and 2 are metal-poor subdwarfs. We combined our new measurements with 114 previously published UCD parallaxes and optical-mid-IR photometry to examine trends in spectral-type/absolute magnitude, and color-color diagrams. We report new polynomial relations between spectral type and M{sub JHK}. Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a 'bright' (unresolved binary) and a 'faint' (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0-T4 sources is prominent in M{sub J} where there is a [1.2-1.4] mag difference. A similar yet dampened brightening of [0.3-0.5] mag happens at M{sub H} and a plateau or dimming of [-0.2 to -0.3] mag is seen in M{sub K} . Comparison with evolutionary models that vary gravity, metallicity, and cloud thickness verifies that for L into T dwarfs, decreasing cloud thickness reproduces brown dwarf near-IR color-magnitude diagrams. However we find that a near constant temperature of 1200 {+-}100 K along a narrow spectral subtype of T0-T4 is required to account for the brightening and color-magnitude diagram of the L-dwarf/T-dwarf transition. There is a significant population of both L and T dwarfs which are red or potentially 'ultra-cloudy' compared to the models, many of which are known to be young indicating a correlation between enhanced photospheric dust and youth. For the low surface gravity or young companion L dwarfs we find that 8 out of 10 are at least [0.2-1.0] mag underluminous in M{sub JH} and/or M{sub K} compared to equivalent spectral type objects. We speculate that this is a consequence of increased dust opacity and conclude that low surface gravity L dwarfs require a completely new spectral-type/absolute magnitude

  20. Brown Dwarfs: Discovery and Detailed Studies

    NASA Technical Reports Server (NTRS)

    Kulkarni, Shrinivas R.

    2001-01-01

    We obtained the optical and IR spectra of Gliese 229B and identified Cs, I, and CO features - as expected in theoretical models. Our optical IR spectrum showed that most of the refractory metals have condensed out of the atmosphere and the presence of Cs, I and CO shows evidence for disequilibrium chemistry. We reported orbital evidence for Gliese 229B. The HST measured optical magnitudes provide additional evidence for the absence of dust in the atmosphere of this cool object. The luminosity of brown dwarfs depend on their masses and ages and in order to interpret the results of the survey we have carried out an extensive Monte Carlo analysis. Our conclusion is that warm brown dwarfs are rare, as companions in the orbital period range beyond approximately 30 - 50 AU. The Palomer survey poses no constraint for brown dwarfs in planetary orbits similar to those of the outer planets. We have just started a program of imaging nearby stars with the newly commissioned AO system at Palomar and Keck and have already found a brown dwarf candidate.

  1. The Role of Microvolt T-Wave Alternans to Assess Arrhythmia Vulnerability Among Patients with Heart Failure and Systolic Dysfunction: Primary Results from the TWA SCD-HeFT Substudy

    PubMed Central

    Gold, Michael R; Ip, John H; Costantini, Otto; Poole, Jeanne E; McNulty, Steven; Mark, Daniel B; Lee, Kerry L; Bardy, Gust H

    2009-01-01

    Background Sudden cardiac death remains a leading cause of mortality despite advances in medical treatment for the prevention of ischemic heart disease and heart failure. Recent studies showed a benefit of ICD implantation, but appropriate shocks for ventricular tachyarrhythmias were only noted in a minority of patients during 4-5 years of follow-up. Accordingly, better risk stratification is needed to optimize patient selection. In this regard microvolt T-wave alternans (TWA) has emerged as a potentially useful measure of arrhythmia vulnerability, but it has not been evaluated previously in a prospective randomized trial of ICD therapy. Methods and Results This investigation was a prospective substudy of the SCD-HeFT trial including 490 patients at 37 clinical sites. TWA tests were classified by blinded readers as + (37%), - (22%), or indeterminate (41%) by standard criteria. The composite primary endpoint was the first occurrence of any of the following events: sudden cardiac death, sustained ventricular tachycardia/fibrillation or appropriate ICD discharge. During a median follow-up of 30 months, there were no significant differences in event rates between TWA + or − patients (Hazard ratio 1.24, p=0.56, [CI 0.60, 2.59]), or TWA − and non − (+ and indeterminate) subjects (Hazard ratio 1.28, p=0.46, CI [0.65, 2.53]). Similar results were obtained including or excluding patients randomized to amiodarone in the analyses. Conclusions TWA testing did not predict arrhythmic events or mortality in SCD-HeFT, although a small reduction of events (20-25%) among TWA − patients cannot be excluded given the sample size of this study. Accordingly, these results suggest that TWA is not useful to help make clinical decisions regarding ICD therapy among patients with heart failure and left ventricular systolic dysfunction. PMID:18955671

  2. Formation of high-field magnetic white dwarfs from common envelopes.

    PubMed

    Nordhaus, Jason; Wellons, Sarah; Spiegel, David S; Metzger, Brian D; Blackman, Eric G

    2011-02-22

    The origin of highly magnetized white dwarfs has remained a mystery since their initial discovery. Recent observations indicate that the formation of high-field magnetic white dwarfs is intimately related to strong binary interactions during post-main-sequence phases of stellar evolution. If a low-mass companion, such as a planet, brown dwarf, or low-mass star, is engulfed by a post-main-sequence giant, gravitational torques in the envelope of the giant lead to a reduction of the companion's orbit. Sufficiently low-mass companions in-spiral until they are shredded by the strong gravitational tides near the white dwarf core. Subsequent formation of a super-Eddington accretion disk from the disrupted companion inside a common envelope can dramatically amplify magnetic fields via a dynamo. Here, we show that these disk-generated fields are sufficiently strong to explain the observed range of magnetic field strengths for isolated, high-field magnetic white dwarfs. A higher-mass binary analogue may also contribute to the origin of magnetar fields. PMID:21300910

  3. Memory for Companions in Preschool Children.

    ERIC Educational Resources Information Center

    Delfosse, Patricia; Smith, Peter K.

    1979-01-01

    Memory of preschool children (four years of age) for companions was investigated by comparing interview data using a picture sociometric technique with observational data on actual play companions. Subjects were 15 boys and girls. (Author/MP)

  4. Hydrodynamics of winds from irradiated companion stars in low-mass X-ray binaries

    NASA Technical Reports Server (NTRS)

    Tavani, Marco; London, Richard

    1993-01-01

    We study the hydrodynamics of evaporative winds driven by X-rays and/or soft gamma-rays irradiating the outer layers of companion stars in low-mass X-ray binaries (LMXBs). We consider several irradiating fluxes and spectra for LMXBs with white dwarf and main-sequence companion stars. The thermal structure of the base of the coronal region, the position of the sonic point, and the value of the mass-loss rate are calculated in the case of spherical geometry. We consider photospheric and coronal heating from both X-ray photoionization and Compton scattering of X-rays and soft gamma-rays with energy about 1 MeV possibly irradiating the companion star in LMXBs. Evaporative winds may play a relevant role for the evolution of a special class of radiation-driven LMXBs, and this study is a step toward a quantitative understanding of the mechanism driving LMXB evolution.

  5. DISCOVERY OF THE COLDEST IMAGED COMPANION OF A SUN-LIKE STAR

    SciTech Connect

    Thalmann, C.; Carson, J.; Goto, M.; Feldt, M.; Henning, T.; Klahr, H.; Mordasini, C.; Janson, M.; McElwain, M.; Egner, S.; Hayano, Y.; Suzuki, R.; Hashimoto, J.; Kandori, R.; Kudo, T.; Kusakabe, N.; Morino, J.-I.; Suto, H.; Tamura, M.; Hodapp, K. W.

    2009-12-20

    We present the discovery of a brown dwarf or possible planet at a projected separation of 1.''9 = 29 AU around the star GJ 758, placing it between the separations at which substellar companions are expected to form by core accretion (approx5 AU) or direct gravitational collapse (typically approx>100 AU). The object was detected by direct imaging of its thermal glow with Subaru/HiCIAO. At 10-40 times the mass of Jupiter and a temperature of 550-640 K, GJ 758 B constitutes one of the few known T-type companions, and the coldest ever to be imaged in thermal light around a Sun-like star. Its orbit is likely eccentric and of a size comparable to Pluto's orbit, possibly as a result of gravitational scattering or outward migration. A candidate second companion is detected at 1.''2 at one epoch.

  6. A Companion Assessment of Equatorial Stars with both Astrometry and Radial Velocity

    NASA Astrophysics Data System (ADS)

    Davison, Cassy; White, R. J.; Henry, T. J.; Jao, W.; Bailey, J. I.; Cantrell, J. R.; Riedel, A. R.

    2013-01-01

    The aim of CAESAR, a Companion Assessment of Equatorial Stars with both Astrometry and Radial velocity, is to determine the frequency of close companions around mid M stars, all the way down to planetary masses. The ensemble sample of 61 stars includes all known mid-M dwarfs (includes M3.5V to M8V) within 10 parsecs that have declinations between +/- 30 degrees without known companions within 2"; here we show results for half of the stars in the survey. We are using CSHELL at NASA's Infaraed Telescope Falicity to obtain high precision infrared radial velocity (RV) measurements to search for planets with short periods, close-in to their parent star. Our radial velocity precision for high signal to noise targets is 50 to 80m/s. As a complement to our radial velocity program, we are using results from the RECONS astrometry program at the CTIO 0.9m to search for more massive planets and brown dwarfs at distances as large as 2 AU from the majority of our stars, which is past the snowline. Our demonstrated astrometric precision is ~ 4 milli-arcseconds per night. The combination of both methods allows us to establish the most complete assessment to date on the companion frequency around these very low mass stars. This effort is supported by the NSF through grant AST-0908402 and by the NSF Graduate Reseach Fellowhip. Observations were made possible by the SMARTS Consortium and by NASA's Infrared Telescope Facility.

  7. Low-mass companions to Bright Giants

    NASA Astrophysics Data System (ADS)

    Niedzielski, A.; Wolszczan, A.; Nowak, G.; Adamów, M.; Deka, B.; Górecka, M.; Kowalik, K.

    2014-04-01

    Asymmetric Planetary Nebulae (APN) are formed by bipolar outflows through various mechanism like fast rotation (Blackman et al. 2001), magnetic field (Regos & Tout 1995) or binarity (Harpaz & Soker 1994; Soker 1996; Livio & Soker 2002). The binary scenario seems currently to be best supported by observations as the most efficient in producing the observed APN (De Marco et al. 2004; Soker 2006). Detailed studies of disk formation in binaries leading to APN were presented for instance in Reyes-Ruiz & Lopez (1999), Blackman et al. (2001) and Nordhaus & Blackman (2006). To estimate relative efficiently of the various channels of APN production properties of the population of stars to become AGB stars have to be known. Here our RV search for planets around evolved stars the Penn State-Torun Centre for Astronomy Planet Search (PTPS), whose primary, long-term goal is to improve our understanding of the evolution of planetary systems around aging stars (Niedzielski et al. 2007; Niedzielski & Wolszczan 2008) may be of some help. 1036 stars are monitored within PTPS with the Hobby-Eberly Telescope (HET, Ramsey et al. 1998) and its High Resolution Spectrograph (HRS, Tull et al. 1998) for RV variations using the high precision iodine-cell technique since 2004. The sample is mainly composed of evolved low- and intermediate- mass single or SB1 stars: 449 giants (including 343 clump giants) and 297 subgiants but it also contains 151 slightly evolved dwarfs. All SB1 and SB2 stellar-mass binaries have been identified in the sample. Detailed spectroscopic analysis of 348 stars, mostly giants has been completed by Zieliński et al. (2012). Similar analyses for 403 giants and subgiants (Niedzielski et. al. in prep.) and 146 dwarf (Deka et al. in prep.) are in preparation. In addition to stellar atmospheric parameters the spectroscopic studies deliver masses and luminosities (through fits to evolutionary tracks) as well as ages required for further considerations on planetary

  8. The SOPHIE search for northern extrasolar planets. IX. Populating the brown dwarf desert

    NASA Astrophysics Data System (ADS)

    Wilson, P. A.; Hébrard, G.; Santos, N. C.; Sahlmann, J.; Montagnier, G.; Astudillo-Defru, N.; Boisse, I.; Bouchy, F.; Rey, J.; Arnold, L.; Bonfils, X.; Bourrier, V.; Courcol, B.; Deleuil, M.; Delfosse, X.; Díaz, , R. F.; Ehrenreich, D.; Forveille, T.; Moutou, C.; Pepe, F.; Santerne, A.; Ségransan, D.; Udry, S.

    2016-04-01

    Radial velocity planet search surveys of nearby solar-type stars have shown a strong scarcity of brown dwarf companions within ~5 AU. There is presently no comprehensive explanation for this lack of brown dwarf companions; therefore, increasing the sample of such objects is crucial to understand their formation and evolution. Based on precise radial velocities obtained using the SOPHIE spectrograph at Observatoire de Haute-Provence we characterise the orbital parameters of 15 companions to solar-type stars and constrain their true mass using astrometric data from the Hipparcos space mission. The nine companions not shown to be stellar in nature have minimum masses ranging from ~13 to 70 MJup, and are well distributed across the planet/brown dwarf mass regime, making them an important contribution to the known population of massive companions around solar-type stars. We characterise six companions as stellar in nature with masses ranging from a minimum mass of 76 ± 4 MJup to a mass of 0.35 ± 0.03 M⊙. The orbital parameters of two previously known substellar candidates are improved. Based on observations collected with the SOPHIE spectrograph on the 1.93 m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium.The radial velocity measurements are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A144

  9. The Companion's Role in the Doctor-Elderly Patient-Companion Interaction.

    ERIC Educational Resources Information Center

    Beisecker, Analee E.; Fuemmeler, Elizabeth F.

    Based on Beisecker's earlier finding that patients over age 60 brought companions to their medical appointments more often than did patients aged 25-59, a study was conducted to examine the role of the companion. Eleven of 21 patients aged 60-85 brought companions. Companions were either spouses or adult children of the patients. Within this…

  10. The Solar Neighborhood. XXXVI. The Long-term Photometric Variability of Nearby Red Dwarfs in the VRI Optical Bands

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We present an analysis of long-term photometric variability for nearby red dwarf stars at optical wavelengths. The sample consists of 264 M dwarfs south of decl. = +30 with V-K = 3.96-9.16 and MV ≈ 10-20, corresponding to spectral types M2V-M8V, most of which are within 25 pc. The stars have been observed in the VRI filters for ˜4-14 yr at the CTIO/SMARTS 0.9 m telescope. Of the 238 red dwarfs within 25 pc, we find that only ˜8% are photometrically variable by at least 20 mmag (˜2%) in the VRI bands. Only four stars have been found to vary by more than 50 mmag, including GJ 1207 at 8.6 pc, which experienced a single extraordinary flare, and GJ 2006 A, TWA 8 A, and TWA 8 B, which are all young stars beyond 25 pc linked to moving groups. We find that high variability at optical wavelengths over the long term can in fact be used to identify young stars. Overall, however, the fluxes of most red dwarfs at optical wavelengths are steady to a few percent over the long term. The low overall rate of photometric variability for red dwarfs is consistent with results found in previous work on similar stars on shorter timescales, with the body of work indicating that most red dwarfs are only mildly variable. As expected, we find that the degree of photometric variability is greater in the V band than in the R or I bands, but we do not find any obvious trends in variability over the long term with red dwarf luminosity or temperature. We highlight 17 stars that show long-term changes in brightness, sometimes because of flaring activity or spots, and sometimes because of stellar cycles similar to our Sun's solar cycle. Remarkably, two targets show brightnesses that monotonically increase (G 169-029) or decrease (WT 460AB) by several percent over a decade. We also provide long-term variability measurements for seven M dwarfs within 25 pc that host exoplanets, none of which vary by more than 20 mmag. Both as a population, and for the specific red dwarfs with exoplanets observed

  11. Metal Lines in DA White Dwarfs

    NASA Astrophysics Data System (ADS)

    Zuckerman, B.; Koester, D.; Reid, I. N.; Hünsch, M.

    2003-10-01

    transfer, perhaps in the form of a wind flowing off the red dwarf. As a by-product we find from the kinematics of GD 165 a likely age of more than 2 Gyr for its probable brown dwarf companion GD 165B. This paper is based in part on observations obtained at the Calar Alto Observatory of the Deutsch-Spanisches Astronomisches Zentrum and at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the generous financial suppport of the W. M. Keck Foundation. We have made use of the SIMBAD database at CDS.

  12. The Nature of the Flaring EUVE Companion to HD 43162

    NASA Technical Reports Server (NTRS)

    Kulkarni, Shrinivas R.

    2005-01-01

    The purpose of our program was to observe and characterize the companion to HD 43162, EUVE J0614-2354, which (serendipitously) experienced an enormous flare event during our EUVE observation of HD 43162, one of the nearby solar analogs that we observed during our survey of this population. Our observation was carried out and the data have been received and reduced. We are able to identify EUVE J0614-2354 in both the X-ray (EPIC MOS + PN) and the UV (OM) data, which provides a sub-arcsecond position for this source. Our findings are consistent with the analysis of Christian et al. (2003a,b), who identify EUVE J0614-2354 with a coronally-active M-dwarf star at distance d = 15 plus or minus 5pc. The X-ray spectrum from the EPIC data are also consistent with this identification.

  13. The Gobbling Dwarf that Exploded

    NASA Astrophysics Data System (ADS)

    2007-07-01

    A unique set of observations, obtained with ESO's VLT, has allowed astronomers to find direct evidence for the material that surrounded a star before it exploded as a Type Ia supernova. This strongly supports the scenario in which the explosion occurred in a system where a white dwarf is fed by a red giant. ESO PR Photo 31a/07 ESO PR Photo 31a/07 Evolution of SN 2006X Spectrum Because Type Ia supernovae are extremely luminous and quite similar to one another, these exploding events have been used extensively as cosmological reference beacons to trace the expansion of the Universe. However, despite significant recent progress, the nature of the stars that explode and the physics that governs these powerful explosions have remained very poorly understood. In the most widely accepted models of Type Ia supernovae the pre-explosion white dwarf star orbits another star. Due to the close interaction and the strong attraction produced by the very compact object, the companion star continuously loses mass, 'feeding' the white dwarf. When the mass of the white dwarf exceeds a critical value, it explodes. The team of astronomers studied in great detail SN 2006X, a Type Ia supernova that exploded 70 million light-years away from us, in the splendid spiral Galaxy Messier 100 (see ESO 08/06). Their observations led them to discover the signatures of matter lost by the normal star, some of which is transferred to the white dwarf. The observations were made with the Ultraviolet and Visual Echelle Spectrograph (UVES), mounted at ESO's 8.2-m Very Large Telescope, on four different occasions, over a time span of four months. A fifth observation at a different time was secured with the Keck telescope in Hawaii. The astronomers also made use of radio data obtained with NRAO's Very Large Array as well as images extracted from the NASA/ESA Hubble Space Telescope archive. ESO PR Photo 31b/07 ESO PR Photo 31b/07 SN 2006X, before and after the Type Ia Supernova explosion "No Type Ia

  14. Searching for Binary Y Dwarfs with the Gemini Multi-conjugate Adaptive Optics System (GeMS)

    NASA Astrophysics Data System (ADS)

    Opitz, Daniela; Tinney, C. G.; Faherty, Jacqueline K.; Sweet, Sarah; Gelino, Christopher R.; Kirkpatrick, J. Davy

    2016-03-01

    The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to have smaller separations and are more frequently detected in near-equal mass configurations. The binary statistics for Y-type brown dwarfs, however, are sparse, and so it is unclear if the same trends that hold for L- and T-type brown dwarfs also hold for Y-type ones. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results for binary properties of a sample of five WISE Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System. We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or equal-mass) binaries with separations larger than ˜0.5-1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e., 1042 erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs.

  15. THE ELM SURVEY. V. MERGING MASSIVE WHITE DWARF BINARIES

    SciTech Connect

    Brown, Warren R.; Kenyon, Scott J.; Kilic, Mukremin; Gianninas, A.; Allende Prieto, Carlos E-mail: skenyon@cfa.harvard.edu E-mail: alexg@nhn.ou.edu

    2013-05-20

    We present the discovery of 17 low-mass white dwarfs (WDs) in short-period (P {<=} 1 day) binaries. Our sample includes four objects with remarkable log g {approx_equal} 5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or ongoing accretion. Notably, six of the WDs in our sample have binary merger times <10 Gyr. Four have {approx}>0.9 M{sub Sun} companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be millisecond pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the ELM Survey to 54; 31 of these binaries will merge within a Hubble time.

  16. Infrared Spectral Energy Distributions of Nearby Dwarf Carbon Stars

    NASA Astrophysics Data System (ADS)

    Lowrance, Patrick

    2014-06-01

    The discovery of G77-61 (Dahn et al. 1977) -- a star with a carbon-rich spectrum a mere 58 pc away and therefore of relatively low luminosity -- led to the recognition that _dwarf_ carbon (dC) stars exist. As more dCs are now known, the accepted paradigm of the presence of atmospheric carbon is that dCs must contain a white dwarf secondary. While the white dwarf companion was going through an AGB stage, it deposited carbon-rich material in the atmosphere of the lower-mass (and now brighter) dwarf star. Indeed, a handful of the dC's have exhibited radial velocity signatures consistent with this picture. To allow for the carbon to still be present in the atmosphere past the AGB stage, a replenishing outer shell or disk has been proposed. Current understanding of the formation and evolution of a dC is, however, limited by the small number of objects and observations. We present a full range of fluxes and flux limits from 1 - 160 um including 2MASS, WISE, Spitzer, and Herschel observations for a list of the nearest carbon dwarfs. We reconstruct the spectral energy distribution exploring the mid-infrared region where any residual debris disks would be detectable. The carbon dwarfs have been historically studied in the visible, and these new infrared observations provide a picture of the circumstellar dust.

  17. Observational Constraints on the White Dwarf Mass--Radius Relation

    NASA Astrophysics Data System (ADS)

    Oswalt, Terry D.; Dhital, Saurav; Mizusawa, Trisha; Holberg, Jay B.; Zhao, Jingkun

    2014-02-01

    We propose to measure gravitational redshifts for white dwarf stars that have distant, non-interacting main-sequence companions. With independent radius constraints obtained from parallaxes and surface gravity determinations obtained by fitting the Balmer series from our spectra, we will make improved estimates of white dwarf masses and radii that can be critically compared with theoretical mass-radius relations specific to each star. These observations will allow us to examine serious discrepancies between the theoretical and empirical measurements of the white dwarf mass-radius relation and extend the range of masses over which it has been tested, spanning 0.5-1.2 Msun. Currently, the measured radius for only a single WD matches its predicted value. Using the same spectra, we will also estimate the metallicity of the main-sequence companion and examine how the initial-final-mass ratio for WDs depends on metallicity. Thus, this project will put robust constraints on two fundamental relations that govern our understanding of white dwarfs: the mass-ratio and the initial-final-mass relations.

  18. The closest M-dwarf quadruple system to the Sun

    SciTech Connect

    Davison, Cassy L.; White, R. J.; Jao, W.-C.; Henry, T. J.; Quinn, S. N.; Cantrell, J. R.; Winters, J. G.; Bailey, J. I. III; Riedel, A. R.; Subasavage, J. P.; Crockett, C. J.

    2014-02-01

    We report new infrared radial velocity measurements obtained with CSHELL at NASA's Infrared Telescope Facility that reveal the M3.5 dwarf GJ 867B to be a single-lined spectroscopic binary with a period of 1.795 ± 0.017 days. Its velocity semi-amplitude of 21.4 ± 0.5 km s{sup –1} corresponds to a minimum mass of 61 ± 7 M {sub JUP}; the new companion, which we call GJ 867D, could be a brown dwarf. Stable astrometric measurements of GJ 867BD obtained with CTIO's 0.9 m telescope over the last decade exclude the presence of any massive planetary companions (7-18 M {sub JUP}) with longer orbital periods (2-10 yr) for the majority of orientations. These complementary observations are also used to determine the trigonometric distance and proper motion of GJ 867BD; the measurements are consistent with the HIPPARCOS measured values of the M2 dwarf GJ 867AC, which is itself a 4.1 day double-lined spectroscopic binary at a projected separation of 24.''5 (216 AU) from GJ 867BD. These new measurements strengthen the case that GJ 867AC and GJ 867BD are physically associated, making the GJ 867 system one of only four quadruple systems within 10 pc of the Sun (d = 8.82 ± 0.08 pc) and the only among these with all M-dwarf (or cooler) components.

  19. THE ABSENCE OF EX-COMPANIONS IN TYPE Ia SUPERNOVA REMNANTS

    SciTech Connect

    Di Stefano, R.; Kilic, Mukremin E-mail: kilic@ou.edu

    2012-11-01

    Type Ia supernovae (SNe Ia) play important roles in our study of the expansion and acceleration of the universe, but because we do not know the exact nature or natures of the progenitors, there is a systematic uncertainty that must be resolved if SNe Ia are to become more precise cosmic probes. No progenitor system has ever been identified either in the pre- or post-explosion images of a Ia event. There have been recent claims for and against the detection of ex-companion stars in several SNe Ia remnants. These studies, however, usually ignore the angular momentum gain of the progenitor white dwarf (WD), which leads to a spin-up phase and a subsequent spin-down phase before explosion. For spin-down timescales greater than 10{sup 5} years, the donor star could be too dim to detect by the time of explosion. Here we revisit the current limits on ex-companion stars to SNR 0509-67.5, a 400-year-old remnant in the Large Magellanic Cloud. If the effects of possible angular momentum gain on the WD are included, a wide range of single-degenerate progenitor models are allowed for this remnant. We demonstrate that the current absence of evidence for ex-companion stars in this remnant, as well as other SNe Ia remnants, does not necessarily provide the evidence of absence for ex-companions. We discuss potential ways to identify such ex-companion stars through deep imaging observations.

  20. AN ALMA DISK MASS FOR THE CANDIDATE PROTOPLANETARY COMPANION TO FW TAU

    SciTech Connect

    Kraus, Adam L.; Andrews, Sean M.; Bowler, Brendan P.; Herczeg, Gregory; Ireland, Michael J.; Liu, Michael C.; Metchev, Stanimir; Cruz, Kelle L.

    2015-01-01

    We present ALMA observations of the FW Tau system, a close binary pair of M5 stars with a wide-orbit (300 AU projected separation) substellar companion. The companion is extremely faint and red in the optical and near-infrared, but boasts a weak far-infrared excess and optical/near-infrared emission lines indicative of a primordial accretion disk of gas and dust. The component-resolved 1.3 mm continuum emission is found to be associated only with the companion, with a flux (1.78 ± 0.03 mJy) that indicates a dust mass of 1-2 M {sub ⊕}. While this mass reservoir is insufficient to form a giant planet, it is more than sufficient to produce an analog of the Kepler-42 exoplanetary system or the Galilean satellites. The mass and geometry of the disk-bearing FW Tau companion remains unclear. Near-infrared spectroscopy shows deep water bands that indicate a spectral type later than M5, but substantial veiling prevents a more accurate determination of the effective temperature (and hence mass). Both a disk-bearing ''planetary-mass'' companion seen in direct light or a brown dwarf tertiary viewed in light scattered by an edge-on disk or envelope remain possibilities.

  1. Detection of a white dwarf in a visual binary system

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1992-01-01

    The F6 giant HD 160365 was detected to have a white dwarf companion about 8 arcsec south of the star. The UV energy distribution observed with IUE shows that the white dwarf has an effective temperature of 23,000 +/- 2000 K. If log g = 8 the Lya profile indicates an effective temperature around 24,500 K. Using the theoretical models by Wesemael et al. (1980) one finds a visual magnitude of m(V) about 16.5. For T(eff) = 24,500 K one expects for a white dwarf a luminosity of log L/L(solar) about 1.3 and M(V) about 10.67. This gives a distance modulus for the system of m(V) - M(V) = 5.83 and an absolute magnitude M(V)= 0.3 for the giant.

  2. Detection of a white dwarf in a visual binary system

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1980-01-01

    The F6 giant HD 160365 was detected to have a white dwarf companion about 8 arcsec south of the star. The UV energy distribution observed with International Ultraviolet Explorer (IUE) shows that the white dwarf has an effective temperature of 23,000 +/- 2,000 K. If log g = 8 the Ly(alpha) profile indicates an effective temperature around 24,500 K. Using the theoretical models, one finds a visual magnitude of m(sub v) is approximately 16.5. For T(sub eff) = 24,500 K one expects for a white dwarf a luminosity of log L/solar luminosity is approximately -1.3 and M(sub V) is approximately 10.67. This gives a distance modulus for the system of m(sub v) - M(sub V) = 5.83 and an absolute magnitude M(sub v) = 0.3 for the giant.

  3. Cloud Driven Variability on Young Brown Dwarfs and Giant Exoplanets

    NASA Astrophysics Data System (ADS)

    Biller, Beth

    2016-01-01

    Variability has now been robustly observed in a range of L and T type field brown dwarfs, primarily at near-IR and mid-IR wavelengths. The probable cause of this variability is surface inhomogeneities in the clouds of these objects, causing a semi-periodic variability signal when combined with the rotational modulation from the 3-12 hour period expected for these objects. Variability at similar or even higher amplitudes may be expected for young brown dwarfs and giant exoplanets, which share similar Teff as field brown dwarfs, but have considerably lower surface gravities. Variability studies of these objects relative to old field objects is then a direct probe of the effects of surface gravity on atmospheric structure. Here I discuss ongoing efforts to detect variability from these young objects, both for free-floating objects and companions to stars, including preliminary results from an ongoing survey of young, low surface gravity objects with NTT SOFI.

  4. Mystery of a Dimming White Dwarf

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-12-01

    In the wake of the recent media attention over an enigmatic, dimming star, another intriguing object has been discovered: J1529+2928, a white dwarf that periodically dims. This mystery, however, may have a simple solution with interesting consequences for future surveys of white dwarfs.Unexpected VariabilityJ1529+2928 is an isolated white dwarf that appears to have a mass of slightly more than the Sun. But rather than radiating steadily, J1529+2928 dims once every 38 minutes almost as though it were being eclipsed.The team that discovered these variations, led by Mukremin Kilic (University of Oklahoma), used telescopes at the Apache Point Observatory and the McDonald Observatory to obtain follow-up photometric data of J1529+2928 spread across 66 days. The team also took spectra of the white dwarf with the Gemini North telescope.Kilic and collaborators then began, one by one, to rule out possible causes of this objects variability.Eliminating OptionsThe period of the variability is too long for J1529+2928 to be a pulsating white dwarf with luminosity variation caused by gravity-wave pulsations.The variability cant be due to an eclipse by a stellar or brown-dwarf companion, because there isnt any variation in J1529+2928s radial velocity.Its not due to the orbit of a solid-body planetary object; such a transit would be too short to explain observations.It cant be due to the orbit of a disintegrated planet; this wouldnt explain the light curves observed in different filters plus the light curve doesnt change over the 66-day span.Spotty SurfaceTop and middle two panels: light curves from three different nights observing J1529+2928s periodic dimming. Bottom panel: The Fourier transform shows a peak at 37.7 cycles/day (and another, smaller peak at its first harmonic). [Kilic et al. 2015]So what explanation is left? The authors suggest that J1529+2928s variability is likely caused by a starspot on the white dwarfs surface that rotates into and out of our view. Estimates

  5. THE KEPLER LIGHT CURVE OF THE UNIQUE DA WHITE DWARF BOKS 53856

    SciTech Connect

    Holberg, J. B.; Howell, Steve B. E-mail: howell@noao.edu

    2011-08-15

    The faint (g = 16.9) hot white dwarf BOKS 53856 was observed by the Kepler Mission in short cadence mode during mid-2009. Analysis of these observations reveals a highly stable modulation with a period of 6.1375 hr and a 2.46% half-amplitude. The folded light curve has an unusual shape that is difficult to explain in terms of a binary system containing an unseen companion more luminous than an L0 brown dwarf. Optical spectra of BOKS 53856 show a T{sub eff} = 34,000 K, log g = 8.0 DA white dwarf. There are few, if any, known white dwarfs in this temperature range exhibiting photometric variations similar to those we describe. A magnetic spin-modulated white dwarf model can in principle explain the light curve, an interpretation supported by spectral observations of the H{alpha} line showing evidence of Zeeman splitting.

  6. THE EXEMPLAR T8 SUBDWARF COMPANION OF WOLF 1130

    SciTech Connect

    Mace, Gregory N.; McLean, Ian S.; Logsdon, Sarah E.; Wright, Edward L.; Kulas, Kristin R.; Kirkpatrick, J. Davy; Gelino, Christopher R.; Beichman, Charles A.; Cushing, Michael C.; Skrutskie, Michael F.; Eisenhardt, Peter R.

    2013-11-01

    We have discovered a wide separation (188.''5) T8 subdwarf companion to the sdM1.5+WD binary Wolf 1130. Companionship of WISE J200520.38+542433.9 is verified through common proper motion over a ∼3 yr baseline. Wolf 1130 is located 15.83 ± 0.96 pc from the Sun, placing the brown dwarf at a projected separation of ∼3000 AU. Near-infrared colors and medium resolution (R ≈ 2000-4000) spectroscopy establish the uniqueness of this system as a high-gravity, low-metallicity benchmark. Although there are a number of low-metallicity T dwarfs in the literature, WISE J200520.38+542433.9 has the most extreme inferred metallicity to date with [Fe/H] = –0.64 ± 0.17 based on Wolf 1130. Model comparisons to this exemplar late-type subdwarf support it having an old age, a low metallicity, and a small radius. However, the spectroscopic peculiarities of WISE J200520.38+542433.9 underscore the importance of developing the low-metallicity parameter space of the most current atmospheric models.

  7. Evidence for very nearby hidden white dwarfs

    NASA Astrophysics Data System (ADS)

    Fuhrmann, K.; Chini, R.; Kaderhandt, L.; Chen, Z.; Lachaume, R.

    2016-06-01

    We report the discovery of a tertiary component to the prominent and nearby (d = 14 pc) visual binary α Fornacis. The new invisible component is part of a 4-d short-period Ba-Bb subsystem, whose K-type α For Ba primary shows a striking [Ba/Fe] = +0.26 dex overabundance, at variance with a close to solar [Ba/Fe] = +0.04 dex abundance for its distant visual companion α For A. For the even nearer (d = 8 pc) multiple star ξ Ursae Majoris and its alike 4-d Ba-Bb subsystem, we similarly find [Ba/Fe] = +0.37 dex for its G-type ξ UMa Ba primary, compared to a significantly lower [Ba/Fe] = +0.12 dex for the visual companion ξ UMa A. In both cases, the differential barium enrichment is direct evidence for short-period white dwarf systems and the creation of blue straggler stars through mass transfer and wind accretion, for their close and distant companions, respectively. These findings also imply that conventional stellar age datings for both α For and ξ UMa are likely not reliable.

  8. Dynamical analyses of the companions orbiting eclipsing binaries - I. SW Lacertae

    NASA Astrophysics Data System (ADS)

    Yuan, Jinzhao; Şenavci, Hakan Volkan

    2014-03-01

    New mid-eclipse times of the short-period eclipsing binary SW Lacertae are reported, and two cyclical variations are found in the corresponding O - C diagram. The proposed light-travel time model is refined. The best fit suggests that two possible circumbinary companions are in a near 3:1 mean-motion resonance with periods of 27.01 and 82.61 yr. Based on the best-fitting solution, we have studied the stabilities of the two companions moving on a series of mutually inclined orbits. The results show that no orbital configurations can survive for >1000 yr. Then, non-Keplerian corrections to the initial conditions and the more distant K-dwarf companion discovered by Ruciński, Pribulla & van Kerkwijk, moving on assumed circular orbits with wide ranges of orbital inclinations, are considered in our numerical simulations. The outcome similarly reveals that the whole system is yet short-term unstable. Perhaps, one or both cyclical variations in the mid-eclipse times are attributed to irregular mass exchange and/or magnetic cycles in the magnetically active W UMa system. Despite this, the instability of the system may also arise from the large uncertainties in orbital parameters. So, secular observations of this target are needed to determine the eccentricity of the outmost companion and the orbital period of the middle companion with much higher precision. Our results suggest that, if the two inner companions do exist, they should be on mutually inclined orbits of >100°, with the minimum masses of 0.62 and 1.94 M⊙ for the innermost and middle components, respectively. Our work demonstrates that it is important and necessary to perform dynamical analyses before a discovery of two or more circumbinary companions is announced.

  9. The search for substellar companions to subdwarf B stars in connection with evolutionary aspects

    NASA Astrophysics Data System (ADS)

    Lutz, Ronny

    2011-09-01

    The formation and evolution of single hot subdwarf B stars is not entirely understood. Enhanced mass loss during the red giant phase is a prerequisite to explain the very existence of these stars, yet its cause is a matter of debate. One hypothesis predicts that substellar companions like brown dwarfs and exoplanets may be able to have a decisive influence on the formation and evolution of single subdwarf B stars. This dissertation investigates two pulsating subdwarf B stars with the goal to search for substellar companions and to directly measure the evolutionary timescales. The long-term multi-site photometric data were taken in the framework of the EXOTIME (EXOplanet search with the TIming MEthod) program and cover a baseline of several tens of months. The secular behaviour of several pulsations in each target is investigated by applying a timing method and constructing O-C (Observed minus Calculated) diagrams. The analysis results in the fundamental insight that both targets are in a phase of global expansion, that their pulsation periods increase on a timescale of several million years and that the two target stars have probably already undergone core Helium exhaustion. Furthermore, the O-C diagrams show evidence for the presence of substellar companions. The star HS0444+0458 has a brown dwarf companion candidate of roughly 31 Jupiter masses in an orbit of 0.27 astronomical units. An exoplanet candidate of 5.6 Jupiter masses is found to orbit its host star HS0702+6043 at a distance of 1.15 astronomical units. These detections provide a direct support for a formation channel of single subdwarf B stars that includes substellar companions as the mass loss trigger.

  10. Know the Star, Know the Planet. IV. A Stellar Companion to the Host Star of the Eccentric Exoplanet HD 8673b

    NASA Astrophysics Data System (ADS)

    Roberts, Lewis C., Jr.; Mason, Brian D.; Neyman, Christopher R.; Wu, Yanqin; Riddle, Reed L.; Shelton, J. Christopher; Angione, John; Baranec, Christoph; Bouchez, Antonin; Bui, Khanh; Burruss, Rick; Burse, Mahesh; Chordia, Pravin; Croner, Ernest; Das, Hillol; Dekany, Richard G.; Guiwits, Stephen; Hale, David; Henning, John; Kulkarni, Shrinivas; Law, Nicholas; McKenna, Dan; Milburn, Jennifer; Palmer, Dean; Punnadi, Sujit; Ramaprakash, A. N.; Roberts, Jennifer E.; Tendulkar, Shriharsh P.; Trinh, Thang; Troy, Mitchell; Truong, Tuan; Zolkower, Jeff

    2015-04-01

    HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e = 0.723). Based on two epochs of speckle interferometry a previous publication identified a candidate stellar companion. We observed HD 8673 multiple times with the 10 m Keck II telescope, the 5 m Hale telescope, the 3.63 m Advanced Electro-Optical System telescope, and the 1.5 m Palomar telescope in a variety of filters with the aim of confirming and characterizing the stellar companion. We did not detect the candidate companion, which we now conclude was a false detection, but we did detect a fainter companion. We collected astrometry and photometry of the companion on six epochs in a variety of filters. The measured differential photometry enabled us to determine that the companion is an early M dwarf with a mass estimate of 0.33-0.45 M⊙ . The companion has a projected separation of 10 AU, which is one of the smallest projected separations of an exoplanet host binary system. Based on the limited astrometry collected, we are able to constrain the orbit of the stellar companion to a semimajor axis of 35-60 AU, an eccentricity ≤slant 0.5, and an inclination of 75°-85°. The stellar companion has likely strongly influenced the orbit of the exoplanet and quite possibly explains its high eccentricity.

  11. Wind-driven evolution of white dwarf binaries to type Ia supernovae

    SciTech Connect

    Ablimit, Iminhaji; Xu, Xiao-jie; Li, X.-D.

    2014-01-01

    In the single-degenerate scenario for the progenitors of Type Ia supernovae (SNe Ia), a white dwarf rapidly accretes hydrogen- or helium-rich material from its companion star and appears as a supersoft X-ray source. This picture has been challenged by the properties of the supersoft X-ray sources with very low mass companions and the observations of several nearby SNe Ia. It has been pointed out that the X-ray radiation or the wind from the accreting white dwarf can excite winds or strip mass from the companion star, thus significantly influencing the mass transfer processes. In this paper, we perform detailed calculations of the wind-driven evolution of white dwarf binaries. We present the parameter space for the possible SN Ia progenitors and for the surviving companions after the SNe. The results show that the ex-companion stars of SNe Ia have characteristics more compatible with the observations, compared with those in the traditional single-degenerate scenario.

  12. Formation of high-field magnetic white dwarfs from common envelopes

    PubMed Central

    Nordhaus, Jason; Wellons, Sarah; Spiegel, David S.; Metzger, Brian D.; Blackman, Eric G.

    2011-01-01

    The origin of highly magnetized white dwarfs has remained a mystery since their initial discovery. Recent observations indicate that the formation of high-field magnetic white dwarfs is intimately related to strong binary interactions during post-main-sequence phases of stellar evolution. If a low-mass companion, such as a planet, brown dwarf, or low-mass star, is engulfed by a post-main-sequence giant, gravitational torques in the envelope of the giant lead to a reduction of the companion’s orbit. Sufficiently low-mass companions in-spiral until they are shredded by the strong gravitational tides near the white dwarf core. Subsequent formation of a super-Eddington accretion disk from the disrupted companion inside a common envelope can dramatically amplify magnetic fields via a dynamo. Here, we show that these disk-generated fields are sufficiently strong to explain the observed range of magnetic field strengths for isolated, high-field magnetic white dwarfs. A higher-mass binary analogue may also contribute to the origin of magnetar fields. PMID:21300910

  13. A Dark Spot on a Massive White Dwarf

    NASA Astrophysics Data System (ADS)

    Kilic, Mukremin; Gianninas, Alexandros; Bell, Keaton J.; Curd, Brandon; Brown, Warren R.; Hermes, J. J.; Dufour, Patrick; Wisniewski, John P.; Winget, D. E.; Winget, K. I.

    2015-12-01

    We present the serendipitous discovery of eclipse-like events around the massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We selected J1529+2928 for time-series photometry based on its spectroscopic temperature and surface gravity, which place it near the ZZ Ceti instability strip. Instead of pulsations, we detect photometric dips from this white dwarf every 38 minutes. Follow-up optical spectroscopy observations with Gemini reveal no significant radial velocity variations, ruling out stellar and brown dwarf companions. A disintegrating planet around this white dwarf cannot explain the observed light curves in different filters. Given the short period, the source of the photometric dips must be a dark spot that comes into view every 38 minutes due to the rotation of the white dwarf. Our optical spectroscopy does not show any evidence of Zeeman splitting of the Balmer lines, limiting the magnetic field strength to B < 70 kG. Since up to 15% of white dwarfs display kG magnetic fields, such eclipse-like events should be common around white dwarfs. We discuss the potential implications of this discovery on transient surveys targeting white dwarfs, like the K2 mission and the Large Synoptic Survey Telescope. This work is based on observations obtained at the Gemini Observatory, McDonald Observatory, and the Apache Point Observatory 3.5-m telescope. The latter is owned and operated by the Astrophysical Research Consortium. Gemini Observatory 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), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  14. Measuring the spin of the directly imaged sub-stellar companion GQ Lupi b

    NASA Astrophysics Data System (ADS)

    Schwarz, Henriette; Brogi, Matteo; de Kok, Remco; Birkby, Jayne; Snellen, Ignas

    2015-12-01

    Recently we measured for the first time the spin rotation of an extra-solar planet. The famous planet beta Pictoris b was found to spin much faster than any planet in our solar system, which is in line with the idea that massive planets spin more rapidly. Interestingly, field brown dwarfs do not seem to follow this relation, which may indicate that an object's spin is closely linked to its formation mechanism.Here we present the spin measurement of the sub-stellar companion GQ Lupi b, which has an uncertain mass in the range separating extrasolar planets and brown dwarfs. The young T-Tauri system was observed for an hour with the CRIRES instrument at the VLT with a spectral resolving power of 100000, positioning the slit to both contain the host star and the companion separated from the host by 0.7 arcseconds. We find GQ Lupi b to be a slow rotator with a projected rotational velocity of 6.0 pm 0.8 km/s, possibly due to the ultra-young companion still being in the process of accreting material and angular momentum.

  15. Multiplicity of the Galactic Senior Citizens: A High-resolution Search for Cool Subdwarf Companions

    NASA Astrophysics Data System (ADS)

    Ziegler, Carl; Law, Nicholas M.; Baranec, Christoph; Riddle, Reed L.; Fuchs, Joshua T.

    2015-05-01

    Cool subdwarfs are the oldest members of the low-mass stellar population. Mostly present in the galactic halo, subdwarfs are characterized by their low-metallicity. Measuring their binary fraction and comparing it to solar-metallicity stars could give key insights into the star formation process early in the Milky Way’s history. However, because of their low luminosity and relative rarity in the solar neighborhood, binarity surveys of cool subdwarfs have suffered from small sample sizes and incompleteness. Previous surveys have suggested that the binary fraction of red subdwarfs is much lower than for their main-sequence cousins. Using the highly efficient Robo-AO system, we present the largest high-resolution survey of subdwarfs, sensitive to angular separations (ρ ≥slant 0.″ 15) and contrast ratios ({Δ }{{m}i} ≤slant 6) invisible in past surveys. Of 344 target cool subdwarfs, 43 are in multiple systems, 19 of which are newly discovered, for a binary fraction of 12.5 ± 1.9%. We also discovered seven triple star systems for a triplet fraction of 2.0 ± 0.8%. Comparisons to similar surveys of solar-metallicity dwarf stars gives a ∼3σ disparity in luminosity between companion stars, with subdwarfs displaying a shortage of low-contrast companions. We also observe a lack of close subdwarf companions in comparison to similar-mass dwarf multiple systems.

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

    NASA Astrophysics Data System (ADS)

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

    2008-05-01

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

  17. WISE and Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, J. Davy; WISE Team

    2009-05-01

    The search for the nearest and coolest brown dwarfs will use WISE's two short-wavelength channels (W1 and W2), which are optimized for brown dwarf detection. W1 samples the methane fundamental absorption band at 3.3 microns, and W2 measures the relatively opacity-free portion of the brown dwarf atmosphere near 4.7 microns. Cool brown dwarfs will thus have very red [W1]-[W2] colors, maximizing our chances of identifying them. Extrapolating preferred mass functions to very low masses and assuming that the star formation rate has been constant over the last 10 Gyr, we can predict the number of brown dwarfs WISE is expected to image. At spectral types later than T7 (Teff > 850K), WISE is expected to find 500 brown dwarfs, which makes WISE uniquely suited among future surveys to measure the low-mass limit of star formation for the first time. This sample will also show whether a new spectral class beyond T, dubbed "Y", is needed at the lowest temperatures. Although the primary six-month WISE mission will cover the entire sky once, WISE should have sufficient cryogen to perform a second, complete pass of the sky. In this case, the identification of nearby brown dwarfs need not rely solely on color selection. Kinematics (proper motion) and geometry (parallax) can also be used to distinguish our closest brown dwarf neighbors, one of which may lie less distant than Proxima Centauri or even fall within our own Oort Cloud.

  18. Astrophysics: Illuminating brown dwarfs

    NASA Astrophysics Data System (ADS)

    Showman, Adam P.

    2016-05-01

    Objects known as brown dwarfs are midway between stars and planets in mass. Observations of a hot brown dwarf irradiated by a nearby star will help to fill a gap in our knowledge of the atmospheres of fluid planetary objects. See Letter p.366

  19. A search for a distant companion to the sun with the wide-field infrared survey explorer

    SciTech Connect

    Luhman, K. L.

    2014-01-20

    I have used multi-epoch astrometry from the Wide-field Infrared Survey Explorer to perform a search for a distant companion to the Sun via its parallactic motion. I have not found an object of this kind down to W2 = 14.5. This limit corresponds to analogs of Saturn and Jupiter at 28,000 and 82,000 AU, respectively, according to models of the Jovian planets by Fortney and coworkers. Models of brown dwarfs by Burrows and coworkers predict fainter fluxes at a given mass for the age of the solar system, producing a closer distance limit of 26,000 AU for a Jupiter-mass brown dwarf. These constraints exclude most combinations of mass and separation at which a solar companion has been suggested to exist by various studies over the years.

  20. THE IMPACT OF TYPE Ia SUPERNOVA EXPLOSIONS ON HELIUM COMPANIONS IN THE CHANDRASEKHAR-MASS EXPLOSION SCENARIO

    SciTech Connect

    Liu Zhengwei; Wang, B.; Han, Z. W.; Pakmor, R.; Seitenzahl, I. R.; Hillebrandt, W.; Kromer, M.; Edelmann, P.; Taubenberger, S.; Roepke, F. K.; Maeda, K.

    2013-09-01

    In the version of the single-degenerate scenario of Type Ia supernovae (SNe Ia) studied here, a carbon-oxygen white dwarf explodes close to the Chandrasekhar limit after accreting material from a non-degenerate helium (He) companion star. In the present study, we employ the STELLAR GADGET code to perform three-dimensional hydrodynamical simulations of the interaction of the SN Ia ejecta with the He companion star taking into account its orbital motion and spin. It is found that only 2%-5% of the initial companion mass is stripped off from the outer layers of He companion stars due to the supernova (SN) impact. The dependence of the unbound mass (or the kick velocity) on the orbital separation can be fitted to a good approximation by a power law for a given companion model. After the SN impact, the outer layers of a He donor star are significantly enriched with heavy elements from the low-expansion-velocity tail of SN Ia ejecta. The total mass of accumulated SN-ejecta material on the companion surface reaches about {approx}> 10{sup -3} M{sub Sun} for different companion models. This enrichment with heavy elements provides a potential way to observationally identify the surviving companion star in SN remnants. Finally, by artificially adjusting the explosion energy of the W7 explosion model, we find that the total accumulation of SN ejecta on the companion surface is also dependent on the explosion energy with a power-law relation to a good approximation.

  1. Mapping the Shores of the Brown Dwarf Desert. IV. Ophiuchus

    NASA Astrophysics Data System (ADS)

    Cheetham, Anthony C.; Kraus, Adam L.; Ireland, Michael J.; Cieza, Lucas; Rizzuto, Aaron C.; Tuthill, Peter G.

    2015-11-01

    We conduct a multiplicity survey of members of the ρ Ophiuchus cloud complex with high-resolution imaging to characterize the multiple-star population of this nearby star-forming region and investigate the relation between stellar multiplicity and star and planet formation. Our aperture masking survey reveals the presence of five new stellar companions beyond the reach of previous studies, but does not result in the detection of any new substellar companions. We find that 43 ± 6% of the 114 stars in our survey have stellar-mass companions between 1.3 and 780 AU, while {7}-5+8% host brown dwarf companions in the same interval. By combining this information with knowledge of disk-hosting stars, we show that the presence of a close binary companion (separation <40 AU) significantly influences the lifetime of protoplanetary disks, a phenomenon previously seen in older star-forming regions. At the ˜1-2 Myr age of our Ophiuchus members ˜2/3 of close binary systems have lost their disks, compared to only ˜30% of single stars and wide binaries. This has a significant impact on the formation of giant planets, which are expected to require much longer than 1 Myr to form via core accretion and thus planets formed via this pathway should be rare in close binary systems.

  2. Blue compact dwarfs - Extreme dwarf irregular galaxies

    NASA Technical Reports Server (NTRS)

    Thuan, Trinh X.

    1987-01-01

    Observational data on the most extreme members of the irregular dwarf (dI) galaxy class, the blue compact dwarfs (BCDs), are characterized, reviewing the results of recent investigations. The properties of the young stellar population, the ionized gas, the older star population, and the gas and dust of BCDs are contrasted with those of other dIs; BCD morphology is illustrated with sample images; and the value of BCDs (as nearby 'young' chemically unevolved galaxies) for studies of galaxy formation, galactic evolution, and starburst triggering mechanisms is indicated.

  3. First supernova companion star found

    NASA Astrophysics Data System (ADS)

    2004-01-01

    Supernova 1993J exploding hi-res Size hi-res: 222 kb Credits: ESA and Justyn R. Maund (University of Cambridge) Supernova 1993J exploding (artist’s impression) New observations with the Hubble Space Telescope allow a look into a supernova explosion under development. In this artist’s view the red supergiant supernova progenitor star (left) is exploding after having transferred about 10 solar masses of hydrogen gas to the blue companion star (right). This interaction process happened over about 250 years and affected the supernova explosion to such an extent that SN 1993J was later known as one of the most peculiar supernovae ever seen. Supernova 1993J exploding hi-res Size hi-res: 4200 kb Credits: ESA and Justyn R. Maund (University of Cambridge) The site of the Supernova 1993J explosion A virtual journey into one of the spiral arms of the grand spiral Messier 81 (imaged with the Isaac Newton Telescope on La Palma, left) reveals the superb razor-sharp imaging power of the NASA/ESA Hubble Space Telescope (Hubble’s WFPC2 instrument, below). The close-up (with Hubble’s ACS, to the right) is centred on the newly discovered companion star to Supernova 1993J that itself is no longer visible. The quarter-circle around the supernova companion is a so-called light echo originating from sheets of dust in the galaxy reflecting light from the original supernova explosion. Supernova 1993J explosing site hi-res Size hi-res: 1502 kb Credits: ESA and Justyn R. Maund (University of Cambridge) Close-up of the Supernova 1993J explosion site (ACS/HRC image) This NASA/ESA Hubble Space Telescope image shows the area in Messier 81 where Supernova 1993J exploded. The companion to the supernova ‘mother star’ that remains after the explosion is seen in the centre of the image. The image is taken with Hubble’s Advanced Camera for Surveys and is a combination of four exposures taken with ACS’ High Resolution Camera. The exposures were taken through two near-UV filters (250W

  4. BINARY FORMATION MECHANISMS: CONSTRAINTS FROM THE COMPANION MASS RATIO DISTRIBUTION

    SciTech Connect

    Reggiani, Maddalena M.; Meyer, Michael R.

    2011-09-01

    We present a statistical comparison of the mass ratio distribution of companions, as observed in different multiplicity surveys, to the most recent estimate of the single-object mass function. The main goal of our analysis is to test whether or not the observed companion mass ratio distribution (CMRD) as a function of primary star mass and star formation environment is consistent with having been drawn from the field star initial mass function (IMF). We consider samples of companions for M dwarfs, solar-type stars, and intermediate-mass stars, both in the field as well as clusters or associations, and compare them with populations of binaries generated by random pairing from the assumed IMF for a fixed primary mass. With regard to the field we can reject the hypothesis that the CMRD was drawn from the IMF for different primary mass ranges: the observed CMRDs show a larger number of equal-mass systems than predicted by the IMF. This is in agreement with fragmentation theories of binary formation. For the open clusters {alpha} Persei and the Pleiades we also reject the IMF random-pairing hypothesis. Concerning young star-forming regions, currently we can rule out a connection between the CMRD and the field IMF in Taurus but not in Chamaeleon I. Larger and different samples are needed to better constrain the result as a function of the environment. We also consider other companion mass functions and we compare them with observations. Moreover the CMRD both in the field and clusters or associations appears to be independent of separation in the range covered by the observations. Combining therefore the CMRDs of M (1-2400 AU) and G (28-1590 AU) primaries in the field and intermediate-mass primary binaries in Sco OB2 (29-1612 AU) for mass ratios, q = M{sub 2}/M{sub 1}, from 0.2 to 1, we find that the best chi-square fit follows a power law dN/dq{proportional_to}q {sup {beta}}, with {beta} = -0.50 {+-} 0.29, consistent with previous results. Finally, we note that the

  5. Binary Formation Mechanisms: Constraints from the Companion Mass Ratio Distribution

    NASA Astrophysics Data System (ADS)

    Reggiani, Maddalena M.; Meyer, Michael R.

    2011-09-01

    We present a statistical comparison of the mass ratio distribution of companions, as observed in different multiplicity surveys, to the most recent estimate of the single-object mass function. The main goal of our analysis is to test whether or not the observed companion mass ratio distribution (CMRD) as a function of primary star mass and star formation environment is consistent with having been drawn from the field star initial mass function (IMF). We consider samples of companions for M dwarfs, solar-type stars, and intermediate-mass stars, both in the field as well as clusters or associations, and compare them with populations of binaries generated by random pairing from the assumed IMF for a fixed primary mass. With regard to the field we can reject the hypothesis that the CMRD was drawn from the IMF for different primary mass ranges: the observed CMRDs show a larger number of equal-mass systems than predicted by the IMF. This is in agreement with fragmentation theories of binary formation. For the open clusters α Persei and the Pleiades we also reject the IMF random-pairing hypothesis. Concerning young star-forming regions, currently we can rule out a connection between the CMRD and the field IMF in Taurus but not in Chamaeleon I. Larger and different samples are needed to better constrain the result as a function of the environment. We also consider other companion mass functions and we compare them with observations. Moreover the CMRD both in the field and clusters or associations appears to be independent of separation in the range covered by the observations. Combining therefore the CMRDs of M (1-2400 AU) and G (28-1590 AU) primaries in the field and intermediate-mass primary binaries in Sco OB2 (29-1612 AU) for mass ratios, q = M 2/M 1, from 0.2 to 1, we find that the best chi-square fit follows a power law dN/dqvpropq β, with β = -0.50 ± 0.29, consistent with previous results. Finally, we note that the Kolmogorov-Smirnov test gives a ~1% probability

  6. Suites of dwarfs around Nearby giant galaxies

    SciTech Connect

    Karachentsev, Igor D.; Kaisina, Elena I.; Makarov, Dmitry I. E-mail: kei@sao.ru

    2014-01-01

    The Updated Nearby Galaxy Catalog (UNGC) contains the most comprehensive summary of distances, radial velocities, and luminosities for 800 galaxies located within 11 Mpc from us. The high density of observables in the UNGC makes this sample indispensable for checking results of N-body simulations of cosmic structures on a ∼1 Mpc scale. The environment of each galaxy in the UNGC was characterized by a tidal index Θ{sub 1}, depending on the separation and mass of the galaxy's main disturber (MD). We grouped UNGC galaxies with a common MD in suites, and ranked suite members according to their Θ{sub 1}. All suite members with positive Θ{sub 1} are assumed to be physical companions of the MD. About 58% of the sample are members of physical groups. The distribution of suites by the number of members, n, follows a relation N(n) ∼ n {sup –2}. The 20 most populated suites contain 468 galaxies, i.e., 59% of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at M{sub B} = –18{sup m}. We discuss various properties of MDs, as well as galaxies belonging to their suites. The suite abundance practically does not depend on the morphological type, linear diameter, or hydrogen mass of the MD, the tightest correlation being with the MD dynamical mass. Dwarf galaxies around MDs exhibit well-known segregation effects: the population of the outskirts has later morphological types, richer H I contents, and higher rates of star formation activity. Nevertheless, there are some intriguing cases where dwarf spheroidal galaxies occur at the far periphery of the suites, as well as some late-type dwarfs residing close to MDs. Comparing simulation results with galaxy groups, most studies assume the Local Group is fairly typical. However, we recognize that the nearby groups significantly differ from each other and there is considerable variation in their properties. The suites of companions around the Milky Way and M31, consisting of the

  7. Suites of Dwarfs around nearby Giant Galaxies

    NASA Astrophysics Data System (ADS)

    Karachentsev, Igor D.; Kaisina, Elena I.; Makarov, Dmitry I.

    2014-01-01

    The Updated Nearby Galaxy Catalog (UNGC) contains the most comprehensive summary of distances, radial velocities, and luminosities for 800 galaxies located within 11 Mpc from us. The high density of observables in the UNGC makes this sample indispensable for checking results of N-body simulations of cosmic structures on a ~1 Mpc scale. The environment of each galaxy in the UNGC was characterized by a tidal index Θ1, depending on the separation and mass of the galaxy's main disturber (MD). We grouped UNGC galaxies with a common MD in suites, and ranked suite members according to their Θ1. All suite members with positive Θ1 are assumed to be physical companions of the MD. About 58% of the sample are members of physical groups. The distribution of suites by the number of members, n, follows a relation N(n) ~ n -2. The 20 most populated suites contain 468 galaxies, i.e., 59% of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at MB = -18m. We discuss various properties of MDs, as well as galaxies belonging to their suites. The suite abundance practically does not depend on the morphological type, linear diameter, or hydrogen mass of the MD, the tightest correlation being with the MD dynamical mass. Dwarf galaxies around MDs exhibit well-known segregation effects: the population of the outskirts has later morphological types, richer H I contents, and higher rates of star formation activity. Nevertheless, there are some intriguing cases where dwarf spheroidal galaxies occur at the far periphery of the suites, as well as some late-type dwarfs residing close to MDs. Comparing simulation results with galaxy groups, most studies assume the Local Group is fairly typical. However, we recognize that the nearby groups significantly differ from each other and there is considerable variation in their properties. The suites of companions around the Milky Way and M31, consisting of the Local Group, do not quite seem to be a typical

  8. Efficient detection of brown dwarfs using methane-band imaging

    NASA Astrophysics Data System (ADS)

    Rosenthal, Edward D.; Gurwell, Mark A.; Ho, Paul T. P.

    1996-11-01

    BROWN dwarfs lie in the mass range between the most massive Jupiter-like planets and the least massive stars. They are much less luminous than stars, and so may provide a fraction of the baryonic dark matter in our Galaxy. Only one unambiguous detection of a brown dwarf has been made to date1-6-G1229B, a low-mass companion to the nearby star G1229A. The detection4 of strong methane-band absorption in the spectrum of G1229B, a feature restricted to cool substellar objects5-9, lends weight to the idea7 that differential methane-band imaging (the subtraction of an image taken in the methane band from a continuum-light image taken in the same spectral region) should provide an efficient method for detecting brown dwarfs. Here we demonstrate the potential of this approach by obtaining an image of G1229B with less than two minutes of integration time. This technique promises efficient detection of both isolated brown dwarfs in crowded regions, and brown dwarfs orbiting close to their primary stars.

  9. A non-uniform distribution of the nearest brown dwarfs

    NASA Astrophysics Data System (ADS)

    Bihain, G.; Scholz, R.-D.

    2016-05-01

    Context. The census of solar neighbours is still complemented by new discoveries, mainly of very low-mass, faint dwarfs, close to or within the substellar domain. These discoveries contribute to a better understanding of the field population; its origin in terms of Galactic dynamics and (sub)stellar formation and evolution. Also, the nearest stars and brown dwarfs at any given age allow the most precise direct characterization, including the search for planetary companions. Aims: We aim to further assess the substellar census on the Galactic plane. Methods: We projected the 136 stars and 26 brown dwarfs known at <6.5 pc on the Galactic plane and evaluated their distributions. Results: Stars present a uniform- and brown dwarfs a non-uniform distribution, with 21 objects behind the Sun and only five ahead relative to the direction of rotation of the Galaxy. This substellar configuration has a probability of 0.098+10.878-0.098% relative to uniformity. The helio- and geocentric nature of the distribution suggests it might result in part from an observational bias, which if compensated for by future discoveries, might increase the brown-dwarf-to-star ratio, shifting it closer to values found in some star forming regions.

  10. NICMOS Imaging of 2MASSWJ 1207334-393254 - A Planetary-Mass Companion Candidate

    NASA Astrophysics Data System (ADS)

    Schneider, G.; Song, I.; Zuckerman, B.; Becklin, E.; Lowrance, P.; Macintosh, B.; Bessell, M.; Dumas, C.; Chauvin, G.

    2004-12-01

    2MASSWJ 1207334-393254, a likely member of the nearby TW Hya association (age app 10 Myr and app 70 pc from Earth), is an app 30 Mjupiter brown dwarf (M8V spectrum due to its youth) for which a putative candidate planetary-mass companion was identified by Chauvin et al (Astron. and Astroph. 425, L29) with VLT/NACO observations in April 2004. Earlier, 2MASSWJ 1207334-393254 had been scheduled for observation in HST cycle 13 in a NICMOS H-band coronagraphic companion detection survey (GO 10176), but was re-programmed as an early "follow-up" observation given the ground-based derived implications for shorter wavelength space-based detection and efficacious diagnostic photometric measurements. Here, we present NICMOS camera 1 imaging photometry observations of 2MASSWJ 1207334-393254 and its point-like companion candidate in three bands: F090M (0.80 - 1.00 microns; similar to I-band), F110M (1.00 - 1.20 microns) and F160W (1.40 - 1.60 microns; similar to H-band) obtained on 28 Aug 2004. For the 773.7 +/- 2.2 mas (app 55 AU projected separation) distant companion we find in-band magnitudes for the companion candidate of F090M = 22.34 +/- 0.35 (delta-F090M = +7.14), F110M = 20.61 +/- 0.15 and (delta-F110M = +7.02) F160W = 18.24 +/- 0.02 (delta-F160W = +5.62). The NICMOS [0.90] - [1.6] micron color index of +4.1 +/- 0.4 is consistent with expectations for the spectral energy distribution of a mid to late L-dwarf (e.g., I - H of app +4.4 for spectral type L4). At the likely age of this candidate, the NICMOS and longer wavelength VLT/NACO derived photometric measures may implicate an object of several Jupiter masses. If the candidate companion is (as is yet to be) demonstrated to exhibit common proper motion with 2MASSWJ 1207334-393254 then the first image of a gravitationally bound companion of planetary mass may have already been secured. This work is supported through grants to the GO 10176 and 10177 teams from STScI, which is operated by AURA, Inc., under NASA contract

  11. A Radial Velocity Survey of Hot Subdwarfs with Main Sequence Companions using the Hobby-Eberly Telescope

    NASA Astrophysics Data System (ADS)

    Wade, R.; Barlow, B.; Liss, S.; Stark, M.

    2014-04-01

    Binary population synthesis models are generally successful at reproducing the observed periods of hot subdwarf binaries with M dwarf or white dwarf companions; the story for sdB+F/G/K binaries, however, is still being written. Relatively few observational constraints have been published for these composite-spectra systems. We have been monitoring the radial velocities (RVs) of 15 hot subdwarf binaries with late F - K dwarf companions since 2005 using the Medium and High Resolution Spectrographs on the Hobby-Eberly Telescope. Here we present RV measurements and orbital parameter estimates for selected systems in our sample. We also present an up-to-date period histogram for all known hot subdwarf binaries, including both short- and long-period systems. Our initial results suggest that those with late F - K main sequence companions have orbital periods on the order of 1.5 to 3 years. Several of the long-period binaries show strong evidence for non-circular orbits, challenging the conventional Roche Lobe overflow formation channel for hot subdwarfs.

  12. M dwarfs: Theoretical work

    NASA Technical Reports Server (NTRS)

    Mullan, Dermott J.

    1987-01-01

    Theoretical work on the atmospheres of M dwarfs has progressed along lines parallel to those followed in the study of other classes of stars. Such models have become increasingly sophisticated as improvements in opacities, in the equation of state, and in the treatment of convection were incorporated during the last 15 to 20 years. As a result, spectrophotometric data on M dwarfs can now be fitted rather well by current models. The various attempts at modeling M dwarf photospheres in purely thermal terms are summarized. Some extensions of these models to include the effects of microturbulence and magnetic inhomogeneities are presented.

  13. When White Dwarfs Collide

    NASA Astrophysics Data System (ADS)

    Hawley, Wendy Phyllis

    2012-01-01

    3D models of white dwarf collisions are used to assess the likelihood of double-degenerate mergers as progenitors for Type Ia supernovae (henceforth SNIa) and to identify observational signatures of double-degenerate collisions. Observations of individual SNIa, SNIa rates in different galaxy types, and double white dwarf binary systems suggest that mergers or collisions between two white dwarfs play a role in the overall SNIa population. Given the possibility of two progenitor systems (single-degenerate and double-degenerate), the sample of SNIa used in cosmological calcula- tions needs to be carefully examined. To improve calculations of cosmological parameters, the development of calibrated diagnostics for double-degenerate progenitor SNIa is essential. Head-on white dwarf collision simulations are used to provide an upper limit on the 56Ni production in white dwarf collisions. In chapter II, I explore zero impact parameter collisions of white dwarfs using the Eulerian grid code FLASH. The initial 1D white dwarf profiles are created assuming hydrostatic equilibrium and a uniform composition of 50% 12C and 50% 16O. The masses range from 0.64 to 0.81 solar masses and have an isothermal temperature of 107 K. I map these 1D models onto a 3D grid, where the dimensions of the grid are each eight times the white dwarf radius, and the dwarfs are initially placed four white dwarf radii apart (center to center). To provide insight into a larger range of physical possibilities, I also model non-zero impact parameter white dwarf collisions (Chapter III). Although head-on white dwarf collisions provide an upper limit on 56Ni production, non-zero impact parameter collisions provide insight into a wider range of physical scenarios. The initial conditions (box size, initial separation, composition, and initial temperature) are identical to those used for the head-on collisions (Chapter II) for the same range of masses. For each mass pair- ing, collision simulations are carried

  14. White-dwarf + main-sequence binaries identified from the ninth data release of the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Li, Lifang; Zhang, Fenghui; Han, Quanwang; Kong, Xiaoyang; Gong, Xiaobo

    2014-12-01

    We have identified 227 new spectroscopic white-dwarf + main-sequence (WDMS) binaries from the ninth data release (DR9) of the Sloan Digital Sky Survey (SDSS). The SDSS spectra of the newly found WDMS binaries with a DA white dwarf and an M-dwarf are analysed based on a spectral decomposition/fitting method. We obtain the effective temperatures, surface gravities and masses of the white dwarf, together with the spectral types and metallicities of the secondary star. Two independent distance estimates are derived from the flux-scaling factors between the WDMS SDSS spectra and the white dwarf and M-dwarf model spectra. We find that about 25 per cent of the newly found WDMS binaries show a significant discrepancy between the two distance estimates. This might be caused by the effects of M-dwarf stellar activity or irradiation of the M-dwarf companions by the white dwarf. The stellar parameter distributions are used to investigate the global properties of the newly found WDMS binaries. We find that the WDMS binaries with a low signal-to-noise ratio (S/N ≤ 4.0) usually have a massive DA white dwarf component with a higher surface gravity, and the metallicity is usually significantly different from solar. This suggests that the observational selection effects and the spectral S/N of the WDMS binaries have a significant influence on the determinations of these physical parameters of WDMS binaries.

  15. A NEW SUB-STELLAR COMPANION AROUND THE YOUNG STAR HD 284149

    SciTech Connect

    Bonavita, Mariangela; Desidera, Silvano; Daemgen, Sebastian; Jayawardhana, Ray; Janson, Markus; Lafrenière, David

    2014-08-20

    Even though only a handful of sub-stellar companions have been found via direct imaging, each of these discoveries has had a tremendous impact on our understanding of the star formation process and the physics of cool atmospheres. Young stars are prime targets for direct imaging searches for planets and brown dwarfs due to the favorable brightness contrast expected at such ages and also because it is often possible to derive relatively good age estimates for these primaries. Here we present the direct imaging discovery of HD 284149 b, a 18-50 M {sub Jup} companion at a projected separation of 400 AU from a young (25{sub 10}{sup +25} Myr) F8 star, with which it shares common proper motion.

  16. Hubble Space Telescope observations of the very low mass companion to Gliese 105A

    NASA Technical Reports Server (NTRS)

    Golimowski, David A.; Fastie, William G.; Uomoto, Alan; Schroeder, Daniel J.

    1995-01-01

    Hubble Space Telescope images of the astrometric binary GI 105A confirm the previous ground-based detection of a faint, very red companion (GI 105C) located 3.39 sec from GI 105A at P.A. 290 deg. The instrumental magnitudes of GI 105C are (visual magnitude) V(sub 555) = 16.86 and I(sub 814) = 13.54. The observed position of GI 105C differs significantly from the positions expected from current astrometric solutions. No other companions brighter than I(sub 814) = 20.3 are seen between 1 sec and 13.5 sec from GI 105A. Using the M dwarf model atmospheres of Allard and Hauschildt, we obtain for GI 105C a standard color of V - I = 4.6, which suggests a spectral type of M7 V.

  17. THE (DOUBLE) WHITE DWARF BINARY SDSS 1257+5428

    SciTech Connect

    Kulkarni, S. R.; Van Kerkwijk, M. H.

    2010-08-20

    SDSS 1257+5428 is a white dwarf in a close orbit with a companion that has been suggested to be a neutron star. If so, it hosts the closest known neutron star, and its existence implies a great abundance of similar systems and a rate of white dwarf neutron-star mergers similar to that of the type Ia supernova rate. Here, we present high signal-to-noise spectra of SDSS 1257+5428, which confirm an independent finding that the system is in fact composed of two white dwarfs, one relatively cool and with low mass and the other hotter and more massive. With this, the demographics and merger rate are no longer puzzling (various factors combine to lower the latter by more than 2 orders of magnitude). We show that the spectra are fit well with a combination of two hydrogen model atmospheres, as long as the lines of the higher-gravity component are broadened significantly relative to what is expected from just pressure broadening. Interpreting this additional broadening as due to rotation, the inferred spin period is short, about 1 minute. Similarly rapid rotation is only seen in accreting white dwarfs that are magnetic; empirically, it appears that in non-magnetized white dwarfs, accreted angular momentum is lost by nova explosions before it can be transferred to the white dwarf. This suggests that the massive white dwarf in SDSS 1257+5428 is magnetic as well, with B {approx_equal} 10{sup 5} G. Alternatively, the broadening seen in the spectral lines could be due to a stronger magnetic field, of {approx}10{sup 6} G. The two models can be distinguished by further observations.

  18. THE INITIAL-FINAL MASS RELATION AMONG WHITE DWARFS IN WIDE BINARIES

    SciTech Connect

    Zhao, J. K.; Oswalt, T. D.; Willson, L. A.; Wang, Q.; Zhao, G. E-mail: toswalt@fit.edu E-mail: lwillson@iastate.edu

    2012-02-20

    We present the initial-final mass relation derived from 10 white dwarfs in wide binaries that consist of a main-sequence star and a white dwarf. The temperature and gravity of each white dwarf were measured by fitting theoretical model atmospheres to the observed spectrum using a {chi}{sup 2} fitting algorithm. The cooling time and mass were obtained using theoretical cooling tracks. The total age of each binary was estimated from the chromospheric activity of its main-sequence component to an uncertainty of about 0.17 dex in log t. The difference between the total age and white dwarf cooling time is taken as the main-sequence lifetime of each white dwarf. The initial mass of each white dwarf was then determined using stellar evolution tracks with a corresponding metallicity derived from spectra of their main-sequence companions, thus yielding the initial-final mass relation. Most of the initial masses of the white dwarf components are between 1 and 2 M{sub Sun }. Our results suggest a correlation between the metallicity of a white dwarf's progenitor and the amount of post-main-sequence mass loss it experiences-at least among progenitors with masses in the range of 1-2 M{sub Sun }. A comparison of our observations to theoretical models suggests that low-mass stars preferentially lose mass on the red giant branch.

  19. THE BINARY COMPANION OF YOUNG, RELATIVISTIC PULSAR J1906+0746

    SciTech Connect

    Van Leeuwen, J.; Janssen, G. H.; Kasian, L.; Stairs, I. H.; Lorimer, D. R.; Camilo, F.; Chatterjee, S.; Cognard, I.; Desvignes, G.; Freire, P. C. C.; Kramer, M.; Lyne, A. G.; Stappers, B. W.; Nice, D. J.; Ransom, S. M.; Weisberg, J. M.

    2015-01-10

    PSR J1906+0746 is a young pulsar in the relativistic binary with the second-shortest known orbital period, of 3.98 hr. We here present a timing study based on five years of observations, conducted with the five largest radio telescopes in the world, aimed at determining the companion nature. Through the measurement of three post-Keplerian orbital parameters, we find the pulsar mass to be 1.291(11) M {sub ☉}, and the companion mass 1.322(11) M {sub ☉}, respectively. These masses fit well in the observed collection of double neutron stars (DNSs), but are also compatible with other systems where a young pulsar such as J1906+0746 is orbited by a white dwarf (WD). Neither radio pulsations nor dispersion-inducing outflows that could have further established the companion nature were detected. We derive an H I-absorption distance, which indicates that an optical confirmation of a WD companion is very challenging. The pulsar is fading fast due to geodetic precession, limiting future timing improvements. We conclude that the young pulsar J1906+0746 is likely part of a DNS, or is otherwise orbited by an older WD, in an exotic system formed through two stages of mass transfer.

  20. Ground Based Astrometric Search for Substellar Companions in Stellar Multiple Systems, The Case of the Exoplanet Host System HD 19994

    NASA Astrophysics Data System (ADS)

    Röll, T.; Seifahrt, A.; Neuhäuser, R.; Köhler, R.

    2010-12-01

    Due to the unknown inclination angle, radial velocity (RV) measurements only provide the minimum mass of companions. In combination with transit observations one can derive the true mass, but a transit is only observable for nearly edge-on systems. For all other systems, astrometry is the only method to get the true mass of an orbiting companion by measuring the reflex motion of the host star. In our ongoing astrometric search program we observe stellar multiple systems within a distance of 100 parsec in order to confirm RV exoplanet candidates and to search for unknown substellar companions. Here we present preliminary results of one of our targets, the binary HD 19994, which is known to harbour a RV planet candidate around the A component. From our astrometric observations over the last years, it seems that a high mass brown dwarf is orbiting the low-mass B component. Analysis of our data with speckle interferometry confirms the existence of an additional body.

  1. A search for faint companions of the nearest stars with CanariCam and VHS .

    NASA Astrophysics Data System (ADS)

    Gauza, B.; Béjar, V. J. S.; Rebolo, R.; érez-Garrido, A. P.; Lodieu, N.; Álvarez, C.; UCD Group of the VHS; substellar Group of the CCST

    After two decades of discoveries, the census of substellar objects in the solar neighborhood remains incomplete. Current imaging surveys carried out in the near and mid-infrared are expected to unveil numerous ultracool dwarfs and expand the population to previously undetectable temperature ranges. Here we present a review of our searches for substellar companions around stars in the solar vicinity (d<10 pc). The searches are based on the southern near-infrared VISTA Hemisphere Survey (VHS) combined with WISE and 2MASS catalogues and on a deep mid-IR imaging program carried out with CanariCam at the 10.4m GTC, in the Northern sky. We achieve sensitivity and resolving power that enables us to detect early Y dwarfs (T_eff˜300-500 K) at separations larger than 10 AU.

  2. A tidally distorted dwarf galaxy near NGC 4449.

    PubMed

    Rich, R M; Collins, M L M; Black, C M; Longstaff, F A; Koch, A; Benson, A; Reitzel, D B

    2012-02-01

    NGC 4449 is a nearby Magellanic irregular starburst galaxy with a B-band absolute magnitude of -18 and a prominent, massive, intermediate-age nucleus at a distance from Earth of 3.8 megaparsecs (ref. 3). It is wreathed in an extraordinary neutral hydrogen (H I) complex, which includes rings, shells and a counter-rotating core, spanning ∼90 kiloparsecs (kpc; refs 1, 4). NGC 4449 is relatively isolated, although an interaction with its nearest known companion--the galaxy DDO 125, some 40 kpc to the south--has been proposed as being responsible for the complexity of its H I structure. Here we report the presence of a dwarf galaxy companion to NGC 4449, namely NGC 4449B. This companion has a V-band absolute magnitude of -13.4 and a half-light radius of 2.7 kpc, with a full extent of around 8 kpc. It is in a transient stage of tidal disruption, similar to that of the Sagittarius dwarf near the Milky Way. NGC 4449B exhibits a striking S-shaped morphology that has been predicted for disrupting galaxies but has hitherto been seen only in a dissolving globular cluster. We also detect an additional arc or disk ripple embedded in a two-component stellar halo, including a component extending twice as far as previously known, to about 20 kpc from the galaxy's centre. PMID:22318602

  3. [Companion Diagnostics for Solid Tumors].

    PubMed

    Watanabe, Atsushi

    2015-11-01

    Companion diagnostics (CoDx) will likely continue to rapidly increase in number and application to disease areas including solid tumors, for example EGFR for gefitinib and ALK fusion gene for crizotinib in non-small-cell lung cancer; KRAS against the use of cetuximab and panitumumab in colorectal cancer; HER2 for trastuzumab in breast cancer. CoDx are an indispensable part of personalized medicine and pharmacogenomics. In CoDx development, there are still many challenges, such as the business model promoting cooperation between diagnostics and pharmaceutical companies, and also the regulations related to CoDx. The FDA notice on the development of CoDx in 2011 recommended the co-development of a new drug and CoDx as the best practice, and the Ministry of Health, Labour and Welfare in Japan also issued a statement in 2013. In addition, the recent discovery of many novel variants in the DNA sequence, advances in sequencing and genomic technology, and improved analytic methods have enabled the impact of germline and somatic mutations to be determined using multiplex diagnosis. The complex challenges to develop CoDx necessitate a close collaboration among academic institutions, regulatory authorities, and pharmaceutical companies. [Review]. PMID:26995877

  4. Companion Diagnostics and Molecular Imaging.

    PubMed

    Puranik, Ameya D; Kulkarni, Harshad R; Baum, Richard P

    2015-01-01

    Companion diagnostics (CDx) is a positive attempt in the direction of improving the drug development process, especially in the field of oncology, with the advent of newer targeted therapies. It helps the oncologist in deciding the choice of treatment for the individual patient. The role of CDx assays has attracted the attention of regulators, and especially the US Food and Drug Administration developed regulatory strategies for CDx and the drug-diagnostic codevelopment project. For an increasing number of cancer patients, the treatment selection will depend on the result generated by a CDx assay, and consequently this type of assay has become critical for the care and safety of the patients. In addition to the assay-based approach, molecular imaging with its ability to image at the genetic and receptor level has made foray into the field of drug development and personalized medicine. We shall review these aspects of CDx, with special focus on molecular imaging and the upcoming concept of Theranostics. PMID:26049701

  5. Direct Imaging of Faint Companions

    NASA Astrophysics Data System (ADS)

    Claudi, Riccardo

    The exoplanets around stars in the solar neighborhood are expected to be bright enough for us to characterize them with direct imaging; however, they are much fainter than their parent stars, and separated by very small angles, so conventional imaging techniques are totally inadequate, and new methods are needed. The direct imaging of exoplanets is extremely challenging. Jupiter is 109 times fainter than our Sun in reflected visible light. A direct imaging instrument for exoplanets must suppress (1) the bright star image and diffraction pattern and (2) the stellar scattered light from imperfections in the telescope. The main goal of high-contrast imaging is primarily to discover and characterize extrasolar planetary systems. High-contrast observations, in optical and infrared astronomy, are defined as any observation requiring a technique to reveal a low mass companion that is so close to the primary, brighter by a factor of at least 105, that optical effects hinder or prevent the collection of photons directly from the target of observation. To overcome this, astronomers combined large telescopes (to reduce the impact of diffraction), adaptive optics (to correct for phase errors induced by atmospheric turbulence), and sophisticated image processing.

  6. OGLE-2014-BLG-0257L: A Microlensing Brown Dwarf Orbiting a Low-mass M Dwarf

    NASA Astrophysics Data System (ADS)

    Han, C.; Jung, Y. K.; Udalski, A.; Gould, A.; Bozza, V.; Szymański, M. K.; Soszyński, I.; Poleski, R.; Kozłowski, S.; Pietrukowicz, P.; Skowron, J.; Ulaczyk, K.; Wyrzykowski, Ł.; OGLE Collaboration

    2016-05-01

    In this paper, we report the discovery of a binary composed of a brown dwarf (BD) and a low-mass M dwarf from observation of the microlensing event OGLE-2014-BLG-0257. The resolution of the very brief caustic crossing combined with the detection of subtle continuous deviation in the lensing light curve induced by the Earth’s orbital motion enable us to precisely measure both the Einstein radius {θ }{{E}} and the lens parallax {π }{{E}}, which are the two quantities needed to unambiguously determine the mass and distance to the lens. It is found that the companion is a substellar BD with a mass of 0.036+/- 0.005 {M}ȯ (37.7+/- 5.2 {M}{{J}}) and it is orbiting an M dwarf with a mass of 0.19+/- 0.02 {M}ȯ . The binary is located at a distance of 1.25 ± 0.13 kpc toward the Galactic bulge and the projected separation between the binary components is 0.61 ± 0.07 au. The separation scaled by the mass of the host is 3.2 {{au}}/{M}ȯ . Based on the assumption that separations scale with masses, the discovered BD is located in the BD desert. With the growing sample of BDs in various environments, microlensing will provide a powerful probe of BDs in the Galaxy.

  7. Progress of the Living with a Red Dwarf Program: Activity-Rotation-Age Relationships for M dwarfs and the Ages of Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Engle, Scott G.; Guinan, Edward Francis; Harper, Graham

    2015-08-01

    Red Dwarfs (M dwarfs or dM stars) make up over 75% of the local stellar population. This is among the reasons they are being targeted by an increasing number of planet-hunting programs. As such, developing a method to accurately estimate the age of a field M dwarf is of critical importance. However, due to their long lifetimes and very slow nuclear evolution, the best method for determining ages is likely through “magnetic tracers” such as X-UV activity levels and stellar rotation rates. The Living with a Red Dwarf program’s database of M dwarfs with photometrically determined rotation periods (via starspot modulations) is becoming substantial. Its expansion to include M dwarfs with well-detached WD companions - through which reliable ages can be determined - has had significant impacts on the reliability of the relations. When combined with M dwarfs possessing cluster/population memberships, or specific kinematics, a full range of “calibrators” is being realized. We report on our continuing efforts to build reliable Activity-Rotation-Age relationships for M dwarfs, utilizing X-UV measures obtained with HST, IUE Chandra and XMM (both proposed by us, and archival). Such relationships permit the assessment of the habitability of planets hosted by red dwarfs, by delineating the X-UV radiation environments these planets are exposed to, and have been exposed to in the past. After proper calibration, the relationships can also permit the age of a field red dwarf (and any hosted planets) to be determined through measures of either the stellar rotation period or X-UV activity level.We gratefully acknowledge the support from NSF/RUI Grant AST 1009903, Chandra Grant GO-13200633, HST Grants GO-12124X and GO-13020X.

  8. An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5.

    PubMed

    Schaefer, Bradley E; Pagnotta, Ashley

    2012-01-12

    A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a 'double-degenerate' origin), or by mass transfer from a companion star (the 'single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400 ± 50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of M(V) = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been 'kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system. PMID:22237107

  9. An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5

    NASA Astrophysics Data System (ADS)

    Schaefer, Bradley E.; Pagnotta, Ashley

    2012-01-01

    A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a `double-degenerate' origin), or by mass transfer from a companion star (the `single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400 +/- 50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of MV = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been `kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.

  10. Cepheid Companions and the Masses of Cepheids

    NASA Astrophysics Data System (ADS)

    Bohm-Vitense, E.; Borutzki, S.; Harris, H.

    The authors have observed in the ultraviolet the hot companions of the Cepheids SV Per, RW Cam, SY Nor and KN Cen. The study of the absolute and relative intensities reveals that all, except the companion for KN Cen are evolved stars which should fit on almost the same mass track as the Cepheid. The authors find however that with generally accepted reddening values the companions of at least SV Per and RW Cam are too faint. Either the Cepheid loops are more luminous than presently calculated or the reddening is larger than presently accepted.

  11. Dwarfs in ancient Egypt.

    PubMed

    Kozma, Chahira

    2006-02-15

    Ancient Egypt was one of the most advanced and productive civilizations in antiquity, spanning 3000 years before the "Christian" era. Ancient Egyptians built colossal temples and magnificent tombs to honor their gods and religious leaders. Their hieroglyphic language, system of organization, and recording of events give contemporary researchers insights into their daily activities. Based on the record left by their art, the ancient Egyptians documented the presence of dwarfs in almost every facet of life. Due to the hot dry climate and natural and artificial mummification, Egypt is a major source of information on achondroplasia in the old world. The remains of dwarfs are abundant and include complete and partial skeletons. Dwarfs were employed as personal attendants, animal tenders, jewelers, and entertainers. Several high-ranking dwarfs especially from the Old Kingdom (2700-2190 BCE) achieved important status and had lavish burial places close to the pyramids. Their costly tombs in the royal cemeteries and the inscriptions on their statutes indicate their high-ranking position in Egyptian society and their close relation to the king. Some of them were Seneb, Pereniankh, Khnumhotpe, and Djeder. There were at least two dwarf gods, Ptah and Bes. The god Ptah was associated with regeneration and rejuvenation. The god Bes was a protector of sexuality, childbirth, women, and children. He was a favored deity particularly during the Greco-Roman period. His temple was recently excavated in the Baharia oasis in the middle of Egypt. The burial sites and artistic sources provide glimpses of the positions of dwarfs in daily life in ancient Egypt. Dwarfs were accepted in ancient Egypt; their recorded daily activities suggest assimilation into daily life, and their disorder was not shown as a physical handicap. Wisdom writings and moral teachings in ancient Egypt commanded respect for dwarfs and other individuals with disabilities. PMID:16380966

  12. Isolated elliptical galaxies and their globular cluster systems. II. NGC 7796 - globular clusters, dynamics, companion

    NASA Astrophysics Data System (ADS)

    Richtler, T.; Salinas, R.; Lane, R. R.; Hilker, M.; Schirmer, M.

    2015-02-01

    Context. Rich globular cluster systems, particularly the metal-poor part of them, are thought to be the visible manifestations of long-term accretion processes. The invisible part is the dark matter halo, which may show some correspondence to the globular cluster system. It is therefore interesting to investigate the globular cluster systems of isolated elliptical galaxies, which supposedly have not experienced extended accretion. Aims: We investigate the globular cluster system of the isolated elliptical NGC 7796, present new photometry of the galaxy, and use published kinematical data to constrain the dark matter content. Methods: Deep images in B and R, obtained with the VIsible MultiObject Spectrograph (VIMOS) at the VLT, form the data base. We performed photometry with DAOPHOT and constructed a spherical photometric model. We present isotropic and anisotropic Jeans-models and give a morphological description of the companion dwarf galaxy. Results: The globular cluster system has about 2000 members, so it is not as rich as those of giant ellipticals in galaxy clusters with a comparable stellar mass, but richer than many cluster systems of other isolated ellipticals. The colour distribution of globular clusters is bimodal, which does not necessarily mean a metallicity bimodality. The kinematic literature data are somewhat inconclusive. The velocity dispersion in the inner parts can be reproduced without dark matter under isotropy. Radially anisotropic models need a low stellar mass-to-light ratio, which would contrast with the old age of the galaxy. A MONDian model is supported by X-ray analysis and previous dynamical modelling, but better data are necessary for a confirmation. The dwarf companion galaxy NGC 7796-1 exhibits tidal tails, multiple nuclei, and very boxy isophotes. Conclusions: NGC 7796 is an old, massive isolated elliptical galaxy with no indications of later major star formation events as seen frequently in other isolated ellipticals. Its

  13. A Comparative Study of the Mass Distribution of Extreme-Ultraviolet-selected White Dwarfs

    NASA Astrophysics Data System (ADS)

    Napiwotzki, R.; Green, Paul J.; Saffer, Rex A.

    1999-05-01

    We present new determinations of effective temperature, surface gravity, and masses for a sample of 46 hot DA white dwarfs selected from the Extreme Ultraviolet Explorer (EUVE) and ROSAT Wide Field Camera bright source lists in the course of a near-infrared survey for low-mass companions. Our analysis, based on hydrogen non-LTE model atmospheres, provides a map of LTE correction vectors, which allow a thorough comparison with previous LTE studies. We find that previous studies underestimate both the systematic errors and the observational scatter in the determination of white dwarf parameters obtained via fits to model atmospheres. The structure of very hot or low-mass white dwarfs depends sensitively on their history. To compute white dwarf masses, we thus use theoretical mass-radius relations that take into account the complete evolution from the main sequence. We find a peak mass of our white dwarf sample of 0.59 Msolar, in agreement with the results of previous analyses. However, we do not confirm a trend of peak mass with temperature reported in two previous analyses. Analogous to other EUV-selected samples, we note a lack of low-mass white dwarfs and a large fraction of massive white dwarfs. Only one white dwarf is likely to have a helium core. While the lack of helium white dwarfs in our sample can be easily understood from their high cooling rate, and therefore low detection probability in our temperature range, this is not enough to explain the large fraction of massive white dwarfs. This feature very likely results from a decreased relative sample volume for low-mass white dwarfs caused by interstellar absorption in EUV-selected samples. Spectral observations reported here were obtained with the Multiple Mirror Telescope, a joint facility of the University of Arizona and the Smithsonian Institution, and with the Bok telescope at the Steward Observatory of the University of Arizona.

  14. How frequent are substellar companions in T Tauri binary systems?

    NASA Astrophysics Data System (ADS)

    Woitas, J.; Leinert, Ch.

    Using speckle interferometry we have determined the J-band magnitudes for the components of 27 close T Tauri multiples (separations <= 1 arcsec) in Taurus-Auriga detected by Leinert et al. (A&A 278, 129, 1993). The J-band is least affected by emission of circumstellar material, so it can be used as an estimator for a star's luminosity. Taking the spectral type of the system as that of the main component and assuming that both stars are coeval, we can place them into the HRD. A comparison with theoretical PMS evolution tracks by D'Antona & Mazzitelli (ApJS, 90, 467, 1994) yields the masses of the components. Since almost all T Tauri stars in Taurus-Auriga form in multiple systems (Leinert et al. ,1993, see above), the resultant mass function should be an estimation of the initial mass function (IMF) in this star forming region. The result is that the IMF has a turnover at M ~0.3M_{\\odot} and that there are not many brown dwarf candidates. Only three out of 57 stars, namely the companions of CZ Tau, FS Tau and Haro 6-28 seem to have masses close to or below the substellar limit. Multiplicity surveys of e. g. Koehler & Leinert (A&A 331, 977, 1998) have revealed that the binary frequency among T Tauri stars in Taurus-Auriga is about twice as high as that observed in the solar neighbourhood (Duquennoy & Mayor, A&A 248, 485, 1991). One proposed explanation for this overabundance is that there are many substellar companions that are relatively bright during their PMS evolution, but are not detectable on the main sequence stage. Our results suggest that this is in fact not the case.

  15. Stellar Companions as a Trigger for Rapid Dust Evolution

    NASA Astrophysics Data System (ADS)

    Pascucci, Ilaria; Apai, Daniel; Bouwman, Jeroen; Meyer, Michael

    2006-05-01

    The first steps of planet formation are marked by the growth and crystallization of sub-micrometer-sized dust grains. These steps have been identified in disks around young stars of different masses and, recently, even in disks around brown dwarfs. Although models suggest that stellar age and luminosity alone shall determine the extent of dust processing, recent observations show that grain growth and crystallinity can be very different even for coeval disks around stars of similar spectral type. This indicates the presence of at least a third important parameter. A number of studies in the past pointed out that multiplicity could play a major role in the disk evolution. But theoretical models have not yet reached a consensus on the efficiency of planet formation in the presence of companions. We propose here to investigate the effects of stellar companions on the initial steps of planet formation in protoplanetary disks. Our work will provide fundamental constraints on theoretical models of planet formation in multiple systems as well set the frame for the correct interpretation of the numerous Spitzer studies of dust in circumstellar disks. We selected a statistically significant sample of coeval disks around low-mass stars with well-known multiplicity to test the hypothesis that multiple systems have more processed dust disks (micron-sized grains and crystals). We have identified 59 spectra in the Spitzer archive from three different programs that have sufficient signal-to-noise to meet our goals. We will reduce and analyze these spectra in the same manner and determine the amount of large-to-small grains and crystals via the spectral decomposition of the 10 micron silicate emission feature. Our Monte Carlo simulations and Kolmogorov-Smirnov tests show that we will be able, for example, to discriminate between two populations with 10% and 20% crystalline mass fractions at a confidence level of 99%.

  16. Searching for Binary Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System (GeMS)

    NASA Astrophysics Data System (ADS)

    Opitz, Daniela; Tinney, Chris

    2015-08-01

    The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to be closely separated and are more frequently detected in near-equal mass configurations. The binary status of Y- type brown dwarfs is still unclear and therefore, determining if Y-type primaries hold the same trend, is of considerable interest. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results from a diffraction-limited study of a sample of five WISE Y dwarfs observed with the Gemini Multi-Conjugate Adaptive Optics System (GeMS). We find no evidence for binary companions in these data, which suggests these systems are not equal luminosity (or equivalently equal mass) binaries at separations larger than ~ 0.3-1.9 AU.

  17. Imaginary Play Companions: Characteristics and Functions.

    ERIC Educational Resources Information Center

    Kalyan-Masih, V.

    1986-01-01

    Investigates some of the following characteristics associated with young children playing with imaginary play companions (IPCs): intelligence, parental and socioeconomic and educational background, family size, and birth order. Compares these children to those without IPCs. (HOD)

  18. Video Otoscopy in Exotic Companion Mammals.

    PubMed

    Jekl, Vladimir; Hauptman, Karel; Knotek, Zdenek

    2015-09-01

    Ear disease is a common disorder seen in exotic companion mammals, especially in ferrets, rabbits, and rats. This article describes patient preparation, equipment, and video otoscopy technique in exotic companion mammals. This noninvasive technique facilitates accurate diagnosis of diseases affecting the external ear canal or middle ear. Moreover, therapeutic otoscopic evaluation of the external ear facilitates foreign body removal, external ear canal flushing, intralesional drug administration, myringotomy, and middle ear cavity flushing. PMID:26117517

  19. TWO NEW TIDALLY DISTORTED WHITE DWARFS

    SciTech Connect

    Hermes, J. J.; Montgomery, M. H.; Winget, D. E.; Kilic, Mukremin; Brown, Warren R.

    2012-04-10

    We identify two new tidally distorted white dwarfs (WDs), SDSS J174140.49+652638.7 and J211921.96-001825.8 (hereafter J1741 and J2119). Both stars are extremely low mass (ELM, {<=} 0.2 M{sub Sun }) WDs in short-period, detached binary systems. High-speed photometric observations obtained at the McDonald Observatory reveal ellipsoidal variations and Doppler beaming in both systems; J1741, with a minimum companion mass of 1.1 M{sub Sun }, has one of the strongest Doppler beaming signals ever observed in a binary system (0.59% {+-} 0.06% amplitude). We use the observed ellipsoidal variations to constrain the radius of each WD. For J1741, the star's radius must exceed 0.074 R{sub Sun }. For J2119, the radius exceeds 0.10 R{sub Sun }. These indirect radius measurements are comparable to the radius measurements for the bloated WD companions to A-stars found by the Kepler spacecraft, and they constitute some of the largest radii inferred for any WD. Surprisingly, J1741 also appears to show a 0.23% {+-} 0.06% reflection effect, and we discuss possible sources for this excess heating. Both J1741 and J2119 are strong gravitational wave sources, and the time-of-minimum of the ellipsoidal variations can be used to detect the orbital period decay. This may be possible on a timescale of a decade or less.

  20. The Origin of Prolate Rotation in Dwarf Spheroidal Galaxies Formed by Mergers of Disky Dwarfs

    NASA Astrophysics Data System (ADS)

    Ebrová, Ivana; Łokas, Ewa L.

    2015-11-01

    Motivated by the discovery of prolate rotation of stars in Andromeda II (And II), a dwarf spheroidal companion of M31, we study its origin via mergers of disky dwarf galaxies. We simulate merger events between two identical dwarfs changing the initial inclination of their disks with respect to the orbit and the amount of orbital angular momentum. On radial orbits, the amount of prolate rotation in the merger remnants correlates strongly with the inclination of the disks and is well understood as due to the conservation of the angular momentum component of the disks along the merger axis. For non-radial orbits, prolate rotation may still be produced if the orbital angular momentum is initially not much larger than the intrinsic angular momentum of the disks. The orbital structure of the remnants with significant rotation is dominated by box orbits in the center and long-axis tubes in the outer parts. The frequency analysis of stellar orbits in the plane perpendicular to the major axis reveals the presence of two families roughly corresponding to inner and outer long-axis tubes. The fraction of inner tubes is largest in the remnant forming from disks that are initially oriented most vertically, and is responsible for the boxy shape of the galaxy. We conclude that prolate rotation results from mergers with a variety of initial conditions and no fine tuning is necessary to reproduce this feature. We compare the properties of our merger remnants to those of dwarfs resulting from the tidal stirring scenario and the data for And II.

  1. [Companion diagnostics and reimbursement system].

    PubMed

    Tazawa, Yoshiaki

    2013-05-01

    Recently, Companion Diagnostics (CoDx) have been gaining importance to promote personalized medicine in order to improve the safety and cost effectiveness of therapy. In July 2011, the FDA published draft guidance for the development of CoDx, which recommends the co-development of CoDx and new drugs as the best practice, and then the FDA approved vemurafenib and the BRAF-V600-E gene mutation assay simultaneously as a typical example of the co-development of a new drug and its CoDx. Considering medical needs for multiple biomarker assays to select the right assay from various therapeutic candidates, more complicated assay technologies such as DNA sequencing will be required for CoDx in the near future. However, since it is quite difficult to standardize the validation process and manage test quality under the current regulatory criteria of in-vitro diagnostics using advanced and/or complicated assay technologies, the clinical use of laboratory-developed tests (LDT) should be recommended in order to avoid biomarker test lag. On the other hand, the current reimbursement system is not always suitable to assess the clinical and technological value of CoDx and it should be revised to encourage the development of CoDx. Although Health Technology Assessment (HTA) is a potential method to assess the value of CoDx, it is not easy to define appropriate indicators for CoDx because its clinical utility and cost effectiveness are completely dependent on the performance and value of available therapy. It is also suggested that the price and/or insurance rate of CoDx should be included in the price of the drug; however, there is no good solution to how to pay for CoDx with negative results for all therapies. It is said that the concept of personalized medicine with advanced technologies is a destructive innovation that could markedly change the current structure and system of medications; therefore, it is essential to create a quite new regulatory and reimbursement system to

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

    SciTech Connect

    Ren Juanjuan; Luo Ali; Li Yinbi; Wei Peng; Zhao Jingkun; Zhao Yongheng; Song Yihan; Zhao Gang E-mail: lal@nao.cas.cn

    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. 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.

  3. THE BINARY FRACTION OF LOW-MASS WHITE DWARFS

    SciTech Connect

    Brown, Justin M.; Kilic, Mukremin; Brown, Warren R.; Kenyon, Scott J.

    2011-04-01

    We describe spectroscopic observations of 21 low-mass ({<=}0.45 M{sub sun}) white dwarfs (WDs) from the Palomar-Green survey obtained over four years. We use both radial velocities and infrared photometry to identify binary systems, and find that the fraction of single, low-mass WDs is {<=}30%. We discuss the potential formation channels for these single stars including binary mergers of lower-mass objects. However, binary mergers are not likely to explain the observed number of single low-mass WDs. Thus, additional formation channels, such as enhanced mass loss due to winds or interactions with substellar companions, are likely.

  4. Three Wide Planetary-mass Companions to FW Tau, ROXs 12, and ROXs 42B

    NASA Astrophysics Data System (ADS)

    Kraus, Adam L.; Ireland, Michael J.; Cieza, Lucas A.; Hinkley, Sasha; Dupuy, Trent J.; Bowler, Brendan P.; Liu, Michael C.

    2014-01-01

    We report the discovery of three planetary-mass companions (M = 6-20 M Jup) in wide orbits (ρ ~ 150-300 AU) around the young stars FW Tau (Taurus-Auriga), ROXs 12 (Ophiuchus), and ROXs 42B (Ophiuchus). All three wide planetary-mass companions (PMCs) were reported as candidate companions in previous binary survey programs, but then were neglected for >10 yr. We therefore obtained followup observations that demonstrate that each candidate is comoving with its host star. Based on the absolute M_{K^{\\prime }} magnitudes, we infer masses (from hot-start evolutionary models) and projected separations of 10 ± 4 M Jup and 330 ± 30 AU for FW Tau b, 16 ± 4 M Jup and 210 ± 20 AU for ROXs 12, and 10 ± 4 M Jup and 140 ± 10 AU for ROXs 42B b. We also present similar observations for 10 other candidates that show that they are unassociated field stars, as well as multicolor JHK'L' near-infrared photometry for our new PMCs and for five previously identified substellar or planetary-mass companions. The near-infrared photometry for our sample of eight known and new companions generally parallels the properties of free-floating, low-mass brown dwarfs in these star-forming regions. However, five of the seven objects with M < 30 M Jup are redder in K' - L' than the distribution of young free-floating counterparts of similar J - K' color. We speculate that this distinction could indicate a structural difference in circumplanetary disks, perhaps tied to higher disk mass since at least two of the objects in our sample are known to be accreting more vigorously than typical free-floating counterparts.

  5. Three wide planetary-mass companions to FW Tau, ROXs 12, and ROXs 42B

    SciTech Connect

    Kraus, Adam L.; Ireland, Michael J.; Cieza, Lucas A.; Bowler, Brendan P.; Liu, Michael C.; Hinkley, Sasha; Dupuy, Trent J.

    2014-01-20

    We report the discovery of three planetary-mass companions (M = 6-20 M {sub Jup}) in wide orbits (ρ ∼ 150-300 AU) around the young stars FW Tau (Taurus-Auriga), ROXs 12 (Ophiuchus), and ROXs 42B (Ophiuchus). All three wide planetary-mass companions (PMCs) were reported as candidate companions in previous binary survey programs, but then were neglected for >10 yr. We therefore obtained followup observations that demonstrate that each candidate is comoving with its host star. Based on the absolute M{sub K{sup ′}} magnitudes, we infer masses (from hot-start evolutionary models) and projected separations of 10 ± 4 M {sub Jup} and 330 ± 30 AU for FW Tau b, 16 ± 4 M {sub Jup} and 210 ± 20 AU for ROXs 12, and 10 ± 4 M {sub Jup} and 140 ± 10 AU for ROXs 42B b. We also present similar observations for 10 other candidates that show that they are unassociated field stars, as well as multicolor JHK'L' near-infrared photometry for our new PMCs and for five previously identified substellar or planetary-mass companions. The near-infrared photometry for our sample of eight known and new companions generally parallels the properties of free-floating, low-mass brown dwarfs in these star-forming regions. However, five of the seven objects with M < 30 M {sub Jup} are redder in K' – L' than the distribution of young free-floating counterparts of similar J – K' color. We speculate that this distinction could indicate a structural difference in circumplanetary disks, perhaps tied to higher disk mass since at least two of the objects in our sample are known to be accreting more vigorously than typical free-floating counterparts.

  6. Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris

    NASA Astrophysics Data System (ADS)

    Lee, B.-C.; Han, I.; Park, M.-G.; Mkrtichian, D. E.; Hatzes, A. P.; Kim, K.-M.

    2014-06-01

    Aims: The aim of our paper is to investigate the low-amplitude and long-period variations in evolved stars with a precise radial velocity survey. Methods: The high-resolution, the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) was used from 2003 to 2013 for a radial velocity survey of giant stars as part of the exoplanet search program at Bohyunsan Optical Astronomy Observatory (BOAO). Results: We report the detection of three new planetary companions orbiting the K giants β Cnc, μ Leo, and β UMi. The planetary nature of the radial velocity variations is supported by analyzes of ancillary data. The Hipparcos photometry shows no variations with periods close to those in radial velocity variations and there is no strong correlation between the bisector velocity span (BVS) and the radial velocities for each star. Furthermore, the stars show weak or no core reversal in Ca II H lines indicating that they are inactive stars. The companion to β Cnc has a minimum mass of 7.8 MJup in a 605-day orbit with an eccentricity of 0.08. The giant μ Leo is orbited by a companion of minimum mass of 2.4 MJup having a period of 357 days and an eccentricity of 0.09. The giant β UMi is a known barium star and is suspected of harboring a white dwarf or substellar mass companion. Its companion has a minimum mass of 6.1 MJup, a period of 522 days, and an eccentricity e = 0.19. Based on observations made with the BOES instrument on the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory in Korea.Tables 4-6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/A67

  7. The X-ray evidence that the 51 Peg companion is a planet

    NASA Astrophysics Data System (ADS)

    Pravdo, Steven H.; Angelini, Lorella; Drake, Stephen A.; Stern, Robert A.; White, Nicholas E.

    1996-10-01

    51 Pegasi is a nearby G2-3 V star which is similar to the Sun. Mayor & Queloz (1995) [Natur, 378, 355] have recently found that 51 Peg has sinusoidal radial velocity variations with a period of 4.2 days and amplitude of 59 m/s. The radial velocity, if due to orbital motion around the system center-of-mass, implies a minimum companion mass of 0.47 Jupiter masses, which results from the assumption that the inclination angle of the system is 90° from the line of sight. However, because the inclination angle is not directly measured there remains an uncertainty in the companion mass. In the limit of a near-zero inclination angle the companion could even be a late-type dwarf star. We argue that the low measured X-ray luminosity of the 51 Peg system supports the conclusion that the companion is a planet, independent of any assumption about the inclination angle. If 51 Peg were a binary stellar system with a 4-day orbital period its X-ray emission would be in marked contrast with ALL known binary stellar systems with similar orbital periods. When compared to the distribution of binary star X-ray luminosities, a system with the 51 Peg X-ray luminosity have an occurrence probability of only 1.7 × 10 -6. The low X-ray luminosity also confirms that 51 Peg is a slow rotator based upon the correlation between X-ray emission and rotational velocity. We discuss the lack of synchronization between the 51 Peg orbital and rotational periods and calculate model-dependent upper limits on the companion mass which also indicate that it is a planet. Steven Beckwith

  8. SWIFT/UVOT PHOTOMETRY OF THE PLANETARY NEBULA WeBo 1: UNMASKING A FAINT HOT COMPANION STAR

    SciTech Connect

    Siegel, Michael H.; Hoversten, Erik; Stark, Michele; Bond, Howard E.; Breeveld, Alice A. E-mail: hoversten@swift.psu.edu E-mail: bond@stsci.edu

    2012-08-15

    We present an analysis of over 150 ks of data on the planetary nebula WeBo 1 (PN G135.6+01.0) obtained with the Swift Ultraviolet Optical Telescope (UVOT). The central object of this nebula has previously been described as a late-type K giant barium star with a possible hot companion, most likely a young pre-white dwarf. UVOT photometry shows that while the optical photometry is consistent with a large cool object, the near-ultraviolet (NUV) photometry shows far more UV flux than could be produced by any late-type object. Using model stellar atmospheres and a comparison to UVOT photometry for the pre-white dwarf PG 1159-035, we find that the companion has a temperature of at least 40,000 K and a radius of, at most, 0.056 R{sub Sun }. While the temperature and radius are consistent with a hot compact stellar remnant, they are lower and larger, respectively, than expected for a typical young pre-white dwarf. This likely indicates a deficiency in the assumed UV extinction curve. We find that higher temperatures more consistent with expectations for a pre-white dwarf can be derived if the foreground dust has a strong 'blue bump' at 2175 A and a lower R{sub V}. Our results demonstrate the ability of Swift to both uncover and characterize hot hidden companion stars and to constrain the UV extinction properties of foreground dust based solely on UVOT photometry.

  9. METALLICITY AND TEMPERATURE INDICATORS IN M DWARF K-BAND SPECTRA: TESTING NEW AND UPDATED CALIBRATIONS WITH OBSERVATIONS OF 133 SOLAR NEIGHBORHOOD M DWARFS

    SciTech Connect

    Rojas-Ayala, Barbara; Covey, Kevin R.; Lloyd, James P.; Muirhead, Philip S.

    2012-04-01

    We present K-band spectra for 133 nearby (d < 33 ps) M dwarfs, including 18 M dwarfs with reliable metallicity estimates (as inferred from an FGK type companion), 11 M dwarf planet hosts, more than 2/3 of the M dwarfs in the northern 8 pc sample, and several M dwarfs from the LSPM catalog. From these spectra, we measure equivalent widths of the Ca and Na lines, and a spectral index quantifying the absorption due to H{sub 2}O opacity (the H{sub 2}O-K2 index). Using empirical spectral type standards and synthetic models, we calibrate the H{sub 2}O-K2 index as an indicator of an M dwarf's spectral type and effective temperature. We also present a revised relationship that estimates the [Fe/H] and [M/H] metallicities of M dwarfs from their Na I, Ca I, and H{sub 2}O-K2 measurements. Comparisons to model atmosphere provide a qualitative validation of our approach, but also reveal an overall offset between the atomic line strengths predicted by models as compared to actual observations. Our metallicity estimates also reproduce expected correlations with Galactic space motions and H{alpha} emission line strengths, and return statistically identical metallicities for M dwarfs within a common multiple system. Finally, we find systematic residuals between our H{sub 2}O-based spectral types and those derived from optical spectral features with previously known sensitivity to stellar metallicity, such as TiO, and identify the CaH1 index as a promising optical index for diagnosing the metallicities of near-solar M dwarfs.

  10. DISCOVERY OF A LOW-MASS COMPANION TO A METAL-RICH F STAR WITH THE MARVELS PILOT PROJECT

    SciTech Connect

    Fleming, Scott W.; Ge Jian; Mahadevan, Suvrath; Lee, Brian; Cuong Nguyen, Duy; Morehead, Robert C.; Wan Xiaoke; Zhao Bo; Liu Jian; Guo Pengcheng; Kane, Stephen R.; Eastman, Jason D.; Siverd, Robert J.; Scott Gaudi, B.; Niedzielski, Andrzej; Sivarani, Thirupathi; Stassun, Keivan G.; Gary, Bruce; Wolszczan, Alex; Barnes, Rory

    2010-08-01

    We report the discovery of a low-mass companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) pilot project. The host star has an effective temperature T{sub eff} = 6135 {+-} 40 K, logg = 4.4 {+-} 0.1, and [Fe/H] = 0.32 {+-} 0.01, indicating a mass of M = 1.25 {+-} 0.09 M{sub sun} and R = 1.15 {+-} 0.15 R{sub sun}. The companion has an orbital period of 5.69449 {+-} 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M{sub J} , and thus may be an example of the rare class of brown dwarfs orbiting at distances comparable to those of 'Hot Jupiters'. We present relative photometry that demonstrates that the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius {approx}>0.8 R{sub J} at the 95% confidence level. Tidal analysis of the system suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first low-mass companion detected with a multi-object, dispersed, fixed-delay interferometer.

  11. A New Milky Way dwarf galaxy in Ursa Major

    SciTech Connect

    Willman, Beth; Dalcanton, Julianne J.; Martinez-Delgado, David; West, Andrew A.; Blanton, Michael R.; Hogg, David W.; Barentine, J.C.; Brewington, Howard J.; Harvanek, Michael; Kleinman, S.J.; Krzesinski, Jurek; Long, Dan; Neilsen, Eric H., Jr.; Nitta, Atsuko; Snedden, Stephanie A.; /CCPP, New York /Washington U., Seattle, Astron. Dept. /IAA, Granada /Heidelberg, Max Planck Inst. Astron. /Apache Point Observ. /Mt. Suhora Observ., Cracow /Fermilab

    2005-03-01

    In this Letter, we report the discovery of a new dwarf satellite to the Milky Way, located at ({alpha}{sub 2000}, {delta}{sub 2000}) = (158.72,51.92) in the constellation of Ursa Major. This object was detected as an overdensity of red, resolved stars in Sloan Digital Sky Survey data. The color-magnitude diagram of the Ursa Major dwarf looks remarkably similar to that of Sextans, the lowest surface brightness Milky Way companion known, but with approximately an order of magnitude fewer stars. Deeper follow-up imaging confirms this object has an old and metal-poor stellar population and is {approx} 100 kpc away. We roughly estimate M{sub V} = -6.75 and r{sub 1/2} = 250 pc for this dwarf. Its luminosity is several times fainter than the faintest known Milky Way dwarfs. However, its physical size is typical for dSphs. Even though its absolute magnitude and size are presently quite uncertain, Ursa Major is likely the lowest luminosity and lowest surface brightness galaxy yet known.

  12. Discovery of a nearby young brown dwarf binary candidate

    NASA Astrophysics Data System (ADS)

    Reiners, A.; Seifahrt, A.; Dreizler, S.

    2010-04-01

    In near-infrared NaCo observations of the young brown dwarf 2MASS J0041353-562112, we discovered a companion a little less than a magnitude fainter than the primary. The binary candidate has a separation of 143 mas, and the spectral types of the two components are M 6.5 and M 9.0. Colors and flux ratios of the components are consistent with their locations being at the same distance minimizing the probability of the secondary being a background object. The brown dwarf is known to exhibit Li absorption constraining the age to be younger than ~ 200 Myr, and has been suspected of experiencing ongoing accretion, which implies an age as young as ~ 10 Myr. We estimate distance and orbital parameters of the binary as a function of age. For an age of 10 Myr, the distance to the system is 50 pc, the orbital period is 126 yr, and the masses of the components are ~ 30 and ~ 15 MJup. The binary brown dwarf fills a so far unoccupied region in the parameters mass and age; it is a valuable new benchmark object for brown dwarf atmospheric and evolutionary models. Emmy Noether Fellow.

  13. The Coronal Abundances of Mid-F Dwarfs

    NASA Astrophysics Data System (ADS)

    Wood, Brian E.; Laming, J. Martin

    2013-05-01

    A Chandra spectrum of the moderately active nearby F6 V star π3 Ori is used to study the coronal properties of mid-F dwarfs. We find that π3 Ori's coronal emission measure distribution is very similar to those of moderately active G and K dwarfs, with an emission measure peak near log T = 6.6 seeming to be ubiquitous for such stars. In contrast to coronal temperature, coronal abundances are known to depend on spectral type for main sequence stars. Based on this previously known relation, we expected π3 Ori's corona to exhibit an extremely strong "first ionization potential (FIP) effect," a phenomenon first identified on the Sun where elements with low FIP are enhanced in the corona. We instead find that π3 Ori's corona exhibits a FIP effect essentially identical to that of the Sun and other early G dwarfs, perhaps indicating that the increase in FIP bias toward earlier spectral types stops or at least slows for F stars. We find that π3 Ori's coronal characteristics are significantly different from two previously studied mid-F stars, Procyon (F5 IV-V) and τ Boo (F7 V). We believe π3 Ori is more representative of the coronal characteristics of mid-F dwarfs, with Procyon being different because of luminosity class, and τ Boo being different because of the effects of one of two close companions, one stellar (τ Boo B: M2 V) and one planetary.

  14. The Spectral Character of Giant Planets and Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Burrows, A.; Marley, M.; Hubbard, W. B.; Sudarsky, D.; Sharp, C.; Lunine, J. I.; Guillot, T.; Saumon, D.; Freedman, R.

    Since October of 1995, employing Doppler spectroscopy, astronomers have discovered as many as 20 giant planets and brown dwarfs, including companions to tau Boo, 51 Peg, upsilon And, 55 Cnc, rho CrB, 70 Vir, 16 Cyg B, and 47 UMa. These discoveries have galvanized the planetary science community, astronomers, and the public at large. Within hours of the announcement of the planet 51 Peg b, the first direct detection of an unimpeachable brown dwarf, Gl 229 B, was also announced. Gl 229 B is a watershed since it has methane spectral features and a surface temperature below 1000 Kelvin, characteristics unique to objects with substellar masses. During the last two years, building upon our previous experience in the modeling of brown dwarfs and M stars, we published theoretical studies of the evolution and spectra of extrasolar giant planets. We have recently upgraded our capabilities and now generate non-gray spectral and color models of both giant planets and brown dwarfs. This theory will soon encompass objects whose effective temperatures range from 100 K to 4000 K and whose masses span three orders of magnitude. The evolutionary, spectral, and color calculations upon which we have embarked are in direct support of the searches now being planned in earnest with the HST (WFPC2, NICMOS), the IRTF, the MMT 6.5-meter upgrade, the Large Binocular Telescope (LBT), Keck's I and II, ISO, UKIRT, NGST, the VLT, COROT, DENIS, 2MASS, and SIRTF.

  15. Extreme Planet-Like Systems: Brown Dwarfs at the Exoplanet Mass Boundary

    NASA Astrophysics Data System (ADS)

    Faherty, Jacqueline Kelly

    2015-12-01

    Brown dwarfs have long been the observational anchors for our theoretical understanding of giant gas planets. Recent studies have uncovered a population of nearby young sources that rival the age and mass of many planetary mass companions. From detailed observations, we postulate that objects in this young population have dynamic atmospheres ripe with exotic, thick condensate cloud species that drive extreme photometric and spectroscopic characteristics. In this talk I will review how we are using these so-called exoplanet analogs to establish luminosity, temperature, age, and mass relations for brown dwarf into planetary mass objects.

  16. Structures induced by companions in galactic discs

    NASA Astrophysics Data System (ADS)

    Kyziropoulos, P. E.; Efthymiopoulos, C.; Gravvanis, G. A.; Patsis, P. A.

    2016-09-01

    Using N-body simulations we study the structures induced on a galactic disc by repeated flybys of a companion in decaying eccentric orbit around the disc. Our system is composed by a stellar disc, bulge and live dark matter halo, and we study the system's dynamical response to a sequence of a companion's flybys, when we vary i) the disc's temperature (parameterized by Toomre's Q-parameter) and ii) the companion's mass and initial orbit. We use a new 3D Cartesian grid code: MAIN (Mesh-adaptive Approximate Inverse N-body solver). The main features of MAIN are reviewed, with emphasis on the use of a new Symmetric Factored Approximate Sparse Inverse (SFASI) matrix in conjunction with the multigrid method that allows the efficient solution of Poisson's equation in three space variables. We find that: i) companions need to be assigned initial masses in a rather narrow window of values in order to produce significant and more long-standing non-axisymmetric structures (bars and spirals) in the main galaxy's disc by the repeated flyby mechanism. ii) a crucial phenomenon is the antagonism between companion-excited and self-excited modes on the disc. Values of Q > 1.5 are needed in order to allow for the growth of the companion-excited modes to prevail over the the growth of the disc's self-excited modes. iii) We give evidence that the companion-induced spiral structure is best represented by a density wave with pattern speed nearly constant in a region extending from the ILR to a radius close to, but inside, corotation.

  17. Zoonotic Poxviruses Associated with Companion Animals

    PubMed Central

    Tack, Danielle M.; Reynolds, Mary G.

    2011-01-01

    Simple Summary Contemporary enthusiasm for the ownership of exotic animals and hobby livestock has created an opportunity for the movement of poxviruses—such as monkeypox, cowpox, and orf—outside their traditional geographic range bringing them into contact with atypical animal hosts and groups of people not normally considered at risk. It is important that pet owners and practitioners of human and animal medicine develop a heightened awareness for poxvirus infections and understand the risks that can be associated with companion animals and livestock. This article reviews the epidemiology and clinical features of zoonotic poxviruses that are most likely to affect companion animals. Abstract Understanding the zoonotic risk posed by poxviruses in companion animals is important for protecting both human and animal health. The outbreak of monkeypox in the United States, as well as current reports of cowpox in Europe, point to the fact that companion animals are increasingly serving as sources of poxvirus transmission to people. In addition, the trend among hobbyists to keep livestock (such as goats) in urban and semi-urban areas has contributed to increased parapoxvirus exposures among people not traditionally considered at high risk. Despite the historic notoriety of poxviruses and the diseases they cause, poxvirus infections are often missed. Delays in diagnosing poxvirus-associated infections in companion animals can lead to inadvertent human exposures. Delays in confirming human infections can result in inappropriate treatment or prolonged recovery. Early recognition of poxvirus-associated infections and application of appropriate preventive measures can reduce the spread of virus between companion animals and their owners. This review will discuss the epidemiology and clinical features associated with the zoonotic poxvirus infections most commonly associated with companion animals. PMID:26486622

  18. A mid-infrared search for substellar companions of nearby planet-host stars

    SciTech Connect

    Hulsebus, A.; Marengo, M.; Carson, J.; Stapelfeldt, K.

    2014-03-20

    Determining the presence of widely separated substellar-mass companion is crucial to understand the dynamics of inner planets in extrasolar planetary systems (e.g., to explain their high mean eccentricity as inner planets are perturbed by the Kozai mechanism). We report the results of our Spitzer/Infrared Array Camera (IRAC) imaging search for widely separated (10''-25'') substellar-mass companions for 14 planet-host stars within 15 pc of the Sun. Using deep 3.6 and 4.5 μm observations in subarray mode, we found one object in the field of 47 UMa with [3.6]–[4.5] color similar to a T5 dwarf, which is, however, unlikely to share common proper motion with 47 UMa. We also found three objects with brown-dwarf-like [3.6]–[4.5] color limits in the fields of GJ 86, HD 160691, and GJ 581, as well as another in the field of HD 69830 for which we have excluded common proper motion. We provide model-based upper mass limits for unseen objects around all stars in our sample, with typical sensitivity to 10 M {sub J} objects from a projected separation of 50-300 AU from the parent star. We also discuss our data analysis methods for point-spread-function subtraction, image co-alignment, and artifact subtraction of IRAC subarray images.

  19. On the nature of the companion to Van Biesbroeck 8

    NASA Technical Reports Server (NTRS)

    Nelson, L. A.; Rappaport, S. A.; Joss, P. C.

    1985-01-01

    Results of the first numerical evolutionary calculations for very low-mass stars with ages up to the age of the Galaxy are presented. The calculations shed new light on the nature of the recently discovered object VB 8B, the companion to Van Biesbroeck's star no. 8, and support the identification of this object as a low-mass star in which hydrogen burning was never able to establish thermal equilibrium. For plausible ages of this binary stellar system, the mass of VB 8B is estimated to be in the range 0.04-0.08 solar mass. The object is supported primarily by degenerate electron pressure; its present values of central density and temperature are found to be 500-2000 g/cu cm and 1.0-1.5 million K. An orbital period of more than about 40 yr is predicted for the binary system. The presented evolutionary tracks are also applicable to the interpretation of observations of other very low-luminosity dwarfs.

  20. Asteroseismology of White Dwarf Stars

    NASA Technical Reports Server (NTRS)

    Hansen, Carl J.

    1997-01-01

    The primary purpose of this investigation has been to study various aspects of multimode pulsations in variable white dwarfs. In particular, nonlinear interactions among pulsation modes in white dwarfs (and, to some extent, in other variable stars), analysis of recent observations where such interactions are important, and preliminary work on the effects of crystallization in cool white dwarfs are reported.

  1. Using Close White Dwarf + M Dwarf Stellar Pairs to Constrain the Flare Rates in Close Stellar Binaries

    NASA Astrophysics Data System (ADS)

    Morgan, Dylan P.; West, Andrew A.; Becker, Andrew C.

    2016-05-01

    We present a study of the statistical flare rates of M dwarfs (dMs) with close white dwarf (WD) companions (WD+dM; typical separations <1 au). Our previous analysis demonstrated that dMs with close WD companions are more magnetically active than their field counterparts. One likely implication of having a close binary companion is increased stellar rotation through disk-disruption, tidal effects, and/or angular momentum exchange; increased stellar rotation has long been associated with an increase in stellar activity. Previous studies show a strong correlation between dMs that are magnetically active (showing Hα in emission) and the frequency of stellar flare rates. We examine the difference between the flare rates observed in close WD+dM binary systems and field dMs. Our sample consists of a subset of 181 close WD+dM pairs from Morgan et al. observed in the Sloan Digital Sky Survey Stripe 82, where we obtain multi-epoch observations in the Sloan ugriz-bands. We find an increase in the overall flaring fraction in the close WD+dM pairs (0.09 ± 0.03%) compared to the field dMs (0.0108 ± 0.0007%) and a lower flaring fraction for active WD+dMs (0.05 ± 0.03%) compared to active dMs (0.28 ± 0.05%). We discuss how our results constrain both the single and binary dM flare rates. Our results also constrain dM multiplicity, our knowledge of the Galactic transient background, and may be important for the habitability of attending planets around dMs with close companions.

  2. Reading Aloud: Companion Reader vs. No Companion Reader--An Experimental Research Study

    ERIC Educational Resources Information Center

    Ruivo, Paula

    2006-01-01

    This study has been done to gather data as to whether there is improvement in vocabulary development, reading comprehension and reading fluency when a child is reading aloud and he or she has a reading companion as opposed to not having a reading companion. As this literature review indicates there has been a lot of research on the benefits of…

  3. EX-111 Thermal Emission from Hot White Dwarfs: The Suggested He Abundance-Temperature Correlation. EX-112: The Unique Emission Line White Dwarf Star GD 356

    NASA Technical Reports Server (NTRS)

    Shipman, H. L.

    1986-01-01

    Progress in the EXOSAT data analysis program is reported. EXOSAT observations for four white dwarfs (WD1031-115, WD0004+330, WD1615-154, and WD0109-264) were obtained. Counting rates were unexpectedly low, indicating that these objects have a substantial amount of x-ray absorbing matter in their photosheres. In addition, soft x-ray pulsations characterized by a 9.25 minute cycle were discovered in the DA white dwarf V471 Tauri. A residual x-ray flux from the K dwarf companion can be seen during the white dwarf eclipse at orbital phase 0.0. Pronounced dips in the soft x-ray light curve occur at orbital phases 0.15, 0.18, and 0.85. The dips may be correlated with the triangular Lagrangian points of the binary orbit. Smaller dips at phases near the eclipse may be associated with cool loops in the K star corona. Data for the white dwarf H1504+65 was also analyzed. This object is particularly unusual in that its photoshere is devoid of hydrogen and helium. Finally, existing data on the white dwarf Sirius B were analyzed to see what constraints from other data can be placed on the properties of this star. Interrelationships between radius, rotational velocity, and effective temperature were derived.

  4. Genomic Analysis of Companion Rabbit Staphylococcus aureus

    PubMed Central

    Holmes, Mark A.; Harrison, Ewan M.; Fisher, Elizabeth A.; Graham, Elizabeth M.; Parkhill, Julian; Foster, Geoffrey; Paterson, Gavin K.

    2016-01-01

    In addition to being an important human pathogen, Staphylococcus aureus is able to cause a variety of infections in numerous other host species. While the S. aureus strains causing infection in several of these hosts have been well characterised, this is not the case for companion rabbits (Oryctolagus cuniculus), where little data are available on S. aureus strains from this host. To address this deficiency we have performed antimicrobial susceptibility testing and genome sequencing on a collection of S. aureus isolates from companion rabbits. The findings show a diverse S. aureus population is able to cause infection in this host, and while antimicrobial resistance was uncommon, the isolates possess a range of known and putative virulence factors consistent with a diverse clinical presentation in companion rabbits including severe abscesses. We additionally show that companion rabbit isolates carry polymorphisms within dltB as described as underlying host-adaption of S. aureus to farmed rabbits. The availability of S. aureus genome sequences from companion rabbits provides an important aid to understanding the pathogenesis of disease in this host and in the clinical management and surveillance of these infections. PMID:26963381

  5. Genomic Analysis of Companion Rabbit Staphylococcus aureus.

    PubMed

    Holmes, Mark A; Harrison, Ewan M; Fisher, Elizabeth A; Graham, Elizabeth M; Parkhill, Julian; Foster, Geoffrey; Paterson, Gavin K

    2016-01-01

    In addition to being an important human pathogen, Staphylococcus aureus is able to cause a variety of infections in numerous other host species. While the S. aureus strains causing infection in several of these hosts have been well characterised, this is not the case for companion rabbits (Oryctolagus cuniculus), where little data are available on S. aureus strains from this host. To address this deficiency we have performed antimicrobial susceptibility testing and genome sequencing on a collection of S. aureus isolates from companion rabbits. The findings show a diverse S. aureus population is able to cause infection in this host, and while antimicrobial resistance was uncommon, the isolates possess a range of known and putative virulence factors consistent with a diverse clinical presentation in companion rabbits including severe abscesses. We additionally show that companion rabbit isolates carry polymorphisms within dltB as described as underlying host-adaption of S. aureus to farmed rabbits. The availability of S. aureus genome sequences from companion rabbits provides an important aid to understanding the pathogenesis of disease in this host and in the clinical management and surveillance of these infections. PMID:26963381

  6. First light of the VLT planet finder SPHERE. I. Detection and characterization of the substellar companion GJ 758 B

    NASA Astrophysics Data System (ADS)

    Vigan, A.; Bonnefoy, M.; Ginski, C.; Beust, H.; Galicher, R.; Janson, M.; Baudino, J.-L.; Buenzli, E.; Hagelberg, J.; D'Orazi, V.; Desidera, S.; Maire, A.-L.; Gratton, R.; Sauvage, J.-F.; Chauvin, G.; Thalmann, C.; Malo, L.; Salter, G.; Zurlo, A.; Antichi, J.; Baruffolo, A.; Baudoz, P.; Blanchard, P.; Boccaletti, A.; Beuzit, J.-L.; Carle, M.; Claudi, R.; Costille, A.; Delboulbé, A.; Dohlen, K.; Dominik, C.; Feldt, M.; Fusco, T.; Gluck, L.; Girard, J.; Giro, E.; Gry, C.; Henning, T.; Hubin, N.; Hugot, E.; Jaquet, M.; Kasper, M.; Lagrange, A.-M.; Langlois, M.; Le Mignant, D.; Llored, M.; Madec, F.; Martinez, P.; Mawet, D.; Mesa, D.; Milli, J.; Mouillet, D.; Moulin, T.; Moutou, C.; Origné, A.; Pavlov, A.; Perret, D.; Petit, C.; Pragt, J.; Puget, P.; Rabou, P.; Rochat, S.; Roelfsema, R.; Salasnich, B.; Schmid, H.-M.; Sevin, A.; Siebenmorgen, R.; Smette, A.; Stadler, E.; Suarez, M.; Turatto, M.; Udry, S.; Vakili, F.; Wahhaj, Z.; Weber, L.; Wildi, F.

    2016-03-01

    GJ 758 B is a brown dwarf companion to a nearby (15.76%) solar-type, metal-rich (M / H = + 0.2 dex) main-sequence star (G9V) that was discovered with Subaru/HiCIAO in 2009. From previous studies, it has drawn attention as being the coldest (~600 K) companion ever directly imaged around a neighboring star. We present new high-contrast data obtained during the commissioning of the SPHERE instrument at the Very Large Telescope (VLT). The data was obtained in Y-, J-, H-, and Ks-bands with the dual-band imaging (DBI) mode of IRDIS, thus providing a broad coverage of the full near-infrared (near-IR) range at higher contrast and better spectral sampling than previously reported. In this new set of high-quality data, we report the re-detection of the companion, as well as the first detection of a new candidate closer-in to the star. We use the new eight photometric points for an extended comparison of GJ 758 B with empirical objects and four families of atmospheric models. From comparison to empirical object, we estimate a T8 spectral type, but none of the comparison objects can accurately represent the observed near-IR fluxes of GJ 758 B. From comparison to atmospheric models, we attribute a Teff = 600 ± 100 K, but we find that no atmospheric model can adequately fit all the fluxes of GJ 758 B. The lack of exploration of metal enrichment in model grids appears as a major limitation that prevents an accurate estimation of the companion physical parameters. The photometry of the new candidate companion is broadly consistent with L-type objects, but a second epoch with improved photometry is necessary to clarify its status. The new astrometry of GJ 758 B shows a significant proper motion since the last epoch. We use this result to improve the determination of the orbital characteristics using two fitting approaches: Least-Squares Monte Carlo and Markov chain Monte Carlo. We confirm the high-eccentricity of the orbit (peak at 0.5), and find a most likely semi-major axis of

  7. The Astrometric-Spectroscopic Binary System HIP 50796: An Overmassive Companion

    NASA Astrophysics Data System (ADS)

    Torres, Guillermo

    2006-02-01

    We report spectroscopic observations of the star HIP 50796, previously considered (but later rejected) as a candidate member of the TW Hya association. Our measurements reveal it to be a single-lined binary with an orbital period of 570 days and an eccentricity of e=0.61. The astrometric signature of this orbit was previously detected by Hipparcos in the form of curvature in the proper-motion components, although the period was unknown at the time. By combining our radial velocity measurements with the Hipparcos intermediate data (abscissa residuals) we are able to derive the full three-dimensional orbit and determine the dynamical mass of the unseen companion, as well as a revised trigonometric parallax that accounts for the orbital motion. Given our primary mass estimate of 0.73 Msolar (mid-K dwarf), the companion mass is determined to be 0.89 Msolar, or ~20% larger than the primary. The likely explanation for the larger mass without any apparent contribution to the light is that the companion is itself a closer binary composed of M dwarfs. The near-infrared excess and X-ray emission displayed by HIP 50796 support this. Our photometric modeling of the excess leads to a lower limit to the mass ratio of the close binary of q~0.8 and individual masses of 0.44-0.48 and 0.41-0.44 Msolar. The new parallax (π=20.6+/-1.9 mas) is significantly smaller than the original Hipparcos value and more precise.

  8. Search for light curve modulations among Kepler candidates. Three very low-mass transiting companions

    NASA Astrophysics Data System (ADS)

    Lillo-Box, J.; Ribas, A.; Barrado, D.; Merín, B.; Bouy, H.

    2016-07-01

    Context. Light curve modulations in the sample of Kepler planet candidates allows the disentangling of the nature of the transiting object by photometrically measuring its mass. This is possible by detecting the effects of the gravitational pull of the companion (ellipsoidal modulations) and in some cases, the photometric imprints of the Doppler effect when observing in a broad band (Doppler beaming). Aims: We aim to photometrically unveil the nature of some transiting objects showing clear light curve modulations in the phase-folded Kepler light curve. Methods: We selected a subsample among the large crop of Kepler objects of interest (KOIs) based on their chances to show detectable light curve modulations, i.e., close (a< 12 R⋆) and large (in terms of radius, according to their transit signal) candidates. We modeled their phase-folded light curves with consistent equations for the three effects, namely, reflection, ellipsoidal and beaming (known as REB modulations). Results: We provide detailed general equations for the fit of the REB modulations for the case of eccentric orbits. These equations are accurate to the photometric precisions achievable by current and forthcoming instruments and space missions. By using this mathematical apparatus, we find three close-in very low-mass companions (two of them in the brown dwarf mass domain) orbiting main-sequence stars (KOI-554, KOI-1074, and KOI-3728), and reject the planetary nature of the transiting objects (thus classifying them as false positives). In contrast, the detection of the REB modulations and transit/eclipse signal allows the measurement of their mass and radius that can provide important constraints for modeling their interiors since just a few cases of low-mass eclipsing binaries are known. Additionally, these new systems can help to constrain the similarities in the formation process of the more massive and close-in planets (hot Jupiters), brown dwarfs, and very low-mass companions.

  9. Plasma processes in cloud-forming exoplanet and brown dwarf atmospheres

    NASA Astrophysics Data System (ADS)

    Helling, Christiane

    2015-12-01

    The increasing number of observations of cyclotron emission, possible chromospheric emission, and potential aurorae suggests that high energy processes occur also in, or are associated with ultra-cool, cloud-forming atmospheres like in extrasolar planets and brown dwarfs. While a magnetic field is primordial to brown dwarfs and most planets, free charges in form of electrons need to be continuously produced to allow the necessary magnetic coupling for cyclotron emission to occur or for the formation of a chromosphere and possible magnetically driven winds to emerge. This is particularly critical for free floating objects not bathed in the wind of a host or companion star.We perform a reference study for late M-dwarfs, brown dwarfs and giant gas planets to identify which ultra-cool objects are most susceptible to plasma and magnetic processes. We utilise the Drift-Phoenix model grid where the local atmospheric structure is determined by the global parameters Teff , log(g) and metalicity [M/H]. For this reference study, thermal ionisation is considered only.Our results show that it is not unreasonable to expect Halfa or radio emission to origin from ultra-cool atmospheres as in particular the rarefied upper parts of the atmospheres can be magnetically coupleddespite having low degrees of thermal gas ionisation. The minimum threshold for the magnetic flux density required for electrons and ions to be magnetised is well above typical values of the global magnetic field of brown dwarfs and giant gas planets. Such atmospheres could therefore drive, e.g., auroral emission without the need for a companion's wind or an outgassing moon. The reference study is based on thermal emission and provides therefore a lower limit for plasma effects in late M-dwarfs, brown dwarfs and giant gas planets. We have shown that non-equilibrium processes like cloud discharges in form of lightning and coronal discharges, high wind speeds and cosmic rays increase the local electron budget

  10. Companion cropping to manage parasitic plants.

    PubMed

    Pickett, John A; Hamilton, Mary L; Hooper, Antony M; Khan, Zeyaur R; Midega, Charles A O

    2010-01-01

    Parasitic plants, through a range of infestation strategies, can attack crop plants and thereby require management. Because such problems often occur in resource-poor farming systems, companion cropping to manage parasitic plants is an appropriate approach. Many examples of companion cropping for this purpose have been reported, but the use of cattle forage legumes in the genus Desmodium as intercrops has been shown to be particularly successful in controlling the parasitic witchweeds (Striga spp.) that afflict approximately one quarter of sub-Saharan African cereal production. Through the use of this example, the development of effective companion crops is described, together with developments toward widespread adoption and understanding the underlying mechanisms, both for sustainability and ensuring food security, and also for exploitation beyond the cropping systems described here. PMID:20429664

  11. SPECTROSCOPY OF THE INNER COMPANION OF THE PULSAR PSR J0337+1715

    SciTech Connect

    Kaplan, David L.; Van Kerkwijk, Marten H.; Koester, Detlev; Stairs, Ingrid H.; Ransom, Scott M.; Archibald, Anne M.; Hessels, Jason W. T.; Boyles, Jason E-mail: mhvk@astro.utoronto.ca

    2014-03-01

    The hierarchical triple system PSR J0337+1715 offers an unprecedented laboratory to study secular evolution of interacting systems and to explore the complicated mass-transfer history that forms millisecond pulsars and helium-core white dwarfs. The latter in particular, however, requires knowledge of the properties of the individual components of the system. Here we present precise optical spectroscopy of the inner companion in the PSR J0337+1715 system. We confirm it as a hot, low-gravity DA white dwarf with T {sub eff} = 15, 800 ± 100 K and log{sub 10}(g) = 5.82 ± 0.05. We also measure an inner mass ratio of 0.1364 ± 0.0015, entirely consistent with that inferred from pulsar timing, and a systemic radial velocity of 29.7 ± 0.3 km s{sup –1}. Combined with the mass (0.19751 M {sub ☉}) determined from pulsar timing, our measurement of the surface gravity implies a radius of 0.091 ± 0.005 R {sub ☉}; combined further with the effective temperature and extinction, the photometry implies a distance of 1300 ± 80 pc. The high temperature of the companion is somewhat puzzling: with current models, it likely requires a recent period of unstable hydrogen burning, and suggests a surprisingly short lifetime for objects at this phase in their evolution. We discuss the implications of these measurements in the context of understanding the PSR J0337+1715 system, as well as of low-mass white dwarfs in general.

  12. Characterization of the Gaseous Companion k Andromedae B* New Keck and LBTI High-contrast Observations

    NASA Technical Reports Server (NTRS)

    Bonnefoy, M.; Currie, T.; Marleau, G.-D.; Schlieder, J. E.; Wisniewski, J.; Carson, J.; Covey, K. R.; Henning, T.; Biller, B.; Hinz, P.; Klahr, H.; Boyer, A. N. Marsh; Zimmerman, N.; Janson, M.; McElwain, M.; Mordasini, C.; Skemer, A.; Bailey, V.; Defrere, D.; Thalmann, C.; Skrutskie, M.; Allard, F.; Homeier, D.; Tamura, M.; Grady, C.

    2013-01-01

    Context. We previously reported the direct detection of a low mass companion at a projected separation of 55+/-2 astronomical units around the B9 type star kappa Andromedae. The properties of the system (mass ratio, separation) make it a benchmark for the understanding of the formation and evolution of gas giant planets and brown dwarfs on wide-orbits. Aims. We present new angular differential imaging (ADI) images of the system at 2.146 (K(sub s)), 3.776 (L'), 4.052 (NB 4.05) and 4.78 micrometers (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as more accurate near-infrared photometry of the star with the MIMIR instrument. We aim to determine the near-infrared spectral energy distribution (SED) of the companion and use it to characterize the object. Methods. We used analysis methods adapted to ADI to extract the companion flux. We compared the photometry of the object to reference young/old objects and to a set of seven PHOENIX-based atmospheric models of cool objects accounting for the formation of dust. We used evolutionary models to derive mass estimates considering a wide range of plausible initial conditions. Finally, we used dedicated formation models to discuss the possible origin of the companion. Results. We derive a more accurate J = 15.86 +/- 0.21, H = 14.95 +/- 0.13, K(sub s) = 14.32 +/- 0.09 mag for kappa And b. We redetect the companion in all our high contrast observations. We confirm previous contrasts obtained at K(sub s) and L' band. We derive NB 4.05 = 13.0 +/- 0.2 and M' = 13.3 +/- 0.3 mag and estimate Log(base 10)(L/solar luminosity) = -3.76 +/- 0.06. Atmospheric models yield T(sub eff) = 1900(+100/-200) K. They do not set constrains on the surface gravity. "Hot-start" evolutionary models predict masses of 14(+25/-2) Jupiter mass based on the luminosity and temperature estimates, and considering a conservative age range for the system (30(+120/-10) million years). "warm-start" evolutionary tracks constrain the mass to M greater than or

  13. Accretion onto Planetary Mass Companions of Low-mass Young Stars

    NASA Astrophysics Data System (ADS)

    Zhou, Yifan; Herczeg, Gregory J.; Kraus, Adam L.; Metchev, Stanimir; Cruz, Kelle L.

    2014-03-01

    Measurements of accretion rates onto planetary mass objects may distinguish between different planet formation mechanisms, which predict different accretion histories. In this Letter, we use Hubble Space Telescope (HST)/WFC3 UVIS optical photometry to measure accretion rates onto three accreting objects, GSC 06214-00210 b, GQ Lup b, and DH Tau b, that are at the planet/brown dwarf boundary and are companions to solar mass stars. The excess optical emission in the excess accretion continuum yields mass accretion rates of 10-9-10-11 M ⊙ yr-1 for these three objects. Their accretion rates are an order of magnitude higher than expected from the correlation between mass and accretion rates measured from the UV excess, which is applicable if these wide planetary mass companions formed by protostellar core fragmentation. The high accretion rates and large separation from the central star demonstrate the presence of massive disks around these objects. Models for the formation and evolution of wide planetary mass companions should account for their large accretion rates. High ratios of Hα luminosity over accretion luminosity for objects with low accretion rates suggest that searches for Hα emission may be an efficient way to find accreting planets.

  14. Limits on Stellar Companions to Exoplanet Host Stars with Eccentric Planets

    NASA Astrophysics Data System (ADS)

    Kane, Stephen R.; Howell, Steve B.; Horch, Elliott P.; Feng, Ying; Hinkel, Natalie R.; Ciardi, David R.; Everett, Mark E.; Howard, Andrew W.; Wright, Jason T.

    2014-04-01

    Though there are now many hundreds of confirmed exoplanets known, the binarity of exoplanet host stars is not well understood. This is particularly true of host stars that harbor a giant planet in a highly eccentric orbit since these are more likely to have had a dramatic dynamical history that transferred angular momentum to the planet. Here we present observations of four exoplanet host stars that utilize the excellent resolving power of the Differential Speckle Survey Instrument on the Gemini North telescope. Two of the stars are giants and two are dwarfs. Each star is host to a giant planet with an orbital eccentricity >0.5 and whose radial velocity (RV) data contain a trend in the residuals to the Keplerian orbit fit. These observations rule out stellar companions 4-8 mag fainter than the host star at passbands of 692 nm and 880 nm. The resolution and field of view of the instrument result in exclusion radii of 0.''05-1.''4, which excludes stellar companions within several AU of the host star in most cases. We further provide new RVs for the HD 4203 system that confirm that the linear trend previously observed in the residuals is due to an additional planet. These results place dynamical constraints on the source of the planet's eccentricities, place constraints on additional planetary companions, and inform the known distribution of multiplicity amongst exoplanet host stars.

  15. EFFECTS OF A COMPANION STAR ON SLOW NOVA OUTBURSTS-TRANSITION FROM STATIC TO WIND EVOLUTIONS

    SciTech Connect

    Kato, Mariko; Hachisu, Izumi E-mail: hachisu@ea.c.u-tokyo.ac.jp

    2011-12-20

    Two types of nova evolutions can occur in low-mass white dwarfs of {approx}0.5-0.7 M{sub Sun }, i.e., an evolution with optically thick winds like in usual classical novae, or an another type of evolution without them like in the symbiotic nova PU Vul. The latter type is characterized by spectra with no indication of strong winds as well as a long-lasting flat optical peak in its light curve. We propose a transition from evolution with no optically thick wind to usual evolution with optically thick winds as a new outburst model for slow novae that show a relatively long-lasting multipeak phase followed by a wind phase like in the slow novae V723 Cas, HR Del, and V5558 Sgr. We calculated nova envelopes with one-dimensional approximation of the companion's effects and found that when the companion star is deeply embedded in the extended nova envelope, the structure of the static envelope approaches that of the optically thick wind solution. Thus, the transition from static to wind solution is triggered by the effect of the companion. The transition occurs in a close binary nova like V723 Cas, but is not triggered in a long-period binary like PU Vul. We reconfirm our previous results that the frictional energy deposition is negligibly small in almost all hydrogen/helium novae because of the low envelope density at the orbit.

  16. Limits on stellar companions to exoplanet host stars with eccentric planets

    SciTech Connect

    Kane, Stephen R.; Hinkel, Natalie R.; Howell, Steve B.; Horch, Elliott P.; Feng, Ying; Wright, Jason T.; Ciardi, David R.; Everett, Mark E.; Howard, Andrew W.

    2014-04-20

    Though there are now many hundreds of confirmed exoplanets known, the binarity of exoplanet host stars is not well understood. This is particularly true of host stars that harbor a giant planet in a highly eccentric orbit since these are more likely to have had a dramatic dynamical history that transferred angular momentum to the planet. Here we present observations of four exoplanet host stars that utilize the excellent resolving power of the Differential Speckle Survey Instrument on the Gemini North telescope. Two of the stars are giants and two are dwarfs. Each star is host to a giant planet with an orbital eccentricity >0.5 and whose radial velocity (RV) data contain a trend in the residuals to the Keplerian orbit fit. These observations rule out stellar companions 4-8 mag fainter than the host star at passbands of 692 nm and 880 nm. The resolution and field of view of the instrument result in exclusion radii of 0.''05-1.''4, which excludes stellar companions within several AU of the host star in most cases. We further provide new RVs for the HD 4203 system that confirm that the linear trend previously observed in the residuals is due to an additional planet. These results place dynamical constraints on the source of the planet's eccentricities, place constraints on additional planetary companions, and inform the known distribution of multiplicity amongst exoplanet host stars.

  17. Barley Yellow Dwarf

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Barley yellow dwarf is the most economically important virus disease affecting most cereal crops world wide. This manuscript summarizes the current knowledge of the disease etiology, epidemiology and management. This information is incorporated into the latest revision of the American Phytopathologi...

  18. Barley Yellow Dwarf Virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Barley yellow dwarf (BYD) is the most widespread and economically important virus disease of cereals. The viruses causing BYD were initially grouped based on common biological properties, including persistent and often strain-specific transmission by aphids and induction of yellowing symptoms. The...

  19. Dwarf Eye Disorder

    ERIC Educational Resources Information Center

    Science Teacher, 2005

    2005-01-01

    Johns Hopkins researchers at the Wilmer Eye Institute have discovered what appears to be the first human gene mutation that causes extreme farsightedness. The researchers report that nanophthalmos, Greek for "dwarf eye," is a rare, potentially blinding disorder caused by an alteration in a gene called MFRP that helps control eye growth and…

  20. White Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Kepler, S. O.

    2014-10-01

    White dwarfs are the evolutionary endpoint for nearly 95% of all stars born in our Galaxy, the final stages of evolution of all low- and intermediate mass stars, i.e., main sequence stars with masses below (8.5± 1.5) M_{odot}, depending on metallicity of the progenitor, mass loss and core overshoot. Massive white dwarfs are intrinsically rare objects, tand produce a gap in the determination of the initial vs. final mass relation at the high mass end (e.g. Weidemann 2000 A&A, 363, 647; Kalirai et al. 2008, ApJ, 676, 594; Williams, Bolte & Koester 2009, ApJ, 693, 355). Main sequences stars with higher masses will explode as SNII (Smartt S. 2009 ARA&A, 47, 63), but the limit does depend on the metallicity of the progenitor. Massive white dwarfs are probably SNIa progenitors through accretion or merger. They are rare, being the final product of massive stars (less common) and have smaller radius (less luminous). Kepler et al. 2007 (MNRAS, 375, 1315), Kleinman et al. 2013 (ApJS, 204, 5) estimate only 1-2% white dwarfs have masses above 1 M_{odot}. The final stages of evolution after helium burning are a race between core growth and loss of the H-rich envelope in a stellar wind. When the burning shell is exposed, the star rapidly cools and burning ceases, leaving a white dwarf. As they cool down, the magnetic field freezes in, ranging from a few kilogauss to a gigagauss. Peculiar type Ia SN 2006gz, SN 2007if, SN 2009dc, SN 2003fg suggest progenitors in the range 2.4-2.8 M_{odot}, and Das U. & Mukhopadhyay B. (2012, Phys. Rev. D, 86, 042001) estimate that the Chandrasekhar limit increases to 2.3-2.6 M_{odot} for extremely high magnetic field stars, but differential rotation induced by accretion could also increase it, according to Hachisu I. et al. 2012 (ApJ, 744, 69). García-Berro et al. 2012, ApJ, 749, 25, for example, proposes double degenerate mergers are the progenitors of high-field magnetic white dwarfs. We propose magnetic fields enhance the line broadening in

  1. SPECTROSCOPIC CONFIRMATION OF UV-BRIGHT WHITE DWARFS FROM THE SANDAGE TWO-COLOR SURVEY OF THE GALACTIC PLANE

    SciTech Connect

    Lepine, Sebastien; Bergeron, P.; Lanning, Howard H.

    2011-03-15

    We present spectroscopic observations confirming the identification of hot white dwarfs among UV-bright sources from the Sandage Two-color Survey of the Galactic Plane and listed in the Lanning (Lan) catalog of such sources. A subsample of 213 UV-bright Lan sources have been identified as candidate white dwarfs based on the detection of a significant proper motion. Spectroscopic observations of 46 candidates with the KPNO 2.1 m telescope confirm 30 sources to be hydrogen white dwarfs with subtypes in the DA1-DA6 range, and with one of the stars (Lan 161) having an unresolved M dwarf as a companion. Five more sources are confirmed to be helium white dwarfs, with subtypes from DB3 to DB6. One source (Lan 364) is identified as a DZ 3 white dwarf, with strong lines of calcium. Three more stars are found to have featureless spectra (to within detection limits) and are thus classified as DC white dwarfs. In addition, three sources are found to be hot subdwarfs: Lan 20 and Lan 480 are classified as sdOB, and Lan 432 is classified sdB. The remaining four objects are found to be field F star interlopers. Physical parameters of the DA and DB white dwarfs are derived from model fits.

  2. The Resolved Stellar Halo and Dwarf Satellite Population of NGC 3109

    NASA Astrophysics Data System (ADS)

    Hargis, Jonathan R.; Crnojevic, Denija; Sand, David J.; Willman, Beth; Spekkens, Kristine; Grillmair, Carl J.; Strader, Jay

    2016-01-01

    The stellar halo and halo substructure of dwarf galaxies provides an important window into both LCDM cosmology and galaxy formation theory on the smallest scales. We are undertaking a deep, wide-field imaging survey of nearby, isolated sub-Milky Way mass galaxies in order to (1) map the substructure, spatial extent, and metallicity of their stellar halos in resolved stars, and (2) search for faint dwarf satellite companions (i.e., the ``dwarfs of dwarfs"). These studies will allow us to explore the role of in-situ versus accretion processes in forming stellar halos in dwarfs, as well as constrain the faint end of the satellite galaxy luminosity function. This work presents a preliminary analysis of the pilot galaxy in our survey: NGC 3109 (Mv = -15 mag), a nearby (d = 1.3 Mpc) dwarf irregular, approximately 1/6th the stellar mass of the SMC. We imaged ~40 sq. deg around NGC 3109 (projected radius of ~100 kpc) using CTIO 4m/DECam to depths ~2 mag below the TRGB. We disovered a new gas-rich dwarf satellite of NGC 3109, dubbed Antlia B (Mv = -9.7 mag), similar to the recently-discovered Leo P. We also discovered five candidate dwarf satellites, with sizes (~100 pc) and luminosities (Mv ~ -6 mag) consistent with being ultra-faint dwarfs at the distance of NGC 3109. Lastly, we present stellar halo maps of resolved RGB stars on both large and small scales. We discuss the various substructures found in these maps and the future directions of our survey. This work was supported by NSF AST-1151462.

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

    SciTech Connect

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

    2015-02-10

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

  4. Supernova SN 2011fe from an exploding carbon-oxygen white dwarf star.

    PubMed

    Nugent, Peter E; Sullivan, Mark; Cenko, S Bradley; Thomas, Rollin C; Kasen, Daniel; Howell, D Andrew; Bersier, David; Bloom, Joshua S; Kulkarni, S R; Kandrashoff, Michael T; Filippenko, Alexei V; Silverman, Jeffrey M; Marcy, Geoffrey W; Howard, Andrew W; Isaacson, Howard T; Maguire, Kate; Suzuki, Nao; Tarlton, James E; Pan, Yen-Chen; Bildsten, Lars; Fulton, Benjamin J; Parrent, Jerod T; Sand, David; Podsiadlowski, Philipp; Bianco, Federica B; Dilday, Benjamin; Graham, Melissa L; Lyman, Joe; James, Phil; Kasliwal, Mansi M; Law, Nicholas M; Quimby, Robert M; Hook, Isobel M; Walker, Emma S; Mazzali, Paolo; Pian, Elena; Ofek, Eran O; Gal-Yam, Avishay; Poznanski, Dovi

    2011-12-15

    Type Ia supernovae have been used empirically as 'standard candles' to demonstrate the acceleration of the expansion of the Universe even though fundamental details, such as the nature of their progenitor systems and how the stars explode, remain a mystery. There is consensus that a white dwarf star explodes after accreting matter in a binary system, but the secondary body could be anything from a main-sequence star to a red giant, or even another white dwarf. This uncertainty stems from the fact that no recent type Ia supernova has been discovered close enough to Earth to detect the stars before explosion. Here we report early observations of supernova SN 2011fe in the galaxy M101 at a distance from Earth of 6.4 megaparsecs. We find that the exploding star was probably a carbon-oxygen white dwarf, and from the lack of an early shock we conclude that the companion was probably a main-sequence star. Early spectroscopy shows high-velocity oxygen that slows rapidly, on a timescale of hours, and extensive mixing of newly synthesized intermediate-mass elements in the outermost layers of the supernova. A companion paper uses pre-explosion images to rule out luminous red giants and most helium stars as companions to the progenitor. PMID:22170680

  5. Supernova SN 2011fe from an exploding carbon-oxygen white dwarf star

    NASA Astrophysics Data System (ADS)

    Nugent, Peter E.; Sullivan, Mark; Cenko, S. Bradley; Thomas, Rollin C.; Kasen, Daniel; Howell, D. Andrew; Bersier, David; Bloom, Joshua S.; Kulkarni, S. R.; Kandrashoff, Michael T.; Filippenko, Alexei V.; Silverman, Jeffrey M.; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard T.; Maguire, Kate; Suzuki, Nao; Tarlton, James E.; Pan, Yen-Chen; Bildsten, Lars; Fulton, Benjamin J.; Parrent, Jerod T.; Sand, David; Podsiadlowski, Philipp; Bianco, Federica B.; Dilday, Benjamin; Graham, Melissa L.; Lyman, Joe; James, Phil; Kasliwal, Mansi M.; Law, Nicholas M.; Quimby, Robert M.; Hook, Isobel M.; Walker, Emma S.; Mazzali, Paolo; Pian, Elena; Ofek, Eran O.; Gal-Yam, Avishay; Poznanski, Dovi

    2011-12-01

    Type Ia supernovae have been used empirically as `standard candles' to demonstrate the acceleration of the expansion of the Universe even though fundamental details, such as the nature of their progenitor systems and how the stars explode, remain a mystery. There is consensus that a white dwarf star explodes after accreting matter in a binary system, but the secondary body could be anything from a main-sequence star to a red giant, or even another white dwarf. This uncertainty stems from the fact that no recent type Ia supernova has been discovered close enough to Earth to detect the stars before explosion. Here we report early observations of supernova SN 2011fe in the galaxy M101 at a distance from Earth of 6.4 megaparsecs. We find that the exploding star was probably a carbon-oxygen white dwarf, and from the lack of an early shock we conclude that the companion was probably a main-sequence star. Early spectroscopy shows high-velocity oxygen that slows rapidly, on a timescale of hours, and extensive mixing of newly synthesized intermediate-mass elements in the outermost layers of the supernova. A companion paper uses pre-explosion images to rule out luminous red giants and most helium stars as companions to the progenitor.

  6. Trigonometric parallaxes of young field L dwarfs

    NASA Astrophysics Data System (ADS)

    Zapatero Osorio, M. R.; Béjar, V. J. S.; Miles-Páez, P. A.; Peña Ramírez, K.; Rebolo, R.; Pallé, E.

    2014-08-01

    Aims: We aim to determine the trigonometric parallaxes and proper motions of a sample of ten field L0-L5 dwarfs with spectroscopic evidence for low-gravity atmospheres. The ten sources were located in color-absolute magnitude diagrams and in the Hertzsprung-Russell (HR) diagram for age and mass derivations and were compared with field and star cluster dwarfs of related spectral classification and with state-of-the-art solar-metallicity evolutionary models. Methods: We obtained J and Ks imaging data using 2-4 m class telescopes with a typical cadence of one image per month between 2010 January and 2012 December, in which the data cover a time baseline of nearly three years. We also obtained low resolution optical spectra (R ~ 300, 500-1100 nm) using the 10 m Gran Telescopio de Canarias to assess the presence of lithium absorption in four targets and confirm their young age. The derived parallaxes and proper motions were combined with data from the literature to determine Teff, luminosity, and space velocities. All this information along with the lithium observations was used to assess the ages and masses of the sample. The astrometric curves were also examined for periodic perturbations indicative of unseen companions. Results: Trigonometric parallaxes and proper motions were derived to typical accuracies of a milliarcsecond (mas) and ±10 mas yr-1, respectively. All ten L dwarfs have large motions (μ ≥ 70 mas yr-1) and are located at distances between 9 and 47 pc. They lie above and on the sequence of field dwarfs in the diagrams of absolute J and Ks magnitude versus spectral type and luminosity versus effective temperature, which implies ages similar to or smaller than those typical of the field. In the HR diagram, 2MASS J00332386-1521309 (L4), 2MASS J00452143+1634446 (L2), 2MASS J03552337+1133437 (L5), 2MASS J05012406-0010452 (L4), G 196-3B (L3), 2MASS J17260007+1538190 (L3), and 2MASS J22081363+2921215 (L3) occupy locations that are compatible with the most

  7. When Toddlers Provide Care: Infants Companion Space.

    ERIC Educational Resources Information Center

    Braten, Stein

    1996-01-01

    Hypothesizes regarding factors that enhance prosociality in children, implying that the quality of childrearing and early companionship have profound impact on toddlers' social behavior. Discusses observation space versus companion space, prosocial behavior across cultures, when toddlers abuse, and the implications of a circular reenactment of…

  8. Asteroidal companions in the visible: HST data

    NASA Astrophysics Data System (ADS)

    Storrs, Alex; Vilas, Faith; Landis, Rob; Gaffey, Michael J.; Makhoul, Khaldoun; Davis, MIke; Richmond, Mike

    2016-01-01

    We present a reanalysis of HST images of five asteroids with known companions (45 Eugenia, 87 Sylvia, 93 Minerva, 107 Camilla, 121 Hermione). It is remarkable that all of these companion bodies are much redder in the visible region than their primary bodies. Storrs et al. (2009, BAAS vol. 41, no. 4, p 189) attributed this to space weathering, however, all of these bodies belong to dark C- or X-type groups. Current modeling of space weathering effects are limited to bright asteroids (e.g. Cloutis et al., Icarus 252, pp. 39-82, 2015) and show little change on the scale reported here. We suggest that the interaction of dark, possibly organic-rich surfaces with the solar wind produces reddening on a much greater scale than is observed in bright, silica-rich surfaces, and that this effect is easily reset by collisions. Thus, while both the parent and companion object accumulate the effects, the parent is much more likely to be "reset" by small collisions than the companion, due to the differences in their cross-sections.

  9. Polaris: Amplitude, Period Change, and Companions

    NASA Astrophysics Data System (ADS)

    Evans, N. R.; Sasselov, D. D.; Short, C. I.

    2000-12-01

    Amplitude: Polaris has presented us with the rare phenomenon of a Cepheid with a pulsation amplitude which has decreased over the last 50 years. In this study we investigate whether the amplitude decrease during the last 15 years has had any effect on upper atmosphere heating. We obtained IUE high and low resolution spectra but found no change in either the Mg II chromospheric emission or the flux at 1800 Å/ between 1978 and 1993 when the pulsation amplitude dropped by 50 % (from 2.8 to 1.6 km sec-1). The energy distribution from 1700 Å/ through V, B, R(KC), and I(KC) is like that of a nonvariable supergiant of the same color rather than a full amplitude Cepheid in that it has nonradiative flux at 1800 Å/ which the full amplitude Cepheid δ Cep lacks. Period Change: Polaris also has a rapidly changing period (3.2 sec/year), in common with other overtone pulsators. We argue that this is a natural consequence of the different envelope locations which dominate in growth rates in fundamental and overtone pulsation. In fundamental mode pulsators, the deeper envelope is more important in determining growth rates than for overtone pulsators. For fundamental mode pulsators, evolutionary changes in the radius produce approximately linear changes in period. In overtone pulsators, pulsation reacts to small evolutionary changes in a more unstable way because the modes are more sensitive to high envelope features such as opacity bumps, and the growth rates for the many closely spaced overtone modes change easily. Companions: The upper limit to the X-ray flux from an Einstein observation implies that the companion in the astrometric orbit is probably earlier than F4 V. The combination of upper and lower limits on the companion from IUE and Einstein respectively catch the companion mass between 1.7 and 1.4 M⊙ . The X-ray limit is consistent with the more distant companion α UMi B being a physical companion in a hierarchal triple system. However the X-ray limits imply that

  10. The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits. II. Survey description, results, and performances

    NASA Astrophysics Data System (ADS)

    Chauvin, G.; Vigan, A.; Bonnefoy, M.; Desidera, S.; Bonavita, M.; Mesa, D.; Boccaletti, A.; Buenzli, E.; Carson, J.; Delorme, P.; Hagelberg, J.; Montagnier, G.; Mordasini, C.; Quanz, S. P.; Segransan, D.; Thalmann, C.; Beuzit, J.-L.; Biller, B.; Covino, E.; Feldt, M.; Girard, J.; Gratton, R.; Henning, T.; Kasper, M.; Lagrange, A.-M.; Messina, S.; Meyer, M.; Mouillet, D.; Moutou, C.; Reggiani, M.; Schlieder, J. E.; Zurlo, A.

    2015-01-01

    Context. Young, nearby stars are ideal targets for direct imaging searches for giant planets and brown dwarf companions. After the first-imaged planet discoveries, vast efforts have been devoted to the statistical analysis of the occurence and orbital distributions of giant planets and brown dwarf companions at wide (≥5-6 AU) orbits. Aims: In anticipation of the VLT/SPHERE planet-imager, guaranteed-time programs, we have conducted a preparatory survey of 86 stars between 2009 and 2013 to identify new faint comoving companions to ultimately analyze the occurence of giant planets and brown dwarf companions at wide (10-2000 AU) orbits around young, solar-type stars. Methods: We used NaCo at VLT to explore the occurrence rate of giant planets and brown dwarfs between typically 0.1 and 8''. Diffraction-limited observations in H-band combined with angular differential imaging enabled us to reach primary star-companion brightness ratios as small as 10-6 at 1.5''. Repeated observations at several epochs enabled us to discriminate comoving companions from background objects. Results: During our survey, twelve systems were resolved as new binaries, including the discovery of a new white dwarf companion to the star HD 8049. Around 34 stars, at least one companion candidate was detected in the observed field of view. More than 400 faint sources were detected; 90% of them were in four crowded fields. With the exception of HD 8049 B, we did not identify any new comoving companions. The survey also led to spatially resolved images of the thin debris disk around HD 61005 that have been published earlier. Finally, considering the survey detection limits, we derive a preliminary upper limit on the frequency of giant planets for the semi-major axes of [10, 2000] AU: typically less than 15% between 100 and 500 AU and less than 10% between 50 and 500 AU for exoplanets that are more massive than 5 MJup and 10 MJup respectively, if we consider a uniform input distribution and a

  11. A Case Study for a Tidal Interaction between Dwarf Galaxies in UGC 6741

    NASA Astrophysics Data System (ADS)

    Paudel, Sanjaya; Duc, P. A.; Ree, C. H.

    2015-03-01

    We present a case study of the tidal interaction between low-mass star-forming galaxies initially found in the Sloan Digital Sky Survey (SDSS) images and further analyzed with SDSS spectroscopy and UV GALEX photometry. With a luminosity of Mr = -17.7 mag and exhibiting a prominent tidal filament, UGC 6741 appears as a scaled down version of massive gas-rich interacting systems and mergers. The stellar disk of the smaller companion, UGC 6741_B, which is three times less massive, has likely already been destroyed. Both galaxies, which are connected by a 15 kpc long stellar bridge, have similar oxygen abundances of 12 +log(O/H)˜8.3. Several knots of star-forming regions are identified along the bridge, some with masses exceeding ˜107 M ⊙ . The most compact of them, which are unresolved, may evolve into globular clusters or ultra compact dwarf galaxies. This would be the first time progenitors of such objects are detected in mergers involving dwarf galaxies. UGC 6741 currently has the color and star formation properties of blue compact dwarf galaxies (BCDs). However, analysis of its surface photometry suggests that the galaxy lies within the scaling relations defined by early-type dwarf galaxies (dEs). Thus, UGC 6741 appears as a promising system for studying the possible transformation of BCDs into dEs, possibly through a merger episode. The frequency of such dwarf-dwarf mergers should now be explored.

  12. An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate.

    PubMed

    Gilfanov, Marat; Bogdán, Akos

    2010-02-18

    There is wide agreement that type Ia supernovae (used as standard candles for cosmology) are associated with the thermonuclear explosions of white dwarf stars. The nuclear runaway that leads to the explosion could start in a white dwarf gradually accumulating matter from a companion star until it reaches the Chandrasekhar limit, or could be triggered by the merger of two white dwarfs in a compact binary system. The X-ray signatures of these two possible paths are very different. Whereas no strong electromagnetic emission is expected in the merger scenario until shortly before the supernova, the white dwarf accreting material from the normal star becomes a source of copious X-rays for about 10(7) years before the explosion. This offers a means of determining which path dominates. Here we report that the observed X-ray flux from six nearby elliptical galaxies and galaxy bulges is a factor of approximately 30-50 less than predicted in the accretion scenario, based upon an estimate of the supernova rate from their K-band luminosities. We conclude that no more than about five per cent of type Ia supernovae in early-type galaxies can be produced by white dwarfs in accreting binary systems, unless their progenitors are much younger than the bulk of the stellar population in these galaxies, or explosions of sub-Chandrasekhar white dwarfs make a significant contribution to the supernova rate. PMID:20164924

  13. IMPACT OF TYPE Ia SUPERNOVA EJECTA ON BINARY COMPANIONS IN THE SINGLE-DEGENERATE SCENARIO

    SciTech Connect

    Pan, Kuo-Chuan; Ricker, Paul M.; Taam, Ronald E. E-mail: pmricker@illinois.edu

    2012-05-10

    Type Ia supernovae are thought to be caused by thermonuclear explosions of a carbon-oxygen white dwarf in close binary systems. In the single-degenerate scenario (SDS), the companion star is non-degenerate and can be significantly affected by the explosion. We explore this interaction by means of multi-dimensional adaptive mesh refinement simulations using the FLASH code. We consider several different companion types, including main-sequence-like stars (MS), red giants (RG), and helium stars (He). In addition, we include the symmetry-breaking effects of orbital motion, rotation of the non-degenerate star, and Roche-lobe overflow. A detailed study of a sub-grid model for Type Ia supernovae is also presented. We find that the dependence of the unbound stellar mass and kick velocity on the initial binary separation can be fitted by power-law relations. By using the tracer particles in FLASH, the process leading to the unbinding of matter is dominated by ablation, which has usually been neglected in past analytical studies. The level of Ni/Fe contamination of the companion that results from the passage of the supernova ejecta is found to be {approx}10{sup -5} M{sub Sun} for the MS star, {approx}10{sup -4} M{sub Sun} for the He star, and {approx}10{sup -8} M{sub Sun} for the RG. The spinning MS companion star loses about half of its initial angular momentum during the impact, causing the rotational velocity to drop to a quarter of the original rotational velocity, suggesting that the Tycho G star is a promising progenitor candidate in the SDS.

  14. The HST Snapshot Survey of Nearby Dwarf Galaxy Candidates. III. Resolved Dwarf Galaxies In and Beyond the Local Group

    NASA Astrophysics Data System (ADS)

    Grebel, E. K.; Seitzer, P.; Dolphin, A. E.; Geisler, D.; Guhathakurta, P.; Hodge, P. W.; Karachentsev, I. D.; Karachentseva, V. E.; Sarajedini, A.; Sharina, M. E.

    1999-12-01

    We present results for several nearby, resolved dwarf galaxies imaged with WFPC2 in the framework of our HST snapshot survey of nearby dwarf galaxy candidates (Seitzer et al., paper I in this series). All data presented here were analyzed with the automated photometry package HSTPHOT (Dolphin et al., paper IV in this series). Our closest target is the recently discovered Cassiopeia dwarf spheroidal (dSph) galaxy (Karachentsev & Karachentseva 1999, A&A, 341, 355), a new Local Group member and companion of M31 (Grebel & Guhathakurta 1999, ApJ, 511, 101). Our WFPC2 snapshot data reveal a pronounced red horizontal branch in Cas dSph. IC 5152 is a dwarf irregular (dIrr) just beyond the Local Group. Our data show a significant intermediate-age population with a strongly tilted asymptotic giant branch (AGB), a substantial young population, and a wide giant branch. Other nearby galaxies to be discussed include NGC 1560, ESO 471-G006, ESO 470-G018, and KK 035. Most of these galaxies are being resolved into stars for the first time. We describe their properties in detail and derive distances for all dwarfs with a well-defined tip of the red giant branch. Membership of these galaxies in nearby groups is discussed. Support for this work was provided by NASA through grant GO-08192.97A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. EKG acknowledges support by NASA through grant HF-01108.01-98A from the Space Telescope Science Institute. EKG and IDK are supported by the Henri Chrétien International Research Grant administered by the American Astronomical Society. PG is an Alfred P. Sloan Research Fellow.

  15. Potential Brown Dwarf-Planet System in the ~40 Myr Argus Association

    NASA Astrophysics Data System (ADS)

    Bardalez Gagliuffi, Daniella; Gagne, Jonathan; Faherty, Jackie; Burgasser, Adam J.

    2016-06-01

    Low-temperature L and T dwarfs in young moving groups are excellent proxies of giant exoplanet atmospheres, and allow us to probe the very lowest limits of the substellar initial mass function. We present a detailed spectral analysis of an L9 dwarf candidate member of the Argus young moving group, whose peculiar and unusually red spectrum suggests the presence of an unresolved, even lower temperature companion. Using the spectral binary technique, we are able to reproduce the shape of this peculiar spectrum, and using evolutionary models we infer that the component masses straddle the deuterium burning minimum mass limit, making this a candidate brown dwarf/giant planet system. This system is unique in that its secondary is one of only a few examples of a young T dwarf, and the discovery of this system implies that the spectral binary technique can probe companions down to planetary masses. High-resolution imaging and spectroscopy are still needed to confirm the multiplicity of this source.

  16. CARMENES. Multiplicity of M dwarfs from tenths of arcseconds to hundreds of arcminutes

    NASA Astrophysics Data System (ADS)

    Cortés-Contreras, M.; J. S. Béjar, V.; Caballero, J. A.; Gauza, B.; Montes, D.; Alonso-Floriano, F. J.; Ribas, I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.; CARMENES Consortium

    2015-05-01

    With the help of CARMENCITA, the CARMENES Cool dwarf Information and datA Archive, we investigate the multiplicity of M dwarfs in the solar neighnourhood observable from Calar Alto to prepare and characterize the final sample of stars of CARMENES. Our multiplicity study covers a wide range in projected physical separations, from 0.5 to 50 000 au. The inner range is covered with a lucky-imaging survey of 385 M dwarfs with FastCam at the 1.5 m Telescopio Carlos Sánchez (42.3 mas/pix), complemented with a literature search. We explore visual or physical companions from 0.15 to 18 arcsec around our targets. These observations are important to discard very close companions that may induce spurious variations in the radial velocity of the primary and mimic the presence of planets. The outer range is covered with a detailed analysis of Washington Double Stars catalogue data and optical images taken by us with TCP and CAMELOT at the 0.8 m IAC80 telescope, and an astrometric study of all-sky public images and catalogues. We review the main results of our searches and derive the multiplicity of M dwarfs at close and wide physical separations.

  17. DIRECT SPECTRUM OF THE BENCHMARK T DWARF HD 19467 B

    SciTech Connect

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

    2015-01-10

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

  18. Solidification of carbon-oxygen white dwarfs

    NASA Technical Reports Server (NTRS)

    Schatzman, E.

    1982-01-01

    The internal structure of white dwarfs is discussed. Highly correlated plasmas are reviewed. Implications for phase separation in the core of cooling white dwarfs are considered. The consequences for evolution of white dwarfs are addressed.

  19. Local Universe Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Carignan, Claude

    2015-08-01

    One of the outstanding problems in cosmology is addressing the "small-scale crisis" and understanding structure formation at the smallest scales. Standard Lambda Cold Dark Matter cosmological simulations of Milky Way-size DM halos predict many more DM sub-halos than the number of dwarf galaxies observed. This is the so-called Missing Satellites Problem. The most popular interpretation of the Missing Satellites Problem is that the smallest dark matter halos in the universe are extremely inefficient at forming stars. The virialized extent of the Milky Way's halo should contain ~500 satellites, while only ˜100 satellites and dwarfs are observed in the whole Local Group. Despite the large amount of theoretical work and new optical observations, the discrepancy, even if reduced, still persists between observations and hierarchical models, regardless of the model parameters. It may be possible to find those isolated ultra-faint missing dwarf galaxies via their neutral gas component, which is one of the goals we are pursuing with the SKA precursor KAT-7 in South Africa, and soon with the SKA pathfinder MeerKAT.

  20. Discovery of Seven Companions to Intermediate-mass Stars with Extreme Mass Ratios in the Scorpius-Centaurus Association

    NASA Astrophysics Data System (ADS)

    Hinkley, Sasha; Kraus, Adam L.; Ireland, Michael J.; Cheetham, Anthony; Carpenter, John M.; Tuthill, Peter; Lacour, Sylvestre; Evans, Thomas M.; Haubois, Xavier

    2015-06-01

    We report the detection of seven low-mass companions to intermediate-mass stars (SpT B/A/F; M ˜ 1.5-4.5 M⊙) in the Scorpius-Centaurus (Sco-Cen) Association using nonredundant aperture masking interferometry. Our newly detected objects have contrasts {Δ }L\\prime ≈ 4-6, corresponding to masses as low as ˜20 MJup and mass ratios of q ≈ 0.01-0.08, depending on the assumed age of the target stars. With projected separations ρ ≈ 10-30 AU, our aperture masking detections sample an orbital region previously unprobed by conventional adaptive optics imaging of intermediate-mass Sco-Cen stars covering much larger orbital radii (˜30-3000 AU). At such orbital separations, these objects resemble higher-mass versions of the directly imaged planetary mass companions to the 10-30 Myr, intermediate-mass stars HR 8799, β Pictoris, and HD 95086. These newly discovered companions span the brown dwarf desert, and their masses and orbital radii provide a new constraint on models of the formation of low-mass stellar and substellar companions to intermediate-mass stars. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory Under Program IDs: 0.87.C-0790 and 089.C-0605.

  1. Distances to WISE Y dwarfs

    NASA Astrophysics Data System (ADS)

    Beichman; A., C.; Gelino; R., C.; Kirkpatrick, J. Davy

    The WISE satellite has detected some of the coldest, lowest mass objects in the solar neighborhood. These late T and early Y dwarfs have effective temperatures in the range 250-800 K and inferred masses in the range 5-25 MJup. A critical piece of information for determining the physical properties of a brown dwarf is its distance, which greatly improves the comparison with evolutionary models. We discuss the importance of Y dwarfs in the context of star and planet formation. We also update our recent paper on Y dwarf parallaxes with improved values for four objects based on recent observations.

  2. Polaris: Amplitude, Period Change, and Companions

    NASA Astrophysics Data System (ADS)

    Evans, Nancy Remage; Sasselov, Dimitar D.; Short, C. Ian

    2002-03-01

    Polaris has presented us with the rare phenomenon of a Cepheid with a pulsation amplitude that has decreased over the last 50 yr. In this study we have used this property to see whether the amplitude decrease during the last 15 yr has had any effect on upper atmosphere heating. We obtained IUE high- and low-resolution spectra but found no change in either the Mg II chromospheric emission or the flux at 1800 Å between 1978 and 1993 when the pulsation amplitude dropped by 50% (from 2.8 to 1.6 km s-1). The energy distribution from 1700 Å through V, B, R(KC), and I(KC) is like that of a nonvariable supergiant of the same color rather than a full amplitude Cepheid in that it has more flux at 1800 Å than the full amplitude Cepheid δ Cep. Polaris also has a rapidly changing period (3.2 s yr-1), in common with other overtone pulsators. We argue that this is a natural consequence of the different envelope locations that dominate pulsation growth rates in fundamental and overtone pulsation. In fundamental mode pulsators, the deeper envelope is more important in determining growth rates than for overtone pulsators. For fundamental mode pulsators, evolutionary changes in the radius produce approximately linear changes in period. In overtone pulsators, pulsation reacts to small evolutionary changes in a more unstable way because the modes are more sensitive to high envelope features such as opacity bumps, and the growth rates for the many closely spaced overtone modes change easily. Finally, the upper limit to the X-ray flux from an Einstein observation implies that the companion in the astrometric orbit is earlier than F4 V. The combination of upper and lower limits on the companion from IUE and Einstein respectively catch the companion mass between 1.7 and 1.4 Msolar. The X-ray limit is consistent with the more distant companion α UMi B being a physical companion in a hierarchal triple system. However the X-ray limits require that the even more distant companions α UMi

  3. VizieR Online Data Catalog: White dwarf main-sequence binaries (Rebassa-Mansergas+, 2013)

    NASA Astrophysics Data System (ADS)

    Rebassa-Mansergas, A.; Agurto-Gangas, C.; Schreiber, M. R.; Gansicke, B. T.; Koester, D.

    2014-07-01

    The spectroscopic catalogue of white dwarf main-sequence (WDMS) binaries from the Sloan Digital Sky Survey (SDSS) is the largest and most homogeneous sample of compact binary stars currently known. However, because of selection effects, the current sample is strongly biased against systems containing cool white dwarfs and/or early-type companions, which are predicted to dominate the intrinsic population. In this study, we present colour selection criteria that combines optical (ugriz DR8 SDSS) plus infrared (yjhk DR9 UKIRT Infrared Sky Survey, JHK Two Micron All Sky Survey and/or W1W2 Wide-Field Infrared Survey Explorer) magnitudes to select 3419 photometric candidates of harbouring cool white dwarfs and/or dominant (M dwarf) companions. We demonstrate that 84 percent of our selected candidates are very likely genuine WDMS binaries, and that the white dwarf effective temperatures and secondary star spectral types of 71 percent of our selected sources are expected to be below <~10000-15000K, and concentrated at ~M2-3, respectively. We also present an updated version of the spectroscopic SDSS WDMS binary catalogue, which incorporates 47 new systems from SDSS DR8. The bulk of the DR8 spectroscopy is made up of main-sequence stars and red giants that were targeted as part of the Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey, therefore the number of new spectroscopic WDMS binaries in DR 8 is very small compared to previous SDSS data releases. Despite their low number, DR8 WDMS binaries are found to be dominated by systems containing cool white dwarfs and therefore represent an important addition to the spectroscopic sample. The updated SDSS DR8 spectroscopic catalogue of WDMS binaries consists of 2316 systems. We compare our updated catalogue with recently published lists of WDMS binaries and conclude that it currently represents the largest, most homogeneous and cleanest sample of spectroscopic WDMS binaries from SDSS. (5 data files).

  4. Peculiar variations of white dwarf pulsation frequencies and maestro

    NASA Astrophysics Data System (ADS)

    Dalessio, James Ruland

    In Part I we report on variations of the normal mode frequencies of the pulsating DB white dwarfs EC 20058-5234 and KIC 8626021 and the pulsating DA white dwarf GD 66. The observations of EC 20058-5234 and KIC 8626021 were motivated by the possibility of measuring the plasmon neutrino production rate of a white dwarf, while the observations of GD 66 were part of a white dwarf pulsation timing based planet search. We announce the discovery of periodic and quasi-periodic variations of multiple normal mode frequencies that cannot be due to the presence of planetary companions. We note the possible signature of a planetary companion to EC 20058-5234 and show that GD 66 cannot have a planet in a several AU orbit down to half a Jupiter mass. We also announce the discovery of secular variations of the normal mode frequencies of all three stars that are inconsistent with cooling alone. Importantly, the rates of period change of several modes of KIC 8626021 are consistent with evolutionary cooling, but are not yet statistically significant. These modes offer the best possibility of measuring the neutrino production rate in a white dwarf. We also observe periodic and secular variations in the frequency of a combination mode that exactly matches the variations predicted by the parent modes, strong observational evidence that combination modes are created by the convection zone and are not normal modes. Periodic variations in the amplitudes of many of these modes is also noted. We hypothesize that these frequency variations are caused by complex variations of the magnetic field strength and geometry, analogous to behavior observed in the Sun. In Part II we describe the MAESTRO software framework and the MAESTRO REDUCE algorithm. MAESTRO is a collection of astronomy specific MatLab software developed by the Whole Earth Telescope. REDUCE is an an algorithm that can extract the brightness of stars on a set of CCD images with minimal configuration and human interaction. The key to

  5. The Kepler eclipsing system KIC 5621294 and its substellar companion

    SciTech Connect

    Lee, Jae Woo; Hong, Kyeongsoo; Hinse, Tobias Cornelius E-mail: kshong@kasi.re.kr

    2015-03-01

    We present the physical properties of KIC 5621294, showing light and timing variations from the Kepler photometry. Its light curve displays partial eclipses and the O’Connell effect, with Max II fainter than Max I, which was fitted quite well by applying third-body and spot effects to the system. The results indicate that the eclipsing pair is a classical Algol-type system with parameters of q = 0.22, i = 76.°8, and Δ(T{sub 1}−T{sub 2}) = 4235 K, in which the detached primary component fills about 77% of its limiting lobe. Striking discrepancies exist between the primary and secondary eclipse times obtained with the method of Kwee and van Woerden. These are mainly caused by surface inhomogeneities due to spot activity detected in our light curve synthesis. The 1253 light curve timings from the Wilson–Devinney code were used for a period study. It was found that the orbital period of KIC 5621294 has varied due to periodic variation overlaid on a downward parabola. The sinusoidal variation with a period of 961 days and a semi-amplitude of 22.5 s most likely arises from a light-time effect due to a third component with a mass of M{sub 3}sini{sub 3} = 46.9 M{sub Jup}, which is in good agreement with that calculated from the light curve itself. If its orbital inclination is larger than about 40°, the mass of the circumbinary object would possibly match a brown dwarf. The parabolic variation could not be fully explained by either a mass transfer between the binary components or angular momentum via magnetic braking. It is possible that the parabola may be the only observed part of a period modulation caused by the presence of another companion in a wider orbit.

  6. Spectroscopic confirmation of young planetary-mass companions on wide orbits

    SciTech Connect

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

    2014-03-20

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

  7. Spectroscopic Confirmation of Young Planetary-mass Companions on Wide Orbits

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  8. Companion animals: Translational scientist's new best friends.

    PubMed

    Kol, Amir; Arzi, Boaz; Athanasiou, Kyriacos A; Farmer, Diana L; Nolta, Jan A; Rebhun, Robert B; Chen, Xinbin; Griffiths, Leigh G; Verstraete, Frank J M; Murphy, Christopher J; Borjesson, Dori L

    2015-10-01

    Knowledge and resources derived from veterinary medicine represent an underused resource that could serve as a bridge between data obtained from diseases models in laboratory animals and human clinical trials. Naturally occurring disease in companion animals that display the defining attributes of similar, if not identical, diseases in humans hold promise for providing predictive proof of concept in the evaluation of new therapeutics and devices. Here we outline comparative aspects of naturally occurring diseases in companion animals and discuss their current uses in translational medicine, benefits, and shortcomings. Last, we envision how these natural models of disease might ultimately decrease the failure rate in human clinical trials and accelerate the delivery of effective treatments to the human clinical market. PMID:26446953

  9. Observing Faint Companions Close to Bright Stars

    NASA Astrophysics Data System (ADS)

    Serabyn, Eugene

    2012-04-01

    Progress in a number of technical areas is enabling imaging and interferometric observations at both smaller angular separations from bright stars and at deeper relative contrast levels. Here we discuss recent progress in several ongoing projects at the Jet Propulsion Laboratory. First, extreme adaptive optics wavefront correction has recently enabled the use of very short (i.e., blue) wavelengths to resolve close binaries. Second, phase-based coronagraphy has recently allowed observations of faint companions to within nearly one diffraction beam width of bright stars. Finally, rotating interferometers that can observe inside the diffraction beam of single aperture telescopes are being developed to detect close-in companions and bright exozodiacal dust. This paper presents a very brief summary of the techniques involved, along with some illustrative results.

  10. Satellite dwarf galaxies in a hierarchical universe: the prevalence of dwarf-dwarf major mergers

    SciTech Connect

    Deason, Alis; Wetzel, Andrew; Garrison-Kimmel, Shea

    2014-10-20

    Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ∼10% of satellite dwarf galaxies with M {sub star} > 10{sup 6} M {sub ☉} that are within the host virial radius experienced a major merger of stellar mass ratio closer than 0.1 since z = 1, with a lower fraction for lower mass dwarf galaxies. Recent merger remnants are biased toward larger radial distance and more recent virial infall times, because most recent mergers occurred shortly before crossing within the virial radius of the host halo. Satellite-satellite mergers also occur within the host halo after virial infall, catalyzed by the large fraction of dwarf galaxies that fell in as part of a group. The merger fraction doubles for dwarf galaxies outside of the host virial radius, so the most distant dwarf galaxies in the Local Group are the most likely to have experienced a recent major merger. We discuss the implications of these results on observable dwarf merger remnants, their star formation histories, the gas content of mergers, and massive black holes in dwarf galaxies.

  11. The Evolution of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Dunn, Jacqueline M.

    2016-01-01

    Dwarf galaxies are the most numerous galaxies in the Universe, yet the driving forces in their evolution remain elusive. The proposed evolutionary link between dwarf irregular and dwarf elliptical/spheroidal galaxies is investigated using broad-band UBVR photometry obtained for a sample of 29 dwarf galaxies. The galaxies span a range of absolute B-band magnitude from -13.67 to -19.86 mag. Broad-band colors and Sérsic surface brightness profile fits are compared for the two morphological types. All optical parameters are statistically different between the two subsamples, as evidenced by the significance level of the Kolmogorov-Smirnov statistic.Others have noted that dwarf ellipticals might have looked much like the currently observed dwarf irregulars in the past based on optical colors. An overlap between in the range of colors observed is noted for these targets, implying the possibility of an evolutionary link. A difference is noted between the two samples in the value of n (the power-law exponent determined from the Sérsic profile fitting), suggesting that the two main types of dwarf galaxy are structurally distinct. The differences in the structure of the stellar components would imply that dwarf irregulars do not evolve to become dwarf ellipticals in isolation, meaning that some sort of external interaction is required if the transformation is to occur. However, when the brightest dwarf elliptical targets are eliminated from the comparison, the two dwarf samples are much more similar in their values and range for the power-law exponent, which again suggests a possible evolutionary link. The environments of the galaxies are initially classified as either field or group/cluster, though no definitive environmental comparison is presented here.

  12. The SOPHIE search for northern extrasolar planets. XI. Three new companions and an orbit update: Giant planets in the habitable zone

    NASA Astrophysics Data System (ADS)

    Díaz, R. F.; Rey, J.; Demangeon, O.; Hébrard, G.; Boisse, I.; Arnold, L.; Astudillo-Defru, N.; Beuzit, J.-L.; Bonfils, X.; Borgniet, S.; Bouchy, F.; Bourrier, V.; Courcol, B.; Deleuil, M.; Delfosse, X.; Ehrenreich, D.; Forveille, T.; Lagrange, A.-M.; Mayor, M.; Moutou, C.; Pepe, F.; Queloz, D.; Santerne, A.; Santos, N. C.; Sahlmann, J.; Ségransan, D.; Udry, S.; Wilson, P. A.

    2016-07-01

    We report the discovery of three new substellar companions to solar-type stars, HD 191806, HD 214823, and HD 221585, based on radial velocity measurements obtained at the Haute-Provence Observatory. Data from the SOPHIE spectrograph are combined with observations acquired with its predecessor, ELODIE, to detect and characterise the orbital parameters of three new gaseous giant and brown dwarf candidates. Additionally, we combine SOPHIE data with velocities obtained at the Lick Observatory to improve the parameters of an already known giant planet companion, HD 16175 b. Thanks to the use of different instruments, the data sets of all four targets span more than ten years. Zero-point offsets between instruments are dealt with using Bayesian priors to incorporate the information we possess on the SOPHIE/ELODIE offset based on previous studies. The reported companions have orbital periods between three and five years and minimum masses between 1.6 MJup and 19 MJup. Additionally, we find that the star HD 191806 is experiencing a secular acceleration of over 11 m s-1 per year, potentially due to an additional stellar or substellar companion. A search for the astrometric signature of these companions was carried out using Hipparcos data. No orbit was detected, but a significant upper limit to the companion mass can be set for HD 221585, whose companion must be substellar. With the exception of HD 191806 b, the companions are located within the habitable zone of their host star. Therefore, satellites orbiting these objects could be a propitious place for life to develop. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France by the SOPHIE Consortium (programme 07A.PNP.CONS to 15A.PNP.CONS).

  13. The Oxford Companion to the Earth

    NASA Astrophysics Data System (ADS)

    Hancock, Paul L.

    2001-06-01

    Here is a wealth of information on planet Earth, ranging from the heights of the ionsphere down to the red-hot molten core. Written by some 200 expert contributors, and illustrated with over 600 pictures, including 16 pages of color plates, The Oxford Companion to the Earth offers 900 alphabetically arranged entries that cover everything from deserts and wetlands to mountains, caves, glaciers, and coral reefs. There are articles on natural phenomena such as tornadoes and tsunamis, volcanoes and earthquakes, jet streams and weather fronts; on the history of Earth, including the origin of life, Burgess Shale fauna, dinosaurs, and the Ice Ages; on key figures, such as Agassiz, Cuvier, Darwin, and Lamarck; and on such important ecological concerns as acid rain, the ozone layer, industrial waste disposal, and the greenhouse effect. The Companion also examines the great sources of wealth to be found in the Earth, from coal and oil to gold, silver, and diamonds, and many curious land formations, from sinkholes and fiords to yardangs and quicksand. There are brief entries on rock types, from amber to travertine, and extensive essays on cutting-edge aspects of the earth sciences, such as seismology and marine geology. The Companion includes extensive cross-references, suggested further reading, an index, and many useful appendices, with a geological timescale, facts and figures about the Earth, and a table of chemical elements. The Oxford Companion to the Earth is a unique reference work, offering unrivaled coverage of our home planet. Generously illustrated and vividly written, it is a treasure house of information for all lovers of natural history, geology, and ecology, whether professional or amateur.

  14. Binary-binary collisions involving main-sequence stars, white dwarfs and neutron stars in globular clusters

    SciTech Connect

    Leonard, P.J.T.; Davies, M.B.

    1993-12-31

    We consider collisions between dynamically-evolved primordial binaries consisting of main-sequence stars, white dwarfs and neutron stars in globular clusters. In our four-body binary-binary scattering experiments, we allow stars to ``stick`` if they pass close enough to each other, which leads to the formation of a wide variety of exotic objects. Most of these objects have binary companions. Also, relatively clean exchange interactions can produce binaries containing neutron stars that eventually receive material from their companions. Such systems will be observable as X-ray binaries.

  15. Extension of Companion Modeling Using Classification Learning

    NASA Astrophysics Data System (ADS)

    Torii, Daisuke; Bousquet, François; Ishida, Toru

    Companion Modeling is a methodology of refining initial models for understanding reality through a role-playing game (RPG) and a multiagent simulation. In this research, we propose a novel agent model construction methodology in which classification learning is applied to the RPG log data in Companion Modeling. This methodology enables a systematic model construction that handles multi-parameters, independent of the modelers ability. There are three problems in applying classification learning to the RPG log data: 1) It is difficult to gather enough data for the number of features because the cost of gathering data is high. 2) Noise data can affect the learning results because the amount of data may be insufficient. 3) The learning results should be explained as a human decision making model and should be recognized by the expert as being the result that reflects reality. We realized an agent model construction system using the following two approaches: 1) Using a feature selction method, the feature subset that has the best prediction accuracy is identified. In this process, the important features chosen by the expert are always included. 2) The expert eliminates irrelevant features from the learning results after evaluating the learning model through a visualization of the results. Finally, using the RPG log data from the Companion Modeling of agricultural economics in northeastern Thailand, we confirm the capability of this methodology.

  16. Population synthesis of Be/white dwarf binaries in the Galaxy

    NASA Astrophysics Data System (ADS)

    Raguzova, N. V.

    2001-03-01

    Using the ``Scenario Machine'' (a numerical co-de that models the evolution of large ensembles of binary systems) we study the number and physical properties of binary Be stars with white dwarfs taking account of the compact object cooling and we discuss the ways of their formation. In our calculations we take into account the influence of tidal synchronization on the evolution of stars in a close binary. The synchronization time scale may be less than the life-time of a Be star on the main sequence after the first mass transfer. It has strong effects on the resulting number distribution of binary Be stars over orbital periods. In particular, it can explain the lack of short period Be binaries. According to our calculations the number of binary systems containing a Be star paired with a white dwarf in the Galaxy is very large - 70% of all Be stars formed as a result of binary evolution must have a white dwarf as a companion. Based on our calculations we conclude that the compact companion in these systems must have a high surface temperature. The number distribution over the surface temperature peaks at 2 104 K for all white dwarfs and at 4 104 K for white dwarfs paired with early-type Be stars (between B0 and B2). The registration of white dwarfs in such systems is hampered by the fact that the entire orbit of a white dwarf is embedded in the dense circumstellar envelope of the primary star (our calculations show that the majority of Be/WD systems have orbital periods less than one year) and all extreme-UV and soft X-ray photons of a compact companion are absorbed by the Be star envelope. The detection of a white dwarf is possible during the period when the Be star disc-like envelope is lacking by the detection of white dwarf extreme-UV and soft X-ray emission. This method of registration appears to be particularly promising for ``single'' early-type Be stars because in these systems the white dwarfs must have a very high surface temperature. However, the loss of

  17. L151-81A/B - A unique white dwarf binary with DB and DA components

    NASA Technical Reports Server (NTRS)

    Oswalt, Terry D.; Hintzen, Paul M.; Liebert, James W.; Sion, Edward M.

    1988-01-01

    Spectroscopic observations of the wide binary L151-81A/B reveal that both components are white dwarfs with spectral types DB3 and DA4, the first such binary identified in a comprehensive survey of Luyten and Giclas common proper motion pairs. Assuming log g = 8, measurements of the helium line profiles in the DB primary yield Teff = 16,000 + or - 2,000, while the hydrogen profiles for the DA companion yield Teff =12,000 + or - 2,000. The existence of a helium-rich/hydrogen-rich degenerate pair offers several interesting tests of theoretical white dwarf formation channels and surface abundance evolution.

  18. The H I chronicles of LITTLE THINGS blue compact dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Ashley, Trisha Lynn

    Star formation occurs when the gas (mostly atomic hydrogen; H I) in a galaxy becomes disturbed, forming regions of high density gas, which then collapses to form stars. In dwarf galaxies it is still uncertain which processes contribute to star formation and how much they contribute to star formation. Blue compact dwarf (BCD) galaxies are low mass, low shear, gas rich galaxies that have high star formation rates when compared to other dwarf galaxies. What triggers the dense burst of star formation in BCDs but not other dwarfs is not well understood. It is often suggested that BCDs may have their starburst triggered by gravitational interactions with other galaxies, dwarf-dwarf galaxy mergers, or consumption of intergalactic gas. However, there are BCDs that appear isolated with respect to other galaxies, making an external disturbance unlikely. Here, I study six apparently isolated BCDs from the LITTLE THINGS sample in an attempt to understand what has triggered their burst of star formation. LITTLE THINGS is an H I survey of 41 dwarf galaxies. Each galaxy has high angular and velocity resolution H I data from the Very Large Array (VLA) telescope and ancillary stellar data. I use these data to study the detailed morphology and kinematics of each galaxy, looking for signatures of starburst triggers. In addition to the VLA data, I have collected Green Bank Telescope data for the six BCDs. These high sensitivity, low resolution data are used to search the surrounding area of each galaxy for extended emission and possible nearby companion galaxies. The VLA data show evidence that each BCD has likely experienced some form of external disturbance despite their apparent isolation. These external disturbances potentially seen in the sample include: ongoing/advanced dwarf-dwarf mergers, an interaction with an unknown external object, and external gas consumption. The GBT data result in no nearby, separate H I companions at the sensitivity of the data. These data therefore

  19. Kinematics of faint white dwarfs.

    PubMed

    Luyten, W J

    1978-10-01

    An analysis has been made for solar motion for 128 very faint white dwarfs of color class b or a. While about 40% of these stars may be high-velocity objects, it seems definitely indicated that the luminosity of all of them is considerably lower than that for the "normal" white dwarf of the same color. PMID:16592566

  20. Testing gravity using dwarf stars

    NASA Astrophysics Data System (ADS)

    Sakstein, Jeremy

    2015-12-01

    Generic scalar-tensor theories of gravity predict deviations from Newtonian physics inside astrophysical bodies. In this paper, we point out that low mass stellar objects, red and brown dwarf stars, are excellent probes of these theories. We calculate two important and potentially observable quantities: the radius of brown dwarfs and the minimum mass for hydrogen burning in red dwarfs. The brown dwarf radius can differ significantly from the general relativity prediction, and upcoming surveys that probe the mass-radius relation for stars with masses dwarf stars. This places a new and extremely stringent constraint on the parameters that appear in the effective field theory of dark energy and rules out several well-studied dark energy models.

  1. Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Lumninous Infrared Galaxy Candidates

    NASA Technical Reports Server (NTRS)

    Griffith, Roger L.; Kirkpatrick, J. Davy; Eisenhardt, Peter R. M.; Gelino, Christopher R.; Cushing, Michael C.; Benford, Dominic; Blain, Andrew; Bridge, Carrie R.; Cohen, Martin; Cutri, Roc M.; Donoso, Emilio; Jarrett, Thomas H.; Lonsdale, Carol; Mace, Gregory; Mainzer, A.; Marsh, Ken; Padgett, Deborah; Petty, Sara; Ressler, Michael E.; Skrutskie, Michael F.; Stanford, Spencer A.; Stern, Daniel; Tsai, Chao-Wei; Wright, Edward L.; Wu, Jingwen

    2012-01-01

    We present Spitzer 3.6 and 4.5 micrometer photometry and positions for a sample of 1510 brown dwarf candidates identified by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12). Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify seven fainter (4.5 m to approximately 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy candidates. For this control sample, we find another six brown dwarf candidates, suggesting that the seven companion candidates are not physically associated. In fact, only one of these seven Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this, there is no evidence for any widely separated (greater than 20 AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of 7.33 x 10(exp 5) objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5 m photometry, along with positionally matched B and R photometry from USNO-B; J, H, and Ks photometry from Two Micron All-Sky Survey; and W1, W2, W3, and W4 photometry from the WISE all-sky catalog.

  2. Dwarfs in Coma Cluster

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version

    This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.

  3. Seeing Baby Dwarf Galaxies

    NASA Technical Reports Server (NTRS)

    2009-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Visible/DSS Click on image for larger version Ultraviolet/GALEX Click on image for larger version Poster Version Click on image for larger version

    The unique ultraviolet vision of NASA's Galaxy Evolution Explorer reveals, for the first time, dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way.

    The forming dwarf galaxies shine in the far ultraviolet spectrum, rendered as blue in the call-out on the right hand side of this image. Near ultraviolet light, also obtained by the Galaxy Evolution Explorer, is displayed in green, and visible light from the blue part of the spectrum here is represented by red. The clumps (in circles) are distinctively blue, indicating they are primarily detected in far ultraviolet light.

    The faint blue overlay traces the outline of the Leo Ring, a huge cloud of hydrogen and helium that orbits around two massive galaxies in the constellation Leo (left panel). The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light.

    Only a portion of the Leo Ring has been imaged in the ultraviolet, but this section contains the telltale ultraviolet signature of recent massive star formation within this ring of pristine gas. Astronomers have previously only seen dwarf galaxies form out of gas that has already been cycled through a galaxy and enriched with metals elements heavier than helium produced as stars evolve.

    The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md. The

  4. Barley yellow dwarf viruses.

    PubMed

    Miller, W A; Rasochová, L

    1997-01-01

    Barley yellow dwarf viruses represent one of the most economically important and ubiquitous groups of plant viruses. This review focuses primarily on four research areas in which progress has been most rapid. These include (a) evidence supporting reclassification of BYDVs into two genera; (b) elucidation of gene function and novel mechanisms controlling gene expression; (c) initial forays into understanding the complex interactions between BYDV virions and their aphid vectors; and (d) replication of a BYDV satellite RNA. Economic losses, symptomatology, and means of control of BYD are also discussed. PMID:15012520

  5. The Holistic Evolution of Dwarf Galaxies: Internal and External Processes in NGC 6822

    NASA Astrophysics Data System (ADS)

    Cannon, John

    2010-09-01

    Low-mass galaxy evolution is driven by both internal {e.g., star formation and feedback} and external {e.g., tidal interaction} processes; however, few nearby systems show evidence of both mechanisms operating in tandem. The Local Group dwarf galaxy NGC 6822 presents a unique opportunity to study important evolutionary processes because of proximity and timing: it harbors one of the largest known holes in its neutral ISM {a signpost of violent stellar feedback}, and it appears to be undergoing a tidal interaction with a very low mass companion dwarf galaxy. To capitalize on this opportunity, we propose to undertake an ACS and WFC3 imaging study of the stellar populations throughout NGC 6822. We will study the role of both internal and external processes by sampling the stellar populations associated with the main body {using archival WFPC2 data}, the giant HI hole, the companion dwarf galaxy, and the tidal material at the ends of the disk. From these data we will extract precise color magnitude diagrams; we will measure the full 13 Gyr star formation history of each field, with high time resolution {20-250 Myr} over the past 1 Gyr, and quantify the relative contributions of internal and external drivers of dwarf galaxy evolution. Specifically, we will study: 1} the nature of the companion object {differentiating between infalling gas and a genuine low-mass galaxy}; 2} the energetics of giant HI hole creation; 3} the role of interactions in the system's evolution; 4} the nature of feedback in governing the star formation process; and 5} the patterns of star formation over time. We have optimized our field placements to extract the most information possible about the competing forces that drive galaxy evolution; in only six orbits, we will gain fundamental insights into the contributions of both internal and external processes that bear on the evolution of low-mass galaxies.

  6. Discovery of Nearest Known Brown Dwarf

    NASA Astrophysics Data System (ADS)

    2003-01-01

    Bright Southern Star Epsilon Indi Has Cool, Substellar Companion [1] Summary A team of European astronomers [2] has discovered a Brown Dwarf object (a 'failed' star) less than 12 light-years from the Sun. It is the nearest yet known. Now designated Epsilon Indi B, it is a companion to a well-known bright star in the southern sky, Epsilon Indi (now "Epsilon Indi A"), previously thought to be single. The binary system is one of the twenty nearest stellar systems to the Sun. The brown dwarf was discovered from the comparatively rapid motion across the sky which it shares with its brighter companion : the pair move a full lunar diameter in less than 400 years. It was first identified using digitised archival photographic plates from the SuperCOSMOS Sky Surveys (SSS) and confirmed using data from the Two Micron All Sky Survey (2MASS). Follow-up observations with the near-infrared sensitive SOFI instrument on the ESO 3.5-m New Technology Telescope (NTT) at the La Silla Observatory confirmed its nature and has allowed measurements of its physical properties. Epsilon Indi B has a mass just 45 times that of Jupiter, the largest planet in the Solar System, and a surface temperature of only 1000 °C. It belongs to the so-called 'T dwarf' category of objects which straddle the domain between stars and giant planets. Epsilon Indi B is the nearest and brightest T dwarf known. Future studies of the new object promise to provide astronomers with important new clues as to the formation and evolution of these exotic celestial bodies, at the same time yielding interesting insights into the border zone between planets and stars. TINY MOVING NEEDLES IN GIANT HAYSTACKS ESO PR Photo 03a/03 ESO PR Photo 03a/03 [Preview - JPEG: 400 x 605 pix - 92k [Normal - JPEG: 1200 x 1815 pix - 1.0M] Caption: PR Photo 03a/03 shows Epsilon Indi A (the bright star at far right) and its newly discovered brown dwarf companion Epsilon Indi B (circled). The upper image comes from one of the SuperCOSMOS Sky

  7. THE DISCOVERY OF BINARY WHITE DWARFS THAT WILL MERGE WITHIN 500 Myr

    SciTech Connect

    Kilic, Mukremin; Brown, Warren R.; Kenyon, S. J.; Allende Prieto, Carlos; Panei, J. A.

    2010-06-10

    We present radial velocity observations of four extremely low-mass (0.2 M {sub sun}) white dwarfs (WDs). All four stars show peak-to-peak radial velocity variations of 540-710 km s{sup -1} with 1.0-5.9 hr periods. The optical photometry rules out main-sequence companions. In addition, no millisecond pulsar companions are detected in radio observations. Thus, the invisible companions are most likely WDs. Two of the systems are the shortest period binary WDs yet discovered. Due to the loss of angular momentum through gravitational radiation, three of the systems will merge within 500 Myr. The remaining system will merge within a Hubble time. The mass functions for three of the systems imply companions more massive than 0.46 M {sub sun}; thus, those are carbon/oxygen core WDs. The unknown inclination angles prohibit a definitive conclusion about the future of these systems. However, the chance of a supernova Ia event is only 1%-5%. These systems are likely to form single R Coronae Borealis stars, providing evidence for a WD + WD merger mechanism for these unusual objects. One of the systems, SDSS J105353.89+520031.0, has a 70% chance of having a low-mass WD companion. This system will probably form a single helium-enriched subdwarf O star. All four WD systems have unusual mass ratios of {<=}0.2-0.8 that may also lead to the formation of AM CVn systems.

  8. Star Formation and Tidal Encounters with the Low Surface Brightness Galaxy UGC 12695 and Companions

    NASA Astrophysics Data System (ADS)

    O'Neil, K.; Verheijen, M. A. W.; McGaugh, S. S.

    2000-05-01

    We present VLA H I observations of the low surface brightness (LSB) galaxy UGC 12695 and its two companions, UGC 12687 and a newly discovered dwarf galaxy 2333+1234. UGC 12695 shows solid-body rotation but has a very lopsided morphology of the H I disk, with the majority of the H I lying in the southern arm of the galaxy. The H I column density distribution of this very blue LSB galaxy coincides in detail with its light distribution. Comparing the H I column density of UGC 12695 with the empirical (but not well-understood) value of Σc=1021 atoms cm-2 found in, e.g., Skillman's 1987 paper shows the star formation to be a local affair, occurring only in those regions where the column density is above this star formation threshold. The low surface brightness nature of this galaxy could thus be attributed to an insufficient gas surface density, inhibiting star formation on a more global scale. Significantly, however, the Toomre criterion places a much lower critical density on the galaxy (~1020 atoms cm-2), which is shown by the galaxy's low star formation rate not to be applicable. Within a projected distance of 300 kpc/30 km s-1 of UGC 12695 lie two companion galaxies-UGC 12687, a high surface brightness barred spiral galaxy, and 2333+1234, a dwarf galaxy discovered during this investigation. The close proximity of the three galaxies, combined with UGC 12695's extremely blue color and regions of localized starburst and UGC 12687's UV, excess bring to mind mutually induced star formation through tidal activity.

  9. THE CORONAL ABUNDANCES OF MID-F DWARFS

    SciTech Connect

    Wood, Brian E.; Laming, J. Martin

    2013-05-10

    A Chandra spectrum of the moderately active nearby F6 V star {pi}{sup 3} Ori is used to study the coronal properties of mid-F dwarfs. We find that {pi}{sup 3} Ori's coronal emission measure distribution is very similar to those of moderately active G and K dwarfs, with an emission measure peak near log T = 6.6 seeming to be ubiquitous for such stars. In contrast to coronal temperature, coronal abundances are known to depend on spectral type for main sequence stars. Based on this previously known relation, we expected {pi}{sup 3} Ori's corona to exhibit an extremely strong ''first ionization potential (FIP) effect'', a phenomenon first identified on the Sun where elements with low FIP are enhanced in the corona. We instead find that {pi}{sup 3} Ori's corona exhibits a FIP effect essentially identical to that of the Sun and other early G dwarfs, perhaps indicating that the increase in FIP bias toward earlier spectral types stops or at least slows for F stars. We find that {pi}{sup 3} Ori's coronal characteristics are significantly different from two previously studied mid-F stars, Procyon (F5 IV-V) and {tau} Boo (F7 V). We believe {pi}{sup 3} Ori is more representative of the coronal characteristics of mid-F dwarfs, with Procyon being different because of luminosity class, and {tau} Boo being different because of the effects of one of two close companions, one stellar ({tau} Boo B: M2 V) and one planetary.

  10. Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. I. A Low-mass Ratio Stellar Companion to TYC 4110-01037-1 in a 79 Day Orbit

    NASA Astrophysics Data System (ADS)

    Wisniewski, John P.; Ge, Jian; Crepp, Justin R.; De Lee, Nathan; Eastman, Jason; Esposito, Massimiliano; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; Gonzalez Hernandez, Jonay I.; Lee, Brian L.; Stassun, Keivan G.; Agol, Eric; Allende Prieto, Carlos; Barnes, Rory; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Da Costa, Luiz N.; Porto De Mello, G. F.; Femenía, Bruno; Ferreira, Leticia D.; Gary, Bruce; Hebb, Leslie; Holtzman, Jon; Liu, Jian; Ma, Bo; Mack, Claude E.; Mahadevan, Suvrath; Maia, Marcio A. G.; Nguyen, Duy Cuong; Ogando, Ricardo L. C.; Oravetz, Daniel J.; Paegert, Martin; Pan, Kaike; Pepper, Joshua; Rebolo, Rafael; Santiago, Basilio; Schneider, Donald P.; Shelden, Alaina C.; Simmons, Audrey; Tofflemire, Benjamin M.; Wan, Xiaoke; Wang, Ji; Zhao, Bo

    2012-05-01

    TYC 4110-01037-1 has a low-mass stellar companion, whose small mass ratio and short orbital period are atypical among binary systems with solar-like (T eff <~ 6000 K) primary stars. Our analysis of TYC 4110-01037-1 reveals it to be a moderately aged (lsim5 Gyr) solar-like star having a mass of 1.07 ± 0.08 M ⊙ and radius of 0.99 ± 0.18 R ⊙. We analyze 32 radial velocity (RV) measurements from the SDSS-III MARVELS survey as well as 6 supporting RV measurements from the SARG spectrograph on the 3.6 m Telescopio Nazionale Galileo telescope obtained over a period of ~2 years. The best Keplerian orbital fit parameters were found to have a period of 78.994 ± 0.012 days, an eccentricity of 0.1095 ± 0.0023, and a semi-amplitude of 4199 ± 11 m s-1. We determine the minimum companion mass (if sin i = 1) to be 97.7 ± 5.8 M Jup. The system's companion to host star mass ratio, >=0.087 ± 0.003, places it at the lowest end of observed values for short period stellar companions to solar-like (T eff <~ 6000 K) stars. One possible way to create such a system would be if a triple-component stellar multiple broke up into a short period, low q binary during the cluster dispersal phase of its lifetime. A candidate tertiary body has been identified in the system via single-epoch, high contrast imagery. If this object is confirmed to be comoving, we estimate it would be a dM4 star. We present these results in the context of our larger-scale effort to constrain the statistics of low-mass stellar and brown dwarf companions to FGK-type stars via the MARVELS survey.

  11. Orbit of a Giant and a Dwarf

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-11-01

    The binary system Procyon, located a mere 11 light-years away, consists of a bright, subgiant star and a faint white dwarf presenting a distinct challenge for astronomers to observe. But careful analysis of two decades of precise measurements with the Hubble Space Telescope has now finally revealed some of its secrets.Challenging ObservationsPerturbations were detected as early as 1844 in the orbit of Procyon, originally thought to be a single star. Astronomers of the time suspected that this wobbling was due to the pull of a companion orbiting Procyon, but it wasnt until five decades later that the companion was first detected visually.Why? Because the subgiant Procyon A is the 8th brightest star in the sky. Its companion, on the other hand, is a white dwarf thats fainter (in visual wavelengths) by a factor of nearly 16,000! And the two stars are separated by an angular distance of less than 5.Due to the difficulty observing the system, the measurements of its motion and resulting estimates of the masses of the two stars have been a subject of debate for the better part of the last century.Led by Howard Bond (Pennsylvania State University and the Space Telescope Science Institute), a team of astronomers has now analyzed two decades of Hubble observations of the system, combined with historical, ground-based observations dating back to the 19th century. Bond and collaborators used these data to precisely measure the orbital elements of Procyon and obtain dynamical masses of the two stars.Surprising MixingRelative orbit of Procyon B around Procyon A. The red curve is the authors fit to the orbit, and the open blue circles are positions predicted by the orbital elements found. The black dots are the HST observations of Procyon B. The open green and turquoise circles are the (significantly less precise!) historical, ground-based observations. [Bond et al. 2015]The team reports that this system orbits once every 40.8 years. They find masses for the two stars of 1

  12. White Dwarf Stars

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Peering deep inside a cluster of several hundred thousand stars, NASA's Hubble Space Telescope has uncovered the oldest burned-out stars in our Milky Way Galaxy, giving astronomers a fresh reading on the age of the universe.

    Located in the globular cluster M4, these small, burned-out stars -- called white dwarfs -- are about 12 to 13 billion years old. By adding the one billion years it took the cluster to form after the Big Bang, astronomers found that the age of the white dwarfs agrees with previous estimates that the universe is 13 to 14 billion years old.

    The images, including some taken by Hubble's Wide Field and Planetary Camera 2, are available online at

    http://oposite.stsci.edu/pubinfo/pr/2002/10/ or

    http://www.jpl.nasa.gov/images/wfpc .

    The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    In the top panel, a ground-based observatory snapped a panoramic view of the entire cluster, which contains several hundred thousand stars within a volume of 10 to 30 light-years across. The Kitt Peak National Observatory's .9-meter telescope took this picture in March 1995. The box at left indicates the region observed by the Hubble telescope.

    The Hubble telescope studied a small region of the cluster. A section of that region is seen in the picture at bottom left. A sampling of an even smaller region is shown at bottom right. This region is only about one light-year across. In this smaller region, Hubble pinpointed a number of faint white dwarfs. The blue circles indicate the dwarfs. It took nearly eight days of exposure time over a 67-day period to find these extremely faint stars.

    Globular clusters are among the oldest clusters of stars in the universe. The faintest and coolest white dwarfs within globular clusters can yield a globular cluster's age. Earlier Hubble observations showed that the first stars formed less than 1 billion years after the universe's birth in the big bang. So, finding the

  13. DIRECT IMAGING AND SPECTROSCOPY OF A CANDIDATE COMPANION BELOW/NEAR THE DEUTERIUM-BURNING LIMIT IN THE YOUNG BINARY STAR SYSTEM, ROXs 42B

    SciTech Connect

    Currie, Thayne; Daemgen, Sebastian; Jayawardhana, Ray; Debes, John; Lafreniere, David; Itoh, Yoichi; Ratzka, Thorsten; Correia, Serge

    2014-01-10

    We present near-infrared high-contrast imaging photometry and integral field spectroscopy of ROXs 42B, a binary M0 member of the 1-3 Myr old ρ Ophiuchus star-forming region, from data collected over 7 years. Each data set reveals a faint companion—ROXs 42Bb—located ∼1.''16 (r {sub proj} ≈ 150 AU) from the primaries at a position angle consistent with a point source identified earlier by Ratzka et al.. ROXs 42Bb's astrometry is inconsistent with a background star but consistent with a bound companion, possibly one with detected orbital motion. The most recent data set reveals a second candidate companion at ∼0.''5 of roughly equal brightness, though preliminary analysis indicates it is a background object. ROXs 42Bb's H and K{sub s} band photometry is similar to dusty/cloudy young, low-mass late M/early L dwarfs. K band VLT/SINFONI spectroscopy shows ROXs 42Bb to be a cool substellar object (M8-L0; T {sub eff} ≈ 1800-2600 K), not a background dwarf star, with a spectral shape indicative of young, low surface gravity planet-mass companions. We estimate ROXs 42Bb's mass to be 6-15 M{sub J} , either below the deuterium-burning limit and thus planet mass or straddling the deuterium-burning limit nominally separating planet-mass companions from other substellar objects. Given ROXs 42b's projected separation and mass with respect to the primaries, it may represent the lowest mass objects formed like binary stars or a class of planet-mass objects formed by protostellar disk fragmentation/disk instability, the latter slightly blurring the distinction between non-deuterium-burning planets like HR 8799 bcde and low-mass, deuterium-burning brown dwarfs.

  14. Near-infrared imaging of white dwarfs with candidate debris disks

    SciTech Connect

    Wang, Zhongxiang; Tziamtzis, Anestis; Wang, Xuebing

    2014-02-10

    We have carried out JHK{sub s} imaging of 12 white dwarf debris disk candidates from the WIRED Sloan Digital Sky Survey Data Release 7 catalog, aiming to confirm or rule out disks among these sources. On the basis of positional identification and the flux density spectra, we find that seven white dwarfs have excess infrared emission, but mostly at Wide-field Infrared Survey Explorer W1 and W2 bands. Four are due to nearby red objects consistent with background galaxies or very low mass dwarfs, and one exhibits excess emission at JHK{sub s} consistent with an unresolved L0 companion at the correct distance. While our photometry is not inconsistent with all seven excesses arising from disks, the stellar properties are distinct from the known population of debris disk white dwarfs, making the possibility questionable. In order to further investigate the nature of these infrared sources, warm Spitzer imaging is needed, which may help resolve galaxies from the white dwarfs and provide more accurate flux measurements.

  15. The BANYAN All-Sky Survey for Brown Dwarf Members of Young Moving Groups

    NASA Astrophysics Data System (ADS)

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Faherty, Jacqueline K.; Malo, Lison; Cruz, Kelle L.; Artigau, Étienne; Burgasser, Adam J.; Naud, Marie-Eve; Bouchard, Sandie; Gizis, John E.; Albert, Loïc

    2016-01-01

    We describe in this work the BASS survey for brown dwarfs in young moving groups of the solar neighborhood, and summarize the results that it generated. These include the discovery of the 2MASS J01033563-5515561 (AB)b and 2MASS J02192210-3925225 B young companions near the deuterium-burning limit as well as 44 new low-mass stars and 69 new brown dwarfs with a spectroscopically confirmed low gravity. Among those, ~20 have estimated masses within the planetary regime, one is a new L4 γ bona fide member of AB Doradus, three are TW Hydrae candidates with later spectral types (L1-L4) than all of its previously known members and six are among the first contenders for low-gravity >= L5 β/γ brown dwarfs, reminiscent of WISEP J004701.06+680352.1, PSO J318.5338-22.8603 and VHS J125601.92-125723.9 b. Finally, we describe a future version of this survey, BASS-Ultracool, that will specifically target >= L5 candidate members of young moving groups. First experimentations in designing the survey have already led to the discovery of a new T dwarf bona fide member of AB Doradus, as well as the serendipitous discoveries of an L9 subdwarf and an L5 + T5 brown dwarf binary.

  16. Limits from the Ongoing Search for Planets Around White Dwarf Stars Using Pulsation Timings

    NASA Astrophysics Data System (ADS)

    Winget, D. E.; Hermes, J. J.; Mullally, Fergal; Bell, K. J.; Montgomery, M. H.; Williams, S. G.; Harrold, S. T.; Kepler, S. O.; Castanheira, B.; Chandler, D. W.; Winget, K. I.; Mukadam, A. S.; Nather, R. E.

    2015-06-01

    Evidence from searches of stars in our galaxy for exoplanet companions suggests that most lower main sequence stars likely have one or more planets; the vast majority of these planet-hosting stars will evolve into white dwarf stars. Some planets may survive this process and new ones may form in a sort of second generation from the cast-off material. If we combine this argument with evidence of a substantial population of metal polluted white dwarf stars, we may plausibly expect that planets may be common around white dwarf stars. Empirically, however, little is known about the presence of planets, new or old around white dwarf stars. Our search is small (˜15 white dwarf stars), but sensitive. Using pulsation arrival times we reach a large search volume around each star: we are sensitive to 1 MJupiter planets at distances ranging from 1- 100AU. In this context, our tightening constraints from pulsation timings become increasingly important to the broader study of planet formation, dynamical evolution, and ultimate survival.

  17. Indications of M-Dwarf Deficits in the Halo and Thick Disk of the Galaxy

    NASA Technical Reports Server (NTRS)

    Konishi, Mihoko; Shibai, Hiroshi; Sumi, Takahiro; Fukagawa, Misato; Matsuo, Taro; Samland, Matthias S.; Yamamoto, Kodai; Sudo, Jun; Itoh, Yoichi; Arimoto, Nubuo; Kajisawa, Masaru; Lyu, Abe; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Oliver, Guyon; Hashimoto, Jun; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R.; Kudo,Tomoyuki; Kusakabe, Nobuhiko; Kwon, Jungmi; McElwain, Michael W.

    2014-01-01

    We compared the number of faint stars detected in deep survey fields with the current stellar distribution model of the Galaxy and found that the detected number in the H band is significantly smaller than the predicted number. This indicates that M-dwarfs, the major component, are fewer in the halo and the thick disk. We used archived data of several surveys in both the north and south field of GOODS (Great Observatories Origins Deep Survey), MODS in GOODS-N, and ERS and CANDELS in GOODS-S. The number density of M-dwarfs in the halo has to be 20 +/- 13% relative to that in the solar vicinity, in order for the detected number of stars fainter than 20.5 mag in the H band to match with the predicted value from the model. In the thick disk, the number density of M-dwarfs must be reduced (52 +/- 13%) or the scale height must be decreased (approximately 600 pc). Alternatively, overall fractions of the halo and thick disks can be significantly reduced to achieve the same effect, because our sample mainly consists of faint M-dwarfs. Our results imply that the M-dwarf population in regions distant from the Galactic plane is significantly smaller than previously thought. We then discussed the implications this has on the suitability of the model predictions for the prediction of non-companion faint stars in direct imaging extrasolar planet surveys by using the best-fit number densities.

  18. Indications of M-Dwarf Deficits in the Halo and Thick Disk of the Galaxy

    NASA Technical Reports Server (NTRS)

    Konishi, Mihoko; Shibai, Hiroshi; Sumi, Takahiro; Fukagawa, Misato; Matsuo, Taro; Samland, Matthias S.; Yamamoto, Kodai; Sudo, Jun; Itoh, Yoichi; Arimoto, Nobuo; Kajisawa, Masaru; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Feldt, Marcus; Goto, Miwa; Grady, Carol A.; Guyon, Oliver; Hashimoto, Jun; Hayano, Yutaka; Hayashi, Masahiko; McElwain, Michael W.

    2014-01-01

    We compared the number of faint stars detected in deep survey fields with the current stellar distribution model of the Galaxy and found that the detected number in the H band is significantly smaller than the predicted number. This indicates that M-dwarfs, the major component, are fewer in the halo and the thick disk. We used archived data of several surveys in both the north and south field of GOODS (Great Observatories Origins Deep Survey), MODS in GOODS-N, and ERS and CANDELS in GOODS-S. The number density of M-dwarfs in the halo has to be 20+/-13% relative to that in the solar vicinity, in order for the detected number of stars fainter than 20.5 mag in the H band to match with the predicted value from the model. In the thick disk, the number density of M-dwarfs must be reduced (52+/-13%) or the scale height must be decreased ( approx. 600 pc). Alternatively, overall fractions of the halo and thick disks can be significantly reduced to achieve the same effect, because our sample mainly consists of faint M-dwarfs. Our results imply that the M-dwarf population in regions distant from the Galactic plane is significantly smaller than previously thought. We then discussed the implications this has on the suitability of the model predictions for the prediction of non-companion faint stars in direct imaging extrasolar planet surveys by using the best-fit number densities.

  19. A Near-Infrared Search for Very Low Mass Companions to Stars within 10 pc of the Sun

    NASA Astrophysics Data System (ADS)

    Golimowski, David

    1997-07-01

    Most stars are fainter and less massive than the Sun. Nevertheless, the luminosity function {LF} and mass-luminosity relation {MLR} for very-low- mass {VLM} stars {M < 0.2 Msun} remain poorly constrained. The best way to constrain these relations is a search for faint companions to nearby stars. Such a search has several advantages over field surveys, the most important of which are greater sensitivity to VLM objects and the availability of pre- cise parallaxes from which absolute luminosities and dynamic masses can be obtained. We propose a NICMOS snapshot search for VLM companions to 120 single stars within 10 pc of the Sun. This search will probe the previously unexplored circumstellar region lying between the search spaces of speckle searches {1-10 AU} and deep imaging searches {100-1000 AU}. With a 10 sigma detection limit of M_J 21.5 at 10 pc, we will detect objects at least 10 mag fainter than the empirical end of the main sequence and at least 6 mag fainter than the brown dwarf Gl 229B. Our ultimate goal is the largest, most sensitive, volume-limited search for VLM companions ever un- dertaken. The four colors selected for the search will permit unambiguous identification of VLM-companion candidates for follow-up observation. To- gether with the IR speckle and deep imaging surveys, our program will firmly establish both the LF for VLM companions at separations of 1-1000 AU and the multiplicity fraction of all stars within 10 pc.

  20. Companion Cases in a Large Urban Medical Examiner's Office.

    PubMed

    Hlavaty, Leigh; Njiwaji, Chantel; Sung, LokMan

    2015-12-01

    Companion death cases, as defined in this study, include 2 or more deaths that occur at the same location or 1 death at a specific location combined with 1 or more individuals transported from that same location to a hospital where death was pronounced within 1 hour of arrival. These types of cases can have multiple causes and manners of death. The Wayne County Medical Examiner's Office conducted a retrospective study of companion death cases that came into the office from mid 2007 to the end of 2014. The purpose of the study was to identify and examine patterns of companion death cases in a large urban area that would assist future companion death case investigations. Three hundred fifty deaths were found to be companion cases, including 135 pairs (2 connected deaths in the same location), 20 trios, and 5 quartets. Approximately 49% of companion case deaths were homicides. Approximately 30% of companion case deaths were traumatic accidental deaths. Around 14% of companion case deaths that were from the same scene location had different manners of death, including suicide, homicide, natural, and indeterminate. The remainder of companion death cases were either drug related or natural. Through this study, we have identified a pattern to these companion death cases and have concluded that it is important to conduct a thorough medicolegal death investigation of such cases to establish and elucidate the true circumstances surrounding these deaths. PMID:26332646

  1. A Virtual Observatory Census to Address Dwarfs Origins (AVOCADO). I. Science goals, sample selection, and analysis tools

    NASA Astrophysics Data System (ADS)

    Sánchez-Janssen, R.; Amorín, R.; García-Vargas, M.; Gomes, J. M.; Huertas-Company, M.; Jiménez-Esteban, F.; Mollá, M.; Papaderos, P.; Pérez-Montero, E.; Rodrigo, C.; Sánchez Almeida, J.; Solano, E.

    2013-06-01

    Context. Even though they are by far the most abundant of all galaxy types, the detailed properties of dwarf galaxies are still only poorly characterised - especially because of the observational challenge that their intrinsic faintness and weak clustering properties represent. Aims: AVOCADO aims at establishing firm conclusions on the formation and evolution of dwarf galaxies by constructing and analysing a homogeneous, multiwavelength dataset for a statistically significant sample of approximately 6500 nearby dwarfs (Mi - 5 log h100 > - 18 mag). The sample is selected to lie within the 20 < D < 60 h100-1 Mpc volume covered by the SDSS-DR7 footprint, and is thus volume-limited for Mi - 5 log h100 < -16 mag dwarfs - but includes ≈1500 fainter systems. We will investigate the roles of mass and environment in determining the current properties of the different dwarf morphological types - including their structure, their star formation activity, their chemical enrichment history, and a breakdown of their stellar, dust, and gas content. Methods: We present the sample selection criteria and describe the suite of analysis tools, some of them developed in the framework of the Virtual Observatory. We use optical spectra and UV-to-NIR imaging of the dwarf sample to derive star formation rates, stellar masses, ages, and metallicities - which are supplemented with structural parameters that are used to classify them morphologically. This unique dataset, coupled with a detailed characterisation of each dwarf's environment, allows for a fully comprehensive investigation of their origins and enables us to track the (potential) evolutionary paths between the different dwarf types. Results: We characterise the local environment of all dwarfs in our sample, paying special attention to trends with current star formation activity. We find that virtually all quiescent dwarfs are located in the vicinity (projected distances ≲ 1.5 h100-1 Mpc) of ≳ L∗ companions, consistent with

  2. PROPERTIES OF THE COOLEST DWARFS

    SciTech Connect

    SAUMON, DIDIER; LEGGETT, SANDY K.; FREEDMAN, RICHARD S.; GEBALLE, THOMAS R.; GOLIMOWSKI, DAVID A.; LODIEU, NICOLAS; MARLEY, MARK S.; STEPHENS, DENISE; PINFIELD, DAVID J.; WARREN, STEPHEN J.

    2007-01-18

    Eleven years after the discovery of the first T dwarf, we have a population of ultracool L and T dwarfs that is large enough to show a range of atmospheric properties, as well as model atmospheres advanced enough to study these properties in detail. Since the last Cool Stars meeting, there have been observational developments which aid in these studies. they present recent mid-infrared photometry and spectroscopy from the Spitzer Space Telescope which confirms the prevalence of vertical mixing in the atmospheres of L and T dwarfs. Hence, the 700 K to 2200 K L and t dwarf photspheres require a large number of parameters for successful modeling: effective temperature, gravity, metallicity, grain sedimentation and vertical mixing efficiency. They also describe initial results of a search for ultracool dwarfs in the UKIRT Infrared Deep Sky Survey, and present the latest T dwarf found to date. They conclude with a discussion of the definition of the later-than-T spectral type, the Y dwarf.

  3. The quest for companions to post-common envelope binaries. III. A reexamination of HW Virginis

    NASA Astrophysics Data System (ADS)

    Beuermann, K.; Dreizler, S.; Hessman, F. V.; Deller, J.

    2012-07-01

    We report new mid-eclipse times of the short-period sdB/dM binary HW Virginis, which differ substantially from the times predicted by a previous model. The proposed orbits of the two planets in that model are found to be unstable. We present a new secularly stable solution, which involves two companions orbiting HW Vir with periods of 12.7 yr and 55 ± 15 yr. For orbits coplanar with the binary, the inner companion is a giant planet with mass M3 sin i3 ≃ 14 MJup and the outer one a brown dwarf or low-mass star with a mass of M4 sin i4 = 30-120 MJup. Using the mercury6 code, we find that such a system would be stable over more than 107 yr, in spite of the sizeable interaction. Our model fits the observed eclipse-time variations by the light-travel time effect alone, without invoking any additional process, and provides support for the planetary hypothesis of the eclipse-time variations in close binaries. The signature of non-Keplerian orbits may be visible in the data.

  4. Z Draconis with two companions in a 2:1 mean-motion resonance

    NASA Astrophysics Data System (ADS)

    Yuan, Jin-Zhao; Şenavcι, Hakan Volkan; Qian, Sheng-Bang

    2016-05-01

    All available mid-eclipse times of the eclipsing binary Z Draconis are analyzed, and three sets of cyclic variations with periods of 20.1, 29.96 and 59.88 yr are found. The low-amplitude variations with a period of 20.1 yr may be attributed to the unavoidable slight imperfection in the double-Keplerian model, which gives periods of 29.96 and 59.88 yr. Interestingly, the Z Draconis system is close to a 2:1 mean-motion resonance, or a 6:3:2 mean-motion resonance if the 20.1 yr period really exists. We also find that the best solutions tend to give the minimum eccentricities. Based on Kepler's third law, the outermost companion has a minimum mass of ∼ 0.77 M ⊙, whereas the middle companion is an M dwarf star with a mass of ∼ 0.40 M ⊙, suggesting that Z Draconis is a general N-body system.

  5. Helium Star Donor Channel to Type Ia Supernovae and Their Surviving Companion Stars

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Han, Zhanwen

    2013-01-01

    Employing Eggleton's stellar evolution code and assuming optically thick winds, we systematically studied the He star donor channel of Type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf (WD) accretes material from a He main-sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. We mapped out the initial parameters for producing SNe Ia in the orbital period-secondary mass plane for various WD masses from this channel. Based on a detailed binary population synthesis approach, we find that this channel can produce SNe Ia with short delay times (~100 Myr) implied by recent observations. We derived many properties of the surviving companions of this channel after SN explosion, which can be tested by future observations. We also find that the surviving companions from the SN explosion scenario have a high spatial velocity (>400 km/s), which could be an alternative origin for hypervelocity stars (HVSs), especially for HVSs such as US 708.

  6. Multi-Wavelength Implications of the Companion Star in eta Carinae

    NASA Technical Reports Server (NTRS)

    Madura, Thomas I.; Gull, Theodore R.; Groh, Jose H.; Owocki, Stanley P.; Okazaki, Atsuo; Hillier, D. John; Russell, Christopher

    2012-01-01

    Eta-Carinae is considered to be a massive colliding wind binary system with a highly eccentric (e approximately 0.9), 5.54-yr orbit. However, the companion star continues to evade direct detection as the primary dwarfs its emission at most wavelengths. Using three-dimensional (3-D) SPH simulations of eta-Car's colliding winds and radiative transfer codes, we are able to compute synthetic observables across multiple wavebands for comparison to the observations. The models show that the presence of a companion star has a profound influence on the observed HST/STIS UV spectrum and H-alpha line profiles, as well as the ground-based photometric monitoring. Here, we focus on the Bore Hole effect, wherein the fast wind from the hot secondary star carves a cavity in the dense primary wind, allowing increased escape of radiation from the hotter/deeper layers of the primary's extended wind photosphere. The results have important implications for interpretations of eta-Car's observables at multiple wavelengths.

  7. Combinatorics and companion galaxies: Paradox lost

    NASA Technical Reports Server (NTRS)

    Newman, William I.; Terzian, Yervant

    1995-01-01

    Arp (1994) has presented redshift data for the Local Group of galaxies and for the next major group, whose largest galaxies are M31 and M81, respectively. He observed that the relative redshifts of all 22 of their companions were positive and claimed that the likelihood that this would occur is 1 in 4 x 10(exp 6). We show using the classical combinatoric paradigm of ordered samples (without replacement) that the correct probability for the dominant member of each cluster to possess the lowest observed redshift is approximately 8%.

  8. Discovery of spin-up in the X-ray pulsar companion of the hot subdwarf HD 49798

    NASA Astrophysics Data System (ADS)

    Mereghetti, Sandro; Pintore, Fabio; Esposito, Paolo; La Palombara, Nicola; Tiengo, Andrea; Israel, Gian Luca; Stella, Luigi

    2016-06-01

    The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28 ± 0.05 M⊙, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton and Swift observations of this source, we could perform a phase-connected timing analysis extending back to the ROSAT data obtained in 1992. We found that the pulsar is spinning up at a rate of (2.15 ± 0.05) × 10-15 s s-1. This result is best interpreted in terms of a neutron star accreting from the wind of its subdwarf companion, although the remarkably steady period derivative over more than 20 yr is unusual in wind-accreting neutron stars. The possibility that the compact object is a massive white dwarf accreting through a disc cannot be excluded, but it requires a larger distance and/or properties of the stellar wind of HD 49798 different from those derived from the modelling of its optical/UV spectra.

  9. Discovery of the Accretion-Powered Millisecond Pulsar SWIFT 51756.9-2508 with a Low-Mass Companion

    NASA Technical Reports Server (NTRS)

    Krimm, H.A.; Markwardt, C.B.; Deloye, C.J.; Romano, P.; Chakrabarty, S.; Campana. S.; Cummings, J.C.; Galloway, D.K.; Gehrels, N.; Hartman, J.M.; Kaaret, P.; Morgan, E.H.; Tueller, J

    2007-01-01

    We report on the discovery by the Swift Gamma-Ray Burst Explorer of the eighth known transient accretion-powered millisecond pulsar: SWIFT J1756.9-2508, as part of routine observations with the Swift Burst Alert Telescope hard X-ray transient monitor. The pulsar was subsequently observed by both the X-Ray Telescope on Swift and the Rossi X-Ray Timing Explorer Proportional Counter Array. It has a spin frequency of 182 Hz (5.5 ms) and an orbital period of 54.7 minutes. The minimum companion mass is between 0.0067 and 0.0086 Solar Mass, depending on the mass of the neutron star, and the upper limit on the mass is 0.030 Solar Mass (95% confidence level). Such a low mass is inconsistent with brown dwarf models. and comparison with white dwarf models suggests that the companion is a He-dominated donor whose thermal cooling has been at least modestly slowed by irradiation from the accretion flux. No X-ray bursts. dips, eclipses or quasi-periodic oscillations were detected. The current outburst lasted approx. 13 days and no earlier outbursts were found in archival data.

  10. Combining Astrometry and Light-time Effect: Low-mass Companions around Eclipsing Systems

    NASA Astrophysics Data System (ADS)

    Ribas, I.

    2005-07-01

    We discuss a method to determine orbital properties and masses of low-mass bodies orbiting eclipsing binaries based on combined analyses of light-travel time (LTT) and astrometry. The presence of a third body causes the relative distance of the eclipsing pair to the Earth to change as it orbits the barycenter of the triple system, thus causing periodic variatio