J/ApJ/839/23ivo://CDS.VizieR/J/ApJ/839/23doi:10.26093/cds/vizier.18390023CDSBrown W.R.Kilic M.Gianninas A.2018-03-12T08:32:46Z2017-12-11T10:01:46ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frwhite-dwarf-starseclipsing-binary-starsradial-velocitymetallicityWe address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution spectroscopy. However, colors and proper motions indicate that sdA stars are cooler and more luminous, and thus larger in radius, than published ELM WDs. We demonstrate that surface gravities derived from pure hydrogen models suffer a systematic ~1dex error for sdA stars, likely explained by metal line blanketing below 9000K. A detailed study of five eclipsing binaries with radial velocity orbital solutions and infrared excess establishes that these sdA stars are metal-poor ~1.2M_{sun}_ main sequence stars with ~0.8M_{sun}_ companions. While WDs must exist at sdA temperatures, only ~1% of a magnitude-limited sdA sample should be ELM WDs. We conclude that the majority of sdA stars are metal-poor A-F type stars in the halo, and that recently discovered pulsating ELM WD-like stars with no obvious radial velocity variations may be SX Phe variables, not pulsating WDs.2017ApJ...839...23Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/839/23CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)J/ApJS/99/135 : Rotation and Spectral Peculiarities (Abt+ 1995)J/A+A/339/123 : PSR J1012+5307 evolutionary tracks (Driebe+ 1998)J/PASP/110/863 : A Stellar Spectral Flux Library: 1150 - 25000 A (Pickles 1998)J/ApJ/573/359 : Rotational velocities of B stars from BSC (Abt+, 2002)J/AJ/131/582 : Cool white dwarfs in the SDSS (Kilic+, 2006)J/AJ/136/2070 : SEGUE stellar parameter pipeline. III. (Allende Prieto+, 2008)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJ/723/1072 : The ELM survey. I. Low-mass white dwarfs (Brown+, 2010)J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)J/MNRAS/417/1210 : DA-white dwarfs from SDSS and UKIDSS (Girven+, 2011)J/ApJ/743/138 : Spectroscopic survey of bright white dwarfs (Gianninas+, 2011)J/AJ/141/89 : SEGUE stellar parameter pipeline. IV. (Smolinski+, 2011)J/A+A/557/A19 : Mass and age of extreme low-mass white dwarfs (Althaus+, 2013)J/ApJ/769/66 : The ELM survey. V. White dwarf binaries (Brown+, 2013)J/A+A/568/A7 : Model SDSS colors for halo stars (Allende Prieto+, 2014)J/ApJ/794/35 : Binary white dwarfs atmospheric parameters (Gianninas+, 2014)J/MNRAS/448/2260 : White dwarf candidates in SDSS DR10 (Gentile Fusillo+, 2015)J/ApJ/812/167 : The ELM survey. VI. 11 new ELM WD binaries (Gianninas+, 2015)J/MNRAS/446/4078 : New white dwarf stars in SDSS DR10 (Kepler+, 2015)J/ApJ/818/155 : The ELM survey. VII. 15 new ELM WD cand. (Brown+, 2016)J/A+A/595/A35 : Low-mass helium WDs evolutionary models (Istrate+, 2016)J/MNRAS/455/3413 : New WD and subdwarf stars in SDSS DR12 (Kepler+, 2016)J/A+A/600/A50 : Catalog of hot subdwarf stars (Geier+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/839/23https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/839/23http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/839/23https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/839/23https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/839/23http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/839/23GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/839/23/stars (Summary of observations and stellar atmosphere parameters (tables 1 and 2))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/839/23/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/839/23/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/839/23/stars?GETtext/xml+votable180.050000true116.8959791745.905561110.0055555555555555566/4628 5682 6430 6447 6542 6556 6557 6559 6588 6630 7378 9354 9730 12756 19402 21817 23126 26086 27254 31447 36763 49133https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/839/23?format=asciiOpticaldefaultJ/ApJ/839/23/table5Radial velocity datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSDSS designation (JHHMMSS.sss+DDMMSS.ss)meta.id;meta.maincharANameShort named used in articlemeta.codecharHJDHeliocentric Julian Date; JD-2450000, based on UTCdtime.epochdoubleHRV[-486/339] Heliocentric radial velocity (1)km/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[3/51] Uncertainty in HRVkm/sstat.errorfloatJ/ApJ/839/23/starsSummary of observations and stellar atmosphere parameters (tables 1 and 2)VarRV variable star?meta.codecharNameSDSS designation (JHHMMSS.sss+DDMMSS.ss)meta.numbercharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSetSet: sdA = subdwarf A-type stars or sdAL = sdA-like extremely low mass (ELM) WD candidatesmeta.code.classcharNsp[4/27] Number of spectroscopic measurementsmeta.numberintNph[0/757] Number of photometric measurementsmeta.numberintEclEclipsing?meta.codecharIRexIR excess?meta.codecharRVInteractive Velocity Plotmeta.ref.urlcharANameAbbreviated name used in the articlemeta.codecharTeff[6652/8466] Gianninas effective temperature (1)Kphys.temperature.effectiveinte_Teff[111/232] Teff uncertaintyKstat.error;phys.temperature.effectiveintlogg[4.7/6.1] Gianninas log surface gravity (1)log(cm.s**-2)phys.gravityfloate_logg[0.06/0.6] logg uncertaintylog(cm.s**-2)stat.errorfloatTeffK[6786/8355]? Kepler effective temperature (2)Kphys.temperature.effectiveintnullableloggK[5.3/6.4]? Kepler log surface gravity (2)log(cm.s**-2)phys.gravityfloatnullableTeffS[6769/7906]? SEGUE stellar parameter pipeline effective temperatureKphys.temperature.effectiveintnullablee_TeffS[46/286]? TeffS uncertaintyKstat.errorintnullableloggS[3.5/4.4]? SEGUE stellar parameter pipeline log surface gravitylog(cm.s**-2)stat.param;phys.gravityfloatnullablee_loggS[0.09/0.4]? loggS uncertaintylog(cm.s**-2)stat.errorfloatnullable[Fe/H][-1.8/-0.3]? SEGUE stellar parameter pipeline metallicitylog(Sun)phys.abund.Zfloatnullablee_[Fe/H][0.01/0.3]? [Fe/H] uncertaintylog(Sun)stat.error;phys.abund.FefloatnullableSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from SDSS designations (right ascension part)degpos.eq.ra;meta.main_DEPositions from SDSS designations (declination part)degpos.eq.dec;meta.main