J/ApJ/898/47ivo://CDS.VizieR/J/ApJ/898/47doi:10.26093/cds/vizier.18980047CDSFurlan E.Howell S.B.2022-10-04T11:54:37Z2021-12-13T09:29:04ZCDS support team

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

cds-question@unistra.frmultiple-starsspectroscopyastronomical-modelsmetallicitystellar-radiivisible-astronomyIn this work, we quantify the effect of an unresolved companion star on the derived stellar parameters of the primary star if a blended spectrum is fit assuming the star is single. Fitting tools that determine stellar parameters from spectra typically fit for a single star, but we know that up to half of all exoplanet host stars may have one or more companion stars. We use high- resolution spectra of planet host stars in the Kepler field from the California-Kepler Survey to create simulated binaries; we select eight stellar pairs and vary the contribution of the secondary star, then determine stellar parameters with SpecMatch-Emp and compare them to the parameters derived for the primary star alone. We find that, in most cases, the effective temperature, surface gravity, metallicity, and stellar radius derived from the composite spectrum are within 2-3{sigma} of the values determined from the unblended spectrum, but the deviations depend on the properties of the two stars. Relatively bright companion stars that are similar to the primary star have the largest effect on the derived parameters; in these cases, the stellar radii can be overestimated by up to 60%. We find that metallicities are generally underestimated, with values up to eight times smaller than the typical uncertainty in [Fe/H]. Our study shows that follow-up observations are necessary to detect or set limits on stellar companions of planetary host stars so that stellar (and planet) parameters are as accurate as possible.2020ApJ...898...47Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/898/47CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/133 : Kepler Input Catalog (Kepler Mission Team, 2009)J/A+A/415/1153 : [Fe/H] for 98 extra-solar planet-host stars (Santos+, 2004)J/ApJ/622/1102 : The planet-metallicity correlation. (Fischer+, 2005)J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)J/A+A/512/A13 : EW-Teff calibration for solar-type stars (Sousa+, 2010)J/AJ/142/19 : Speckle observations of KOI (Howell+, 2011)J/AJ/144/42 : Infrared photometry of 90 KOIs (Adams+, 2012)J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)J/A+A/546/A10 : Multiplicity in planet-host stars (Lillo-Box+, 2012)J/ApJ/750/L37 : Stellar parameters of low-mass KOIs (Muirhead+, 2012)J/ApJ/757/161 : Spectroscopy of 56 exoplanet host stars (Torres+, 2012)J/ApJ/771/107 : Spectroscopy of faint KOI stars (Everett+, 2013)J/ApJ/767/127 : Asteroseismic solutions for 77 Kepler stars (Huber+, 2013)J/A+A/558/A106 : Chemical abundances for 83 transit hosts (Mortier+, 2013)J/ApJS/211/2 : Revised properties of Q1-16 Kepler targets (Huber+, 2014)J/ApJ/791/35 : Detection of Kepler planet candidates host stars (Law+, 2014)J/A+A/566/A103 : Kepler planet host candidates imaging (Lillo-Box+, 2014)J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)J/AJ/147/86 : From binaries to multiples. I. FG-67 sample (Tokovinin, 2014)J/ApJ/806/248 : AO imaging of KOIs with gas giant planets (Wang+, 2015)J/ApJ/813/130 : Kepler multiple transiting planet systems (Wang+, 2015)J/AJ/152/18 : Robo-AO Kepler planetary cand. survey. II. (Baranec+, 2016)J/AJ/152/8 : Stellar multiplicity impact on planets I. (Kraus+, 2016)J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)J/AJ/153/71 : Kepler follow-up obs. program. I. Imaging (Furlan+, 2017)J/AJ/153/117 : KOIs companions from high-resolution imaging (Hirsch+, 2017)J/AJ/154/108 : California-Kepler Survey (CKS). II. (Johnson+, 2017)J/ApJS/229/30 : Revised properties of Q1-17 Kepler targets (Mathur+, 2017)J/AJ/154/107 : California-Kepler Survey (CKS). I. (Petigura+, 2017)J/ApJ/836/77 : A library of high-S/N opt. spectra of FGKM stars (Yee+, 2017)J/AJ/153/66 : Robo-AO Kepler Planetary Cand. Survey. III. (Ziegler+, 2017)J/ApJ/866/99 : Radii of KIC stars & planets using Gaia DR2 (Berger+, 2018)J/ApJS/237/38 : Extended abundance analysis of KOIs (Brewer+, 2018)J/AJ/156/264 : CKS. VII. Planet radius gap (Fulton+, 2018)J/ApJ/861/149 : Kepler Follow-up Obs. Program. II. Spectro. (Furlan+, 2018)J/AJ/155/89 : California-Kepler Survey (CKS). IV. Planets (Petigura+, 2018)J/AJ/156/292 : Effect of close companions on exoplanet radii (Teske+, 2018)J/ApJS/235/6 : Updated Mult. Star Catalog (MSC): Sept 2021 (Tokovinin, 2018)J/AJ/155/48 : CKS. V. Masses and radii (Weiss+, 2018)J/AJ/155/161 : Stars nearby Robo-AO Kepler planetary cand. (Ziegler+, 2018)J/AJ/158/113 : Kepler-13AB aperture photometry (Howell+, 2019)J/ApJ/888/34 : AO Kepler asteroseismic survey. II. (Schonhut-Stasik+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/898/47https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/898/47http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/898/47https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/898/47https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/898/47http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/898/47GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/898/47/table1 (Stellar parameters derived with SpecMatch-Emp for the eight stellar pairs used in this work to create simulated binaries)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/898/47/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/898/47/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/898/47/table1?GETtext/xml+votable180.050000true290.944465840.4800850.0055555555555555566/14581 14735 14756 14764 14794 14932-14933 14956 14966 14973 15104 15113 15123 15142https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/898/47?format=asciiOpticaldefaultJ/ApJ/898/47/table1Stellar parameters derived with SpecMatch-Emp for the eight stellar pairs used in this work to create simulated binaries_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBinSimulated binary numbermeta.number;phys.atmol.numberchardTeff[32/1404] {Delta}Teff of binariesKphys.temperature.effective;arith.diffintdL[0.15/0.84] L_sec_/L_prim_ ratiophys.luminosity;arith.ratiofloatKOI[116/5622] KOI star identifier (<KOI-NNNNN> in Simbad)meta.id;meta.mainintprimaryTeff[4446/5892] Effective temperatureKphys.temperature.effectiveinte_Teff[70/110] Teff uncertaintyKstat.error;phys.temperature.effectiveintlogg[4.22/4.62] Log of surface gravitylog(cm.s**-2)phys.gravityfloate_logg[0.12/0.12] Logg uncertaintylog(cm.s**-2)stat.errorfloat[Fe/H][-0.11/0.2] [Fe/H] abundancelog(Sun)phys.abund.Fefloate_[Fe/H][0.09/0.09] [Fe/H] uncertaintylog(Sun)stat.error;phys.abund.FefloatRad[0.7/1.2] RadiussolRadphys.size.radiusfloate_Rad[0.1/0.18] Rad uncertaintysolRadstat.errorfloatChi2[0.43/13.04] Median {chi}^2^ value (G1)stat.fit.chi2floatS/N[20.9/135.3] Signal-to-noise ratio of the spectrumstat.snrfloatParamDisplay the derived parameters for this system (link to Table 2)meta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.mainJ/ApJ/898/47/table2Stellar parameters derived with SpecMatch-Emp from the blended spectra of the the simulated binariesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStar1KOI star identifier, primarymeta.id;meta.mainintStar2KOI star identifier, secondarymeta.idintRVshift[-500/500] RV shift applied to the scaled spectrum of secondary starkm/sphys.veloc;arith.diffintTeff[4861/6154] Effective temperature, primaryKphys.temperature.effectiveinte_Teff[110] Uncertainty in TeffKstat.error;phys.temperature.effectiveintlogg[4/4.56] Log surface gravity, primarylog(cm.s**-2)phys.gravityfloate_logg[0.12] Uncertainty in logglog(cm.s**-2)stat.errorfloatFeH[-0.6/0.16] Metallicity, primarylog(Sun)phys.abund.Fefloate_FeH[0.09] Uncertainty in FeHlog(Sun)stat.errorfloatRad[0.7/1.83] Radius, primarysolRadphys.size.radiusfloate_Rad[0.1/0.18] Uncertainty in RadiussolRadstat.errorfloatchi2[0.9/38] Median {chi}^2^ value of the fit (G1)stat.fit.param;stat.medianfloat