J/ApJ/908/87ivo://CDS.VizieR/J/ApJ/908/87doi:10.26093/cds/vizier.19080087CDSNeugent K.F.2025-06-19T20:10:29Z2024-02-12T09:56:10ZCDS support team

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

cds-question@unistra.frob-starssupergiant-starsmultiple-starstwo-color-diagramsvisible-astronomyRecent work measuring the binary fraction of evolved red supergiants (RSGs) in the Magellanic Clouds points to a value between 15% and 30%, with the majority of the companions being unevolved B-type stars as dictated by stellar evolution. Here I extend this research to the Local Group galaxies M31 and M33 and investigate the RSG binary fraction as a function of metallicity. Recent near-IR photometric surveys of M31 and M33 have led to the identification of a complete sample of RSGs down to a limiting logL/L{sun}>=4.2. To determine the binary fraction of these M31 and M33 RSGs, I used a combination of newly obtained spectroscopy to identify single RSGs and RSG+OB binaries, as well as archival UV, visible, and near-IR photometry to probabilistically classify RSGs as either single or binary based on their colors. I then adjusted the observed RSG+OB binary fraction to account for observational biases. The resulting RSG binary fraction in M33 shows a strong dependence on galactocentric distance, with the inner regions having a much higher binary fraction (41.2_-7.3_^+12.0^%) than the outer regions (15.9_-1.9_^+12.4^%). Such a trend is not seen in M31; instead, the binary fraction in lightly reddened regions remains constant at 33.5_-5.0_^+8.6^% . I conclude that the changing RSG binary fraction in M33 is due to a metallicity dependence, with higher-metallicity environments having higher RSG binary fractions. This dependence most likely stems not from changes in the physical properties of RSGs due to metallicity but from changes in the parent distribution of OB binaries.2021ApJ...908...87Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/908/87CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)J/ApJ/501/153 : VRB photometry of red supergiants (Massey 1998)J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)J/AJ/134/2474 : Ha emission-line stars in 7 dwarfs galaxies (Massey+, 2007)J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011)J/ApJ/750/97 : The yellow and red supergiants of M33 (Drout+, 2012)J/ApJ/759/11 : Wolf-Rayet content of M31 (Neugent+, 2012)J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)J/ApJ/758/133 : Metallicity profile of M31 HII regions & PNe (Sanders+, 2012)J/A+A/550/A107 : RV catalogue of O stars in 30 Doradus (Sana+, 2013)J/ApJ/789/10 : M33 WR and Of-type Stars (Neugent+, 2014)J/A+A/578/A3 : Survey of supergiants in the MCs (Gonzalez-Fernandez+, 2015)J/ApJ/826/224 : RSG and foreground candidates in M31 (Massey+, 2016)J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)J/ApJ/875/124 : Binary red supergiants. II. B-type companions (Neugent+, 2019)J/A+A/624/A129 : 30 Dor red supergiant stars radial velocities (Patrick+, 2019)J/A+A/629/A91 : A source catalog for the SMC (Yang+, 2019)J/ApJ/900/118 : RSGs in the LMC & sp. follow-up for LMC & SMC (Neugent+, 2020)J/ApJ/889/44 : UKIRT obs. of red supergiants in M31 (Neugent+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/908/87https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/908/87http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/908/87https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/908/87https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/908/87http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/908/87GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/908/87/table1 (*Spectroscopically observed M31 and M33 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/908/87/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/908/87/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/908/87/table1?GETtext/xml+votable180.050000true9.434833340.06705560.0055555555555555566/2154-2155 2241 2622-2623 2666 2705 2709 2752https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/908/87?format=asciiOpticaldefaultJ/ApJ/908/87/table1*Spectroscopically observed M31 and M33 starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLGGSLocal Group Galaxy Survey designationmeta.id;meta.maincharRAJ2000[0/1] Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000[30/42] Degree of Declination (J2000)pos.eq.dec;meta.mainVmag[17.2/20.4] Apparent V band magnitudemagphot.mag;em.opt.VfloatB-V[-0.2/2.18] The (B-V) colormagphot.color;em.opt.B;em.opt.VfloatU-B[-1.2/0.58] The (U-B) colormagphot.color;em.opt.U;em.opt.BfloatV-R[-0.13/1.42] The (V-R) colormagphot.color;em.opt.V;em.opt.RfloatR-I[-0.23/1.55] The (R-I) colormagphot.color;em.opt.R;em.opt.IfloatClassClassification; OB, RSG or RSG+Bsrc.classcharSimbadSimbad column added by the CDSmeta.ref.urlchar