J/A+A/657/A4ivo://CDS.VizieR/J/A+A/657/A4doi:10.26093/cds/vizier.36570004CDSMahy L.Lanthermann C.Hutsemekers D.Kluska J.Lobel A.Manick R.,Miszalski B.Reggiani M.Sana H.Gosset E.2022-10-12T07:18:43Z2021-12-20T08:15:04ZCDS support team

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

cds-question@unistra.frvariable-starsspectroscopyradial-velocityvisible-astronomyLuminous blue variables (LBVs) are characterised by strong photometric and spectroscopic variability. They are thought to be in a transitory phase between O-type stars on the main sequence and the Wolf-Rayet stage. Recent studies also evoked the possibility that they might be formed through binary interaction. Only a few are known in binary systems so far, but their multiplicity fraction is still uncertain. We derive the binary fraction of the Galactic LBV population. We combine multi-epoch spectroscopy and long-baseline interferometry to probe separations from 0.1 to 120mas around confirmed and candidate LBVs. We used a cross-correlation technique to measure the radial velocities of these objects. We identified spectroscopic binaries through significant radial velocity variability with an amplitude larger than 35km/s. We also investigated the observational biases to take them into account when we established the intrinsic binary fraction. We used candid to detect interferometric companions, derive their flux fractions, and their positions on the sky. From the multi-epoch spectroscopy, we derive an observed spectroscopic binary fraction of 26-10+16%. Considering period and mass ratio ranges from log(Porb)=0-3 (i.e. from 1 to 1000days), q=0.1-1.0, and a representative set of orbital parameter distributions, we find a bias-corrected binary fraction of 62_-24_^+38^%. Based on data of the interferometric campaign, we detect a binary fraction of 70+/-9% at projected separations between 1 and 120mas. Based on the derived primary diameters and considering the distances of these objects, we measure for the first time the exact radii of Galactic LBVs to be between 100 and 650R_{sun}_. This means that it is unlikely that short-period systems are included among LBV-like stars. This analysis shows for the first time that the binary fraction in the Galactic LBV population is large. If they form through single-star evolution, their orbit must be large initially. If they form through a binary channel, the implication is that either massive stars in short binary systems must undergo a phase of fully non-conservative mass transfer to be able to sufficiently widen the orbit to form an LBV, or that LBVs form through merging in initially binary or triple systems. Interferometric follow-up would provide the distributions of orbital parameters at more advanced stages and would serve to quantitatively test the binary evolution in massive stars.2022A&A...657A...4Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/657/A4CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/657/A4https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/657/A4http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/657/A4https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/657/A4https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/657/A4http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/657/A4GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/657/A4/stars (stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/657/A4/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/657/A4/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/657/A4/stars?GETtext/xml+votable180.050000true279.75-13.84640.0055555555555555566/14643 14692 28804 28830-28831 29116 29159 29558 30694 37339 37841 37923-37924 37930 42206 42383 42387https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/657/A4?format=asciiOpticaldefaultJ/A+A/657/A4/starsstarsDEJ2000Declination (J2000)pos.eq.dec;meta.mainRVsDisplay the RVS from table A1meta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right ascension (J2000)pos.eq.raRASRight ascension (J2000)spos.eq.ra;meta.mainStarStar namemeta.id;meta.maincharJ/A+A/657/A4/tablea1Compilation of RVs derived for the starse_SiII6347-71? Error on SiII RVkm/sstat.errorintnullableNeI6402? NeI radial velocitykm/sspect.dopplerVelocfloatnullablee_NeI6402? Error on NeI RVkm/sstat.errorfloatnullableSII6449? SII radial velocitykm/sspect.dopplerVelocfloatnullablee_SII6449? Error on SII RVkm/sstat.errorfloatnullableCII6578-83? CII radial velocitykm/sspect.dopplerVelocfloatnullablee_CII6578-83? Error on CII RVkm/sstat.errorfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharHJDHeliocentric Julian datedtime.epochdoubleSiII4128-4130? SiII radial velocitykm/sspect.dopplerVelocfloatnullablee_SiII4128-4130? Error on SiII RVkm/sstat.errorfloatnullableSIII4253? SIII radial velocitykm/sspect.dopplerVelocfloatnullablee_SIII4253? Error on SiIII RVkm/sstat.errorfloatnullableHeI4471? HeI radial velocitykm/sspect.dopplerVelocfloatnullablee_HeI4471? Error on HeI RVkm/sstat.errorfloatnullableMgII4481? MgII radial velocitykm/sspect.dopplerVelocfloatnullablee_MgII4481? Error on MgII RVkm/sstat.errorfloatnullableHeI4471+MgII4481? HeI and MgII radial velocitykm/sspect.dopplerVelocfloatnullablee_HeI4471+MgII4481? Error on HeI+MgII RVkm/sstat.errorfloatnullableFeII4526-34-36? FeII radial velocitykm/sspect.dopplerVelocfloatnullablee_FeII4526-34-36? Error on FeII RVkm/sstat.errorfloatnullableSiIII4552? SiIII radial velocitykm/sspect.dopplerVelocfloatnullablee_SiIII4552? Error on SiIII RVkm/sstat.errorfloatnullableNII4630? NII radial velocitykm/sspect.dopplerVelocfloatnullablee_NII4630? Error on NII RVkm/sstat.errorfloatnullableSiIII4813-19-28? SiIII radial velocitykm/sspect.dopplerVelocfloatnullablee_SiIII4813-19-28? Error on SiIII RVkm/sstat.errorfloatnullableFeIII5156? FeIII radial velocitykm/sspect.dopplerVelocfloatnullablee_FeIII5156? Error on FeIII RVkm/sstat.errorfloatnullableSII5454-74? SII radial velocitykm/sspect.dopplerVelocfloatnullablee_SII5454-74? Error on SII RVkm/sstat.errorfloatnullableNII5666-76-79-86+AlIII5723? NII and AlIII radial velocitykm/sspect.dopplerVelocfloatnullablee_NII5666-76-79-86+AlIII5723? Error on NII+AlIII RVkm/sstat.errorfloatnullableHeI5876? HeI radial velocitykm/sspect.dopplerVelocfloatnullablee_HeI5876? Error on HeI RVkm/sstat.errorfloatnullableSiII5979? SiII radial velocitykm/sspect.dopplerVelocfloatnullablee_SiII5979? Error on SiII RVkm/sstat.errorfloatnullableFeII6179? FeII radial velocitykm/sspect.dopplerVelocfloatnullablee_FeII6179? Error on FeII RVkm/sstat.errorfloatnullableSiII6347? SiII radial velocitykm/sspect.dopplerVelocfloatnullablee_SiII6347? Error on SiII RVkm/sstat.errorfloatnullableSiII6371? SiII radial velocitykm/sspect.dopplerVelocfloatnullablee_SiII6371? Error on SiII RVkm/sstat.errorfloatnullableSiII6347-71? SiII radial velocitykm/sspect.dopplerVelocintnullableMgII21347-21438? MgII radial velocitykm/sspect.dopplerVelocfloatnullablee_MgII21347-21438? Error on MgII RVkm/sstat.errorfloatnullableMean? Mean radial velocityspect.dopplerVelocfloatnullablee_Mean? Error on mean RVstat.errorfloatnullable