J/A+A/550/A107ivo://CDS.VizieR/J/A+A/550/A107doi:10.26093/cds/vizier.35500107CDSSana H.de Koter A.de Mink S.E.Dunstall P.R.Evans C.J.,Henault-Brunet V.Maiz Apellaniz J.Ramirez-Agudelo O.H.Taylor W.D.,Walborn N.R.Clark J.S.Crowther P.A.Herrero A.Gieles M.Langer N.,Lennon D.J.Vink J.S.2017-06-01T08:53:02Z2013-02-04T10:42:15ZCDS support team

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

cds-question@unistra.frmagellanic-cloudso-starsspectroscopic-binary-starsradial-velocityThe Tarantula Nebula in the Large Magellanic Cloud is our closest view of a starburst region and is the ideal environment to investigate important questions regarding the formation, evolution and final fate of the most massive stars. We analyze the multiplicity properties of the massive O-type star population observed through multi-epoch spectroscopy in the framework of the VLT-FLAMES Tarantula Survey. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. By modelling simultaneously the observed binary fraction, the distributions of the amplitudes of the radial velocity variations and the distribution of the time scales of these variations, we derive the intrinsic current binary fraction and period and mass-ratio distributions. We observe a spectroscopic binary fraction of 0.35+/-0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20km/s . We compute the intrinsic binary fraction to be 0.51+/-0.04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f(log_10_P/d)~(log_10_ P/d)^pi^ (with log_10_P/d in the range 0.15-3.5) and f(q)~q^kappa^ with 0.1<q=M2/M1< 1.0. The power-law indexes that best reproduce the observed quantities are pi=-0.45+/-0.30 and kappa=-1.0+/-0.4. The period distribution that we obtain thus favours shorter period systems compared to an Opik law (pi=0). The mass ratio distribution is slightly skewed towards low mass ratio systems but remains incompatible with a random sampling of a classical mass function (kappa=-2.35). The binary fraction seems mostly uniform across the field of view and independent of the spectral types and luminosity classes. The binary fraction in the outer region of the field of view (r>7.8 , i.e. ~117pc) and among the O9.7 I/II objects are however significantly lower than expected from statistical fluctuations. The observed and intrinsic binary fractions are also lower for the faintest objects in our sample (Ks>15.5mag), which results from observational effects and the fact that our O star sample is not magnitude-limited but is defined by a spectral-type cutoff. We also conclude that magnitude-limited investigations are biased towards larger binary fractions. Using the multiplicity properties of the O stars in the Tarantula region and simple evolutionary considerations, we estimate that over 50% of the current O star population will exchange mass with its companion within a binary system. This shows that binary interaction is greatly affecting the evolution and fate of massive stars, and must be taken into account to correctly interpret unresolved populations of massive stars.2013A&A...550A.107Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/550/A107CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/530/A108 : VLT-FLAMES Tarantula Survey (Evans+, 2011)J/A+A/550/A108 : DIB in VLT-FLAMES Tarantula Survey (van Loon+, 2013)J/A+A/550/A109 : vsini in VLT-FLAMES Tarantula Survey (Dufton+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/550/A107https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/550/A107http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/550/A107https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/550/A107https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/550/A107http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/550/A107GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/550/A107/stars (Stars observed: list of lines used for RV measurements and Multiplicity status)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/550/A107/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/550/A107/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/550/A107/stars?GETtext/xml+votable180.050000true84.28129167-69.085244440.0055555555555555566/33094https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/550/A107?format=asciiOpticaldefaultJ/A+A/550/A107/table2RV data baserecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVFTS[14/892] VLT-FLAMES Tarantula Survey identifiermeta.id;meta.mainintHJDHeliocentric Julian date (HJD-2400000)dtime.epochdoubleRVRadial velocity (RV)km/sphys.veloc;pos.heliocentricfloate_RV1{sigma} uncertainty on RVkm/sstat.errorfloatJ/A+A/550/A107/starsStars observed: list of lines used for RV measurements and Multiplicity statussigVar? Significance of the RV variability (1)src.var.indexfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVCVelocity curve (if 4 or more measures)meta.codecharVFTS[14/892] VLT-FLAMES Tarantula Survey identifiermeta.id;meta.mainintprimaryNNumber of velocity observationsmeta.numberintnullable4026[x-] HeI+II 4026 line used (6)meta.codechar4200[x-] HeII 4200 line used (6)meta.codechar4387[x-] HeI 4387 line used (6)meta.codechar4471[x-] HeI 4471 line used (6)meta.codechar4541[x-] HeII 4541 line used (6)meta.codechar4686[x-] HeII 4686 line used (6)meta.codechar4713[x-] HeI 4713 line used (6)meta.codechar4922[x-] HeI 4922 line used (6)meta.codecharPapIDetails from Paper I for this source (Evans et al. 2011, Cat. J/A+A/530/A108)meta.codechardRV? Amplitude of the RV variations (2)km/ssrc.var.amplitudefloatnullableLPV[y:-] Line profile variations (3)meta.codecharMorphMorphological comments (3)(4)src.morphcharHSTMultiplicity in HST images (3)(5)meta.codecharSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from Paper I, Evans et al., 2011, Cat. J/A+A/530/A108 (right ascension part)degpos.eq.ra;meta.main_DEPositions from Paper I, Evans et al., 2011, Cat. J/A+A/530/A108 (declination part)degpos.eq.dec;meta.main