J/ApJ/751/4ivo://CDS.VizieR/J/ApJ/751/4doi:10.26093/cds/vizier.17510004CDSKiminki D.C.Kobulnicky H.A.2017-12-18T07:56:49Z2014-01-29T08:43:31ZCDS support team

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

cds-question@unistra.frearly-type-starsradial-velocitystellar-associationsspectroscopic-binary-starsThis work provides a statistical analysis of the massive star binary characteristics in the Cygnus OB2 association using radial velocity information of 114 B3-O5 primary stars and orbital properties for the 24 known binaries. We compare these data to a series of Monte Carlo simulations to infer the intrinsic binary fraction and distributions of mass ratios, periods, and eccentricities. We model the distribution of mass ratio, log-period, and eccentricity as power laws and find best-fitting indices of {alpha}=0.1+/-0.5, {beta}=0.2+/-0.4, and {gamma}=-0.6+/-0.3, respectively. These distributions indicate a preference for massive companions, short periods, and low eccentricities. Our analysis indicates that the binary fraction of the cluster is 44%+/-8% if all binary systems are (artificially) assumed to have P<1000 days; if the power-law period distribution is extrapolated to 10^4^ years, then a plausible upper limit for bound systems, the binary fraction is ~90%+/-10%. Of these binary (or higher order) systems, ~45% will have companions close enough to interact during pre- or post-main-sequence evolution (semi-major axis <~4.7AU). The period distribution for P<26 days is not well reproduced by any single power law owing to an excess of systems with periods around 3-5 days (0.08-0.31AU) and a relative shortage of systems with periods around 7-14 days (0.14-0.62AU). We explore the idea that these longer-period systems evolved to produce the observed excess of short-period systems. The best-fitting binary parameters imply that secondaries generate, on average, ~16% of the V-band light in young massive populations. This means that photometrically based distance measurements for young massive clusters and associations will be systematically low by ~8% (0.16 mag in the distance modulus) if the luminous contributions of unresolved secondaries are not taken into account.2012ApJ...751....4Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/751/4CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/773/135 : Cyg OB2 cand. stars with disk multiphot. (Guarcello+, 2013)J/A+A/543/A101 : OB stars in Cygnus OB2 association (Comeron+, 2012)J/ApJS/202/19 : riz photometry in Cyg OB2 (Guarcello+, 2012)J/ApJS/194/27 : Variable stars in Cygnus OB2 (Henderson+, 2011)J/ApJ/713/871 : X-ray sources in star-forming region Cyg-OB2 (Wright+, 2010)J/ApJS/184/84 : X-ray sources in Cyg OB2 region (Wright+, 2009)J/A+A/486/453 : NIR phot. of early-type stars in Cyg OB2 (Comeron+, 2008)J/A+A/464/211 : Chandra and near-IR obs. of Cyg OB2 (Albacete Colombo+, 2007)J/ApJ/664/1102 : RV survey of Cyg OB2 association (Kiminki+, 2007)J/ApJ/643/238 : Chandra/2MASS sources in Cygnus OB2 (Butt+, 2006)J/ApJS/149/123 : WSRT survey of Cygnus OB2 (Setia Gunawan+, 2003)J/MNRAS/298/753 : Variables in Cygnus OB2 (Pigulski+ 1998)J/AJ/101/1408 : Massive stars in Cyg OB2. (Massey+ 1991)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/751/4https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/751/4http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/751/4https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/751/4https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/751/4http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/751/4GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/751/4/stars (Stars used in the Monte Carlo analysis (table added by CDS))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/751/4/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/751/4/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/751/4/stars?GETtext/xml+votable180.050000true308.74497541.60483890.0055555555555555566/14692 14693 14694https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/751/4?format=asciiOpticaldefaultJ/ApJ/751/4/starsStars used in the Monte Carlo analysis (table added by CDS)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSNameSIMBAD namemeta.id;meta.maincharNameStar designation as in table 1 (G1)meta.idcharprimaryPlotPlot of the velocitiesmeta.ref.urlcharNNumber of velocity measurementsmeta.ref.urlintnullablePapICross-match with Paper I (Cat. J/ApJ/664/1102) and Cat. J/AJ/101/1408, within 10"meta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from SIMBAD names (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD names (declination part)degpos.eq.dec;meta.mainJ/ApJ/751/4/table1Ephemerides for CygOB2 stars used in Monte Carlo analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar designation (G1)meta.id;meta.maincharprimaryHJDHeliocentric Julian Date; HJD-2400000dtime.epochdoubleHRVHeliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRV1{sigma} uncertainty in HRVkm/sstat.errorfloat