{
  "id": "1203.2156",
  "version": "v1",
  "published": "2012-03-09T18:03:12.000Z",
  "updated": "2012-03-09T18:03:12.000Z",
  "title": "An Updated Look at Binary Characteristics of Massive Stars in the Cygnus OB2 Association",
  "authors": [
    "Daniel C. Kiminki",
    "Henry A. Kobulnicky"
  ],
  "comment": "Accepted for publication in the Astrophysical Journal, 41 pages, 14 figures",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "This work provides a statistical analysis of the massive star binary characteristics in the Cygnus OB2 Association using radial velocity information of 114 B3-O3 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, 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 ~/<4.7 AU). The period distribution for P<27 days is not well reproduced by any single power-law owing to an excess of systems with periods around 3-5 days (0.08-0.31 AU) and a relative shortage of systems with periods around 7-14 days (0.14-0.62 AU). 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 & 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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-03-09T18:03:12.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cygnus ob2 association",
      "binary characteristics",
      "massive star",
      "updated look",
      "binary fraction"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/751/1/4",
      "journal": "The Astrophysical Journal",
      "year": 2012,
      "month": "May",
      "volume": 751,
      "number": 1,
      "pages": 4
    },
    "note": {
      "typesetting": "TeX",
      "pages": 41,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1093404,
      "adsabs": "2012ApJ...751....4K"
    }
  }
}