{
  "id": "0910.3954",
  "version": "v1",
  "published": "2009-10-20T20:00:06.000Z",
  "updated": "2009-10-20T20:00:06.000Z",
  "title": "Stellar-mass black holes in star clusters: implications for gravitational wave radiation",
  "authors": [
    "Sambaran Banerjee",
    "Holger Baumgardt",
    "Pavel Kroupa"
  ],
  "comment": "Accepted for publication in MNRAS. 11 pages, 6 figures, 2 color figures",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA",
    "astro-ph.HE"
  ],
  "abstract": "We study the dynamics of stellar-mass black holes (BH) in star clusters with particular attention to the formation of BH-BH binaries, which are interesting as sources of gravitational waves (GW). We examine the properties of these BH-BH binaries through direct N-body simulations of star clusters using the GPU-enabled NBODY6 code. We perform simulations of N <= 10^5 Plummer clusters of low-mass stars with an initial population of BHs. Additionally, we do several calculations of star clusters confined within a reflective boundary mimicking only the core of a massive cluster. We find that stellar-mass BHs with masses ~ 10 solar mass segregate rapidly into the cluster core and form a sub-cluster of BHs within typically 0.2 - 0.5 pc radius, which is dense enough to form BH-BH binaries through 3-body encounters. While most BH binaries are ejected from the cluster by recoils received during super-elastic encounters with the single BHs, few of them harden sufficiently so that they can merge via GW emission within the cluster. We find that for clusters with $N \\ga 5\\times 10^4$, typically 1 - 2 BH-BH mergers occur within them during the first ~ 4 Gyr of evolution. Also for each of these clusters, there are a few escaping BH binaries that can merge within a Hubble time, most of the merger times being within a few Gyr. These results indicate that intermediate-age massive clusters constitute the most important class of candidates for producing dynamical BH-BH mergers. Old globular clusters cannot contribute significantly to the present-day BH-BH merger rate since most of the mergers from them would have occurred earlier. In contrast, young massive clusters are too young to produce significant number of BH-BH mergers. Our results imply significant BH-BH merger detection rates for the proposed \"Advanced LIGO\" GW detector. (Abridged)",
  "revisions": [
    {
      "version": "v1",
      "updated": "2009-10-20T20:00:06.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "stellar-mass black holes",
      "star clusters",
      "gravitational wave radiation",
      "bh-bh merger detection rates",
      "significant bh-bh merger detection"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1111/j.1365-2966.2009.15880.x",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2010,
      "month": "Feb",
      "volume": 402,
      "number": 1,
      "pages": 371
    },
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 834738,
      "adsabs": "2010MNRAS.402..371B"
    }
  }
}