{
  "id": "2004.14389",
  "version": "v1",
  "published": "2020-04-29T18:00:00.000Z",
  "updated": "2020-04-29T18:00:00.000Z",
  "title": "Primordial mass segregation of star clusters with primordial binaries",
  "authors": [
    "Václav Pavlík"
  ],
  "comment": "11 pages, 2 tables, 9 figures, accepted for publication in Astronomy & Astrophysics",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Observational results of young star-forming regions suggest that star clusters are completely mass segregated at birth. As a star cluster evolves dynamically, these initial conditions are gradually lost. For star clusters with single stars only and a canonical IMF, it has been suggested that traces of these initial conditions vanish at a time $\\tau_\\mathrm{v}$ between $3$ and $3.5\\,t_\\mathrm{rh}$ (initial half-mass relaxation times). Since a significant fraction of stars are observed in binary systems and it is widely accepted that most stars are born in binary systems we investigate what role a primordial binary population (even up to $100\\,\\%$ binaries) plays in the loss of primordial mass segregation of young star clusters. We use numerical $N$-body models similar in size to the Orion Nebula Cluster (ONC) -- a representative of young open clusters -- integrated over several relaxation times to draw conclusions on the evolution of its mass segregation. We also compare our models to the observed ONC. We found that $\\tau_\\mathrm{v}$ depends on the binary star fraction and the distribution of initial binary parameters that include semi-major axis, eccentricity and mass ratio. For instance, in the models with $50\\,\\%$ binaries, we find $\\tau_\\mathrm{v} = (2.7 \\pm 0.8)\\,t_\\mathrm{rh}$, while for $100\\,\\%$ binary fraction, we find a lower value, i.e. $\\tau_\\mathrm{v} = (2.1 \\pm 0.6)\\,t_\\mathrm{rh}$. We also conclude that the initially completely mass segregated clusters, even with binaries, are more compatible with the present-day ONC than the non-segregated ones.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-04-29T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "primordial mass segregation",
      "primordial binary",
      "initial half-mass relaxation times",
      "binary systems",
      "initial conditions"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}