{
  "id": "2010.07616",
  "version": "v1",
  "published": "2020-10-15T09:21:59.000Z",
  "updated": "2020-10-15T09:21:59.000Z",
  "title": "Population III Binary Black Holes: Effects of Convective Overshooting on Formation of GW190521",
  "authors": [
    "Ataru Tanikawa",
    "Tomoya Kinugawa",
    "Takashi Yoshida",
    "Kotaro Hijikawa",
    "Hideyuki Umeda"
  ],
  "comment": "6 pages, 5 figures, 1 table",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "GW190521 is a merger of two black holes (BHs), at least one of which is in so-called the pair-instability (PI) mass gap, and should be hard to form due to effects of PI supernovae (SNe) and pulsational PI (PPI). We study the formation of GW190521-like BH-BHs under Population (Pop.) III environments by binary population synthesis (BPS) calculations. We reveal that convective overshooting in stellar evolution strongly affects the formation of GW190521-like BH-BHs. A model with a small overshoot parameter (similar to GENEC) can form GW190521-like BH-BHs. The derived merger rate is $4 \\times 10^{-2}$ yr$^{-1}$ Gpc$^{-3}$ at redshift of $\\sim 0.82$, comparable to the merger rate of GW190521-like BH-BHs inferred by gravitational wave observations. In this model, a $\\sim 90 M_\\odot$ star can collapse to a $\\sim 90 M_\\odot$ BH avoiding PPI and PISN even if it is a member of a binary star. This is because it expands up to $\\sim 10^2 R_\\odot$, and lose little mass through binary evolution. However, a model with a large overshoot parameter (similar to Stern) cannot form GW190521-like BH-BHs at all. We cannot conclude that a Pop. III binary is the origin of GW190521, since the correct overshoot parameter is highly uncertain. If a Pop. III binary is the origin of GW190521, the merger rate of BH-BHs including a $100-135 M_\\odot$ BH is much smaller than that of GW190521-like BH-BHs. This will be assessed by gravitational wave observations in the near future.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-10-15T09:21:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "binary black holes",
      "convective overshooting",
      "gravitational wave observations",
      "overshoot parameter",
      "merger rate"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}