{
  "id": "1909.05867",
  "version": "v1",
  "published": "2019-09-12T18:00:02.000Z",
  "updated": "2019-09-12T18:00:02.000Z",
  "title": "Jet Propagation in Neutron Star Mergers and GW170817",
  "authors": [
    "Hamid Hamidani",
    "Kenta Kiuchi",
    "Kunihito Ioka"
  ],
  "comment": "25 pages, 10 figures, and 2 tables",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "The gravitational wave event from the binary neutron star (BNS) merger GW170817 and the following multi-messenger observations present strong evidence for i) merger ejecta expanding with substantial velocities and ii) a relativistic jet which had to propagate through the merger ejecta. The ejecta's expansion velocity is not negligible for the jet head motion, which is a fundamental difference from the other systems like collapsars and active galactic nuclei. Here we present an analytic model of the jet propagation in an expanding medium. In particular, we notice a new term in the expression of the breakout time and velocity. In parallel, we perform a series of over a hundred 2D numerical simulations of jet propagation. The BNS merger ejecta is prepared based on numerical relativity simulations of a BNS merger with the highest-resolution to date. We show that our analytic results agree with numerical simulations over a wide parameter space. Then we apply our analytic model to GW170817, and obtain two solid constraints on: i) the central engine luminosity as $L_{iso,0} \\sim 3\\times10^{49}-2.5\\times10^{52}$ erg s$^{-1}$, and on ii) the delay time between the merger and engine activation $t_0-t_m < 1.3$ s. The engine power implies that the apparently-faint \\textit{short} gamma-ray burst (\\textit{s}GRB) \\textit{s}GRB 170817A is similar to typical \\textit{s}GRBs if observed on-axis.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-09-12T18:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "neutron star mergers",
      "jet propagation",
      "analytic model",
      "jet head motion",
      "engine power implies"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 25,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}