{
  "id": "2404.04248",
  "version": "v1",
  "published": "2024-04-05T17:54:11.000Z",
  "updated": "2024-04-05T17:54:11.000Z",
  "title": "Observation of Gravitational Waves from the Coalescence of a $2.5-4.5~M_\\odot$ Compact Object and a Neutron Star",
  "authors": [
    "The LIGO Scientific Collaboration",
    "the Virgo Collaboration",
    "the KAGRA Collaboration"
  ],
  "comment": "main paper: 14 pages, 8 figures, 2 tables; total with appendices: 34 pages, 14 figures, 7 tables",
  "categories": [
    "astro-ph.HE",
    "gr-qc"
  ],
  "abstract": "We report the observation of a coalescing compact binary with component masses $2.5-4.5~M_\\odot$ and $1.2-2.0~M_\\odot$ (all measurements quoted at the 90% credible level). The gravitational-wave signal GW230529_181500 was observed during the fourth observing run of the LIGO-Virgo-KAGRA detector network on 2023 May 29 by the LIGO Livingston Observatory. The primary component of the source has a mass less than $5~M_\\odot$ at 99% credibility. We cannot definitively determine from gravitational-wave data alone whether either component of the source is a neutron star or a black hole. However, given existing estimates of the maximum neutron star mass, we find the most probable interpretation of the source to be the coalescence of a neutron star with a black hole that has a mass between the most massive neutron stars and the least massive black holes observed in the Galaxy. We estimate a merger rate density of $55^{+127}_{-47}~\\text{Gpc}^{-3}\\,\\text{yr}^{-1}$ for compact binary coalescences with properties similar to the source of GW230529_181500; assuming that the source is a neutron star-black hole merger, GW230529_181500-like sources constitute about 60% of the total merger rate inferred for neutron star-black hole coalescences. The discovery of this system implies an increase in the expected rate of neutron star-black hole mergers with electromagnetic counterparts and provides further evidence for compact objects existing within the purported lower mass gap.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-04-05T17:54:11.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "compact object",
      "gravitational waves",
      "neutron star-black hole merger",
      "observation",
      "merger rate"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}