{
  "id": "2109.07694",
  "version": "v1",
  "published": "2021-09-16T03:32:38.000Z",
  "updated": "2021-09-16T03:32:38.000Z",
  "title": "A kilonova from an ultra-quick merger of a neutron star binary",
  "authors": [
    "Zhi-Ping Jin",
    "Hao Zhou",
    "Stefano Covino",
    "Neng-Hui Liao",
    "Xiang Li",
    "Lei Lei",
    "Paolo D'Avanzo",
    "Yi-Zhong Fan",
    "Da-Ming Wei"
  ],
  "comment": "20 pages, 7 figures, 2 tables",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "GRB 060505 was the first well-known nearby (at redshift 0.089) \"hybrid\" gamma-ray burst that has a duration longer than 2 seconds but without the association of a supernova down to very stringent limits. The prompt $\\gamma-$ray flash lasting $\\sim 4$ sec could consist of an intrinsic short burst and its tail emission, but the sizable temporal lag ($\\sim 0.35$ sec) as well as the environment properties led to the widely-accepted classification of a long duration gamma-ray burst originated from the collapse of a massive star. Here for the $ first$ time we report the convincing evidence for a thermal-like optical radiation component in the spectral energy distribution of the early afterglow emission. In comparison to AT2017gfo, the thermal radiation is $\\sim 2$ times brighter and the temperature is comparable at similar epochs. The optical decline is much quicker than that in X-rays, which is also at odds with the fireball afterglow model but quite natural for the presence of a blue kilonova. Our finding reveals a neutron star merger origin of the hybrid GRB 060505 and strongly supports the theoretical speculation that some binary neutron stars can merge ultra-quickly (within $\\sim 1$ Myr) after their formation when the surrounding region is still highly star-forming and the metallicity remains low. Gravitational wave and electromagnetic jointed observations are expected to confirm such scenarios in the near future.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-09-16T03:32:38.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "neutron star binary",
      "ultra-quick merger",
      "long duration gamma-ray burst",
      "neutron star merger origin",
      "binary neutron stars"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}