{
  "id": "2209.10832",
  "version": "v1",
  "published": "2022-09-22T07:37:45.000Z",
  "updated": "2022-09-22T07:37:45.000Z",
  "title": "The Origin of the Photospheric Emission of GRB 220426A",
  "authors": [
    "Xin-Ying Song",
    "Shuang-Nan Zhang",
    "Ming-Yu Ge",
    "Shu Zhang"
  ],
  "comment": "15 pages, 7 figures, accepted for publication in MNRAS on 2022 September 20",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "GRB 220426A is a bright gamma-ray burst (GRB) dominated by the photospheric emission. We perform several tests to speculate the origin of this photospheric emission. The dimensionless entropy $\\eta$ is large, which is not usual if we assume that it is a pure hot fireball launched by neutrino-antineutrino annihilation mechanism only. Moreover, the outflow has larger $\\eta$ with lower luminosity $L$ in the first few seconds, so that the trend of time-resolved $\\eta-L$ can not be described as a monotonically positive correlation between $\\eta$ and $L$. A hybrid outflow with almost completely thermalized Poynting flux could account for the quasi-thermal spectrum as well as large $\\eta$. More importantly, the existence of magnetic field could affect the proton density and neutron-proton coupling effect, so that it could account for the observed trend of time-resolved $\\eta-L$. The other origins for the photospheric emission, such as non-dissipative hybrid outflow or magnetic reconnection, are not supported because their radiation efficiencies are low, which is not consistent with non-detection of the afterglow for GRB 220426A. Therefore, we think the hybrid outflow may be the most likely origin.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-09-22T07:37:45.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "photospheric emission",
      "grb 220426a",
      "hybrid outflow",
      "neutrino-antineutrino annihilation mechanism",
      "bright gamma-ray burst"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}