{
  "id": "2502.19189",
  "version": "v2",
  "published": "2025-02-26T14:55:45.000Z",
  "updated": "2025-06-24T17:20:56.000Z",
  "title": "Fermi detection of gamma-ray Emission from the Hot Coronae of Radio-quiet Active Galactic Nuclei",
  "authors": [
    "Jun-Rong Liu",
    "Jian-Min Wang",
    "Fermi-LAT Collaboration"
  ],
  "comment": "Published in Nature Astronomy",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "Relativistic jets around supermassive black holes (SMBHs) are well-known powerful $\\gamma$-ray emitters. In absence of the jets in radio-quiet active galactic nuclei (AGNs), how the SMBHs work in $\\gamma$-ray bands is still unknown despite of great observational efforts made in the last 3 decades. Considering the previous efforts, we carefully select an AGN sample composed of 37 nearby Seyfert galaxies with ultra-hard X-rays for the goals of $\\gamma$-ray detections by excluding all potential contamination in this band. Adopting a stacking technique, here we report the significant $\\gamma$-ray detection (${\\rm TS}=30.6$, or $5.2\\,\\sigma$) from the sample using 15-year Fermi-Large Area Telescope (LAT) observation. We find an average $\\gamma$-ray luminosity of the sample as $(1.5\\pm1.0)\\times10^{40}{\\,\\rm erg\\,s^{-1}}$ at energies from 1-300\\,GeV. Limited by the well-known pair production from the interaction of $\\gamma$-rays with low energy photons, $\\gtrsim$ several GeV $\\gamma$-rays are found to originate from an extended corona ($\\sim 2.7\\times 10^6\\,R_{\\rm g}$), whereas the canonical much more compact X-ray corona ($\\sim 10\\,R_{\\rm g}$) is responsible for 1 to several GeV $\\gamma$-rays. The finding of the compact region lends to strong supports to the long-time theoretical expectations, but the extended corona is beyond all the existing models. One promising scenario is that the electron-positron pairs produced in the compact X-ray corona would expand as fireball, similar to that in $\\gamma$-ray bursts, forming the structure of extended corona.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2025-06-24T17:20:56.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "radio-quiet active galactic nuclei",
      "gamma-ray emission",
      "hot coronae",
      "fermi detection",
      "compact x-ray corona"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}