{
  "id": "astro-ph/9612104",
  "version": "v1",
  "published": "1996-12-10T18:45:28.000Z",
  "updated": "1996-12-10T18:45:28.000Z",
  "title": "X-rays and gamma-rays from accretion flows onto black holes in Seyferts and X-ray binaries",
  "authors": [
    "Andrzej A. Zdziarski",
    "W. Neil Johnson",
    "Juri Poutanen",
    "Pawel Magdziarz",
    "Marek Gierlinski"
  ],
  "comment": "8 pages, 6 figures, to appear in proceedings of the 2nd INTEGRAL workshop \"Transparent Universe\", September 16-20, 1996, St. Malo, France",
  "categories": [
    "astro-ph"
  ],
  "abstract": "We review observations and theoretical models of X-ray/gamma-ray spectra of radio-quiet Seyfert galaxies and of Galactic black-hole candidates (in the hard spectral state). The observed spectra share all their basic components: an underlying power law, a Compton-reflection component with an Fe K-alpha line, low-energy absorption by intervening cold matter, and a high-energy cutoff above ~ 200 keV. The X-ray energy spectral index, alpha, is typically in the range ~ 0.8-1 in Seyfert spectra from Ginga, EXOSAT and OSSE. The hard-state spectra of black-hole candidates Cyg X-1 and GX 339-4 from simultaneous Ginga/OSSE observations have alpha ~ 0.6-0.8. The Compton-reflection component corresponds to cold matter (e.g., inner or outer parts of an accretion disk) covering a solid angle of ~ (0.4-1) times 2 pi as seen from the X-ray source. The spectra are cut off in soft gamma-rays above ~ 200 keV. The broad-band spectra of both Seyferts and black-hole sources are well fitted by Compton upscattering of soft photons in thermal plasmas. Our fits yield the thermal plasma temperature of ~ 100 keV and the Thomson optical depth of tau 1. A fraction of the luminosity emitted nonthermally appears to be small and it can be constrained to < 15% in the Seyfert galaxy NGC 4151. The spectra are cut off before 511 keV, which is strongly suggestive of a thermostatic role of e+e- pair production in constraining the temperature and optical depth of the sources. The source geometry is compatible with a patchy corona above a cold disk in Seyferts, but not in Cyg X-1. In the latter, the relative weakness of reflection is compatible with reflection of emission of a hot inner disk from outer disk regions.",
  "revisions": [
    {
      "version": "v1",
      "updated": "1996-12-10T18:45:28.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "black holes",
      "x-ray binaries",
      "accretion flows",
      "gamma-rays",
      "thermal plasma"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 427244
    }
  }
}