{
  "id": "1103.3875",
  "version": "v1",
  "published": "2011-03-20T18:57:07.000Z",
  "updated": "2011-03-20T18:57:07.000Z",
  "title": "Absorption of high-energy gamma rays in Cygnus X-3",
  "authors": [
    "Benoit Cerutti",
    "Guillaume Dubus",
    "Julien Malzac",
    "Anna Szostek",
    "Renaud Belmont",
    "Andrzej Zdziarski",
    "Gilles Henri"
  ],
  "comment": "11 pages, 9 figures, accepted for publication in Astronomy and Astrophysics",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "The microquasar Cygnus X-3 was detected at high energies by the gamma-ray space telescopes AGILE and Fermi. The gamma-ray emission is transient, modulated with the orbital period and seems related to major radio flares, i.e. to the relativistic jet. The GeV gamma-ray flux can be substantially attenuated by internal absorption with the ambient X-rays. In this study, we examine quantitatively the effect of pair production in Cygnus X-3 and put constraints on the location of the gamma-ray source. Cygnus X-3 exhibits complex temporal and spectral patterns in X-rays. During gamma-ray flares, the X-ray emission can be approximated by a bright disk black body component and a non-thermal tail extending in hard X-rays, possibly related to a corona above the disk. We calculate numerically the exact optical depth for gamma rays above a standard accretion disk. Emission and absorption in the corona are also investigated. GeV gamma rays are significantly absorbed by soft X-rays emitted from the inner parts of the accretion disk. The absorption pattern is complex and anisotropic. Isotropization of X-rays due to Thomson scattering in the companion star wind tends to increase the gamma-ray opacity. Gamma rays from the corona suffer from strong absorption by photons from the disk and cannot explain the observed high-energy emission, unless the corona is unrealistically extended. The lack of absorption feature in the GeV emission indicates that high-energy gamma rays should be located at a minimum distance ~10^8-10^10 cm from the compact object. The gamma-ray emission is unlikely to have a coronal origin.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2011-03-20T18:57:07.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high-energy gamma rays",
      "absorption",
      "bright disk black body component",
      "companion star wind tends",
      "gamma-ray emission"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1051/0004-6361/201116581",
      "journal": "Astronomy and Astrophysics",
      "year": 2011,
      "month": "May",
      "volume": 529
    },
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 893261,
      "adsabs": "2011A&A...529A.120C"
    }
  }
}