{
  "id": "2102.12983",
  "version": "v1",
  "published": "2021-02-25T16:35:26.000Z",
  "updated": "2021-02-25T16:35:26.000Z",
  "title": "Observations of Her X-1 in low states during SRG/eROSITA all-sky survey",
  "authors": [
    "N. I. Shakura",
    "D. A. Kolesnikov",
    "P. S. Medvedev",
    "R. A. Sunyaev",
    "M. R. Gilfanov",
    "K. A. Postnov",
    "S. V. Molkov"
  ],
  "comment": "10 pages, 7 figures. Accepted to Astronomy & Astrophysics",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "eROSITA (extended ROentgen Survey with an Imaging Telescope Array) instrument onboard the Russian-German `Spectrum-Roentgen-Gamma' (SRG) mission observed the Her X-1/HZ Her binary system in multiple scans over the source during the first and second SRG all-sky surveys. Both observations occurred during a low state of the X-ray source when the outer parts of the accretion disk blocked the neutron star from view. The orbital modulation of the X-ray flux was detected during the low states. We argue that the detected X-ray radiation results from scattering of the emission of the central source by three distinct regions: (a) an optically thin hot corona with temperature $\\sim (2-4) \\times 10^6$ K above the irradiated hemisphere of the optical star; (b) an optically thin hot halo above the accretion disk; and (c) the optically thick cold atmosphere of the optical star. The latter region effectively scatters photons with energies above $5-6$ keV.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-02-25T16:35:26.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "srg/erosita all-sky survey",
      "low state",
      "observations",
      "accretion disk",
      "second srg all-sky surveys"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}