{
  "id": "2208.08930",
  "version": "v1",
  "published": "2022-08-18T16:05:52.000Z",
  "updated": "2022-08-18T16:05:52.000Z",
  "title": "The long stare at Hercules X-1 -- I. Emission lines from the outer disk, the magnetosphere boundary and the accretion curtain",
  "authors": [
    "P. Kosec",
    "E. Kara",
    "A. C. Fabian",
    "F. Furst",
    "C. Pinto",
    "I. Psaradaki",
    "C. S. Reynolds",
    "D. Rogantini",
    "D. J. Walton",
    "R. Ballhausen",
    "C. Canizares",
    "S. Dyda",
    "R. Staubert",
    "J. Wilms"
  ],
  "comment": "Accepted for publication in ApJ. 26 pages, 17 figures, 4 tables",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Hercules X-1 is a nearly edge-on accreting X-ray pulsar with a warped accretion disk, precessing with a period of about 35 days. The disk precession allows for unique and changing sightlines towards the X-ray source. To investigate the accretion flow at a variety of sightlines, we obtained a large observational campaign on Her X-1 with XMM-Newton (380 ks exposure) and Chandra (50 ks exposure) for a significant fraction of a single disk precession cycle, resulting in one of the best datasets taken to date on a neutron star X-ray binary. Here we present the spectral analysis of the High State high-resolution grating and CCD datasets, including the extensive archival data available for this famous system. The observations reveal a complex Fe K region structure, with three emission line components of different velocity widths. Similarly, the high-resolution soft X-ray spectra reveal a number of emission lines of various widths. We correct for the uncertain gain of the EPIC-pn Timing mode spectra, and track the evolution of these spectral components with Her X-1 precession phase and observed luminosity. We find evidence for three groups of emission lines: one originates in the outer accretion disk (10^5 RG from the neutron star). The second line group plausibly originates at the boundary between the inner disk and the pulsar magnetosphere (10^3 RG). The last group is too broad to arise in the magnetically-truncated disk and instead must originate very close to the neutron star surface, likely from X-ray reflection from the accretion curtain (~10^2 RG).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-08-18T16:05:52.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "emission line",
      "accretion curtain",
      "outer disk",
      "long stare",
      "magnetosphere boundary"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 26,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}