{
  "id": "2406.15018",
  "version": "v1",
  "published": "2024-06-21T09:46:19.000Z",
  "updated": "2024-06-21T09:46:19.000Z",
  "title": "X Persei: A study on the origin of its high-energy emission",
  "authors": [
    "J. Rodi",
    "L. Natalucci",
    "M. Fiocchi"
  ],
  "comment": "15 pages, 5 figures, accepted in A&A",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Aims. The origin of the hard X-ray emission in the Be/X-ray binary system X Persei has long been debated as its atypical 'two-hump' spectrum can be modelled in multiple ways. The main debate focuses on the the high-energy hump, which is fit as either a cyclotron resonance scatter frequency (CRSF) or inverse Comptonization due to bulk Comptonization. Methods. Using INTEGRAL/JEM-X and ISGRI data, we studied the temporal and spectral variability in the 3-250 keV energy range during observations over ~15 years. A NuSTAR observation was also included in a joint spectral fit with the INTEGRAL spectrum. Results. We find that the joint spectrum can be described well by a low-energy component due to thermal Comptonization and a high-energy component due to bulk Comptonization, a CRSF, or a cyclotron emission line. The three models begin to diverge above ~120 keV, where statistics are low. Conclusions. We compare our results with observations of other Be/X-ray binaries that show similar 'two-hump' spectra while in a low-luminosity state. As the sources are in a low accretion state, the bulk Comptonization process is likely inefficient, and thus not an explanation for the high-energy component. The broad CRSF (27 +/- 2 keV) in X Persei suggests that the high-energy emission is not due to a CRSF. Thus, the high-energy component is potentially due to cyclotron emission, though other scenarios are not definitively excluded.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-06-21T09:46:19.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high-energy emission",
      "high-energy component",
      "cyclotron resonance scatter frequency",
      "be/x-ray binary system",
      "main debate focuses"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}