{
  "id": "1106.0508",
  "version": "v1",
  "published": "2011-06-02T20:33:49.000Z",
  "updated": "2011-06-02T20:33:49.000Z",
  "title": "Early magnetic B-type stars: X-ray emission and wind properties",
  "authors": [
    "L. M. Oskinova",
    "H. Todt",
    "R. Ignace",
    "J. C. Brown",
    "J. P. Cassinelli",
    "W. -R. Hamann"
  ],
  "comment": "20 pages, accepted by MNRAS",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We present a comprehensive study of X-ray emission and wind properties of massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three stars xi1 CMa, V2052 Oph, and zeta Cas. We report the first detection of X-ray emission from V2052 Oph and zeta Cas. The observations show that the X-ray spectra of our program stars are quite soft. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field. We analyze the UV spectra of five non-supergiant B stars with magnetic fields by means of non-LTE iron-blanketed model atmospheres. The latter are calculated with the PoWR code, which treats the photosphere as well as the the wind, and also accounts for X-rays. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high. Our analysis reveals that the magnetic early type B stars studied here have weak winds. The mass-loss rates are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive stronger mass-loss than we empirically infer from the UV spectral lines. (abridged)",
  "revisions": [
    {
      "version": "v1",
      "updated": "2011-06-02T20:33:49.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "x-ray emission",
      "early magnetic b-type stars",
      "wind properties",
      "magnetic early b-type stars",
      "magnetic field"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1111/j.1365-2966.2011.19143.x",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2011,
      "month": "Sep",
      "volume": 416,
      "number": 2,
      "pages": 1456
    },
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 912617,
      "adsabs": "2011MNRAS.416.1456O"
    }
  }
}