{
  "id": "1806.00015",
  "version": "v1",
  "published": "2018-05-31T18:00:04.000Z",
  "updated": "2018-05-31T18:00:04.000Z",
  "title": "Radio-loudness in black hole transients: evidence for an inclination effect",
  "authors": [
    "S. E. Motta",
    "P. Casella",
    "R. Fender"
  ],
  "comment": "16 pages, 6 figures, accepted for pubblication on MNRAS",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Accreting stellar-mass black holes appear to populate two branches in a radio:X-ray luminosity plane. We have investigated the X-ray variability properties of a large number of black hole low-mass X-ray binaries, with the aim of unveiling the physical reasons underlying the radio-loud/radio-quiet nature of these sources, in the context of the known accretion-ejection connection. A reconsideration of the available radio and X-ray data from a sample of black hole X-ray binaries confirms that being radio-quiet is the more normal mode of behaviour for black hole binaries. In the light of this we chose to test, once more, the hypothesis that radio loudness could be a consequence of the inclination of the X-ray binary. We compared the slope of the `hard-line' (an approximately linear correlation between X-ray count rate and rms variability, visible in the hard states of active black holes), the orbital inclination, and the radio-nature of the sources of our sample. We found that high-inclination objects show steeper hard-lines than low-inclination objects, and tend to display a radio-quiet nature (with the only exception of V404 Cyg), as opposed to low-inclination objects, which appear to be radio-loud(er). While in need of further confirmation, our results suggest that - contrary to what has been believed for years - the radio-loud/quiet nature of black-hole low mass X-ray binaries might be an inclination effect, rather than an intrinsic source property. This would solve an important issue in the context of the inflow-outflow connection, thus providing significant constraints to the models for the launch of hard-state compact jets.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-05-31T18:00:04.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "x-ray binary",
      "black hole transients",
      "inclination effect",
      "stellar-mass black holes appear",
      "hole low-mass x-ray binaries"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}