{
  "id": "1607.03293",
  "version": "v1",
  "published": "2016-07-12T10:08:30.000Z",
  "updated": "2016-07-12T10:08:30.000Z",
  "title": "Two giant outbursts of V 0332+53 observed with INTEGRAL",
  "authors": [
    "C. Ferrigno",
    "L. Ducci",
    "E. Bozzo",
    "P. Kretschmar",
    "M. Kühnel",
    "C. Malacaria",
    "K. Pottschmidt",
    "A. Santangelo",
    "V. Savchenko",
    "J. Wilms"
  ],
  "comment": "Accepted for publication on A&A",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "In July 2015, the high-mass X-ray binary V 0332+53 underwent a giant outburst, a decade after the previous one. This system hosts a strongly magnetized neutron star. During the 2004--2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. The long ($\\approx 100$ d) and bright ($L_{\\rm x} \\approx 10^{38}$ erg s$^{-1}$) 2015 outburst offered the opportunity to study during another outburst the unique properties of the fundamental CRSF and its dependence on the X-ray luminosity. The source was observed by the INTEGRAL satellite for $\\sim 330$ ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004--2005 and left unpublished so far. We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the $3-100$ keV luminosity of $E_1 \\propto -0.095(8)L_{37}$ keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004--2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data we also report on the detection of a $\\sim 34$ d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-07-12T10:08:30.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "giant outburst",
      "fundamental crsf",
      "x-ray luminosity",
      "joint european x-ray monitors",
      "centroid energy"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}