{
  "id": "1607.02881",
  "version": "v1",
  "published": "2016-07-11T10:02:09.000Z",
  "updated": "2016-07-11T10:02:09.000Z",
  "title": "X-ray spectral and optical properties of a ULX in NGC 4258 (M106)",
  "authors": [
    "Hasan Avdan",
    "Senay Avdan",
    "Aysun Akyuz",
    "Solen Balman",
    "Nazim Aksaker",
    "Inci Akkaya Oralhan"
  ],
  "comment": "10 pages, 8 figures, accepted for publication in ApJ",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We study the X-ray and optical properties of Ultraluminous X-ray source (ULX) X-6 in the nearby galaxy NGC 4258 (M106) based on the archival XMM-Newton, Chandra, Swift, and HST observations. The source has a peak luminosity of $L_{\\mathrm{X}} \\sim 2 \\times 10^{39}$ erg s$^{-1}$ in the XMM-Newton observation of 2004 June. Throughout the X-ray observations, the source seems to exhibit possible spectral variations by considering the hardness ratios and the spectral model parameters. In the HST/ACS images, three optical sources have been identified as counterpart candidates within the 1$\\sigma$ error radius of 0.3 arcsec. The brighter one has an absolute magnitude of M$_{V} \\approx$ $-$7.0 and shows extended structure. The remaining two sources have absolute magnitudes of M$_{V} \\approx$ $-$5.8 and $-$5.3 mag. The possible spectral types of the candidates from brighter to dimmer were determined as B6$-$A5, B0$-$A7 and B2$-$A3, respectively. The counterparts of the X-ray source possibly belong to a young star cluster. Both the standard disk model and the slim disk model do not provide a firm evidence to determine the spectral characteristics of ULX X-6. We argue that the mass for the compact object lies in the range 10-15M$_{\\odot}$ indicating that the compact source is most likely a stellar-mass black hole.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-07-11T10:02:09.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "optical properties",
      "x-ray spectral",
      "absolute magnitude",
      "slim disk model",
      "observation"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}