{
  "id": "1607.07448",
  "version": "v1",
  "published": "2016-07-25T20:00:05.000Z",
  "updated": "2016-07-25T20:00:05.000Z",
  "title": "A 78 Day X-ray Period Detected from NGC 5907 ULX1 by Swift",
  "authors": [
    "D. J. Walton",
    "F. Fuerst",
    "M. Bachetti",
    "D. Barret",
    "M. Brightman",
    "A. C. Fabian",
    "N. Gehrels",
    "F. A. Harrison",
    "M. Heida",
    "M. J. Middleton",
    "V. Rana",
    "T. P. Roberts",
    "D. Stern",
    "L. Tao",
    "N. Webb"
  ],
  "comment": "6 pages, 3 figures, accepted for publication in ApJL",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "We report the detection of a $78.1\\pm0.5$ day period in the X-ray lightcurve of the extreme ultraluminous X-ray source NGC 5907 ULX1 ($L_{\\rm{X,peak}}\\sim5\\times10^{40}$ erg s$^{-1}$), discovered during an extensive monitoring program with Swift. These periodic variations are strong, with the observed flux changing by a factor of $\\sim$3-4 between the peaks and the troughs of the cycle; our simulations suggest that the observed periodicity is detected comfortably in excess of 3$\\sigma$ significance. We discuss possible origins for this X-ray period, but conclude that at the current time we cannot robustly distinguish between orbital and super-orbital variations.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-07-25T20:00:05.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "day x-ray period",
      "extreme ultraluminous x-ray source ngc",
      "day period",
      "x-ray lightcurve",
      "periodic variations"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}