{
  "id": "1604.08644",
  "version": "v1",
  "published": "2016-04-28T22:55:28.000Z",
  "updated": "2016-04-28T22:55:28.000Z",
  "title": "Spectro-timing study of GX 339-4 in a hard intermediate state",
  "authors": [
    "F. Fuerst",
    "V. Grinberg",
    "J. A. Tomsick",
    "M. Bachetti",
    "S. E. Boggs",
    "M. Brightman",
    "F. E. Christensen",
    "W. W. Craig",
    "P. Gandhi",
    "B. Grefenstette",
    "C. J. Hailey",
    "F. A. Harrison",
    "K. K. Madsen",
    "M. L. Parker",
    "K. Pottschmidt",
    "D. Stern",
    "D. J. Walton",
    "J. Wilms",
    "W. W. Zhang"
  ],
  "comment": "10 pages, 8 figures; submitted to ApJ, comments welcome",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We present an analysis of NuSTAR energy and power spectra of the transient accreting black hole GX 339-4 taken in January 2015. The observations took place during a hard intermediate state and the source softened significantly over the course of the 1.3 d-long observation. We perform time-resolved spectral analysis by splitting the data into 21 sub-sets and find that the energy spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from ~1.69 to ~1.77 over the course of the observation. We find that the best-fit model requires a harder power-law incident on the reflector than that observed as primary continuum. The accretion disk is truncated at around 9 gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which changes in frequency from ~0.68 to ~1.05 Hz over the course of the observation. The frequency change is very well correlated with the softening of the power-law continuum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of ~100M_sun, which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii is difficult to reconcile with current models.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-04-28T22:55:28.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "hard intermediate state",
      "inner accretion disk radius",
      "accreting black hole gx",
      "spectro-timing study",
      "relativistically blurred reflection component"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2016arXiv160408644F",
      "inspire": 1454056
    }
  }
}