{
  "id": "1107.3590",
  "version": "v1",
  "published": "2011-07-18T22:28:01.000Z",
  "updated": "2011-07-18T22:28:01.000Z",
  "title": "Spectral and Timing Studies of Cyg X-1 in the Low/Hard State with Suzaku",
  "authors": [
    "Shunsuke Torii",
    "Shin'ya Yamada",
    "Kazuo Makishima",
    "Soki Sakurai",
    "Kazuhiro Nakazawa",
    "Hirofumi Noda",
    "Chris Done",
    "Hiromitsu Takahashi",
    "Poshak Gandhi"
  ],
  "comment": "28 pages, 14 figures",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "From 2005 to 2009, 25 observations of Cyg X-1 were performed with Suzaku, achieving a total exposure of 446 ks. In all observations, the source was found in the low/hard state, while the 1.5--12.0 keV count rate of the All-Sky Monitor onboard RXTE varied by a factor of ~ 3. In each observation, the 10--60 keV HXD-PIN spectrum and the 60--400 keV HXD-GSO spectrum were fitted successfully by a thermal Comptonization model plus reflection by a thick neutral material. As the soft X-ray intensity increased, the Compton y-parameter was found to decrease from 1.0 to 0.6, while the solid angle of reflection to increase by ~ 30%. Also conducted was timing analysis over a frequency range of 0.001--10 Hz. As the source became brighter in soft X-rays, the characteristic frequency of hard X-ray variation increased from 0.03 to 0.3 Hz, while the fractional hard X-ray variation integrated over 0.001--0.01 Hz decreased by a factor of ~ 5. The signals in the 60--200 keV band were generally found to vary on shorter time scales than those in the 10--60 keV band. These spectral and timing results can be consistently interpreted by presuming that increases in the mass accretion rate cause the Comptonizing hot corona to shrink, while the optically-thick disk to intrude deeper therein.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2011-07-18T22:28:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "low/hard state",
      "timing studies",
      "hard x-ray variation",
      "monitor onboard rxte",
      "thermal comptonization model plus reflection"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1093/pasj/63.sp3.S771",
      "journal": "Publications of the Astronomical Society of Japan",
      "year": 2011,
      "month": "Nov",
      "volume": 63
    },
    "note": {
      "typesetting": "TeX",
      "pages": 28,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 919177,
      "adsabs": "2011PASJ...63S.771T"
    }
  }
}