Suzaku results on cygnus X-1 in the low/hard State

Kazuo Makishima, Hiromitsu Takahashi, Shin'ya Yamada, Chris Done, Aya Kubota, Tadayasu Dotani, Ken Ebisawa, Takeshi Itoh, Shunji Kitamoto, Hitoshi Negoro, Yoshihiro Ueda, Kazutaka Yamaoka

研究成果: Article査読

93 被引用数 (Scopus)

抄録

The black-hole binary Cygnus X-1 was observed for 17 ks with the Suzaku X-ray observatory in 2005 October, while it was in a low/hard state with a 0.7-300keV luminosity of 4.6 × 1037 erg s-1. The XIS and HXD spectra, spanning 0.7-400 keV, were reproduced successfully, incorporating a cool accretion disk and a hot Comptonizing corona. The corona is characterized by an electron temperature of ∼ 100 keV, and two optical depths of ∼0.4 and ∼ 1.5, which account for the softer and harder continua, respectively. The disk has an innermost temperature of ∼ 0.2keV, and is thought to protrude half way into the corona. The disk not only provides seed photons to the Compton cloud, but also produces a soft spectral excess, a mild reflection hump, and a weakly broadened iron line. A comparison with the Suzaku data on GRO J1655-40 reveals several interesting spectral differences, which can mostly be attributed to inclination effects, assuming that the disk has a flat geometry while the corona is grossly spherical. An intensity-sorted spectroscopy indicates that the continuum becomes less Comptonized when the source flares up on time scales of 1-200 s, while the underlying disk remains unchanged.

本文言語English
ページ(範囲)585-604
ページ数20
ジャーナルPublications of the Astronomical Society of Japan
60
3
DOI
出版ステータスPublished - 2008

ASJC Scopus subject areas

  • 天文学と天体物理学
  • 宇宙惑星科学

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