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

Research output: Contribution to journalArticle

87 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)585-604
Number of pages20
JournalPublications of the Astronomical Society of Japan
Volume60
Issue number3
Publication statusPublished - 2008

Fingerprint

coronas
corona
continuums
accretion disks
erg
optical thickness
optical depth
flares
inclination
seeds
observatories
observatory
temperature
spectroscopy
accretion
luminosity
electron energy
timescale
seed
iron

Keywords

  • Accretion disks
  • Black hole physics
  • Stars: Individual (cygnus x-1)
  • X-ray: Binaries

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Makishima, K., Takahashi, H., Yamada, S., Done, C., Kubota, A., Dotani, T., ... Yamaoka, K. (2008). Suzaku results on cygnus X-1 in the low/hard State. Publications of the Astronomical Society of Japan, 60(3), 585-604.

Suzaku results on cygnus X-1 in the low/hard State. / Makishima, Kazuo; Takahashi, Hiromitsu; Yamada, Shin'ya; Done, Chris; Kubota, Aya; Dotani, Tadayasu; Ebisawa, Ken; Itoh, Takeshi; Kitamoto, Shunji; Negoro, Hitoshi; Ueda, Yoshihiro; Yamaoka, Kazutaka.

In: Publications of the Astronomical Society of Japan, Vol. 60, No. 3, 2008, p. 585-604.

Research output: Contribution to journalArticle

Makishima, K, Takahashi, H, Yamada, S, Done, C, Kubota, A, Dotani, T, Ebisawa, K, Itoh, T, Kitamoto, S, Negoro, H, Ueda, Y & Yamaoka, K 2008, 'Suzaku results on cygnus X-1 in the low/hard State', Publications of the Astronomical Society of Japan, vol. 60, no. 3, pp. 585-604.
Makishima K, Takahashi H, Yamada S, Done C, Kubota A, Dotani T et al. Suzaku results on cygnus X-1 in the low/hard State. Publications of the Astronomical Society of Japan. 2008;60(3):585-604.
Makishima, Kazuo ; Takahashi, Hiromitsu ; Yamada, Shin'ya ; Done, Chris ; Kubota, Aya ; Dotani, Tadayasu ; Ebisawa, Ken ; Itoh, Takeshi ; Kitamoto, Shunji ; Negoro, Hitoshi ; Ueda, Yoshihiro ; Yamaoka, Kazutaka. / Suzaku results on cygnus X-1 in the low/hard State. In: Publications of the Astronomical Society of Japan. 2008 ; Vol. 60, No. 3. pp. 585-604.
@article{68eb14329eec4547930e21548dcddc90,
title = "Suzaku results on cygnus X-1 in the low/hard State",
abstract = "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.",
keywords = "Accretion disks, Black hole physics, Stars: Individual (cygnus x-1), X-ray: Binaries",
author = "Kazuo Makishima and Hiromitsu Takahashi and Shin'ya Yamada and Chris Done and Aya Kubota and Tadayasu Dotani and Ken Ebisawa and Takeshi Itoh and Shunji Kitamoto and Hitoshi Negoro and Yoshihiro Ueda and Kazutaka Yamaoka",
year = "2008",
language = "English",
volume = "60",
pages = "585--604",
journal = "Publication of the Astronomical Society of Japan",
issn = "0004-6264",
publisher = "Astronomical Society of Japan",
number = "3",

}

TY - JOUR

T1 - Suzaku results on cygnus X-1 in the low/hard State

AU - Makishima, Kazuo

AU - Takahashi, Hiromitsu

AU - Yamada, Shin'ya

AU - Done, Chris

AU - Kubota, Aya

AU - Dotani, Tadayasu

AU - Ebisawa, Ken

AU - Itoh, Takeshi

AU - Kitamoto, Shunji

AU - Negoro, Hitoshi

AU - Ueda, Yoshihiro

AU - Yamaoka, Kazutaka

PY - 2008

Y1 - 2008

N2 - 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.

AB - 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.

KW - Accretion disks

KW - Black hole physics

KW - Stars: Individual (cygnus x-1)

KW - X-ray: Binaries

UR - http://www.scopus.com/inward/record.url?scp=48249151430&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=48249151430&partnerID=8YFLogxK

M3 - Article

VL - 60

SP - 585

EP - 604

JO - Publication of the Astronomical Society of Japan

JF - Publication of the Astronomical Society of Japan

SN - 0004-6264

IS - 3

ER -