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Prog. Theor. Phys. Supplement No.169 (2007) pp. 225-228
Suzaku Discovery of Absorption Lines from the Black Hole Transient 4U1630-472
Aya Kubota,1,*
Tadayasu Dotani,2
Jean Cottam,3
Taro Kotani,4
Chris Done,2,5
Yoshihiro Ueda,6
Andy C. Fabian,7
Tomonori Yasuda,8
Hiromitsu Takahashi,8
Yasushi Fukazawa,8
Kazutaka Yamaoka,9
Kazuo Makishima,1,10
Shinya Yamada,10
Takayoshi Kohmura,11
Lorella Angelini3 and
the Suzaku Team
1Institute of Physical and Chemical Research (RIKEN),
Wako 351-0198, Japan
2Institute of Space and Astronautical Science,
Japan Aerospace Exploration Agency, Sagamihara 229-8510, Japan
3Exploration of the Universe Division,
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
4Department of Physics, Tokyo Tech, Tokyo 152-8551, Japan
5Department of Physics, University of Durham,
South Road, Durham, DH1 3LE, UK
6Department of Astronomy, Kyoto University, Kyoto 606-8502, Japan
7Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
8Department of Physics, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
9Department of Physics, Aoyama Gakuin University, Sagamihara 229-8558, Japan
10Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
11Physics Department, Kogakuin University, Hachioji 192-0015, Japan
Abstract:
We present the results of six Suzaku observations of the recurrent
black hole transient 4U 1630-472 during its decline from its most
recent outburst in 2006. All observations show the typical
high/soft state spectral shape in the 2–50 keV band, roughly described
by an optically thick disk spectrum in the soft energy band plus a weak
power-law tail. The disk
temperature decreases from 1.4 keV to 1.2 keV as the flux decreases by a
factor 2, consistent with a constant radius as expected for
disk-dominated spectra. All the observations reveal significant
absorption lines from highly ionized (H-like and He-like) iron Kα
at 7.0 keV and 6.7 keV.
The energies of these absorption lines suggest a blue shift with
an outflow velocity of ∼1000 km s-1.
The H-like iron Kα equivalent width remains approximately constant
at ∼30 eV over all the observations, while that of the He-like Kα
line increases from 7 eV to 20 eV. Thus the ionization state of the material
decreases, as expected from the decline in flux.
The data constrain the velocity dispersion of the absorber to 200–2000
km s-1, and the size of the plasma as ∼1010 cm
assuming a source distance of 10 kpc.
URL :
http://ptp.ipap.jp/link?PTPS/169/225/
DOI : 10.1143/PTPS.169.225
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