Suzaku discovery of absorption lines from the black hole transient 4U1630-472

Aya Kubota, Tadayasu Dotani, Jean Cottam, Taro Kotani, Chris Done, Yoshihiro Ueda, Andy C. Fabian, Tomonori Yasuda, Hiromitsu Takahashi, Yasushi Fukazawa, Kazutaka Yamaoka, Kazuo Makishima, Shinya Yamada, Takayoshi Kohmura, Lorella Angelini

Research output: Contribution to journalArticlepeer-review


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 KQ 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 ∼ 10 10 cm assuming a source distance of 10 kpc.

Original languageEnglish
Pages (from-to)225-228
Number of pages4
JournalProgress of Theoretical Physics Supplement
Issue number169
Publication statusPublished - 2007

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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