Suzaku Discovery of Absorption Lines from the Black Hole Transient 4U1630-472(Chapter 9. Stellar/Intermediate Mass Black Holes, The Extreme Universe in the Suzaku Era)

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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 2-50keV 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 1.4keV to 1.2keV 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 Ka at 7.0keV and 6.7keV. The energies of these absorption lines suggest a blue shift with an outflow velocity of〜1000km s^<-1>. The H-like iron Kα equivalent width remains approximately constant at〜30eV over all the observations, while that of the He-like Kα line increases from 7eV to 20eV. 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 200-2000km s^<-1>, and the size of the plasma as〜10^<10> cm assuming a source distance of 10kpc.
理論物理学刊行会の論文
2007-12-19