Oral Presentation

Suzaku Observation of the Black Hole Binary 4U 1630-47 in the Very High State

Takafumi Hori, Yoshihiro Ueda, Megumi Shidatsu, Taiki Kawamuro(Kyoto University), Aya Kubota(Shibaura Institute of Technology), Chris Done(University of Durham), Satoshi Nakahira(ISAS)

The best objects to study the physics of accretion flow onto a black hole are stellar-mass black hole binaries (BHBs) in our Galaxy. When the accretion rate approaches to the Eddington limit, BHBs takes the ``very high state'' (VHS), where X-ray spectra are characterized by strong Comptonization. Although the VHS is a key state to understand supper-critical accretion, the structure of the innermost accretion disk is poorly understood because it is rarely observed. Here we report the results from a Suzaku observation of the Galactic black hole binary 4U 1630--47 in the VHS during the 2012 outburst. From detailed spectral analysis, we find marginal evidence that the standard disk is truncated at a slightly larger radius than the innermost stable circular orbit. This suggests that the innermost part of the accretion disk made a transition from the standard disk into another state. D{\'{\i}}az Trigo et al. (2013) report evidence for the presence of baryonic jets from an observation with XMM-Newton during this outburst. Although this observation was performed only four days before Suzaku observation and the source was in a similar state, our X-ray spectra do not show the Doppler-shifted iron emission lines indicating a baryonic jet. We discuss the physical conditions of the accretion flow and baryonic jets of 4U 1630--47 in the VHS.