2010年4月
Probing the Peculiar Behavior of GRS 1915+105 at Near-Eddington Luminosity
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
- ,
- ,
- 巻
- 62
- 号
- 2
- 開始ページ
- 239
- 終了ページ
- 253
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1093/pasj/62.2.239
- 出版者・発行元
- OXFORD UNIV PRESS
To understand the nature of supercritical accretion, we systematically analyzed the RXTE/PCA data of GRS 1915+105 in its quasi-steady states, by choosing data with small variability during 1999-2000. We applied a multicolor disk plus a thermal Comptonization model, and took into consideration accurate interstellar absorption, a reflection component (with an iron-K emission line), and absorption features from the disk wind self-consistently. The total luminosity ranges from similar to 0.2L(E) to slightly above L-E. There is a strong correlation between the inner disk temperature and the fraction of the disk component. Most of the Comptonization-dominated (> 50% total flux) spectra show T-in similar to 1 keV with a high electron temperature of > 10 keV, which may correspond to the very high state in canonical black hole X-ray binaries (BHBs). In contrast, the disk-dominated spectra have T-in similar to 2 keV with a low temperature (< 10 keV) and optically thick Comptonization, and show two separate branches in the luminosity vs. innermost temperature (L-T-in) diagram. The lower branch clearly follows the L alpha T-in(4)-track. Furthermore, by applying the extended disk blackbody (or p-free disk) model, we found that 9 out of 12 datasets with disk luminosity above 0.3 L-E prefer a flatter temperature gradient than that in the standard disk (p < 0.7). We interpret that, in the lower branch, the disk extends down to the innermost stable circular orbit, and the source is most probably in the slim-disk state. A rapidly spinning black hole can explain both the lack of the L alpha T-in(2)-track and a high value of the spectral hardening factor (similar to 4) that would be required for a non-rotating black hole. The spectra in the upper branch are consistent with the picture of a truncated disk with low-temperature Comptonization. This state was uniquely observed from GRS 1915+105 among BHBs, which may be present at near-Eddington luminosity.
- リンク情報
- ID情報
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- DOI : 10.1093/pasj/62.2.239
- ISSN : 0004-6264
- eISSN : 2053-051X
- CiNii Articles ID : 10026714463
- Web of Science ID : WOS:000279834900005