期刊
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
卷 65, 期 2, 页码 -出版社
OXFORD UNIV PRESS
DOI: 10.1093/pasj/65.2.33
关键词
Galaxy: center; ISM: molecular clouds; X-Rays: super-massive black hole; X-ray spectra
资金
- Global COB Program The Next Generation of Physics, Spun from Universality and Emergence from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan
- Japan Society for the Promotion of Science (JSPS)
- JSPS [20340043, 23340047]
- JSPS KAKENHI [23000004, 24540229, 24740123]
- Grants-in-Aid for Scientific Research [24740123, 23340047, 20340043] Funding Source: KAKEN
This paper presents Suzaku results obtained for the Sagittarius (Sgr) C region using the concept of X-ray reflection nebulae (XRNe) as the echo of past flares from a super-massive black hole, Sgr A*. The Sgr C complex is composed of several molecular clouds proximately located in projected distance. The X-ray spectra of Sgr C were analyzed based on the view that XRNe are located inside the Galactic center plasma X-ray emission with an oval distribution around Sgr A*. We found that XRNe are largely separated in the line-of-sight position, and are associated with molecular clouds in different velocity ranges detected by radio observations. We also applied the same analysis to Sgr B XRNe, and completed a long-term light curve for Sgr A* occurring in the past. As a new finding, we determined that Sgr A* has already experienced periods of high luminosity, similar to 500 years ago, which is longer than the previously reported value. Our results are consistent with a scenario that Sgr A* was continuously active with sporadic flux variabilities of L-x = (1-3) x 10(39) erg s(-1) in the past 50 to 500 years. The average past luminosity was approximately 4-6 orders of magnitude higher than that presently observed. In addition, two short-term flares of 5-10 years have been found. Thus, the past X-ray flare should not be a single short-term flare, but can be interpreted as multiple flares superposed on a long-term high state.
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