科研之友
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摘要
We report an updated analysis of the gamma-ray source AGL J2241+4454 that was detected as a brief two-day flare in 2010 by the AGILE satellite. The high-energy emission of AGL J2241+4454 has been attributed to the binary system HD 215227, which consists of a Be star being orbited by a black hole making it the first known Be-black hole binary system. We have analysed the AGILE data and find a gamma-ray flux of (1.8 +/- 0.7) x 10(-6) ph cm(-2) s(-1), in agreement with the initial report. Additionally, we examined data from the Fermi Large Area Telescope over several time intervals including the two-day flare, the folded orbital phase, and the entire mission (similar to 6 yr). We do not detect AGL J2241+4454 over any of these time periods with Fermi and find upper limits of 1.1 x 10(-7) and 5.2 x 10(-10) ph cm(-2) s(-1) for the flare and the full mission, respectively. We conclude that the HD 215227 Be-black hole binary is not a true gamma-ray binary as previously speculated. While analysing the Fermi data of the AGL J2241+4454 region, we discovered a previously unknown gamma-ray source with average flux of (13.56 +/- 0.02) x 10(-8) ph cm(-2) s(-1) that is highly variable on monthly time-scales. We associate this emission with the known quasar 87GB 215950.2+503417.
- 出版日期2015-5-11
