An updated gamma-ray analysis of the Be–BH binary HD 215227
MJ Alexander ; MV McSwain ; - ASI Sponsor
Aug - 2015
DOI: 10.1093/mnras/stv400
ISSN : 1365-2966 ;
journal : Monthly Notices of the Royal Astronomical Society

Volume : 449 ; Issue : 2
type: Article Journal

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) × 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 (∼6 yr). We do not detect AGL J2241+4454 over any of these time periods with Fermi and find upper limits of 1.1 × 10−7 and 5.2 × 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) × 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.

keywords : binaries: general – gamma-rays: stars – stars: black holes – stars:emission-line, Be – stars: black holes – quasars: general

Notes : Acknowledgements These include the National Aeronautics and Space Administrationand the Department of Energy in the United States, theCommissariat `a lEnergie Atomique and the Centre Nationalde la Recherche Scientifique/Institut National de PhysiqueNucl`eaire et de Physique des Particules in France, the AgenziaSpaziale Italiana