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http://hdl.handle.net/20.500.12386/29551
Titolo: | The Gamma-Ray Source AGL J2241+4454 as the Possible Counterpart of MWC 656 | Autori: | Munar-Adrover, Pere Sabatini, S. PIANO, Giovanni TAVANI, MARCO Nguyen, L. H. LUCARELLI, Fabrizio VERRECCHIA, Francesco PITTORI, Carlotta |
Data pubblicazione: | 2016 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 829 | Fascicolo: | 2 | Abstract: | AGILE discovered the transient source AGL J2241+4454 in 2010, which triggered the study of the associated field allowing for the discovery of the first Be/black hole binary system: MWC 656. This binary was suggested to be the counterpart of AGL J2241+4454, but this association is still not robust. In this work we explore the archival AGILE and Fermi/Large Area Telescope (LAT) data to find more transient events compatible with AGL J2241+4454 and address the possibility to link them to the accretion/ejection processes of MWC 656. We found a total of nine other transient events with AGILE compatible with the position of AGL J2241+4454, besides the 2010 one. We folded these events with the period of the binary system and we could not associate the gamma-ray activity with any particular orbital phase. By stacking the 10 transient events we obtained a spectrum that extends between 100 MeV and 1 GeV, and we fitted it with a power law with a photon index Γ = 2.3 +/- 0.2. We searched the Fermi/LAT data in order to complement the gamma-ray information provided by AGILE but no significant results arose. To investigate this apparent contradiction between these telescopes, we studied the exposure of the field of AGL J2241+4454 in both instruments, and found significant differences. In particular, AGILE exposed, for a longer time and at a lower off-axis angular distance, the field of AGL J2241+4454. This fact, together with the energy-dependent sensitivity of both instruments, and the soft spectrum found in the stacking analysis, might explain why AGILE observed the transient events not seen by Fermi/LAT. | URI: | http://hdl.handle.net/20.500.12386/29551 | URL: | https://iopscience.iop.org/article/10.3847/0004-637X/829/2/101 | ISSN: | 0004-637X | DOI: | 10.3847/0004-637X/829/2/101 | Bibcode ADS: | 2016ApJ...829..101M | Fulltext: | open |
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