Место издания:International Union of Pure and Applied Physics (IUPAP)
Первая страница:2341
Последняя страница:2344
Аннотация:Micro quasars are promising candidates to account for unidentified, but variable EGRET sources at low galactic latitude. support for this hypothesis is given by already claimed associations between unidentified gamma-ray sources and known or recently discovered galactic relativistic jet sources. In contrast to spatial-statistical methods we have analyzed archival data throughout the EGRET mission at positions of six micro quasars using the likelihood source finding algorithm. Preliminary results will be given and compared with existing models which suggest detectable high-energy gamma-ray emission. Micro quasars as sources of high-energy gamma radiation Galactic black hole candidates in X-ray binary systems with relativistic outflows, collectively refereed to as micro quasars [12], have been suggested as either counterparts of persistent gamma-ray sources as exemplified in the associations of 3EG J0241+6103/LSI+61°303 [11,14,15] and 3EG J1824-1514/LS5039 [13], or more generally as potential explanation of unidentified, but variable highenergy gamma-ray sources in the Galactic Plane. A reason to expect high-energy emission can be seen in the existence of a non-thermal emission component extending into IR and even optical wavelength. The same synchrotron-radiating energetic particles will also Compton-scatter photons of the ambient or external medium [2,4]. This is by analogy to what is inferred from AGN, yielding to a 'microblazar' hypothesis if we see a micro quasars jet directed towards us. It is also suggested that one expects significant contributions from upscattered stellar photons from the companion star/donor [10]. In several micro quasars hard X-ray power law components have been detected [3], some indicating a spectral cutoff (GRO J0442+32), others extending well into MeV-energies without any indication of spectral changes (GRO J165540, GRS1915+105) [5,16]. Thermal or bulk-motion Comptonization as responsible emission mechanism is therefore ruled out. At high-energy gamma-rays, a systematic study of 16 LMXB and 4 HMXB found no evidence of periodic or persistent emission above 100 MeV [8], but here we concentrate on exceptional