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Session 55 - Galactic Microquasars.
Oral session, Tuesday, January 16
1st Floor, La Villita Assembly Building
Radio jet features commonly seen in quasars have now been observed convincingly in high energy sources in the Galaxy. The two superluminal transient sources (GRS\ 1915+105 and GRO\ J1655--40 = X-ray Nova Scorpius 1994) form a class of galactic jet sources, by their rapid and multi-episodic radio jet ejection and very unusual high energy emission. Their hard X-ray light curves show multiple outbursts, at times with quasi-periodic (in GRO\ J1655-- 40) and with no apparent pattern (GRS\ 1915+105). All radio flares are found to occur in association with hard X-ray transient events; on the other hand, some other hard X-ray transient events do not correspond to any detectable radio activity. Both systems are believed to contain a black hole as the central compact object (the mass function of GRO\ J1655--40>3 M_ødot). Their X-ray and gamma-ray energy spectra, however, differ from other galactic black hole candidates (BHCs) in many aspects, except for the two-component (ultrasoft plus power law hard X-ray tail) spectrum seen in GRO\ J1655--40. Two other galactic jet sources (1E1740--294 and GRS\ 1758--258), also considered BHCs, possibly make another class of galactic jet sources, with their slowly moving radio blobs and very hard high energy emission. Recent high energy observations of these jet sources will be briefly reviewed. We also present the BATSE data for these above mentioned four jet sources and contrast these two possible classes in terms of their different observational characteristics, especially in the high energy band (1--200 keV).
