Compact and diffuse sources in the Galactic Center region

The 10 by 10 degrees region around dynamic center of our Galaxy is known to host a large number of bright X-ray sources, most of which are low mass bi nary systems. While high luminosity Z-sources are especially bright in the standard X-ray band (e.g. 2-10 keV), lower luminosity systems are dominatin g the flux above 30 keV. The two hardest sources in the region, i.e. 1E1740 .7-2942 and GRS 1758-258 are thought to be black hole candidates (BHC) base d on the similarity of spectral properties and short-term variability to th at of dynamically proven BHCs. However, while most of the other galactic BH Cs are known to be transients, these two objects could be considered persis tent though variable sources. The persistent behavior of these sources impl ies some constraints on the parameters of the binary systems. Both sources were detected in the first GRANAT observation of the GC region. They are th e only two persistent BHCs seen in the 35-75 keV SIGMA image after collecti ng several million seconds of exposure time over eight years, indicating th at they are perhaps the only two persistent BHCs in the region. Another peculiar object in the field is of course a putative supermassive b lack hole (Sgr A*) at the dynamic center of our Galaxy. The present day's X -ray luminosity from Sgr A* is very small (less than or similar to 10(36) e rg/s) However an indication that Sgr A* might have been much brighter in th e past was found while studying diffuse X-ray emission in the region. We sp eculate here on how future X-ray observatories may verify the hypothesis of the violent activity of Sgr A* in the past.