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   81410
   With ASCA, we found a lot of X-ray objects around the Galactic center
   region: black hole candidates, neutron star binaries, X-ray reflection
   nebula, and so on. By studying these objects statistically, we can
   reveal the environment of the Galactic center region. However, there is
   many transient sources at the Galactic center. We must know the duty
   ratio of the transients to investigate the correct number or correct
   distribution of the whole X-ray sources. Then we propose to observe the
   Galactic nucleus Sgr A*. We can study the time variabilities and the
   frequency of transients by this observation. Of course, we also obtain
   very good data about Sgr A* and nearby binary star, AX J1745.6-2901.
   They also can be keys for revealing the environment of the Galactic
   center.
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