This paper presents the Suzaku results obtained for the Sagittarius ( Sgr ) C region using the concept of X-ray reflection nebulae ( XRNe ) as the echo of past flares from the super massive black hole , Sgr A* .
The Sgr C complex is composed of several molecular clouds proximately located in projected distance .
The X-ray spectra of Sgr C were analyzed on the basis of a view that XRNe are located inside the Galactic center plasma X-ray emission with an oval distribution around Sgr A* .
We found that the XRNe are largely separated in the line-of-sight position , and are associated with molecular clouds in different velocity ranges detected by radio observations .
We also applied the same analysis to the Sgr B XRNe and completed a long-term light curve for Sgr A* occurring in the past .
As a new finding , we determined that Sgr A* was experiencing periods of high luminosity already \sim 500 years ago , which is longer than the previously reported value .
Our results are consistent with a scenario that Sgr A* was continuously active with sporadic flux variabilities of L _ { X } = 1 – 3 \times 10 ^ { 39 } erg s ^ { -1 } in the past 50 to 500 years .
The average past luminosity was approximately 4–6 orders of magnitude higher than that presently observed .
In addition , two short-term flares of 5–10 years are found .
Thus , the past X-ray flare should not be a single short-term flare , but can be interpreted as multiple flares superposed on a long-term high state .