BEXCO - Room F(201/202/203/204)
[GA046] GeV gamma-ray, X-ray, and optical monitoring of a radio galaxy NGC 1275
We analyzed Suzaku/XIS data (2006-2015) and Fermi/LAT data (2008-2015) of the gamma-ray emitting radio galaxy NGC 1275 and monitored it with the Kanata optical telescope. A brightening of the nucleus in both the X-ray and GeV gamma-ray energy bands was found in 2013-2015. This is the first evidence of variability with correlation between X-ray and GeV gamma-rays for NGC 1275. We also analyzed Swift/XRT data of NGC 1275 and found that the X-ray flux increased by a factor of 5 in several days in 2006, 2010, and 2013 with a harder X-ray spectrum, indicating that a synchrotron component became brighter. GeV gamma-rays also showed a higher flux with a harder spectrum during the 2010 flare. The simultaneous X-ray and GeV gamma-ray flux increase in the flare could be explained by the shock-in-jet scenario. On the other hand, a long-term gradual brightening of radio, X-ray, and GeV gamma-ray flux with a larger gamma-ray amplitude could originate from other than internal shocks. The optical light curve does not show a clear correlation with GeV gamma-rays, indicating that the disk/corona emission is dominant in the optical band. We also report interesting results using Hitomi/SXS data on NGC 1275.