X-Ray and Optical Monitoring of a Gamma-Ray-Emitting Radio Galaxy, NGC 1275

Abstract

Abstract We performed monitoring observations of a gamma-ray-emitting radio galaxy, NGC 1275, in the X-ray and optical bands with the Suzaku/XIS, Kanata telescope, and the Okayama telescope. The X-ray flux of the nucleus was estimated by imaging spectroscopy in the hard X-ray band. In the optical band, a continuum flux, a broad H$ \alpha$ line flux, and the polarization degree were measured. We could not find any time variability of the X-ray (2006–2011) and optical continuum (2010–2011) within 30%, regardless of the recent radio and gamma-ray variability by a factor of 3. The observed optical polarization was very small at $ \sim$ 0.4% and showed little variability; it would be mostly of interstellar origin within our Galaxy. Furthermore, we confirmed with the XMM-Newton data that the X-ray spectrum of NGC 1275 in 2006 exhibited the Fe-K line, whose equivalent width was typical for other radio and Seyfert galaxies. These results indicate that the jet emission is not a major component in the optical and X-ray bands. Following these results, we discuss the jet emission of NGC 1275.