Suzaku X-Ray Monitoring of Gamma-Ray-Emitting Radio Galaxy, NGC 1275

TL;DR

This study reports the first observed X-ray variability in NGC 1275 correlated with gamma-ray activity, using Suzaku/XIS monitoring, suggesting a jet-related origin of high-energy emissions in this radio galaxy.

Contribution

It provides new evidence of X-ray variability in NGC 1275 correlated with gamma-ray flux increase, highlighting the importance of multi-wavelength monitoring for understanding emission mechanisms.

Findings

X-ray flux increased during gamma-ray activity in 2013-2014

First evidence of X-ray variability in NGC 1275

Correlation between X-ray and gamma-ray fluxes observed

Abstract

NGC 1275 is a gamma-ray-emitting radio galaxy at the center of the Perseus cluster. Its multi-wavelength spectrum is similar to that of blazers, and thus a jet-origin of gamma-ray emissions is believed. In the optical and X-ray region, NGC 1275 also shows a bright core, but their origin has not been understood, since a disk emission is not ruled out. In fact, NGC 1275 exhibits optical broad emission lines and a X-ray Fe-K line, which are typical for Seyfert galaxies. In our precious studies of NGC 1275 with Suzaku/XIS, no X-ray time variability was found from 2006 to 2011, regardless of moderate gamma-ray variability observed by {it Fermi}-LAT~\cite{Yamazaki}. We have continued monitoring observations of NGC 1275 with Suzaku/XIS. In 2013-2014, MeV/GeV gams-ray flux of NGC 1275 gradually increased and reached the maximum at the beginning of 2014. Correlated with this recent gamma-ray activity, we found that X-ray flux also increased, and this is the first evidence of X-ray variability of NGC 1275. Following these results, we discuss the emission component during the time variability, but we cannot decide the origin of X-ray variability correlating with gamma-ray. Therefore, for future observation, it is important to observe NGC 1275 by using Fermi gamma-ray, XMM-Newton, NuStar, ASTRO-H X-ray, CTA TeV gamma-ray and Kanata optical telescope.