INTEGRAL Observations of the Perseus cluster

TL;DR

This study uses INTEGRAL to observe the Perseus cluster, detecting its X-ray emission and analyzing the presence and variability of a non-thermal component, which appears linked to the central AGN rather than diffuse cluster emission.

Contribution

It provides the first broad-band high-energy spectrum of the Perseus cluster with INTEGRAL, clarifying the nature of the non-thermal emission and its variability.

Findings

Detection of the Perseus cluster up to 120 keV with INTEGRAL.

The non-thermal component is variable and consistent with the AGN NGC 1275.

The non-thermal flux exceeds previous Chandra-based estimates by a factor of 3.

Abstract

We present the results of a 500 ksec observation of the Perseus cluster with INTEGRAL, with the aim of investigating the possible diffuse non-thermal component detected in a previous Chandra observation. In the 3-20 keV band with the JEM-X instrument, we detect the source with high significance and resolve it spatially. Above 20 keV with IBIS/ISGRI, we find that the source is point-like, and the cluster could be detected up to 120 keV. From the broad-band ISGRI/JEM-X spectrum, although we detect a non-thermal component, we find that the high-energy flux is variable and is consistent with the extrapolation of the 2-10 keV flux of the central AGN, NGC 1275. The extrapolation of the non-thermal component claimed from Chandra data exceeds the INTEGRAL spectrum by a factor of 3.