X‐Ray Observations of the Coma Cluster in a Broad Energy Band with theINTEGRAL,RXTE, andROSATObservatories

Abstract

We present results of X-ray observations of the Coma Cluster with multiple instruments over a broad energy band. Using the data from the INTEGRAL, RXTE, and ROSAT observatories, we find that the Coma spectrum in the 0.5–107 keV energy band can be well approximated by a thermal plasma emission model with a temperature of T = 8.2 keV. INTEGRAL was used to image the cluster emission in the hard energy band. The cluster is only marginally detectable (~1.6 σ) in the 44–107 keV energy band; however, the raw flux in this band is consistent with the previous results from the BeppoSAX and RXTE observatories. We can exclude with high significance that the hard-band flux reported by BeppoSAX and RXTE could be produced by a single point source. The 20–80 keV flux of a possible nonthermal component in the cluster spectrum is (6.0 ± 8.8) × 10−12 ergs cm−2 s−1. Using the upper limits on nonthermal flux, we obtain a lower limit on magnetic field of 0.1-0.2 μG (depending on the spatial model for a smoothly varying field). We also present a temperature map of the central part of the cluster, which shows significant variations and, in particular, a hot ~11.5 keV region in the extension toward the subcluster infalling from the southwest.