ARossi X‐Ray Timing ExplorerStudy of M87 and the Core of the Virgo Cluster

We present hard X-ray observations of the nearby radio galaxy M87 and the core of the Virgo cluster using the Rossi X-ray Timing Explorer. These are the first hard X-ray observations of M87 not affected by contamination from the nearby Seyfert 2 galaxy NGC4388. Thermal emission from Virgo's intracluster medium is clearly detected and has a spectrum that is well described by a kT=2.7keV thermal plasma component together with a cooler kT=0.4keV component. No non-thermal (power-law) emission from M87 is detected in the hard X-ray band, with fluctuations in the Cosmic X-ray Background being the limiting factor. Combining with ROSAT data, we infer that the X-ray spectrum of the M87 core and jet must be steep (Gamma_core>1.75 and Gamma_jet>1.60), and we discuss the implications of this result. Our hard X-ray limits are also inconsistent with the non-thermal electron model for the extreme ultraviolet excess observed in Virgo by the Extreme Ultraviolet Explorer.