Analysis and Interpretation of Hard X‐Ray Emission from the Bullet Cluster (1ES 0657−558), the Most Distant Cluster of Galaxies Observed byRXTE

Evidence for non-thermal activity in clusters of galaxies is well establishedfrom radio observations of synchrotron emission by relativistic electrons. Newwindows in the Extreme Ultraviolet and Hard X-ray ranges have provided for morepowerful tools for the investigation of this phenomenon. Detection of hardX-rays in the 20 to 100 keV range have been reported from several clusters ofgalaxies, notably from Coma and others. Based on these earlier observations weidentified the relatively high redshift cluster 1E0657-56 (also known as RXJ0658-5557) as a good candidate for hard X-ray observations. This cluster, alsoknown as the bullet cluster, has many other interesting and unusual features,most notably that it is undergoing a merger, clearly visible in the X-rayimages. Here we present results from a successful RXTE observations of thiscluster. We summarize past observations and their theoretical interpretationwhich guided us in the selection process. We describe the new observations andpresent the constraints we can set on the flux and spectrum of the hard X-rays.Finally we discuss the constraints one can set on the characteristics ofaccelerated electrons which produce the hard X-rays and the radio radiation.Comment: Accepted by the Astrophysical Journa