Rossi X-Ray Timing Explorer hard X-ray observation of Abell 754: Constraining the hottest temperature component and the intracluster magnetic field

Abell 754, a cluster undergoing merging, was observed in hard X-rays with t he Rossi X-Ray Tinting Explorer (RXTE) in order to constrain its hottest te mperature component and search for evidence of nonthermal emission. Simulta neous modeling of RXTE data and those taken with previous missions yields a n average intracluster temperature of similar to 9 keV in the 1-50 keV ener gy band. A multitemperature component model derived from numerical simulati ons of the evolution of a cluster undergoing a merger produces similar qual ity of fit, indicating that the emission measure from the very hot gas comp onent is sufficiently small that it renders the two models indistinguishabl e. No significant nonthermal emission was detected. However, our observatio ns set an upper limit of 7.1 x 10(-14) ergs cm(-2) s(-1) keV(-1) (90% confi dence limit) to the nonthermal emission flux at 20 keV. Combining this resu lt with the radio synchrotron emission flux, we find a lower limit of 0.2 m u G for the intracluster magnetic held. We discuss the implications of our results for the theories of magnetic held amplifications in cluster mergers .