Spectral Analysis ofRossi X‐Ray Timing ExplorerObservations of A3667

Abstract

X-ray emission from the cluster of galaxies A3667 was measured by the Proportional Counter Array and High-Energy X-Ray Timing Experiment experiments on board the Rossi X-Ray Timing Explorer (RXTE) satellite during the period 2001 December-2002 July. Analysis of the ~141 ks RXTE observation and lower energy ASCA Gas Imaging Spectrometer data yields only marginal evidence for a secondary power-law emission component in the spectrum. The 90% confidence upper limit on nonthermal emission in the 15-35 keV band is determined to be 2.6 × 10-12 ergs cm-2 s-1. When combined with the measured radio flux and spectral index of the dominant region of extended radio emission, this upper limit implies a lower limit of ~0.4 μG on the mean, volume-averaged, intracluster magnetic field in A3667.