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The Coma cluster of galaxies hosts the brightest radio halo known and hastherefore been the target of numerous searches for associated inverse Compton(IC) emission, particularly at hard X-ray energies where the IC signal musteventually dominate over thermal emission. The most recent search with theSuzaku Hard X-ray Detector (HXD) failed to confirm previous IC detections withRXTE and BeppoSAX, instead setting an upper limit 2.5 times below theirnonthermal flux. However, this discrepancy can be resolved if the IC emissionis very extended, beyond the scale of the cluster radio halo. Usingreconstructed sky images from the 58-month Swift BAT all sky survey, thefeasibility of such a solution is investigated. Building on Renaud et al., wetest and implement a method for extracting the fluxes of extended sources,assuming specified spatial distributions. BAT spectra are jointly fit with anXMM-Newton EPIC-pn spectrum derived from mosaic observations. We find noevidence for large-scale IC emission at the level expected from the previouslydetected nonthermal fluxes. For all nonthermal spatial distributionsconsidered, which span the gamut of physically reasonable IC models, wedetermine upper limits for which the largest (most conservative) limit is<4.2x10^{-12} erg/s/cm^2 (20-80 keV), which corresponds to a lower limit on themagnetic field B>0.2uG. A nominal flux upper limit of <2.7x10^{-12} erg/s/cm^2,with corresponding B>0.25uG, is derived for the most probable IC distributiongiven the size of the radio halo and likely magnetic field radial profile.

The Lack of Diffuse, Nonthermal Hard X-ray Emission in the Coma Cluster: The Swift BAT's Eye View