Galaxy Clusters in the Swift/BAT era II: 10 more Clusters detected above
  15 keV
  We report on the discovery of 10 additional galaxy clusters detected in the
ongoing Swift/BAT all-sky survey. Among the newly BAT-discovered clusters there
are: Bullet, Abell 85, Norma, and PKS 0745-19. Norma is the only cluster, among
those presented here, which is resolved by BAT. For all the clusters we perform
a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate
the presence of a hard (non-thermal) X-ray excess. We find that in most cases
the clusters' emission in the 0.3-200keV band can be explained by a
multi-temperature thermal model confirming our previous results. For two
clusters (Bullet and Abell 3667) we find evidence for the presence of a hard
X-ray excess. In the case of the Bullet cluster, our analysis confirms the
presence of a non-thermal, power-law like, component with a 20-100 keV flux of
3.4 \times 10-12 erg cm-2 s-1 as detected in previous studies. For Abell 3667
the excess emission can be successfully modeled as a hot component (kT=~13keV).
We thus conclude that the hard X-ray emission from galaxy clusters (except the
Bullet) has most likely thermal origin.
