Reports on soft excess emission in clusters as observed by Chandra are scarce. Henriksen et al. (2004) detected soft excess emission in the merging cluster Abell 754 (z = 0.0535). Although a non-thermal origin could not be fully excluded, from their combined Chandra, BeppoSAX, ASCA and ROSAT PSPC analysis they conclude that a weak soft thermal component (~ 1 keV) is present in this hot (~ 10 keV) cluster. The emission extends out to 8' from the core and is peaked in the cluster centre. Henriksen et al. attribute the emission to embedded groups of galaxies.
In another cluster, Abell 2163 (z = 0.2030), Henriksen & Hudson (2004) also report a soft and hard X-ray excess in their combined Chandra and ROSAT PSPC analysis. The excess can be modelled by a non-thermal component with photon index 2.7 - 5.9. Little detail about the observations is given in this paper, but the authors attribute the non-thermal emission to a weak merger shock that is present in this cluster.
Bonamente et
al. (2007)
analysed Chandra data of Abell 3112 in the
central 1.0-2.5 arcmin region and found significant soft excess,
reaching 20% of the hot gas emission level at 0.3 keV. Its spectrum
is acceptably fit with a low temperature (~ 0.5 keV) thermal
model or by a non-thermal model
(
ph ~
1.8). The best-fit
values differ from those obtained with XMM-Newton data, indicating
that remaining calibration uncertainties affect fine details.
Nevertheless, the magnitude of the soft excess is above the level of
calibration inaccuracies, and similar to that in XMM-Newton, thus
proving the celestial origin of the soft excess in Abell 3112.