  We present spatially-resolved spectroscopy of the galaxy cluster Abell S1101,
also known as Sersic 159-03, with Chandra, XMM-Newton and ROSAT, and
investigate the presence of soft X-ray excess emission above the contribution
from the hot intra-cluster medium. In earlier papers we reported an extremely
bright soft excess component that reached 100% of the thermal radiation in the
R2 ROSAT band (0.2-0.4 keV), using the HI column density measurement by Dickey
and Lockman. In this paper we use the newer Leiden-Argentine-Bonn survey
measurements of the HI column density towards Abell S1101, significantly lower
than the previous value, and show that the soft excess emission in Abell S1101
is now at the level of 10-20% of the hot gas emission, in line with those of a
large sample of clusters analyzed by Bonamente et al. in 2002. The ROSAT soft
excess emission is detected regardless of calibration uncertainties between
Chandra and XMM-Newoton. This new analysis of Abell S1101 indicate that the
1/4keV band emission is compatible with the presence of WHIM filaments
connected to the cluster and extending outward into the intergalactic medium;
the temperatures we find in this study are typically lower than the WHIM probed
in other X-ray studies. We also show that the soft excess emission is
compatible with a non-thermal origin as the inverse Compton scattering of
relativistic electrons off the cosmic microwave background, with pressure less
than 1% of the thermal electrons.
