  gamma Cassiopeiae (gCas) is a B0.5e star with peculiar X-ray emission
properties and yet the prototype of its own small class. In this paper we
examine the X-ray spectra for a 2004 XMM-Newton observation and a previously
published 2001 Chandra observation. In both cases the spectra can be modeled
with 3 or 4 thermal components, which appear be discrete in temperature and
spatially distinct. The dominant component, having kT ~ 12 keV contributes most
(~80-90%) of the flux. The secondary components have temperatures in the range
of 2-3 keV to 0.1 keV; these values can shift in time. Importantly, we find
that the strong absorption of soft X-rays in 2001 is absent in 2004, meaning
that an absorbing column in front of the source has moved off the star or has
been removed. Other differences include a reduced Fe abundance from the ionized
lines of the FeKalpha complex (even more subsolar than the 2001 observation), a
decrease of the Fe K and possibly of the Si K fluorescence features, and from
the NVII and NeX H-alpha lines, a possible overabundance of N and Ne. Also, we
note common characteristics in both spectra that seem to set gCas apart from
HD110342, another member of this subclass studied in detail. In this sense
these stars have different "personalities." For example, for gCas rapid X-ray
flaring and slower changes in the light curve are only seldomly accompanied by
variations in hardness, and the hot X-ray component remains nearly constant in
temperature. Moreover, the light curve shows recurrent "lulls" in flux,
suggesting that a relaxation cycle is operates as part of the (unknown) X-ray
generation process.
