  Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray
emission. The Suzaku observatory detected six rapid X-ray spectral hardening
events called "softness dips" in a ~100 ksec duration observation in 2011. All
the softness dip events show symmetric softness ratio variations, and some of
them have flat bottoms apparently due to saturation. The softness dip spectra
are best described by either ~40% or ~70% partial covering absorption to kT ~12
keV plasma emission by matter with a neutral hydrogen column density of ~2-8e21
cm-2, while the spectrum outside of these dips is almost free of absorption.
This result suggests the presence of two distinct X-ray emitting spots in the
gamma Cas system, perhaps on a white dwarf companion with dipole mass
accretion. The partial covering absorbers may be blobs in the Be stellar wind,
the Be disk, or rotating around the white dwarf companion. Weak correlations of
the softness ratios to the hard X-ray flux suggest the presence of stable
plasmas at kT ~0.9 and 5 keV, which may originate from the Be or white dwarf
winds. The formation of a Be star and white dwarf binary system requires mass
transfer between two stars; gamma Cas may have experienced such activity in the
past.
