A 30 h duration EXOSAT observation made in 1985 December is used to ex
amine the X-ray time variability and spectrum of the Be star gamma Cas
siopeiae (X 0053 + 604). We find that the X-ray lightcurve is dominate
d by irregular energy-independent flaring on time-scales greater than
or similar to 100 s. This flaring markedly decreases the sensitivity t
o any periodic signals. We find no evidence for the 6000 s oscillation
s reported by Frontera et al. (1987) from an earlier EXOSAT observatio
n. We suggest that these arise from statistical fluctuations in the re
d noise power. The X-ray spectrum of gamma Cas can either be modeled b
y thermal emission from an optically thin plasma with a temperature of
12 keV, or by a cut-off power-law model with a narrow iron line at an
energy of 6.67 keV. The origin of the X-ray emission in this system r
emains open since its spectral and temporal properties are consistent
with both an accreting neutron star and a white dwarf while its high t
emperature argues against a coronal mechanism.