We report broad-band X-ray measurements of the Be star \gamma Cassiopeiae by the BeppoSAX X-ray astronomy satellite .
The observations took place on 1998 July , 18–23 .
The 0.1–200 keV X-ray spectrum is reasonably well fit by an optically thin thermal plasma model of temperature 12.5 \pm 0.6 keV with significant residuals around 0.3 keV and 1 keV .
The former is interpreted as the variable soft component reported by ROSAT , although there is no evidence for variability at the 5 % level .
For a blackbody interpretation , the fitted temperature is 100 \pm ^ { 320 } _ { 13 } eV , in agreement with the ROSAT value of 200 \pm 10 eV .
However , a MEKAL interpretation gives a significantly lower temperature of ( 48 \pm 11 eV ) .
The fitted abundances are about half solar values , in agreement with previous measurements .
At higher energies , the spectrum does not require non-thermal components and the observation of a line at 6.8 keV supports the ASCA interpretation of the source as an accreting white dwarf .
Assuming a source distance of 188 pc , the bolometric luminosity in the 2–10 keV band is 6 \times 10 ^ { 32 } ergs s ^ { -1 } .
Simultaneous optical measurements by the Wendelstein Observatory near Munich , indicate that the source continues to be in a late but rather normal Be phase , with no obvious signs of a transition to the Be-shell phase .
The measured magnitudes at B , V and R wavelengths of 2.18 \pm 0.06 , 2.23 \pm 0.02 and 2.36 \pm 0.03 , respectively , confirm this .