1995A&A...296..685H

A ROSAT observation of the Be star γ Cas revealed the existence of a variable soft component in the X-ray spectrum. This component can be modeled either by blackbody emission with kT of 200eV or bremsstrahlung with kT around 2keV. The 0.1-0.4keV light curve suggests a possible period of 135.6min for a sinusoidal modulation, with the variation mainly caused by changing photo-electric absorption while the characteristic temperature of the soft spectral component stays constant. The ROSAT spectrum of γ Cas is different to that of X Persei, debilitating the argument that the X-ray source is a neutron star from similarities to the Be/neutron star binary X Persei. The X-ray properties of γ Cas in the ROSAT band resemble more those of magnetic cataclysmic variables suggesting a white dwarf as origin of the X-rays.