We report on a BeppoSAX Low-Energy Concentrator Spectrometer ( LECS ) observation of the super-soft source ( SSS ) CAL 83 .
The X-ray emission in SSS is believed to arise from nuclear burning of accreted material on the surface of a white dwarf ( WD ) .
The LECS spectrum of CAL 83 can be well fit by both absorbed blackbody and WD atmosphere models .
If the absorption is constrained to be equal to the value derived from Hubble Space Telescope measurements , then the best-fit blackbody temperature is 46.4 \pm 1.4 eV while a Non Local Thermal Equilibrium ( NLTE ) WD atmosphere model gives a lower temperature of 32.6 \pm 0.7 eV .
In contrast to CAL 87 , there are no strong absorption edges visible in the X-ray spectrum with a 68 % confidence upper limit of 2.3 to the optical depth of a C vi edge at 0.49 keV predicted by WD atmosphere models .
The luminosity and radius derived from the NLTE fit are consistent with the values predicted for stable nuclear burning on the surface of a \sim 0.9–1.0 M _ { \odot } WD .