A BEPPOSAX OBSERVATION OF THE SUPER-SOFT SOURCE CAL-87

We report on a BeppoSAX Concentrator Spectrometer observation of the s uper-soft source (SSS) CAL 87. The X-ray emission in SSS is believed t o arise from nuclear burning of accreted material on the surface of a white dwarf (WD). An absorbed blackbody spectral model gives a chi(ups ilon)(2) of 1.18 and a temperature of 42+/-(13)(11) eV. However, the d erived luminosity and radius are greater than the Eddington limit and radius of a WD, Including an O VIII edge at 0.871 keV gives a signific antly better fit (at >95% confidence) and results in more realistic va lues of the source luminosity and radius. We also fit WD atmosphere mo dels to the CAL 87 spectrum. These also give reasonable bolometric lum inosities and radii in the ranges 2.7-4.8x10(36) erg s(-1) and 8-20x10 (7) cm, respectively. These results support the view that the X-ray em ission from CAL 87 results from nuclear burning in the atmosphere of a WD.