We report on a BeppoSAX Concentrator Spectrometer observation of the super-soft source ( SSS ) CAL 87 .
The X-ray emission in SSS is believed to arise from nuclear burning of accreted material on the surface of a white dwarf ( WD ) .
An absorbed blackbody spectral model gives a \chi _ { { \nu } } ^ { 2 } of 1.18 and a temperature of 42 \pm ^ { 13 } _ { 11 } eV .
However , the derived 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 significantly better fit ( at > 95 % confidence ) and results in more realistic values of the source luminosity and radius .
We also fit WD atmosphere models to the CAL 87 spectrum .
These also give reasonable bolometric luminosities and radii in the ranges 2.7–4.8 \times 10 ^ { 36 } erg s ^ { -1 } and 8–20 \times 10 ^ { 7 } cm , respectively .
These results support the view that the X-ray emission from CAL 87 results from nuclear burning in the atmosphere of a WD .