We report observation results of the super-soft X-ray sources ( SSS ) CAL87 and RXJ0925.7–4758 with the X-ray CCD cameras ( Solid-state Imaging Spectrometer ; SIS ) on-board the ASCA satellite .
Because of the superior energy resolution of SIS ( \Delta E / E \sim 10 \% at 1 keV ) relative to previous instruments , we could study detailed X-ray spectral structure of these sources for the first time .
We have applied theoretical spectral models to CAL87 , and constrained the white dwarf mass and intrinsic luminosity as 0.8 - 1.2 M _ { \odot } and 4 \times 10 ^ { 37 } – 1.2 \times 10 ^ { 38 } erg s ^ { -1 } , respectively .
However , we have found the observed luminosity is an order of magnitude smaller than the theoretical estimate , which indicates the white dwarf is permanently blocked by the accretion disk , and we are observing a scattering emission by a fully ionized accretion disk corona ( ADC ) whose column density is \sim 1.5 \times 10 ^ { 23 } cm ^ { -2 } .
Through simulation , we have shown that the orbital eclipse can be explained by the ADC model , such that a part of the extended X-ray emission from the ADC is blocked by the companion star filling its Roche lobe .

We have found that very high surface gravity and temperature , \sim 10 ^ { 10 } cm s ^ { -2 } and \sim 100 eV respectively , as well as a strong absorption edge at \sim 1.02 keV , are required to explain the X-ray energy spectrum of RXJ0925.7–4758 .
These values are only possible for an extremely heavy white dwarf near the Chandrasekhar limit .
Although the super soft source luminosity should be \sim 10 ^ { 38 } erg s ^ { -1 } at the Chandrasekhar limit , the observed luminosity of RXJ0925.7–4758 is nearly two orders of magnitude smaller even assuming an extreme distance of \sim 10 kpc .
To explain the luminosity discrepancy , we propose a model that very thick matter which was previously ejected from the system , as a form of jets , intervenes the line of sight , and reduces the luminosity significantly due to Thomson scattering .