  The Super Soft Source RX J0925.7--4758 was observed by BeppoSAX LECS and MECS
on January 25--26 1997. The source was clearly detected by the LECS but only
marginally detected by the MECS. We apply detailed Non-Local Thermodynamic
Equilibrium (Non-LTE) models including metal line opacities to the observed
LECS spectrum. We test whether the X-ray spectrum of RX J0925 is consistent
with that of a white dwarf and put constraints upon the effective temperature
and surface gravity by considering the presence or absence of spectral features
such as absorption edges and line blends in the models and the observed
spectrum. We find that models with effective temperatures above ~1e6 K or below
\~7.5e5 K can be excluded. If we assume a single model component for RX J0925
we observe a significant discrepancy between the model and the data above the
NeIX edge energy at 1.19 keV. This is consistent with earlier observations with
ROSAT and ASCA. The only way to account for the emission above ~1.2 keV is by
introducing a second spectral (plasma) component. This plasma component may be
explained by a shocked wind originating from the compact object or from the
irradiated companion star. If we assume log g = 9 then the derived luminosity
is consistent with that of a nuclear burning white dwarf at a distance of ~4
kpc.
