  The Rossi X-ray Timing Explorer data of GRS 1915+105 from several observing
periods are modeled with a thermal Comptonization model. Best-fit models
indicate that there is a strong correlation between the inner disk temperature
and the disk luminosity. The hard Comptonized luminosity does not depend
significantly on the total luminosity. The spectral hardness of the Comptonized
radiation, the fraction of seed soft photons scattered by the Comptonizing
cloud, its Thomson optical depth, and the fraction of the total power
dissipated in the optically thin hot plasma, all strongly anticorrelate with
the luminosity. We find that the inner disk radius is almost constant and that
the hot Comptonizing corona shrinks at high luminosities. We note that the fits
using xspec diskbb + power law model underestimate the amplitude of the
blackbody component (and therefore the corresponding size of the emitting
region) and overestimate the absorption column density and the total, corrected
for absorption, luminosity.
