  Classical modelling suggests that, during the RXTE observations studied, GRS
1915+105 was near or above the critical accretion rate and the optically thick
inner disk penetrated inside the advection-dominated flow. The system was very
unstable leading to a rich pattern of variability, e.g. the Rings which might
be characteristic to disk instabilities very close to the innermost stable
orbit (Vilhu and Nevalainen, 1998, ApJ 508, L85). Small values of R_in obtained
require a rapidly rotating Kerr hole, unless the central mass is smaller than
2-3 solar masses. A thermal sombrero provides a reasonable modelling of the
rings, although the broad-band RXTE/OSSE spectrum analysed seems to require a
significant injection of relativistic electrons, the hot phase being not a pure
thermal one. Observations below 2 keV and simultaneous broad-band spectra
between 2--400 keV are needed to better fix the size of the black body disk and
the role of relativistic injection. Further, theoretical work on emerging
spectra of Kerr-holes is required to replace the classical model used.
