| Abstract: | Optical spectroscopic data on the recurrent nova RS Ophiuchi obtained between 32 and 108 days after its last outburst on 1985
January 27 are presented. RS Oph was in the coronal-line phase at that time. The widths of the permitted as well as coronal-lines
decreased continuously. Assuming that the ejected envelope decelerated due to its interaction with circum stellar matter,
its size is deduced as a function of time. Observed fluxes in permitted lines would then imply that the electron density decreased
from 3 × 109 cm#x2212;3 on day 32 to 1.8 × 108 cm-3 on day 108, for an assumed filling factor of 0.01. The helium abundance in the ejecta is estimated to be n(He)/n(H) ∼ 0.16.
The mass of the unshocked ejecta was 3 × 10-6 (Φ/0.01)1/2 M⊙, (at this stage, where f is the filling factor. Observed fluxes in coronal-lines imply that the temperature of coronal-line
region decreased from 1.5 × 106 K on day 32 to 1.1 × 106 K on day 108. Most of the coronal line emission, as well as He n emission arises in shocked and cooling ejecta. This region
is not isothermal, but contains material at a wide range of temperatures. Mass of the shocked ejecta is estimated to be in
the range 10−7−10−6 M⊙ Based on the number of H- and He-ionizing photons, we estimate that the ionizing source evolved from a radius and temperature
of (2 × l012 cm, 3 × 104 K) on day 32 to (6 × l09 cm, 3.6 × 105K) on day 204.
We also present the spectra of RS Oph recorded in quiescent phase, 2 and 3 years after outburst, for comparison. The spectrum
is dominated by that of M2 giant secondary, with superposed emission lines of H and He I |
