MODELS FOR THE REMNANTS OF RECURRENT NOVAE .3. COMPARISON WITH THE X-RAY OBSERVATIONS OF RS OPHIUCHI (1985)

Papers I and II in this series developed a model for the interaction of ejecta with a circumstellar medium which was principally applied to the 1985 outburst of the recurrent nova RS Ophiuchi. Here the X-ray emission predicted by this model is compared in detail to EXOSAT observations of the outburst. Fits to the first observations 55 days after outburst lead to values for model parameters which are consistent with existing estimates: outburst energy congruent-to 1.1 x 10(43) erg; ejecta mass congruent-to 1.1 x 10(-6) M.; and mass-loss rate into the wind of the red giant component congruent-to 6 x 10(12) g cm-1. Once these parameters are fixed the model predicts the subsequent evolution of the X-ray emission. Comparison with observations then indicates that account must be taken of the finite nature of the volume filled by pre-shock red giant wind. Numerical calculations are presented of the behaviour of the remnant once the shock breaks out from this confining medium. The subsequent expansion and strong adiabatic cooling result in the required decrease in X-ray flux but at a rate somewhat less than that observed. Suggestions for possible solutions to this problem are briefly discussed.