A theoretical light-curve model for the 1985 outburst of RS Ophiuchi

A theoretical light-curve model of the 1985 outburst of RS Ophiuchi based o n a thermonuclear runaway model is presented. The system consists of a very massive white dwarf (WD) with an accretion disk and a red giant. The early phase of the V light curve is well reproduced only by the bloated WD photo sphere of the thermonuclear runaway model on a 1.35 +/- 0.01 M. WD, while t he later phase is dominated both by the irradiated accretion disk and by th e irradiated red giant underfilling the inner critical Roche lobe. The UV l ight curve is also well reproduced by the same model with a distance of 0.6 kpc to RS Oph. The envelope mass at the optical peak is estimated to be 2 x 10(-6) M,, indicating a rather high mass accretion rate of 1.2 x 10(-7) M . yr(-1) between the 1967 and 1985 outbursts. About 90% of the envelope mas s is blown off in the outburst wind, while the residual 10% (2 x 10(-7) M.) has been left and added to the helium layer of the WD. The net increasing rate of the WD mass is 1.2 x 10(-8) M. yr(-1). Thus, RS Oph is certainly a strong candidate for a Type Ia supernova progenitor.