A theoretical light-curve model for the recurrent nova V394 Coronae Australis

A theoretical light curve for the 1987 outburst of V394 Coronae Australis ( V394 CrA) is modeled to obtain various physical parameters of this recurren t nova. We then apply the same set of parameters to a quiescent phase and c onfirm that these parameters give a unified picture of the binary. Our V394 CrA model consists of a very massive white dwarf (WD), with an accretion d isk (ACDK) having a flaring-up rim, and a lobe-filling, slightly evolved, m ain-sequence star (MS). The model includes irradiation effects of the MS an d the ACDK by the WD. The early visual light curve (t similar to 1-10 days after the optical maximum) is well reproduced by a thermonuclear runaway mo del on a very massive WD close to the Chandrasekhar limit (1.37 +/- 0.01 M. ). The ensuing plateau phase (t similar to 10-30 days) is also reproduced b y the combination of a slightly irradiated MS and a fully irradiated flarin g-up disk with a radius similar to 1.4 times the Roche lobe size. The best- fit parameters are the WD mass similar to 1.37 M., the companion mass simil ar to 1.5 M. (0.8-2.0 M. is acceptable), the inclination angle of the orbit i similar to 65 degrees-68 degrees, and the flaring-up rim similar to 0.30 times the disk radius. The envelope mass at the optical peak is estimated to be similar to 6 x 10(-6) M., which indicates an average mass accretion r ate of similar to 1.5 x 10(-7) M, yr(-1) during the quiescent phase between the 1949 and 1987 outbursts. In the quiescent phase, we properly include t he accretion luminosity of the WD and the viscous luminosity of the ACDK as well as the irradiation effects of the ACDK and MS by the WD. The observed light curve can be reproduced with a disk size of 0.7 times the Roche lobe size and a rather slim thickness of 0.05 times the accretion disk size at the rim. About 0.5 mag sinusoidal variation of the light curve requires a m ass accretion rate higher than similar to 1.0 x 10-7 M, yr(-1), which is co nsistent with the above estimation from the 1987 outburst. These newly obta ined quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae.