The Hot Component of RS Ophiuchi

Abstract

We analyze optical and ultraviolet spectrophotometry of the quiescent recurrent nova RS Ophiuchi. Our preferred model for this binary consists of an M-type giant and a B-type shell star with a luminosity of Lh˜100-600 Lsun. The ejecta from the recent outburst are slightly enhanced in helium relative to the solar abundance, which agrees with previous estimates from model fits to the optical and ultraviolet light curve. These results indicate that the hot component has a mass close to the Chandrasekhar limit. Although the hot component luminosity is consistent with the high accretion rate needed for recurrent nova eruptions in this system, our effective temperature estimate is not consistent with predicted cooling curves for massive white dwarfs.