A new spectroscopic orbit for RS Ophiuchi

Abstract

This paper presents a new spectroscopic orbit for the recurrent nova RS Ophiuchi. We analyze echelle spectra obtained during quiescence; some spectra resemble those of A-type stars and some resemble M giant spectra. We derive an orbital period of 460 days for both A-type and M-type absorption features. The A-type features are 0.4P out of phase with the orbit of the M giant. We consider models in which the A-type features can be associated with a hot companion to the M giant, the heated hemisphere of the red giant, or some other component in a binary system. RS Oph is best understood if the A-type features are not associated with either binary component. Our analysis of the orbit and the optical light curve indicates the system has an inclination of 30 deg - 40 deg if the hot component is a Chandrasekhar mass white dwarf.