2011A&A...530A..63P

Recurrent nova systems like RS Oph have been proposed as a possible channel for type Ia supernova (SN) explosions based on the high mass of the accreting white dwarf. Additional support for this hypothesis has recently been provided by the detection of circumstellar material around SN 2006X and SN 2007le, showing a structure compatible with that expected for recurrent nova outbursts. We investigate the circumstellar environment of RS Oph and its structure with the aim of establishing a firmer and independent link between this class of objects and type Ia SN progenitors. We study the time evolution of CaII, NaI, and KI absorption features in RS Oph before, during, and after the last outburst, using multi-epoch, high-resolution spectroscopy and applying the same method as was adopted for SN 2006X and SN 2007le. A number of components are detected, that are blue-shifted with respect to the systemic velocity of RS Oph. In particular, one feature strongly weakens in the first two weeks after the outburst, at the same time that the very narrow P-Cyg profiles disappear, which are overimposed on the much wider nova emission lines of H, He, FeII, and other elements. We interpret this as the signature of density enhancements in the circumstellar material, suggesting that the recurrent eruptions might indeed create complex structures within the material lost by the donor star. This establishes a strong link between RS Oph and the progenitor system of the type Ia SN 2006X, for which similar features have been detected.