A near-infrared shock wave in the 2006 outburst of recurrent nova RS Ophiuchi

Near-infrared spectra are presented for the recent 2006 outburst of the recurrent nova RS Ophiuchi. We report the rare detection of an infrared shock wave as the nova ejecta plows into the preexisting wind of the secondary in the RS Oph system consisting of a white dwarf (WD) primary and a red giant secondary. The evolution of the shock is traced through a free expansion stage to a decelerative phase. The behavior of the shock velocity with time is found to be broadly consistent with current shock models. The present observations also imply that the WD in the RS Oph system has a high mass indicating that it could be a potential Type Ia supernova (SN Ia) candidate. We also discuss the results from a recent study showing that the near-IR continuum from the recent RS Oph eruption does not originate in an expanding fireball. However, the present work shows that the IR line emission does have an origin in an expanding shock wave.