Raman-scattered O vi Features in the Symbiotic Nova RR Telescopii

Abstract

RR Telescopii (RR Tel) is an interacting binary system in which a hot white dwarf (WD) accretes matter from a Mira-type variable star via gravitational capture of its stellar wind. This symbiotic nova shows intense Raman-scattered O vi 1032 and 1038 features at 6825 and 7082 Å. We present high-resolution optical spectra of RR Tel taken in 2016 and 2017 with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph at the Magellan-Clay telescope, Chile. We aim to study the stellar wind accretion in RR Tel from the profile analysis of Raman O vi features. With an asymmetric O vi disk model, we derive a representative Keplerian speed of >35 km s −1 , and the corresponding scale <0.8 au. The best fit for the Raman profiles is obtained with a mass-loss rate of the Mira M ̇ ∼ 2 × 10 − 6 M ⊙ yr − 1 and a wind terminal velocity v ∞ ∼ 20 km s −1 . We compare the MIKE data with an archival spectrum taken in 2003 with the Fiber-fed Extended Range Optical Spectrograph at the MPG/ESO 2.2 m telescope. It allows us to highlight the profile variation of the Raman O vi features, indicative of a change in the density distribution of the O vi disk in the last two decades. We also report the detection of O vi recombination lines at 3811 and 3834 Å, which are blended with other emission lines. Our profile decomposition suggests that the recombination of O vii takes place nearer to the WD than the O vi 1032 and 1038 emission region.