Raman-scattered O VI features in the symbiotic nova RR Telescopii

Abstract

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 1032Ã and 1038Ã features at 6825Ã and 7082Ã . We present high-resolution optical spectra of RR Tel taken in 2016 and 2017 with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph at 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 $>35\mathrm{km}{\mathrm{s}}^{-1}$, and the corresponding scale < 0.8 au. The best-fit for the Raman profiles is obtained with a mass loss rate of the Mira $\dot{M}\sim 2\times 10^{-6}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ and a wind terminal velocity $v_{\infty }\sim 20\mathrm{km}{\mathrm{s}}^{-1}$. We compare the MIKE data with an archival spectrum taken in 2003 with the Fibre-fed Extended Range Optical Spectrograph (FEROS) at the MPG/ESO 2.2m 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 3811Ã and 3834Ã , 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 1032Ã and 1038Ã emission region.

13 pages, 9 figures, 6 tables, accepted for publication in ApJ