Raman-scattered O VI l1032 and He II l1025 and bipolar outflow in the symbiotic star V455 Sco

Jeong-Eun Heo, Francesco Di Mille, Rodolfo Angeloni, Tali Palma, Seok-Jun Chang & Hee-Won Lee

Sejong University, Korea

Raman scattering by atomic hydrogen is a unique spectroscopic process that may probe the mass transfer and mass loss phenomena in symbiotic stars. In the high resolution spectra of the S-type symbiotic star V455 Sco obtained with the Magellan- Clay telescope, we note the presence of two Raman-scattered features, one at around 6825Å with a triple-peak profile formed from Raman scattering of O VI l1032 and the other Raman-scattered He II l1025 at around 6545Å. We transform the Raman O VI feature to the rest frame determined by the optical emission line He I l7065 to find that the line center of the Raman-scattered O VI l6825 feature falls on the dip dividing the blue peak and the central peak. Adopting an accretion flow model with additional contribution from a collimated bipolar outflow, we propose that the blue and central peaks formed via Raman scattering of O VI line photons from the accretion flow and the bipolar flow is responsible for the remaining red peak. With the absence of [N II] l6548, the Raman-scattered He II l1025 at around 6545 Å is immersed in the broad Ha wings that appear to be formed by Raman scattering of far-UV continuum near Lyman series. We provide a simple analysis of the formation of Raman-scattered He II l1025 to show that He II emission is localized to the part of the O VI emission region giving rise to the central peak and also constrain the mass loss rate from the feature.

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