Raman Scattered He II Features in Symbiotic Satrs and Young Planetary Nebulae

Monday, 30 November 2015 1 p.m. — 2 p.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
HEE-WON LEE (Department of Physics and Astronomy, Sejong University and Gemini South Visiting Astronomer)

He II being a single electron ion, emission lines arising from 2n -> 2 transitions are formed just blueward of HI Lyman series. These He II lines can be Raman scattered by atomic hydrogen to form scattered features blueward of Balmer lines. These features are observed in many symbiotic stars and a number of young planetary nebulae. These objects are characterized by a hot white dwarf surrounded by a thick neutral hydrogen. The covering factor and HI column density of the neutral region are two main factors in the formation of Raman scattered He II features. We present some of our high resolution spectroscopy of these features. As an application we illustrate how these features are used to infer the mass loss rate in the case of the symbiotic star V1016 Cyg.