In this Letter, we report the detection of an emission feature at around 6545 Å in the spectra of the bipolar planetary nebula M2-9 and the symbiotic stars RR Telescopii and He 2-106 and propose to identify it as the He II Raman-scattered feature. This feature was predicted by Nussbaumer, Schmid, & Vogel, who suggested that it was formed through Raman scattering by atomic hydrogen of He II n = 6 → n = 2 photons with a slightly shorter wavelength than that of Ly/β. The scattering cross section, ∼10-20 cm-2 for this process, implies the existence of a neutral hydrogen component with a column density NH1 ∼ 1020 cm-2 around the He II emission regions in these objects, which are believed to be associated with the mass-loss process in the late stage of stellar evolution. Brief discussions on the astrophysical implications of Raman scattering in these objects are presented.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science