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.
Bibliographical noteFunding Information:
We thank the staff at CTIO for their support in the operation of the telescope. We also thank Siek Hyung, who sent us his spectra secured from the Hamilton echelle spectrograph mounted at the Lick 3 m telescope. This work was supported by the Korea Research Foundation grant KRF-1999-115-DP0441.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science