천문학회보 (The Bulletin of The Korean Astronomical Society)
- 제45권1호
- /
- Pages.50.4-51
- /
- 2020
- /
- 1226-2692(pISSN)
Discovery of Raman-scattered He II Features at 6545 Å in Planetary Nebulae NGC 6886 & NGC 6881 from BOES Spectroscopy
- Choi, Bo-Eun (Department of Physics and Astronomy, Sejong University) ;
- Lee, Hee-Won (Department of Physics and Astronomy, Sejong University)
- 발행 : 2020.10.13
초록
We report our discovery of Raman-scattered He II λ6545 feature in young planetary nebulae NGC 6886 and NGC 6881 which indicates the existence of atomic hydrogen components. Considering sharply increasing cross-section of hydrogen atom near the resonance, Raman-scattered He II features are a useful diagnostic tool to investigate the distribution and kinematics of H I region in planetary nebulae. The high-resolution spectroscopic observation was carried out using BOES installed on the 1.8 m telescope of BOAO. We estimate the column density of H I region and its expansion velocity using our grid-based Monte-Carlo radiative transfer code. We assume that the H I region is uniformly distributed in spherical shell geometry with an opening angle and expands with constant speed. Our best-fit model is shown with the column density NHI = 3 × 1020 cm-2 and expansion speed vexp = 25 km s-1 with the opening angle ~ 25° for NGC 6886, and NHI = 4 × 1020 cm-2 and vexp = 30 km s-1 with the opening angle ~ 35° for NGC 6881. We present brief discussions on the late-stage of evolution of stars with mass > 3 M⊙.
키워드