Raman‐scattered Heii λλ4850, 6545 in the Young and Compact Planetary Nebula IC 5117
| Autor: | Hee-Won Lee, Sang-Hyeon Ahn, Yang-Chan Jung, In-Ok Song |
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| Rok vydání: | 2006 |
| Předmět: |
Physics
Scattering White dwarf Astronomy and Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics Planetary nebula symbols.namesake Emission nebula Space and Planetary Science symbols Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics Emission spectrum H I region Stellar evolution Astrophysics::Galaxy Astrophysics Raman scattering |
| Zdroj: | The Astrophysical Journal. 636:1045-1053 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.1086/498143 |
| Popis: | We report the discovery of He II λλ4850 and 6545 Raman-scattered by atomic hydrogen in the high-resolution spectrum of the very compact and young planetary nebula IC 5117 obtained with the ESPaDOnS (Echelle Spectropolarimetric Device for the Observation of Stars) installed on the 3.6 m Canada-France-Hawaii Telescope. By adopting case B recombination atomic data and considering all the fine-structure emission components, we calculate the weighted averages for the line centers of the Raman-scattered features, as well as those for the emission lines He II λλ4859 and 6560 to determine redward velocity shifts of Δv4850 = +29 km s-1 and Δv6545 = +24 km s-1. We compute the Raman conversion efficiency by a Monte Carlo technique adopting a simple scattering geometry, in which the hot central star is surrounded by a hollow cylindrical H I region characterized by thickness T that is in turn parameterized by the H I column density. It is proposed that the central far-UV emission region is covered significantly by the neutral scattering region characterized by the H I column density N 4 × 1021 cm-2. The H I column density is higher by an order of magnitude than the value proposed from 21 cm radio observations. We briefly discuss the importance of Raman scattering as a probe of neutral material around a newly formed hot white dwarf and the mass-loss process occurring in the late stage of stellar evolution. |
| Databáze: | OpenAIRE |
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