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2005ApJ...625..368S - Astrophys. J., 625, 368-384 (2005/May-3)
The FUSE spectrum of the planetary nebula SwSt 1: evidence for inhomogeneities in the gas and dust.
STERLING N.C., DINERSTEIN H.L., BOWERS C.W. and REDFIELD S.
Abstract (from CDS):
We detect nebular absorption at 1040.94 and 1041.69 Å from the two excited fine-structure levels of neutral oxygen. These levels give rise to far-infrared emission lines at 63 and 145 µm, which are often used to infer gas properties, particularly temperature, under the assumption that they are collisionally excited. We find that the O I fine-structure levels in SwSt 1 have an inverted population ratio. This requires a nonthermal excitation mechanism, which we identify as fluorescent excitation by the stellar continuum. To the extent that fluorescence affects the level populations, the far-infrared [O I] line strengths cannot be directly used as diagnostics of density and temperature.
Abstract Copyright: ∼
Journal keyword(s): ISM: Dust, Extinction - Nuclear Reactions, Nucleosynthesis, Abundances - ISM: Planetary Nebulae: General - ISM: Planetary Nebulae: Individual: Alphanumeric: SwSt 1 - Stars: AGB and Post-AGB - Ultraviolet: ISM
Simbad objects: 11
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