Open AccessExcitation of g modes in Wolf–Rayet stars by a deep opacity bump
Author(s) -
Townsend R. H. D.,
MacDonald J.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2006.00157.x
Subject(s) - opacity , wolf–rayet star , physics , astrophysics , excited state , envelope (radar) , stars , hydrogen , excitation , atomic physics , optics , telecommunications , radar , quantum mechanics , computer science
We examine the stability of ℓ= 1 and ℓ= 2 g modes in a pair of nitrogen‐rich Wolf–Rayet stellar models characterized by differing hydrogen abundances. We find that modes with intermediate radial orders are destabilized by a κ mechanism operating on an opacity bump at an envelope temperature of log T ≈ 6.25. This ‘deep opacity bump’ is due primarily to L‐shell bound–free transitions of iron. Periods of the unstable modes span ∼11–21 h in the model containing some hydrogen, and ∼3–12 h in the hydrogen‐depleted model. Based on the latter finding, we suggest that self‐excited g modes may be the source of the 9.8‐h periodic variation of WR 123 recently reported by Lefèvre et al.