The influence of rotation on optical emission profiles of O stars

ABSTRACT We study the formation of photospheric emission lines in O stars and show that the rectangular profiles, sometimes double peaked, that are observed for some stars are a direct consequence of rotation, and it is unnecessary to invoke an enhanced density structure in the equatorial regions. E...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2012-10, Vol.426 (2), p.1043-1049
Main Authors: Hillier, D. John, Bouret, Jean‐Claude, Lanz, Thierry, Busche, Joseph R.
Format: Article
Language:English
Subjects:
Astrophysics
line: formation
line: profiles
radiative transfer
Sciences of the Universe
Stars & galaxies
stars: atmospheres
stars: early‐type
stars: individual: ζ Puppis
Citations: Items that cite this one
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Summary:ABSTRACT We study the formation of photospheric emission lines in O stars and show that the rectangular profiles, sometimes double peaked, that are observed for some stars are a direct consequence of rotation, and it is unnecessary to invoke an enhanced density structure in the equatorial regions. Emission lines, such as N iv λ4058 and the N iii λλ4634–4640–4642 multiplet, exhibit non‐standard ‘limb‐darkening’ laws. The lines can be in absorption for rays striking the centre of the star and in emission for rays near the limb. Weak features in the flux spectrum do not necessarily indicate an intrinsically weak feature – instead the feature can be weak because of cancellation between absorption in ‘core’ rays and emission from rays near the limb. Rotation also modifies line profiles of wind diagnostics such as He ii λ4686 and Hα and should not be neglected when inferring the actual stratification, level and nature of wind structures.
ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2012.21646.x