Journal Article

The influence of rotation on optical emission profiles of O stars

D. John Hillier, Jean-Claude Bouret, Thierry Lanz and Joseph R. Busche

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 2, pages 1043-1049
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21646.x
The influence of rotation on optical emission profiles of O stars

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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.

Keywords: line: formation; line: profiles; radiative transfer; stars: atmospheres; stars: early-type; stars: individual: ζ Puppis

Journal Article.  4277 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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