Journal Article

Study of sdO models: pulsation analysis

C. Rodríguez-López, A. Moya, R. Garrido, J. MacDonald, R. Oreiro and A. Ulla

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 1, pages 295-306
Published in print February 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15750.x
Study of sdO models: pulsation analysis

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We have explored the possibility of driving pulsation modes in models of subluminous O-stars (sdOs), in which the effects of element diffusion, gravitational settling and radiative levitation have been neglected so that the distribution of iron-peak elements remains uniform throughout the evolution. The stability of these models was determined using a non-adiabatic oscillations code. We analysed 27 sdO models from 16 different evolutionary sequences and discovered the first ever sdO models capable of driving high-radial-order g modes. In one model, the driving is by a classical κ mechanism due to the opacity bump from iron-peak elements at temperature ∼200 000 K. In a second model, the driving results from the combined action of κ mechanisms operating in three distinct regions of the star: (i) a carbon–oxygen partial ionization zone at temperature ∼2 × 106 K; (ii) a deeper region at temperature ∼2 × 107 K, which we attribute to ionization of argon, and (iii) at the transition from radiative to conductive opacity in the core of the star.

Keywords: stars: oscillations; stars: variables: other

Journal Article.  8602 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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