An asteroseismic study of the O9V star HD 46202 from CoRoT space-based photometry

Briquet, M. (1); Aerts, C. (1,2); Baglin, A. (3); Nieva, M. F. (4); Degroote, P. (1); Przybilla, N. (5); Noels, A. (6); Schiller, F. (5); Vuckovic, M. (1); Oreiro, R. (1); Smolders, K. (1); Auvergne, M. (3); Baudin, F. (7); Catala, C. (3); Michel, E. (3); Samadi, R. (3)

1- Instituut voor Sterrenkunde, K.U.Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
2- Department of Astrophysics, IMAPP, University of Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
3- LESIA, CNRS UMR8109, Universite Pierre et Marie Curie, Universite Denis Diderot, Observatoire de Paris, 92195 Meudon Cedex, France
4- Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, Garching bei Munchen D-85741, Germany
5- Dr. Karl Remeis Observatory & ECAP, University of Erlangen-Nuremberg, Sternwartstrasse 7, D-96049 Bamberg, Germany
6- Institut d'Astrophysique et de Geophysique, University of Liege, Bat. B5C, Allee du 6 Aout 17, B-4000 Liege, Belgium
7- Institut d'Astrophysique Spatiale (IAS), Batiment 121, F-91405, Orsay Cedex, France

The O9V star HD 46202, which is a member of the young open cluster NGC 2244, was observed by the CoRoT satellite in October/November 2008 during a short run of 34 days. From the very high-precision light curve, we clearly detect beta Cep-like pulsation frequencies with amplitudes of ~0.1 mmag and below. A comparison with stellar models was performed using a chi^2 as a measure for the goodness-of-fit between the observed and theoretically computed frequencies. The physical parameters of our best-fitting models are compatible with the ones deduced spectroscopically. A core overshooting parameter alpha_ov = 0.10 +- 0.05 pressure scale height is required. None of the observed frequencies are theoretically excited with the input physics used in our study. More theoretical work is thus needed to overcome this shortcoming in how we understand the excitation mechanism of pulsation modes in such a massive star. A similar excitation problem has also been encountered for certain pulsation modes in beta Cep stars recently modelled asteroseismically.

Reference: Astronomy and Astrophysics
Status: Manuscript has been accepted