EDP Sciences
Free Access
Issue
A&A
Volume 432, Number 3, March IV 2005
Page(s) 1013 - 1024
Section Stellar structure and evolution
DOI https://doi.org/10.1051/0004-6361:20042103
Published online 07 March 2005


A&A 432, 1013-1024 (2005)
DOI: 10.1051/0004-6361:20042103

A study of bright southern slowly pulsating B stars

III. Mode identification for singly-periodic targets in spectroscopy
P. De Cat1, 2, M. Briquet2, J. Daszynska-Daszkiewicz2, 3, M. A. Dupret4, J. De Ridder2, R. Scuflaire5 and C. Aerts2, 6

1  Royal Observatory of Belgium, Ringlaan 3, 1180 Brussel, Belgium
    e-mail: peter@oma.be
2  Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
3  Astronomical Institute of the Wroclaw University, ul. Kopernika 11, 51-622 Wroclaw, Poland
4  Instituto de Astrofísica de Andalucía, CSIC, Apdo. 3004, 18080 Granada, Spain
5  Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du Six Août 17, 4000 Liège, Belgium
6  Department of Astrophysics, University of Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands

(Received 1 October 2004 / Accepted 30 November 2004)

Abstract
We present the results of the mode identification for a sample of 7 bright southern slowly pulsating B stars showing one pulsation frequency in the $\lambda\lambda$ 413 nm Si II profiles. We combined the results from (1) the method of photometric amplitudes; (2) the moment method; and (3) the amplitude and phase variation across the profile to search for the $\ell$ and m values of the modes best fitting the data. It is the first time that the applicability of these techniques is tested to a sample of main-sequence g-mode pulsators. Combining the moment method with the amplitude and phase variations across the observed line profile gives an improvement in spectroscopic identification of low degree $\ell$ g-mode pulsations. Using the variations of the higher order even moments ${\langle v^4\rangle}$ and ${\langle v^6\rangle}$ of the moment method solutions can also help. For HD 181558, HD 24587, HD 140873 and HD 177863, the photometric and spectroscopic results are compatible and point towards $(\ell,m)$ = (1, +1) sectoral modes. For HD 215573, HD 53921 and HD 92287, the results are inconclusive. Our proposed methodology for mode identification is also applicable to $\gamma$ Doradus stars.


Key words: stars: early-type -- stars: variables: general -- stars: oscillations -- line: profiles

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© ESO 2005

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