EDP Sciences
Free Access
Volume 399, Number 2, February IV 2003
Page(s) 639 - 645
Section Stellar atmospheres
DOI https://doi.org/10.1051/0004-6361:20021750

A&A 399, 639-645 (2003)
DOI: 10.1051/0004-6361:20021750

Spectroscopic mode identification for the $\beta\,$Cephei star EN (16) Lacertae

C. Aerts1, H. Lehmann2, M. Briquet3, R. Scuflaire3, M. A. Dupret3, J. De Ridder1 and A. Thoul3

1  Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
2  Thüringer Landessternwarte, 07778 Tautenburg, Germany
3  Institut d'Astrophysique et de Géophysique de Liège, Université de Liège, allée du Six Août 17, 4000 Liège, Belgium

(Received 15 October 2002 / Accepted 21 November 2002 )

We perform for the first time spectroscopic mode identification in the eclipsing binary $\beta\,$Cephei star EN (16) Lac. This mode identification is based upon a time series of 942 line profiles of the He I $\lambda\lambda$ 6678 Å line in its spectrum. All three known frequencies f1, f2, f3 of the star are present in the line-profile variations, but we failed to find additional modes. Using different identification methods we find conclusive evidence for the radial nature of the main mode and for the $\ell=2, m=0$ identification of the mode with frequency f2. A unique identification of the third mode is not possible from the spectra, but we do derive that $\ell_3<3$. Fits to the amplitude and phase variability of the modes imply a rotation frequency between 0.1 and 0.4 c d -1. The star's rotation axis is not aligned with the orbital axis.

Key words: stars: binaries: spectroscopic -- stars: variables: early-type -- stars: individual: EN(16) Lac

Offprint request: C. Aerts, conny@ster.kuleuven.ac.be

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