EDP Sciences
Free access
Issue
A&A
Volume 416, Number 3, March IV 2004
Page(s) 1069 - 1079
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20031731


A&A 416, 1069-1079 (2004)
DOI: 10.1051/0004-6361:20031731

Line-profile variability in the $\beta$ Cephei star $\epsilon$ Centauri

C. Schrijvers1, 2, J. H. Telting3 and C. Aerts4

1  Astronomical Institute Anton Pannekoek, University of Amsterdam, and Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
2  Space Department, TNO TPD, Stieltjesweg 1, 2600 AD Delft, The Netherlands
    e-mail: schrijvers@tpd.tno.nl
3  Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain
4  Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
    e-mail: conny@ster.kuleuven.ac.be

(Received 14 February 2000 / Accepted 9 December 2003)

Abstract
We present an analysis of 530 high-resolution spectra of the $\beta$ Cephei star $\epsilon$ Cen, showing complex variations in the rotationally broadened absorption line-profiles of the Si III triplet ( $\lambda$ 4552, 4567, 4574 Å). Most data were acquired during four dedicated observing runs between April 1996 and June 1998, with time spans between 6 and 14 days.

We calculate velocity moments of the line profiles and apply Fourier analysis techniques to analyze their time behavior. The variations of the velocity moments confirm the presence of two periods already known from photometry, and provide evidence for the presence of two or more non-radial pulsation modes. Our analysis of the spectral time series concentrates on the variability at each position in the $\lambda$ 4567 Å line profile. In addition to the two frequencies found in the radial-velocity variations, we find several other periodicities to be present across the line profile. We use Fourier analysis, sinusoid fitting, and folding techniques to analyze the amplitude and phase information for each of the detected periods. We find evidence for at least five pulsation modes in $\epsilon$ Cen, and identify $\ell$-values between 2 and 5.


Key words: line: profiles -- stars: early-type -- stars: oscillations -- stars: rotation -- stars: variable: other -- stars: individual $\epsilon$ Cen

Offprint request: J. H. Telting, jht@not.iac.es

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