EDP Sciences
Free access
Volume 392, Number 1, September II 2002
Page(s) 151 - 159
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020911

A&A 392, 151-159 (2002)
DOI: 10.1051/0004-6361:20020911

Photometric amplitudes and phases of nonradial oscillation in rotating stars

J. Daszynska-Daszkiewicz1, 2, W. A. Dziembowski2, 3, A. A. Pamyatnykh2, 4 and M.-J. Goupil5

1  Astronomical Institute of the Wroclaw University, ul. Kopernika 11, 51-622 Wroclaw, Poland
2  Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
3  Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
4  Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya Str. 48, 109017 Moscow, Russia
5  DASGAL, UMR CNRS 8633, Observatoire de Paris-Meudon, France

(Received 28 May (2002) / Accepted 11 June (2002))

Effects of rotational mode coupling on photometric parameters of stellar oscillations are studied. At moderate rotation rates, a strong coupling between modes of spherical harmonic degree, $\ell$, differing by 2 and of the same azimuthal order, m, takes place if the frequencies are close. This is a common situation amongst main sequence pulsators. Numerical results for a sequence of $\beta$ Cephei star models are reported for the two- and three-mode couplings. One consequence of mode coupling is that modes of higher degree should be considered in photometric mode identification. Modes with nominal degree $\ell>2$ acquire substantial $\ell\le2$ components and therefore are more likely to reach detectable amplitudes. Coupled mode positions in the amplitude ratio - phase difference diagrams, based on multicolour photometry, become both aspect- and m-dependent. Examples of the mode path in the diagram with varying aspect are given. The diagrams remain a useful tool for mode identification in rotating stars but the tool must be used with care.

Key words: stars: $\beta$ Cephei variables -- stars: oscillation -- stars: rotation

Offprint request: J. Daszynska-Daszkiewicz, daszynsk@camk.edu.pl

© ESO 2002