EDP Sciences
Free access
Volume 407, Number 3, September I 2003
Page(s) 999 - 1006
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030947

A&A 407, 999-1006 (2003)
DOI: 10.1051/0004-6361:20030947

Constraints on stellar convection from multi-colour photometry of $\delta$ Scuti stars

J. Daszynska-Daszkiewicz1, 2, 3, W. A. Dziembowski2, 4 and A. A. Pamyatnykh2, 5, 6

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  Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
4  Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
5  Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya Str. 48, 109017 Moscow, Russia
6  Institute of Astronomy, University of Vienna, Türkenschanzstr. 17, 1180 Vienna, Austria

(Received 14 April 2003 / Accepted 28 May 2003 )

In $\delta$ Scuti star models, the calculated amplitude ratios and phase differences for multi-colour photometry exhibit a strong dependence on convection. These observables are tools for the determination of the spherical harmonic degree,  $\ell$, of the excited modes. The dependence on convection enters through the complex parameter  f, which describes bolometric flux perturbation. We present a method of simultaneous determination of  f and harmonic degree  $\ell$ from multi-colour data and apply it to three $\delta$ Scuti stars. The method indeed works. Determination of  $\ell$ appears unique and the inferred values of  f are sufficiently accurate to yield a useful constraint on models of stellar convection. Furthermore, the method helps to refine stellar parameters, especially if the identified mode is radial.

Key words: stars: variables: $\delta$ Scuti -- stars: oscillation -- convection

Offprint request: J. Daszynska-Daszkiewicz, daszynska@astro.uni.wroc.pl

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