Constraints on stellar convection from multi-colour photometry of δ Scuti stars

¹ Astronomical Institute of the Wrocław University, ul. Kopernika 11, 51-622 Wrocław, 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

Corresponding author: J. Daszyńska-Daszkiewicz, daszynska@astro.uni.wroc.pl

Received: 14 April 2003
Accepted: 28 May 2003

Abstract

In δ 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, , 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  from multi-colour data and apply it to three δ Scuti stars. The method indeed works. Determination of  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.