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

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 determination of the spherical harmonic degree, l, 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 l from multi-colour data and apply it to three δ Scuti stars. The method indeed works. Determination of l appears unique and the inferred f ’s 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.