Asteroseismology of the double-radial mode δ Scuti star BP Pegasi

Using the ASAS data, we determine the pulsational frequencies of the high-amplitude $\delta$ Sct star BP Pegasi. The analysis revealed only the two known, independent frequencies. On the basis of multicolour Str\"omgren photometry, we independently find that both frequencies can only be associated with radial modes which, according to the frequency ratio, are fundamental and first overtone modes. The models fitting the two frequencies depend strongly on the opacity data. For low values of the mixing length parameter $\alpha_{\rm MLT}\approx 0.5$, only the OPAL seismic models in the post-main sequence phase of evolution are caught within the observed error box. Seismic OP and OPLIB models can only reach the error box if we increase $\alpha_{\rm MLT}$ to at least 2.0. Then, including the non-adiabatic parameter $f$ into our seismic modelling, we constrain various parameters, employing Monte Carlo-based Bayesian analysis.