Theoretical UBVI light curves of RR Lyrae stars

By performing detailed frequency-dependent radia-tive transfer computations we have obtained UBVI light curves of nonlinear RR Lyrae models, which recently have been calculated by the Vienna nonlinear convective pulsation code. For two sets of stellar parameters (M = 0. the fundamental and the first overtone limit cycle solutions have been calculated for effective temperatures ranging from 6000 K to 7200 K. The results of these computations are used as input for the radiative transfer calculations. The properties of the UBVI light curves have been analyzed by means of standard Fourier decomposition and a detailed comparison to recent observations has been performed. As main results we find an good agreement with important observed RR Lyrae properties like pulsation amplitudes and Fourier parameters in B-, V-, and I-bands. Additionally from these synthetic colour light curves we derive linear transformation laws between amplitudes as well as Fourier parameters in the different passbands.