Hydrodynamic models for the RRc stars

Hydrodynamic pulsation models are constructed for the RR Lyrae stars, including a large grid of RRc models and a pair of models with parameters corresponding to the RRd stars. The latter calculations are used to argue that LNA periods are sufficient when comparing RRd models with observations. The RRc models are subjected to Fourier decomposition, and a discussion of various Fourier parameters is undertaken to complement a treatment given elsewhere of the phase parameter ϕ31. It is shown that the theoretical light curves mimic the observations rather well, including the observed run of ϕ31with period and the fall-off of ϕ31 with R21 • The greatest deficiency of the models lies in their failure to reproduce observed values of the phase parameter ϕ21. Finally, turning to the velocity curves, we show that the first-order phase lag (Δϕ)1 between velocity and light is related in the models to the linear driving ƞ1 and thus potentially may be used to measure the distances of observed RRc stars from their respective blue edges