RR LYRAES AND CEPHEIDS AT MINIMUM AND MAXIMUM LIGHT

We present an explanation of the observed behaviour of RRab stars at l ight minimum and Cepheids at light maximum in a common framework. For RRab star models, the temperature of the photosphere at minimum light is related to the mass lying above the hydrogen ionization zone, which in turn is related to global values such as L/M and T-eff. Models whi ch match observations in terms of the temperature of the photosphere a t minimum light also match the observations in terms of the Fourier ph ase parameters phi(21) and phi(31) of the light curve. Possibilities f or asteroseismology arising from this are discussed.