We demonstrate how, with a purely empirical analysis of the irregular lightcurve data, one can extract a great deal of information about the stellar pulsation mechanism. An application to R Sct thus shows that the irregular lightcurve is the result of the nonlinear interaction of two highly nonadiabatic pulsation modes, namely a linearly unstable, low frequency mode, and the second mode that, a...

The theoretical period-luminosity relation for Cepheids was deduced from stellar evolution and pulsation computations. Questions concerning the metallicity dependence of the relation as well as the constancy of the pulsation ‘constant’ Q in the instablility strip were addressed. We found no significant metallicity dependence of either the slope or of the zero-point of the period-luminosity rela...

A new precise method for measuring magnetic fields on Zeeman plates of the southern cepheid W Sgr is reviewed. Ten plates over the 7_6 period of pulsation show two extrema in the measured values of the effective magnetic field. The method has a precision of ±0.4_ in the Zeeman shift corresponding to ±50 gauss (g). A negative "spike" of -220g occurred at the time of arrival of the compressional ...

It has long been known that rotation can have an appreciable impact on stellar pulsation — by modifying the usual p and g modes found in the non-rotating case, and by introducing new classes of mode. However, its only relatively recently that advances in numerical simulations and complementary theoretical treatments have enabled us to model these phenomena in any great detail. In this talk I’ll...

Thermal pulsation is a complicated mixing event in AGB stars which involves interaction between several layers of the stellar interior, and which occurs on very short timescales compared to a star’s evolutionary timescale. The temporal constraint makes these events difficult to resolve in a 1-D stellar evolution codes, and instead they are typically studied in isolation through 3-D smoothed-par...

We investigate a selected sample of Galactic classical Cepheids with available distance and reddening estimates in the framework of the theoretical scenario provided by pulsation models, computed with metal abundance Z=0.02, helium content in the range of Y =0.25 to 0.31, and various choices of the stellar mass and luminosity. After transforming the bolometric light curve of the fundamental mod...

We investigate a selected sample of Galactic classical Cepheids with available distance and reddening estimates in the framework of the theoretical scenario provided by pulsation models, computed with metal abundance Z=0.02, helium content in the range of Y =0.25 to 0.31, and various choices of the stellar mass and luminosity. After transforming the bolometric light curve of the fundamental mod...