Bump Cepheids and the Stellar Mass-Luminosity Relation

We present the results of non-linear pulsation modeling of bump Cepheids in the LMC and SMC. By obtaining an optimal fit to the observed MACHO V and R lightcurves we can determine the fundamental parameters of each Cepheid, namely mass, luminosity, effective temperature, distance modulus and reddening. We are able to describe the mass-luminosity relation for core-He burning intermediate mass stars. The mass-luminosity relation depends critically upon the level of internal mixing during the course of the star’s main-sequence evolution. Under the paradigm of convective core overshoot, our results enable us to place tight quantitative limits of the level of overshoot. We derive an overshooting parameter of Λc of 0.65±0.03 and 0.67±0.04 l/Hp for the LMC and SMC respectively.