We present the results of nonlinear pulsation modeling of 20 bump Cepheids in the LMC. By obtaining an optimal fit to the observed V, R MACHO light curves, we have placed tight constraints on stellar parameters of M, L, and Teff as well as quantities of distance modulus and reddening. We describe the mass-luminosity relation for core He burning for intermediate-mass stars. The mass-luminosity relation depends critically on the level of mixing within the stellar interior over the course of the main-sequence lifetime. Our sample is significantly more luminous than predicted by classical stellar evolutionary models that do not incorporate extension to the convective core. Under the paradigm of convective core overshoot, our data imply Λc of 0.65 ± 0.03l/Hp. We derive a LMC distance modulus of 18.55 ± 0.02.
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