Stellar opacities and standard candles

The present consideration of theoretical stellar pulsation models for predicting the observed period-luminosity relations of classical Cepheids notes that recent improvements in stellar opacity calculations have shown theoretical period-luminosity-color and period-luminosity relations of +/- 0.1 mag accuracy to be possible. Improvements in theoretical evolution and pulsation models based primarily on the revised opacities yield consistent determinations of RR Lyrae masses for Oosterhoff I and II stars; model properties are in good agreement with recent observational studies of absolute magnitudes.