Beat Cepheids as Probes of Stellar and Galactic Metallicity
The Astrophysical Journal, 660 (1):
723 (2007)Abstract
The mere location of a beat Cepheid model in a period ratio versus period diagram (Petersen diagram) puts very tight constraints on its metallicity Z . The beat Cepheid Petersen diagrams are revisited with linear nonadiabatic turbulent convective models, and their accuracy as a probe for stellar metallicity is evaluated. They are shown to be largely independent of the helium content Y , and they are also only weakly dependent on the mass-luminosity relation that is used in their construction. However, they are found to show sensitivity to the relative abundances of the elements that are lumped into the metallicity parameter Z . Rotation is estimated to have but a small effect on the "pulsation metallicities." A composite Petersen diagram is presented that allows one to read off upper and lower limits on the metallicity Z from the measured period P 0 and period ratio P 10 .