Evolutionary and Pulsational Constraints for Super–Metal‐rich Stars withZ= 0.04

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Abstract

We investigate the evolutionary behavior of stellar structures with metallicity Z \ 0.04 in order to disclose theoretical expectations for both evolutionary and pulsational behaviors of supermetal-rich (SMR) objects, which are found in the solar neighborhood, in the Galactic bulge, and in elliptical galaxies. A suitable set of stellar models is presented for the given metallicity value but for two alternative assumptions about the amount of original He, namely, Y \ 0.34 and Y \ 0.37. Theoretical isochrones for H-burning evolutionary phases are presented for ages ranging from 18 to less than 1 Gyr. The evolutionary behavior of He-burning structures is discussed for suitable assumptions about the mass of the progenitors and the amount of mass loss. For both quoted assumptions of original He abundance, we conrm that at metal contents larger than the solar value the luminosity of the horizontal branch (HB) at the RR Lyrae gap increases as the metal content increases, a direct consequence of the expected simultaneous increase of original He. We nd that, at the exhaustion of central helium, SMR stars denitely undergo the gravonuclear instabilities previously found in some He-burning structures with solar metallicity.

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