Pulsation Models for Ultra-Low Z=0.0004 Metallicity Classical Cepheids - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




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Abstract: Classical Cepheids are primary distance indicators playing a fundamental rolein the calibration of the extragalactic distance scale. The possible dependenceof their characteristic Period-Luminosity PL relation on chemical compositionis still debated in the literature, and the behaviour of these pulsators atvery low metallicity regimes is almost unexplored. In order to deriveconstraints on the application of the Period-Luminosity relation at low metalabundances, we investigate the properties of the few ultra-low metallicity Z ~0.0004 Cepheids recently discovered in the Blue Compact Dwarf galaxy IZw18. Tothis purpose we have computed an updated and extended set of nonlinearconvective models for Z=0.0004 and Y=0.24, spanning a wide range of stellarmasses, and taking into account the evolutionary constraints for selectedluminosity levels. As a result we are able to predict the topology of theinstability strip, the variations of all the relevant quantities along thepulsation cycle, including the morphology of the light curves, the theoreticalPeriod-Luminosity-Color, Period-Wesenheit and Period-Luminosity relations atsuch a low metallicity. For each of these relations we provide the appropriatecoefficients for fundamental mode pulsators with Z=0.0004. By comparing theseresults with the properties of more metal rich Cepheids we find that thesynthetic PL relations for Z=0.0004 are steeper than at higher Z, but similarto the Z=0.004 ones, thus suggesting a leveling off of the metallicity effecttowards the lowest Zs.



Autor: M. Marconi, I. Musella, G. Fiorentino, G. Clementini, A. Aloisi, F. Annibali, R. Contreras Ramos, A. Saha, M. Tosi, R. P. van der

Fuente: https://arxiv.org/







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