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Theoretical Models for Classical Cepheids: Mean Magnitudes and Colors and the Evaluation of Distance, Reddening and Metallicity

Published online by Cambridge University Press:  12 April 2016

Marcella Marconi
Affiliation:
Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italy
Filippina Caputo
Affiliation:
Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italy
Vincenzo Ripepi
Affiliation:
Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italy

Abstract

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We present a detailed analysis of theoretical period–luminosity (PL) and period–luminosity–color (PLC) relations of classical Cepheids, as derived from nonlinear, nonlocal, time-dependent convective pulsating models with different masses and chemical compositions. The predicted PL and PLC relations turn out to depend on the pulsator metallicity and, to a minor extent, on the adopted averages (magnitude-weighted or intensity-weighted) over the light cycle in different bands. We show that the determination of the reddening and true distance modulus of a galaxy from the observed PL and PLC relations is constrained by the metallicity sensitivity of these relations. Moreover, the metallicity sensitivity itself provides us with a powerful tool for deriving self-consistent evaluations of distance, reddening and metallicity of the host galaxy, once Cepheid measurements in at least three photometric bands are available. To illustrate this point, we apply our relations to the BVK data for Cepheids in the Magellanic Clouds, assuming to be unaware of their metallicities. The three filter method is finally adopted to evaluate the metallicity of galactic Cepheids (BVI data) as a function of their position.

Type
Part 5. Theoretical Models of Classical Pulsating Stars
Copyright
Copyright © Astronomical Society of the Pacific 2000

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