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Astron. Astrophys. 354, 610-620 (2000)

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4. Summary

From nonlinear, nonlocal and time-dependent convective pulsating models we have derived a set of homogeneus PL, PC, CC, PLC and WPL relations in the BVRIJK passbands at varying chemical composition. We find that the predicted relations are, in various degrees, metallicity dependent, suggesting that the adoption of universal relations for Cepheid studies should be treated with caution.

The slope of the predicted relations with Z=0.004-0.008 matches the results of LMC and SMC Cepheids collected during the OGLE II microlensing survey (Udalski et al. 1999), but our zero points suggest a larger LMC distance, in agreement with the suggestions by Zaritsky (1999).

As for the comparison of the predicted relations at Z=0.02 with the observed data of calibrating Galactic Cepheids, we find a fair agreement even though the slope of our [FORMULA] and [FORMULA] relations seems shallower than observed. This is the consequence of the significant metallicity dependence in the predicted relations and we believe that a careful analysis (of larger samples of Galactic Cepheids) which takes into account the actual metallicity dispersion is required to settle the question.

Special requests for other theoretical relations can be addressed to M. Marconi.

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© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000