Cepheids in NGC 1866 - a Test for Pulsational Models

Abstract

We present nonlinear theoretical results concerning the predicted pulsation behaviour of stellar models suitable for the sample of Cepheids belonging to the Large Magellanic Cloud (LMC) star cluster NGC 1866. The blue and red edges of the instability strip, transformed into the observative plane (V, B-V) by adopting current values for the distance modulus (DM=18.57 mag., Welch et al. 1991) and for the reddening (E(B-V)=0.06 mag., Arp 1967; Walker 1974; Walker 1987), are in agreement with the observed distribution of Cepheids in the quoted cluster. Moreover, the distribution of observational data in the Bailey diagram (V amplitude versus period) appears in agreement with theoretical predictions derived adopting the luminosity level predicted by canonical evolutionary models. The role played by the direct integration of the coupling between pulsation and convection and by the input physics on the smoothness of light and velocity curves is briefly discussed.