Calibrated stellar models for metal-poor populations^*

¹ Dipartimento di Fisica, Università di Pisa, via Buonarroti 2, 56126 Pisa, Italy
² INFN Sezione di Pisa, via Buonarroti 2, 56126 Pisa, Italy
³ Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
⁴ INFN, sezione di Ferrara, via Paradiso 12, 44100 Ferrara, Italy

Corresponding author: S. Degl'Innocenti, scilla@df.unipi.it

Received: 16 June 2003
Accepted: 2 March 2004

Abstract

We extend to lower metallicities recent evolutionary computations devoted to Magellanic Clouds stars, presenting and discussing new stellar models with , 0.0004, 0.0006, 0.001 and suitable assumptions about the original He content. As in the previous paper, evolutionary results are compared with observational data to properly calibrate the assumptions about the efficiency of the surface convection. On this basis, we follow the evolution of stellar models in the mass range 0.6 to 11  from the Main Sequence (MS) to the C ignition or the onset of thermal pulses in the advanced Asymptotic Giant Branch (AGB) phase, presenting cluster isochrones covering the range of ages from 20 Myr to 20 Gyr. Selected predictions constraining the cluster ages are discussed, presenting a calibration of the difference in magnitude between the luminous MS termination and the He burning giants in terms of the cluster age. Both evolutionary tracks and isochrones are available at the URL http://astro.df.unipi.it/SAA/PEL/Z0.html.