Scaled solar tracks and isochrones in a large region of the Z–Y plane^*

II. From 2.5 to 20 M stars

¹ INAF – Padova Astronomical Observatory, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: gianpaolo.bertelli@oapd.inaf.it
² Astronomy Department, Padova University, Vicolo dell'Osservatorio 3, 35122 Padova, Italy

Received: 17 March 2009
Accepted: 17 September 2009

Abstract

We extend our theoretical computations for low-mass stars to intermediate-mass and massive stars, for which few databases exist in the literature. Evolutionary tracks and isochrones are computed for initial masses for a grid of 37 chemical compositions with metal content Z between 0.0001 and 0.070 and helium content Y between 0.23 and 0.40 to enable users to obtain isochrones for ages as young as about 10⁷ years and to simulate stellar populations with different helium-to-metal enrichment laws. The Padova stellar evolution code is identical to that used in the first paper of this series. Synthetic TP-AGB models allow stellar tracks and isochrones to be extended until the end of the thermal pulses along the AGB. We provide software tools for the bidimensional interpolation (in Y and Z) of the isochrones
from very old ages down to about 10⁷ years. This lower limit depends on chemical composition. The extension of the blue loops and the instability strip of Cepheid stars are compared and the Cepheid mass-discrepancy is discussed. The location of red supergiants in the H-R diagram is in good agreement with the evolutionary tracks for masses from 10 to . Tracks and isochrones are available in tabular form for the adopted grid of chemical compositions in the extended plane in three photometric systems. An interactive web interface allows users to obtain isochrones of any chemical composition inside the provided range and also to simulate stellar populations with different helium-to-metal enrichment laws.