Updated Pre-Main Sequence tracks at low metallicities for 0.1< M/Mo<1.5

TL;DR

This paper extends pre-main sequence stellar evolution models to low metallicities, providing updated tracks and isochrones for stars with masses between 0.1 and 1.5 solar masses, crucial for studying young populations in metal-poor environments.

Contribution

It introduces low-metallicity PMS models based on NEMO--FST physics, filling a gap where MLTa2D calibrations are unavailable, and offers new evolutionary tracks for metal-poor stars.

Findings

Extended PMS models to [Fe/H]= -2.0

Provided updated isochrones for low-metallicity stars

Models available online for community use

Abstract

Young populations at Z<Zo are being examined to understand the role of metallicity in the first phases of stellar evolution. For the analysis it is necessary to assign mass and age to Pre--Main Sequence (PMS) stars. While it is well known that the mass and age determination of PMS stars is strongly affected by the convection treatment, extending any calibration to metallicities different from solar one is very artificial, in the absence of any calibrators for the convective parameters. For solar abundance, Mixing Lenght Theory models have been calibrated by using the results of 2D radiative-hydrodynamical models (MLTa2D), that result to be very similar to those computed with non-grey ATLAS9 atmosphere boundary condition and full spectrum of turbolence (FST) convection model both in the atmosphere and in the interior (NEMO--FST models). While MLTa2D models are not available for lower metallicities, we extend to lower Z the NEMO--FST models, in the educated guess that in such a way we are simulating also at smaller Z the results of MLTa2D. We present PMS models for low mass stars from 0.1 to 1.5 Mo for metallicities [Fe/H]= -0.5, -1.0 and -2.0. The calculations include the most recent interior physics and the latest generation of non-grey atmosphere models. These evolutionary tracks and isochrones are available in electronic form at a WEB site http://www.mporzio.astro.it/%7Etsa/