Confronting uncertainties in stellar physics II. exploring differences in main-sequence stellar evolution tracks

TL;DR

This study evaluates systematic uncertainties in stellar evolution models for main-sequence stars, comparing different codes and physics assumptions to understand their impact on stellar track predictions.

Contribution

It provides a detailed comparison of stellar evolution tracks from various codes, quantifies uncertainties, and discusses their sources, especially in initial composition and convective overshooting.

Findings

Uncertainties in initial composition cause about 2% error in stellar mass estimates.

Differences in convective overshooting implementation affect main sequence extent.

Overall uncertainties can be partly explained by input physics and calibration choices.

Abstract

We assess the systematic uncertainties in stellar evolutionary calculations for low- to intermediate-mass, main-sequence stars. We compare published stellar tracks from several different evolution codes with our own tracks computed using the stellar codes STARS and MESA. In particular, we focus on tracks of 1 and 3 solar masses at solar metallicity. We find that the spread in the available 1 solar mass tracks (computed before the recent solar composition revision by Asplund et al.) can be covered by tracks between 0.97-1.01 solar masses computed with the STARS code. We assess some possible causes of the origin of this uncertainty, including how the choice of input physics and the solar constraints used to perform the solar calibration affect the tracks. We find that for a 1 solar mass track, uncertainties of around 10% in the initial hydrogen abundance and initial metallicity produce around a 2% error in mass. For the 3 solar mass tracks, there is very little difference between the tracks from the various different stellar codes. The main difference comes in the extent of the main sequence, which we believe results from the different choices of the implementation of convective overshooting in the core. Uncertainties in the initial abundances lead to a 1-2% error in the mass determination. These uncertainties cover only part of the total error budget, which should also include uncertainties in the input physics (e.g., reaction rates, opacities, convective models) and any missing physics (e.g., radiative levitation, rotation, magnetic fields). Uncertainties in stellar surface properties such as luminosity and effective temperature will further reduce the accuracy of any potential mass determinations.