Testing the Chronometric Accuracy of Stellar Evolution Models Using Young Stars in Open Clusters

Abstract

Comparisons between empirical data and theoretical stellar evolutionary models indicate large systematic errors in the stellar ages resulting from different age-dating techniques. Nevertheless, these chronometric tools have been used to determine fundamental timescales in many different branches of astrophysics. The primary scientific goal of this study, resulting from research presented in my thesis, is to perform a disparate range of independent tests of stellar age, using multiple age-dating techniques of stellar samples in order to constrain, and inform future refinement of, the existing theoretical stellar evolutionary models. We describe the results from a extensive study of the PMS eclipsing binary Par1802. Through detailed orbit and light-curve solutions we have identified Par1802 to be composed of two young stars with nearly identical masses of 0.4 M⊙, making this system the first discovered pair of PMS low-mass “identical twins.” Par1802 provides us with a unique opportunity to test the identical astrophysical nature of young equal-mass stars and the accuracy of the various PMS models. We then detail our modeling of empirical H-R diagrams using isochrones from stellar evolutionary models. Employing a new statistical approach to modeling cluster sequences on empirical H-R diagrams, we derive ages and distances of two open clusters, IC4665 and Blanco1, and identify systematic offsets between the best-fit isochrone ages. We also explore age-dating techniques for stars in open clusters based on magnetic activity, including a new analysis of X-ray data for Blanco1. We also include an epilogue that contains additional analysis of rotation and X-ray emission distributions for Blanco1, a comparison of X-ray emission in Blanco1 and IC4665, and provide ideas to quantitatively calibrate magnetic activity and age using open clusters. Finally, we conclude by describing current and future implications of this thesis as we work towards reconciling empirical and model-predicted stellar ages. Namely, summarizing our on-going projects, we provide details into our investigation into the role of convection and radius in predicted stellar ages.