Age-Related Observations of Low Mass Pre-Main and Young Main Sequence Stars (Invited Review)

TL;DR

This review discusses methods for determining the ages of young low-mass stars, comparing empirical and theoretical models, and exploring the implications of luminosity spreads for age estimates.

Contribution

It provides an overview of age diagnostics for young stars, focusing on HR diagrams and addressing discrepancies between empirical and theoretical isochrones.

Findings

Empirical young cluster isochrones are compared with theoretical models.

The consistency of stellar ages derived from different methods is examined.

The significance of luminosity spreads at constant temperature for age estimation is discussed.

Abstract

This overview summarizes the age dating methods available for young sub-solar mass stars. Pre-main sequence age diagnostics include the Hertzsprung-Russell (HR) diagram, spectroscopic surface gravity indicators, and lithium depletion; asteroseismology is also showing recent promise. Near and beyond the zero-age main sequence, rotation period or vsini and activity (coronal and chromospheric) diagnostics along with lithium depletion serve as age proxies. Other authors in this volume present more detail in each of the aforementioned areas. Herein, I focus on pre-main sequence HR diagrams and address the questions: Do empirical young cluster isochrones match theoretical isochrones? Do isochrones predict stellar ages consistent with those derived via other independent techniques? Do the observed apparent luminosity spreads at constant effective temperature correspond to true age spreads? While definitive answers to these questions are not provided, some methods of progression are outlined.