The Impact of Starspots on Mass and Age Estimates During The Pre-Main Sequence

TL;DR

Starspots significantly affect the observed properties and inferred ages of pre-main sequence stars, causing radius inflation, altered lithium depletion, and potential misinterpretation of age spreads in clusters.

Contribution

This study quantifies how starspots influence stellar evolution models, revealing their role in radius inflation and age estimation biases during the pre-MS phase.

Findings

Starspots increase stellar radii by 4-10%.

Starspots suppress lithium depletion rates.

Starspots cause systematic under-estimation of ages.

Abstract

We investigate the impact of starspots on the evolution of late-type stars during the pre-main sequence (pre-MS). We find that heavy spot coverage increases the radii of stars by 4-10%, consistent with inflation factors in eclipsing binary systems, and suppresses the rate of pre-MS lithium depletion, leading to a dispersion in zero-age MS Li abundance (comparable to observed spreads) if a range of spot properties exist within clusters from 3-10 Myr. This concordance with data implies that spots induce a range of radii at fixed mass during the pre-MS. These spots decrease the luminosity and $T_{\rm eff}$ of stars, leading to a displacement on the HR diagram. This displacement causes isochrone derived masses and ages to be systematically under-estimated, and can lead to the spurious appearance of an age spread in a co-eval population.