BANYAN. IV. Fundamental parameters of low-mass star candidates in nearby young stellar kinematic groups - Isochronal Age determination using Magnetic evolutionary models

TL;DR

This study uses magnetic evolutionary models to determine the ages of low-mass star candidates in young stellar groups, reconciling different age estimation methods and providing refined age estimates.

Contribution

It introduces the application of magnetic evolutionary models to improve age estimates of low-mass stars in young groups, addressing previous inconsistencies.

Findings

Magnetic models fit observed stellar parameters well assuming kG magnetic fields.

Inclusion of magnetic fields increases isochronal age estimates to 15-28 Myr.

Derived age of 26±3 Myr from Lithium Depletion Boundary is consistent with previous estimates.

Abstract

Based on high resolution optical spectra obtained with ESPaDOnS at CFHT, we determine fundamental parameters (\Teff, R, \Lbol, \logg\ and metallicity) for 59 candidate members of nearby young kinematic groups. The candidates were identified through the BANYAN Bayesian inference method of \citet{2013malo}, which takes into account the position, proper motion, magnitude, color, radial velocity and parallax (when available) to establish a membership probability. The derived parameters are compared to Dartmouth Magnetic evolutionary models and to field stars with the goal to constrain the age of our candidates. We find that, in general, low-mass stars in our sample are more luminous and have inflated radii compared to older stars, a trend expected for pre-main sequence stars. The Dartmouth Magnetic evolutionary models show a good fit to observations of field K and M stars assuming a magnetic field strength of a few kG, as typically observed for cool stars. Using the low-mass members of $\beta$Pictoris moving group, we have re-examined the age inconsistency problem between Lithium Depletion age and isochronal age (Hertzspring-Russell diagram). We find that the inclusion of the magnetic field in evolutionary models increase the isochronal age estimates for the K5V-M5V stars. Using these models and field strengths, we derive an average isochronal age between 15 and 28 Myr and we confirm a clear Lithium Depletion Boundary from which an age of 26$\pm$3~Myr is derived, consistent with previous age estimates based on this method.