Evolution of very low mass pre-main sequence stars and young brown dwarfs under accretion: A phenomenological approach

TL;DR

This study investigates how disk accretion influences the evolution of very low mass pre-main sequence stars and brown dwarfs, revealing that accretion has limited impact on their observable properties compared to non-accreting models.

Contribution

It introduces a phenomenological model of accretion effects on stellar evolution, incorporating internal energy addition and providing insights for improved stellar interior calculations.

Findings

Accretion does not significantly alter isochrone positions.

Luminosity remains similar to non-accreting models.

The formalism offers useful hints for stellar interior modeling.

Abstract

In the poster presented in Cool Star 15, we analyzed the effect of disk accretion on the evolution of very low mass pre-main sequence stars and young brown dwarfs and the resulting uncertainties on the determination of masses and ages. We use the Lyon evolutionary 1-D code assuming a magnetospheric accretion process, i.e., the material falls covering a small area of the radiative surface, and we take into account the internal energy added from the accreted material as a free parameter $\epsilon$. Even if the approach to this problem is phenomenological, our formalism provides important hints about characteristics of disk accretion, which are useful for improved stellar interior calculations. Using the accretion rates derived from observations our results show that accretion does not affect considerably the position of theoretical isochrones as well as the luminosity compared with standard non-accreting models. See more discussions in a forthcoming paper by Gallardo, Baraffe and Chabrier (2008).