Evolution of very low mass pre-main sequencestars and young brown dwarfs under accretionA phenomenological approach

摘要

In the poster presented in Cool Star 15, we analyzed the effect of disk accretion on theevolution of very low mass pre-main sequence stars and young brown dwarfs and the resultinguncertainties on the determination of masses and ages. We use the Lyon evolutionary 1-D code ([1])assuming a magnetospheric accretion process, i.e., the material falls covering a small area of theradiative surface, and we take into account the internal energy added from the accreted materialas a free parameter E. Even if the approach to this problem is phenomenological, our formalismprovides important hints about characteristics of disk accretion, which are useful for improvedstellar interior calculations. Using the accretion rates derived from observations our results showthat accretion does not affect considerably the position of theoretical isochrones as well as theluminosity compared with standard non-accreting models (e.g., [2]). See more discussions in aforthcoming paper by Gallardo, Baraffe & Chabrier (2008).