EPoS Contribution
EPoS Contribution
The effect of accretion on stellar structures: Multi-dimensional time-implicit hydrodynamical simulations

Chris Geroux
U Exeter, Exeter, UK
Recent work has suggested the possible high impact of accretion on the structure and evolution of very young low mass stars and brown dwarfs. The accretion history could indeed play a crucial role on the very early stages of evolution of such objects and explain some observational puzzles such as the luminosity spread in the Luminosity-Teff diagram of members of young clusters and star formation regions. Those results, however, are based on 1D stellar evolution calculation with phenomenological treatments of accretion and internal convection, implying rough assumptions (instantaneous and uniform redistribution of the accreted mass and of the extra source of internal energy brought by the accreted material).
We will present preliminary multi-dimensional numerical simulations of non-spherical accretion (i.e through an accretion disk) on a very young, mostly convective, solar mass star (see figure) based on a multi-D time implicit hydrodynamical code that we are developing in our team. These are the very first multi-D simulations describing this type of process in young stars. Our goal is to better describe the mass and heat redistribution of accreted matter in the stellar interior, depending on the mass accretion rate and the entropy of the infalling material. A major uncertainty regarding the structure of accreting low mass stars and brown dwarfs concerns the efficiency of convection, in terms of energy transport and chemical species mixing in their interior. Accretion of "hot" material is expected to alter the convection efficiency in the stellar interior and we are particularly interested in understanding and describing more accurately these effects.
Caption: Vorticity in a convective young sun model. Shown is the outer 80% of the star.
Collaborators:
I. Baraffe, U Exeter
Key publication

Suggested Sessions: Cores to Disks