The Importance of Episodic Accretion for Low-mass Star Formation

A star acquires much of its mass by accreting material from a disk. Accretion is probably not continuous but episodic. We have developed a method to include the effects of episodic accretion in simulations of star formation. Episodic accretion results in bursts of radiative feedback, during which a protostar is very luminous, and its surrounding disk is heated and stabilized. These bursts typically last only a few hundred years. In contrast, the lulls between bursts may last a few thousand years; during these lulls the luminosity of the protostar is very low, and its disk cools and fragments. Thus, episodic accretion enables the formation of low-mass stars, brown dwarfs, and planetary-mass objects by disk fragmentation. If episodic accretion is a common phenomenon among young protostars, then the frequency and duration of accretion bursts may be critical in determining the low-mass end of the stellar initial mass function.