Nonsteady Accretion in Protostars

摘要: Observations indicate that mass accretion rates onto low-mass protostars are generally lower than the of infall to their disks; this suggests much protostellar must be accreted during rare, short outbursts rapid accretion. We explore when disk is likely highly variable. While constant α disks can in principle adjust match rates, unlikely have α. In particular, we show neither models with angular momentum transport due solely magnetorotational instability (MRI) nor gravitational (GI) at over large range radii needed move infalling envelope material down central protostar. MRI and GI combine produce starting a few AU. Our analysis consistent time-dependent Armitage et al. agrees our observational study outbursting object FU Ori.