The Burst Mode of Protostellar Accretion：（原恒星吸积的破裂模式）.pdfVIP

to appear in ApJ 20 Oct 2006 The Burst Mode of Protostellar Accretion E. I. Vorobyov1,2 and Shantanu Basu2 ABSTRACT 6 0 0 2 We present new numerical simulations in the thin-disk approximation which char- l acterize the burst mode of protostellar accretion. The burst mode begins upon the u formation of a centrifugally balanced disk around a newly formed protostar. It is com- J 6 prised of prolonged quiescent periods of low accretion rate (typically 10−7M⊙ yr−1) which are punctuated by intense bursts of accretion (typically 10−4M⊙ yr−1, with 1 v duration 100 yr) during which most of the protostellar mass is accumulated. The 8 accretion bursts are associated with the formation of dense protostellar/protoplanetary 1 1 embryos, which are later driven onto the protostar by the gravitational torques that 7 develop in the disk. Gravitational instability in the disk, driven by continuing infall 0 6 from the envelope, is shown to be an effective means of transporting angular momen- 0 tum outward, and mass inward to the protostar. We show that the disk mass always / h remains significantly less than the central protostar mass throughout this process. The p - burst phenomenon is robust enough to occur for a variety of initial values of rotation o rate, frozen-in (supercritical) magnetic field, and density-temperature relations. Even r t in cases where the bursts are nearly entirely suppressed, a moderate increase in cloud s