AAS 207th Meeting, 8-12 January 2006
Session 163 Star Formation Grab Bag I
Oral, Wednesday, 2:00-3:30pm, January 11, 2006, Wilson A/B

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[163.05] The Origin of Episodic Accretion Bursts in the Early Stages of Star Formation

S. Basu, E. I. Vorobyov (UWO)

We present the first model of cloud core collapse which self-consistently generates episodic mass accretion and luminosity bursts. Our numerical models follow the collapse of a rotating molecular cloud core that leads self-consistently to the formation of a protostar and protostellar disk. The disk quickly becomes unstable to the development of a spiral structure similar to that observed recently in AB Aurigae. The instability is driven by the continuous infall of matter from the protostellar envelope onto the disk. The gravitational instability leads to the formation of dense protostellar/protoplanetary clumps within the spiral arms. The growing strength of spiral arms and ensuing redistribution of mass and angular momentum creates a strong centrifugal disbalance in the disk and triggers bursts of mass accretion during which the dense protostellar/protoplanetary clumps fall onto the central protostar. These episodes of clump infall may manifest themselves as episodes of vigorous accretion rate ( \ge~10-4~M\odot~yr-1) which lead to luminosity increases of up to a factor ~1000. Between these accretion bursts, the protostar is characterized by a low accretion rate ( < 10-6 M\odot~yr-1). During the phase of episodic accretion, the mass of the protostellar disk remains less than the mass of the protostar.

This work was supported by a grant from NSERC. EIV acknowledges support from a CITA National Fellowship.

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