Magnetocentrifugally Driven Winds from Rapidly Rotating Protostars

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Session 75 -- Star Formation II
Oral presentation, Thursday, 2:30-4:00, Zellerbach Playhouse Room

[75.02] Magnetocentrifugally Driven Winds from Rapidly Rotating Protostars

J. Najita (UCB)

We examine the hypothesis that bipolar outflows associated with deeply embedded young stellar objects are driven by powerful stellar winds generated by the ``X-celerator mechanism,'' a process in which mass loss along open magnetic field lines emerging from the equatorial regions of a critically rotating star is centrifugally enhanced by the combination of rapid rotation and strong magnetic fields.

We have constructed detailed 2D steady state axisymmetric models of the sub-Alfvenic regions of winds driven by the X-celerator mechanism. Explicit consideration of the 2D nature of the flow enables us to study the ability of the X-celerator mechanism to collimate the flow. We find that smooth acceleration to speeds of the order of the escape speed accompanied by substantial collimation of the flow can be achieved within a few stellar radii. Applying these calculations to the protostellar case, we show that at mass loss rates of $10^{-6} \,{\rm M_\odot\,y^{-1}},$ the X-celerator mechanism can accelerate protostellar winds to velocities of $100{\rm s\,km\,s^{-1}}$ within a few stellar radii given kilogauss strength stellar magnetic fields.

Thursday program listing