AAS 207th Meeting, 8-12 January 2006
Session 54 Supernovae, Novae, and Cataclysmic Variables
Oral, Monday, 2:30-4:00pm, January 9, 2006, Salon 3

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[54.04] Aspherical Core--Collapse Explosion: Rotation and Magnetic Fields

S. Akiyama (University of Texas at Austin)

While the process that converts implosion into explosion in core collapse supernovae is poorly understood, the observed asphericity provides new constraints on the physics. Since pulsars are rotating and magnetized neutron stars, there is no doubt that rotation and magnetic fields are inherent to the exploding engine. We have shown that magnetic field amplification is an inevitable by--product of the differential rotation that accompanies core--collapse. We performed 1D core--collapse simulations of rotating iron cores with various rotational profiles and velocities. We found that differential rotation was a generic feature of rotating iron core collapse. As a result, the magnetorotational instability (MRI) generates magnetic fields of order 1015-17 G in a few tens of milliseconds where the negative shear is the strongest. The corresponding MHD luminosity available is ~1052 erg s-1, which can modify the explosion dynamics if the power is sustained for a fraction of a second.

When rotational effects are included, we found that there is a critical iron core rotation rate that gives the most rapidly rotating proto--neutron star, faster than which the rotational velocity of the proto--neutron star decreases due to centrifugal support. This non--monotonic behavior of post--collapse core rotation suggests that the progenitor of the most rapidly rotating proto--neutron star is not the most rapidly rotating iron core, but that only those iron cores with nearly the critical initial rotation rate may produce the maximum proto--neutron star rotation, the strongest magnetic fields, and the most robust supernova explosions. Further implications for rotation and magnetic fields, pulsars and magnetars, and jet formation mechanisms are discussed.

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