Is Strong SASI Activity the Key to Successful Neutrino-Driven Supernova Explosions?

Details Is Strong SASI Activity the Key to Successful Neutrino-Driven Supernova Explosions? Is Strong SASI Activity the Key to Successful Neutrino-Driven Supernova Explosions?

2011-08-22

arxiv.org/abs/1108.4355v1

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

19 pages, 14 figures, 26 eps files; submitted to The Astrophysical Journal

Scientific paper

With a numerical approach similar to Nordhaus et al. (2010) but a modified approximation of neutrino effects we explore the viability of the neutrino mechanism of core-collapse supernova explosions in dependence on the spatial dimension of the simulations. We cannot confirm the previous findings. While we also observe that 2D models explode for a lower driving neutrino luminosity than those in 1D, we do not find that explosions in 3D occur easier and earlier than in 2D. Moreover, we find that the average entropy of matter in the gain layer hardly depends on the dimension and thus is not a good diagnostic quantity for the readiness to explode. Instead, the mass, integrated entropy, total neutrino-heating rate, and nonradial kinetic energy in the gain layer turn out to be higher for models that are closer to explosion. Coherent, large-scale mass motions as typically associated with the standing accretion-shock instability (SASI), whose low spherical-harmonics modes have the highest growth rates, are observed to support the explosion because they drive strong shock expansion and thus enlarge the gain layer including its mass and integral values of entropy, neutrino-energy deposition, and nonradial kinetic energy. While 2D models with better angular resolution explode clearly more easily, the opposite trend is seen in 3D. We interpret this as a consequence of the turbulent energy cascade, which transports energy from small to large spatial scales in 2D, thus fostering SASI activity, whereas the energy flow in 3D is in the opposite direction and feeds fragmentation and vortex motions on smaller scales, making the 3D evolution more similar to 1D when finer grid resolution is used. More favorable conditions for explosions in 3D may therefore be tightly linked to efficient growth of low-order SASI modes including nonaxisymmetric ones.

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