Importance of Prolate Neutrino Radiation in Core-Collapse Supernovae: The Reason for the Prolate Geometry of SN1987A?

Abstract

Abstract We have carried out 2-D simulations of core-collapse supernova explosions. The local neutrino radiation field was assumed to have its maximum value either at the symmetry (polar) axis or on the equatorial plane. These led to prolate and oblate explosions, respectively. We have found that the gain of the explosion energy in the prolate explosion evolves more predominately than that in the oblate one when the total neutrino luminosity is given. Namely, the prolate explosion is more energetic than the oblate one. One of the authors (Shimizu et al. 2001) showed for the first time that globally anisotropic neutrino radiation produces a more powerful explosion than does spherical neutrino radiation. In our previous study (Madokoro et al. 2003), we improved the numerical code of Shimizu et al. (2001), and demonstrated that globally anisotropic neutrino radiation yields a more energetic explosion than does spatially-fluctuated neutrino radiation. Together with the result of this paper, we conclude that globally anisotropic (prolate) neutrino radiation is the most effective way to increase the explosion energy among various types of explosions investigated in these studies. We discuss the reason for this. Our result is suggestive of the fact that the expanding materials of SN1987A have been observed to have a prolate geometry.