http://arxiv.org/abs/1402.6292
27 years after the detection of the thermal neutrino single signal from SN1987A, which confirmed the core-collapse scenario and the possible formation of a neutron star, there has not been detected yet its compact remnant. In particular, the hypercritical accretion model proposed by Chevalier (1989) forecasted the accretion of $\sim 0.15 M_{\odot}$ in two hours and after the submergence of the magnetic field in the newborn neutron star as has been proposed by Bernal et al.(2013). In this paper, we revisit such model for SN1987A in a numerical framework, focusing on the neutrino cooling effect in the supernova fall-back dynamics. For that, we carry out numerical simulations of the accretion of matter onto the surface of the newborn neutron star in order to estimate the physical parameters such as the emissivity and luminosity of neutrinos in this regime using both an analytical formula and the tabulated values for several neutrino cooling processes. We use a customized version of the FLASH code to perform the numerical simulations in a 2D spherical mesh. In addition, due to matter effects thermal neutrinos may oscillate resonantly from one flavor to another when they go through the outer layers of the expanding supernova. To investigate these oscillations, we consider an energy of neutrino in the range of 1-30 MeV, the mixing parameter and splitting then this phase of the supernova in four regions: core surface, accretion shock envelope, free fall region and surface of the star. For the magnetized plasma of the first region, we derive the neutrino effective potential up to order $1/M_W^4$. For the other regions and based on each density profile we calculate the probabilities of neutrino oscillations at different radii. Finally, in addition of neutrino luminosity, we estimate the number of events expected as well as the neutrino flavor ratio on Earth, as a signature of this phase.
C. Bernal, N. Fraija and H. M
Wed, 26 Feb 14
5/51