Signatures of stellar collapse in electron-type neutrinos

Abstract

Neutrinos provide a direct probe for observing the internal convulsions of stars at the end of their thermonuclear life. Implications of developments on the theory of stellar collapse¹ have not been explored systematically for neutrino emission. In view of experiments^2,3 that can detect extraterrestrial neutrinos, a summary of the theoretical signatures expected in neutrino emission from stellar collapse is needed. If such experiments^2,3 record an event with features indicative of stellar collapse, its signatures will provide valuable tests for present theories on stellar demise. The current hypothesis¹ of stellar collapse is that the iron core (M_c ∼ 1.5 M⊙) of a massive star (M_*>12M⊙) loses its pressure support at the end point of thermonuclear evolution. The core implodes to densities above that of nuclear matter where the collapse halts. The bounce forms a shock at the surface of the core, which then propagates into the infalling mantle. The outcome may be either continued collapse to a black hole or a supernova, depending on the initial mass of the iron core. Here we examine the v_e emission for both cases. In particular, we give analytical expressions for the rise-time and magnitude of the leading pulse and the average energy of the emitted neutrinos. We then discuss subsequent behaviour of the emission. Ongoing terrestrial experiments can resolve much of the emission's structure up to distances of ∼2 kpc.