A Dynamical Picture of Failed Supernovae
Eric R. Coughlin (UC Berkeley)
December 17, 2018
Abstract: Despite the fact that nature generates core-collapse supernovae on a daily basis, stellar explosions are not easily produced from first principles. In particular, the neutron star ”bounce” paradigm — wherein the overpressured neutron star formed during core collapse launches a shock that unbinds the overlying envelope — has been shown to fail in most cases, as the ram pressure of infalling material causes the shock to stall at small radii. If nothing revives this stalled shock, the continued accretion of mass onto the central core results in the formation of a black hole, and the black hole swallows the star in a ”failed supernova.” In this talk, I will discuss a mechanism, triggered by neutrino production during the formation of the neutron star, that is responsible for producing a second, weak shock (distinct from the neutron star bounce shock) in the outer layers of the dying star in a failed supernova. When the progenitor of a failed supernova is a supergiant, this second shock forms at the base of the hydrogen envelope, and propagates through another 2-3 decades in radius before reaching the photosphere. I will present a new class of self-similar solutions that describes the propagation of this weak shock in the hydrogen envelope of the star. I will make comparisons to simulations of shock propagation in failed supernovae, and show that these self-similar solutions reproduce both the evolution of the shock itself and the post-shock velocity, density, and pressure extremely accurately. I will discuss the implications of these findings for mass ejection and late-time fallback from failed supernovae.