Do “neutrino supernovae” exist?

Question

Core collapse supernovae release most of their energy in the form of neutrinos. About 1% of the neutrinos are absorbed by the thick outer envelope which powers a spectacular supernova explosion.

Core collapse can also happen in white dwarfs. According to this answer, white dwarfs made of light elements (He, C) explode upon reaching the Chandrasekhra mass limit, while white dwarfs consisting of heavy elements (O, Ne, Mg) collapse into neutron stars. The collapse is not much different than the core collapse of massive stars, except that the white dwarfs are not buried under a thick atmosphere. As a result, neutrinos will just escape freely with little absorption.

Does that mean such collapses will result in “neutrino supernovae” (in analogy with neutron bombs), with minimal electromagnetic emission?

Answer 1

The answer appears to be yes. Unless the accretion-induced-collapse (AIC) supernova interacts with a close companion (see below) then the supernova will be much fainter optically than a Type II core-collapse supernova explosion in a massive star, but will be similar in terms of neutrino luminosity.

In type II supernovae the neutrinos are not absorbed by the thick outer envelope. They are absorbed, briefly, in the inner few tens of km of the collapsed core at nuclear densities ($\geq 10^{17}$ kg/m$^{-3}$). From that point of view, a supernova instigated by accretion-induced-collapse (AIC) of a massive white dwarf will be no different to a core-collapse supernova.

A reasonably canonical paper to look at is that by Fryer et al. (1999) who did some of the first basic models of AIC supernovae. Perhaps the main difference in not having a massive envelope is that the explosion develops more rapidly - there should not be such a big delay in between a neutrinio signature and a visible signature of the supernova. Another consequence maybe that "de-leptonised" (aka neutron-rich) material should be more successfully ejected and could be a source of neutron-capture (r-process) elements. In type II supernovae, the infalling envelope probably causes a much greater fallback of this neutron-rich material onto the proto neutron star.

AIC supernovae are though expected to be relatively faint and short-lived in optical terms - the amount of mass ejected is small and contains little of the radioactive Nickel that powers type Ia supernovae. Piro & Thompson (2014) estimate that the absolute visual magnitude of such an event would peak at just $M_V \sim -13$ , which is about 100-1000 times fainter than most type Ia and type II supernovae, and would fade on timescales of 1-2 days. However, if the AIC is triggered by accretion from a close companion, they show that the blast wave will shock-hear the envelope of the companion causing the transient to be more luminous by factor of $\sim 10-100$ and extending the timescale of emission by a few days.