What can the accretion-induced collapse of white dwarfs really explain?

The accretion-induced collapse (AIC) of a white dwarf into a. neutron star has been invoked to explain gamma-ray bursts, Type Ia supernovae, and a num ber of problematic neutron star populations and specific binary systems. Th e ejecta from this collapse has also been claimed as a source of r-process nucleosynthesis. So far, most AIC studies have focused on determining the e vent rates from binary evolution models and less attention has been directe d toward understanding the collapse itself. However, the collapse of a whit e dwarf into a neutron star is followed by the ejection of rare neutron-ric h isotopes. The observed abundance of these chemical elements may set a mor e reliable limit on the rate at which AICs have taken place over the histor y of the Galaxy. In this paper, we present a thorough study of the collapse of a massive white dwarf in one- and two-dimensions and determine the amou nt and composition of the ejected material. We discuss the importance of th e input physics (equation of state, neutrino transport, rotation) in determ ining these quantities. These simulations affirm that AICs are too baryon r ich to produce gamma-ray bursts and do not eject enough nickel to explain T ype Ia supernovae (with the possible exception of a small subclass of extre mely low-luminosity Type las). Although nucleosynthesis constraints limit t he number of neutron stars formed via AICs to less than or similar to 0.1% of the total Galactic neutron star population, AICs remain a viable scenari o for forming systems of neutron stars that are difficult to explain with T ype II core-collapse supernovae.