Paper: astro-ph/0601603
Date: Thu, 26 Jan 2006 15:06:11 GMT (3565kb)

Title: Multi-Dimensional Simulations of the Accretion-Induced Collapse of White
Dwarfs to Neutron Stars

Authors: Luc Dessart, Adam Burrows, Christian Ott, Eli Livne, Sung-Chul Yoon,
Norbert Langer

Comments: 25 pages, 19 figures, submitted to ApJ, high resolution of the paper
available at http://hermes.as.arizona.edu/~luc/aic/aic.html
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We present 2.5D radiation-hydrodynamics simulations of the accretion-induced
collapse (AIC) of white dwarfs, starting from 2D rotational equilibrium
configurations. Electron capture leads to the collapse to nuclear densities of
these cores within a few tens of milliseconds. The shock generated at bounce
moves slowly, but steadily, outwards. Within 50-100ms, the stalled shock breaks
out of the white dwarf along the poles. The blast is followed by a
neutrino-driven wind that develops within the white dwarf, in a cone of ~40deg
opening angle about the poles, with a Mdot of 5-8 x 10^{-3} Msun/s. The ejecta
have an entropy on the order of 20-50 k_B/baryon, and an electron fraction
distribution that is bimodal. By the end of the simulations, at >600ms after
bounce, the explosion energy has reached 3-4 x 10^49 erg and the outflowing
mass has reached a few times 0.001Msun. We estimate the asymptotic explosion
energies to be lower than 10^50 ergs, significantly lower than those inferred
in the core collapse of massive progenitors. AIC of WDs thus represents one
instance where a neutrino mechanism leads undoubtedly to a successful, albeit
weak, explosion. We document in detail the numerous effects of the fast
rotation of the progenitors: the neutron stars are aspherical; the
``\nu_{\mu}'' and \bar{\nu}_e luminosities are reduced compared to the \nu_e
luminosity; the deleptonized region has a butterfly shape; the neutrino flux
and electron fraction depend strongly upon latitude (a la von Zeipel); and a
quasi-Keplerian 0.1-0.5Msun accretion disk is formed [abridged].

\\ ( http://arXiv.org/abs/astro-ph/0601603 , 3566kb)