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

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

Aug 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aipc..924..457d&link_type=abstract

THE MULTICOLORED LANDSCAPE OF COMPACT OBJECTS AND THEIR EXPLOSIVE ORIGINS. AIP Conference Proceedings, Volume 924, pp. 457-459

Computer Science

Faint Blue Stars, White Dwarfs, Degenerate Stars, Nuclei Of Planetary Nebulae, Neutron Stars, Accretion And Accretion Disks, Radiative Transfer, Scattering

Scientific paper

We have performed 2.5D radiation-hydrodynamics simulations of the accretion-induced collapse (AIC) of white dwarfs, starting from 2D rotational equilibrium configurations of a 1.92-Msolar model. Electron capture leads to the collapse to nuclear densities of the core within a few tens of milliseconds. The shock generated at bounce moves slowly, but steadily, outwards. Within 50-100 ms, 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 ~ 40° opening angle about the poles, with a mass loss rate of 5 × 10-3Msolaryr-1. The ejecta have an entropy on the order of 20-50 kB/baryon, and an electron fraction distribution that is bimodal. By the end of the simulations, at >=600 ms after bounce, the explosion energy has reached 3 × 1049 erg and the total ejecta mass has reached a few times 0.001 Msolar. We estimate the asymptotic explosion energies to be slightly lower than 1050 erg, significantly lower than those inferred for standard core collapse. The AIC of white dwarfs thus represents one instance where a neutrino mechanism leads undoubtedly to a successful, albeit weak, explosion.
We summarize the numerous effects of the fast rotation of the progenitor: The neutron star is aspherical; the ``νμ'' and νe neutrino luminosities are reduced compared to the νe neutrino luminosity; the deleptonized region has a ``butterfly'' shape; the neutrino flux and electron fraction depend strongly upon latitude (à la von Zeipel) and a quasi-Keplerian 0.5-Msolar accretion disk is formed.

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