Ernazar Abdikamalov, Christian D. Ott, Luciano Rezzolla, Luc Dessart, Harald Dimmelmeier, A. Marek, and H.-T. Janka
Submitted to Phys. Rev. D., arXiv:0910.2703
- Electron Fraction Trajectories -
Abstract
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The accretion-induced collapse (AIC) of a white dwarf (WD) may lead
to the formation of a protoneutron star and a collapse-driven
supernova explosion. This process represents a path alternative to
thermonuclear disruption of accreting white dwarfs in Type Ia
supernovae. In the AIC scenario, the supernova explosion energy is
expected to be small and the resulting transient short-lived, making
it hard to detect by electromagnetic means alone. Neutrino and
gravitational-wave (GW) observations may provide crucial information
necessary to reveal a potential AIC. Motivated by the need for
systematic predictions of the GW signature of AIC, we present
results from an extensive set of general-relativistic AIC
simulations using a microphysical finite-temperature equation of
state and an approximate treatment of deleptonization during
collapse. Investigating a set of 114 progenitor models in
axisymmetric rotational equilibrium, with a wide range of rotational
configurations, temperatures and central densities, and resulting
white dwarf masses, we extend previous Newtonian studies and find
that the GW signal has a generic shape akin to what is
known as a ``Type~III'' signal in the literature. Despite this
reduction to a single type of waveform, we show that the emitted GWs
carry information that can be used to constrain the progenitor and
the postbounce rotation. We discuss the detectability of the emitted
GWs, showing that the signal-to-noise ratio for current or
next-generation interferometer detectors could be high enough to
detect such events in our Galaxy. Furthermore, we contrast the GW
signals of AIC and rotating massive star iron core collapse and find
that they can be distinguished, but only if the distance to the
source is known and a detailed reconstruction of the GW time series
from detector data is possible. Some of our AIC models form massive
quasi-Keplerian accretion disks after bounce. The disk mass is very
sensitive to progenitor mass and angular momentum distribution. In
rapidly differentially rotating models whose precollapse masses are
significantly larger than the Chandrasekhar mass, the
resulting disk mass can be as large as ~0.8 solar masses. Slowly
and/or uniformly rotating models that are limited to masses near the
Chandrasekhar mass produce much smaller disks or no disk at
all. Finally, we find that the postbounce cores of rapidly spinning
white dwarfs can reach sufficiently rapid rotation to develop a
gravito-rotational bar-mode instability. Moreover, many of our
models exhibit sufficiently rapid and differential rotation to
become subject to recently discovered low-E_rot/|W|-type dynamical
instabilities.
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Here we provide the electron fraction (Y_e) profiles used in the deleptonization
scheme described in detail in the paper. The Y_e data were obtained in the
Newtonian multi-group flux-limited diffusion neutrino radiation-hydrodynamics AIC simulations
of Dessart et al. 2006.
Below are the Y_e(rho) data used to setup the initial white dwarf Y_e distribution. They are based on data of
Dessart et al. 2006 at 7 ms into their simulation.
