Axisymmetric General Relativistic Simulations of the Accretion-Induced Collapse of White Dwarfs

TL;DR

This study conducts extensive axisymmetric general relativistic simulations of white dwarf accretion-induced collapse, predicting gravitational wave signals, disk formation, and rotational instabilities, with implications for detection and understanding supernova mechanisms.

Contribution

It provides the first systematic set of 114 GR simulations of AIC, analyzing GW signatures, disk formation, and rotational instabilities across diverse progenitor models.

Findings

GW signals have a generic 'Type III' shape.

Detectability of GWs in our Galaxy is promising with current/future detectors.

Rapidly rotating models can develop nonaxisymmetric instabilities.

Abstract

(Abridged.) 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. 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 rotational equilibrium, with a wide range of rotational configurations, temperatures and central densities, 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. 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. Some of our AIC models form massive quasi-Keplerian accretion disks after bounce. In rapidly differentially rotating models, the disk mass can be as large as ~0.8-Msun. Slowly and/or uniformly rotating models produce much smaller disks. Finally, we find that the postbounce cores of rapidly spinning white dwarfs can reach sufficiently rapid rotation to develop a nonaxisymmetric rotational instability.