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Published February 15, 2010 | public
Journal Article

Axisymmetric general relativistic simulations of the accretion-induced collapse of white dwarfs


The accretion-induced collapse (AIC) of a white dwarf 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-tonoise 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 0:8M. 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 gravitorotational 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.

Additional Information

© 2010 The American Physical Society. Received 15 October 2009; published 10 February 2010. It is a pleasure to thank Alessandro Bressan, Adam Burrows, Frank Löffler, John Miller, Stephan Rosswog, Nikolaos Stergioulas, Sung-Chul Yoon, Shin Yoshida, and Burkhard Zink for helpful comments and discussions. This work was supported by the Deutsche Forschungsgemeinschaft through the Transregional Collaborative Research Centers SFB/TR 27 ''Neutrinos and Beyond,'' SFB/TR 7 ''Gravitational Wave Astronomy,'' by the Cluster of Excellence EXC 153 ''Origin and Structure of the Universe'' (http://www.universe-cluster.de), and by ''CompStar,'' a Research Networking Programme of the European Science Foundation. C. D. O. acknowledges partial support by the National Science Foundation under Grant No. AST-0855535. The simulations were performed on the computer clusters of the Albert Einstein Institute, on machines of the Louisiana Optical Network Initiative under allocation LONI_numrel04, and on the NSF Teragrid under allocation TG-MCA02N014.

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