Takami Kuroda, Tomoya Takiwaki, Kei Kotake
We study properties of gravitational waves (GWs) from rotating core-collapse of a 15 solar mass star by performing three-dimensional general-relativistic hydrodynamic simulations with an approximate neutrino transport. By parametrically changing the precollapse angular momentum, we focus on the effects of rotation on the GW signatures in the early postbounce evolution. Regarding three-flavor neutrino transport, we solve the energy-averaged set of radiation energy and momentum. In addition to the gravitational quadrupole radiation from matter motions, we take into account GWs from anisotropic neutrino emission. With these computations, our results present evidence that non-axisymmetric instabilities play an essential role in determining the GW signatures in the rotating postbounce evolution. For our rapidly rotating models, we show that precollapse density inhomogeneities give rise to millisecond variations in the waveforms. During prompt convection, we find that the waveforms show narrow-band and highly quasi-periodic signals. We point out that such feature reflects the growth of the one-armed spiral modes that develop under the influence of the standing-accretion-shock instability and the low-$T/|W|$ instability. The typical frequency of the quasi-periodic waveforms can be well explained by the propagating acoustic waves. Although the GW signals exhibit strong variability between the two polarizations and different observer directions, they are within the realm of next generation detectors such as by KAGRA and Advanced LIGO, if the source with sufficient angular momentum is located in our Galaxy.
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http://arxiv.org/abs/1304.4372
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