dc.description.abstract |
Gravitational waves (GW) generated during a core-collapse supernova open a
window into the heart of the explosion. At core bounce, progenitors with rapid core
rotation rates exhibit a characteristic GW signal which can be used to constrain the
properties of the core of the progenitor star. We investigate the dynamics of rapidly
rotating core collapse, focusing on hydrodynamic waves generated by the core bounce
and the GW spectrum they produce. The centrifugal distortion of the rapidly rotating
proto-neutron star (PNS) leads to the generation of axisymmetric quadrupolar oscil-
lations within the PNS and surrounding envelope. Using linear perturbation theory,
we estimate the frequencies, amplitudes, damping times, and GW spectra of the os-
cillations. Our analysis provides a qualitative explanation for several features of the
GW spectrum and shows reasonable agreement with nonlinear hydrodynamic simu-
lations, although a few discrepancies due to non-linear/rotational e ects are evident.
The dominant early postbounce GW signal is produced by the fundamental quadrupo-
lar oscillation mode of the PNS, at a frequency 0:70 kHz . f . 0:80 kHz, whose energy
is largely trapped within the PNS and leaks out on a 10 ms timescale. Quasi-radial
oscillations are not trapped within the PNS and quickly propagate outwards until
they steepen into shocks. Both the PNS structure and Coriolis/centrifugal forces have
a strong impact on the GW spectrum, and a detection of the GW signal can therefore
be used to constrain progenitor properties. |
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