A&A 393, 523-542 (2002)

DOI: 10.1051/0004-6361:20021053

## Relativistic simulations of rotational core collapse II. Collapse dynamics and gravitational radiation

**H. Dimmelmeier**

^{1}, J. A. Font^{1, 2}and E. Müller^{1}^{1}Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany

^{2}Departamento de Astronomía y Astrofísica, Universidad de Valencia, 46100 Burjassot (Valencia), Spain

(Received 12 April 2002 / Accepted 4 July 2002 )

** Abstract **

We have performed hydrodynamic simulations of relativistic
rotational supernova core collapse in axisymmetry and have computed
the gravitational radiation emitted by such an event. The Einstein
equations are formulated using the conformally flat metric
approximation, and the corresponding hydrodynamic equations are
written as a first-order flux-conservative hyperbolic
system. Details of the methodology and of the numerical code have
been given in an accompanying paper. We have simulated the evolution
of 26 models in both Newtonian and relativistic gravity. The
initial configurations are differentially rotating relativistic
4 / 3-polytropes in equilibrium which have a central density of
. Collapse is initiated by decreasing
the adiabatic index to some prescribed fixed value. The equation of
state consists of a polytropic and a thermal part for a more
realistic treatment of shock waves. Any microphysics like
electron capture and neutrino transport is neglected.
Our simulations show that the three different types of rotational
supernova core collapse and gravitational waveforms identified in
previous Newtonian simulations (regular collapse, multiple bounce
collapse, and rapid collapse) are also present in relativistic
gravity. However, rotational core collapse with multiple bounces is
only possible in a much narrower parameter range in relativistic
gravity. The relativistic models cover almost the same range of
gravitational wave amplitudes
(
for a
source at a distance of 10 kpc) and
frequencies (
) as the
corresponding Newtonian ones. Averaged over all models, the total
energy radiated in the form of gravitational waves is
in the relativistic case, and
in the Newtonian case. For all collapse models that are of the
same type in both Newtonian and relativistic gravity, the
gravitational wave signal is of lower amplitude. If the collapse
type changes, either weaker or stronger signals are found in the
relativistic case. For a given model, relativistic gravity can
cause a large increase of the characteristic signal frequency of up
to a factor of five, which may have important consequences for the signal
detection. Our study implies that the prospects for
detection of gravitational wave signals from axisymmetric supernova
rotational core collapse do not improve when taking into account
relativistic gravity. The gravitational wave signals obtained in our
study are within the sensitivity range of the first generation laser
interferometer detectors if the source is located within the Local
Group. An online catalogue containing the gravitational wave signal
amplitudes and spectra of all our models is available at the URL
http://www.mpa-garching.mpg.de/Hydro/hydro.html.

**Key words:**gravitation

**--**gravitational waves

**--**hydrodynamics

**--**stars: neutron

**--**stars: rotation

**--**stars: supernovae: general

Offprint request: H. Dimmelmeier, harrydee@mpa-garching.mpg.de

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**©**

*ESO 2002*