Gravitational Radiation from Newtonian Rotational Core Collapse

Thomas Zwerger & Ewald Müller

Among potential sources which emit gravitational waves core collapse supernova are thought to be one of the most promising sources to be detected on earth by gravitational wave detectors

For this reason we have performed a comprehensive set of axially symmetric (Newtonian) hydrodynamical simulations of collapsing rotating stellar cores to determine the strength, form and frequency of the gravitational wave signal produced in such events. In order to examine a large set of initial conditions we have approximated the collapsing core by a rotating polytrope and used a simplified analytical equation of state.

Initial Models:

Initial models have been calculated with the method of Eriguchi & Müller (A&A 147 (1984), 161) and are rotating Gamma=4/3 polytropes in rotational equilibrium. Collapse was induced by suddenly reducing Gamma to a specified value. Varying the initial amount and distribution of angular momentum we have computed a total of 81 initial models and followed their evolution well beyond core bounce. The models initially rotated according to the prescribed rotation law

Omega (R) = Omega_0 / (1 + (R / A)^2),

where R is the distance from the rotation axis. The constant Omega_0 is uniquely related to the parameter beta_i, which gives the initial ratio of the rotational energy and the gravitational binding energy of the configuration. The parameter A determines the initial angular momentum distribution. For large values of A (compared to the size of the initial model) one obtains almost rigidly rotating configurations, while small values of A correspond to strongly differentially rotating ones. More details can be found in our paper (gzip'd postscript, 223 kB) published in (A&A 320 (1997), 209).

Results:

Maximum dimensionless gravitational wave amplitude (gzip'd Postscript, 6 KB).: The "error bars" give the frequency range which contains most of the signal strength. NOTE that it is assumed that the source is located at a distance of 10 Mpc. The amplitudes of the four models calculated by Mönchmeyer etal. (A&A, 1991, 246, 417) are also shown and are marked by crosses.

The following two entries contain example pages from our comprehensive gravitational wave signal catalogue (gzip'd postscript, 1.4 MB).

wave amplitudes of models A1B3G(1-5) (gzip'd postscript, 17 KB)

spectral energy densities of models A1B3G(1-5) (gzip'd postscript, 60 KB)

In order to obtain the quadrupole wave forms (amplitude A_E2_20 [cm] as a function of time) in digital form for all models click here (gzip'd uuencoded, 1.8 MB). Besides the data the uuencoded, tar-file also contains an IDL program to read the data.

Ewald Müller / ewald@mpa-garching.mpg.de/24. November 1997