A Model for Gravitational Wave Emission from Neutrino-Driven Core-Collapse Supernovae
Using a suite of progenitor models, neutrino luminosities, and two-dimensional simulations, we investigate the matter gravitational wave (GW) emission from postbounce phases of neutrino-driven core-collapse supernovae. These phases include prompt and steady-state convection, the standing accretion shock instability (SASI), and asymmetric explosions. For the stages before explosion, we propose a model for the source of GW emission. Downdrafts of the postshock-convection/SASI region strike the protoneutron star "surface" with large speeds and are decelerated by buoyancy forces. We find that the GW amplitude is set by the magnitude of deceleration and, by extension, the downdraft's speed and the vigor of postshock-convective/SASI motions. However, the characteristic frequencies, which evolve from ~100 Hz after bounce to ~300-400 Hz, are practically independent of these speeds (and turnover timescales). Instead, they are set by the deceleration timescale, which is in turn set by the buoyancy frequency at the lower boundary of postshock convection. Consequently, the characteristic GW frequencies are dependent upon a combination of core structure attributes, specifically the dense-matter equation of state (EOS) and details that determine the gradients at the boundary, including the accretion-rate history, the EOS at subnuclear densities, and neutrino transport. During explosion, the high frequency signal wanes and is replaced by a strong low frequency, ~10s of Hz, signal that reveals the general morphology of the explosion (i.e., prolate, oblate, or spherical). However, current and near-future GW detectors are sensitive to GW power at frequencies ≳50 Hz. Therefore, the signature of explosion will be the abrupt reduction of detectable GW emission.
Additional Information© 2009 American Astronomical Society. Print publication: Issue 2 (2009 December 20); received 2009 July 24; accepted for publication 2009 November 2; published 2009 December 2. We acknowledge helpful discussions with and input from Casey Meakin and Eric Agol. J.W.M. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0802315. C.D.O. is supported by a Sherman Fairchild postdoctoral fellowship at Caltech, by an NSF award under grant number AST-0855535, and by an Otto Hahn Prize awarded by theMax Planck Society. A.B. acknowledges support for this work from the Scientific Discovery through Advanced Computing (SciDAC) program of the DOE, under grant number DE-FG02-08ER41544.We acknowledge that the work reported in this paper was substantially performed at the TIGRESS high performance computer center at Princeton University which is jointly supported by the Princeton Institute for Computational Science and Engineering and the Princeton University Office of Information Technology and on the ATHENA cluster at the University of Washington. Further computations were performed on the NSF Teragrid under grant TG-MCA02N014, on machines of the Louisiana Optical Network Initiative under grant LONI_NUMREL04, and at the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the US Department of Energy under contract DE-AC03-76SF00098.
Published - Murphy2009p6663Astrophys_J.pdf