Gravitational wave extraction in simulations of rotating stellar core collapse
We perform simulations of general relativistic rotating stellar core collapse and compute the gravitational waves (GWs) emitted in the core-bounce phase of three representative models via multiple techniques. The simplest technique, the quadrupole formula (QF), estimates the GW content in the spacetime from the mass-quadrupole tensor only. It is strictly valid only in the weak-field and slow-motion approximation. For the first time, we apply GW extraction methods in core collapse that are fully curvature based and valid for strongly radiating and highly relativistic sources. These techniques are not restricted to weak-field and slow-motion assumptions. We employ three extraction methods computing (i) the Newman-Penrose (NP) scalar Ψ_4, (ii) Regge-Wheeler-Zerilli-Moncrief master functions, and (iii) Cauchy-characteristic extraction (CCE) allowing for the extraction of GWs at future null infinity, where the spacetime is asymptotically flat and the GW content is unambiguously defined. The latter technique is the only one not suffering from residual gauge and finite-radius effects. All curvature-based methods suffer from strong nonlinear drifts. We employ the fixed-frequency integration technique as a high-pass waveform filter. Using the CCE results as a benchmark, we find that finite-radius NP extraction yields results that agree nearly perfectly in phase, but differ in amplitude by ~1%–7% at core bounce, depending on the model. Regge-Wheeler-Zerilli-Moncrief waveforms, while, in general, agreeing in phase, contain spurious high-frequency noise of comparable amplitudes to those of the relatively weak GWs emitted in core collapse. We also find remarkably good agreement of the waveforms obtained from the QF with those obtained from CCE. The results from QF agree very well in phase and systematically underpredict peak amplitudes by ~5%–11%, which is comparable to the NP results and is certainly within the uncertainties associated with core collapse physics.
Additional Information© 2011 American Physical Society. Received 2 December 2010; published 8 March 2011. We are happy to acknowledge helpful exchanges with E. Abdikamalov, P. Ajith, A. Burrows, N. T. Bishop, P. Cerdá-Durán, P. Diener, H. Dimmelmeier, J. Kaplan, E. O'Connor, E. Pazos, D. Pollney, E. Seidel, R. O'Shaughnessy, K. Thorne, and S. Teukolsky. This work is supported by the Sherman Fairchild Foundation and by the National Science Foundation under Grants No. AST- 0855535, No. OCI-0721915, No. PHY-0904015, No. OCI-0905046, and No. OCI-0941653. C.D.O. and C. R. wish to thank Chris Mach for support of the group servers at TAPIR on which much of the code development and testing was carried out. Results presented in this article were obtained through computations on the Caltech compute cluster "Zwicky" (NSF MRI Grant No. PHY-0960291), on the NSF Teragrid under Grant No. TGPHY100033, on machines of the Louisiana Optical Network Initiative under Grant No. loni_numrel05, and at the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. U. S. acknowledges support from the Ramón y Cajal Programme of the Spanish Ministry of Education and Science, from FCT-Portugal through Grant No. PTDC/FIS/098025/2008, and allocations through the TeraGrid Advanced Support Program under Grant No. PHY-090003 at NICS and the Centro de Supercomputación de Galicia (CESGA, Project No. ICTS-2009-40).
Published - Reisswig2011p13204Phys_Rev_D.pdf