Numerical relativity simulations of neutron star merger remnants using conservative mesh refinement
Abstract
We study equal- and unequal-mass neutron star mergers by means of new numerical relativity simulations in which the general relativistic hydrodynamics solver employs an algorithm that guarantees mass conservation across the refinement levels of the computational mesh. We consider eight binary configurations with total mass M=2.7M_⊙, mass ratios q=1 and q=1.16, four different equations of state (EOSs) and one configuration with a stiff EOS, M=2.5M_⊙ and q=1.5, which is one of the largest mass ratios simulated in numerical relativity to date. We focus on the postmerger dynamics and study the merger remnant, the dynamical ejecta, and the postmerger gravitational wave spectrum. Although most of the merger remnants are a hypermassive neutron star collapsing to a black hole+disk system on dynamical time scales, stiff EOSs can eventually produce a stable massive neutron star. During the merger process and on very short time scales, about ∼10^(−3) –10^(−2) M_⊙ of material become unbound with kinetic energies ∼10^(50) erg. Ejecta are mostly emitted around the orbital plane and favored by large mass ratios and softer EOS. The postmerger wave spectrum is mainly characterized by the nonaxisymmetric oscillations of the remnant neutron star. The stiff EOS configuration consisting of a 1.5M_⊙ and a 1.0M_⊙ neutron star, simulated here for the first time, shows a rather peculiar dynamics. During merger the companion star is very deformed; about ∼0.03M_⊙ of the rest mass becomes unbound from the tidal tail due to the torque generated by the two-core inner structure. The merger remnant is a stable neutron star surrounded by a massive accretion disk of rest mass ∼0.3M_⊙. This and similar configurations might be particularly interesting for electromagnetic counterparts. Comparing results obtained with and without the conservative mesh refinement algorithm, we find that postmerger simulations can be affected by systematic errors if mass conservation is not enforced in the mesh refinement strategy. However, mass conservation also depends on grid details and on the artificial atmosphere setup; the latter are particularly significant in the computation of the dynamical ejecta.
Additional Information
© 2015 American Physical Society. Received 7 April 2015; Published 12 June 2015. It is a pleasure to thank Marcus Bugner, Enno Harms, David Hilditch, Nathan Johnson-McDaniel, Niclas Moldenhauer, Alessandro Nagar, Stephan Rosswog, Kentaro Takami, and Andreas Weyhausen for helpful discussions. This work was supported in part by DFG Grant SFB/Transregio 7 "Gravitational Wave Astronomy" and the Graduierten-Akademie Jena. S. B. acknowledges partial support from the National Science Foundation under Grants No. NSF AST-1333520, No. PHY-1404569, and No. AST-1205732. The authors also gratefully acknowledge the Gauss Centre for Supercomputing e.V. for funding this project by providing computing time on the GCS Supercomputer SuperMUC at Leibniz Supercomputing Centre and the computing time granted by the John von Neumann Institute for Computing provided on the supercomputer JUROPA at Jülich Supercomputing Centre. Additionally, this work used the Extreme Science and Engineering Discovery Environment, which is supported by National Science Foundation Grant No. ACI-1053575 and computer resources at the Institute of Theoretical Physics of the University of Jena.Attached Files
Published - PhysRevD.91.124041.pdf
Submitted - 1504.01266v1.pdf
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Additional details
- Eprint ID
- 58785
- Resolver ID
- CaltechAUTHORS:20150706-161013547
- SFB/Transregio 7
- Deutsche Forschungsgemeinschaft (DFG)
- AST-1333520
- NSF
- PHY-1404569
- NSF
- AST-1205732
- NSF
- Gauss Centre for Supercomputing
- ACI-1053575
- NSF
- Graduierten-Akademie Jena
- Created
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2015-07-07Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field