Constraint preserving boundary conditions for the Z4c formulation of general relativity

Ruiz, Milton; Hilditch, David; Bernuzzi, Sebastiano

doi:10.1103/physrevd.83.024025

Cited by 68 publications

(83 citation statements)

References 59 publications

(109 reference statements)

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“…It was also pointed out in [58] that CCZ4 may show instability depending on the value of the damping parameter (we used k 1 = 0.05, k 2 = 0, for k 3 = 1). Our result indicates that a deeper study of the properties of the CCZ4 formulation (and the very similar Z4c formulation [59]) is needed for its use at very low resolution. At the same time, the result that the PPM scheme is less accurate does not come as a surprise, since it is formally a thirdorder method instead of a fifth-order one (like WENO).…”

Section: B Accuracy In the Determination Of Merger Timementioning

confidence: 98%

Modeling equal and unequal mass binary neutron star mergers using public codes

et al. 2016

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We present three-dimensional simulations of the dynamics of binary neutron star (BNS) mergers from the late stage of the inspiral process up to ∼ 20 ms after the system has merged, either to form a hyper-massive neutron star (NS) or a rotating black hole (BH). We investigate five equalmass models of total gravitational mass 2.207, 2.373, 2.537, 2.697 and 2.854 M , respectively; and four unequal mass models with M ADM 2.53 M and q 0.94, 0.88, 0.83, and 0.77 (whereis the mass ratio). We use a semi-realistic equation of state (EOS), namely the seven-segment piece-wise polytropic SLyPP with a thermal component given by Γ th = 1.8. We have also compared the resulting dynamics (for one model) using both, the BSSN-NOK and CCZ4 methods for the evolution of the gravitational sector, and also different reconstruction methods for the matter sector, namely PPM, WENO and MP5. Our results show agreement and high resolution, but superiority of BSSN-NOK supplemented by WENO reconstruction at lower resolutions.One of the important characteristics of the present investigation is that for the first time, it has been done using only publicly available open source software: the Einstein Toolkit code, deployed for the dynamical evolution; and the LORENE code, for the generation of the initial models. All of the source code and parameters used for the simulations have been made publicly available. This not only makes it possible to re-run and re-analyze our data, but also enables others to directly build upon this work for future research.

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Section: B Accuracy In the Determination Of Merger Timementioning

confidence: 98%

Modeling equal and unequal mass binary neutron star mergers using public codes

et al. 2016

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“…For the first setup, we substitute the outermost level (l = 0) by a multipatch cubed-sphere grid [45,[54][55][56]] on which we do not solve the GRHD equations. The spheres allow us to apply constraint preserving boundary conditions [57]. This 'shell' setup is denoted in Tab.…”

Section: B Evolutionsmentioning

confidence: 99%

Gravitational waves and mass ejecta from binary neutron star mergers: Effect of the mass ratio

et al. 2017

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We present new (3+1)D numerical relativity simulations of the binary neutron star (BNS) merger and postmerger phase. We focus on a previously inaccessible region of the binary parameter space spanning the binary's mass-ratio q ∼ 1.00 − 1.75 for different total masses and equations of state, and up to q ∼ 2 for a stiff BNS system. We study the mass-ratio effect on the gravitational waves (GWs) and on the possible electromagnetic emission associated to dynamical mass ejecta. We compute waveforms, spectra, and spectrograms of the GW strain including all the multipoles up to l = 4. The mass-ratio has a specific imprint on the GW multipoles in the late-inspiral-merger signal, and it affects qualitatively the spectra of the merger remnant. The multipole effect is also studied by considering the dependency of the GW spectrograms on the source's sky location. Unequal mass BNSs produce more ejecta than equal mass systems with ejecta masses and kinetic energies depending almost linearly on q. We estimate luminosity peaks and light curves of macronovae events associated to the mergers using a simple approach. For q ∼ 2 the luminosity peak is delayed for several days and can be up to four times larger than for the q = 1 cases. The macronova emission associated with the q ∼ 2 BNS is more persistent in time and could be observed for weeks instead of few days (q = 1) in the near infrared. Finally, we estimate the flux of possible radio flares produced by the interaction of relativistic outflows with the surrounding medium. Also in this case a large q can significantly enhance the emission and delay the peak luminosity. Overall, our results indicate that BNS merger with large mass ratio have EM signatures distinct from the equal mass case and more similar to black hole -neutron star binaries.

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“…[35,94]. We also use the Z4c scheme [53,95] with constraint-preserving boundary conditions [53,96]. The BAM grid setup consists of seven refinement levels.…”

Section: Dynamical Evolutionsmentioning

confidence: 99%

Binary neutron stars with generic spin, eccentricity, mass ratio, and compactness: Quasi-equilibrium sequences and first evolutions

Dietrich¹,

Moldenhauer²,

et al. 2015

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Information about the last stages of a binary neutron star inspiral and the final merger can be extracted from quasiequilibrium configurations and dynamical evolutions. In this article, we construct quasiequilibrium configurations for different spins, eccentricities, mass ratios, compactnesses, and equations of state. For this purpose we employ the SGRID code, which allows us to construct such data in previously inaccessible regions of the parameter space. In particular, we consider spinning neutron stars in isolation and in binary systems; we incorporate new methods to produce highly eccentric and eccentricity-reduced data; we present the possibility of computing data for significantly unequal-mass binaries with mass ratios q ≃ 2; and we create equal-mass binaries with individual compactness up to C ≃ 0.23. As a proof of principle, we explore the dynamical evolution of three new configurations. First, we simulate a q ¼ 2.06 mass ratio which is the highest mass ratio for a binary neutron star evolved in numerical relativity to date. We find that mass transfer from the companion star sets in a few revolutions before merger and a rest mass of ∼10 −2 M ⊙ is transferred between the two stars. This amount of mass accretion corresponds to ∼10 51 ergs of accretion energy. This configuration also ejects a large amount of material during merger (∼7.6 × 10 −2 M ⊙ ), imparting a substantial kick to the remnant neutron star. Second, we simulate the first merger of a precessing binary neutron star. We present the dominant modes of the gravitational waves for the precessing simulation, where a clear imprint of the precession is visible in the (2,1) mode. Finally, we quantify the effect of an eccentricity-reduction procedure on the gravitational waveform. The procedure improves the waveform quality and should be employed in future precision studies. However, one also needs to reduce other errors in the waveforms, notably truncation errors, in order for the improvement due to eccentricity reduction to be effective.

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Constraint preserving boundary conditions for the Z4c formulation of general relativity

Cited by 68 publications

References 59 publications

Modeling equal and unequal mass binary neutron star mergers using public codes

Modeling equal and unequal mass binary neutron star mergers using public codes

Gravitational waves and mass ejecta from binary neutron star mergers: Effect of the mass ratio

Binary neutron stars with generic spin, eccentricity, mass ratio, and compactness: Quasi-equilibrium sequences and first evolutions

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