Gravitational waveforms for high spin and high mass-ratio binary black holes: A synergistic use of numerical-relativity codes

Abstract

Observation and characterisation of gravitational waves from binary black holes requires accurate knowledge of the expected waveforms. The late inspiral and merger phase of the waveform is obtained through direct numerical integration of the full 3-dimensional Einstein equations. The Spectral Einstein Code (SpEC) utilizes a multi-domain pseudo-spectral method tightly adapted to the geometry of the black holes; it is computationally efficient and accurate, but-for high mass-ratios and large spins-sometimes requires manual fine-tuning for the merger-phase of binaries. The Einstein Toolkit (ET) employs finite difference methods and the moving puncture technique; it is less computationally efficient, but highly robust. For some mergers with high mass ratio and large spins, the efficient numerical algorithms used in SpEC have failed, whereas the simpler algorithms used in the ET were successful. Given the urgent need of testing the accuracy of waveform models currently used in LIGO and Virgo inference analyses for high mass ratios and spins, we present here a synergistic approach to numericalrelativity: We combine SpEC and ET waveforms into complete inspiral-merger-ringdown waveforms, taking advantage of the computational efficiency of the pseudo-spectral code during the inspiral, and the robustness of the finite-difference code at the merger. We validate our method against a case where complete waveforms from both codes are available, compute three new hybrid numerical-relativity waveforms, and compare them with analytical waveform models currently used in LIGO and Virgo science. All the waveforms and the hybridization code are publicly available.

Multipolar effective-one-body waveforms for precessing binary black holes: Construction and validation

“…Significant progress has been made in recent years by several NR groups to improve the coverage of the BBH parameter space [53][54][55][56][57][58], mainly motivated by the calibration of analytical waveform models and surrogate models used in LIGO and Virgo data analysis. While large strides have been made for aligned-spin cases, the exploration of precessing waveforms has been mostly limited to q ≤ 4; χ 1;2 ≡ j χ 1;2 j ≤ 0.8, typically 15-20 orbital cycles before merger, and a large region of parameter space remains to be explored.…”

“…So far, NR simulations of BBHs have been mostly limited to mass ratio ≤ 4 and (dimensionless) spins ≤ 0.8, and length of 15-20 orbital cycles before merger [53][54][55][56][57] (however, see Ref. [58] where simulations with larger spins and mass ratios were obtained through a synergistic use of NR codes). Here, to test our newly constructed EOB precessing waveform model, we enhance the NR parameter-space coverage, while maintaining a manageable computational TABLE I.…”

Spin effects in the effective field theory approach to Post-Minkowskian conservative dynamics

“…3 In addition, finite-size effects can be readily incorporated as a series of corrections beyond minimal coupling constrained solely by diffeomorphism invariance [30,31] 1 Needless to say, numerical simulations for spinning black holes in the strongly coupled regime are also significantly more involved than non-rotating counterparts, e.g. [29]. 2 On the other hand, spin-dependent radiation effects are only known to NLO to quadratic order in the spins [28,[48][49][50][51][52][53][54][55], and N 2 LO for spin-orbit corrections [56].…”

Gravitational radiation from inspiralling compact objects: Spin-spin effects completed at the next-to-leading post-Newtonian order

“…We can also transform the above expression as function of the conserved-norm spin vector. Using (17) we have…”

“…This is notoriously important when spin effects are manifest, e.g., [15], in particular due to the expectation that binary black holes may be rapidly rotating, e.g., [16]. While numerical simulations are required for the late stages of the dynamics, e.g., [17], the post-Newtonian (PN) expansion has provided the groundwork to tackle the weak-field/small-velocity inspiral regime [18][19][20][21]. So far, PN studies have been carried out notably in the conservative sector, both for nonspinning [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] and spinning bodies [42][43][44][45][46][47][48][49][50][51][52][53][54][55], using various tools [18][19][20][21].…”