Phenomenological model for the gravitational-wave signal from precessing binary black holes with two-spin effects

Abstract

The properties of compact binaries, such as masses and spins, are imprinted in the gravitationalwaves they emit and can be measured using parameterised waveform models. Accurately and efficiently describing the complicated precessional dynamics of the various angular momenta of the system in these waveform models is the object of active investigation. One of the key models extensively used in the analysis of LIGO and Virgo data is the single-precessing-spin waveform model IMRPhenomPv2. In this article we present a new model IMRPhenomPv3 which includes the effects of two independent spins in the precession dynamics. Whereas IMRPhenomPv2 utilizes a single-spin frequency-dependent post-Newtonian rotation to describe precession effects, the improved model, IMRPhenomPv3, employs a double-spin rotation that is based on recent developments in the description of precessional dynamics. Besides double-spin precession, the improved model benefits from a more accurate description of precessional effects. We validate our new model against a large set of precessing numerical-relativity simulations. We find that IMRPhenomPv3 has better agreement with the inspiral portion of precessing binary-black-hole simulations and is more robust across a larger region of the parameter space than IMRPhenomPv2. As a first application we analyse, for the first time, the gravitational-wave event GW151226 with a waveform model that describes two-spin precession. Within statistical uncertainty our results are consistent with published results. IMRPhenomPv3 will allow studies of the measurability of individual spins of binary black holes using GWs and can be used as a foundation upon which to build further improvements, such as modeling precession through merger, extending to higher multipoles, and including tidal effects.PACS numbers: 04.80. Nn, 04.25.dg, 95.85.Sz, 97.80.-d arXiv:1809.10113v1 [gr-qc]

Including higher order multipoles in gravitational-wave models for precessing binary black holes

“…q = 6: When comparing to this NR simulation we find both models perform substantially worse than the q = 5 cases with even PhenomPv3 outperforming PhenomPv3HM with matches as low as 0.898. We have verified that we obtain matches of ∼ 0.97 when restricting the NR waveform to just the = 2 multipoles, consistent with our previous study [49]. We conclude that either our model is outside its range of validity or that this NR simulation is inaccurate for the higher multipoles, however, our results are robust against NR simulations of this configuration at multiple resolutions.…”

“…In this context the optimal waveform maximises the overlap over coalescence time, template phase and polarisation angle and the intrinsic parameters are fixed to the values from the NR simulation. As shown in [49] SEOBNRv3 and PhenomPv3 have overlaps of ∼ 99 % and ∼ 98 % respectively to this NR waveform when only the = 2 multipoles are considered. When we include higher order multipoles in the NR waveform we find the overlap drops to only ∼ 92 % and ∼ 93 % respectively.…”

“…III A in Ref. [49] for details. Figure 2 shows the orientation-averaged-mismatch [49] as a function of the total mass of the binary for an inclination angle ι = π/3.…”

“…[49] for details. Figure 2 shows the orientation-averaged-mismatch [49] as a function of the total mass of the binary for an inclination angle ι = π/3. Here ι is the angle between the Newtonian orbital angular momentum and the line of sight at the start frequency of the NR waveform.…”

“…The BHs are allowed to precess and we also model the contribution to the GW signal from higher order multipoles. This combines the progress made in two earlier models: a precessing-binary model that includes accurate two-spin precession effects during the inspiral [54,55] (PhenomPv3 [49]), and an approximate higher-multipole aligned-spin model (PhenomHM [10]). Figure 1 demonstrates the improved accuracy that is achievable by our new model, PhenomPv3HM, compared to other existing models that include the effect of spin precession, but not higher order multipoles.…”