arXiv subjects

Joan Llobera-Querol

Publications and source records attributed to Joan Llobera-Querol.

5 recordsLinked to original sources

arXiv2026

Parity symmetry as a diagnostic for spin-precessing binary-black-hole waveform models

Parity invariance of general relativity imposes exact relations between waveforms and remnant properties of binary-black-hole configurations related by reversal of the in-plane spins and observer direction. We summarize these relations and construct consistency tests for spin-precessing waveform and remnant models. Applying a conservative, unmaximized overlap diagnostic to seven state-of-the-art waveform models, we find that models built from aligned-spin calibrated waveforms and parity-covariant precession dynamics satisfy the symmetry to numerical precision. The original \texttt{IMRPhenomXO4a} and \texttt{IMRPhenomXPNR} implementations instead exhibit median parity residuals of approximately $1.6\times10^{-3}$ with broad upper tails, while \texttt{NRSur7dq4} shows its largest violations at high mass ratio and large spin magnitude. The asymmetric extension of \texttt{SEOBNRv5PHM} exhibits a smaller, localized violation, while \texttt{NRSur7dq4Remnant} shows larger residuals in the recoil than in the final mass and spin. We trace these violations to an observer-dependent phase anchor in the \texttt{IMRPhenom} antisymmetric mode, non-invariant parameterization of the \texttt{NRSur7dq4} surrogate fits, and one non-invariant NR-calibrated coefficient in the asymmetric \texttt{SEOBNRv5PHM} extension. Local corrections restore waveform parity to numerical precision for the \texttt{IMRPhenom} and \texttt{SEOBNRv5PHM} cases; restoring it in \texttt{NRSur7dq4} requires refitting the surrogate. Reanalyses of eight GWTC-5.0 events show no qualitative change in astrophysical interpretation, although the \texttt{IMRPhenom} correction yields Jensen-Shannon divergences up to $5\times10^{-2}$ in individual marginalized posteriors. Exact symmetries thus provide inexpensive, model-independent consistency tests and should be imposed by construction in calibrated waveform models.

gr-qc↗

arXiv2026

Remnant recoil and host environments of GWTC-4.0 binary black-hole mergers

Determining the astrophysical origin of binary black holes and whether merger remnants are retained in their birth environments is essential for understanding hierarchical mergers and the growth of intermediate-mass black holes. We identified gravitational-wave events most consistent with dense-cluster origin and assessed whether their merger remnants are retained in globular clusters, nuclear star clusters, or galactic potentials. We considered 84 events consistent with binary-black-hole mergers from the first part of the fourth observing run (O4a) of the LIGO-Virgo-KAGRA detector network, and 3 selected events from the second part (O4b). We compared parameter-estimation posteriors with synthetic population models for field and cluster binaries using Bayes factors, accounting for the relative abundances of these formation channels. We computed recoil-velocity posteriors for all events using the IMRPhenomXPNR waveform model. We identified five events whose intrinsic parameters show preference for the adopted dense-cluster models over the considered field-binary populations, including the most massive O4a event GW231123_135430, while finding no robust preference for a dense-cluster origin for the high-spinning O4b event GW241011_233834. Typical recoil velocities are a few hundred km/s, with extended high-velocity tails. These kicks suggest merger remnants are likely ejected from typical globular clusters, while retention in nuclear star clusters remains possible but not guaranteed. Within the adopted models, efficient hierarchical growth may be challenging in typical globular clusters, whereas nuclear star clusters remain viable environments for repeated mergers. Although results depend on the adopted population models, this analysis highlights the importance of improved population models and higher-quality detections enabled by future GW detectors.

astro-ph.HE↗

arXiv2026

A stepping stone toward detecting gravitational wave memory: a cumulative analysis with the full $(\ell=2, m=0)$ spherical harmonic using events from GWTC-4.0 and GWTC-5.0

We perform Bayesian model selection to test for the presence of the $(\ell=2,m=0)$ spherical harmonic mode in gravitational wave events that have previously been identified as binary black hole mergers. As our signal model we use the quasi-circular, non-precessing IMRPhenomTHM_20 waveform model, which includes the oscillatory and displacement memory contributions. Including the oscillatory component of the (2,0) mode increases the signal-to-noise ratio and evidence for this mode, compared to testing only for the presence of gravitational wave memory. Our analysis thus constitutes a natural stepping stone toward detecting gravitational wave memory. We perform our analysis for the binary black hole signals identified in the GWTC-4.0 catalog, and for selected GWTC-5.0 events. In our Bayesian model comparison we find a cumulative $\log_{10}\mathcal{B}=1.38\pm0.79$ in favor of the presence of the (2,0) mode for the GWTC-4.0 catalog. We also stack the signal-to-noise ratio of the full (2,0) mode and of its individual contributions, obtaining results consistent with previous studies and reaching $\mathrm{SNR}_{\mathrm{memory}} = 0.89^{+0.29}_{-0.11}$ after approximately 7.5 months of O4a observations. In addition, we study the precessing candidate GW241127_061008, and find no additional evidence for the (2,0) mode when precession is included in IMRPhenomTPHM_20. Overall, our results provide an assessment of the observational support for the (2,0) mode in current gravitational wave data and allow us to discuss prospects for its future detection. We find that decisive statistical evidence will likely require a larger catalog, with an optimistic estimated number of events of $N_{\mathrm{events}} = 166^{+82}_{-55}$, based on the specific assumptions adopted in this work. We also expect that decisive evidence will require a more extensive waveform systematics study.

gr-qc↗

arXiv2025

Hybrid waveforms for precessing quasi-circular binary systems

The demand for long and accurate gravitational waveforms is increasing as we prepare for the next generation of detectors and seek to improve current waveform models. However, numerical relativity waveforms, while highly accurate, are often too short for these applications due to their high computational cost. Hybrid waveforms, which stitch together gravitational wave signals from different modeling approaches, provide a way to generate complete inspiral-merger-ringdown signals. While hybridization is well-established for aligned-spin systems, precession introduces additional complexities due to gauge ambiguities, frame dependence, or spin dynamics. Here we study the challenges associated with alignment of precessing waveforms and present a systematic approach for constructing hybrid waveforms of precessing quasi-circular systems. Our approach relies on minimal assumptions about the merger waveforms and employs the quadrupole-aligned frame to mitigate mode-mixing. Our method is designed to be robust and broadly applicable, imposing minimal constraints on the input waveforms. This framework expands the applicability of hybridization techniques, facilitating flexible hybrid construction for parameter estimation, model calibration, and gravitational-wave data analysis.

gr-qc↗

arXiv2024

Building a bridge between comparable and extreme mass ratio black hole binaries: a single spin precessing model for the final state

Modelling the gravitational wave signal from binaries beyond comparable mass is an important open issue in gravitational wave astronomy. For non-spinning binaries and when the spins are aligned with the orbital angular momentum, some first studies concerning the transition between the comparable and extreme mass ratio regime are already available, which suggest that extreme mass ratio results at times extrapolate to comparable mass ratios with surprising precision. Here we study the case of misaligned spins: We present new NR simulations performed with the Einstein Toolkit code at mass ratios up to 18 and construct a heterogeneous dataset that spans all mass ratios, including data from NR simulations, numerical approximations to extreme mass ratio binaries, and data from the geodesic approximation. As a first application we provide fits for the remnant mass and spin magnitude in single spin precessing systems, omitting consideration of the in-plane spin orientation. These fits demonstrate accuracy comparable to the state-of-the-art NRSur7dq4EmriRemnant model, all while retaining the simplicity and efficiency inherent in previous phenomenological fits.

gr-qc↗