The first informative astrophysical calibration of gravitational-wave detectors is reported using GW240925 and GW250207.
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GWTC-2.1: Deep Extended Catalog of Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run
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abstract
The second Gravitational-Wave Transient Catalog reported on 39 compact binary coalescences observed by the Advanced LIGO and Advanced Virgo detectors between 1 April 2019 15:00 UTC and 1 October 2019 15:00 UTC. We present GWTC-2.1, which reports on a deeper list of candidate events observed over the same period. We analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. We employ three matched-filter search pipelines for candidate identification, and estimate the astrophysical probability for each candidate event. While GWTC-2 used a false alarm rate threshold of 2 per year, we include in GWTC-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. We calculate the source properties of a subset of 44 high-significance candidates that have an astrophysical probability greater than 0.5. Of these candidates, 36 have been reported in GWTC-2. If the 8 additional high-significance candidates presented here are astrophysical, the mass range of events that are unambiguously identified as binary black holes (both objects $\geq 3M_\odot$) is increased compared to GWTC-2, with total masses from $\sim 14 M_\odot$ for GW190924_021846 to $\sim 182 M_\odot$ for GW190426_190642. The primary components of two new candidate events (GW190403_051519 and GW190426_190642) fall in the mass gap predicted by pair instability supernova theory. We also expand the population of binaries with significantly asymmetric mass ratios reported in GWTC-2 by an additional two events (the mass ratio is less than $0.65$ and $0.44$ at $90\%$ probability for GW190403_051519 and GW190917_114630 respectively), and find that 2 of the 8 new events have effective inspiral spins $\chi_\mathrm{eff} > 0$ (at $90\%$ credibility), while no binary is consistent with $\chi_\mathrm{eff} < 0$ at the same significance.
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representative citing papers
The first search for scalar-induced gravitational waves via pulsar parameter drifts yields f_PBH < 10^{-10} (95% CL) for PBH masses 0.3 to 4e4 solar masses, strongly disfavoring a primordial black hole origin for LVK binary black holes.
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First joint population inference on binary black hole eccentricity from GWTC-4 bounds the eccentric branching ratio below 5% at 90% confidence, with results consistent with quasi-circular models but highly model-dependent.
BHaHAHA provides the first infrastructure-agnostic open-source apparent horizon finder using a hyperbolic flow method, with reported 64x speedups on difficult cases and 2.1x faster dynamic tracking than AHFinderDirect.
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A cross-correlation search of ~11,000 event pairs in GWTC-4 including sub-threshold candidates finds no lensed GW pairs above 3σ, setting an upper bound of ≤1.5/yr on the lensing rate.
SEOBNRv6EHM is a multipolar EOB model for eccentric planar-orbit BBHs calibrated to NR simulations, showing low waveform mismatches up to eccentricity 0.9.
The gwNRHME framework constructs a multi-modal non-spinning eccentric gravitational waveform surrogate by modulating quasi-circular models with universal eccentric functions, achieving median mismatches of ~9e-5 against 156 NR waveforms.
Presents a practical fully time-domain end-to-end likelihood for gravitational-wave inference with structured linear algebra and GPU acceleration.
A new harmonic-decomposition template search for precessing binary black holes in LIGO O3 data improves sensitivity by up to 28% and reduces computational cost by up to 5x with no new detections.
Derives closed 5D partial-wave Raman scattering amplitude via NS functions and computes non-vanishing dynamical ℓ=0 and static ℓ=1 scalar tidal Love numbers with RG running up to O(G²) for STBH.
Numerical simulations of eccentric Proca-star mergers show that relative phase between the stars controls post-merger fate and can generate odd-mode gravitational waves absent from black-hole mergers.
A universal anomalous dimension for multipole moments in GR is derived via two EFT methods and applied to resum short-distance logarithmic tails in binary gravitational waveforms.
Stable neutron-star configurations denser than black holes exist in quasi-topological gravity and may produce detectable gravitational-wave echoes.
No GWTC-3 event robustly prefers a non-BBH merger morphology once low-frequency cutoffs are raised; apparent low-compactness modes are noise artifacts, with GW231123 left as an unresolved special case.
Mode-by-mode filtering of higher-order modes enables low-latency marginalization over mode information in NSBH gravitational-wave signals, tightening constraints on distance, inclination, and secondary mass.
A saliency-guided wavelet framework extracts transient glitches from gravitational-wave strain data by pre-tagging candidates with UMAP, identifying time-frequency regions on CWT spectrograms, and enabling exact reconstruction via adaptive DWT coefficient masking.
Two LIGO transients are consistent with domain wall signals from a shared scalar field but binary black hole models remain favored, with a morphological degeneracy identified.
SEOBNRv6EHM reduces parameter biases for eccentric binaries versus prior models and shows mild support for eccentricity in five catalog events plus comparable unbound fits for three high-mass events.
Spinning test particles around rotating hairy black holes show finite-time instability in localized regions of the (spin, hair-parameter) plane that reorganize the strong-field phase space compared to Kerr.
Single-event GW parameter estimates under reference priors are population-biased; hierarchical, population-informed re-analysis is needed and changes the identification of the most extreme black holes in the catalog.
A vertical long-wire suspended gradiometer configuration amplifies gravitational wave signals from order h to order h L/D by separating gravitational force from moment of inertia.
citing papers explorer
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GW240925 and GW250207: Astrophysical Calibration of Gravitational-wave Detectors
The first informative astrophysical calibration of gravitational-wave detectors is reported using GW240925 and GW250207.
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Constraints on the Primordial Black Hole Abundance using Pulsar Parameter Drifts
The first search for scalar-induced gravitational waves via pulsar parameter drifts yields f_PBH < 10^{-10} (95% CL) for PBH masses 0.3 to 4e4 solar masses, strongly disfavoring a primordial black hole origin for LVK binary black holes.
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Testing the Kerr hypothesis beyond the quadrupole with GW241011
GW241011 data shows consistency with Kerr black holes for both quadrupole and octupole moments and delivers the first observational bounds on spin-induced octupole deviations.
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Population Properties of Binary Black Holes with Eccentricity
First joint population inference on binary black hole eccentricity from GWTC-4 bounds the eccentric branching ratio below 5% at 90% confidence, with results consistent with quasi-circular models but highly model-dependent.
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BHaHAHA: A Fast, Robust Apparent Horizon Finder Library for Numerical Relativity
BHaHAHA provides the first infrastructure-agnostic open-source apparent horizon finder using a hyperbolic flow method, with reported 64x speedups on difficult cases and 2.1x faster dynamic tracking than AHFinderDirect.
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Joint inference of line-of-sight acceleration and orbital eccentricity in neutron-star--black-hole binaries
All five NSBH events are consistent with zero line-of-sight acceleration; the joint posterior for GW200105_162426 disfavors both zero LOSA and zero eccentricity at 90% credibility.
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Fast gravitational waveform models for quasi-circular coalescences of neutron star--black hole binaries
New frequency-domain models IMRPhenomXHM_NSBH, SEOBNRv5HM_ROM_NRTidalv3_NSBH, and IMRPhenomXPHM_NSBH bring higher-order modes and tidal effects to fast NSBH waveform templates.
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Model-Independent Search Discards Faint Lensed-Pairs of Gravitational Wave Events in the Sub-Threshold Candidates of GWTC-4
A cross-correlation search of ~11,000 event pairs in GWTC-4 including sub-threshold candidates finds no lensed GW pairs above 3σ, setting an upper bound of ≤1.5/yr on the lensing rate.
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Accurate waveforms for generic planar-orbit binary black holes: The multipolar effective-one-body model SEOBNRv6EHM
SEOBNRv6EHM is a multipolar EOB model for eccentric planar-orbit BBHs calibrated to NR simulations, showing low waveform mismatches up to eccentricity 0.9.
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Including higher-order modes in a quadrupolar eccentric numerical relativity surrogate using universal eccentric modulation functions
The gwNRHME framework constructs a multi-modal non-spinning eccentric gravitational waveform surrogate by modulating quasi-circular models with universal eccentric functions, achieving median mismatches of ~9e-5 against 156 NR waveforms.
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Accelerated Time-domain Analysis for Gravitational Wave Astronomy
Presents a practical fully time-domain end-to-end likelihood for gravitational-wave inference with structured linear algebra and GPU acceleration.
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Search for Precessing Binary Black Holes in Advanced LIGO's Third Observing Run using Harmonic Decomposition
A new harmonic-decomposition template search for precessing binary black holes in LIGO O3 data improves sensitivity by up to 28% and reduces computational cost by up to 5x with no new detections.
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5-Dimensional Gravitational Raman Scattering: Scalar Wave Perturbations in Schwarzschild-Tangherlini Spacetime
Derives closed 5D partial-wave Raman scattering amplitude via NS functions and computes non-vanishing dynamical ℓ=0 and static ℓ=1 scalar tidal Love numbers with RG running up to O(G²) for STBH.
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Eccentric mergers of binary Proca stars
Numerical simulations of eccentric Proca-star mergers show that relative phase between the stars controls post-merger fate and can generate odd-mode gravitational waves absent from black-hole mergers.
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Resummation of Universal Tails in Gravitational Waveforms
A universal anomalous dimension for multipole moments in GR is derived via two EFT methods and applied to resum short-distance logarithmic tails in binary gravitational waveforms.
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Neutron stars more compact than black holes as a probe of strong-field gravity
Stable neutron-star configurations denser than black holes exist in quasi-topological gravity and may produce detectable gravitational-wave echoes.
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Compactness Inference in Gravitational-Wave Mergers with PhenomDECO: Catalog Benchmarks and Robustness Diagnostics
No GWTC-3 event robustly prefers a non-BBH merger morphology once low-frequency cutoffs are raised; apparent low-compactness modes are noise artifacts, with GW231123 left as an unresolved special case.
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Improving low-latency multi-messenger follow-up of neutron star-black hole mergers with mode-by-mode filtering
Mode-by-mode filtering of higher-order modes enables low-latency marginalization over mode information in NSBH gravitational-wave signals, tightening constraints on distance, inclination, and secondary mass.
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Wavelet-Based Extraction of Transient Noise in Gravitational-Wave Interferometers using a Saliency-Guided Learning Architecture
A saliency-guided wavelet framework extracts transient glitches from gravitational-wave strain data by pre-tagging candidates with UMAP, identifying time-frequency regions on CWT spectrograms, and enabling exact reconstruction via adaptive DWT coefficient masking.
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Short Gravitational-Wave Transients as Probes of Cosmic Domain Walls
Two LIGO transients are consistent with domain wall signals from a shared scalar field but binary black hole models remain favored, with a morphological degeneracy identified.
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Eccentric and unbound compact binaries in the LIGO-Virgo-KAGRA catalog: parameter estimation and waveform systematics with SEOBNRv6EHM
SEOBNRv6EHM reduces parameter biases for eccentric binaries versus prior models and shows mild support for eccentricity in five catalog events plus comparable unbound fits for three high-mass events.
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Spin-Hair Induced Chaos of Spinning Test Particles in Rotating Hairy Black Holes
Spinning test particles around rotating hairy black holes show finite-time instability in localized regions of the (spin, hair-parameter) plane that reorganize the strong-field phase space compared to Kerr.
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Gravitational-wave astronomy requires population-informed parameter estimation
Single-event GW parameter estimates under reference priors are population-biased; hierarchical, population-informed re-analysis is needed and changes the identification of the most extreme black holes in the catalog.
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Mechanical Long Baseline Differential Gradiometers as Low Frequency Gravitational Wave Detectors
A vertical long-wire suspended gradiometer configuration amplifies gravitational wave signals from order h to order h L/D by separating gravitational force from moment of inertia.
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Second-Generation Mass Peak in the Gravitational-Wave Population as a Probe of Globular Clusters
Dynamical formation in globular clusters produces a robust second black-hole mass peak at ~70 solar masses from second-generation mergers when the first-generation spectrum is truncated by pair-instability supernovae.
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Posterior Predictive Checks for Gravitational-wave Populations: Limitations and Improvements
Maximum-likelihood-based posterior predictive checks detect model misspecification better than event-level versions for uncertain spin tilts, but current detector sensitivity limits their power; the Gaussian Component Spins model underpredicts high spin magnitudes and overpredicts anti-aligned tilts
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Measurement prospects for the pair-instability mass cutoff with gravitational waves
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A new group of low-spin $50-70M_\odot$ Black Holes and the high pair-instability mass cutoff
GWTC-4.0 reveals low-spin black holes up to ~68.5 Msun, implying a higher pair-instability mass cutoff and a lower 12C(alpha,gamma)16O rate.
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Scalar fields around black hole binaries in LIGO-Virgo-KAGRA
Semi-analytic waveform model for scalar environments around black hole binaries is validated against numerical relativity and applied to LIGO-Virgo-KAGRA data to obtain upper limits on scalar densities with tentative evidence in GW190728.
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Black Hole Spectroscopy and Tests of General Relativity with GW250114
GW250114 data confirm the remnant is consistent with a Kerr black hole and bound the dominant quadrupolar mode frequency to within a few percent of the GR prediction, with constraints tighter than prior multi-event catalogs.
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Gravitational wave surrogate model for spinning, intermediate mass ratio binaries based on perturbation theory and numerical relativity
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Evidence for eccentricity in the population of binary black holes observed by LIGO-Virgo-KAGRA
Bayesian inference on LVK O1-O3 events with eccentric aligned-spin waveforms yields log10 Bayes factors of 1.77-4.75 favoring eccentricity for GW200129, GW190701 and GW200208_22, and >99.5% probability that at least one of 57 events is eccentric under an astrophysically motivated rate prior.
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The Chirp-Mass Ladder: A New Rung Emerges
GWTC-5 chirp-mass peaks form a ~1.9-spaced ladder with a new ~19 M⊙ rung matching predicted 2G+3G mergers, unifying prior 1G+2G spin-transition groups under one hierarchical scenario.
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Reference Frames and Gravitational-Wave Polarizations: Symmetry Classification and Preferred-Frame Phenomenology
Derives boost transformations for GW polarizations, proposes symmetry classification without preferred frames, and analyzes preferred-frame effects in Bumblebee gravity including novel polarization conversion.
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High-Stability Deformable Mirrors for Correcting Non-Axisymmetric Residual Aberrations in Thermal Compensation of Future Gravitational Wave Interferometers
Deformable mirrors combined with a modified Gerchberg-Saxton algorithm enable reproducible asymmetric intensity patterns for thermal compensation in high-power gravitational wave interferometers, shown via simulations and experiments.
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Extended parameterized spin expansion formalism for ringdown analysis with GW250114
Simultaneously sampling the EFT scaling index p̃ and length scale ℓ̃ in ParSpec shows p̃ is prior-dominated and the ℓ̃ ~ 83 km bound is mostly prior geometry.
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Population-level correlations in Bayesian statistics: an illustrative model for gravitational-wave astronomy
An idealized Gaussian model demonstrates that single-event correlations inflate uncertainties in population correlations and that catalog-wide correlated biases can be misread as population correlations.
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AGN-driven BBH mergers: Black hole populations and hierarchical growth across the AGN parameter space
Semi-analytical models show AGN disks produce repeated BBH mergers with a high-mass tail beyond the pair-instability gap, more efficiently at low viscosity, with spin and mass-ratio signatures that can match events like GW190521.
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Line-of-sight acceleration in compact binaries with higher harmonics and eccentricity
Implements consistent line-of-sight acceleration corrections in quasi-circular and eccentric GW waveform models, applies them to GWTC-3 events, and reports no substantial evidence for acceleration while warning of bias from inconsistent harmonic treatment.
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How do the LIGO-Virgo-KAGRA's Heavy Black Holes Form? No evidence for core-collapse Intermediate-mass black holes in GWTC-4
No evidence for core-collapse formed low-spin IMBHs in GWTC-4, with 90% upper limit on merger rate of 0.077 Gpc^{-3} yr^{-1}, low-spin BH mass truncation at 65 solar masses consistent with pair-instability gap lower edge, and high-spin IMBHs from hierarchical mergers.
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Ringdown Analysis of GW250114 with Orthonormal Modes
Orthonormal QNM analysis of GW250114 raises the significance of the first overtone of the ℓ=m=2 mode from 82.5% to 99.9% and detects no significant deviation from Kerr predictions.
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Probing Kerr Symmetry Breaking with LISA Extreme-Mass-Ratio Inspirals
LISA EMRIs can constrain deviations from Kerr equatorial symmetry to 10^{-2} and axial symmetry to 10^{-3} using Analytic Kludge waveforms and Fisher analysis.
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Recoil kicks from binary black hole mergers in GWTC catalogs: implications for retention and hierarchical mergers
GWTC BBH mergers have typical recoil kicks of ~300–330 km/s, with retention of only ~2–3% in globular clusters; hierarchical-merger prospects depend on both retention and post-kick re-centering.
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Confronting eikonal and post-Kerr methods with numerical evolution of scalar field perturbations in spacetimes beyond Kerr
Numerical simulations benchmark the eikonal and post-Kerr approximations for quasinormal modes in deformed Kerr spacetimes, quantifying their errors relative to expected observational precision.
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Biased parameter inference of eccentric, spin-precessing binary black holes
Eccentric BBH signals recovered with quasi-circular precessing models show biases in chirp mass and χ_p; Bayes factors favor eccentric aligned-spin models when both eccentricity and precession are present.
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Neural Post-Einsteinian Test of General Relativity with the Third Gravitational-Wave Transient Catalog
Neural post-Einsteinian analysis of GWTC-3 finds no GR violation and sets constraints covering both post-Newtonian and beyond-post-Newtonian deviations in a single theory-agnostic setup.
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Binary black holes in the heat of merger
Develops a frequency-domain approximant for tidal heating in nonspinning black hole binaries that extends to merger and includes horizon parameters.
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Probing globular clusters parameters through gravitational wave lensing with stellar-mass black hole binaries
Simulations of wave-optics lensing of GW150914-like signals by globular clusters recover injected velocity dispersion values for favorable alignments when lens and source parameters are jointly estimated.
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Exploring Gravitational Wave Signatures Due to Primordial Non-gaussianity and Large Scale Structure Using SKAO
Explores SKAO detection of scalar-induced GW backgrounds as probes of primordial non-Gaussianity and parity violation, with LSS cross-correlation to improve SNR.
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Fast targeted gravitational-wave followup search for compact binary mergers using GSTLAL pipeline
A targeted gravitational-wave search modifies the GstLAL likelihood ratio with a sky localization prior from EM triggers, showing improved detection efficiency in injection studies while controlling false alarms.