arXiv subjects

Ethan Payne

Publications and source records attributed to Ethan Payne.

At least 19 recordsLinked to original sources

arXiv2025

Photon counting readout for detection and inference of gravitational waves from neutron star merger remnants

Gravitational waves emitted after neutron star binary coalescences and the information they carry about dense matter are a high-priority target for next-generation detectors. Even though such detectors are expected to observe millions of signals, detectable postmerger emission will remain rare. In this work, we explore postmerger detectability and inference through an alternative detector readout scheme for data dominated by quantum-noise, which is the case above $1$\,kHz: photon-counting. In such a readout, signals and noise become quantized into discrete distributions corresponding to the detection of single photons measured in a chosen basis of modes. Through simulated data, we demonstrate that photon counting can be efficient even for weak signals. We find ${\sim}1$ in 100 signals with a postmerger signal-to-noise ratio of 0.2 can result in a single photon and thus be detected. Furthermore, after $2\times10^4$ signals -- equivalent to $10^{-2}$ to $1.5$ years of observation -- photon counting results in a twofold improvement in the measurement of the radius of a $1.6\,M_\odot$ neutron star. Constraints can be further tightened if the detector classical noise is reduced. Photon counting offers a promising alternative to traditional homodyne readout techniques for extracting information from low signal-to-noise ratio postmerger signals.

gr-qc↗

arXiv2025

Trends in the Population of Binary Black Holes Following the Fourth Gravitational-Wave Transient Catalog: a Data-Driven Analysis

Current population models of binary black hole distributions are difficult to interpret because standard population inferences hinge on modeling choices, which can mask or mimic real structure. The maximum population likelihood ``$\pistroke$ formalism'' provides a means to investigate and interpret features in the distribution of binary black holes using only data -- without specifying a population model. It tells us if features inferred from current population models are truly present in the data or if they arise from model misspecification. It also provides guidance for developing new models by highlighting previously unnoticed features. In this study, we utilize the $\pistroke$ formalism to examine the binary black hole population in the LIGO--Virgo--KAGRA (LVK) fourth Gravitational-Wave Transient Catalog (GWTC-4). Our analysis supports the existence of a gap around $45\,M_\odot$ in the secondary black hole mass distribution and identifies a widening in the distribution of the effective inspiral spin parameter $\chi_\text{eff}$ near this mass as recently reported by Tong et al. (2025). Similar to earlier studies, we find support for an anti-correlation between $\chi_\text{eff}$ and mass ratio. However, we argue that this may be a spurious correlation arising from misspecification of the joint distribution of black hole masses. Furthermore, we identify support for dimensionless black hole spin magnitudes at approximately $\chi \approx 0.2$ and $\chi\approx0.7$. The data support the existence of a correlation between the spin magnitudes $\chi_1$ and $\chi_2$, though subsequent study is required to determine if this feature is statistically significant. The accompanying data release includes $\pistroke$ samples, which can be used to compare theoretical predictions to LVK data and to assess assumptions in parameterised models.

astro-ph.HE↗

arXiv2025

Bayesian frequency estimation at the fundamental quantum limit

Searching for a weak signal at an unknown frequency is a canonical task in experiments probing fundamental physics such as gravitational-wave observatories and ultra-light dark matter haloscopes. These state-of-the-art sensors are limited by quantum noise arising from the fundamental uncertainty about the state of the device. Classically, frequency estimation suffers from a threshold effect in the signal-to-noise ratio such that weak signals are extremely hard to localise in frequency. We show that this phenomenon persists at the fundamental quantum limit but that the classical approach, a quadrature measurement, can nevertheless be beaten by a coherent protocol of projecting onto the "quantum whitened" possible quantum states. Quantum whitening is a covariant measurement, and we examine it analytically in the wide-prior limit and numerically for finite-width priors. Beyond accelerating searches for unknown frequencies, quantum whitening may be used generally to sense the parameter of a unitary encoding given no prior information about the parameter.

quant-ph↗

arXiv2024

The curvature dependence of gravitational-wave tests of General Relativity

High-energy extensions to General Relativity modify the Einstein-Hilbert action with higher-order curvature corrections and theory-specific coupling constants. The order of these corrections imprints a universal curvature dependence on observations while the coupling constant controls the deviation strength. In this Letter, we leverage the theory-independent expectation that modifications to the action of a given order in spacetime curvature (Riemann tensor and contractions) lead to observational deviations that scale with the system length-scale to a corresponding power. Focusing on gravitational wave observations, the relevant scale is the binary total mass, and deviations scale as a power of mass $p$ related to the action order. For example, $p=4,6$ arise in effective field theory for cubic and quartic theories respectively. We incorporate this universal scaling into theory-agnostic tests of General Relativity with current gravitational-wave observations, thus enabling constraints on the curvature scaling without compromising the agnostic nature of these tests. This introduces a flexible yet highly interpretable new paradigm for tests of General Relativity with gravitational-wave catalogs.

gr-qc↗

arXiv2024

Are all models wrong? Falsifying binary formation models in gravitational-wave astronomy

As the catalogue of gravitational-wave transients grows, several entries appear "exceptional" within the population. Tipping the scales with a total mass of $\approx 150 M_\odot$, GW190521 likely contained black holes in the pair-instability mass gap. The event GW190814, meanwhile, is unusual for its extreme mass ratio and the mass of its secondary component. A growing model-building industry has emerged to provide explanations for such exceptional events, and Bayesian model selection is frequently used to determine the most informative model. However, Bayesian methods can only take us so far. They provide no answer to the question: does our model provide an adequate explanation for the data? If none of the models we are testing provide an adequate explanation, then it is not enough to simply rank our existing models - we need new ones. In this paper, we introduce a method to answer this question with a frequentist $p$-value. We apply the method to different models that have been suggested to explain GW190521: hierarchical mergers in active galactic nuclei and globular clusters. We show that some (but not all) of these models provide adequate explanations for exceptionally massive events like GW190521.

astro-ph.HE↗

arXiv2024

Spin Doctors: How to diagnose a hierarchical merger origin

Gravitational-wave observations provide the unique opportunity of studying black hole formation channels and histories -- but only if we can identify their origin. One such formation mechanism is the dynamical synthesis of black hole binaries in dense stellar systems. Given the expected isotropic distribution of component spins of binary black hole in gas-free dynamical environments, the presence of anti-aligned or in-plane spins with respect to the orbital angular momentum is considered a tell-tale sign of a merger's dynamical origin. Even in the scenario where birth spins of black holes are low, hierarchical mergers attain large component spins due to the orbital angular momentum of the prior merger. However, measuring such spin configurations is difficult. Here, we quantify the efficacy of the spin parameters encoding aligned-spin ($χ_{\rm eff}$) and in-plane spin ($χ_{\rm p}$) at classifying such hierarchical systems. Using Monte Carlo cluster simulations to generate a realistic distribution of hierarchical merger parameters from globular clusters, we can infer mergers' $χ_{\rm eff}$ and $χ_{rm p}$. The cluster populations are simulated using Advanced LIGO-Virgo sensitivity during the detector network's third observing period and projections for design sensitivity. Using a "likelihood-ratio"-based statistic, we find that $\sim2\%$ of the recovered population by the current gravitational-wave detector network has a statistically significant $χ_{\rm p}$ measurement, whereas no $χ_{\rm eff}$ measurement was capable of confidently determining a system to be anti-aligned with the orbital angular momentum at current detector sensitivities. These results indicate that measuring spin-precession through $χ_{\rm p}$ is a more detectable signature of a hierarchical mergers and dynamical formation than anti-aligned spins.

gr-qc↗

arXiv2024

Possible Causes of False General Relativity Violations in Gravitational Wave Observations

General relativity (GR) has proven to be a highly successful theory of gravity since its inception. The theory has thrivingly passed numerous experimental tests, predominantly in weak gravity, low relative speeds, and linear regimes, but also in the strong-field and very low-speed regimes with binary pulsars. Observable gravitational waves (GWs) originate from regions of spacetime where gravity is extremely strong, making them a unique tool for testing GR, in previously inaccessible regions of large curvature, relativistic speeds, and strong gravity. Since their first detection, GWs have been extensively used to test GR, but no deviations have been found so far. Given GR's tremendous success in explaining current astronomical observations and laboratory experiments, accepting any deviation from it requires a very high level of statistical confidence and consistency of the deviation across GW sources. In this paper, we compile a comprehensive list of potential causes that can lead to a false identification of a GR violation in standard tests of GR on data from current and future ground-based GW detectors. These causes include detector noise, signal overlaps, gaps in the data, detector calibration, source model inaccuracy, missing physics in the source and in the underlying environment model, source misidentification, and mismodeling of the astrophysical population. We also provide a rough estimate of when each of these causes will become important for tests of GR for different detector sensitivities. We argue that each of these causes should be thoroughly investigated, quantified, and ruled out before claiming a GR violation in GW observations.

gr-qc↗

arXiv2024

Visualizing the Number of Existing and Future Gravitational-Wave Detections from Merging Double Compact Objects

How many gravitational-wave observations from double compact object mergers have we seen to date? This seemingly simple question surprisingly yields a somewhat ambiguous answer that depends on the chosen data-analysis pipeline, detection threshold and other underlying assumptions. To illustrate this we provide visualizations of the number of existing detections from double compact object mergers by the end of the third observing run (O3) based on recent results from the literature. Additionally, we visualize the expected number of observations from future-generation detectors, highlighting the possibility of up to millions of detections per year by the time next-generation ground-based detectors like Cosmic Explorer and Einstein Telescope come online. We present a publicly available code that highlights the exponential growth in gravitational-wave observations in the coming decades and the exciting prospects of gravitational-wave (astro)physics.

astro-ph.HE↗

arXiv2024

Transdimensional inference for gravitational-wave astronomy with Bilby

It has become increasingly useful to answer questions in gravitational-wave astronomy using transdimensional models where the number of free parameters can be varied depending on the complexity required to fit the data. Given the growing interest in transdimensional inference, we introduce a new package for the Bayesian inference Library (Bilby) called tBilby. The tBilby package allows users to set up transdimensional inference calculations using the existing Bilby architecture with off-the-shelf nested samplers and/or Markov Chain Monte Carlo algorithms. Transdimensional models are particularly helpful when we seek to test theoretically uncertain predictions described by phenomenological models. For example, bursts of gravitational waves can be modelled using a superposition of N wavelets where N is itself a free parameter. Short pulses are modelled with small values of N whereas longer, more complicated signals are represented with a large number of wavelets stitched together. Other transdimensional models have found use describing instrumental noise and the population properties of gravitational-wave sources. We provide a few demonstrations of tBilby, including fitting the gravitational-wave signal GW150914 with a superposition of N sine-Gaussian wavelets. We outline our plans to further develop the tbilby code suite for a broader range of transdimensional problems.

gr-qc↗

arXiv2024

The impact of selection biases on tests of general relativity with gravitational-wave inspirals

Tests of general relativity with gravitational wave observations from merging compact binaries continue to confirm Einstein's theory of gravity with increasing precision. However, these tests have so far only been applied to signals that were first confidently detected by matched-filter searches assuming general relativity templates. This raises the question of selection biases: what is the largest deviation from general relativity that current searches can detect, and are current constraints on such deviations necessarily narrow because they are based on signals that were detected by templated searches in the first place? In this paper, we estimate the impact of selection effects for tests of the inspiral phase evolution of compact binary signals with a simplified version of the GstLAL search pipeline. We find that selection biases affect the search for very large values of the deviation parameters, much larger than the constraints implied by the detected signals. Therefore, combined population constraints from confidently detected events are mostly unaffected by selection biases, with the largest effect being a broadening at the $\sim10$ % level for the $-1$PN term. These findings suggest that current population constraints on the inspiral phase are robust without factoring in selection biases. Our study does not rule out a disjoint, undetectable binary population with large deviations from general relativity, or stronger selection effects in other tests or search procedures.

gr-qc↗

arXiv2023

Fortifying gravitational-wave tests of general relativity against astrophysical assumptions

Most tests of general relativity with gravitational-wave observations rely on inferring the degree to which a signal deviates from general relativity in conjunction with the astrophysical parameters of its source, such as the component masses and spins of a compact binary. Due to features of the signal, measurements of these deviations are often highly correlated with the properties of astrophysical sources. As a consequence, prior assumptions about astrophysical parameters will generally affect the inferred magnitude of the deviations. Incorporating information about the underlying astrophysical population is necessary to avoid biases in the inference of deviations from general relativity. Current tests assume that the astrophysical population follows an unrealistic fiducial prior chosen to ease sampling of the posterior -- for example, a prior flat in component masses -- which is is inconsistent with both astrophysical expectations and the distribution inferred from observations. We propose a framework for fortifying tests of general relativity by simultaneously inferring the astrophysical population using a catalog of detections. Although this method applies broadly, we demonstrate it concretely on massive graviton constraints and parameterized tests of deviations to the post-Newtonian phase coefficients. Using observations from LIGO-Virgo-KAGRA's third observing run, we show that concurrent inference of the astrophysical distribution strengthens constraints and improves overall consistency with general relativity. We provide updated constraints on deviations from the theory, finding that, upon modeling the astrophysical population, the 90\%-credible upper limit on the mass of the graviton improves by $25\%$ to $m_g \leq 9.6 \times 10^{-24}\, \mathrm{eV}/c^2$ and the inferred population-level post-Newtonian deviations move ${\sim} 0.4 σ$ closer to zero.

gr-qc↗

arXiv2023

General-relativistic precession in a black-hole binary

The general-relativistic phenomenon of spin-induced orbital precession has not yet been observed in strong-field gravity. Gravitational-wave observations of binary black holes (BBHs) are prime candidates, since we expect the astrophysical binary population to contain precessing binaries. Imprints of precession have been investigated in several signals, but no definitive identification of orbital precession has been reported in any one of the 84 BBH observations to date by the Advanced LIGO and Virgo detectors. Here we report the measurement of strong-field precession in the LIGO-Virgo-Kagra (LVK) gravitational-wave signal GW200129. The binary's orbit precesses at a rate ten orders of magnitude faster than previous weak-field measurements from binary pulsars. We also find that the primary black hole is likely highly spinning. According to current binary population estimates a GW200129-like signal is extremely unlikely, and therefore presents a direct challenge to many current binary formation models.

gr-qc↗

arXiv2023

Model exploration in gravitational-wave astronomy with the maximum population likelihood

Hierarchical Bayesian inference is an essential tool for studying the population properties of compact binaries with gravitational waves. The basic premise is to infer the unknown prior distribution of binary black hole and/or neutron star parameters such component masses, spin vectors, and redshift. These distributions shed light on the fate of massive stars, how and where binaries are assembled, and the evolution of the Universe over cosmic time. Hierarchical analyses model the binary black hole population using a prior distribution conditioned on hyper-parameters, which are inferred from the data. However, a misspecified model can lead to faulty astrophysical inferences. In this paper we answer the question: given some data, which prior distribution--from the set of all possible prior distributions--produces the largest possible population likelihood? This distribution (which is not a true prior) is $\pistroke$ (pronounced "pi stroke"), and the associated \textit{maximum population likelihood} is $\Lstroke$ (pronounced "L stroke"). The structure of $\pistroke$ is a linear superposition of delta functions, a result which follows from Carath{é}odory's theorem. We show how $\pistroke$ and $\Lstroke$ can be used for model exploration/criticism. We apply this $\Lstroke$ formalism to study the population of binary black hole mergers observed in LIGO--Virgo--KAGRA's third Gravitational-Wave Transient Catalog. Based on our results, we discuss possible improvements for gravitational-wave population models.

astro-ph.IM↗

arXiv2022

The curious case of GW200129: interplay between spin-precession inference and data-quality issues

Measurement of spin-precession in black hole binary mergers observed with gravitational waves is an exciting milestone as it relates to both general relativistic dynamics and astrophysical binary formation scenarios. In this study, we revisit the evidence for spin-precession in GW200129 and localize its origin to data in LIGO Livingston in the 20--50\,Hz frequency range where the signal amplitude is lower than expected from a non-precessing binary given all the other data. These data are subject to known data quality issues as a glitch was subtracted from the detector's strain data. The lack of evidence for spin-precession in LIGO Hanford leads to a noticeable inconsistency between the inferred binary mass ratio and precessing spin in the two LIGO detectors, something not expected from solely different Gaussian noise realizations. We revisit the LIGO Livingston glitch mitigation and show that the difference between a spin-precessing and a non-precessing interpretation for GW200129 is smaller than the statistical and systematic uncertainty of the glitch subtraction, finding that the support for spin-precession depends sensitively on the glitch modeling. We also investigate the signal-to-noise ratio $\sim7$ trigger in the less sensitive Virgo detector. Though not influencing the spin-precession studies, the Virgo trigger is grossly inconsistent with the ones in LIGO Hanford and LIGO Livingston as it points to a much heavier system. We interpret the Virgo data in the context of further data quality issues. While our results do not disprove the presence of spin-precession in GW200129, we argue that any such inference is contingent upon the statistical and systematic uncertainty of the glitch mitigation. Our study highlights the role of data quality investigations when inferring subtle effects such as spin-precession for short signals such as the ones produced by high-mass systems.

gr-qc↗

arXiv2022

Angular emission patterns of remnant black holes

The gravitational radiation from the ringdown of a binary black hole merger is described by the solution of the Teukolsky equation, which predicts both the temporal dependence and the angular distribution of the emission. Many studies have explored the temporal feature of the ringdown wave through black hole spectroscopy. In this work, we further study the spatial distribution, by introducing a global fitting procedure over both temporal and spatial dependences, to propose a more complete test of General Relativity. We show that spin-weighted spheroidal harmonics are the better representation of the ringdown angular emission patterns compared to spin-weighted spherical harmonics. The differences are distinguishable in numerical relativity waveforms. We also study the correlation between progenitor binary properties and the excitation of quasinormal modes, including higher-order angular modes, overtones, prograde and retrograde modes. Specifically, we show that the excitation of retrograde modes is dominant when the remnant spin is anti-aligned with the binary orbital angular momentum. This study seeks to provide an analytical strategy and inspire the future development of ringdown test using real gravitational wave events.

gr-qc↗

arXiv2021

The imprint of superradiance on hierarchical black hole mergers

Ultralight bosons are a proposed solution to outstanding problems in cosmology and particle physics: they provide a dark-matter candidate while potentially explaining the strong charge-parity problem. If they exist, ultralight bosons can interact with black holes through the superradiant instability. In this work we explore the consequences of this instability on the evolution of hierarchical black holes within dense stellar clusters. By reducing the spin of individual black holes, superradiance reduce the recoil velocity of merging binary black holes, which, in turn, increases the retention fraction of hierarchical merger remnants. We show that the existence of ultralight bosons with mass $ 2\times10^{-14}\lesssim μ/\textrm{eV} \lesssim2\times10^{-13}$ would lead to an increased rate of hierarchical black hole mergers in nuclear star clusters. An ultralight boson in this energy range would result in up to $\approx60\%$ more present-day nuclear star clusters supporting hierarchical growth. The presence of an ultralight boson can also double the rate of intermediate mass black hole mergers to $\approx0.08$\,Gpc$^{-3}$\,yr$^{-1}$ in the local Universe. These results imply that a select range of ultralight boson mass can have far-reaching consequences for the population of black holes in dense stellar environments. Future studies into black hole cluster populations and the spin distribution of hierarchically formed black holes will test this scenario.

gr-qc↗

arXiv2021

Evidence for hierarchical black hole mergers in the second LIGO--Virgo gravitational-wave catalog

We study the population properties of merging binary black holes in the second LIGO--Virgo Gravitational-Wave Transient Catalog assuming they were all formed dynamically in gravitationally bound clusters. Using a phenomenological population model, we infer the mass and spin distribution of first-generation black holes, while self-consistently accounting for hierarchical mergers. Considering a range of cluster masses, we see compelling evidence for hierarchical mergers in clusters with escape velocities $\gtrsim 100~\mathrm{km\,s^{-1}}$. For our most probable cluster mass, we find that the catalog contains at least one second-generation merger with $99\%$ credibility. We find that the hierarchical model is preferred over an alternative model with no hierarchical mergers (Bayes factor $\mathcal{B} > 1400$) and that GW190521 is favored to contain two second-generation black holes with odds $\mathcal{O}>700$, and GW190519, GW190602, GW190620, and GW190706 are mixed-generation binaries with $\mathcal{O} > 10$. However, our results depend strongly on the cluster escape velocity, with more modest evidence for hierarchical mergers when the escape velocity is $\lesssim 100~\mathrm{km\,s^{-1}}$. Assuming that all binary black holes are formed dynamically in globular clusters with escape velocities on the order of tens of $\mathrm{km\,s^{-1}}$, GW190519 and GW190521 are favored to include a second-generation black hole with odds $\mathcal{O}>1$. In this case, we find that $99\%$ of black holes from the inferred total population have masses that are less than $49\,M_{\odot}$, and that this constraint is robust to our choice of prior on the maximum black hole mass.

astro-ph.HE↗

arXiv2021

Characterization of systematic error in Advanced LIGO calibration in the second half of O3

We present the probability distribution of the systematic errors in the most accurate, high-latency version of the reconstructed dimensionless strain $h$, at the Hanford and Livingston LIGO detectors, used for gravitational-wave astrophysical analysis, including parameter estimation, in the last five months of the third observing run (O3B). This work extends the results presented in Sun et. al (2020) [1] for the first six months of the third observing run (O3A). The complex-valued, frequency-dependent, and slowly time-varying systematic error (excursion from unity magnitude and zero phase) in O3B generally remains at a consistent level as in O3A, yet changes of detector configurations in O3B have introduced a non-negligible change in the frequency dependence of the error, leading to larger excursions from unity at some frequencies and/or during some observational periods; in some other periods the excursions are smaller than those in O3A. For O3B, the upper limit on the systematic error and associated uncertainty is 11.29% in magnitude and 9.18 deg in phase (68% confidence interval) in the most sensitive frequency band 20-2000 Hz. The systematic error alone is estimated at levels of < 2% in magnitude and $\lesssim 4$ deg in phase. These errors and uncertainties are dominated by the imperfect modeling of the frequency dependence of the detector response functions rather than the uncertainty in the absolute reference, the photon calibrators.

astro-ph.IM↗