arXiv subjects

Maximiliano Isi

Publications and source records attributed to Maximiliano Isi.

At least 19 recordsLinked to original sources

arXiv2026

Constraining Gravitational Wave Memory with Hierarchical Inference

With the multitude of gravitational wave observations that have been made in the past ten years, probing the dynamical and nonlinear nature of strong gravity is becoming more and more feasible. One promising way to test the nonlinear nature of Einstein's theory of general relativity (GR) is through the gravitational wave null memory effect: a nonlinear prediction of GR which corresponds to initially comoving observers being permanently displaced due to a burst of gravitational radiation. Previous studies have shown that, while it is unlikely that the memory effect will be observed in a single event by the LIGO-Virgo-KAGRA (LVK) detectors, evidence for memory in the population of LVK events should be attainable after $\sim$2,000 gravitational wave detections. These works, however, largely relied on Bayes factors to perform their memory analyses: an approach that can depend sensitively on the analysis priors and, when naively multiplied across many events, can even favor incorrect conclusions. In this work, using the GWTC-5.0 catalog of binary black hole observations, we instead perform hierarchical Bayesian inference -- which is not subject to the issues associated with Bayes factors -- to measure the evidence for memory in current LVK observations. We find that we can constrain what we call the memory enhancement factor -- the constant appearing in front of the contribution to the strain from the supermomentum flux -- to $0.26_{-4.08}^{+4.09}$ (with $\pm$ values denoting the 68\% credible interval), consistent with its GR value of 1. We also forecast that $\sim$2,000 detections will be needed to constrain the memory enhancement factor away from zero at the $1\sigma$ level.

gr-qc↗

arXiv2026

Evidence for mass-dependent spin subpopulations in GWTC-4

While the origin of merging black-hole binaries observed in gravitational waves remain uncertain, different formation channels are expected to leave distinct imprints on their observed mass and spin distributions. In this work, we focus on the mass dependence of the spin magnitudes $(\chi_1,\chi_2)$, allowing for multiple spin subpopulations whose relative fraction varies with mass. Using the binaries from the fourth LIGO--Virgo--KAGRA gravitational wave transient catalog (GWTC-4), we find strong evidence for two subpopulations, with a log Bayes factor of $\log_{10} \mathcal B = 4^{+6}_{-2}$. The data support a picture in which low-mass systems are composed almost entirely of slowly spinning black holes ($\chi \lesssim 0.2$), while high-mass systems are dominated by a broader component with moderate to rapid spins, peaking at $(\chi_1,\chi_2)\approx(0.7,0.7)$ and retaining a non-negligible tail toward asymmetric spins $(\chi_1,\chi_2)\approx(0.7,0)$. The transition between these regimes spans a broad range from $m_1 \approx 35^{+20}_{-20} \,M_\odot$ to $m_1 \approx 70^{+90}_{-25}\,M_\odot$. For the low-mass, slowly-spinning regime, a flexible model of spin orientations does not allow us to exclude identically vanishing spins, $\chi_1 = \chi_2 = 0$. Meanwhile, the high-mass, rapidly-spinning population does not neatly display the spin-magnitude asymmetry expected from hierarchical mergers, although the data do not exclude that. This kind of localized structure is generally difficult to access with standard Monte-Carlo likelihood estimators, which we replace with a regularized representation in terms of truncated Gaussian mixtures. Taken together, our results provide a new target for formation models, which should reproduce not only the mass and effective spin distributions, but also the mass-dependent structure of the individual component-spin magnitudes.

astro-ph.HE↗

arXiv2026

The impact of waveform systematics and Gaussian noise on the interpretation of GW231123

GW231123 is an exceptional gravitational-wave event consistent with the merger of two massive, highly-spinning black holes. Reliable inference of the source properties is crucial for accurate interpretation of its astrophysical implications. However, characterization of GW231123 is challenging: only few signal cycles are observed and different signal models result in systematically different parameters. We investigate whether the interpretation of GW231123 is robust against model systematics and Gaussian detector noise. We show that the model systematics observed in GW231123 can be reproduced for a simulated signal based on the numerical-relativity surrogate model NRSur7dq4. Simulating data using the maximum-likelihood NRSur7dq4 waveform for GW231123 and no noise realization, we closely recover the systematics observed for the real signal. We then explore how the headline properties of GW231123 are impacted by Gaussian detector noise. Using the NRSur7dq4 maximum-likelihood waveform and different noise realizations, we consistently find support for large masses, high spin magnitudes (median $\chi_1\geq 0.7$), and high spin precession (median $\chi_\mathrm{p}\geq 0.68$). The spin in the direction of the angular momentum ($\chi_\mathrm{eff}$) fluctuates more. Finally, again comparing to simulated signals, we show that any differences in the GW231123 inference based on each separate detector are not statistically significant. These results show that the properties of GW231123, and most importantly the high mass and high spin magnitudes inferred by NRSur7dq4, are robust.

gr-qc↗

arXiv2025

GW231123 ringdown: interpretation as multimodal Kerr signal

GW231123 is a short-duration, low-frequency gravitational wave signal consistent with a binary black hole coalescence and dominated by the merger-ringdown regime due to the high mass of the source. We demonstrate that fits of this ringdown signal using two quasinormal modes are statistically preferred over single-mode fits, for a broad range of fit start times. We also find that two-mode fits give remnant mass and spin measurements consistent with those of the inspiral-merger-ringdown model NRSur7dq4, whereas one-mode fits struggle to do so. Agreement of our fits with those of NRSur7dq4 is achieved by labeling the two quasinormal modes as the ${(\ell,m)=(2,2)}$ and ${(2,0)}$ Kerr prograde fundamental modes. However, we find some indications that fits with the ${(2,1)}$ quasinormal mode instead of the ${(2,0)}$ mode may describe the data better, hinting at possible NRSur7dq4 error or other systematics. When fitting at early times near the estimated peak strain, we find that the inclusion of a third mode, an ${(\ell,m,n)=(2,2,1)}$ prograde overtone, improves consistency with fits at later times. Finally, we perform a test of general relativity by searching for deviations from the Kerr frequency spectrum. Setting issues of systematics aside, we validate the Kerr frequency and damping rate spectrum to within $\pm10\%$ at the 90$\%$ credible level using a fundamental mode fit, and we also report $\pm8\%$ constraints using a model with fundamental modes and an overtone fit at times near the peak strain. Understanding the systematic errors that may be affecting the most accurate analyses of GW231123 is crucial in the context of population and binary formation studies -- our ${(2,1)}$ mode fits return a significantly higher remnant mass and spin than all available inspiral-merger-ringdown models including NRSur7dq4, and this difference in parameter estimates may have astrophysical implications.

gr-qc↗

arXiv2025

Living on the edge: Testing for compact population features at the edges of parameter space

Many astrophysical population studies involve parameters that exist on a bounded domain, such as the dimensionless spins of black holes or the eccentricities of planetary orbits, both of which are confined to $[0, 1]$. In such scenarios, we often wish to test for distributions clustered near a boundary, e.g., vanishing spin or orbital eccentricity. Conventional approaches -- whether based on Monte Carlo, kernel density estimators, or machine-learning techniques -- often suffer biases at the boundaries. These biases stem from sparse sampling near the edge, kernel-related smoothing, or artifacts introduced by domain transformations. We introduce a truncated Gaussian mixture model framework that substantially mitigates these issues, enabling accurate inference of narrow, edge-dominated population features. While our method has broad applications to many astronomical domains, we consider gravitational wave catalogs as a concrete example to demonstrate its power. In particular, we maintain agreement with published constraints on the fraction of zero-spin binary black hole systems in the GWTC-3 catalog -- results originally derived at much higher computational cost through dedicated reanalysis of individual events in the catalog. Our method can achieve similarly reliable results with a much lower computational cost. The method is publicly available in the open-source packages gravpop and truncatedgaussianmixtures.

astro-ph.IM↗

arXiv2025

Spinning into the Gap: Direct-Horizon Collapse as the Origin of GW231123 from End-to-End GRMHD Simulations

GW231123, the most massive binary black hole (BH) merger observed to date, involves component BHs with masses inside the pair-instability mass gap and unusually high spins. This challenges standard formation channels such as classical stellar evolution and hierarchical mergers. However, stellar rotation and magnetic fields, which have not been systematically incorporated in prior models, can strongly influence the BH properties. We present the first self-consistent simulations tracking a massive, low-metallicity helium star from helium core burning through collapse, BH formation, and post-BH formation accretion using 3D general-relativistic magnetohydrodynamic (GRMHD) simulations. Starting from a $250\,M_\odot$ helium core, we show that collapse above the pair-instability mass gap, aided by rotation and magnetic fields, drives mass loss through disk winds and jet launching. This enables the formation of highly spinning BHs within the mass gap and reveals a BH spin-mass correlation. Strong magnetic fields extract angular momentum from the BH through magnetically driven outflows, which in turn suppress accretion, resulting in slowly spinning BHs within the mass gap. In contrast, stars with weak fields permit nearly complete collapse and spin-up of the BH to $ a\approx1$. We show that massive low-metallicity stars with moderate magnetic fields naturally produce BHs whose masses and spins match those inferred for GW231123, and are also consistent with those of GW190521. The outflows may impart a BH kick, which can induce spin-orbit misalignment and widen the post-collapse orbit, delaying the merger. The outflows launched during collapse may power short-lived, high-luminosity jets comparable to the most energetic $\gamma$-ray bursts, offering a potential observational signature of such events in the early universe.

astro-ph.HE↗

arXiv2025

Identifying Compact Chirping SMBHBs in LSST using Bayesian Analysis

The Legacy Survey of Space and Time (LSST) is expected to observe up to ${\sim}100$ million quasars in the next decade. In this work, we show that it is possible to use such data to measure the characteristic frequency evolution of a "chirp" induced by gravitational waves, which can serve as robust evidence for the presence of a compact supermassive black-hole binary. Following the LSST specifications, we generate mock lightcurves consisting of (i) a post-Newtonian chirp produced by orbital motion through, e.g., relativistic Doppler boosting, (ii) a damped random walk representing intrinsic quasar variability, and (iii) Gaussian photometric errors, while assuming non-uniform observations with extended gaps over a period of 10 yr. Through a fully-Bayesian analysis, we show that we can simultaneously measure the chirp and noise parameters with little degeneracy between the two. For chirp signals with an amplitude of $A = 0.5$ mag and a range of times to merger ($t_m = 15{-}10^4$ yr), we can typically measure a non-zero amplitude and positive frequency derivative with over $5\sigma$ credibility. For binaries with $t_m = 50$ yr, we achieve $3\sigma$ ($5\sigma$) confidence that the signal is chirping for $A \gtrsim 0.1$ ($A > 0.2$). Our analysis can take as little as 35 s (and typically $<$ 10 min) to run, making it scalable to a large number of lightcurves. This implies that LSST could, on its own, establish the presence of a compact supermassive black-hole binary, and thus discover gravitational wave sources detectable by LISA and by Pulsar Timing Arrays.

astro-ph.HE↗

arXiv2025

Black hole spectroscopy: from theory to experiment

The "ringdown" radiation emitted by oscillating black holes has great scientific potential. By carefully predicting the frequencies and amplitudes of black hole quasinormal modes and comparing them with gravitational-wave data from compact binary mergers we can advance our understanding of the two-body problem in general relativity, verify the predictions of the theory in the regime of strong and dynamical gravitational fields, and search for physics beyond the Standard Model or new gravitational degrees of freedom. We summarize the state of the art in our understanding of black hole quasinormal modes in general relativity and modified gravity, their excitation, and the modeling of ringdown waveforms. We also review the status of LIGO-Virgo-KAGRA ringdown observations, data analysis techniques, and the bright prospects of the field in the era of LISA and next-generation ground-based gravitational-wave detectors.

gr-qc↗

arXiv2025

Measuring spin precession from massive black hole binaries with gravitational waves: insights from time-domain signal morphology

Robustly measuring binary black hole spins via gravitational waves is key to understanding these systems' astrophysical origins, but remains challenging -- especially for high-mass systems, whose signals are short and dominated by the merger. Nonetheless, events like GW190521 show that strong spin precession can indeed be gleaned. In this work, we track how spin precession imprints on simulated high-mass binary black hole signals cycle-by-cycle using time-domain inference. We investigate a suite of signals, all with the same spins and (near-unity) mass ratio -- yielding identical spin evolution -- but different signal-to-noise ratios (SNRs), total masses, and extrinsic angles, all of which affect the observed waveform morphology. We truncate each signal at various times and infer source parameters using only the data before or after each cutoff. The resultant posterior allows us to identify which time segments of each signal inform its spin precession constraints. We find that at a sufficiently high post-peak SNR ($\sim 20$), spin precession can be constrained by the NRSur7dq4 waveform model when just the post-peak data (i.e., ringdown) are visible. Similarly, at a large enough pre-cutoff SNR ($\sim 10$), spin precession can be constrained using only pre-peak data (i.e., inspiral); this occurs for signals with detector-frame total mass $\lesssim 100 M_{\odot}$ at GW190521's full-signal SNR. Finally, we vary the inclination, polarization, and phase angles, finding that their configuration need not be fine-tuned to measure spin precession, even for very high-mass and short signals with two to three observable cycles. We do not find that the same morphological features consistently drive precession constraints: in some signals, precession inference hinges on the relationship between a loud merger and quiet pre-merger cycle, as was the case for GW190521, but this is not generically true.

gr-qc↗

arXiv2024

Hints of spin-magnitude correlations and a rapidly spinning subpopulation of binary black holes

The complex astrophysical processes leading to the formation of binary black holes and their eventual merger are imprinted on the spins of the individual black holes. We revisit the astrophysical distribution of those spins based on gravitational waves from the third gravitational wave transient catalog GWTC-3, (Abbott et al. 2023a), looking for structure in the two-dimensional space defined by the dimensionless spin magnitudes of the heavier ($\chi_1$) and lighter ($\chi_2$) component black holes. We find support for two distinct subpopulations with greater than $95\%$ credibility. The dominant population is made up of black holes with small spins, preferring $\chi_1 \approx 0.2$ for the primary and $\chi_2 \approx 0$ for the secondary; we report signs of an anticorrelation between $\chi_1$ and $\chi_2$, as well as as evidence against a subpopulation of binaries in which both components are nonspinning. The subdominant population consists of systems in which both black holes have relatively high spins and contains $20^{+18}_{-18}\%$ of the binaries. The binaries that are most likely to belong in this subpopulation are massive and slightly more likely to have spin-orientations aligned with the orbital angular momentum--potentially consistent with isolated binary formation channels capable of producing large spins, like chemically homogeneous evolution. This hint of a rapidly spinning subpopulation hinges on GW190517, a binary with large and well-measured spins. Our results, which are enabled by novel hierarchical inference methods, represent a first step towards more descriptive population models for black hole spins, and will be strengthened or refuted by the large number of gravitational wave detections expected in the next several years.

astro-ph.HE↗

arXiv2024

Gravitational-Wave Parameter Estimation in non-Gaussian noise using Score-Based Likelihood Characterization

Gravitational-wave (GW) parameter estimation typically assumes that instrumental noise is Gaussian and stationary. Obvious departures from this idealization are typically handled on a case-by-case basis, e.g., through bespoke procedures to ``clean'' non-Gaussian noise transients (glitches), as was famously the case for the GW170817 neutron-star binary. Although effective, manipulating the data in this way can introduce biases in the inference of key astrophysical properties, like binary precession, and compound in unpredictable ways when combining multiple observations; alternative procedures free of the same biases, like joint inference of noise and signal properties, have so far proved too computationally expensive to execute at scale. Here we take a different approach: rather than explicitly modeling individual non-Gaussianities to then apply the traditional GW likelihood, we seek to learn the true distribution of instrumental noise without presuming Gaussianity and stationarity in the first place. Assuming only noise additivity, we employ score-based diffusion models to learn an empirical noise distribution directly from detector data and then combine it with a deterministic waveform model to provide an unbiased estimate of the likelihood function. We validate the method by performing inference on a subset of GW parameters from 400 mock observations, containing real LIGO noise from either the Livingston or Hanford detectors. We show that the proposed method can recover the true parameters even in the presence of loud glitches, and that the inference is unbiased over a population of signals without applying any cleaning to the data. This work provides a promising avenue for extracting unbiased source properties in future GW observations over the coming decade.

astro-ph.IM↗

arXiv2024

Analyzing black-hole ringdowns II: data conditioning

Time series data from observations of black hole ringdown gravitational waves are often analyzed in the time domain by using damped sinusoid models with acyclic boundary conditions. Data conditioning operations, including downsampling, filtering, and the choice of data segment duration, reduce the computational cost of such analyses and can improve numerical stability. Here we analyze simulated damped sinsuoid signals to illustrate how data conditioning operations, if not carefully applied, can undesirably alter the analysis' posterior distributions. We discuss how currently implemented downsampling and filtering methods, if applied too aggressively, can introduce systematic errors and skew tests of general relativity. These issues arise because current downsampling and filtering methods do not operate identically on the data and model. Alternative downsampling and filtering methods which identically operate on the data and model may be achievable, but we argue that the current operations can still be implemented safely. We also show that our preferred anti-alias filtering technique, which has an instantaneous frequency-domain response at its roll-off frequency, preserves the structure of posterior distributions better than other commonly used filters with transient frequency-domain responses. Lastly, we highlight that exceptionally long data segments may need to be analyzed in cases where thin lines in the noise power spectral density overlap with central signal frequencies. Our findings may be broadly applicable to any analysis of truncated time domain data with acyclic boundary conditions.

gr-qc↗

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

Striking the right tone: toward a self-consistent framework for measuring black hole ringdowns

The ringdown portion of a binary black hole merger consists of a sum of modes, each containing an infinite number of tones that are exponentially damped sinusoids. In principle, these can be measured as gravitational-waves with observatories like LIGO/Virgo/KAGRA, however in practice it is unclear how many tones can be meaningfully resolved. We investigate the consistency and resolvability of the overtones of the quadrupolar $\ell = m = 2$ mode by starting at late times when the gravitational waveform is expected to be well-approximated by the $\ell m n = 220$ tone alone. We present a Bayesian inference framework to measure the tones in numerical relativity data. We measure tones at different start times, checking for consistency: we classify a tone as stably recovered if and only if the 95\% credible intervals for amplitude and phase at time $t$ overlap with the credible intervals at all subsequent times. We test a set of tones including the first four overtones of the fundamental mode and the 320 tone and find that the 220 and 221 tones can be measured consistently with the inclusion of additional overtones. The 222 tone measurements can be stabilised when we include the 223 tone, but only in a narrow time window, after which it is too weak to measure. The 223 tone recovery appears to be unstable, and does not become stable with the introduction of the 224 tone. We find that $N=3$ tones can be stably recovered simultaneously. However, when analysing $N \geq 4$ tones, the amplitude of one tone is consistent with zero. Thus, within our framework, one can identify only $N=3$ tones with non-zero amplitude that are simultaneously stable.

gr-qc↗

arXiv2024

Multidimensional hierarchical tests of general relativity with gravitational waves

Tests of general relativity with gravitational waves typically introduce parameters for putative deviations and combine information from multiple events by characterizing the population distribution of these parameters through a hierarchical model. Although many tests include multiple such parameters, hierarchical tests have so far been unable to accommodate this multidimensionality, instead restricting to separate one-dimensional analyses and discarding information about parameter correlations. In this paper, we extend population tests of general relativity to handle an arbitrary number of dimensions. We demonstrate this framework on the two-dimensional inspiral-merger-ringdown consistency test, and derive new constraints from the latest LIGO-Virgo-KAGRA catalog, GWTC-3. We obtain joint constraints for the two parameters introduced by the classic formulation of this test, revealing their correlation structure both at the individual-event and population levels. We additionally propose a new four-dimensional formulation of the inspiral-merger-ringdown test that we show contains further information. As in past work, we find the GW190814 event to be an outlier; the 4D analysis yields further insights on how the low mass and spin of this event biases the population results. Without (with) this event, we find consistency with general relativity at the 60\% (92\%) credible level in the 2D formulation, and 76\% (80\%) for the 4D formulation. This multi-dimensional framework can be immediately applied to other tests of general relativity in any number of dimensions, including the parametrized post-Einsteinian tests and ringdown tests.

gr-qc↗

arXiv2024

Birefringence tests of gravity with multi-messenger binaries

Extensions to General Relativity (GR) allow the polarization of gravitational waves (GW) from astrophysical sources to suffer from amplitude and velocity birefringence, which respectively induce changes in the ellipticity and orientation of the polarization tensor. We introduce a multi-messenger approach to test this polarization behavior of GWs during their cosmological propagation using binary sources, for which the initial polarization is determined by the inclination and orientation angles of the orbital angular momentum vector with respect to the line of sight. In particular, we use spatially-resolved radio imaging of the jet from a binary neutron star (BNS) merger to constrain the orientation angle and hence the emitted polarization orientation of the GW signal at the site of the merger, and compare to that observed on Earth by GW detectors. For GW170817 we constrain the deviation from GR due to amplitude birefringence to $κ_A = -0.12^{+0.60}_{-0.61}$, while the velocity birefringence parameter $κ_V$ remains unconstrained. The inability to constrain $κ_V$ is due to the fact that Virgo did not detect GW170817, and measurements of the polarization orientation require information from a combination of multiple detectors with different alignments. For this reason, we also mock future BNS mergers with resolved afterglow proper motion and project that $κ_V$ could be constrained to a precision of $5\,$rad (corresponding to an angular shift of the GW polarization of $δϕ_V\approx 0.2\,$rad for a BNS at $100\,$Mpc) by a future network of third-generation ground-based GW detectors such as Cosmic Explorer and the radio High Sensitivity Array. Crucially, this velocity birefringence effect cannot be constrained with dark binary mergers as it requires polarization information at the emission time, which can be provided only by electromagnetic emission.

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↗

arXiv2024

GW190521: tracing imprints of spin-precession on the most massive black hole binary

GW190521 is a remarkable gravitational-wave signal on multiple fronts: its source is the most massive black hole binary identified to date and could have spins misaligned with its orbit, leading to spin-induced precession -- an astrophysically consequential property linked to the binary's origin. However, due to its large mass, GW190521 was only observed during its final 3-4 cycles, making precession constraints puzzling and giving rise to alternative interpretations, such as eccentricity. Motivated by these complications, we trace the observational imprints of precession on GW190521 by dissecting the data with a novel time domain technique, allowing us to explore the morphology and interplay of the few observed cycles. We find that precession inference hinges on a quiet portion of the pre-merger data that is suppressed relative to the merger-ringdown. Neither pre-merger nor post-merger data alone are the sole driver of inference, but rather their combination: in the quasi-circular scenario, precession emerges as a mechanism to accommodate the lack of a stronger pre-merger signal in light of the observed post-merger. In terms of source dynamics, the pre-merger suppression arises from a tilting of the binary with respect to the observer. Establishing such a consistent picture between the source dynamics and the observed data is crucial for characterizing the growing number of massive binary observations and bolstering the robustness of ensuing astrophysical claims.

astro-ph.HE↗