arXiv subjects

Hai-Tian Wang

Publications and source records attributed to Hai-Tian Wang.

At least 19 recordsLinked to original sources

arXiv2026

A Catalog-Wide Study of Gravitational-Wave Residuals in GWTC-4 and GWTC-5

Improved sensitivity of the LIGO-Virgo-KAGRA detectors has enabled the accumulation of a large gravitational-wave event catalog, providing an opportunity for catalog-wide residual analyses to assess waveform-model performance. We study GWTC-4 and GWTC-5 events with signal-to-noise ratio $>12$ in at least one detector, applying three goodness-of-fit tests to the normalized Q-transform energies of whitened residuals obtained by subtracting the IMRPhenomXPHM and SEOBNRv5PHM waveform models. Across the catalog, the residuals are consistent with Gaussian noise, with no evidence of systematic deviations in either multi-detector events or valid single-detector events. For events exhibiting strong model dependence in parameter estimation, variations between waveform models likewise do not produce persistent residual structures. These results demonstrate that parameter-estimation biases associated with waveform modeling do not necessarily manifest as detectable features in the residuals. Residual analyses therefore provide a complementary diagnostic in data space for validating gravitational-wave waveform models within the detector sensitivity.

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arXiv2026

Bekenstein--Hod Bound: A $3.3σ$ Confirmation from GW250114

Black holes link gravity, thermodynamics and information via limits on the relaxation rate of a perturbed system. The Bekenstein-Hod bound imposes a minimum relaxation time at fixed temperature, but its observational test demands both black hole thermodynamic characterization and decay time measurement. Here we test this bound with GW250114, the loudest gravitational-wave signal yet observed from a binary black-hole merger. We infer the remnant temperature from pre-merger data truncated at least $10\,M$ before the peak and its longest-lived decay time from post-merger data, thereby avoiding direct reuse of the same strain samples. The ringdown frequencies and damping times are allowed to vary independently rather than being fixed to the Kerr spectrum. For the primary $t_{<}=-10\,M$ analysis, the bound is verified at $3.3-3.6σ$ across the focal ringdown start times, representing a substantial improvement over the $91\%$ confidence level set by GW150914. The conclusion remains robust under varied pre-merger cutoffs and explicit inclusion of the short-lived first overtone in waveform modelling. This separated-data measurement converts an information-theoretic relaxation bound into a precision test of a single astrophysical black hole.

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arXiv2026

Ensemble-Based Residual Tests of GW231123 across Waveform Models

GW231123 is an exceptional gravitational wave event for which different waveform models yield significantly different inferred source parameters. Residual tests provide a direct way to assess whether each waveform model gives an adequate description of the observed signal. In this work, we extend the conventional residual-test methods by subtracting the 100 highest likelihood waveforms, rather than only the maximum likelihood waveform for each model, thereby propagating waveform reconstruction uncertainty into the residual analysis. This ensemble-based approach turns the residual test from a single waveform diagnostic into a robustness test over the local high likelihood waveform manifold. We further perform injection tests to quantify the detectability of cross-model waveform discrepancies in realistic detector noise. The large-scale implementation of these analyses is made possible by the high speed and low computational cost of our residual testing framework, which is based on three goodness-of-fit tests: the Kolmogorov-Smirnov test, the Anderson-Darling test, and Pearson's chi-squared test.

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arXiv2026

First Overtone Mode in the Ringdown Signal of GW231028

The properties of a remnant black hole can be probed by analyzing the gravitational waves emitted during its ringdown phase. This signal provides a direct test of general relativity in the strong-field regime. In this study, we apply both a time-domain F-statistic framework and full Bayesian time-domain sampling to the ringdown of GW231028\_153006. We report decisive evidence for multimode content, specifically identifying both the first overtone ($\ell|m|n=221$) and the higher order ($\ell|m|n=210$). The detection of the $221$ mode is statistically significant, achieving a Bayes factor of $\sim 189.2$ and an amplitude exclusion from zero at $>7σ$ credibility for an analysis beginning at $10\,M$ postpeak. These findings are rigorously validated against the numerical relativity injection SXS:BBH:1282, which confirms that such multimode features are physically expected for a remnant with the inferred high spin and mass ratio. The inclusion of the overtone mode allows for precise constraints on the remnant's properties, yielding a redshifted final mass of $246.2^{+22.3}_{-22.4}\,{\rm M}_{\odot}$ and a final spin of $0.81_{-0.10}^{+0.07}$ (at $90\%$ credibility), consistent with full inspiral-merger-ringdown predictions. A test of the no-hair theorem, enabled by this robust multimode detection, shows consistency with general relativity.

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arXiv2026

Gravitational Wave Astronomy With TianQin

The opening of the gravitational wave window has significantly enhanced our capacity to explore the universe's most extreme and dynamic sector. In the mHz frequency range, a diverse range of compact objects, from the most massive black holes at the farthest reaches of the Universe to the lightest white dwarfs in our cosmic backyard, generate a complex and dynamic symphony of gravitational wave signals. Once recorded by gravitational wave detectors, these unique fingerprints have the potential to decipher the birth and growth of cosmic structures over a wide range of scales, from stellar binaries and stellar clusters to galaxies and large-scale structures. The TianQin space-borne gravitational wave mission is scheduled for launch in the 2030s, with an operational lifespan of five years. It will facilitate pivotal insights into the history of our universe. This document presents a concise overview of the detectable sources of TianQin, outlining their characteristics, the challenges they present, and the expected impact of the TianQin observatory on our understanding of them.

astro-ph.GA↗

arXiv2026

Constraints on parity and Lorentz violations from gravitational waves: a comparison between single-parameter and multi-parameter analysis

The growing catalog of gravitational wave (GW) detections by the LIGO-Virgo-KAGRA Collaboration enables increasingly stringent tests of general relativity, particularly regarding possible violations of parity and Lorentz symmetry. Parity and Lorentz violations in gravity can modify both the damping rate and dispersion relation of GWs, leading to birefringence, frequency-dependent damping, and dispersion effects in the propagation of GWs. These effects result in amplitude and phase corrections of the waveforms of GWs produced by the coalescence of compact binaries, which enable us to constrain parity- and Lorentz-violating effects by analyzing GW signals detected by LIGO-Virgo-KAGRA detectors with the distorted waveforms. While most current analyses employ single-parameter methods-varying one deformation parameter at a time-modified gravity theories often predict multiple, coexisting deviations. In this work, we construct several specific multi-parameter GW waveform models incorporating parity- and Lorentz-violating effects and perform full Bayesian parameter estimation to compare multi-parameter and single-parameter constraints. We find that including multiple deformation parameters yields constraints on individual parameters that are generally comparable to those from single-parameter analyses, despite one specific model showing a degeneracy between the deformation parameters. Our results support the robustness of single-parameter tests for parity and Lorentz symmetry of gravity in current and future GW observations.

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arXiv2026

A Robust and Efficient F-statistic-based Framework for Consistent Bayesian Inference of Compact Binary Coalescences

We present a comprehensive investigation of the F-statistic method for parameter estimation of gravitational wave (GW) signals from compact binary coalescences. By analytically maximizing the likelihood over the luminosity distance and polarization angle, this approach reduces the dimensionality of the parameter space to enhance computational efficiency. We also introduce a novel formulation for calculating the Bayesian evidence for the F-statistic, enabling a quantitative assessment of its performance against standard full frequency-domain (FFD) Bayesian inference. Applying these two methods to analyze several representative GW events (GW190412, GW190814, and GW170817), we find that the F-statistic consistently yields results in good agreement with the FFD approach, while offering a significant reduction in computational cost. We demonstrate that including calibration uncertainty generally improves the agreement between the two methods. Furthermore, under the assumption of physical priors, the F-statistic-based analyses consistently yield higher Bayesian evidence than the corresponding FFD analyses. While the F-statistic produces slightly broader constraints on some parameters, we argue this represents a more honest uncertainty quantification, particularly in high-dimensional parameter spaces with complex posterior structures. These results highlight the significant advantages of the F-statistic method for GW data analysis, positioning it as a powerful tool for the era of high-rate detections with future observatories.

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arXiv2026

Cracking Gravitational Wave Multiple Ringdown Modes in Space

Ringdown signals from perturbed black holes (BHs) offer a clean window into BH spacetime, strong-field gravity, and fundamental physics. Presently the quasi-normal modes of stellar-mass BH ringdowns have been successfully extracted in the ground-based gravitational wave (GW) observations. Looking ahead, the future space-borne observatories will listen to the ringdowns from massive BH binary coalescences more loudly and resolve multiple modes to unprecedented precision, which calls for efficient approaches to mitigate the sharply increasing computational burden. We develop a practical ringdown analysis pipeline for space-borne detectors by implementing FIREFLY, a novel acceleration algorithm validated in ground-based detectors, and for the first time demonstrate its compatibility and effectiveness with the time-delay interferometry (TDI) observables. With high fidelity, we achieve a $\sim 200$-fold speedup for a simulated ringdown signal including six modes, providing a viable and scalable route for multi-mode ringdown analysis in the space context. This new approach has sound statistical interpretation and is extensible to other GW sources in band.

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arXiv2025

Verification of the Black Hole Area Law with GW230814

We present an observational confirmation of Hawking's black-hole area theorem using the newly released gravitational-wave data from the GWTC-4.0. We analyze the high signal-to-noise ratio binary black hole (BBH) merger GW230814 and measure the (total) horizon area of the black holes before and after the merger. For preferred (and reasonable) choices of the post-truncation start time, the horizon area of the remnant black hole is found to be greater than the total horizon area of the two pre-merger black holes at a high possibility (at least $\gtrsim 99.5\%$). Importantly, our analysis accounts for sky-location uncertainty. These results provide a stringent observational confirmation of the black-hole area law, further bolstering the validity of classical general relativity in the dynamical, strong-field regime.

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arXiv2025

Detection of a Higher Harmonic Quasi-normal Mode in the Ringdown Signal of GW231123

The ringdown phase of a gravitational wave signal from a binary black hole merger offers a unique laboratory for testing general relativity in the strong-field regime and probing the properties of the final remnant black hole. In this study, we analyze the ringdown of GW231123 and find strong evidence for a multimode quasinormal spectrum. Our analysis employs two time-domain methodologies: a full Bayesian inference and an enhanced F-statistic framework, which we extend to enable the calculation of Bayesian evidence and the reconstruction of posterior distributions for all model parameters. We report a statistically significant detection of the $\ell|m|n=200$ mode, with a $\log_{10}$(Bayes factor) of $5.3$, commencing at $12\,M$ after the peak amplitude--a time well within the accepted linear regime. This two-mode analysis yields a redshifted final mass of $305.6^{+35.7}_{-47.3}M _{\odot}$ and a final spin of $0.84^{+0.07}_{-0.14}$ at $90\%$ credibility, from a ringdown signal with a network signal-to-noise ratio of approximately $14.5$. Furthermore, a test of the no-hair theorem performed using the two detected modes reveals no deviation from the predictions of general relativity. These results highlight the power of the F-statistic methodology to uncover nuanced features in gravitational wave signals, thereby providing novel insights into the fundamental properties of black holes.

gr-qc↗

arXiv2025

Reanalyzing the ringdown signal of GW150914 using the F-statistic method

The ringdown phase of a gravitational wave (GW) signal from a binary black hole merger provides valuable insights into the properties of the final black hole and serves as a critical test of general relativity in the strong-field regime. A key aspect of this investigation is to determine whether the first overtone mode exists in real GW data, as its presence would offer significant implications for our understanding of general relativity under extreme conditions. To address this, we conducted a reanalysis of the ringdown signal from GW150914, using the newly proposed F-statistic method to search for the first overtone mode. Our results are consistent with those obtained through classical time-domain Bayesian inference, indicating that there is no evidence of the first overtone mode in the ringdown signal of GW150914. However, our results show the potentiality of utilizing the F-statistic methodology to unearth nuanced features within GW signals, thereby contributing novel insights into black hole properties.

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arXiv2025

A practical Bayesian method for gravitational-wave ringdown analysis with multiple modes

Gravitational-wave (GW) ringdown signals from black holes (BHs) encode crucial information about the gravitational dynamics in the strong-field regime, which offers unique insights into BH properties. In the future, the improving sensitivity of GW detectors is to enable the extraction of multiple quasi-normal modes (QNMs) from ringdown signals. However, incorporating multiple modes drastically enlarges the parameter space, posing computational challenges to data analysis. Inspired by the $F$-statistic method in the continuous GW searches, we develope an algorithm, dubbed as FIREFLY, for accelerating the ringdown signal analysis. FIREFLY analytically marginalizes the amplitude and phase parameters of QNMs to reduce the computational cost and speed up the full-parameter inference from hours to minutes, while achieving consistent posterior and evidence. The acceleration becomes more significant when more QNMs are considered. Rigorously based on the principle of Bayesian inference and importance sampling, our method is statistically interpretable, flexible in prior choice, and compatible with various advanced sampling techniques, providing a new perspective for accelerating future GW data analysis.

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arXiv2024

Gravitational wave ringdown analysis using the $\mathcal{F}$-statistic

After the final stage of the merger of two black holes, the ringdown signal takes an important role on providing information about the gravitational dynamics in strong field. We introduce a novel time-domain (TD) approach, predicated on the $\mathcal{F}$-statistic, for ringdown analysis. This method diverges from traditional TD techniques in that its parameter space remains constant irrespective of the number of modes incorporated. This feature is achieved by reconfiguring the likelihood and analytically maximizing over the extrinsic parameters that encompass the amplitudes and reference phases of all modes. Consequently, when performing the ringdown analysis under the assumption that the ringdown signal is detected by the Einstein Telescope, parameter estimation computation time is shortened by at most five orders of magnitude compared to the traditional TD method. We further establish that traditional TD methods become difficult when including multiple overtone modes due to close oscillation frequencies and damping times across different overtone modes. Encouragingly, this issue is effectively addressed by our new TD technique. The accessibility of this new TD method extends to a broad spectrum of research and offers flexibility for various topics within black hole spectroscopy applicable to both current and future gravitational wave detectors.

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arXiv2024

Constraints on Einstein-dilation-Gauss-Bonnet gravity and electric charge of compact binary systems from GW230529

In this work, we study the implications of GW230529 on gravity theories and the charge of black holes. The GW230529, which was initially released in O4a, is most likely neutron star-black hole (NSBH) mergers. We reanalyze the data from the GW230529 event to obtain bounds on the Einstein-dilation-Gauss-Bonnet (EdGB) gravity parameter $\sqrt{α_{\rm EdGB}}$ and the electric charge of compact binary systems. The event places a $90\%$ credible upper bounds on $\sqrt{α_{\rm EdGB}}$ of $\lesssim 0.298$ km. After including high order corrections of EdGB gravity, the bounds improve to $\sqrt{α_{\rm EdGB}} \lesssim 0.260$ km. Analyses of GW230529 also yield a $90\%$ credible upper bounds on the combination of charge-to-mass ratio of the binary components $ζ\lesssim 0.024$. The constraints are more stringent than those derived from previously observed single gravitational wave merger event.

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arXiv2024

Comparison between time-domain and frequency-domain Bayesian inferences to inspiral-merger-ringdown gravitational-wave signals

Time-domain (TD) Bayesian inference is important in ringdown analysis for gravitational wave (GW) astronomy. The validity of this method has been well studied by Isi and Farr [1]. Using GW190521 as an example, we study the TD method in detail by comparing it with the frequency-domain (FD) method as a complement to previous study. We argue that the autocovariance function (ACF) should be calculated from the inverse fast Fourier transform of the power spectral density (PSD), which is usually estimated by the Welch method. In addition, the total duration of the GW data that are used to estimate the PSD and the slice duration of the truncated ACF should be long enough. Only when these conditions are fully satisfied can the TD method be considered sufficiently equivalent to the FD method.

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arXiv2024

Constraints on charged black holes from merger-ringdown signals in GWTC-3 and prospects for the Einstein Telescope

Whether astrophysical black holes (BHs) can have charge is a question to be addressed by observations. In the era of gravitational wave (GW) astronomy, one can constrain the charge of a merged BH remnant using the merger-ringdown signal of the GW data. Extending earlier studies, we analyze five GW events in GWTC-3, assuming Kerr-Newman BHs. Our results show no strong evidence for a charged BH, and give a limit on the charge-to-mass-ratio $Q<0.37$ at $90\%$ credible level (CL). Due to the charge-spin degeneracy in the waveform and the limited signal-to-noise ratios (SNRs), it is challenging for LIGO/Virgo/KAGRA observations to provide better constraints. We further simulate data for the Einstein Telescope (ET), where SNRs can be as large as $\sim270$ in the ringdown signal. These simulated events allow us to consider the 220, 221, and 330 ringdown modes altogether, which can help break the charge-spin degeneracy. The analysis of a simulated GW150914-like signal shows that ET can improve the constraints on the charge-to-mass-ratio to $Q \lesssim 0.2$ at $90\%$ CL with one ringdown signal.

gr-qc↗

arXiv2023

Detection of astrophysical gravitational wave sources by TianQin and LISA

TianQin and LISA are space-based laser interferometer gravitational wave (GW) detectors planned to be launched in the mid-2030s. Both detectors will detect low-frequency GWs around $10^{-2}\,{\rm Hz}$, however, TianQin is more sensitive to frequencies above this common sweet-spot while LISA is more sensitive to frequencies below $10^{-2}\,{\rm Hz}$. Therefore, TianQin and LISA will be able to detect the same sources but with different accuracy depending on the source and its parameters. We consider some of the most important astrophysical sources -- massive black hole binaries, stellar-mass black hole binaries, double white dwarfs, extreme mass ratio inspirals, light and heavy intermediate mass ratio inspirals, as well as the stochastic gravitational background of astrophysical origin -- that TianQin and LISA will be able to detect. For each of these sources, we analyze how far they can be detected (detection distance) and how well their parameters can be measured (detection accuracy) using a Fisher Matrix analysis. We compare the results obtained by the three detection scenarios (TianQin alone, LISA alone, and joint detection by LISA and TianQin) highlighting the gains from joint detection as well as the contribution of TianQin and LISA to a combined study of astrophysical sources. In particular, we consider the different orientations, lifetimes, and duty cycles of the two detectors to explore how they can give a more complete picture when working together.

gr-qc↗

arXiv2023

Effect of Noise Estimation in Time-Domain Ringdown Analysis: A Case Study with GW150914

Accurate noise estimation from gravitational wave (GW) data is critical for Bayesian inference. However, recent studies on ringdown signal, such as those by Isi et al. [1], Cotesta et al. [2], and Isi and Farr [3], have encountered disagreement in noise estimation, leading to inconsistent results. The key discrepancy between these studies lies in the usage of different noise estimation methods, augmented by the usage of different sampling rates. We achieved consistent results across various sampling rates by correctly managing noise estimation, shown in the case study of the GW150914 ringdown signal. By conducting a time-domain Bayesian inference analysis on GW data, starting from the peak of the signal, we discovered that the first overtone mode is weakly supported by the amplitude distribution, with a confidence level of $1.6σ$, and is slightly disfavored by the log-Bayes factor. Overall, in our time-domain analysis we conclude there is no strong evidence for overtones in GW150914.

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