arXiv subjects

Wen-Biao Han

Publications and source records attributed to Wen-Biao Han.

At least 19 recordsLinked to original sources

arXiv2026

Electromagnetic responses driven by gravitational-wave memory in magnetar-flare outflows

An asymmetric relativistic outflow from a magnetar giant flare produces a step-like gravitational-wave (GW) memory. In the magnetized pair plasma surrounding the star, such GW memory drives transverse electromagnetic (EM) X-mode/fast-magnetosonic responses at the corresponding frequencies. We use this GW-memory spectrum to drive a global wave equation for a cold electron--positron pair plasma. With radiative boundary conditions excluding incoming waves, the driven response forms an outgoing EM mode that reaches the outer boundary of the source region. For central-engine energy-release timescales of $10$, $1$, and $0.15\,\mu\mathrm{s}$, 90\% of the integrated response energy lies below 23.3 kHz, 233 kHz, and 1.51 MHz, respectively. The principal response occupies the 10 kHz--1 MHz frequency band; a substantial extension into the 1--3 MHz frequency band also appears when a submicrosecond asymmetric-energy component is present. The electromagnetic response can escape from the source region and potentially propagate in the interstellar medium.

astro-ph.HE↗

arXiv2026

Coherent End-to-End Search for Generic Extreme-Mass-Ratio Inspirals

Extreme-mass-ratio inspirals (EMRIs) encode more than $10^5$ strong-field orbital cycles and are key targets for space-borne gravitational-wave interferometers, yet coherent recovery of generic systems over astrophysically broad priors remains unresolved. Successive Mock LISA, LISA, and Taiji Data Challenges (MLDCs, LDCs, and TDCs) have not yet produced a complete, generally reliable solution for blind EMRI detection and parameter recovery across such priors. The central obstacle is a needle-in-a-haystack likelihood: six phase-evolution parameters span a vast domain, producing an exceptionally narrow global maximum amid numerous secondary maxima. We show that higher-likelihood secondary maxima concentrate progressively around the global maximum and can therefore guide an adaptive contraction of the search volume. We exploit this structure through a reduced-dimensional profile likelihood and a coherent hierarchical strategy to search for EMRI signals across the full 14-dimensional parameter space. This enables the first end-to-end coherent parameter estimation for generic EMRIs with astrophysically broad priors. In stationary Gaussian LISA noise, the search recovers two half-year analytical-kludge signals with signal-to-noise ratios near 50, yielding fitting factors of 0.989 and 0.971, fractional errors of $10^{-3}$--$10^{-2}$ in the phase-evolution parameters and near $3\%$ in the distance, and error of less than $0.1$ radian in the sky location. The method turns secondary maxima into guides for a coherent hierarchical search.

gr-qc↗

arXiv2026

Horizon-redshift transfer in black-hole direct-wave damping

Direct waves from black-hole mergers may probe horizon dynamics, but their observed envelopes need not decay at the Kerr surface-gravity rate. We compute the complex-frequency spin-$-2$, $\ell=m=2$ Teukolsky response and combine it with a finite-duration near-horizon source whose outgoing amplitude is suppressed by gravitational redshift. The screened Kerr response to this finite-duration source produces an observable envelope damping $\geff<\kap$. For GW250114, this corresponds to $\geff\simeq0.4~{\rm ms}^{-1}$, consistent with a joint H1--L1 analysis of QNM-subtracted residuals. As a consistency check, the GW231226 remnant parameters give $\geff\simeq0.31~{\rm ms}^{-1}$, compatible with the event's residual profile. These results identify direct-wave envelope damping as an observable of horizon-redshift transfer rather than a direct measurement of surface gravity.

gr-qc↗

arXiv2026

Measurability of Quadrupole Deviations from Kerr in Binary black hole Mergers

We investigate the measurability of black hole quadrupole deviations from Kerr using five binary black hole mergers observed by the LIGO-Virgo-KAGRA Collaboration with the beyond-general-relativity full-waveform model $\Psi_{\mathrm{FD}}$. While earlier lower-SNR events mildly favored nonzero quadrupole deviations, the newly included high-SNR GWTC-4 events GW231226, GW230814, and GW250114 yield results increasingly consistent with the Kerr prediction. In particular, GW230814 and GW250114, the two highest-SNR events in our sample, yield deviations consistent with zero. We further perform separate inspiral and post-inspiral analyses and find both the posterior distributions centered close to $\Delta Q/Q=0$ for GW230814 and GW250114. Overall, the full-waveform, inspiral, and post-inspiral results for GW230814 and GW250114 reveal no observable departure from the no-hair theorem within the sensitivity of the current data and the $\Psi_{\mathrm{FD}}$ framework. Although the limited number of events prevents a definitive conclusion, future detections of additional high-SNR binary black hole mergers will enable increasingly stringent and robust tests of the Kerr nature of black holes.

gr-qc↗

arXiv2026

Strong-lensing effects in high-redshift massive black-hole binary population inference

High-redshift massive black-hole binary (MBHB) mergers provide a probe of black-hole seed formation and early galaxy assembly, but the population detected by LISA can be modified by galaxy-scale strong lensing. We quantify this effect for MBHB mergers at $10\leq z\leq20$ and assess its impact on the inference of intrinsic formation-channel fractions. We use four channels, corresponding to light- and heavy-seed scenarios with delayed and non-delayed mergers, and compute 4-year LISA-detectable event numbers with and without strong lensing. To bracket the uncertain lens population, we compare a conservative velocity-dispersion-function (VDF) prescription with an optimistic halo-mass-function (HMF)-based prescription. We consider a reference mixture with equal seed-channel weights and additional mixtures in which the intrinsic seed population is weighted toward selected formation channels, and jointly infer the formation fractions and the strength of the lensing contribution. Strong lensing does not affect all channels equally: it can change the detected channel mixture as well as the total number of detections. This effect is weak for the conservative VDF prescription, but becomes significant in the high-lensing-rate HMF case, where neglecting strong lensing can bias the recovered formation fractions. The inference precision depends on the underlying intrinsic channel composition, while the lensing contribution is more accurately recovered in the high-lensing-rate case. These results indicate that galaxy-scale strong-lensing effects and event-count information should be included when using high-redshift MBHB detections to infer intrinsic formation-channel fractions.

astro-ph.CO↗

arXiv2026

Finite Coherence in Gravitational Waves from Tidally Excited Axion Clouds

Axion clouds around rotating black holes form gravitational atoms whose tidal transitions can radiate gravitational waves in binaries. For strongly coupled Bohr crossings, transition radiation is governed by the outgoing two-level coherence, not by the transition probability alone. This coherence is suppressed both on the adiabatic branch and in the weak passage limit, but survives for intermediate sweep rates, producing a finite transition waveform and a localized orbital response. In more massive systems, fine and hyperfine transitions produce narrowband gravitational radiation and cumulative departures from vacuum binary waveforms. Coherent tidal crossings offer a gravitational-wave probe of axion-cloud dynamics.

gr-qc↗

arXiv2026

Long-Lived Ringing of Near-Extremal Kerr Black Holes Resonantly Driven by Extreme-Mass-Ratio Inspirals

Near-extremal Kerr black holes support zero-damped modes (ZDMs), whose small time-domain damping rates make them long-lived probes of the near-horizon region. We show that bound extreme-mass-ratio inspirals (EMRIs) can resonantly drive this response in vacuum general relativity. Using frequency-domain Teukolsky amplitudes for eccentric-inclined Kerr geodesics, we identify a source-supported orbital harmonic whose real frequency falls within one pole half-width of the fundamental gravitational ZDM. In the complex response, the pole contribution is enhanced by this small half-width, while complex-response tomography recovers the independently computed Kerr pole from real-frequency orbital data. After subtracting the smooth non-pole component, the residual exhibits the phase winding of a coherent simple pole, with a pole contribution comparable to the smooth non-pole part of the EMRI-sourced Teukolsky amplitude. The driven branch also lies in the superradiant regime and carries negative horizon flux. These results establish a pole-resolved, resonantly driven ZDM response by EMRIs and make the recovered pole half-width a route to measuring the horizon surface gravity.

gr-qc↗

arXiv2026

A self-consistent EOB--Teukolsky framework for generic extreme mass-ratio inspirals

We present a full-relativistic waveform model for extreme mass-ratio inspirals (EMRIs) by self-consistently combining the effective one-body (EOB) formalism with the Teukolsky equation. The model incorporates analytical, mass-ratio-informed geodesic solutions within a deformed Kerr metric into the source term of the Teukolsky equation, establishing a direct connection between finite-mass-ratio orbital dynamics and gravitational-wave emission. The resulting frequency-domain formulation is coupled to a high-performance solver for the homogeneous Teukolsky equation, enabling rapid evaluation of the tens of thousands of modes required for accurate EMRI waveforms. We generate waveforms and radiation fluxes for generic Kerr orbits and investigate the influence of finite-mass-ratio corrections beyond the test-particle limit. The results show that mass-ratio-dependent deformations produce measurable modifications to radiation fluxes, and accumulated waveform phases over observationally relevant timescales. Our framework provides a generic-orbit EOB--Teukolsky waveform model for future space-based GW data analysis.

gr-qc↗

arXiv2026

Probing Active Galactic Nuclei and Measuring the Hubble constant with Extreme-Mass-Ratio Inspirals

Extreme-mass-ratio inspirals (EMRIs) carry valuable information about their surrounding astrophysical environments. Over the course of their long-term evolution, interactions between the secondary object and the accretion disk can produce observable effects on both the orbital evolution and the emitted gravitational waveform. Based on the modifications to the companion's orbital evolution induced by the accretion disk environment, we investigate the feasibility of identifying the presence of accretion disk environmental effects in EMRI systems using gravitational wave signals. Within a Bayesian framework, we analyze the capability of EMRI systems with multiple parameter configurations to distinguish accretion disk environmental effects. Our results show that, under the $α$-disk model, all injected events can successfully identify the environment in which the EMRIs reside. Furthermore, we examined the improvement in the precision of Hubble constant measurements using the dark siren method after correctly identifying the accretion disk environment and constraining the relevant disk parameters. Constraining these environmental parameters may further deepen our understanding of the host environment, thereby enabling a more reliable inference of the physical properties of the accretion disk and its associated luminosity and ultimately improving the measurement of cosmological parameters. We find that the measurement precision for a single event can improve by as much as $20\%$. This work highlights the necessity of incorporating environmental effects into future EMRI data analysis. Proper modeling of such effects not only helps identify EMRI systems embedded in accretion disk environments but also further improves the precision of gravitational wave cosmological parameter inference.

gr-qc↗

arXiv2026

Waveforms and Fluxes of Generic Extreme-Mass-Ratio Inspirals with a Spinning Secondary

Extreme mass-ratio inspirals (EMRIs), comprising a stellar-mass compact object (CO) orbiting a supermassive black hole (BH), are key targets for future space-based gravitational-wave (GW) observatories. Incorporating the spin of the secondary body into waveform models not only enhances measurement precision but also offers insight into the spin distribution of stellar-mass COs. In this work, we construct the flux and waveform for an EMRI with a spinning secondary in a Kerr background under the linear-spin approximation. Using the radiative prescription (half-retarded minus half-advanced field), we calculate orbit-averaged fluxes for the fundamental constants of motion, including the energy, angular momentum, and the Carter-like constant. This framework provides a tractable route to generating waveforms that incorporate the secondary spin.

astro-ph.HE↗

arXiv2026

Towards Realistic Detection Pipelines of Taiji: New Challenges in Data Analysis and High-Fidelity Simulations of Space-Based Gravitational Wave Antenna

Taiji, a Chinese space-based gravitational wave (GW) detection project, aims to explore the millihertz GW universe with unprecedented sensitivity. By observing astrophysical and cosmological sources, including Galactic binaries, massive black hole binaries, extreme mass-ratio inspirals, and stochastic gravitational wave backgrounds, etc., Taiji is expected to deliver transformative insights into astrophysics, cosmology, and fundamental physics. However, Taiji's data analysis faces unique challenges compared to ground-based detectors like LIGO-Virgo-KAGRA, such as the overlap of numerous signals, extended data durations, more rigorous accuracy requirements for the waveform templates, incompletely characterized noise spectra, non-stationary noises, and various data anomalies. Taking Taiji as a representative example, this paper reviews the data characteristics and data analysis challenges of space-based GW detection, and introduces the second round of Taiji Data Challenge, a collection of simulation datasets designed as a shared platform for resolving these critical issues. This platform distinguishes itself from previous works by the systematic integration of orbital dynamics based on a full drag-free and attitude control simulation, extended noise sources, more complicated and overlapping GW signals, second-generation time-delay interferometry, and the coupling effect of time-varying arm-lengths, etc. Concurrently released is the open-source toolkit Triangle, which offers the capabilities for customized simulation of signals, noises, and other instrumental effects. By taking a step further towards realistic detection, Taiji Data Challenge II and Triangle altogether serve as a new testbed, supporting the development of Taiji's global analysis and end-to-end pipelines, and ultimately bridging the gaps between observation and scientific objectives.

gr-qc↗

arXiv2026

Inspiraling binary charged black holes in an external magnetic field: Application of post-Newtonian dynamics in Einstein-Maxwell theory

We present a systematic post-Newtonian treatment of binary charged black holes immersed in external magnetic fields within the framework of Einstein-Maxwell theory. By incorporating a uniform external magnetic field into the two-body Lagrangian expanded to first post-Newtonian order, we derive the complete equations of motion that capture both gravitational and electromagnetic interactions. The magnetic Lorentz force fundamentally alters the orbital dynamics, breaking the conservation of linear and angular momentum and inducing transitions from planar to three-dimensional trajectories. {Through numerical integration of these equations, we compute the resulting gravitational waveforms and characterize the distinctive magnetic field signatures through time-domain and frequency-domain analysis.} Our results demonstrate that strong background magnetic fields can substantially modify the orbital evolution and leave distinctive signatures in the gravitational wave signals. These findings provide a promising avenue for detecting charged black holes and probing magnetic field environments through gravitational wave observations.

gr-qc↗

arXiv2026

Revealing the origin of supermassive black holes with Taiji-TianQin network

The origin of supermassive black holes (SMBHs) is a pivotal problem in modern cosmology. This work explores the potential of the Taiji-TianQin space-borne gravitational-wave (GW) detector network to identify the formation channels of massive black hole binaries (MBHBs) at high redshifts ($z \gtrsim 10$). The network substantially improves detection capability, boosting the signal-to-noise ratio by a factor of 2.2-3.0 (1.06-1.14) relative to TianQin (Taiji) alone. It increases the detection rate of MBHBs formed from light seeds (LS) by more than 2.2 times and achieves over 96\% detection efficiency for those originating from heavy seeds (HS). Furthermore, the network enables component mass estimation with relative uncertainties as low as $\sim 10^{-4}$ at the $2σ$ level. These improvements facilitate the assembly of a well-constrained population sample, allowing robust measurement of the fractional contributions from different formation pathways. The network achieves high precision in distinguishing between LS and HS origins (7.4\% relative uncertainty at $2σ$) and offers moderate discrimination between delay and no-delay channels in HS-origin binaries (24\%). However, classification remains challenging for delay versus no-delay scenarios in LS-origin systems (58\%) due to significant population overlap. In conclusion, the Taiji-TianQin network will serve as a powerful tool for unveiling the origins of SMBHs through GW population studies.

gr-qc↗

arXiv2025

AInsteinBench: Benchmarking Coding Agents on Scientific Repositories

We introduce AInsteinBench, a large-scale benchmark for evaluating whether large language model (LLM) agents can operate as scientific computing development agents within real research software ecosystems. Unlike existing scientific reasoning benchmarks which focus on conceptual knowledge, or software engineering benchmarks that emphasize generic feature implementation and issue resolving, AInsteinBench evaluates models in end-to-end scientific development settings grounded in production-grade scientific repositories. The benchmark consists of tasks derived from maintainer-authored pull requests across six widely used scientific codebases, spanning quantum chemistry, quantum computing, molecular dynamics, numerical relativity, fluid dynamics, and cheminformatics. All benchmark tasks are carefully curated through multi-stage filtering and expert review to ensure scientific challenge, adequate test coverage, and well-calibrated difficulty. By leveraging evaluation in executable environments, scientifically meaningful failure modes, and test-driven verification, AInsteinBench measures a model's ability to move beyond surface-level code generation toward the core competencies required for computational scientific research.

cs.SE↗

arXiv2025

Gravitational Wave Phase shifts of black hole mergers in AGN Disks

Ground-based gravitational wave (GW) detectors have discovered about 200 compact object mergers. The astrophysical origins of these events are highly debated, and it is possible that at least a fraction of them originate from dynamical environments. Among these, the disks of active galactic nuclei (AGN) are particularly interesting as promising environments, as some observed properties may be more readily produced there. When compact objects merge in these environments, acceleration from the central supermassive black hole (SMBH) or nearby companions is inevitable. Such acceleration induces a phase shift in the observed GW waveforms, which can serve as a useful tool to distinguish the underlying merging environments for each GW event. In this paper, we investigate the expected distribution of such acceleration-induced GW phase shifts, using a semi-analytical model combined with a one-dimensional AGN population synthesis code. We find significant contributions from three-body interactions involving a nearby third object. Our results indicate that the GW phase shift is likely to be larger compared to other channels, making it distinguishable by future GW facilities such as TianQin, DECIGO, Taiji, Einstein Telescope, and Cosmic Explorer. Interestingly, a notable fraction of mergers in fact exhibit a significant GW phase shift ($\gtrsim~{\rm 1\ rad}$) at frequencies above $10~{\rm Hz}$, which could even be detectable by current GW detectors such as LIGO/Virgo/KAGRA. Additionally, if gas-hardening during three-body interactions is taken into account, the GW frequency can be boosted to $\gtrsim 10~{\rm Hz}$, potentially further aiding in the detection of the phase shift.

astro-ph.HE↗

arXiv2025

Analytical solutions of bound timelike geodesic orbits in effective-one-body frame

We derive the approximate analytical solutions of the bound timelike geodesic orbits in the effective-one-body (EOB) frame with extreme-mass ratio limit. The analytical solutions are expressed in terms of the elliptic integrals using Mino time $λ$ as the independent variable. Since Mino time decouples the $r$ and $θ$-motion, we also give explicit expressions for three orbital frequencies $Ω_r, ~Ω_θ, ~Ω_ϕ$ using the Fourier series expansion. With these analytical expressions at hand, we can perform Fourier expansions in Mino time $λ$ for any function expressed in terms of the coordinates $(r,θ,ϕ)$. In particular, the observer's time t is decomposed into Mino time $λ$, and the frequency-domain description is constructed from the $λ$-Fourier expansion and the expansion of t. These analytical expressions are quite simple to implement, and can be applicable for calculating gravitational waves (GWs) from extreme mass-ratio inspirals (EMRIs) with the frequency-domain Teukolsky equation.

gr-qc↗

arXiv2025

Constraining the Deviation of Kerr Metric via Bumpy Parameterization and Particle Swarm Optimization in Extreme Mass-Ratio Inspirals

Measurement of deviations in the Kerr metric using gravitational wave (GW) observations will provide a clear signal of new Physics. Previous studies have developed multiple parameterizations (e.g. ``bumpy" spacetime) to characterize such deviations in extreme mass ratio inspirals (EMRI) and employed analyses based on the Fisher information matrix (FIM) formalism to quantify the constraining power of space-borne GW detectors like LISA and Tianqin, e.g., achieving a constraint sensitivity levels of $10^{-4} \sim 10^{-2}$ on the dimensionless bumpy parameter $δ\tilde{Q}$ under varying source configurations in analytical kluge waveform for LISA. In this paper, we advance prior analyses by integrating particle swarm optimization (PSO) with matched filtering under a restricted parameter search range to enforce a high probability of convergence for PSO. Our results reveal a significant number of degenerate peaks in the likelihood function over the signal parameter space with values that exceed the injected one. This extreme level of degeneracy arises from the involvement of the additional bumpy parameter $δ\tilde{Q}$ in the parameter space and introduces systematic errors in parameter estimation. We show that these systematic errors can be mitigated using information contained in the ensemble of degenerate peaks, thereby restoring the reliability of astrophysical inferences about EMRI systems from GW observations. This study highlights the critical importance of accounting for such degeneracies, which are absent in FIM-based analyses, and points out future directions for improving EMRI data analysis.

gr-qc↗

arXiv2025

Indication for a compact object next to a LIGO-Virgo binary black hole merger

The astrophysical origin of binary black hole (BBH) mergers remains uncertain, although many events have been observed by the LIGO-Virgo-KAGRA network. Such mergers are potentially originated in the vicinity of massive black holes (MBHs). GW190814, due to its secondary mass and mass ratio being beyond the expectations of isolated stellar evolution theories, is a promising event that has occurred in an active galactic nucleus (AGN) disk. In this model, a compact object resides in the vicinity of a merging BBH. Here we report multiple pieces of evidence suggesting that GW190814 is a BBH merging near a compact object. The orbital motion of BBHs around a third body produces a line-of-sight acceleration (LSA) and induces a varying Doppler shift. Using a waveform template that considers LSA, we perform Bayesian inference on a few BBH events with a high signal-to-noise ratio in the gravitational-wave (GW) transient catalog. Compared to the model for isolated BBH mergers, we obtain significantly higher network signal-to-noise ratios for GW190814 with the inclusion of LSA, constraining the LSA to $a = 0.0015^{+0.0008}_{-0.0008} ~c~\mathrm{s}^{-1}$ at a $90 \%$ confidence level. Additionally, the Bayes factor for the LSA case over the isolated case is $58/1$, indicating that the GW data strongly prefer the LSA model. We conclude that this is the first indication showing merging BBHs are located near a third compact object.

astro-ph.HE↗