arXiv subjects

Xing-Yu Zhong

Publications and source records attributed to Xing-Yu Zhong.

7 recordsLinked to original sources

arXiv2025

Mapping inspiral-merger-ringdown waveforms of binary black holes from black hole perturbation waveforms by machine learning

Identifying weak gravitational wave signals in noise and estimating the source properties require high-precision waveform templates. Numerical relativity (NR) simulations can provide the most accurate waveforms. However, it is challenging to compute waveform templates in high-dimensional parameter space using NR simulations due to high computational costs. In this work, we implement a novel waveform mapping method, which is an alternative approach to the existing analytical approximations, based on closed-form continuous-time neural networks. This machine-learning-based method greatly improves the efficiency of calculating waveform templates for arbitrary source parameters, such as the binary mass ratio and the spins of component black holes. Based on this method, we present \textit{BHP2NRMLSur}, a class of models (including nonspinning and spin-aligned ones) that maps point-particle black hole perturbation theory waveforms into NR and surrogate waveforms. The nonspinning model provides highly accurate waveforms that match the NR waveforms to the level of $\gtrsim 0.995$. The spin-aligned model reduces the required input parameters and hence improves the efficiency of the waveform generation -- it takes a factor of $\sim 50$ less time than existing NR surrogate models to generate $100,000$ waveforms, with a mismatch of $<0.01$ compared to the NR waveforms from the Simulating eXtreme Spacetimes collaboration.

gr-qc↗

arXiv2025

Distinguishing compact objects in extreme-mass-ratio inspirals by gravitational waves

Extreme-mass-ratio inspirals (EMRIs) are promising gravitational-wave (GW) sources for space-based GW detectors. EMRI signals typically have long durations, ranging from several months to several years, necessitating highly accurate GW signal templates for detection. In most waveform models, compact objects in EMRIs are treated as test particles without accounting for their spin, mass quadrupole, or tidal deformation. In this study, we simulate GW signals from EMRIs by incorporating the spin and mass quadrupole moments of the compact objects. We evaluate the accuracy of parameter estimation for these simulated waveforms using the Fisher Information Matrix (FIM) and find that the spin, tidal-induced quadruple, and spin-induced quadruple can all be measured with precision ranging from $10^{-2}$ to $10^{-1}$, particularly for a mass ratio of $\sim$$10^{-4}$. Assuming the ``true'' GW signals originate from an extended body inspiraling into a supermassive black hole, we compute the signal-to-noise ratio (SNR) and Bayes factors between a test-particle waveform template and our model, which includes the spin and quadrupole of the compact object. Our results show that the spin of compact objects can produce detectable deviations in the waveforms across all object types, while tidal-induced quadrupoles are only significant for white dwarfs, especially in cases approaching an intermediate-mass ratio. Spin-induced quadrupoles, however, have negligible effects on the waveforms. Therefore, our findings suggest that it is possible to distinguish primordial black holes from white dwarfs, and, under certain conditions, neutron stars can also be differentiated from primordial black holes.

gr-qc↗

arXiv2023

Influence of mass-ratio corrections in extreme-mass-ratio inspirals for testing general relativity

The popular waveform templates of extreme-mass-ratio inspirals usually omit the mass-ratio corrections in the conservative dynamics, and employ adiabatic approximation to include the radiation reaction. With the help of effective-one-body dynamics, we investigate the influence of mass-ratio corrections in the conservative part on the gravitational waves. We find that for the extra-relativistic orbits, the mass-ratio corrections can produce obvious orbital dephasing even for very small mass-ratio and then affect the waveforms. More importantly, it is noted that omitting the mass-ratio corrections in waveform templates may induce a fake signal of deviation from general relativity.

gr-qc↗

arXiv2022

Detecting properties of echoes from inspiraling stage with ground-based detectors

The nature of black holes is one of most exciting issues in gravitational physics. If there is an exotic compact object as the compact as a black hole but without a horizon, gravitational wave echoes may be produced after the merger. In this work, we show that for extreme-mass-ratio binaries, even during the inspiraling phase of compact binary coalescence, the exists of hard surface of the exotic compact object will produce detectable signals on the gravitational waves. We predict that once the LIGO-Virgo-KAGRA, Einstein Telescope or Cosmic Explorer detect such kind of sources, our model shows that one can constrain the properties of surfaces of the compact objects in inspiraling stage better than the current level.

gr-qc↗

arXiv2021

Geometrized effective-one-body formalism for extreme-mass-ratio limits: Generic orbits

Compact objects inspiraling into supermassive black holes, known as extreme-mass-ratio inspirals, are an important source for future space-borne gravitational-wave detectors. When constructing waveform templates, usually the adiabatic approximation is employed to treat the compact object as a test particle for a short duration, and the radiation reaction is reflected in the changes of the constants of motion. However, the mass of the compact object should have contributions to the background. In the present paper, employing the effective-one-body formalism, we analytically calculate the trajectories of a compact object around a massive Kerr black hole with generally three-dimensional orbits and express the fundamental orbital frequencies in explicit forms. In addition, by constructing an approximate "constant" similar to the Carter constant, we transfer the dynamical quantities such as energy, angular momentum, and the "Carter constant" to the semilatus rectum, eccentricity, and orbital inclination with mass-ratio corrections. The linear mass-ratio terms in the formalism may not be sufficient for accurate waveforms, but our analytical method for solving the equations of motion could be useful in various approaches to building waveform models.

gr-qc↗

arXiv2020

Very extreme mass-ratio bursts in the Galaxy and neighbouring galaxies in relation to space-borne detectors

Two recent papers\citep{xmri1, xmri2} revealed that in our Galaxy there are very extreme-mass-ratio inspirals composed by brown dwarfs and the supermassive black hole at the center of the Galaxy. The event rates estimated in these papers are very considerable for future space-borne detectors. In addition, there are plunge events during the formation of inspiraling orbits. In this work, we calculate the gravitational waves from compact objects (brown dwarf, primordial black hole and etc.) plunging into or being scattered by the central supermassive black hole. We find that for space-borne detectors the signal-to-noise ratios of these bursts are quite high. The event rates are estimated as $\sim$ $0.01 {\rm{yr}^{-1}}$ for the Galaxy. If we are lucky, this kind of very extreme-mass-ratio bursts will offer a unique chance to reveal the nearest supermassive black hole and nuclei dynamics. The event rate can be as large as 4 $\sim$ 8 ${\rm yr^{-1}}$ in 10 Mpc, and because the signal is strong enough for observations by space-borne detectors, we have a good chance of being able to probe the nature of neighboring black holes.

gr-qc↗

arXiv2020

Numerical simulation of sky localization for LISA-TAIJI joint observation

LISA is considered to be launched alongside the Athena to probe the energetic astrophysical processes. LISA can determine the direction of sources for Athena's follow-up observation. As another space gravitational wave mission, TAIJI is expected to be launched in the 2030s. The LISA-TAIJI network would provide abundant merits for sources understanding. In this work, we simulate the joint LISA-TAIJI observations for gravitational waves from coalescing supermassive black hole binaries and monochromatic sources. By using the numerical mission orbits, we evaluate the performances of sky localization for various time-delay interferometry channels. For 30 days observation until coalescence, the LISA-TAIJI network in optimal operation can localize all simulated binary sources, $(10^7,\ 3.3 \times 10^6)\ M_\odot$, $(10^6,\ 3.3 \times 10^5)\ M_\odot$ and $(10^5,\ 3.3 \times 10^4)\ M_\odot$ at redshift $z=2$, in 0.4 deg$^2$ (field of view of Wide Field Imager on Athena). The angular resolution can be improved by more than 10 times comparing to LISA or TAIJI single detector at a given percentage of population. The improvements for monochromatic sources at 3 mHz and 10 mHz are relatively moderate in one-year observation. The precision of sky localization could be improved by around 1 to 3 times comparing to single LISA at a given percentage of sources. For a simulated 90 days observation for monochromatic waves, the LISA-TAIJI network still represents a considerable localization advantage which could be more than 10 times better.

gr-qc↗