arXiv subjects

Hideyuki Tagoshi

Publications and source records attributed to Hideyuki Tagoshi.

At least 19 recordsLinked to original sources

arXiv2026

N-body next-to-leading order gravitational spin-orbit interaction via effective field theory

Using the post-Newtonian effective field theory (PN-EFT) formalism for spinning gravitating bodies, we derive the next-to-leading-order (NLO) spin-orbit potential and Hamiltonian for a system of N spinning bodies in general relativity. This extends the EFT treatment of the binary case to arbitrary N. We present two derivations: one in the generalized canonical gauge, and one based on the covariant spin supplementary condition (SSC), followed by a noncanonical transformation to canonical variables. In both approaches, the only new contributions beyond the binary case are three-body interaction diagrams. The canonical Hamiltonians obtained from the two EFT routes agree with the known ADM N-body Hamiltonian of Hartung and Steinhoff up to a canonical transformation.

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arXiv2023

Constraint on the progenitor of binary black hole merger using Population III star formation channel

The observations of gravitational waves have revealed the existence of black holes above $30 M_\odot$. A variety of channels have been proposed as their origin, including the Population III (Pop. III) star channel. In this channel, Binary Black Holes (BBHs) containing such massive BHs are naturally produced. In this paper, we examine the relative fractions of five formation channels that may contribute to the origins of BBHs: isolated binaries of either Population I or Population II stars, PopIII isolated binaries, chemically homogeneous evolution, and the dynamical evolution in globular clusters and nuclear star clusters, using the LIGO-Virgo-KAGRA gravitational-wave transient catalog (GWTC-3) events through hierarchical Bayesian inference. We find that the branching fraction of the Pop. III BBH channel is $0.11^{+0.08}_{-0.06}$ within our framework, consistent with the local merger rate density of the model of the Pop. III BBH channel we adopt. We also evaluate the contributions to the catalogue using the selection effect of each formation channel and find that Pop. III BBH could contribute at a non-negligible rate, though the adequacy of these ratios should be subject to ongoing discussion.

astro-ph.HE↗

arXiv2023

Searching for gravitational wave echoes from black hole binary events in the third observing run of LIGO, Virgo, and KAGRA collaborations

Gravitational wave echo signals have been proposed as evidence for the modification of the spacetime structure near the classical event horizon. These signals are expected to occur after the mergers of compact binaries as a sequence of weak pulse-like signals. Some studies have shown evidence of the echo signals from several binary black hole merger events. On the other hand, the other studies have shown the low significance of such signals from various events in the first, second and third observing runs (O1, O2 and O3). Our previous study also shows the low significance of echo signals from events in O1 and O2, though, we observe that more than half of the events have p-value smaller than 0.1 when the simply modeled waveform is used for the analysis. Since there are only nine events appropriate for this analysis in O1 and O2, it is necessary to analyze more events to evaluate the significance statistically. In this study, we search for echo signals from binary black hole events observed during O3 operated by LIGO, Virgo and KAGRA collaborations. We perform the template-based search by using two different models for echo signal templates: simply modeled one and physically motivated one. Our results show that the distributions of p-values for all events analyzed in this study are consistent with the noise distribution. This means that no significant echo signals are found for both models from O3 events.

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arXiv2022

Mass$\unicode{x2013}$spin Re-Parameterization for Rapid Parameter Estimation of Inspiral Gravitational-Wave Signals

Estimating the source parameters of gravitational waves from compact binary coalescence(CBC) is a key analysis task in gravitational-wave astronomy. To deal with the increasing detection rate of CBC signals, optimizing the parameter estimation analysis is crucial. The analysis typically employs a stochastic sampling technique such as Markov Chain Monte Carlo(MCMC), where the source parameter space is explored and regions of high Bayesian posterior probability density are found. One of the bottlenecks slowing down the analysis is the non-trivial correlation between masses and spins of colliding objects, which makes the exploration of mass$\unicode{x2013}$spin space extremely inefficient. We introduce a new set of mass$\unicode{x2013}$spin sampling parameters which makes the posterior distribution to be simple in the new parameter space, regardless of the true values of the parameters. The new parameter combinations are obtained as the principal components of the Fisher matrix for the restricted 1.5 post-Newtonian waveform. Our re-parameterization improves the efficiency of MCMC by a factor of $\sim10$ for binary neutron star with narrow-spin prior ($|\vec{\chi}|<0.05$) and $\sim100$ with broad-spin prior ($|\vec{\chi}|<0.99$), under the assumption that the binary has spins aligned with its orbital angular momentum.

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arXiv2019

Reanalysis of the binary neutron star mergers GW170817 and GW190425 using numerical-relativity calibrated waveform models

We reanalyze gravitational waves from binary-neutron-star mergers GW170817 and GW190425 using a numerical-relativity (NR) calibrated waveform model, the TF2+_Kyoto model, which includes nonlinear tidal terms. For GW170817, by imposing a uniform prior on the binary tidal deformability $\tilde{\Lambda}$, the symmetric $90\%$ credible interval of $\tilde{\Lambda}$ is estimated to be $481^{+436}_{-359}$ and $402^{+465}_{-279}$ for the case of $f_\mathrm{max}=1000$ and $2048~\mathrm{Hz}$, respectively, where $f_\mathrm{max}$ is the maximum frequency in the analysis. We also reanalyze the event with other waveform models: two post-Newtonian waveform models (TF2_PNTidal and TF2+_PNTidal), the TF2+_NRTidal model that is another NR calibrated waveform model, and its upgrade, the TF2+_NRTidalv2 model. While estimates of parameters other than $\tilde{\Lambda}$ are broadly consistent among various waveform models, our results indicate that estimates of $\tilde{\Lambda}$ depend on waveform models. However, the difference is smaller than the statistical error. For GW190425, we can only obtain little information on the binary tidal deformability. The systematic difference among the NR calibrated waveform models will become significant to measure $\tilde{\Lambda}$ as the number of detectors and events increase and sensitivities of detectors are improved.

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arXiv2019

A nonparametric method to assess significance of events in search for gravitational waves with false discovery rate

In this paper, we present a consistent procedure to assess the significance of gravitational wave events observed by laser interferometric gravitational wave detectors based on the background distribution of detection statistic. We propose a non-parametric method to estimate $p$-value. Based on the estimated $p$-values, we propose a new procedure to assess the significance of a particular event with $q$-value which is the minimum false discovery rate that can be attained when calling the event significant. The $q$-value gives us a criterion on the significance of events which is different from $P_{\rm astro}$ which is used in the LIGO-Virgo analysis and in other analysis. The proposed procedure is applied to the 1-OGC and 2-OGC catalogs [2][3]. For most of the events which were claimed significant in [2] and [3], we also obtain the same results. However, there are differences in the significance for several marginal events. Since the proposed procedure does not require any assumptions on signal and noise, it is very simple and straightforward. The procedure is also applicable to other searches for gravitational waves whose background distribution of detection statistic is difficult to know.

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arXiv2019

Searching for black hole echoes from the LIGO-Virgo Catalog GWTC-1

We have examined gravitational wave echo signals for nine binary black hole merger events observed by Advanced LIGO and Virgo during the first and second observation runs. To construct an echo template, we consider Kerr spacetime, where the event horizon is replaced by a reflective membrane. We use frequency-dependent reflection rate at the angular potential barrier, which is fitted to the numerical data obtained by solving Teukolsky equations. This reflection rate gives a frequency-dependent transmission rate that is suppressed at lower frequencies in the template. We also take into account the overall phase shift of the waveform as a parameter, which arises when the wave is reflected at the membrane and potential barrier. Using this template based on black hole perturbation, we find no significant echo signals in the binary black hole merger events.

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arXiv2018

Discrepancy in tidal deformability of GW170817 between the Advanced LIGO twin detectors

We find that the Hanford and Livingston detectors of Advanced LIGO derive a distinct posterior probability distribution of binary tidal deformability tilde{Lambda} of the first binary-neutron-star merger GW170817. By analyzing public data of GW170817 with a nested-sampling engine and the default TaylorF2 waveform provided by the LALInference package, the probability distribution of the binary tidal deformability derived by the LIGO-Virgo detector network turns out to be determined dominantly by the Hanford detector. Specifically, by imposing the flat prior on tidal deformability of individual stars, symmetric 90% credible intervals of tilde{Lambda} are estimated to be 527^{+619}_{-345} with the Hanford detector, 927^{+522}_{-619} with the Livingston detector, and 455^{+668}_{-281} with the LIGO-Virgo detector network. Furthermore, the distribution derived by the Livingston detector changes irregularly when we vary the maximum frequency of the data used in the analysis. This feature is not observed for the Hanford detector. While they are all consistent, the discrepancy and irregular behavior suggest that an in-depth study of noise properties might improve our understanding of GW170817 and future events.

astro-ph.HE↗

arXiv2017

Optimal follow-up observations of gravitational wave events with small optical telescopes

We discuss optimal strategy for follow-up observations by 1-3 m class optical/infrared telescopes which target optical/infrared counterparts of gravitational wave events detected with two laser interferometric gravitational wave detectors. The probability maps of transient sources, such as coalescing neutron stars and/or black holes, determined by two laser interferometers generally spread widely. They include the distant region where it is difficult for small aperture telescopes to observe the optical/infrared counterparts. For small telescopes, there is a possibility that it is more advantageous to search for nearby region even if the probability inferred by two gravitational wave detectors is low. We show that in the case of the first three events of advanced LIGO, the posterior probability map, derived by using a distance prior restricted to a nearby region, is different from that derived without such restriction. This suggests that the optimal strategy for small telescopes to perform follow-up observation of LIGO-Virgo's three events are different from what has been searched so far. We also show that, when the binary is nearly edge-on, it is possible that the true direction is not included in the 90% posterior probability region. We discuss the optimal strategy to perform optical/infrared follow-up observation with small aperture telescopes based on these facts.

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arXiv2017

Black hole ringdown echoes and howls

Recently the possibility of detecting echoes of ringdown gravitational waves from binary black hole mergers was shown. The presence of echoes is expected if the black hole is surrounded by a mirror that reflects gravitational waves near the horizon. Here, we present slightly more sophisticated templates motivated by a waveform which is obtained by solving the linear perturbation equation around a Kerr black hole with a complete reflecting boundary condition in the stationary traveling wave approximation. We estimate that the proposed template can bring about $10\%$ improvement in the signal-to-noise ratio.

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arXiv2017

On the stability of a superspinar

The superspinar proposed by Gimon and Horava is a rapidly rotating compact entity whose exterior is described by the over-spinning Kerr geometry. The compact entity itself is expected to be governed by superstringy effects, and in astrophysical scenarios it can give rise to interesting observable phenomena. Earlier it was suggested that the superspinar may not be stable but we point out here that this does not necessarily follow from earlier studies. We show, by analytically treating the Teukolsky equations by Detwiler's method, that in fact there are infinitely many boundary conditions that make the superspinar stable, and that the modes will decay in time. It follows that we need to know more on the physical nature of the superspinar in order to decide on its stability in physical reality.

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arXiv2016

The potential of advanced ground-based gravitational wave detectors to detect generic deviations from general relativity

We discuss the potential of the advanced ground-based gravitational-wave detectors such as LIGO, Virgo, and KAGRA to detect generic deviations of gravitational waveforms from the predictions of general relativity. We use the parameterized post-Einsteinian formalism to characterize the deviations, and assess what magnitude of deviations are detectable by using an approximate decision scheme based on Bayesian statistics. We find that there exist detectable regions of the parameterized post-Einsteinian parameters for different binary masses from the observation of a single gravitational wave event. The regions are not excluded by currently existing binary pulsar observations for the parameterized post-Einsteinian parameters at higher post-Newtonian order. We also find that neglect of orbital eccentricity or tidal deformation effects do not cause a significant bias on the detectable region of generic deviations from general relativity.

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arXiv2015

Detectability of bigravity with graviton oscillations using gravitational wave observations

The gravitational waveforms in the ghost-free bigravity theory exhibit deviations from those in general relativity. The main difference is caused by graviton oscillations in the bigravity theory. We investigate the prospects for the detection of the corrections to gravitational waveforms from coalescing compact binaries due to graviton oscillations and for constraining bigravity parameters with the gravitational wave observations. We consider the bigravity model discussed by the De Felice-Nakamura-Tanaka subset of the bigravity model, and the phenomenological model in which the bigravity parameters are treated as independent variables. In both models, the bigravity waveform shows strong amplitude modulation, and there can be a characteristic frequency of the largest peak of the amplitude, which depends on the bigravity parameters. We show that there is a detectable region of the bigravity parameters for the advanced ground-based laser interferometers, such as Advanced LIGO, Advanced Virgo, and KAGRA. This region corresponds to the effective graviton mass of $μ\geq 10^{-17}~{\rm cm}^{-1}$ for $\tilde{c}-1 \geq 10^{-19}$ in the phenomenological model, while $μ\geq 10^{-16.5}~{\rm cm}^{-1}$ for $κξ_c^2 \geq 10^{0.5}$ in the De Felice-Nakamura-Tanaka subset of the bigravity model, respectively, where $\tilde{c}$ is the propagation speed of the massive graviton and $κξ_c^2$ corresponds to the corrections to the gravitational constant in general relativity. These regions are not excluded by existing solar system tests. We also show that, in the case of $1.4-1.4M_{\rm sun}$ binaries at the distance of $200~{\rm Mpc}$, $\logμ^2$ is determined with an accuracy of ${\cal O}$(0.1)\% at the 1$σ$ level for a fiducial model with $μ^2=10^{-33}~{\rm cm}^{-2}$ in the case of the phenomenological model.

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arXiv2014

Gravitational perturbation induced by a rotating ring around a Kerr black hole

The linear perturbation of a Kerr black hole induced by a rotating massive circular ring is discussed by using the formalism by Teukolsky, Chrzanowski, Cohen and Kegeles. In these formalism, the perturbed Weyl scalars, $ψ_0$ and $ψ_4$, are first obtained from the Teukolsky equation. The perturbed metric is obtained in a radiation gauge via the Hertz potential. The computation can be done in the same way as in our previous paper, in which we considered the perturbation of a Schwarzschild black hole induced by a rotating ring. By adding lower multipole modes such as mass and angular momentum perturbation which are not computed by the Teukolsky equation, and by appropriately setting the parameters which are related to the gauge freedom, we obtain the perturbed gravitational field which is smooth except on the equatorial plane outside the ring.

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arXiv2014

Synergy of short gamma ray burst and gravitational wave observations: Constraining the inclination angle of the binary and possible implications for off-axis gamma ray bursts

Compact binary mergers are the strongest candidates for the progenitors of Short Gamma Ray Bursts (SGRBs). If a gravitational wave (GW) signal from the compact binary merger is observed in association with a SGRB, such a synergy can help us understand many interesting aspects of these bursts. We examine the accuracies with which a world wide network of gravitational wave interferometers would measure the inclination angle (the angle between the angular momentum axis of the binary and the observer's line of sight) of the binary. We compare the projected accuracies of GW detectors to measure the inclination angle of double neutron star (DNS) and neutron star-black hole (NS-BH) binaries for different astrophysical scenarios. We find that a 5 detector network can measure the inclination angle to an accuracy of $\sim 5.1 (2.2)$ degrees for a DNS(NS-BH) system at 200 Mpc if the direction of the source as well as the redshift is known electromagnetically. We argue as to how an accurate estimation of the inclination angle of the binary can prove to be crucial in understanding off-axis GRBs, the dynamics and the energetics of their jets, and help the searches for (possible) orphan afterglows of the SGRBs.

astro-ph.HE↗

arXiv2014

Parameter estimation of neutron star-black hole binaries using an advanced gravitational-wave detector network: Effects of the full post-Newtonian waveform

We investigate the effects of using the {\it full} waveform (FWF) over the conventional {\it restricted} waveform (RWF) of the inspiral signal from a coalescing compact binary (CCB) system in extracting the parameters of the source, using a global network of second generation interferometric detectors. We study a hypothetical population of (1.4-10)$M_\odot$ NS-BH binaries (uniformly distributed and oriented in the sky) by employing the full post-Newtonian waveforms, which not only include contributions from various harmonics other than the dominant one (quadrupolar mode) but also the post-Newtonian amplitude corrections associated with each harmonic, of the inspiral signal expected from this system. It is expected that the GW detector network consisting of the two LIGO detectors and a Virgo detector will be joined by KAGRA and by proposed LIGO-India. We study the problem of parameter estimation with all 16 possible detector configurations. Comparing medians of error distributions obtained using FWFs with those obtained using RWFs (which only include contributions from the dominant harmonic with Newtonian amplitude) we find that the measurement accuracies for luminosity distance and the cosine of the inclination angle improve almost by a factor of 1.5-2 depending upon the network under consideration. Although the use of FWF does not improve the source localization accuracy much, the global network consisting of five detectors will improve the source localization accuracy by a factor of 4 as compared to the estimates using a 3 detector LIGO-Virgo network for the same waveform model.

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arXiv2014

Gravitational field of a Schwarzschild black hole and a rotating mass ring

The linear perturbation of the Kerr black hole has been discussed by using the Newman--Penrose and the perturbed Weyl scalars, $ψ_0$ and $ψ_4$ can be obtained from the Teukolsky equation. In order to obtain the other Weyl scalars and the perturbed metric, a formalism was proposed by Chrzanowski and by Cohen and Kegeles (CCK) to construct these quantities in a radiation gauge via the Hertz potential. As a simple example of the construction of the perturbed gravitational field with this formalism, we consider the gravitational field produced by a rotating circular ring around a Schwarzschild black hole. In the CCK method, the metric is constructed in a radiation gauge via the Hertz potential, which is obtained from the solution of the Teukolsky equation. Since the solutions $ψ_0$ and $ψ_4$ of the Teukolsky equations are spin-2 quantities, the Hertz potential is determined up to its monopole and dipole modes. Without these lower modes, the constructed metric and Newman--Penrose Weyl scalars have unphysical jumps on the spherical surface at the radius of the ring. We find that the jumps of the imaginary parts of the Weyl scalars are cancelled when we add the angular momentum perturbation to the Hertz potential. Finally, by adding the mass perturbation and choosing the parameters which are related to the gauge freedom, we obtain the perturbed gravitational field which is smooth except on the equatorial plane outside the ring. We discuss the implication of these results to the problem of the computation of the gravitational self-force to the point particles in a radiation gauge.

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arXiv2013

Post-Newtonian factorized multipolar waveforms for spinning, non-precessing black-hole binaries

We generalize the factorized resummation of multipolar waveforms introduced by Damour, Iyer and Nagar to spinning black holes. For a nonspinning test-particle spiraling a Kerr black hole in the equatorial plane, we find that factorized multipolar amplitudes which replace the residual relativistic amplitude f_{l m} with its l-th root, ρ_{l m} = f_{l m}^{1/l}, agree quite well with the numerical amplitudes up to the Kerr-spin value q \leq 0.95 for orbital velocities v \leq 0.4. The numerical amplitudes are computed solving the Teukolsky equation with a spectral code. The agreement for prograde orbits and large spin values of the Kerr black hole can be further improved at high velocities by properly factoring out the lower-order post-Newtonian contributions in ρ_{l m}. The resummation procedure results in a better and systematic agreement between numerical and analytical amplitudes (and energy fluxes) than standard Taylor-expanded post-Newtonian approximants. This is particularly true for higher-order modes, such as (2,1), (3,3), (3,2), and (4,4) for which less spin post-Newtonian terms are known. We also extend the factorized resummation of multipolar amplitudes to generic mass-ratio, non-precessing, spinning black holes. Lastly, in our study we employ new, recently computed, higher-order post-Newtonian terms in several subdominant modes, and compute explicit expressions for the half and one-and-half post-Newtonian contributions to the odd-parity (current) and even-parity (odd) multipoles, respectively. Those results can be used to build more accurate templates for ground-based and space-based gravitational-wave detectors.

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