A5082436151- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Superconducting and THz Device Technology
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Geophysics and Sensor Technology
- Stellar, planetary, and galactic studies
- High-Energy Particle Collisions Research
- Quantum chaos and dynamical systems
- Laser-Plasma Interactions and Diagnostics
- Magnetic confinement fusion research
- Astro and Planetary Science
- Planetary Science and Exploration
- Space Satellite Systems and Control
- Black Holes and Theoretical Physics
- Advanced Thermodynamic Systems and Engines
- Geomagnetism and Paleomagnetism Studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Seismic Imaging and Inversion Techniques
Tohoku University
2011-2024
Kyoto University
2015-2024
Max Planck Institute for Gravitational Physics
2019-2024
Yukawa Institute for Theoretical Physics
2014-2024
SRON Netherlands Institute for Space Research
2024
Tokyo City University
2024
Japan Aerospace Exploration Agency
2024
Institute of Space and Astronautical Science
2024
Instituto de Física Teórica
2024
The University of Tokyo
2019-2022
The objectives of the DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) are to open a new window observation for gravitational wave astronomy and obtain insight into significant areas science, such as verifying characterizing inflation, determining thermal history universe, dark energy, describing formation mechanism supermassive black holes in center galaxies, testing alternative theories gravity, seeking hole matter, understanding physics neutron stars searching planets...
Numerical-relativity simulations for the merger of binary neutron stars are performed a variety equations state (EOSs) and plausible range neutron-star mass, focusing primarily on properties material ejected from system. We find that fraction is as mildly relativistic anisotropic outflow with typical maximum velocities $\ensuremath{\sim}0.15--0.25c$ $\ensuremath{\sim}0.5--0.8c$ (where $c$ speed light), respectively, total rest mass in wide...
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational antenna. It aims at detecting various kinds of waves between 1 mHz and 100 Hz frequently enough to open a new window observation for astronomy. The pre-conceptual design DECIGO consists three drag-free satellites, 1000 km apart from each other, whose relative displacements are measured by Fabry–Perot Michelson interferometer. We plan launch in 2024 after long intense development...
Gravitational-wave observation together with a large number of electromagnetic observations shows that the source latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is merger binary neutron star. We attempt to interpret this observational event based on our results numerical-relativity simulations performed so far paying particular attention optical and infra-red observations. finally reach conclusion described consistently presence long-lived hypermassive or...
Recent studies suggest that binary neutron star (NS–NS) mergers robustly produce heavy r-process nuclei above the atomic mass number A ∼ 130 because their ejecta consist of almost pure neutrons (electron fraction Ye < 0.1). However, production a small amount lighter (A ≈ 90–120) conflicts with spectroscopic results r-process-enhanced Galactic halo stars. We present, for first time, result nucleosynthesis calculations based on fully general relativistic simulation NS–NS merger approximate...
Massive (hypermassive and supramassive) neutron stars are likely to be often formed after the merger of binary stars. We explore evolution process remnant massive gravitational waves emitted by them, based on numerical-relativity simulations for star mergers employing a variety equations state choosing plausible range neutron-star mass binaries. show that lifetime hypermassive depends strongly total also state. Gravitational universally have quasiperiodic nature an approximately constant...
We perform radiation-hydrodynamics simulations of binary neutron-star mergers in numerical relativity on the Japanese ``K'' supercomputer, taking into account neutrino cooling and heating by an updated leakage-plus-transfer scheme for first time. Neutron stars are modeled three modern finite-temperature equations state (EOS) developed Hempel his collaborators. find that properties dynamical ejecta merger such as total mass, average electron fraction, thermal energy depend strongly EOS. Only...
We perform neutrino radiation-hydrodynamics simulations for the merger of asymmetric binary neutron stars in numerical relativity. Neutron are modeled by soft and moderately stiff finite-temperature equations state (EOS). find that properties dynamical ejecta such as total mass, richness profile, specific entropy profile depend on mass ratio systems a given EOS unique manner. For (SFHo), depends weakly ratio, but average electron number per baryon (${Y}_{e}$) ($s$) decreases significantly...
We perform a numerical-relativity simulation for the merger of binary neutron stars with 6 nuclear-theory-based equations states (EOSs) described by piecewise polytropes. Our purpose is to explore dependence dynamical behavior star and resulting gravitational waveforms on EOS supernuclear-density matter. The numerical results show that process first outcome are classified into three types: (i) black hole promptly formed, (ii) short-lived hypermassive (HMNS) (iii) long-lived HMNS formed. type...
We revisit the constraint on maximum mass of cold spherical neutron stars coming from observational results GW170817. develop a new framework for analysis by employing both energy and angular momentum conservation laws as well solid latest numerical-relativity simulations in equilibrium. The shows that can be only weakly constrained ${M}_{\mathrm{max}}\ensuremath{\lesssim}2.3\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$. Our present result illustrates merger remnant star at onset collapse to...
Numerical simulations for the merger of binary neutron stars are performed in full general relativity incorporating a finite-temperature (Shen's) equation state (EOS) and neutrino cooling first time. It is found that this stiff EOS, hypermassive star (HMNS) with long lifetime ($\gg 10$ ms) outcome total mass $\alt 3.0M_{\odot}$. shown typical luminosity HMNS $\sim 3$--$8\times 10^{53}$ ergs/s effective amplitude gravitational waves from 4--$6 \times 10^{-22}$ at $f=2.1$--2.5 kHz source...
We perform long-term general relativistic neutrino radiation hydrodynamics simulations (in axisymmetry) for a massive neutron star (MNS) surrounded by torus, which is canonical remnant formed after the binary merger. take into account effects of viscosity, likely to arise in merger due magnetohydrodynamical turbulence. As initial condition, we employ azimuthally averaged data MNS-torus system derived three-dimensional, numerical-relativity simulation The viscous effect plays key roles...
This article reports on the results of novel, extremely high-resolution simulations general relativistic magnetohydrodynamics (MHD) neutron star mergers, focussing angular momentum transport due to MHD turbulence. The authors show that Kelvin-Helmholtz instability at merger amplifies magnetic energy $\ensuremath{\sim}1%$ thermal energy.
We perform high-resolution magnetohydrodynamics simulations of binary neutron star mergers in numerical relativity on the Japanese supercomputer K. The stars and merger remnants are covered by a grid spacing 70 m, which yields highest-resolution results among those derived so far. By an in-depth resolution study, we clarify several amplification mechanisms magnetic fields during for first time. First, Kelvin-Helmholtz instability developed shear layer at onset significantly amplifies fields....
We explore magnetic-field amplification due to the Kelvin-Helmholtz instability during binary neutron star mergers. By performing high-resolution general relativistic magnetohydrodynamics simulations with a resolution of $17.5$ m for $4$--$5$ ms after onset merger on Japanese supercomputer "K", we find that an initial magnetic field moderate maximum strength $10^{13}$ G is amplified at least by factor $\approx 10^3$. also saturation energy and our result shows it likely be $\gtrsim 4 \times...
DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational antenna, aiming to detect waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz 10 thus open a new window for astronomy universe. will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by differential Fabry-Perot interferometer, four units triangular...
Abstract By performing general relativistic hydrodynamics simulations with an approximate neutrino radiation transfer, the properties of ejecta in dynamical and post-merger phases are investigated cases which remnant massive neutron star collapses into a black hole ≲20 ms after onset merger. The mass ejection is three-dimensional simulations. two-dimensional axisymmetric viscosity using systems as initial conditions. We show that typical richness higher for merger more asymmetric binaries;...
Abstract The merger of two neutron stars launches a relativistic jet, which must be driven by strong large-scale magnetic field. However, the magnetohydrodynamical mechanism required to build up this field remains uncertain. By performing an ab initio super-high-resolution neutrino-radiation magnetohydrodynamics simulation in full general relativity, we show that αΩ dynamo mechanism, magnetorotational instability, builds inside long-lived remnant binary star merger. As result, induces...
A truncated moment formalism for general relativistic radiation hydrodynamics, based on the Thorne's formalism, is derived. The fluid rest frame chosen to be fiducial defining moments. Then, zeroth-, first-, and second-rank moments are defined from distribution function with a physically reasonable assumption it in optically thin thick limits. source terms written, focusing specifically neutrino transfer neglecting higher harmonic angular dependence of reaction angle. Finally, basic...
We report results of a high-resolution numerical-relativity simulation for the merger black hole-magnetized neutron star binaries on Japanese supercomputer "K". focus binary that is subject to tidal disruption and subsequent formation massive accretion torus. find launch thermally driven torus wind, funnel wall above magnetosphere with collimated poloidal magnetic field, high Blandford-Znajek luminosity. show first time this picture in self-consistent simulation. The turbulence-like motion...
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational antenna. DECIGO expected to open a new window of observation for astronomy especially between 0.1 Hz and 10 Hz, revealing various mysteries universe such as dark energy, formation mechanism supermassive black holes, inflation universe. The pre-conceptual design consists three drag-free spacecraft, whose relative displacements are measured by differential Fabry-Perot Michelson...
General relativistic simulations for the merger of binary neutron stars are performed as an extension a previous work [M. Shibata and K. Taniguchi, Phys. Rev. D 73, 064027 (2006).]. We prepare with large initial orbital separation employ moving-puncture formulation, which enables one to follow ringdown phases long time, even after black hole formation. For modeling inspiraling stars, should be composed cold Akmal-Pandharipande-Ravenhall (APR) equation state (EOS) is adopted. After onset...
Detection of the electromagnetic counterparts gravitational wave (GW) sources is important to unveil nature compact binary coalescences. We perform three-dimensional, time-dependent, multi-frequency radiative transfer simulations for radioactively powered emission from ejecta black hole (BH)–neutron star (NS) mergers. Depending on BH NS mass ratio, spin BH, and equations state dense matter, BH–NS mergers can eject more material than NS–NS In such cases, merger be luminous that show that, in...
We find, using high resolution numerical relativistic simulations, that the tail of dynamical ejecta neutron star mergers extends to mildly velocities faster than $0.7c$. The kinetic energy this fast is $\sim 10^{47}$--$10^{49}$ erg, depending on equation state and binary masses. synchrotron flare arising from interaction with surrounding ISM can power observed non-thermal emission followed GW170817, provided density 10^{-2}\,{\rm cm^{-3}}$, two stars had roughly equal masses soft (small...
An electromagnetic transient powered by the radioactive decay of r-process elements, a so-called kilonova/macronova, is one possible observable consequences compact binary mergers including at least neutron star. Recent observations strongly suggest discovery first transient, which associated with short gamma ray burst 130603B. We explore progenitor this event combining numerical-relativity simulations and radiative transfer dynamical ejecta star black hole–neutron mergers. show that models...