A5075974049- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- High-Energy Particle Collisions Research
- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Astrophysics and Star Formation Studies
- Cosmology and Gravitation Theories
- Computational Fluid Dynamics and Aerodynamics
- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- Heat Transfer Mechanisms
- Neutrino Physics Research
- Powder Metallurgy Techniques and Materials
- Superconducting Materials and Applications
- Risk and Safety Analysis
- Stress and Burnout Research
- Economic theories and models
- Metallurgy and Material Forming
- Workplace Health and Well-being
- Geophysics and Gravity Measurements
- Workaholism, burnout, and well-being
Komazawa University
2019-2025
Tokyo City University
2022
Chubu University
2019
National Astronomical Observatory of Japan
2010-2018
National Institutes of Natural Sciences
2017-2018
Ogikubo Hospital
2015
Kobe University
2010
Kyoto University
2010
Chiba University
2000-2009
National Institute of Advanced Industrial Science and Technology
2009
Using two-dimensional radiation hydrodynamic simulations, we investigate origin of the ultra fast outflows (UFOs) that are often observed in luminous active galactic nuclei (AGNs). We found force due to spectral lines generates strong winds (line-driven disk winds) launched from inner region accretion disks (~30 Schwarzschild radii). A wide range black hole masses ($M_{\rm BH}$) and Eddington ratios ($\varepsilon$) was investigated study conditions for causing line-driven winds. For $M_{\rm...
We present a new magnetohydrodynamic (MHD) simulation code with the aim of providing accurate numerical solutions to astrophysical phenomena where discontinuities, shock waves, and turbulence are inherently important. The implements HLLD approximate Riemann solver, fifth-order-monotonicity-preserving interpolation (MP5) scheme, hyperbolic divergence cleaning method for magnetic field. This choice schemes significantly improved accuracy stability, saved computational costs in multidimensional...
The impact of the magnetic field on postbounce supernova dynamics non-rotating stellar cores is studied by performing three-dimensional magnetohydrodynamics simulations with spectral neutrino transport. explodability strongly and weakly magnetized models $20$ $27$ $M_{\odot}$ pre-supernova progenitors are compared. We find that although efficiency for conversion heating into turbulent energy including fields in gain region not significantly different between strong weak models, amplified due...
We perform two-dimensional radiation hydrodynamical simulations of accretion flows onto a black hole (BH) with mass $10^3\leq M_{\rm BH}/M_{\odot} \lesssim 10^6$ in order to study rapid growth BHs the early Universe. For spherically symmetric flows, hyper-Eddington BH from outside Bondi radius can occur unimpeded by feedback only when is higher than $\simeq 10^4~M_{\odot}(n_\infty/10^5~{\rm cm}^{-3})^{-1}(T_\infty/10^4~{\rm K})^{3/2}$, where $n_\infty$ and $T_\infty$ are density temperature...
Abstract We perform global three-dimensional (3D) radiation-hydrodynamic (RHD) simulations of outflow from supercritical accretion flow around a 10 M⊙ black hole. only solve the part, starting axisymmetric 2D simulation data in nearly steady state but with small perturbations sinusoidal form being added azimuthal direction. The mass rate onto hole is ∼102LE/c2 underlying data, and ∼10 LE/c2 (with LE c Eddington luminosity speed light, respectively). first confirm emergence clumpy outflow,...
ABSTRACT Using three-dimensional general relativistic radiation-magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk ( <?CDATA $\gtrsim {10}^{7}\;{\rm{K}}$?> ) is truncated near hole. Hot and less dense regions, which gas temperature {10}^{9}\;{\rm{K}}$?> more than 10 times higher radiation (overheated regions), appear within truncation radius. The overheated regions also above as well below disk, sandwiching leading to...
Abstract By performing 2.5-dimensional general relativistic radiation magnetohydrodynamic simulations, we demonstrate supercritical accretion onto a non-rotating, magnetized neutron star, where the magnetic field strength of dipole fields is 10 G on star surface. We found flow consists two parts: columns and truncated disk. The disk, which appears far from at around ≃3 R * ( = 6 cm radius), pressure via balances with disks. angular momentum disk truncation radius effectively transported...
Abstract We construct a relativistic resistive magneto-hydrodynamic (RRMHD) numerical simulation code for high-energy heavy-ion collisions as first designed in the Milne coordinates. split system of differential equations into two parts, non-stiff and stiff part. For part, we evaluate flux using HLL approximated Riemann solver execute time integration by second-order Runge–Kutta algorithm. which appears Ampere’s law, integrate semi-analytic solutions electric field. employ generalized...
Charge dependent directed flow is an important observable of electromagnetic fields in relativistic heavy-ion collisions. We demonstrate how the difference charge flows between protons and antiprotons sensitive to resistivity, inverse quark-gluon plasma's electric conductivity, over different collision centralities. Our model numerically solves 3+1D resistive magneto-hydrodynamic (RRMHD) equations, assuming conductivity be a scalar. For this work, we focus on symmetric Au + collisions at top...
We develop a numerical scheme for solving fully special relativistic, resistive radiation magnetohydrodynamics. Our code guarantees conservation of total mass, momentum, and energy. The energy density the flux are consistently updated using M-1 closure method, which can resolve an anisotropic field, in contrast to Eddington approximation, as well flux-limited diffusion approximation. For part, we adopt simple form Ohm's law. advection terms explicitly solved with approximate Riemann solver,...
We study the effects of magnetic field on dynamics non-rotating stellar cores by performing two-dimensional (2D), magnetohydrodynamics (MHD) simulations. To this end, we have updated our neutrino-radiation-hydrodynamics supernova code to include MHD employing a divergence cleaning method with both careful treatments finite volume and area reconstructions. By changing initial strength field, evolution $15.0$, $18.4$ $27.0$ $M_\odot$ presupernova progenitors is investigated. An intriguing...
ABSTRACT We develop a numerical scheme for solving the equations of fully special relativistic, radiation magnetohydrodynamics (MHDs), in which frequency-integrated, time-dependent transfer equation is solved to calculate specific intensity. The energy density, flux, and stress tensor are obtained by angular quadrature In present method, conservation total mass, momentum, magnetofluids guaranteed. treat not only isotropic scattering but also Thomson scattering. method MHDs same as that our...
Abstract We investigate the properties of accretion flows on to a black hole (BH) with mass MBH embedded in an initially uniform gas cloud density n∞ order study rapid growth BHs early Universe. In previous work, conditions required for super-Eddington from outside Bondi radius were studied by assuming that radiation produced at vicinity central BH has single power-law spectrum ν−α $h\nu \ge 13.6\, {\rm eV}$ (α ∼ 1.5). However, spectra surely depend and rate, determine efficiency radiative...
We construct a dynamical model for high-energy heavy-ion collisions based on the relativistic resistive magneto-hydrodynamic framework. Using our newly developed ($3+1$)-dimensional magneto-hydrodynamics code, we investigate expansion in symmetric and asymmetric collision systems as first application to collisions. As realistic initial condition electromagnetic fields, consider solutions of Maxwell equations with source term point charged particles moving direction beam axis, including...
We have investigated the charge-dependent anisotropic flow in high-energy heavy-ion collisions, using relativistic resistive magneto-hydrodynamics (RRMHD). consider optical Glauber model as an initial of quark-gluon plasma (QGP) and solution Maxwell equations with source term charged particles two colliding nuclei electromagnetic fields. The RRMHD simulation is performed these conditions Au-Au Cu-Au collisions at $\sqrt{{s}_{NN}}=200$ GeV. calculated charge-odd contribution to directed...
We present a general relativistic, ray-tracing radiative transfer code RAIKOU for multi-wavlength studies of spectra and images including the black hole shadows around Kerr holes. Important processes in hot plasmas holes, i.e., (cyclo-)synchrotron, bremsstrahlung emission/absorption Compton/inverse-Compton scattering, are incorporated. The Maxwell-J\"uttner single/broken power-law electron distribution functions implemented to calculate via both thermal nonthermal electrons. Two calculation...
Abstract We perform general relativistic radiation magnetohydrodynamics simulations of super-Eddington accretion flows around a neutron star with dipole magnetic field for modeling the Galactic ultraluminous X-ray source exhibiting pulsations, Swift J0243.6+6124. Our show columns near poles, disk outside magnetosphere, and outflows from disk. It is revealed that effectively optically thick outflows, consistent observed thermal emission at ∼10 7 K, are generated if mass rate much higher than...
We propose an explicit-implicit scheme for numerically solving Special Relativistic Radiation Hydrodynamic (RRHD) equations, which ensures a conservation of total energy and momentum (matter radiation). In our scheme, 0th 1st moment equations the radiation transfer equation are solved without employing flux-limited diffusion (FLD) approximation. For hyperbolic term, time scale is light crossing when flow velocity comparable to speed light, explicitly using approximate Riemann solver. Source...
Abstract By performing two-dimensional axisymmetric general relativistic radiation magnetohydrodynamics simulations with spin parameter a * varying from −0.9 to 0.9, we investigate the dependence on black hole of energy flow supercritical accretion disk around stellar mass hole. It is found that optically and geometrically thick disks form near equatorial plane, part matter launched surface in all models. The gas ejection mainly driven by radiative force, but magnetic force cannot be...
Relativistic Sweet–Parker-type magnetic reconnection is investigated by relativistic resistive magnetohydrodynamic (RRMHD) simulations. As an initial setting, we assume anti-parallel fields and a spatially uniform resistivity. A perturbation imposed on the triggers around current sheet, plasma inflows into region. The are then heated due to ohmic dissipation in diffusion region finally become relativistically hot outflows. outflows not accelerated ultrarelativistic speeds (i.e., Lorentz...
By performing 2.5-dimensional special relativistic radiation magnetohydrodynamics simulations, we study the super-critical accretion disks and outflows launched via force. We find that outflow is accelerated by flux force, but drag force prevents velocity from increasing. The saturates around 30-40% of light speed rotation axis, since then balances with Our simulations show kept nearly constant in regime \dot{M}_{BH} ~ 100-1000 L_{Edd}/c^2, where mass rate, L_{Edd} Eddington luminosity, c...
Abstract We develop a general relativistic radiation magnetohydrodynamics (GR-RMHD) code inazuma in which the time-dependent transfer equation (frequency-integrated Boltzmann equation) is solved curved spacetime. The Eddington tensor derived from specific intensity, and we solve zeroth first moment equations order to update fields. Therefore, our can field around compact objects more appropriately than an approximation method like M1 closure scheme. numerical scheme of same as that previous...