A5048510105- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Astrophysical Phenomena and Observations
- Ionosphere and magnetosphere dynamics
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Laser-Plasma Interactions and Diagnostics
- Galaxies: Formation, Evolution, Phenomena
- Laser-induced spectroscopy and plasma
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Lightning and Electromagnetic Phenomena
- Surface and Thin Film Phenomena
- Magnetic confinement fusion research
- Astro and Planetary Science
- Atomic and Molecular Physics
- Graphene research and applications
- Particle Accelerators and Free-Electron Lasers
- Fluid Dynamics and Turbulent Flows
- Fluorine in Organic Chemistry
- Geophysics and Gravity Measurements
- Per- and polyfluoroalkyl substances research
The University of Tokyo
2018-2025
Planetary Science Institute
2019-2025
Saitama University
2019-2023
Aoyama Gakuin University
2012-2023
Center for Astrophysics Harvard & Smithsonian
2012-2023
Konan University
2023
Osaka University
2007-2023
Kyoto University
2021-2023
Obayashi (Japan)
2023
Nagoya University
2008-2023
Recently, the gamma-ray telescopes AGILE and Fermi observed several middle-aged supernova remnants (SNRs) interacting with molecular clouds. It is likely that their gamma-rays arise from decay of neutral pions produced by inelastic collision between cosmic rays (CRs) nucleons, which suggests SNRs make bulk Galactic CRs. In this paper, we provide analytical solution distribution CRs have escaped a finite-size region, naturally explains broken power-law spectra SNRs. addition, typical value...
ABSTRACT Recently gamma-ray bursts (GRBs) have been detected at very-high-energy (VHE) gamma-rays by imaging atmospheric Cherenkov telescopes, and a two-component jet model has often invoked to explain multiwavelength data. In this work, afterglow emission from an extremely bright GRB, GRB 221009A, is examined. The isotropic-equivalent energy of event among the largest, which suggests that similarly previous VHE GRBs, opening angle so small collimation-corrected nominal. Afterglow such...
Recent observations by the CREAM and ATIC-2 experiments suggest that (1) spectrum of cosmic-ray (CR) helium is harder than CR protons below knee energy, 1015eV, (2) all spectra become hard at ≳1011eV nucleon−1. We propose a new idea, higher energy CRs are generated in more helium-rich region, to explain hardening without introducing different sources for helium. The helium-to-proton ratio ∼100 TeV exceeds Big Bang abundance Y = 0.25 several times, not reproduced within diffusive shock...
We study cosmic-ray acceleration in a supernova remnant (SNR) and the escape from it. model nonthermal particle photon spectra for hidden SNR open cluster Westerlund 2, old-age mixed-morphology W 28. assume that shock propagates low-density cavity, which is created heated through activities of progenitor stars and/or previous explosions. indicate diffusion coefficient cosmic-rays around SNRs less than ~1% away them. compare our predictions with gamma-ray molecular clouds illuminated by...
The spectrum of cosmic rays (CRs) is affected by their escape from an acceleration site. This may have been observed not only in the gamma-ray young supernova remnants (SNRs) such as RX J1713.7-3946, but also CRs showering on Earth. escape-limited model cosmic-ray studied general. We discuss running away constrain spectral index at site and ansatz with respect to unknown injection process into particle acceleration. apply our CR SNRs active galactic nuclei (AGN), which are plausible...
It has been suggested by radio observations of polarized synchrotron emissions that downstream magnetic field in some young supernova remnants are oriented radially. We study distribution turbulent remnant driven the Richtmyer-Meshkov instability -- other words, effect rippled shock using three-dimensional magnetohydrodynamics simulations. find induced turbulence radially biased anisotropic velocity dispersion leads to a selective amplification radial component field. The is interaction...
We report the first detection of thermal X-ray line emission from supernova remnant (SNR) RX J1713.7-3946, prototype small class synchrotron-dominated SNRs. A softness-ratio map generated using XMM-Newton data shows that faint interior regions are softer than bright shell regions. Using Suzaku and deep observations, we have extracted spectra softest area, finding clear features at 1 ∼1.35 keV. These lines can be best explained as Ne Lyα Mg Heα a component. Since abundance ratios metals to Fe...
In supernova remnants, the nonlinear amplification of magnetic fields upstream collisionless shocks is essential for acceleration cosmic rays to energy "knee" at 1015.5 eV. A nonresonant instability driven by ray current thought be responsible this effect. We perform two-dimensional, particle-in-cell simulations instability. observe an initial growth circularly polarized nonpropagating waves as predicted in linear theory. It demonstrated that some cases density growing can grow least 10...
H-alpha emission from supernova remnants (SNRs) implies the existence of neutral hydrogen in circumstellar medium. Some particles penetrating shock are ionized by charge exchange process and make a cold ion beam downstream region. We perform linear analyses collisionless plasma instabilities between hot plasma. find that, under typical SNR conditions, either resonant instability or Weibel is most unstable. This mechanism may amplify magnetic field to more than 100 micro G changes structure....
Recent precise observations of cosmic rays (CRs) by AMS-02 experiment clearly show (1) harder spectra helium and carbon compared to protons $\propto R^{0.08}$, (2) concave breaks in proton at a rigidity $R \sim 300$ GV. In particular the are exactly similar, pointing same acceleration site. We examine possible interpretations these features identify chemically enriched region, that is, superbubbles as most probable origin Galactic CRs high $R>30$ The similar CR further suggest with GV...
After a successful kick-off meeting in 2021. two workshops 2022 and 2023 on the future Global Cosmic-Ray Observatory (GCOS) focused mainly straw man design of detector science possibilities for astro- particle physics. About 100 participants gathered in-person hybrid panel discussions. In this report, we summarize these discussions, present preliminary straw-man GCOS collect short write-ups flash talks given during focus sessions.
Abstract Particle acceleration from collisionless shocks is a key mechanism in the generation of cosmic rays. In particular, young supernova remnants (SNRs) are considered to be major source galactic This study investigates early-stage plasma instability evolution and subsequent electron ion heating foot region high-Mach-number perpendicular SNRs, using 2D particle-in-cell simulations. Unlike previous simulations that cover larger regions shock structure—including downstream, shock, upstream...
Abstract Three-dimensional special relativistic magnetohydrodynamic simulations are performed to investigate properties of the downstream turbulence generated by interaction between a shock wave and multiple clumps. We analyze performing Helmholtz decomposition. It is shown that, in contrast non-relativistic case, amplitude compressive modes comparable that solenoidal for shock. In addition, many reflected shocks propagate region. The strength mode, waves, amplified magnetic field depend on...
An extreme case of electron shock drift acceleration (SDA) in low Mach number collisionless shocks is investigated as a plausible mechanism for the initial relativistic electrons large-scale galaxy clusters, where upstream plasma temperature order 10 keV and degree magnetization not too small. One-dimensional electromagnetic full particle simulations reveal that, even when rather moderate, part thermal incoming are accelerated reflected through SDA form local non-thermal population just...
We investigate escape of cosmic ray (CR) electrons from a supernova remnant (SNR) to interstellar space. show that CR in order high energies low like nuclei, while the starts later than beginning Sedov phase at an SNR age 10^3 - 7*10^3 yrs and maximum energy runaway is below knee about 0.3 50 TeV because unlike lose their due synchrotron radiation. Highest will be directly probed by AMS-02, CALET, CTA LHAASO experiments, or have been already detected H.E.S.S. MAGIC as cutoff electron...
In this study, we treat the Fermi bubbles as a scaled-up version of supernova remnants (SNRs). The are created through activities super-massive black hole (SMBH) or starbursts at Galactic center (GC). Cosmic-rays (CRs) accelerated forward shocks like SNRs, which means that cannot decide whether were by SMBH from radiation CRs. We follow evolution CR distribution solving diffusion-advection equation, considering reduction diffusion coefficient streaming. model, gamma-rays hadronic interaction...
The Fermi Gamma-ray Burst Monitor reported the possible detection of gamma-ray counterpart a binary black hole merger event, GW150914. We show that emission is caused by relativistic outflow with Lorentz factor larger than 10. Subsequently, debris pushes ambient gas to form shock, which responsible for afterglow synchrotron emission. find 1.4 GHz radio flux peaks at $\sim10^5$ sec after burst trigger. If matter dense enough density $\sim10^{-2}$ cm$^{-3}$, then peak $\sim0.1$ mJy, detectable...
Abstract Supernova remnants (SNRs) are the primary candidate of Galactic cosmic-ray accelerators. It is still an open issue when and how young SNRs, which typically exhibit strong synchrotron X-rays GeV TeV gamma rays, undergo state transition to middle-aged SNRs dominated by thermal rays. SNR N132D in Large Magellanic Cloud ideal target study such a transition, exhibiting bright with expected age ∼2500 years. In this paper we present results NuSTAR Suzaku spectroscopy. We reveal that has...
ABSTRACT Recently, ground-based Imaging Atmospheric Cherenkov Telescopes have reported the detection of very-high-energy (VHE) gamma-rays from some gamma-ray bursts (GRBs). One them, GRB 190829A, was triggered by Swift satellite, and about 2 × 104 s after burst onset VHE emission detected H.E.S.S. with ∼5σ significance. This event had unusual features having much smaller isotropic equivalent energy than typical long GRBs achromatic peaks in X-ray optical afterglow at 1.4 103 s. Here, we...
We study the escape of cosmic-ray protons accelerated at a supernova remnant (SNR). are interested in their propagation interstellar medium (ISM) after they leave shock neighborhood where accelerated, but when still near SNR with energy density higher than that average ISM. Using Monte Carlo simulations, we found cosmic rays energies ≲ TeV excite Alfvén waves around on scale itself if ISM is highly ionized. Thus, even can shock, scattering by prevents them from moving further away SNR. The...
It has been proposed that the cool cores of galaxy clusters are stably heated by cosmic rays (CRs). If this is case, radio mini-halos, which often found in central regions core clusters, may be attributed to synchrotron emission from CRs. Based on idea, we investigate radial profiles mini-halos. First, using numerical simulations, confirm it appropriate assume radiative cooling intracluster medium (ICM) balanced with heating CR streaming. In these streaming velocity CRs sound ICM, and...
In this paper, we investigate effects of neutral particles on shocks propagating into the partially ionized medium. We find that for 120 km s−1 < ush 3000 (ush is shock velocity), about 10% upstream leak region from downstream region. Moreover, how leakage affect structure and particle accelerations. Using four-fluid approximations (upstream ions, particles, pickup ions), provide analytical solutions precursor due to particles. It shown flow decelerated in compression ratio becomes smaller...
We study non-thermal emissions from cool cores in galaxy clusters. adopted a recent model, which cosmic-rays (CRs) prevail the and stably heat them through CR streaming. The come interaction between protons intracluster medium (ICM). Comparison theoretical predictions radio observations shows that overall spectra must be steep, most of CRs are low-energy CRs. Assuming injected AGN activities, we nature shocks responsible for acceleration. steep likely to reflect fact travel hot ICM with...
We propose that cosmic-ray PeVatrons are pulsar wind nebulae (PWNe) inside supernova remnants (SNRs). The PWN initially expands into the freely expanding stellar ejecta. Then, catches up with shocked region of SNR, where particles can be slightly accelerated by back and forth motion between some diffuse PWN. Afterwards is compressed in adiabatic compression. Using a Monte Carlo simulation, we show SNR to 0.1 PeV reaccelerated 1 until end