A5059767517- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Particle Detector Development and Performance
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Magnetic confinement fusion research
- Solar and Space Plasma Dynamics
- High-Energy Particle Collisions Research
- Photocathodes and Microchannel Plates
- Radiation Detection and Scintillator Technologies
- CCD and CMOS Imaging Sensors
- Calibration and Measurement Techniques
- Radiation Therapy and Dosimetry
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Atmospheric Ozone and Climate
- Ionosphere and magnetosphere dynamics
- Dust and Plasma Wave Phenomena
- History and Developments in Astronomy
National Astronomical Observatory of Japan
2021-2022
Tohoku University
2017
Hiroshima University
2011-2015
The second-order Fermi acceleration (Fermi-II) driven by turbulence may be responsible for the electron in blazar jets. We test this model with time-dependent simulations. hard spectrum predicted Fermi-II process agrees photon of 1ES 1101-232. For other blazars that show softer spectra, requires radial evolution injection rate and/or diffusion coefficient outflow. Such evolutions can yield a curved spectrum, which reproduce synchrotron Mrk 421 from radio to X-ray regime.The GeV energy range...
We discuss the prospects for detection of gamma-ray bursts (GRBs) by Cherenkov Telescope Array (CTA), next generation, ground-based facility imaging atmospheric telescopes (IACTs) operating above a few tens GeV. By virtue its fast slewing capabilities, lower energy threshold compared to current IACTs, and much larger effective area satellite instruments, CTA can measure spectra variability GRBs with excellent photon statistics at multi-GeV energies. Employing model GRB population whose...
We examine the applicability of stochastic electron acceleration to two high synchrotron peaked blazars, Mrk 421 and 501, assuming self-Compton emission gamma-rays. Our model considers an emitting region moving at relativistic speed, where non-thermal electrons are accelerated attain a steady-state energy spectrum together with photons they emit. The kinetic equations solved numerically, given stationary wavenumber magnetohydrodynamic (MHD) disturbances, which responsible for escape. simple...
Abstract We present a weak-lensing analysis for merging galaxy cluster, CIZA J2242.8+5301, which hosts double radio relics, using three-band Subaru/Suprime-Cam imaging (Br′z′). Since the lifetime of dark matter halos colliding into clusters is longer than that X-ray emitting gas halos, powerful method to constrain merger dynamics. Two-dimensional shear fitting clean background catalog suggests cluster undergoes with mass ratio about 2 : 1. The main halo located around core in southern...
Abstract This paper presents a novel formula to convert photographic density into intensity for historical plates of the Sun. Photographic photometry is great importance as very first step analyzing century-long archived data study long-term variation. The calibration newly developed by using fluctuation originating in network pattern quiet region, taking consideration nonlinearity between and intensity. useful especially when experimentally obtained characteristic curves are insufficient...
ABSTRACT Stochastic acceleration of nonthermal electrons is investigated in the context hard photon spectra blazars. It well known that this mechanism can produce a electron spectrum <?CDATA $m\equiv \partial \mathrm{ln}{n}_{{\rm{e}}}(\gamma )/\partial \mathrm{ln}\gamma =2$?> <?MML <mml:math> <mml:mi>m</mml:mi> <mml:mo>≡</mml:mo> <mml:mo>∂</mml:mo> <mml:mi>ln</mml:mi> <mml:msub> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:msub>...
Analytical forms of dispersion relations for three lower-frequency waves in a two-fluid plasma are presented. In underdense plasmas, ωp2≲Ωce2, that is, low density or strongly magnetized where ωp and Ωce respectively the frequency electron cyclotron frequency, displacement current can become important higher-frequency (non-magnetohydrodynamic) region. Focusing on only branches magnetohydrodynamic low-frequency limit, we derive applicable to both overdense plasmas by full set equations...
Abstract Reconstruction of long-term solar UV variations during the entire 20th century is reported. The sunspot number has been used for this purpose so far. By using full-disk Ca K intensity as an additional proxy, range allowed values reconstructed irradiance becomes more restricted. We use archival data photographic plates digitized at Kodaikanal Solar Observatory. calibration method developed in our previous paper (Paper I) applied. Various proxy activity have to estimate past...