S. Kobayashi
A5065916463- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Methane Hydrates and Related Phenomena
- Cosmology and Gravitation Theories
- Nuclear Physics and Applications
- Isotope Analysis in Ecology
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Marine and coastal ecosystems
- Geomagnetism and Paleomagnetism Studies
- Statistical and numerical algorithms
- Nutrition and Health in Aging
- Gastric Cancer Management and Outcomes
- Marine and fisheries research
- Porphyrin and Phthalocyanine Chemistry
- Laser-Plasma Interactions and Diagnostics
Liverpool John Moores University
2015-2024
Toranomon Hospital
2024
Kitasato University
2024
Sumitomo Electric Industries (Japan)
2024
Tohoku University
2023
Saitama Cancer Center
2017
University of Utah
2010-2017
University of Leicester
2005-2015
University of North Carolina at Charlotte
2007-2014
Hebrew University of Jerusalem
1997-2014
(Abridged) The Swift X-Ray Telescope (XRT) reveals some interesting features of early X-ray afterglows, including a distinct rapidly decaying component preceding the conventional afterglow in many sources, shallow decay before more ``normal'' observed good fraction GRBs (e.g. GRB 050128, 050315, 050319, and 050401), flares nearly half afterglows 050406, 050502B, 050607, 050724). In this paper, we systematically analyze possible physical processes that shape properties lightcurves, use data...
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...
We discuss the possibility that gamma-ray bursts result from internal shocks in an ultra-relativistic matter. Using a simple model we calculate temporal structure and estimate efficiency of this process. In matter flow is represented by succession shells with random values Lorentz factor. take place between those resulting emission. Internal can produce highly variable observed most provided source emitting relativistic variable. The peaks are almost one to correlation activity source. A...
Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on nearby environment and indirect central engine that powers burst. We report discovery two bright x-ray flares in GRB afterglows, including a giant flare comparable total energy itself, each peaking minutes after These strong, rapid imply engines bursts long periods activity, with strong internal shocks continuing for hundreds seconds gamma-ray...
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...
Abstract The Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future Japanese space mission with frequency band of 0.1 Hz to 10 Hz. DECIGO aims at the detection primordial gravitational waves, which could have been produced during inflationary period right after birth Universe. There are many other scientific objectives DECIGO, including direct measurement acceleration expansion Universe, and reliable accurate predictions timing locations neutron star/black hole binary...
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...
GRB 221009A ($z=0.151$) is one of the closest known long $\gamma$-ray bursts (GRBs). Its extreme brightness across all electromagnetic wavelengths provides an unprecedented opportunity to study a member this still-mysterious class transients in exquisite detail. We present multi-wavelength observations extraordinary event, spanning 15 orders magnitude photon energy from radio $\gamma$-rays. find that data can be partially explained by forward shock (FS) highly-collimated relativistic jet...
We present observations of the early X-ray emission for a sample 40 gamma-ray bursts (GRBs) obtained using Swift satellite which narrow-field instruments were pointed at burst within 10 minutes trigger. Using data from Burst Alert and X-Ray Telescopes, we show that light curve can be well described by an exponential relaxes into power law, often with flares superimposed. The transition time between law provides physically defined timescale duration. In most breaks to shallower decay first...
The standard model of GRB afterglows assumes that relativistically expanding material is decelerating due to interaction with the surrounding medium. are well described by synchrotron radiation from a forward shock, while strong optical flash associated 990123 can be attributed emission reverse shock. We give detailed study on shock emission. full light curves calculated for long and short cases. discuss lack prompt detections ROTSE 981121 981223.
We systematically analyze the prompt emission and early afterglow data of a sample 31 GRBs detected by {\em Swift} before September 2005, estimate GRB radiative efficiency. BAT's narrow band inhibits precise determination spectral parameters, we have developed method to these parameters with hardness ratio information. The shallow decay component commonly existing in X-ray afterglows, if interpreted as continuous energy injection external shock, suggests that efficiency previously derived...
Evidence suggests that the gamma-ray burst (GRB) ejecta is likely magnetized, although degree of magnetization unknown. We derive a rigorous analytical solution for relativistic 90 shocks under ideal MHD condition, and use them to study reverse shock emission properties an arbitrarily magnetized ejecta. Contrary previous belief, we find strong still exist in high-sigma limit. Assuming constant density circumburst medium, shell-medium interaction detail categorize various critical radii shell...
Early optical afterglows have been observed from GRB 990123, 021004, and 021211, which reveal rich emission features attributed to reverse shocks. It is expected that Swift will discover many more early afterglows. Here we investigate in a unified manner both the forward external shock components, introduce straightforward recipe for directly constraining initial Lorentz factor of fireball using afterglow data. The scheme largely independent microphysics. We identify two types combinations...
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...
We show the peak magnitude for orphan afterglows from jets of gravitational wave (GW) detected black-hole/neutron star - neutron (BH/NS-NS) mergers highly depends on jet half-opening angle $\theta_j$. Short $\gamma$-ray bursts (GRB) with a homogeneous structure and $\theta_j>10^\circ$, afterglow viewed at typical inclination GW event, 38$^\circ$, is brighter optical frequencies than comparable macronova emission. Structured jets, where energetics Lorentz factor $\Gamma$ vary central axis,...
Long-duration Gamma-Ray Bursts (GRBs) are an extremely rare outcome of the collapse massive stars, and typically found in distant Universe. Because its intrinsic luminosity ($L\sim 3 \times 10^{53}$ erg s$^{-1}$) relative proximity ($z=0.34$), GRB 130427A was a unique event that reached highest fluence observed gamma-ray band. Here we present comprehensive multiwavelength view with Swift, 2-m Liverpool Faulkes telescopes by other ground-based facilities, highlighting evolution burst emission...
Fermi/GBM (Gamma-ray Burst Monitor) and INTEGRAL (the International Gamma-ray Astrophysics Laboratory) reported the detection of γ-ray counterpart, GRB 170817A, to LIGO (Light Interferometer Gravitational-wave Observatory)/Virgo gravitational wave detected binary neutron star merger, GW 170817. 170817A is likely have an internal jet or another origin such as cocoon emission, shock-breakout, a flare from viscous disc. In this paper we assume that emission caused by energy dissipation within...
DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a future Japanese space gravitational-wave antenna. The most important objective of DECIGO, among various sciences to be aimed at, detect gravitational waves coming from the inflation universe. DECIGO consists four clusters spacecraft, and each cluster three spacecraft with Fabry–Perot Michelson interferometers. As pathfinder mission B-DECIGO will launched, hopefully in 2020s, demonstrate technologies necessary for as well...