Takeshi Nakamori
A5034858253- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Particle Detector Development and Performance
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Radiation Detection and Scintillator Technologies
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Neutrino Physics Research
- Medical Imaging Techniques and Applications
- Particle Accelerators and Free-Electron Lasers
- Advanced X-ray and CT Imaging
- Atomic and Subatomic Physics Research
- Astronomical Observations and Instrumentation
- Particle physics theoretical and experimental studies
- Astronomy and Astrophysical Research
- Advanced Semiconductor Detectors and Materials
- Cosmology and Gravitation Theories
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
Yamagata University
2016-2025
The University of Tokyo
2018-2024
Universitat de Barcelona
2021-2024
Institut d'Estudis Espacials de Catalunya
2024
Waseda University
2009-2023
The Graduate University for Advanced Studies, SOKENDAI
2023
Nagoya University
2023
Centre National de la Recherche Scientifique
2019-2023
Kyoto University
2005-2023
RIKEN
2021-2023
We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because instrument does not have an onboard magnet, we distinguish two species by exploiting Earth's shadow, which is offset in opposite directions for charges due to magnetic field. estimate subtract proton background using different methods that produce consistent results. report electron-only spectrum, positron-only fraction between 20 GeV 200 GeV. confirm rises energy 20-100 range. The...
We present detailed analysis of two gamma-ray sources, 1FGL J1801.3−2322c and J1800.5−2359c, that have been found toward the supernova remnant (SNR) W28 with Large Area Telescope (LAT) on board Fermi Gamma-ray Space Telescope. is to be an extended source within boundary SNR W28, extensively overlap TeV HESS J1801−233, which associated a dense molecular cloud interacting SNR. The spectrum measured LAT from 0.2 100 GeV can described by broken power-law function break at ∼1 photon indices 2.09...
The flat spectrum radio quasar 3C~454.3 underwent an extraordinary outburst in December 2009 when it became the brightest gamma-ray source sky for over one week. Its daily flux measured with Fermi Large Area Telescope at photon energies E>100 MeV reached F = 22+/-1 x 10^-6 ph cm^-2 s^-1, representing highest of any blazar ever recorded high-energy gamma-rays. It again 2010 April, triggering a pointed-mode observation by Fermi. correlated temporal and spectral properties during these...
The Fermi Large Area Telescope (LAT) observed two bright X-class solar flares on 2012 March 7, and detected gamma-rays up to 4 GeV. We both during the impulsive temporally-extended emission phases, with above 100 MeV lasting for approximately 20 hours. Accurate localization of gamma-ray production site(s) coincide active region from which X-ray emissions associated these originated. Our analysis >100 shows a relatively rapid monotonic decrease in flux first hour phase, much slower, almost...
We report the detection of high-energy γ-rays from quiescent Sun with Large Area Telescope on board Fermi Gamma-Ray Space (Fermi) during first 18 months mission. These observations correspond to recent period low solar activity when emission induced by cosmic rays (CRs) is brightest. For time, high statistical significance allows clear separation two components: point-like disk due CR cascades in atmosphere and extended inverse Compton (IC) scattering electrons photons heliosphere. The...
We present Suzaku X-ray observations along two edge regions of the Fermi Bubbles, with eight ~20 ksec pointings across northern part North Polar Spur (NPS) surrounding north bubble and six southernmost south bubble. After removing compact features, diffuse emission is clearly detected well reproduced by a three-component spectral model consisting unabsorbed thermal (temperature kT ~0.1 keV from Local Bubble (LB), absorbed ~0.3 related to NPS and/or Galactic Halo (GH), power-law component at...
We are proposing a novel design for module with depth of interaction (DOI) capability gamma rays by measuring the pulse-height ratio double-sided Multi-Pixel Photon Counters (MPPCs) coupled at both ends scintillation crystal block. Thanks to newly developed monolithic MPPC arrays consisting 4 × channels three-side buttable package, is very thin and compact, thereby enabling less dead space between each when arranged into fully designed gantry. To demonstrate our concept DOI technique, we...
The flux of gamma rays with energies >100MeV is dominated by diffuse emission from CRs illuminating the ISM our Galaxy through processes Bremsstrahlung, pion production and decay, inverse-Compton scattering. study this provides insight into origin transport CRs. We searched for gamma-ray SMC in order to derive constraints on CR population an external system properties different Milky Way. analysed first 17 months continuous all-sky observations Large Area Telescope Fermi mission determine...
We report on a detailed investigation of the gamma-ray emission from 18 broad line radio galaxies (BLRGs) based two years Fermi Large Area Telescope (LAT) data. confirm previously reported detections 3C 120 and 111 in GeV photon energy range; look at temporal characteristics observed reveals addition possible flux variability both sources. No statistically significant detection other BLRGs was however found considered dataset. Though sample size studied is small, what appears to...
We present a detailed analysis of the GeV gamma-ray emission toward supernova remnant (SNR) G8.7−0.1 with Large Area Telescope (LAT) on board Fermi Gamma-ray Space Telescope. An investigation relationship between and TeV unidentified source HESS J1804−216 provides us an important clue diffusion process cosmic rays if particle acceleration operates in SNR. The is extended most positional coincidence SNR lesser part located outside western boundary G8.7−0.1. region overlaps spatially connected...
Abstract We have developed an optical photon-counting imaging system, IMONY, as instrument for short-scale time-domain astronomy. In this study, we utilized a Geiger avalanche photodiode array with $4\times 4$ pixel configuration, each measuring 100 µm. dedicated analog frontend board and constructed data acquisition system FPGA to time-stamp photon time resolution of ns. mounted prototype model the on 1.5 m Kanata telescope, intending observe Crab pulsar conduct joint observations Iitate...
We report on observations of BL Lacertae during the first 18 months Fermi-LAT science operations and present results from a 48-day multifrequency coordinated campaign 2008 August 19 to October 7. The radio gamma-ray behavior Lac is unveiled low activity state thanks radio-band (Metsahovi VLBA), near-IR/optical (Tuorla, Steward, OAGH MDM) X-ray (RXTE Swift) observatories. No variability was resolved in gamma-rays campaign, brightness level 15 times lower than 1997 EGRET outburst. Moderate...
The hard x-ray imaging spectroscopy system of "Hitomi" observatory is composed two sets imagers (HXI) coupled with telescopes (HXT). With a 12-m focal length, the provides fine (1 ′ . 7 half-power diameter) covering about 5 to 80 keV. HXI sensor consists camera, which four layers Si and one layer CdTe semiconductor imagers, an active shield nine Bi4Ge3O12 scintillators provide low background. HXIs started observation on March 8 14, 2016 were operational until 26 March. Using Crab...
We have detected gamma-ray emission at the 6sigma level energies greater than 500GeV from supernova remnant RX J0852.0-4622 (G266.2-1.2) using CANGAROO-II Imaging Atmospheric Cherenkov Telescope (IACT). The flux was 0.12 times of that Crab 1TeV. signal centroid is consistent with peak X-ray in north-west rim remnant.
The Large Area Telescope (LAT) instrument on the Fermi mission will reveal rich spectral and temporal gamma-ray burst (GRB) phenomena in >100 MeV band. synergy with Fermi's Gamma-ray Burst Monitor detectors link these observations to those well explored 10–1000 keV range; addition of band resolve theoretical uncertainties about emission both prompt afterglow phases. Trigger algorithms be applied LAT data onboard spacecraft ground. sensitivity triggers differ because available computing...
We report on the gamma-ray observations of giant molecular clouds Orion A and B with Large Area Telescope (LAT) on-board Fermi Gamma-ray Space Telescope. The emission in energy band between \sim100 MeV GeV is predicted to trace gas mass distribution through nuclear interactions Galactic cosmic rays (CRs) interstellar gas. production cross-section for interaction known \sim10% precision which makes LAT a powerful tool measure column density CR intensity. present here such distributions B,...
The Cute‐1.7+APD II, 10 × 15 20 cm 3 in size and 5 kg mass, is the third picosatellite developed by students at Tokyo Institute of Technology. One primary goals II mission to validate use avalanche photodiodes (APDs) as a radiation detector for first time space experiment. While itself immature compared forefront satellites plasma physics, APDs offers various possibilities regarding brand‐new electron energy analyzer medium‐energy electrons ions (1–100 keV), well high‐performance light...
We have analyzed all the archival X-ray data of 134 unidentified (unID) gammaray sources listed in first Fermi/LAT (1FGL) catalog and subsequently followed up by Swift/XRT. constructed spectral energy distributions (SEDs) from radio to gamma-rays for each source detected, tried pick unique objects that display anomalous signatures. In these analysis, we target 1FGL unID sources, using updated second (2FGL) on their LAT position spectra. found several potentially interesting objects,...
The Hard X-ray Imager (HXI) is one of the four detectors on board ASTRO-H mission (6th Japanese satellite), which scheduled to be launched in 2014. Using hybrid structure composed double-sided silicon strip and a cadmium telluride detector, both with high spatial resolution 250 μm. Combined hard telescope (HXT), it consists imaging spectroscopic instrument covering energy range from 5 80 keV an effective area <300 cm<sup>2</sup> total at 30 keV. An 1–2 (FWHM) lower threshold are...
We present the simultaneous Swift and Fermi observations of bright GRB100728A its afterglow. The early X-ray emission is dominated by a vigorous flaring activity continuing until 1 ks after burst. In same time interval high energy significantly detected Fermi/LAT. Marginal evidence GeV observed up to later times. discuss broadband properties this burst within both internal external shock scenarios, with particular emphasis on relation between flares, continued long-duration central engine as...