K. Yamaoka
A5045431767- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- SAS software applications and methods
- Pulsars and Gravitational Waves Research
- Particle Detector Development and Performance
- Astrophysics and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Astronomy and Astrophysical Research
- Nuclear Physics and Applications
- Statistical and numerical algorithms
- Dark Matter and Cosmic Phenomena
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Radiation Detection and Scintillator Technologies
- Advanced X-ray and CT Imaging
- Mechanics and Biomechanics Studies
- High-pressure geophysics and materials
- Calibration and Measurement Techniques
- Radiation Therapy and Dosimetry
- Atomic and Subatomic Physics Research
- Medical Imaging Techniques and Applications
- Advanced Semiconductor Detectors and Materials
- Advanced X-ray Imaging Techniques
Nagoya University
2016-2025
University of Miyazaki
2007-2024
Kyoto University
2010-2024
Institute of Space and Astronautical Science
1999-2024
Japan Aerospace Exploration Agency
2004-2024
University of Maryland, Baltimore County
2024
Tohoku University
2024
Tokyo University of Science
2024
European Space Research and Technology Centre
2024
Kanazawa University
2008-2024
The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 by combination of silicon PIN diodes and GSO scintillators. HXD is designed achieve an extremely low in-orbit back ground based new techniques, including the concept well-type active shield counter. With effective area 142 cm^2 at 20 273 cm2 150 keV, background level sea reached ~1x10^{-5} cts s^{-1} cm^{-2} keV^{-1} 30 for PI N diodes, ~2x10^{-5} 100 ~7x10^{-6} 200 phoswich Tight shielding results in...
The MAXI (Monitor of All-sky X-ray Image) mission is the first astronomical payload to be installed on Japanese Experiment Module-Exposed Facility (JEM-EF) ISS. It scheduled for launch in middle 2009 monitor all-sky objects every ISS orbit. will more powerful than any previous All Sky Monitor (ASM) payloads, being able hundreds AGN. provide all sky images sources about 20 mCrab energy band 2-30 keV from observation one orbit (90 min), 4.5 day, and 1 month. A final detectability could 0.2 2...
Abstract The in-orbit performance and calibration of the Hard X-ray Detector (HXD) on board astronomy satellite Suzaku are described. Its basic performances, including a wide energy bandpass 10–600 keV, resolutions $\sim 4 \,\mathrm{keV}$ (FWHM) at 40 keV 11\%$ 511 high background rejection efficiency, have been confirmed by extensive calibrations. long-term gains PIN-Si diodes stable within 1% for half year, those scintillators decreased 5–20%. residual non-X-ray HXD is lowest among past...
Extended results on the cosmic-ray electron $+$ positron spectrum from 11 GeV to 4.8 TeV are presented based observations with Calorimetric Electron Telescope (CALET) International Space Station utilizing data up November 2017. The analysis uses full detector acceptance at high energies, approximately doubling statistics compared previous result. CALET is an all-calorimetric instrument a total thickness of 30 ${X}_{0}$ normal incidence and fine imaging capability, designed achieve large...
In this paper, we present the analysis and results of a direct measurement cosmic-ray proton spectrum with CALET instrument onboard International Space Station, including detailed assessment systematic uncertainties. The observation period used in is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved very wide energy range necessary carry out measurements 50 GeV 10 TeV covering, for first time space, single whole interval previously investigated most cases separate...
Studies were made of ASCA spectra seven ultraluminous compact X-ray sources in nearby spiral galaxies: M33 X-8, M81 X-6, IC 342 source 1, Dwingeloo 1 X-1, NGC 1313 B, and two 4565. With the 0.5-10 keV luminosities range 1039-1040 ergs s-1, they are thought to represent a class enigmatic often found galaxies. For some them, data newly processed or published reanalyzed. others, results quoted. The all have been described successfully with so-called multicolor disk blackbody emission arising...
We report on the result of an X-ray observation Nova Velorum 1993 (GRS 1009–45), made with ASCA November 10-11. The energy spectrum was extremely soft and accompanied by a hard tail, characteristics Galactic black-hole binaries in state. It is well represented two-component model consisting multicolor disk or general relativistic accretion model, both describing emission from optically thick disk, power-law component photon index ∼ 2.5. A spectral analysis allows estimation mass central...
Abstract Suzaku Hard X-ray Detector (HXD) achieved the lowest background level than any other previously or currently operational missions sensitive in energy range of 10–600 keV, by utilizing PIN photodiodes and GSO scintillators mounted BGO active shields to reject particle Compton-scattered events as much possible. Because it does not have an imaging capability nor rocking mode for monitor, sensitivity is limited reproducibility non (NXB) model. We modeled HXD NXB, which varies with time...
First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on International Space Station starting in October, 2015. Nearly half million events are included analysis. an all-calorimetric total vertical thickness 30 ${X}_{0}$ fine imaging capability designed achieve large proton rejection excellent energy resolution well into region. The observed over can be fit single power law spectral index...
Abstract The Gas Slit Camera (GSC) is an X-ray instrument on the MAXI (Monitor of All-sky Image) mission aboard International Space Station. It designed to scan entire sky every 92-minute orbital period in 2–30 keV band and achieve highest sensitivity among all-sky monitors ever flown so far. GSC employs large-area position-sensitive proportional counters with a total detector area 5350 cm $^2$. on-board data processor has functions format telemetry as well control high voltage protect them...
Abstract Here we study a 1–200 keV energy spectrum of the black hole binary Cygnus X-1 taken with NuSTAR and Suzaku . This is first report observation Cyg in intermediate state, was during part orbit where absorption due to companion’s stellar wind minimal. The includes multi-temperature thermal disk component, cutoff power-law relativistic nonrelativistic reflection components. Our initial fits publicly available constant density models ( relxill reflionx ) lead extremely high iron...
We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in hard state. This is first time this state has been observed Cyg with NuSTAR, which enables us to study reflection broadband spectra unprecedented detail. confirm that iron line cannot be fit a combination narrow lines absorption features, instead requiring relativistically blurred profile from companion wind. use models García et al. simultaneously measure black...
A precise measurement of the cosmic-ray proton spectrum with Calorimetric Electron Telescope (CALET) is presented in energy interval from 50 GeV to 60 TeV, and observation a softening above 10 TeV reported. The analysis based on data collected during ∼6.2 years smooth operations aboard International Space Station covers broader range respect previous flux by CALET, an increase available statistics factor ∼2.2. Above few hundred we confirm our progressive spectral hardening higher...
We present the results of a direct measurement cosmic-ray helium spectrum with CALET instrument in operation on International Space Station since 2015. The observation period covered by this analysis spans from October 13, 2015, to April 30, 2022 (2392 days). very wide dynamic range allowed for collection data over large energy interval, ∼40 GeV ∼250 TeV, first time single low Earth orbit. measured shows evidence deviation flux power law more than 8σ progressive spectral hardening few...
We present the results from simultaneous Chandra HETGS and Rossi X-ray Timing Explorer (RXTE) observations of microquasar GRS 1915+105 in its quasi-stable "soft state" (or State A) performed on 2007 August 14, several days after state transition "hard (State C). The flux increased with spectral hardening around middle observation, which 67 Hz quasi-periodic oscillation (QPO) became significant. spectra reveal at least 32 narrow absorption lines highly ionized ions including Ne, Mg, Si, S,...
Abstract The black-hole binary Cygnus X-1 was observed for 17ks with the Suzaku X-ray observatory in 2005 October, while it a low/hard state 0.7-300keV luminosity of $4.6\times 10^{37}$ ergs $^{-1}$ . XIS and HXD spectra, spanning 0.7-400keV, were reproduced successfully, incorporating cool accretion disk hot Comptonizing corona. corona is characterized by an electron temperature $ \sim$ 100keV, two optical depths 0.4 1.5, which account softer harder continua, respectively. has innermost...
We report the in-orbit performance of Gas Slit Camera (GSC) on MAXI (Monitor All-sky X-ray Image) mission carried International Space Station (ISS). Its commissioning operation started August 8, 2009, confirmed basic performances effective area in energy band 2--30 keV, spatial resolution slit-and-slat collimator and detector with 1.5 degree FWHM, source visibility 40-150 seconds for each scan cycle, sky coverage 85% per 92-minute orbital period 95% day. The gas gains read-out amplifier have...
We present a generalized analytic formalism for the inverse Compton X-ray emission from hydrogen-poor supernovae and apply this framework to SN 2011fe using Swift X-Ray Telescope (XRT), UVOT, Chandra observations. characterize optical properties of in bands find them be broadly consistent with "normal" Ia, however, no source is detected by either XRT or Chandra. constrain progenitor system mass-loss rate (3σ c.l.) wind velocity vw = 100 km s−1. Our result rules out symbiotic binary...
In this paper, we present the measurement of energy spectra carbon and oxygen in cosmic rays based on observations with Calorimetric Electron Telescope International Space Station from October 2015 to 2019. Analysis, including detailed assessment systematic uncertainties, results are reported. The measured kinetic per nucleon $10\text{ }\text{ }\mathrm{GeV}/n$ $2.2\text{ }\mathrm{TeV}/n$ an all-calorimetric instrument a total thickness corresponding 1.3 nuclear interaction length. observed...
The Calorimetric Electron Telescope (CALET), in operation on the International Space Station since 2015, collected a large sample of cosmic-ray iron over wide energy interval. In this Letter measurement spectrum is presented range kinetic per nucleon from $10\text{ }\text{ }\mathrm{GeV}/n$ to $2.0\text{ }\mathrm{TeV}/n$ allowing inclusion list elements studied with unprecedented precision by space-borne instruments. based observations carried out January 2016 May 2020. CALET instrument can...
We present the results of high-resolution spectroscopy absorption-line features highly ionized ions in X-ray spectra GX 13+1 with Chandra HETGS. have resolved Kα absorption lines hydrogen-like Fe, Mn, Cr, Ca, Ar, S, Si, and Mg helium-like Fe ions. Applying Voigt profile to these spectral features, we find that plasma responsible for has a significant blueshift 460 ± 70 km s-1, indicating an outflow velocity ≈400 s-1 corrected proper motion, line-of-sight dispersion 490 s-1. The is...
Most black hole binaries show large changes in X-ray luminosity caused primarily by variations mass accretion rate. An important question for understanding and jet production is whether the inner edge of disk recedes at low Measurements location (Rin) can be made using iron emission lines that arise due to fluorescence disk, these indicate Rin very close high moderate luminosities (≳1% Eddington luminosity, LEdd). Here, we report on observations GX 339 − 4 hard state Suzaku Rossi Timing...
One of the most prominent, yet controversial associations derived from ensemble prompt-phase observations gamma-ray bursts (GRBs) is apparent correlation in source frame between peak energy (Epeak) νF(ν) spectrum and isotropic radiated energy, Eiso. Since GRBs have Epeak above range (15–150 keV) Burst Alert Telescope (BAT) on Swift, determining accurate values for large numbers Swift has been difficult. However, by combining data Swift/BAT Suzaku Wide-band All-Sky Monitor (WAM), which covers...
We report on the results from Suzaku broadband X-ray observations of galactic binary source LS5039. The data, which have continuous coverage more than one orbital period, show strong modulation emission at period this TeV gamma-ray emitting system.The shows a minimum phase ~ 0.1, close to so-called superior conjunction compact object, and maximum ~0.7, very inferior object. spectral data up 70 keV are described by hard power-law with phase-dependent photon index varies within Gamma ~1.45 -...
X-ray and near-infrared ($J$-$H$-$K_{\rm s}$) observations of the Galactic black hole binary GX 339--4 in low/hard state were performed with Suzaku IRSF 2009 March. The spectrum 0.5--300 keV band is dominated by thermal Comptonization multicolor disk photons, a small contribution from direct component, indicating that inner almost fully covered hot corona an electron temperature $\approx$175 keV. Comptonizing has at least two optical depths, $\tau \approx 1,0.4$. Analysis iron-K line profile...