A5045097215- Astrophysics and Cosmic Phenomena
- Radiation Detection and Scintillator Technologies
- Astrophysical Phenomena and Observations
- Particle Detector Development and Performance
- Gamma-ray bursts and supernovae
- Nuclear Physics and Applications
- Dark Matter and Cosmic Phenomena
- Medical Imaging Techniques and Applications
- Advanced X-ray and CT Imaging
- Radiation Therapy and Dosimetry
- High-pressure geophysics and materials
- Pulsars and Gravitational Waves Research
- Atomic and Subatomic Physics Research
- Advanced Semiconductor Detectors and Materials
- Atomic and Molecular Physics
- Particle physics theoretical and experimental studies
- Laser-Plasma Interactions and Diagnostics
- Astronomical Observations and Instrumentation
- Radioactive Decay and Measurement Techniques
- Nuclear physics research studies
- Advanced X-ray Imaging Techniques
- Electromagnetic Launch and Propulsion Technology
- Acoustic Wave Resonator Technologies
- Diamond and Carbon-based Materials Research
- Radio Astronomy Observations and Technology
RIKEN Nishina Center
2020-2024
Waseda University
2024
Kanagawa University
2023
RIKEN
2021-2023
University of Würzburg
2023
Kavli Institute for the Physics and Mathematics of the Universe
2018-2021
The University of Tokyo
2016-2021
Institute of Space and Astronautical Science
2016-2017
Japan Aerospace Exploration Agency
2017
University of Electro-Communications
2005
To understand the nature of brightest γ-ray binary system LS 5039, hard x-ray data object, taken with Suzaku and NuSTAR observatories in 2007 2016, respectively, were analyzed. The two sets jointly gave tentative evidence for a periodicity, period ∼9 s increase rate by ∼3×10^{-10} s^{-1}. Therefore, compact object 5039 is inferred to be rotating neutron star, rather than black hole. Furthermore, several lines arguments suggest that this has magnetic field times ∼10^{10} T, orders magnitude...
Abstract The Compton Spectrometer and Imager balloon payload (COSI-Balloon) is a wide field-of-view gamma-ray telescope that operates in the 0.2–5 MeV bandpass. COSI-Balloon had successful 46 day flight 2016 during which instrument observed Crab Nebula, Cygnus X-1, Centaurus A. Using data collected by this flight, we present source flux extraction of signals from variable background environment produce images these background-dominated sources performing Richardson–Lucy deconvolutions. We...
We present measurements of the afterglow signatures in NaI(Tl) and CsI(Tl) detector modules as part Background Transient Observer (BTO) mission trade-study. BTO is a NASA Student Collaboration Project flying on Compton Spectrometer Imager (COSI) Small Explorer 2027. The detectors utilized this study are cylindrical shape with height diameter 5.1 cm were read out by silicon photomultipliers (SiPMs). conducted radiation campaign at HIMAC accelerator Japan where scintillators irradiated 230...
We present a modified Richardson-Lucy (RL) algorithm tailored for image reconstruction in MeV gamma-ray observations, focusing on its application to the upcoming Compton Spectrometer and Imager (COSI) mission. Our method addresses key challenges astronomy by incorporating Bayesian priors sparseness smoothness while optimizing background components simultaneously. introduce novel sparsity term suitable Poisson-sampled data addition prior, allowing flexible of both point sources extended...
We experimentally show that the $1{s}^{2}2{s}^{2}2{p}_{1/2}\ensuremath{-}1s2{s}^{2}2{p}_{1/2}^{2}$ transition in ${\mathrm{Pb}}^{77+}$ emitted dielectronic recombination of ${\mathrm{Pb}}^{78+}$ is strongly polarized, although it an intrinsically unpolarized $J=1/2$ to $1/2$ transition. This unanticipated polarization shown be due quantum interference with radiative recombination. The effect has been studied on asymmetric resonance profile but never polarization. In this Letter, we can arise...
In an X-ray reflection spectrum, a tail-like spectral feature generated via Compton down-scattering, known as shoulder (CS), appears at the low-energy side of iron K$\alpha$ line. Despite its great diagnostic potential, use probe reflector has been seriously limited due to observational difficulties and modelling complexities. We revisit basic nature CS by systematic investigation into dependence on spatial temporal parameters. The calculations are performed Monte-Carlo simulations for...
This paper describes an analysis of the NuSTAR data fastest-rotating magnetar 1E 1547$-$5408, acquired in 2016 April for a time lapse 151 ks. The source was detected with 1-60 keV flux $1.7 \times 10^{-11}$ ergs s$^{-1}$ cm$^{-2}$, and its pulsation at period $2.086710(5)$ sec. In 8-25 keV, pulses were phase-modulated $T=36.0 \pm 2.3$ ks, amplitude $\sim 0.2$ reconfirms Suzaku discovery same effect ^{+4.5}_{-2.5} $ made 2009 outburst. These results strengthen view derived from data, that...
The Compton Spectrometer and Imager (COSI) is a NASA Small Explorer (SMEX) satellite mission in development with planned launch 2027. COSI wide-field gamma-ray telescope designed to survey the entire sky at 0.2-5 MeV. It provides imaging, spectroscopy, polarimetry of astrophysical sources, its germanium detectors provide excellent energy resolution for emission line measurements. Science goals include studies 0.511 MeV from antimatter annihilation Galaxy, mapping radioactive elements...
Abstract The present study aims to reinforce the evidence for ∼9 s pulsation in gamma-ray binary LS 5039, derived from a Suzaku observation 2007 and NuSTAR 2016. Through reanalysis of data incorporating orbital Doppler correction, 9.0538 was confirmed successfully even 3–10 keV range, where it undetectable previously. This attained by perceiving an energy-dependent drift pulse phase below 10 correcting timing individual photons that effect. Similarly, archival 0.7–12 set taken with ASCA Gas...
Application of Compton cameras to nuclear medicine or small animal imaging is a challenging subject. A major issue insufficient spatial resolutions the existing camera systems. We developed an system consisting two Si/CdTe cameras, which allows us investigate γ- γ coincidence for variety radioisotopes, including <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">111</sup> In, emits double photons 171 and 245 keV per decay has been used long time in...
X-ray timing properties of the magnetar SGR 1900+14 were studied, using data taken with Suzaku in 2009 and NuSTAR 2016, for a time lapse 114 ks 242 ks, respectively. On both occasions, object exhibited characteristic two-component spectrum. The soft component, dominant energies below $\sim 5$ keV, showed regular pulsation, period $P=5.21006$ s as determined XIS, $P=5.22669$ NuSTAR. However, $\gtrsim 6$ keV where hard component dominates, pulsation became detectable HXD NuSTAR, only after...
Tomographic imaging with radionuclides commonly used in nuclear medicine, such as $^{111}$In (171 and 245 keV) $^{131}$I (364 keV), is high demand for medical applications small animal imaging. The Si/CdTe Compton camera its angular energy resolutions an especially promising detector to extend the coverage range that covers gamma-ray emitted from these radionuclides. Here, we take first steps towards short-distance by conducting experiments using three-dimensional phantoms composed of...
Abstract The origin of the inner Galactic emission, measured by COMPTEL with a flux ∼10 −2 MeV cm s −1 sr in 1–30 energy range from region, has remained unsettled since its discovery. In this paper, we elaborate on model individual gamma-ray sources unresolved COMPTEL. This is conducted for crossmatched between Swift-BAT and Fermi-LAT catalogs interpolating spectra hard X-ray GeV ranges, as well unmatched two catalogs. We find that source contribution to emission would be at least ∼20%....
Abstract To detect and track structural changes in atomic nuclei, the systematic study of nuclear levels with firm spin-parity assignments is important. While linear polarization measurements have been applied to determine electromagnetic character gamma-ray transitions, applicable range strongly limited due low efficiency detection system. The multi-layer Cadmium-Telluride (CdTe) Compton camera can be a state-of-the-art polarimeter for spectroscopy high position sensitivity efficiency. We...
The methods to measure the polarization of x-rays from highly charged heavy ions with a significantly higher accuracy than existing technology is needed explore relativistic and quantum electrodynamics (QED) effects including Breit interaction. We developed Electron Beam Ion Trap Compton Camera (EBIT-CC), new polarimeter pixelated multi-layer silicon cadmium telluride counters. EBIT-CC detects three-dimensional position scattering photoelectric absorption, thus degree incoming can be...
Abstract Gamma-ray binary systems, a subclass of high-mass X-ray binaries, show nonthermal emissions from radio to TeV. While efficient electron acceleration is considered take place in them, the nature mechanism and physical environments these systems have been long-standing question. In this work, we report on long-term recurrent patterns short-term variability soft emission LS 5039, one brightest gamma-ray systems. The Neutron star Interior Composition Explorer (NICER) observed 5039 four...
The Gamma-Ray and AntiMatter Survey (GRAMS) project is a proposed next-generation balloon/satellite mission targeting both MeV gamma-ray observations antimatter-based dark matter searches. A cost-effective, large-scale Liquid Argon Time Projection Chamber (LArTPC) detector technology will allow GRAMS to have significantly improved sensitivity gamma rays while extensively probing parameter space via antimatter measurements.
We report a polarization measurement of $L$-shell radiative recombination (RR) x rays emitted from He- to F-like bismuth ions. The feature was obtained the azimuthal angular distribution Compton-scattered RR detected with recently developed state-of-the-art Compton polarimeter installed on an electron beam ion trap. This is one very few measurements ever conducted and first derived degree linear averaged over charge states be $0.666\ifmmode\pm\else\textpm\fi{}0.014$. By contrast, theoretical...
We report on detailed analysis of the hard X-ray and GeV gamma-ray spectra LS 5039, one brightest binary system in Galaxy. The NuSTAR observation covering its entire orbit 2016 allowed us for first time to study orbital variability spectrum above 10 keV. is well described with a single power-law component up 78 flux showed slight deviation from those observed previously Suzaku 2007. fast brightening Suzaku, around inferior conjunction, was not this observation. also analyzed 11 years Fermi...