Masayoshi Nobukawa
A5074475497- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Advanced X-ray Imaging Techniques
- Atomic and Molecular Physics
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Galaxies: Formation, Evolution, Phenomena
- Advanced X-ray and CT Imaging
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- X-ray Spectroscopy and Fluorescence Analysis
- Calibration and Measurement Techniques
- Ionosphere and magnetosphere dynamics
- Adaptive optics and wavefront sensing
- Atmospheric Ozone and Climate
- Nuclear Physics and Applications
- CCD and CMOS Imaging Sensors
- Dark Matter and Cosmic Phenomena
- Astro and Planetary Science
- Spacecraft Design and Technology
- Historical Astronomy and Related Studies
Nara University of Education
2016-2025
Kanto Gakuin University
2020-2024
Kyoto University
2009-2024
Saitama University
2024
University of Miyazaki
2022-2024
University of Maryland, Baltimore County
2024
Goddard Space Flight Center
2020-2024
Nagoya University
2024
Nara Women's University
2018-2020
Kindai University
2020
The high energy activity in the inner few degrees of Galactic center is traced by diffuse radio, X-ray and gamma-ray emission. physical relationship between different components gas emitting at multiple wavelengths a focus this work. We first present radio continuum observations using Green Bank Telescope model nonthermal spectrum terms broken power-law distribution GeV electrons synchrotron radiation. show that emission detected Fermi primarily due to bremsstrahlung produced population...
Despite decades of intense efforts, many fundamental aspects Type Ia supernova (SNe Ia) remain elusive. One the major open questions is whether mass exploding white dwarf (WD) close to Chandrasekhar limit. Here we report detection strong K-shell emission from stable Fe-peak elements in Suzaku X-ray spectrum remnant (SNR) 3C 397. The high Ni/Fe and Mn/Fe ratios (0.11-0.24 0.018-0.033, respectively) hot plasma component that dominates lines indicate a degree neutronization SN ejecta which can...
Abstract We present XRISM Resolve observations of the core hot, relaxed galaxy cluster Abell 2029 (A2029). find that line-of-sight bulk velocity intracluster medium (ICM) within central 180 kpc is at rest with respect to brightest galaxy, a 3 σ upper limit ∣ v < 100 km s −1 . robustly measure field-integrated ICM dispersion be = 169 ± 10 , obtaining similar results for both single-temperature and two-temperature plasma models account cool core. This result, if ascribed isotropic...
Supernova remnants (SNRs) retain crucial information about both their parent explosion and circumstellar material left behind by progenitor. However, the complexity of interaction between supernova ejecta ambient medium often blurs this information, it is not uncommon for basic progenitor type (Ia or core-collapse) well-studied to remain uncertain. Here we present a powerful new observational diagnostic discriminate types constrain density SNRs using solely Fe K-shell X-ray emission. We...
We report on the global distribution of intensities K-shell lines from He-like and H-like ions S, Ar, Ca, Fe along Galactic plane. From profiles, we clearly separate center X-ray emission (GCXE) ridge (GRXE). The intensity profiles K$ \alpha $ plane are approximately similar to each other, while not for Ly$ lines. In particular, S show remarkable contrast: a large excess Fe, almost no in GCXE compared GRXE. Although prominent represented by \sim$ 1 keV 7 temperature plasmas, these two...
Abstract We present an initial analysis of the X-Ray Imaging and Spectroscopy Mission (XRISM) first-light observation supernova remnant (SNR) N 132D in Large Magellanic Cloud. The Resolve microcalorimeter has obtained first high-resolution spectrum 1.6–10 keV band, which contains K-shell emission lines Si, S, Ar, Ca, Fe. find that Si S are relatively narrow, with a broadening represented by Gaussian-like velocity dispersion $\sigma _v \sim 450$ km s$^{-1}$. However, Fe He$\alpha$...
Abstract We present an analysis of the first two XRISM/Resolve spectra well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 4151, obtained 2023 December. Our work focuses on nature narrow Fe K α emission line at 6.4 keV, strongest and most common X-ray observed AGN. The total is found to consist three components. Even narrowest component resolved with evident ,1 (6.404 keV) ,2 (6.391 contributions a 2:1 flux ratio, fully consistent neutral gas negligible bulk velocity. Subject...
This paper presents Suzaku results obtained for the Sagittarius (Sgr) C region using concept of X-ray reflection nebulae (XRNe) as echo past flares from a super-massive black hole, Sgr A*. The complex is composed several molecular clouds proximately located in projected distance. spectra were analyzed based on view that XRNe are inside Galactic center plasma emission with an oval distribution around We found largely separated line-of-sight position, and associated different velocity ranges...
Prominent K-shell emission lines of neutral iron (hereafter, FeI-K) and hard-continuum X-rays were found from molecular clouds (MCs) in the Sagittarius B (Sgr B) region with two separate Suzaku observations 2005 2009. The X-ray flux FeI-K decreased correlation to by factor 0.4-0.5 4 years, which is nearly equal light-travelling across MCs. rapid correlated time-variability, equivalent width FeI-K, K-edge absorption depth FeI are consistently explained "X-ray echoes" due fluorescent...
We report Suzaku results for soft X-ray emission to the south of Galactic center (GC). The (hereafter "GC South") has an angular size ~42' x 16' centered at (l, b) ~ (0.0, -1.4), and is located in largely extended ridge (GRXE). spectrum GC South exhibits lines from highly ionized atoms. Although GRXE can be well fitted with a plasma collisional ionization equilibrium (CIE), that cannot CIE, leaving hump-like residuals ~2.5 3.5 keV, which are attributable radiative recombination continua...
Abstract Supernova remnants (SNRs) are the primary candidate of Galactic cosmic-ray accelerators. It is still an open issue when and how young SNRs, which typically exhibit strong synchrotron X-rays GeV TeV gamma rays, undergo state transition to middle-aged SNRs dominated by thermal rays. SNR N132D in Large Magellanic Cloud ideal target study such a transition, exhibiting bright with expected age ∼2500 years. In this paper we present results NuSTAR Suzaku spectroscopy. We reveal that has...
The high energy resolution and low background, particularly in the hard X-ray band, of Imaging Spectrometer onboard Suzaku provide excellent spectra Galactic center diffuse X-rays (GCDX). This paper reports on results spatially resolved spectroscopy GCDX. most pronounced features GCDX are K-shell transition lines from neutral (Fe i) He-like xxv) irons at energies 6.4 keV 6.7 keV, respectively. fluxes these non-uniformly asymmetrically distributed with respect to Sgr A$^\ast$. bright positive...
The K-shell emission line of neutral irons from the Galactic center (GC) region is one key for structure and activity GC. origin still open question, but possibly due either to X-ray radiation or electron bombarding atoms. To address this issue, we analyzed Suzaku spectrum GC intense iron emission, report on discovery Kalpha lines argon, calcium, chrome, manganese equivalent widths these indicate that metal abundances in should be ~1.6 ~4 solar value, depending origins, respectively. On...
This paper reports detailed K-shell line profiles of iron (Fe) and nickel (Ni) the Galactic Center X-ray Emission (GCXE), Bulge (GBXE), Ridge (GRXE), magnetic Cataclysmic Variables (mCVs), non-magnetic (non-mCVs), coronally Active Binaries (ABs). For study origin GCXE, GBXE, GRXE, spectral analysis is focused on equivalent widths Fe K$α$, He$α$, Ly$α$ lines. The global spectrum GBXE reproduced by a combination mCVs, non-mCVs, ABs spectra. On other hand, GRXE shows significant data excesses...
Abstract We report X-ray spectroscopic results for four giant solar flares that occurred on 2005 September 7 (X17.0), 8 (X5.4), 9 (X6.2), and 2006 December 5 (X9.0), obtained from Earth albedo data with the Imaging Spectrometer (XIS) board Suzaku . The good energy resolution of XIS (FWHM ∼ 100 eV) enables us to separate a number line-like features detect underlying continuum emission. These include Si He α , Ly S Ar Ca originating as well fluorescent K β Earth’s atmosphere. Absolute...
XRISM (X-ray Imaging and Spectroscopy Mission) is an X-ray astronomy satellite developed in collaboration with JAXA, NASA ESA. It successfully launched on Sept. 7, 2023. Two complementary telescopes, Resolve Xtend are on-board XRISM. uses the pixelized micro calorimeter by NASA/GSFC has very high energy resolution of 5 eV. On other hand, CCD camera as its focal plane detector which spatial a wide field view. We evaluated performance Mirror Assembly (XMA) for using data observed during...
Abstract The X-ray binary system Cygnus X-3 (4U 2030+40, V1521 Cyg) is luminous but enigmatic owing to the high intervening absorption. High-resolution spectroscopy uniquely probes dynamics of photoionized gas in system. In this Letter, we report on an observation Cyg with XRISM/Resolve spectrometer, which provides unprecedented spectral resolution and sensitivity 2–10 keV band. We detect multiple kinematic ionization components absorption emission whose superposition leads complex line...
The Soft X-ray Imager (SXI) is the charge-coupled device (CCD) camera for soft imaging telescope Xtend installed on Imaging and Spectroscopy Mission (XRISM), which was adopted as a recovery mission Hitomi satellite successfully launched 2023 September 7 (JST). In order to maximize science output of XRISM, we set requirements find that CCD employed in Hitomi/SXI or similar, i.e., $2 \times 2$ array back-illuminated CCDs with $200~\mu$m-thick depletion layer, would be practically best among...
Abstract The Soft X-ray Imager (SXI) is the charge-coupled device (CCD) camera for soft imaging telescope Xtend installed on Imaging and Spectroscopy Mission (XRISM), which was adopted as a recovery mission Hitomi satellite successfully launched 2023 September 7 (JST). In order to maximize science output of XRISM, we set requirements found that CCD employed in Hitomi/SXI or similar, i.e., $2 \times 2$ array back-illuminated CCDs with $200\, \mu$m-thick depletion layer, would be practically...
Abstract The non-thermal neutral iron line can be a probe of low-energy cosmic rays; when rays ionize atoms in the interstellar medium, would emit line. In this paper, we investigated couple supernova remnants (SNRs), G304.6$+$0.1 and G346.6-0.2, which are known to associated with molecular clouds. Analyzing Suzaku archive data, discovered enhancements significance level $\sim \! 3\sigma$ two SNRs. addition, conducted detailed study CO clouds examine detail evidence for shock–cloud...
Abstract The XRISM Resolve microcalorimeter array measured the velocities of hot intracluster gas at two positions in Coma galaxy cluster: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mi>′</mml:mi> </mml:msup> <mml:mo>×</mml:mo> </mml:math> squares center and 6 (170 kpc) to south. We find line-of-sight velocity dispersions those regions be σ z = 208 ± 12 km s −1 202 24 , respectively. central value...