Curriculum Vitaes
Profile Information
- Affiliation
- Professor, Institute of Space and Astronautical Science, Department of Astrophysics, Japan Aerospace Exploration Agency
- J-GLOBAL ID
- 201801002962836691
- researchmap Member ID
- B000323419
- External link
Research Interests
2Research Areas
1Research History
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Aug, 2005 - Present
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Apr, 1992 - Jul, 2005
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Aug, 2001 - Dec, 2004
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Apr, 1991 - Mar, 1992
Education
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Apr, 1986 - Mar, 1991
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Apr, 1980 - Mar, 1986
Committee Memberships
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Nov, 2020 - Present
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Apr, 2020 - Present
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Apr, 2020 - Present
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Apr, 2020 - Present
Papers
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The Astrophysical Journal, Apr 1, 2024
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The Astrophysical Journal, Jan 1, 2024
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Physical Review Letters, 131(19), Nov 9, 2023
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The Astrophysical Journal, Nov 1, 2023
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Physical review letters, 131(10) 109902, Sep 8, 2023This corrects the article DOI: 10.1103/PhysRevLett.130.211001.
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The Astrophysical Journal, Sep 1, 2023
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The cosmic-ray electron and positron spectrum measured with CALET on the International Space StationProceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 18, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 17, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 17, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 17, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 17, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 14, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 14, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 14, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 11, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 9, 2023
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Monthly Notices of the Royal Astronomical Society, Aug 9, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 8, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Aug 8, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023), Jul 25, 2023
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Physical Review Letters, 130(21), May 25, 2023
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Physical Review Letters, 130(17), Apr 27, 2023
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The Astrophysical Journal, Mar 1, 2023
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ASTRONOMISCHE NACHRICHTEN, Feb, 2023Radiation-magnetohydrodynamic simulation of the active galactic nuclei predicts the presence of the strong accretion disk wind, which gets unstable far from the central region and turns into gas clumps. These inner wind and outer clumps may be actually observed as the ultrafast outflows (UFOs) and the clumpy absorbers, respectively. We call this picture as the "hot inner and clumpy outer wind model. " Observationally, it is challenging to place constraints on the origin of the UFOs and clumpy absorbers due to complicated spectral variations. We developed a novel method, "spectral-ratio model fitting, " to resolve parameter degeneracy of the clumpy absorbers and other spectral components. In this method, the parameters of the absorber in the line of sight are estimated from the ratio of the partially absorbed spectrum to the non-absorbed one. We applied this method to the narrow-line Seyfert 1 galaxy IRAS 13224-3809 observed by XMM-Newton in 2016 for 1.5 Ms, where the source showed extreme spectral variability and complex absorption features. As a result, we found that the soft spectral variation is mostly explained by a change in the covering fraction of the mildly-ionized clumpy absorbers, and that these absorbers are outflowing with such a high velocity that is comparable to that of the UFO (similar to 0.2-0.3 c).
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Physical Review Letters, 129(25), Dec 16, 2022 Peer-reviewedWe present the measurement of the energy dependence of the boron flux in cosmic rays and its ratio to the carbon flux in an energy interval from 8.4 GeV/n to 3.8 TeV/n based on the data collected by the Calorimetric Electron Telescope (CALET) during ∼6.4 yr of operation on the International Space Station. An update of the energy spectrum of carbon is also presented with an increase in statistics over our previous measurement. The observed boron flux shows a spectral hardening at the same transition energy E0∼200 GeV/n of the C spectrum, though B and C fluxes have different energy dependences. The spectral index of the B spectrum is found to be γ=-3.047±0.024 in the interval 25<E<200 GeV/n. The B spectrum hardens by ΔγB=0.25±0.12, while the best fit value for the spectral variation of C is ΔγC=0.19±0.03. The B/C flux ratio is compatible with a hardening of 0.09±0.05, though a single power-law energy dependence cannot be ruled out given the current statistical uncertainties. A break in the B/C ratio energy dependence would support the recent AMS-02 observations that secondary cosmic rays exhibit a stronger hardening than primary ones. We also perform a fit to the B/C ratio with a leaky-box model of the cosmic-ray propagation in the Galaxy in order to probe a possible residual value λ0 of the mean escape path length λ at high energy. We find that our B/C data are compatible with a nonzero value of λ0, which can be interpreted as the column density of matter that cosmic rays cross within the acceleration region.
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Physical Review Letters, 129(10), Sep 1, 2022
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, Aug 31, 2022
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The Astrophysical Journal, 933(1) 85-85, Jul 1, 2022Abstract The CALorimetric Electron Telescope (CALET) on the International Space Station consists of a high-energy cosmic-ray CALorimeter (CAL) and a lower-energy CALET Gamma-ray Burst Monitor (CGBM). CAL is sensitive to electrons up to 20 TeV, cosmic-ray nuclei from Z = 1 through Z ∼ 40, and gamma rays over the range 1 GeV–10 TeV. CGBM observes gamma rays from 7 keV to 20 MeV. The combined CAL-CGBM instrument has conducted a search for gamma-ray bursts (GRBs) since 2015 October. We report here on the results of a search for X-ray/gamma-ray counterparts to gravitational-wave events reported during the LIGO/Virgo observing run O3. No events have been detected that pass all acceptance criteria. We describe the components, performance, and triggering algorithms of the CGBM—the two Hard X-ray Monitors consisting of LaBr3(Ce) scintillators sensitive to 7 keV–1 MeV gamma rays and a Soft Gamma-ray Monitor BGO scintillator sensitive to 40 keV–20 MeV—and the high-energy CAL consisting of a charge detection module, imaging calorimeter, and the fully active total absorption calorimeter. The analysis procedure is described and upper limits to the time-averaged fluxes are presented.
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Proceedings of Science, 398, May 12, 2022The Calorimetric Electron Telescope (CALET) was launched on the International Space Station in 2015 and since then has collected a large sample of cosmic-ray charged particles over a wide energy. Thanks to a couple of layers of segmented plastic scintillators placed on top of the detector, the instrument is able to identify the charge of individual elements from proton to iron (and above). The imaging tungsten scintillating fiber calorimeter provides accurate particle tracking and the lead tungstate homogeneous calorimeter can measured the energy with a wide dynamic range. One of the CALET scientific objectives is to measure the energy spectra of cosmic rays to shed light on their acceleration and propagation in the Galaxy. By the observation in first five years, a precise measurement of the iron spectrum is now available in the range of kinetic energy per nucleon from 10 GeV/n to 2 TeV/n. The CALET's result with a description of the analysis and details on systematic uncertainties will be illustrated. Also, a comparison with previous experiments' results is given.
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 513(4) 5020-5033, May, 2022NGC 5548 is a very well-studied Seyfert 1 galaxy in broad wavelengths. Previous multiwavelength observation campaigns have indicated that its multiple absorbers are highly variable and complex. A previous study applied a two-zone partial covering model with different covering fractions to explain the complex X-ray spectral variation and reported a correlation between one of the covering fractions and the photon index of the power-law continuum. However, it is not straightforward to physically understand such a correlation. In this paper, we propose a model to avoid this unphysical situation; the central X-ray emission region is partially covered by clumpy absorbers composed of double layers. These 'double partial coverings' have precisely the same covering fraction. Based on our model, we have conducted an extensive spectral study using the data taken by XMM-Newton, Suzaku, and NuSTAR in the range of 0.3-78 keV for 16 yr. Consequently, we have found that the X-ray spectral variations are mainly explained by independent changes of the following three components; (1) the soft excess spectral component below similar to 1 keV, (2) the cut-off power-law normalization, and (3) the partial covering fraction of the clumpy absorbers. In particular, spectral variations above similar to 1 keV are mostly explained only by the changes of the partial covering fraction and the power-law normalization. In contrast, the photon index and all the other spectral parameters are not significantly variable.
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Physical Review Letters, 128(13), Apr, 2022The relative abundance of cosmic ray nickel nuclei with respect to iron is by far larger than for all other transiron elements; therefore it provides a favorable opportunity for a low background measurement of its spectrum. Since nickel, as well as iron, is one of the most stable nuclei, the nickel energy spectrum and its relative abundance with respect to iron provide important information to estimate the abundances at the cosmic ray source and to model the Galactic propagation of heavy nuclei. However, only a few direct measurements of cosmic-ray nickel at energy larger than ∼3 GeV/n are available at present in the literature, and they are affected by strong limitations in both energy reach and statistics. In this Letter, we present a measurement of the differential energy spectrum of nickel in the energy range from 8.8 to 240 GeV/n, carried out with unprecedented precision by the Calorimetric Electron Telescope (CALET) in operation on the International Space Station since 2015. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z=40). The particle's energy is measured by a homogeneous calorimeter (1.2 proton interaction lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation lengths) providing tracking and energy sampling. This Letter follows our previous measurement of the iron spectrum [1O. Adriani (CALET Collaboration), Phys. Rev. Lett. 126, 241101 (2021).PRLTAO0031-900710.1103/PhysRevLett.126.241101], and it extends our investigation on the energy dependence of the spectral index of heavy elements. It reports the analysis of nickel data collected from November 2015 to May 2021 and a detailed assessment of the systematic uncertainties. In the region from 20 to 240 GeV/n our present data are compatible within the errors with a single power law with spectral index -2.51±0.07.
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Journal of Low Temperature Physics, 209(3-4) 396-408, 2022Feedhorn- and orthomode transducer- (OMT) coupled transition edge sensor (TES) bolometers have been designed and micro-fabricated to meet the optical specifications of the LiteBIRD high frequency telescope (HFT) focal plane. We discuss the design and optical characterization of two LiteBIRD HFT detector types: dual-polarization, dual-frequency-band pixels with 195/280 GHz and 235/337 GHz band centers. Results show well-matched passbands between orthogonal polarization channels and frequency centers within 3% of the design values. The optical efficiency of each frequency channel is conservatively reported to be within the range 0.64- 0.72, determined from the response to a cryogenic, temperature-controlled thermal source. These values are in good agreement with expectations and either exceed or are within 10% of the values used in the LiteBIRD sensitivity forecast. Lastly, we report a measurement of loss in Nb/SiNx/Nb microstrip at 100 mK and over the frequency range 200–350 GHz, which is comparable to values previously reported in the literature.
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Dec 20, 2021Presence of the apparently extended hard (2-10 keV) X-ray emission along the Galactic plane has been known since the early 1980s. With a deep X-ray exposure using the Chandra X-ray Observatory of a slightly off-plane region in the Galactic bulge, most of the extended emission was resolved into faint discrete X-ray sources in the Fe K band (Revnivtsev et al.,2009). The major constituents of these sources have long been considered to be X-ray active stars and magnetic cataclysmic variables (CVs). However, recent works including our NIR imaging and spectroscopic studies (Morihana et al.,2013, 2016) argue that other populations should be more dominant. To investigate this further, we conducted a much deeper NIR imaging observation at the center of the Chandra's exposure field. We have used the MOIRCS on the Subaru telescope, reaching the limiting magnitude of ~18 mag in the J, H, and Ks bands in this crowded region, and identified ~50 % of the X-ray sources with NIR candidate counterparts. We classified the X-ray sources into three groups (A, B, and C) based on their positions in the X-ray color-color diagram and characterized them based on the X-ray and NIR features. We argue that the major populations of the Group A and C sources are, respectively, CVs (binaries containing magnetic or non-magnetic white dwarfs with high accretion rates) and X-ray active stars. The major population of the Group B sources is presumably WD binaries with low mass accretion rates. The Fe K equivalent width in the composite X-ray spectrum of the Group B sources is the largest among the three and comparable to that of the Galactic bulge X-ray emission. This leads us to speculate that there are numerous WD binaries with low mass accretion rates, which are not recognized as CVs, but are the major contributor of the apparently extended X-ray emission.
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Journal of Astronomical Telescopes, Instruments, and Systems, 7(03), Jul 1, 2021X-Ray Imaging and Spectroscopy Mission (XRISM) is an x-ray astronomical mission led by the Japan Aerospace Exploration Agency (JAXA) and National Aeronautics and Space Administration (NASA), with collaboration from the European Space Agency (ESA) and other international participants, that is planned for launch in 2022 (Japanese fiscal year), to quickly restore high-resolution x-ray spectroscopy of astrophysical objects using the microcalorimeter array after the loss of Hitomi satellite. In order to enhance the scientific outputs of the mission, the Science Operations Team (SOT) is structured independently from the Instrument Teams (ITs) and the Mission Operations Team. The responsibilities of the SOT are divided into four categories: (1) guest observer program and data distributions, (2) distribution of analysis software and the calibration database, (3) guest observer support activities, and (4) performance verification and optimization activities. Before constructing the operations concept of the XRISM mission, lessons on the science operations learned from past Japanese x-ray missions (ASCA, Suzaku, and Hitomi) are reviewed, and 15 kinds of lessons are identified by categories, such as lessons on the importance of avoiding non-public ("animal") tools, coding quality of public tools in terms of the engineering viewpoint and calibration accuracy, tight communications with ITs and operations teams, and well-defined task division between scientists and engineers. Among these lessons, (a) the importance of early preparation of the operations from the ground stage, (b) construction of an independent team for science operations separate from the instrument development, and (c) operations with well-defined duties by appointed members are recognized as key lessons for XRISM. Based on this, (i) the task division between the mission and science operations and (ii) the subgroup structure within the XRISM Team are defined in detail as the XRISM operations concept. Based on this operations concept, the detailed plan of the science operations is designed as follows. The science operations tasks are shared among Japan, the USA, and Europe and are performed by three centers: the Science Operations Center (SOC) at JAXA, the Science Data Center (SDC) at NASA, and European Space Astronomy Centre (ESAC) at the ESA. The SOT is defined as a combination of the SOC and SDC. The SOC is designed to perform tasks close to the spacecraft operations, such as spacecraft planning of science targets, quick-look health checks, and prepipeline data processing. The SDC covers tasks regarding data calibration processing (pipeline processing) and maintenance of analysis tools. The data-archive and user-support activities are planned to be covered both by the SOC and SDC. Finally, the details of the science operations tasks and the tools for science operations are defined and prepared before launch. This information is expected to be helpful for the construction of science operations of future x-ray missions. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
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Physical Review Letters, 126(24), Jun 14, 2021
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Journal of Astronomical Telescopes, Instruments, and Systems, 7(2), Apr, 2021Resolve onboard the x-ray satellite X-Ray Imaging and Spectroscopy Mission (XRISM) is a cryogenic instrument with an x-ray microcalorimeter in a Dewar. A lid partially transparent to x-rays (called gate valve or GV) is installed at the top of the Dewar along the optical axis. Because observations will be made through the GV for the first few months, the x-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission using the x-ray beamline at ISAS. For the Be window, we used synchrotron facilities to measure the transmission and modeled the data with (i) photoelectric absorption and incoherent scattering of Be, (ii) photoelectric absorption of contaminants, and (iii) coherent scattering of Be changing at specific energies. We discuss the physical interpretation of the transmission discontinuity caused by the Bragg diffraction in polycrystal Be, which we incorporated into our transmission phenomenological model. We present the x-ray diffraction measurement on the sample to support our interpretation. The measurements and the constructed model meet the calibration requirements of the GV. We also performed a spectral fitting of the Crab nebula observed with Hitomi SXS and confirmed improvements of the model parameters.
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, Dec 21, 2020
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Physical Review Letters, 125(25), Dec 18, 2020
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Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, Dec 16, 2020
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, Dec 15, 2020
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray, 11444, Dec 13, 2020Resolve onboard the X-ray satellite XRISM is a cryogenic instrument with an X-ray microcalorimeter in a Dewar. A lid partially transparent to X-rays is installed at the top of the Dewar along the optical axis, which is called the gate valve (GV). Because observations will be made through the GV for the first few months, the X-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission using the X-ray beamline at ISAS for the first time. For the Be window, we used synchrotron facilities to measure the transmission and modeled the data with (i) photoelectric absorption and incoherent scattering of Be, (ii) photoelectric absorption of contaminants, and (iii) coherent scattering of Be. We discuss the physical interpretation of the transmission discontinuity caused by the Bragg diffraction in poly-crystal Be, which we incorporated into our phenomenological model. The measurements and the constructed model meet the calibration requirements of the GV. We also performed a spectral fitting of the Crab nebula data observed with Hitomi SXS and confirmed improvements of the model.
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ASTROPHYSICAL JOURNAL LETTERS, 899(1) L20-L20, Aug, 2020 Peer-reviewedWe report the first half-year monitoring of the new Galactic black hole candidate MAXI J1348-630, discovered on 2019 January 26 with the Gas Slit Camera on board the Monitor of All-sky X-ray Image (MAXI). During the monitoring period, the source exhibited two outburst peaks, where the first peak flux (at T = 14 days from the discovery of T = 0) was similar to 4 Crab (2-20 keV) and the second one (at T = 132 days) was similar to 0.4 Crab (2-20 keV). The source exhibited distinct spectral transitions between the high/soft and low/hard states and an apparent "q"-shape curve on the hardness-intensity diagram, both of which are well-known characteristics of black hole binaries (BHBs). Compared to other bright black hole transients, MAXI J1348-630 is characterized by its low disk temperature (similar to 0.75 keV at the maximum) and high peak flux in the high/soft state. The low peak temperature leads to a large innermost radius that is identified as the innermost stable circular orbit, determined by the black hole mass and spin. Assuming the empirical relation between the soft-to-hard transition luminosity (L-trans) and the Eddington luminosity (L-Edd), L-trans/L-Edd approximate to 0.02, and a face-on disk around a non-spinning black hole, the source distance and the black hole mass are estimated to be D approximate to 4 kpc and similar to 7(D/4kpc)M-circle dot. respectively. The black hole is more massive if the disk is inclined and the black hole is spinning. These results suggest that MAXI J1348-630 may host a relatively massive black hole among the known BHBs in our Galaxy.
Misc.
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ASTRONOMICAL DATA ANALYSIS SOFTWARE AND SYSTEMS XXVI, 521 205-208, 2019We are developing the web-based quick data analysis tools JUDO2 and UDON2 at DARTS (http: //darts.isas.jaxa.jp). JUDO2 adopts Aladin Lite to display various astronomical survey data. In particular, we have created HiPS data of Suzaku, MAXI, ASCA and Swift, and publish them from DARTS. In addition, we made various types of the constellation data in HiPS format. Recently, thanks to cooperation by ESA-sky team, the XMM fields of view (footprints) and direct links to the XMM-archive at ESA are made available in JUDO2. UDON2 allows users to extract spectra and light-curves of MAXI, Suzaku and ASCA data. Users can display favorite targetstars or sky regions in JUDO2, and jump to UDON2 to quickly analyze these targets. We are going to add JAXA's other astronomical data (e.g. Akari pointing data, Hitomi) to JUDO2 and UDON2.
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ASTRONOMICAL DATA ANALYSIS SOFTWARE AND SYSTEMS XXVIII, 523 515-518, 2019CALET (CALorimetric Electron Telescope) has been installed and operational on the Japanese Experiment Module Exposed Facility of the International Space Station (ISS) since August 2015. We describe the Web analaysis system for the CALET Gamma-ray Burst Monitor (CGBM), which is publicly available from DARTS.
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ASTRONOMICAL DATA ANALYSIS SOFTWARE AND SYSTEMS XXVI, 521 46-49, 2019Over the past few years the Hierarchical Progressive Survey (HiPS) has become a key method for the distribution of all -sky reference data. Today, HiPS represents about 100 TB of data, and is expected to double each year as the network of a dozen of HiPS providers including ESAC, JAXA, CADC and CDS grows. HiPS data sets are used by thousands of users per day through various HiPS aware clients: Aladin, MIZAR, Aladin Lite, and Aladin-Lite based ESASky and JUDO2. We expect that this technology will be one of the main methods for the distribution of surveys - images, catalogs and cubes - for the next decade. In this extremely fast growing environment, we will discuss why the HiPS network is an excellent candidate for long term management of all-sky reference data. We highlight how the intrinsic HiPS architecture based on the well known HEALPix geometry, a simple tile structure, straightforward distribution method based only on a basic HTTP server, and being standardised by IVOA, constitutes an extremely robust foundation for a system which will support all-sky data distribution for a long time.
Presentations
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第1回 SPARC Japan セミナー2020 「研究データ公開：フルオープンと制限公開の境界線」, Oct 2, 2020 Invited
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JpGU-AGU Joint Meeting 2020:Virtual ユニオンセッション U-12 「地球惑星科学の進むべき道10 ビッグデータとオープンサイエンス」, Jul 15, 2020 Invited
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20 Years of Chandra Science Symposium
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The 29th annual international Astronomical Data Analysis Software & Systems (ADASS)
Professional Memberships
1Research Projects
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Japan Society for the Promotion of Science, Apr, 2016 - Mar, 2019
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Japan Society for the Promotion of Science, 2009 - 2011
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Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Japan Society for the Promotion of Science, 2007 - 2009
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Grants-in-Aid for Scientific Research Grant-in-Aid for international Scientific Research, Japan Society for the Promotion of Science, 1992 - 1994
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科学研究費助成事業 奨励研究(特別研究員), 日本学術振興会, 1990 - 1990
