基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系 教授
- J-GLOBAL ID
- 201801002962836691
- researchmap会員ID
- B000323419
- 外部リンク
主にX線天文学の研究をやっています。X線天体のフォローアップとして、地上赤外線観測、電波観測もやってます。ブラックホール、中性子星、白色矮星、AGN、銀河面からのX線放射などに興味を持っています。
宇宙航空研究開発機構（JAXA）・宇宙科学研究所（ISAS）にて、MAXI、XRISMを始めとする天文衛星のデータ処理・解析システムの開発、宇宙科学データアーカイブDARTSの運用を行っています。DARTSにおける全天多波長早見システムJUDO2を開発しました。また、「あかり」のアーカイブデータと他の衛星データを組み合わせ、LiteBIRDなどによる将来の宇宙論精密観測に必要な、銀河系内の赤外線前景放射モデルの作成に取り組んでいます。
研究キーワード
2研究分野
1経歴
4-
2005年8月 - 現在
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2001年8月 - 2004年12月
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1991年4月 - 1992年3月
学歴
2-
1986年4月 - 1991年3月
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1980年4月 - 1986年3月
委員歴
4-
2020年11月 - 現在
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2020年4月 - 現在
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2020年4月 - 現在
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2020年4月 - 現在
論文
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The Astrophysical Journal Letters 982(1) L5-L5 2025年3月12日Abstract We present XRISM Resolve observations of the core of the hot, relaxed galaxy cluster Abell 2029 (A2029). We find that the line-of-sight bulk velocity of the intracluster medium (ICM) within the central 180 kpc is at rest with respect to the brightest cluster galaxy, with a 3σ upper limit of ∣v bulk∣ < 100 km s−1. We robustly measure the field-integrated ICM velocity dispersion to be σ v = 169 ± 10 km s−1, obtaining similar results for both single-temperature and two-temperature plasma models to account for the cluster cool core. This result, if ascribed to isotropic turbulence, implies a subsonic ICM with Mach number and a nonthermal pressure fraction of 2.6 ± 0.3%. The turbulent velocity is similar to what was measured in the core of the Perseus cluster by Hitomi, but here in a more massive cluster with an ICM temperature of 7 keV, the limit on the nonthermal pressure fraction is even more stringent. Our result is consistent with expectations from simulations of relaxed clusters, but it is on the low end of the predicted distribution, indicating that A2029 is an exceptionally relaxed cluster with no significant impacts from either a recent minor merger or active galactic nucleus activity.
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Nature 638(8050) 365-369 2025年2月12日
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International Journal of Modern Physics A 2025年1月29日Recent direct measurements of the energy spectra of the charged cosmic ray have revealed unexpected spectral features, most notably the onset of a progressive hardening at few hundreds of GeV/n not only of proton and He spectra but also observable for heavier nuclei. Thus, the study of the spectra behavior of heavy elements may shed light on understanding propagation and acceleration phenomena in our Galaxy. In particular, Fe and Ni provide favorable conditions for observations thanks to the low background contamination from spallation of higher mass elements they are affected by. The CALorimetric Electron Telescope, CALET, has been measuring high-energy cosmic rays on the International Space Station since October 2015. The instrument consists of two layers of segmented plastic scintillators, a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter and a 27 radiation length thick PWO calorimeter. It identifies the charge of individual elements up to Ni and beyond and it measures the energy of cosmic-ray nuclei providing a direct measurement of their spectra. In this contribution, the iron and nickel spectra, resulted after 5 years of data acquisition, are presented in the energy range between 10 and 2000 GeV/n and between 8.8 and 240 GeV/n, respectively. The analysis procedure and the assessment of systematic errors are detailed, in addition to the ratio between the two fluxes. Both spectra show similar shape and energy dependence.
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Publications of the Astronomical Society of Japan 2024年12月26日Abstract Sagittarius A East is a supernova remnant with a unique surrounding environment, as it is located in the immediate vicinity of the supermassive black hole at the Galactic center, Sagittarius A$^{*}$. The X-ray emission of the remnant is suspected to show features of overionized plasma, which would require peculiar evolutionary paths. We report on the first observation of Sagittarius A East with the X-Ray Imaging and Spectroscopy Mission (XRISM). Equipped with a combination of a high-resolution microcalorimeter spectrometer and a large field-of-view CCD imager, we for the first time resolved the Fe xxv K-shell lines into fine structure lines and measured the forbidden-to-resonance intensity ratio to be $1.39 \pm 0.12$, which strongly suggests the presence of overionized plasma. We obtained a reliable constraint on the ionization temperature just before the transition into the overionization state, of $\gt\! 4\:$keV. The recombination timescale was constrained to be $\lt\! 8 \times 10^{11} \:$cm$^{-3}\:$s. The small velocity dispersion of $109 \pm 6\:$km$\:$s$^{-1}$ indicates a low Fe ion temperature $\lt\! 8\:$keV and a small expansion velocity $\lt\! 200\:$km$\:$s$^{-1}$. The high initial ionization temperature and small recombination timescale suggest that either rapid cooling of the plasma via adiabatic expansion from dense circumstellar material or intense photoionization by Sagittarius A$^{*}$ in the past may have triggered the overionization.
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The Astrophysical Journal Letters 977(2) L34-L34 2024年12月11日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 X-ray spectroscopy uniquely probes the dynamics of the photoionized gas in the system. In this Letter, we report on an observation of Cyg X-3 with the XRISM/Resolve spectrometer, which provides unprecedented spectral resolution and sensitivity in the 2–10 keV band. We detect multiple kinematic and ionization components in absorption and emission whose superposition leads to complex line profiles, including strong P Cygni profiles on resonance lines. The prominent Fe xxv Heα and Fe xxvi Lyα emission complexes are clearly resolved into their characteristic fine-structure transitions. Self-consistent photoionization modeling allows us to disentangle the absorption and emission components and measure the Doppler velocity of these components as a function of binary orbital phase. We find a significantly higher velocity amplitude for the emission lines than for the absorption lines. The absorption lines generally appear blueshifted by ∼−500–600 km s−1. We show that the wind decomposes naturally into a relatively smooth and large-scale component, perhaps associated with the background wind itself, plus a turbulent, denser structure located close to the compact object in its orbit.
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Publications of the Astronomical Society of Japan 2024年10月10日Abstract We present an initial analysis of the X-Ray Imaging and Spectroscopy Mission (XRISM) first-light observation of the supernova remnant (SNR) N 132D in the Large Magellanic Cloud. The Resolve microcalorimeter has obtained the first high-resolution spectrum in the 1.6–10 keV band, which contains K-shell emission lines of Si, S, Ar, Ca, and Fe. We find that the Si and S lines are relatively narrow, with a broadening represented by a Gaussian-like velocity dispersion of $\sigma _v \sim 450$ km s$^{-1}$. However, the Fe He$\alpha$ lines are substantially broadened with $\sigma _v \sim 1670$ km s$^{-1}$. This broadening can be explained by a combination of the thermal Doppler effect due to the high ion temperature and the kinematic Doppler effect due to the SNR expansion. Assuming that the Fe He$\alpha$ emission originates predominantly from the supernova ejecta, we estimate the reverse shock velocity at the time when the bulk of the Fe ejecta were shock heated to be $-1000 \lesssim V_{\rm rs}$ (km s$^{-1}$) $\lesssim 3300$ (in the observer frame). We also find that Fe Ly$\alpha$ emission is redshifted with a bulk velocity of $\sim 890$ km s$^{-1}$, substantially larger than the radial velocity of the local interstellar medium surrounding N 132D. These results demonstrate that high-resolution X-ray spectroscopy is capable of providing constraints on the evolutionary stage, geometry, and velocity distribution of SNRs.
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The Astrophysical Journal Letters 973(1) L25-L25 2024年9月1日Abstract We present an analysis of the first two XRISM/Resolve spectra of the well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 4151, obtained in 2023 December. Our work focuses on the nature of the narrow Fe K α emission line at 6.4 keV, the strongest and most common X-ray line observed in AGN. The total line is found to consist of three components. Even the narrowest component of the line is resolved with evident Fe K α,1 (6.404 keV) and K α,2 (6.391 keV) contributions in a 2:1 flux ratio, fully consistent with neutral gas with negligible bulk velocity. Subject to the limitations of our models, the narrowest and intermediate-width components are consistent with emission from optically thin gas, suggesting that they arise in a disk atmosphere and/or wind. Modeling the three line components in terms of Keplerian broadening, they are readily associated with (1) the inner wall of the “torus,” (2) the innermost optical “broad-line region” (or “X-ray BLR”), and (3) a region with a radius of r ≃ 100 GM/c 2 that may signal a warp in the accretion disk. Viable alternative explanations of the broadest component include a fast-wind component and/or scattering; however, we find evidence of variability in the narrow Fe K α line complex on timescales consistent with small radii. The best-fit models are statistically superior to simple Voigt functions, but when fit with Voigt profiles the time-averaged lines are consistent with a projected velocity broadening of FWHM . Overall, the resolution and sensitivity of XRISM show that the narrow Fe K line in AGN is an effective probe of all key parts of the accretion flow, as it is currently understood. We discuss the implications of these findings for our understanding of AGN accretion, future studies with XRISM, and X-ray-based black hole mass measurements.
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Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray 60-60 2024年8月21日
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Advances in Space Research 2024年4月
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The Astrophysical Journal 2024年4月1日
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Advances in Space Research 2024年3月
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The Astrophysical Journal 2024年1月1日
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Physical Review Letters 131(19) 2023年11月9日
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The Astrophysical Journal 2023年11月1日
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Physical review letters 131(10) 109902 2023年9月8日This corrects the article DOI: 10.1103/PhysRevLett.130.211001.
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The Astrophysical Journal 2023年9月1日
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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) 2023年8月18日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月17日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月17日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月17日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月17日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月14日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月14日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月14日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月11日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月9日
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Monthly Notices of the Royal Astronomical Society 2023年8月9日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月8日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月8日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年7月25日
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Physical Review Letters 130(21) 2023年5月25日
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Physical Review Letters 130(17) 2023年4月27日
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The Astrophysical Journal 2023年3月1日
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ASTRONOMISCHE NACHRICHTEN 2023年2月Radiation-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) 2022年12月16日 査読有りWe 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) 2022年9月1日
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 2022年8月31日
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The Astrophysical Journal 933(1) 85-85 2022年7月1日Abstract 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 2022年5月12日The 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 2022年5月NGC 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) 2022年4月The 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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Proceedings of Science, 37th International Cosmic Ray Conference Volume 395(100) 2022年3月18日
MISC
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ASTRONOMICAL DATA ANALYSIS SOFTWARE AND SYSTEMS XXVI 521 205-208 2019年We 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 2019年CALET (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 2019年Over 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.
講演・口頭発表等
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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」 2020年7月15日 招待有り
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20 Years of Chandra Science Symposium
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The 29th annual international Astronomical Data Analysis Software & Systems (ADASS)
所属学協会
1共同研究・競争的資金等の研究課題
6-
日本学術振興会 科学研究費助成事業 2024年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 基盤研究(C) 2016年4月 - 2019年3月
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日本学術振興会 科学研究費助成事業 基盤研究(C) 2009年 - 2011年
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日本学術振興会 科学研究費助成事業 基盤研究(B) 2007年 - 2009年
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日本学術振興会 科学研究費助成事業 国際学術研究 1992年 - 1994年
