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
257-
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.
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
14-
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
