研究者業績
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を用いて銀河系内の赤外線前景放射を見積もり、将来のLiteBIRDによる宇宙論観測に生かせるようにしたいと考えています。
東京大学大学院理学系研究科天文学専攻の教員です。
研究キーワード
2研究分野
1経歴
4-
2005年8月 - 現在
-
2001年8月 - 2004年12月
-
1991年4月 - 1992年3月
学歴
2-
1986年4月 - 1991年3月
-
1980年4月 - 1986年3月
委員歴
4-
2020年11月 - 現在
-
2020年4月 - 現在
-
2020年4月 - 現在
-
2020年4月 - 現在
論文
244-
The Astrophysical Journal 2024年4月1日
-
The Astrophysical Journal 2024年1月1日
-
Physical Review Letters 131(19) 2023年11月9日
-
The Astrophysical Journal 2023年11月1日
-
Physical review letters 131(10) 109902 2023年9月8日This corrects the article DOI: 10.1103/PhysRevLett.130.211001.
MISC
116-
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.
-
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.
-
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.
-
Publications of the Astronomical Society of Japan 70(3) 2018年2月14日We present results from the Hitomi X-ray observation of a young<br /> composite-type supernova remnant (SNR) G21.5$-$0.9, whose emission is dominated<br /> by the pulsar wind nebula (PWN) contribution. The X-ray spectra in the 0.8-80<br /> keV range obtained with the Soft X-ray Spectrometer (SXS), Soft X-ray Imager<br /> (SXI) and Hard X-ray Imager (HXI) show a significant break in the continuum as<br /> previously found with the NuSTAR observation. After taking into account all<br /> known emissions from the SNR other than the PWN itself, we find that the Hitomi<br /> spectra can be fitted with a broken power law with photon indices of<br /> $\Gamma_1=1.74\pm0.02$ and $\Gamma_2=2.14\pm0.01$ below and above the break at<br /> $7.1\pm0.3$ keV, which is significantly lower than the NuSTAR result ($\sim9.0$<br /> keV). The spectral break cannot be reproduced by time-dependent particle<br /> injection one-zone spectral energy distribution models, which strongly<br /> indicates that a more complex emission model is needed, as suggested by recent<br /> theoretical models. We also search for narrow emission or absorption lines with<br /> the SXS, and perform a timing analysis of PSR J1833$-$1034 with the HXI and<br /> SGD. No significant pulsation is found from the pulsar. However, unexpectedly,<br /> narrow absorption line features are detected in the SXS data at 4.2345 keV and<br /> 9.296 keV with a significance of 3.65 $\sigma$. While the origin of these<br /> features is not understood, their mere detection opens up a new field of<br /> research and was only possible with the high resolution, sensitivity and<br /> ability to measure extended sources provided by an X-ray microcalorimeter.
-
SPACE TELESCOPES AND INSTRUMENTATION 2018: ULTRAVIOLET TO GAMMA RAY 10699 2018年The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi, "Resolving astrophysical problems by precise high-resolution X-ray spectroscopy".(1) This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission's initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020's and 2030's.Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: "Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects". To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
-
2017年8月31日This document presents HiPS, a hierarchical scheme for the description,<br /> storage and access of sky survey data. The system is based on hierarchical<br /> tiling of sky regions at finer and finer spatial resolution which facilitates a<br /> progressive view of a survey, and supports multi-resolution zooming and<br /> panning. HiPS uses the HEALPix tessellation of the sky as the basis for the<br /> scheme and is implemented as a simple file structure with a direct indexing<br /> scheme that leads to practical implementations.
-
ASTROPHYSICAL JOURNAL LETTERS 837(1) 2017年3月X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E approximate to 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S XVI (E similar or equal to 3.44 keV rest-frame)-a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.
-
years of MAXI: monitoring X-ray Transients 2017年
-
2015年12月1日The Galactic Ridge X-ray Emission (GRXE) spectrum has strong iron emission<br /> lines at 6.4, 6.7, and 7.0~keV, each corresponding to the neutral (or<br /> low-ionized), He-like, and H-like iron ions. The 6.4~keV fluorescence line is<br /> due to irradiation of neutral (or low ionized) material (iron) by hard X-ray<br /> sources, indicating uniform presence of the cold matter in the Galactic plane.<br /> In order to resolve origin of the cold fluorescent matter, we examined the<br /> contribution of the 6.4~keV line emission from white dwarf surfaces in the hard<br /> X-ray emitting symbiotic stars (hSSs) and magnetic cataclysmic variables (mCVs)<br /> to the GRXE. In our spectral analysis of 4~hSSs and 19~mCVs observed with<br /> Suzaku, we were able to resolve the three iron emission lines. We found that<br /> the equivalent-widths (EWs) of the 6.4~keV lines of hSSs are systematically<br /> higher than those of mCVs, such that the average EWs of hSSs and mCVs are<br /> $179_{-11}^{+46}$~eV and $93_{-3}^{+20}$~eV, respectively. The EW of hSSs<br /> compares favorably with the typical EWs of the 6.4~keV line in the GRXE of<br /> 90--300~eV depending on Galactic positions. Average 6.4~keV line luminosities<br /> of the hSSs and mCVs are $9.2\times 10^{39}$ and $1.6\times<br /> 10^{39}$~photons~s$^{-1}$, respectively, indicating that hSSs are intrinsically<br /> more efficient 6.4~keV line emitters than mCVs. We compare expected<br /> contribution of the 6.4 keV lines from mCVs with the observed GRXE 6.4 keV line<br /> flux in the direction of $(l,b) \approx (28.5\arcdeg, 0\arcdeg$). We conclude<br /> that almost all the 6.4 keV line flux in GRXE may be explained by mCVs within<br /> current undertainties of the stellar number densities, while contribution from<br /> hSSs may not be negligible.
-
日本理科教育学会全国大会要項 (65) 198-198 2015年
-
2014年12月3日In this white paper we describe the prospects for ASTRO-H for the study of<br /> outflows from active galactic nuclei. The most important breakthroughs in this<br /> field are expected to arise from the high spectral resolution and sensitivity<br /> in the Fe-K band, combined with broad-band sensitivity over the full X-ray band<br /> and spectral capabilities also at lower energies. The sensitivity in the Fe-K<br /> region allows to extend the absorption measure distribution of the outflow out<br /> to the highest ionisation states accessible, where observations with current<br /> X-ray missions indicate that most of the outflowing gas is to be found. Due to<br /> the high-resolution and sensitivity it will also be able to give the definitive<br /> proof for the existence of ultra-fast outflows, and if so, characterise their<br /> physical properties in great detail. These ultra-fast outflows carry very large<br /> amounts of energy and momentum, and are of fundamental importance for feedback<br /> studies. We show how the ASTRO-H observations in general can help to constrain<br /> numerical models for outflows. The link to reflection and emission processes is<br /> also discussed, as well as the possible relation between outflows and<br /> relativistic emission lines. Finally, we discuss the prospects for other<br /> related categories of objects like BAL quasars, partially covered sources and<br /> Compton thick outflows.
-
SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY 9144 2014年WF-MAXI is a soft X-ray transient monitor proposed for the ISS/JEM. Unlike MAXI, it will always cover a large field of view (20 % of the entire sky) to detect short transients more efficiently. In addition to the various transient sources seen by MAXI, we hope to localize X-ray counterparts of gravitational wave events, expected to be directly detected by Advanced-LIGO, Virgo and KAGRA in late 2010's. The main instrument, the Soft X-ray Large Solid Angle Cameras (SLC) is sensitive in the 0.7-12 keV band with a localization accuracy of similar to 0.1 degrees. The Hard X-ray Monitor (HXM) covers the same sky field in the 20 keV-1 MeV band.
-
40th COSPAR Scientific Assembly. Held 2-10 August 2014, in Moscow, Russia, Abstract id. E1.5-54-14. 2014年
-
Astrophysical Journal 779(1) 2013年12月10日We report the results from X-ray studies of the newly discovered black hole candidate MAXI J1305-704 based on Suzaku and Swift observations in the low/hard and high/soft states, respectively. The long Suzaku observation shows two types of clear absorption dips, both of which recur on a dip interval of 9.74 ± 0.04 hr, which we identify with the orbital period. There is also partially ionized absorption in the nondip (persistent) emission in both the high/soft state and, very unusually, the low/hard state. However, this absorption (in both states) has substantially lower ionization than that seen in other high inclination systems, where the material forms a homogeneous disk wind. Here instead the absorption is most likely associated with clumpy, compact structures associated with the dipping material, which we see uniquely in this source likely because we view it at a very large inclination angle. A large inclination angle is also favored, together with a low black hole mass, to explain the high disk temperature seen in the fairly low luminosity high/soft state, as Doppler boosting enhances the disk temperature at high inclination. The disk radius inferred from these data is significantly smaller than that of the soft component seen in the low/hard state, supporting models where the disk is truncated at low luminosities. We find, however, that the lack of variability power on timescales of ∼50 s in the Suzaku low/hard state data is difficult to explain, even with a low-mass black hole. © 2013. The American Astronomical Society. All rights reserved..
-
宇宙航空研究開発機構研究開発報告 12 29-37 2013年3月MAXI(Monitor of All-sky X-ray Image)は2009年8月から「きぼう」船外実験プラットフォーム上で観測を続けている X線全天モニタである.MAXIには2つの主要な役割があり,1つはX線突発変動天体の速報,もう1つは長期にわたる全天のX線による定常的な観測である.MAXIはISSの通信環境により,観測時間の70%はリアルタイムにデータを取得できる.MAXIは,リアルタイムデータを効率良く扱うため,MAXI-DBという地上システムを構築し,それらを利用してこれまでの3年間の観測で150件以上ものX線天体の変動現象に関する観測速報を行った.MAXIの観測データには多くの天体に関する様々な科学情報が含まれるため,データを全世界の科学者に利用しやすい形式で提供することは重要である.我々は段階的にデータ公開を実現してきており,現在までに300程度のカタログ天体の日々の画像,ライトカーブ,エネルギースペクトルデータや,ユーザーが任意に入力した位置/時刻に対応したデータ(オンデマンドデータ)を公開している. MAXIのデータは時間/空間方向で複雑に入り組んでいるため,1日毎に全データを1ファイルにアーカイブする方式では非効率で,オンデマンド公開で天体毎の解析処理の際,要求される処理時間を達成できなかった.そこで,X線データを時刻や到来方向によって整理し,幾つかのファイルに分割し,結合する方式を使ったシステムを構築した.その結果,100倍程度の効率化を達成することができた.
-
宇宙航空研究開発機構研究開発報告 12 19-27 2013年3月科学分野で扱われるデータ量は爆発的に増加しており,膨大なデータに対する機械的処理への要求は極めて高い.論文では,天体物理学におけるX線天体の X線アウトバースト現象を対象に,その観測データの類似検索を行う手法を提案する.具体的には,観測データからアウトバースト部分の自動検出を行なう.得られたデータに対し,ノイズ除去を目的とした平滑化と正規化を施した上で,動的タイムワーピング(DTW; DynamicTimeWarping)法を適用する. DTW法は,長さが異なる時系列データに対しても適用可能であるだけでなく,時間軸方向のスケーリングに対しても頑健なマッチングを行うことが距離である.さらに,X線アウトバーストの持つ特徴や,類似検索に対する要求を考慮し,DTW法の改良手法であるDerivative DTW法や,DTW法に滑り窓を適用した手法など,いくつかの新たな手法を提案する.さらに,実データとの比較によってその有効性を評価する.
-
宇宙航空研究開発機構研究開発報告 12 9-18 2013年3月かねてより筆者らは宇宙科学データの可視化について検討してきた.最近のiOSやAndroid等に代表されるモバイルデバイスは,教育・広報の観点からも無視できない存在になっている.科学データの可視化の 1つの手段として,モバイルデバイスの性能は年々向上しているが,モバイル通信環境は未だ発展途上にあり,科学データを即時に転送できるまでには至っていない.本稿では,利用者を待たせることなく科学データを可視化するために,科学データを逐次取込みながら処理するための手法について提案する.本手法は従来手法と比較して,データ転送に伴う待ち時間を短縮するのみならず,デバイス内のメモリや CPUの使用率低減にも寄与することが期待される.
-
全国大会講演論文集 2012(1) 633-635 2012年3月6日近年の科学分野で扱われるデータの量は膨大である.その筆頭が天文学であり,今も多くのデータが蓄積されている.その内,現在注目されているものの一つに X線天体がある.動的タイムワーピング(Dynamic Time Warping,以下「DTW」)とは,音声や株価といった時系列データを比較する際よく用いられる手法である.これを利用するとDTW距離という類似度を示す一つの数値が得られる.本研究では,全天X線監視装置「MAXI」から提供されるX線天体観測データを対象に,X線天体が起こすバースト現象のデータに対しDTWを用いた類似検索を行い,類似したパターンを示す天体を発見する手法を提案する.
-
第74回全国大会講演論文集 2012(1) 633-634 2012年3月6日近年の科学分野で扱われるデータの量は膨大である．その筆頭が天文学であり，今も多くのデータが蓄積されている．その内，現在注目されているものの一つに X線天体がある．動的タイムワーピング(Dynamic Time Warping，以下「DTW」)とは，音声や株価といった時系列データを比較する際よく用いられる手法である．これを利用するとDTW距離という類似度を示す一つの数値が得られる．本研究では，全天X線監視装置「MAXI」から提供されるX線天体観測データを対象に，X線天体が起こすバースト現象のデータに対しDTWを用いた類似検索を行い，類似したパターンを示す天体を発見する手法を提案する．
-
宇宙航空研究開発機構研究開発報告 11 47-56 2012年3月デジタル技術の進展に伴い,今日,大量の天文観測データが地上の天文台や天文衛星から生み出されつつある.これらの大量データから適切な科学的情報を引き出すために,データを効率よく可視化する方法が望まれている.一方,デジタル技術の進歩により,近年,高精度のイメージをプラネタリウムで投影することが可能になってきている.そこで,この論文では,大規模な天文データの可視化のツールとしてデジタルプラネタリウムを利用する可能性について考察した.実際に,主にJAXA の科学衛星による観測データを用いたプラネタリウム番組を製作したので,その手法について報告する.そのようなプラネタリウム番組は可視化のツールとして使えるだけではなく,教育,アウトリーチ,娯楽の目的も果たすことができる.
-
宇宙航空研究開発機構研究開発報告 11(11-007) 7-11 2012年3月宇宙科学データ可聴化プロジェクトの現状を報告する.宇宙科学データ可聴化プロジェクトでは,日本の科学衛星の取得したX 線パルサーデータや,地磁気の変動を示すKp 指数などの音声化を行ってきた.また,一般的な数値データを音声によって表示するソフトウェアの開発を行った.このソフトウェアにより,数値の並びであった宇宙科学データを視覚障害者にとって意味のある音に変換することができるようになった.本論文では,宇宙科学データ可聴化プロジェクトの現状と,問題点を報告し,今後の開発方針をまとめる.
-
宇宙航空研究開発機構研究開発報告 11(11-007) 13-22 2012年3月時刻データを伴う宇宙科学データの可視化・可聴化手法について,教育・広報目的の観点で述べる.可視化・可聴化の素材としたデータは,X線天文衛星「あすか」や「すざく」の観測データ,太陽地球物理観測衛星「あけぼの」のPWSデータ,地磁気の変動を表すKp指数である.X線天文衛星のデータは,観測された個々の光子の飛来方向,エネルギー,時刻の情報が記録されており,衛星の軌道要素も併せて提供されている.これらのイベントを,衛星軌道と照らし合わせながら,時刻に沿って描画もしくは可聴化することにより,天文観測の追体験が可能となる.PWSデータ及びKp指数は,それぞれの観測値を可聴化することで,地球の周囲を飛び交う電波や地磁気の変化を音の変化として体験することができる.本稿では,広帯域の電波強度分布を記録したPWSデータと楽譜様の変化を記録したKp指数それぞれについて,異なる可聴化を試みた.
-
Proceedings of SPIE - The International Society for Optical Engineering 8443 2012年The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-Throughput spectrometer sensitive over 0.3-12 keV with high spectral resolution of ?E 5 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes. © 2012 SPIE.
-
日本福祉大学健康科学論集 14 1-9 2011年3月30日We are developing a sound-based, interactive, data-plotting program to enable the visually impaired to turn astronomical data into meaningful sounds. The sonification software, called "splot", would be available to any scientist to analyze data. Splot reads ASCII data files containing various plotting commands and other data, and then outputs sounds corresponding to the data instead of plotting to a display or a printer. Input data for splot is partially compatible with "qdp", a data-plotting program developed by NASA HEASARC. In this paper, we report the status of development. In the current version, splot only sonifies a one-dimensional histogram and thus remains an experimental production. Before releasing this software, we must extend its functions for a suitable field test and construct a data-analysis environment for the visually impaired.
-
ASTRONOMY & ASTROPHYSICS 520 2010年9月Context. White dwarfs (WDs) in cataclysmic variables (CVs) are important experimental laboratories where the electron degeneracy is taking place on a macroscopic scale. Magnetic CVs increase in number especially in the hard X-ray band (greater than or similar to 10 keV) thanks to sensitive hard X-ray missions. Aims. From X-ray spectroscopy, we estimate the masses of nearby WDs in moderately-magnetized CVs, or Intermediate Polars (IPs). Methods. Using the Suzaku satellite, we aquired wide-band spectra of 17 IPs, covering 3-50 keV. An accretion column model of Suleimanov et al. (2005, A&A, 435, 191) and an optically-thin thermal emission code were used to construct a spectral emission model of IPs with resolved Fe emission lines. By simultaneously fitting the Fe line complex and the hard X-ray continuum of individual spectra, the shock temperature and the WD mass were determined with a better accuracy than in previous studies. Results. We determined the WD masses of the 17 IPs with statistical fitting errors of less than or similar to 0.1-0.2 M-circle dot in many cases. The WD mass of a recently-found IP, IGR J17195-4100, was also estimated for the first time (1.03(-0.22)(+0.24) M-circle dot). The average WD mass of the sample is 0.88 +/- 0.25 M-circle dot. When our results were compared with previous X-ray mass determinations, we found significant deviation in a few systems although the reason of this is unclear. The iron abundance of the accreting gas was also estimated, and confirmed the previously reported sub-solar tendency in all sources with better accuracy.
-
2010年6月28日We report the detection of a time variable OVII line emission in a deep 100<br /> ks Suzaku X-ray Imaging Spectrometer spectrum of the Galactic Ridge X-ray<br /> emission. The observed line intensity is too strong (11+/-2 line unit or photon<br /> cm^-2 s^-1 str^-1) to be emitted inside the heavily obscured Galactic disk. It<br /> showed a factor of two time variation which shows a significant (~4 sigma)<br /> correlation with the solar wind O^7+ ion flux. The high line intensity and the<br /> good time correlation with the solar wind strongly suggests that it originated<br /> from geocoronal solar wind charge exchange emission. We discuss the X-ray line<br /> intensity considering a line of sight direction and also theoretical<br /> distribution models of the neutral hydrogen and solar wind around the Earth.<br /> Our results indicate that X-ray observationsof geocoronal solar wind charge<br /> exchange emission can be used to constrain these models.
-
2008年10月2日In order to elucidate origin of the Galactic Ridge X-ray Emission, we<br /> analyzed Suzaku data taken at various regions along the Galactic plane and<br /> studied their Fe-K emission line features. Suzaku resolved the Fe line complex<br /> into three narrow lines at ~6.4 keV,~6.7 keV and ~6.97 keV, which are K-lines<br /> from neutral (or low-ionized), He-like, and H-like iron ions, respectively. The<br /> 6.7 keV line is clearly seen in all the observed regions and its longitudinal<br /> distribution is consistent with that determined from previous observations. The<br /> 6.4 keV emission line was also found in various Galactic plane regions (b~0).<br /> Differences in flux ratios of the 6.4 keV/6.7 keV and 6.97 keV/6.7 keV lines<br /> between the Galactic plane and the Galactic center regions are studied and its<br /> implication is discussed.
-
日本物理學會誌 63(9) 670-677 2008年9月5日人工衛星を用いた宇宙観測データは,一定の占有期間の後,解析ソフトウェアとともに無償で公開されることが世界的な標準となっている.データが長期間にわたってアーカイブズ化され,世界中の科学者によって広く共有されることにより,数多くの成果が生み出されるのである.それを目的とし,各国の公的機関が多くの予算とマンパワーを費やして構築した「宇宙科学データアーカイブズ」は,人類共通の貴重な知的財産と言えよう.また,宇宙科学データは,他の多くの分野の科学技術データとは異なり,その利用に金銭的な利害や倫理的な問題が絡まない,という特徴がある.その特徴を生かし,最先端の宇宙科学データを真っ先に取得して世界に公開することは,それによって国際社会からの信頼とリーダーシップを勝ち取るための貴重なソフトパワーになりうる.今後,各国が協力して科学データ共有を進め,国と国との間の信頼関係を高めていくことによって,「科学による安全保障」を実現できるようになるかもしれない.
-
HIGH ENERGY, OPTICAL, AND INFRARED DETECTORS FOR ASTRONOMY III 7021 2008年We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for the nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 20 TeV and gamma rays in 20 MeV - several 10 TeV. CALET has a unique capability to observe electrons and gamma rays over 1 TeV since the hadron rejection power can be larger than 105 and the energy resolution better than a few % over 100 GeV. The detector consists of an imaging calorimeter with scintillating fibers and tungsten plates and a total absorption calorimeter with BGO scintillators. CALET has also a capability to measure cosmic ray H, He and heavy ions up to 1000 TeV. It also will have a function to monitor solar activity and gamma ray transients. The phase A study has started on a schedule of launch in 2013 by H-II Transfer Vehicle (HTV) for 5 year observation.
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
-
20 Years of Chandra Science Symposium
-
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
5-
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
-
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
-
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
-
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
-
日本学術振興会 科学研究費助成事業 奨励研究(特別研究員) 1990年 - 1990年
