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宇宙航空研究開発機構研究開発報告: 宇宙科学情報解析論文誌 JAXA-RR-22-009(12) 31-40 2023年2月28日 査読有り超伝導の原理に基づく論理回路の一種である，単一磁束量子回路の動作を説明するためのインタラクティブ可視化手法について述べる．宇宙探査に関わる将来構想のひとつとして，単一磁束量子回路を用いたデバイスを宇宙機に搭載することが検討されている．単一磁束量子回路はデバイスの動作に係る電力消費が極めて小さく，また演算速度の高速化も期待されている．一方で単一磁束量子回路はCPU やメモリ等，半導体デバイスの論理回路と動作原理が大きく異なるため，その理解の助けとなるような可視化ツールが有用であると期待される．本稿においては，単一磁束量子回路の動作について，WebGL ベースのAPI 等のJavaScript を用いたインタラクティブ可視化アプリケーションを構築し，その課題や将来展望等について検討した．
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宇宙航空研究開発機構研究開発報告: 宇宙科学情報解析論文誌 JAXA-RR-14-009(4) 105-125 2015年3月31日 査読有りDARTS (http://darts.jaxa.jp/)は, JAXAの様々な科学衛星のデータを研究用に公開するデータアーカイブシステムであり, 宇宙科学研究所科学衛星運用・データ利用センター(C-SODA)が運用している. 我々は, 赤外線天文衛星「あかり」の全天サーベイ観測によって得られた2次元画像(全天マップ)を公開するための検索機能付きウェブインターフェースを開発している. 全天マップは, 多数の画像ファイルがタイル状に並んで全天球面をカバーするように構成されており, それぞれの画像は数度平方程度の天域を占めている. 本検索機能において, ユーザーに指定された領域を一部でも含む画像ファイルは全て検索結果として返されるものとする. そのような検索を実現するため, 各画像内を多数の小さな矩形領域に分割して各領域の中心点を直交座標系で表し, その座標値をデータベースに登録するという方法が採用される. この方法は, HEALPixのような外部の天球分割ライブラリが不要で, 天の両極が特異点にならず, かつ任意の座標系を用いた高速検索が可能という利点を持つ.開発と維持管理のコストを低減させるため, われわれはあかりカタログ検索の仕組みを本検索機能に応用し, またPHPとPostgreSQLを用いることによって本機能を実装する.
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宇宙航空研究開発機構研究開発報告: 宇宙科学情報解析論文誌 JAXA-RR-13-010(3) 17-26 2014年3月31日 査読有り責任著者GSTOS (Generic Spacecraft Test and Operations Software; 汎用衛星試験運用ソフトウェア) は，ISAS (Institute of Space and Aeronautical Science) の今後の衛星の試験と運用に使用される汎用のソフトウェアであり，SIB2 (Spacecraft Information Base version 2) に基づき動作する．SIB2/GSTOS-1 プロジェクトは，SPRINT-A, ASTRO-H, Bepi/MMO 向けのSIB2/GSTOSを開発するプロジェクトである．本論文では，SIB2/GSTOS-1 プロジェクトが目指すゴール，従来のISAS における典型的な衛星試験・運用システムに対する改善点を述べるとともに，現在までの開発状況，今後の課題について述べる．
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SOLAR PHYSICS AND SPACE WEATHER INSTRUMENTATION V 8862 2013年 査読有りWe present a design progress of the Solar UV-Vis-IR Telescope (SUVIT) aboard the next Japanese solar mission SOLAR-C. SUVIT has an aperture diameter of similar to 1.4 m for achieving spectro-polarimetric observations with spatial and temporal resolution exceeding the Hinode Solar Optical Telescope (SOT). We have studied structural and thermal designs of the optical telescope as well as the optical interface between the telescope and the focal plane instruments. The focal plane instruments are installed into two packages, filtergraph and spectrograph packages. The spectropolarimeter is the instrument dedicated to accurate polarimetry in the three spectrum windows at 525 nm, 854 nm, and 1083 nm for observing magnetic fields at both the photospheric and chromospheric layers. We made optical design of the spectrograph accommodating the conventional slit spectrograph and the integral field unit (IFU) for two-dimensional coverage. We are running feasibility study of the IFU using fiber arrays consisting of rectangular cores.
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ASTROPHYSICAL JOURNAL 688(2) 1374-1381 2008年12月 査読有りWe present observations of the magnetic landscape of the polar region of the Sun that are unprecedented in terms of spatial resolution, field of view, and polarimetric precision. They were carried out with the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington inversion, we find many vertically oriented magnetic flux tubes with field strengths as strong as 1 kG scattered in latitude between 70 degrees and 90 degrees. They all have the same polarity, consistent with the global polarity of the polar region. The field vectors are observed to diverge from the centers of the flux elements, consistent with a view of magnetic fields that are expanding and fanning out with height. The polar region is also found to have ubiquitous horizontal fields. The polar regions are the source of the fast solar wind, which is channeled along unipolar coronal magnetic fields whose photospheric source is evidently rooted in the strong-field, vertical patches of flux. We conjecture that vertical flux tubes with large expansion around the photospheric-coronal boundary serve as efficient chimneys for Alfven waves that accelerate the solar wind.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 60(4) 827-834 2008年8月We obtained temperature structures in faint coronal features above and near the solar limb with the X-Ray Telescope aboard the Hinode satellite by accurately correcting the scattered X-rays from surrounding bright regions with occulted images during the solar eclipses. Our analysis yields a polar coronal hole temperature of about 1.0 MK and an emission measure in the range of 10(25.5)-10(26.0) cm(-5). In addition, our methods allow us to measure the temperature and emission measure of two distinct quiet-Sun structures: radial (plume-like) structures near the boundary of the coronal-hole and diffuse quiet Sun regions at mid-latitudes. The radial structures appear to have increasing temperature with height during the first 100 Mm, and constant temperatures above 100 Mm. For the diffuse quiet-Sun region the temperatures are the highest just above the limb, and appear to decrease with height. These differences may be due to different magnetic configurations.
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SOLAR PHYSICS 249(2) 263-279 2008年6月 査読有りThe X-ray Telescope (XRT) aboard the Hinode satellite is a grazing incidence X-ray imager equipped with a 2048x2048 CCD. The XRT has 1 arcsec pixels with a wide field of view of 34x34 arcmin. It is sensitive to plasmas with a wide temperature range from < 1 to 30 MK, allowing us to obtain TRACE-like low-temperature images as well as Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data Processor (MDP) controls the XRT through sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection, and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field of view for a given telemetry bandwidth. With a focus adjust mechanism, a higher resolution of Gaussian focus may be available on-axis. This paper follows the first instrument paper for the XRT (Golub et al., Solar Phys. 243, 63, 2007) and discusses the design and measured performance of the X-ray CCD camera for the XRT and its control system with the MDP.
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SOLAR PHYSICS 249(2) 221-232 2008年6月 査読有りThe Hinode Solar Optical Telescope (SOT) is the first space-borne visible-light telescope that enables us to observe magnetic-field dynamics in the solar lower atmosphere with 0.2-0.3 arcsec spatial resolution under extremely stable (seeing-free) conditions. To achieve precise measurements of the polarization with diffraction-limited images, stable pointing of the telescope (< 0.09 arcsec, 3 sigma) is required for solar images exposed on the focal plane CCD detectors. SOT has an image stabilization system that uses image displacements calculated from correlation tracking of solar granules to control a piezo-driven tip-tilt mirror. The system minimizes the motions of images for frequencies lower than 14 Hz while the satellite and telescope structural design damps microvibration in higher frequency ranges. It has been confirmed from the data taken on orbit that the remaining jitter is less than 0.03 arcsec (3 sigma) on the Sun. This excellent performance makes a major contribution to successful precise polarimetric measurements with 0.2-0.3 arcsec resolution.
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FIRST RESULTS FROM HINODE 397 102-+ 2008年We present Hinode/EIS raster scan observations of the GOES X3.2 flare that occurred on 2006 December 13. There was a small transient coronal hole which was located 200 arcsec east of the flare arcade. The transient coronal hole was strongly affected by the X-class flare, and the strong upflows were observed in Fe XV line 284.2 angstrom (log T/K = 6.3) at the boundary of dimming region. In this paper, we discuss how to obtain the velocity map by correcting the instrumental effects.
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Science (New York, N.Y.) 318(5856) 1585-8 2007年12月7日The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray-emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to approximately 1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 59 S757-S762 2007年11月 査読有りThe velocity structures of jets in a coronal hole have been derived for the first time. Hinode observations revealed the existence of many bright points in coronal holes. They are loop-shaped and sometimes associated with coronal jets. Spectra obtained with the Extreme-ultraviolet Imaging Spectrometer aboard Hinode were analyzed to infer the Doppler velocity of bright loops and jets in a coronal hole of the north polar region. Elongated jets above bright loops are found to be blue-shifted by 30 km s(-1) at maximum, while foot points of bright loops are red-shifted. Blue-shifts detected in coronal jets are interpreted as being upflows produced by magnetic reconnection between emerging flux and the ambient field in the coronal hole.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 59(S3) S793-S799 2007年11月We present Hinode/EIS raster scan observations of the plage region taken during the gradual phase of the GOES X3.2 flare that occurred on 2006 December 13. The plage region is located 200 '' east of the flare arcade. The plage region has a small transient coronal hole. The transient coronal hole is strongly affected by an X-class flare, and upflows are observed at its boundary. Multi-wavelength spectral observations allow us to determine velocities from the Doppler shifts at different temperatures. Strong upflows along with stationary plasma have been observed in the Fe XV line 284.2 angstrom (log T/K = 6.3) in the plage region. The strong upflows reach almost 150 km s(-1), which was estimated by a two-component Gaussian fitting. On the other hand, at a lower corona/transition region temperature (He II, 256.3 angstrom, log T/K = 4.9), very weak upflows, almost stationary, have been observed. We find that these upflow velocities clearly depend on the temperature with the hottest line, Fe XV, showing the fastest upflow velocity and the second-highest line, Fe XIV, showing the second-highest upflow velocity (130 km s-1). All velocities are below the sound speed. The trend of the upflow dependence on temperature dramatically changes at 1 MK. These results suggest that heating may have an important role for strong upflow.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 59 S845-S852 2007年11月 査読有りTo understand the physical mechanisms for activity and heating in the solar atmosphere, the magnetic coupling from the photosphere to the corona is an important piece of information from the Hinode observations, and therefore precise positional alignment is required among the data acquired by different telescopes. The Hinode spacecraft and its onboard telescopes were developed to allow us to investigate magnetic coupling with co-alignment accuracy better than 1 ''. Using the Mercury transit observed on 2006 November 8 and co-alignment measurements regularly performed on a weekly basis, we have determined the information necessary for precise image co-alignment, and have confirmed that co-alignment better than 1 '' can be realized between Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our baseline co-alignment method. This paper presents results from the calibration for precise co-alignment of CCD images from SOT and XRT.
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Solar Physics 243(1) 87-92 2007年6月All of the Hinode telemetry data are to be reformatted and archived in the DARTS system at ISAS and mirrored to data centers around the word. The archived data are distributed to users through the Internet. This paper gives an overview of the files in the archive, including the file formats. All formats are portable and have heritage from the previous missions. From the reformatted files, index information is created for faster data search. Users can perform queries based on information contained in the index. This allows for searches to return observations that conform to particular observing conditions. © 2007 Springer.
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日本航空宇宙学会論文集 55(637) 57-64 2007年The solar observation satellite "SOLAR-B," which is being developed under the joint cooperation of JAXA and NAOJ with the U.S.A. (NASA) and the U.K. (PPARC), will be launched in summer 2006. SOLAR-B requires very high pointing stability for its three telescopes. In particular, the Solar Optical Telescope (SOT), which has the highest resolution and narrowest field of view among these telescopes, requires 0.06 [arcsec]3σ of short-term (10[s]) stability to meet the observation demands. However, it is very difficult to achieve such levels of stability by only using the satellite attitude control system due to disturbance from the observation equipment. Therefore, we propose using the Correlation Tracker and tip-tilt Mirror package (CTM), which stabilizes the sun observation image. CTM consists of a correlation tracker and a piezo-based tip-tilt mirror with servo control electronics. This paper describes the mechanism and the control and determination methods of the control gain of CTM as well as the results of experiments conducted to clarify its capability.
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The discovery of diffuse X-ray emission in NGC 2024, one of the nearest massive star-forming regionsASTROPHYSICAL JOURNAL 649(2) L123-L128 2006年10月 査読有りWe analyzed deep 75 ks Chandra ACIS-I data of NGC 2024 with the aim of searching for diffuse X-ray emission in this most nearby (415 pc) of massive star-forming regions. After removing point sources, extended emission was detected in the central circular region with a radius of 0.5 pc, and it is spatially associated with this young massive stellar cluster. Its X-ray spectrum exhibits a very hard continuum (kT > 8 keV) and shows signs of having a He-like Fe K alpha line with a 0.5-7 keV absorption-corrected luminosity of 2 x 10(31) ergs s(-1). Undetected faint point sources, estimated from the luminosity function of the detected sources, contribute less than 10% to this emission. Hence, the emission is truly diffuse in nature. Because of the proximity of NGC 2024 and the long exposure, this discovery is one of the strongest pieces of evidence in support of the existence of diffuse X-ray emission in massive star-forming regions.
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Astrophysical Journal 638(2 I) 860-877 2006年2月20日 査読有りChandra ACIS-I data of the molecular cloud and H n region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto and coworkers) were resolved into 792 point sources. After removing the point sources, an extended X-ray emission component was detected over a 5 × 9 pc2 region, with the 0.5-8 keV absorption-corrected luminosity of 2 × 10 33 ergs s-1. The contribution from faint point sources to this extended emission was estimated as at most ∼20%, suggesting that most of the emission is diffuse in nature. The X-ray spectrum of the diffuse emission was observed to vary from place to place. In tenuous molecular cloud regions with hydrogen column density of (0.5-1) × 1022 cm-2, the spectrum can be represented by a thermal plasma model with temperatures of several keV. The spectrum in dense cloud cores exhibits harder continuum, together with higher absorption of more than ∼3 × 1022 cm-2. In some of such highly obscured regions, the spectra show extremely hard continua equivalent to a photon index of ∼1, and favor a nonthermal interpretation. These results are discussed in the context of thermal and nonthermal emission, both powered by fast stellar winds from embedded young early-type stars through shock transitions. © 2006. The American Astronomical Society. All rights reserved.
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Solar-B Mission and the Forefront of Solar Physics, Proceedings 325 15-25 2004年The Soft X-ray Telescope (XRT) aboard Solar-B is a grazing incidence X-ray telescope equipped with 2k x 2k CCD. XRT has I arcsec resolution with wide field-of-view of 34 x 34 arcmin. It is sensitive to < 1 MK to 30 MK, allowing us to obtain TRACE-like low temperature images as well. Co-alignment with SOT and EIS is realized through the XRT visible light telescope and with temperature overlap with EIS. Spacecraft mission data processor (MDP) controls XRT through the sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field-of-view for given telemetry bandwidth. With focus adjust mechanism, higher resolution of Gaussian focus may be available on-axis.
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OPTICAL, INFRARED, AND MILLIMETER SPACE TELESCOPES, PTS 1-3 5487 1189-1198 2004年 査読有りWe present scientific as well as engineering overview of the X-Ray Telescope (XRT) aboard the Japanese Solar-B mission to be launched in 2006, with emphasis on the focal plane CCD camera that employs a 2k x 2k back-thinned CCD. Characterization activities for the flight CCD camera made at the National Astronomical Observatory of Japan (NAOJ) are discussed in detail with some of the results presented.
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Monthly Notices of the Royal Astronomical Society 328(1) 112-126 2001年11月21日 査読有りExtremely strong ionized Fe emission lines, with equivalent widths reaching ∼4000 eV, were discovered by ASCA from a few Galactic compact objects, including AX J2315-0592, RX J1802.1 + 1804 and AX J1842.8-0423. These objects are thought to be binary systems containing magnetized white dwarfs (WDs). A possible interpretation of the strong Fe K line is the line-photon collimation in the WD accretion column, as a result of resonance scattering of line photons. The collimation occurs when the accretion column has a flat shape, and the effect is augmented by the vertical velocity gradient, which reduces the resonant trapping of resonant photons along the magnetic field lines. This effect was quantitatively confirmed with Monte Carlo simulations. Furthermore, with ASCA observations of the polar V834 Centauri, this collimation effect was clearly detected as a rotational modulation of the equivalent width of the Fe K emission line. The extremely strong emission lines mentioned above can be explained consistently by our interpretation. Combining this effect with other X-ray information, the geometry and plasma parameters in the accretion column were determined.
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X-RAY ASTRONOMY 599 959-962 2001年 査読有りThe Galactic ridge X-ray emission (GRXE) is an enhanced X-ray emission along the Galactic plane, whose origin still remains unknown. The GRXE was studied for the first time in the energy band of 0.5-10 keV with a spatial resolution of 3' by the ASCA Galactic plane survey which covers the spatial area of |l| less than or similar to 45degrees and |b| less than or similar to 0.4degrees almost uniformly. We determined the large scale distribution of the GRXE after eliminating discrete X-ray sources with a flux above 10(-12.5) ergs cm(-2) s(-1) and revealed that the volume emissivity of the GRXE is highly concentrated within the 4 kpc arm. We resolved 163 discrete X-ray sources by imaging analysis and obtained the LogN-LogS relations of those sources. In the hard (2-10 keV) band, the slope of the LogN-LogS relation is significantly smaller than 1. Considering a scale height of the Galactic plane covered by the ASCA Galactic plane survey, we conclude that the slope of the LogN-LogS relation represents that the spatial distribution of the sources has a scale height as small as 10 pc, that the sources are distributed in arm-like structures, and/or that the relation reflects the luminosity function rather than the spatial distribution. We analyzed small-scale spatial intensity fluctuation of the GRXE after subtracting the large scale variations and the contributions of resolved discrete sources. The residual small-scale fluctuation is found to remain significantly over the photon-counting Poisson fluctuation. However, in the 2-10 keV band, the amplitude can be explained by the fluctuation of the cosmic X-ray background coming through the Galactic interstellar medium. From this, we can obtain a strong constraint to a flux and a number density of discrete sources if we are to explain the GRXE with a sum of discrete sources; more than 10(7) sources with the luminosity smaller than 10(31) ergs s(-1) must exist in the Galaxy. This source number density is larger by three orders of magnitude than that of CVs in the solar neighborhood, which would be a plausible candidate for the discrete source origin. Thus, We conclude that the diffuse emission origin should be much more probable even if it has large problems.
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ASTROPHYSICAL JOURNAL 534(2) L181-L184 2000年5月 査読有りA new pulsating X-ray source, AX J183220-0840, with a 1549.1 s period was discovered at R.A. = 18(h)32(m)20(s) and decl, = -8 degrees 40'30 " (J2000, with an uncertainty of 0'.6) during an ASCA observation on the Galactic plane. The source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux of 1.1 x 10(-11) ergs cm(-2) s(-1) and a pulsation period of 1549.1 +/- 0.4 s were consistently obtained from these two observations. The X-ray spectrum was represented by a flat, absorbed power law with a photon index of Gamma similar or equal to 0.8 and an absorption column density of N-H similar or equal to 1.3 x 10(22) cm(-2). Also, a signature of iron K-shell line emission with a centroid of 6.7 keV and an equivalent width of approximately 450 eV was detected. From the pulsation period and the iron-line feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a complexly absorbed thermal spectrum with a temperature of about 10 keV.
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BROAD BAND X-RAY SPECTRA OF COSMIC SOURCES 25(3-4) 589-592 2000年 査読有りAn X-ray study was made to examine whether some part of the soft X-ray background is coming from hot gas halo that might be associated with the Local Group. For this purpose, four consecutive pointings were made with ASCA onto a general sky region in between M31 and M33, which is thought to be close to the direction of the Local Group Center. After removing point sources with 2-10 keV fluxes exceeding 2 x 10(-13) erg s(-1) cm(-2), the X-ray background brightness in this direction was quantified in terms of two (steep and fiat) power-law components. By comparing the soft-component brightness with that in another blank sky region near the equatorial pole, any excess soft X-ray background coming from this M31/M33 region was determined to be less than or equal to 1.27 x 10(-8) erg s(-1) cm(-2) str(-1). Assuming a Raymond-Smith type spectrum of temperature 0.3-1.2 keV and a beta-model density distribution for the X-ray halo, the central plasma density No and core radius R-c for the beta model was constrained as [N-0/10(-3) cm(-3)](2) [R-c/100 kpc] less than or equal to 5.80x10(-3). The implied plasma column density is too low to cause any noticeable quardrupole anisotropy in the cosmic microwave backbround. (C) 2000 COSPAR. Published by Elsevier Science Ltd.
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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 46(3) 371-376 1999年6月 査読有りASTRO-E Hard X-ray Detector (HXD) is characterized by well-type phoswich counters[1] in a compound-eye configuration which reduce the detector background to lower level than any other past hard X-ray mission. When operating in Low Earth Orbit, the expected background of the HXD is an order of 10(-5) counts/s/kev/cm(2), mainly caused from the radioactivity induced within the detector materials by geomagnetically trapped protons. Results are presented from measurements of induced radioactivity in two phoswich scintillators, GSO (Gd2SiO5:Ce 0.5% mol) and EGO (Bi4Ge3O12), irradiated by mono-energetic protons at an accelerator facility. Radiation transport computer codes are used to build the detector response functions for emissions from decays of spallation products. Based on the comparison between experimental and simulation results, the activation background level of HXD in the orbit is estimated.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 51(1) 39-44 1999年2月 査読有りA new transient X-ray source, AX J1842.8-0423, was discovered with ASCA in 1996 October in the Scutum arm region. The source exhibited an absorption-corrected 2-10 keV flux of 5.2 x 10(-12) erg s(-1) cm(-2) with insignificant intensity variability. The continuous spectrum is approximated by a power-law of photon index 2.9, absorbed by a hydrogen column of NH similar to 5 X 10(22) Cm-2 The spectrum also exhibits the Fe-K emission line with an extremely large equivalent width of similar to 4000 eV, of which the centroid energy is similar to 6.8 keV. The overall spectrum can be reproduced by a thin-thermal plasma-emission model having a temperature of similar to 5.1 keV, on the condition that the heavy-element abundance is allowed to increase to 3.0(-0.9)(+4.3) solar abundance. The source was undetectable in a previous observation in 1993 October, as well as in a subsequent observation in 1996 April. The overall source behavior is thus quite peculiar, but may be explained in terms of a close binary involving a magnetized white dwarf viewed from pole-on inclination, where the unusually strong Fe-K line may be the result of resonant scattering of line photons.
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IEEE Nuclear Science Symposium and Medical Imaging Conference 1 227-232 1999年ASTRO-E Hard X-ray Detector (HXD) is characterized by well-type phoswich counters in a compound-eye configuration which reduce the X-ray and non X-ray background to lower level than any other past hard X-ray missions. When operating in Low Earth Orbit, the expected background of the HXD is an order of 10-5[counts/s/keV/cm2], mainly caused from the radioactivity induced within the detector materials by nuclear interactions with geomagnetically trapped protons. Results are presented from measurements of induced radioactivity in two phoswich scintillators, GSO and BGO, irradiated by mono-energetic protons at an accelerator facility. Radiation transport computer codes are used to build the detector response functions against emissions from decays of spallation products. Based on the comparison of experimental and simulation results, the activation background level of HXD in the orbit is estimated.
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ASTRONOMISCHE NACHRICHTEN 320(4-5) 377-377 1999年 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 49(3) L7-L11 1997年6月 査読有りWe report on the ASCA results of a featureless X-ray spectrum from RX J1713.7-3946, a new shell-like SNR discovered with the ROSAT all-sky survey. The northwest part of RX J1713.7-3946 was in the field of the ASCA Galactic Plane Survey Project, and was found to exhibit a shell-like structure. The spectrum, however, shows neither line emission nor any signature of a thermal origin. Instead, a power-law model with a photon index of 2.4-2.5 gives a reasonable fit to the spectrum, suggesting a non-thermal origin. Together with the similarity to SN 1006, we propose that RX J1713.7-3946 is the second example, after SN 1006, of synchrotron X-ray radiation from a shell of SNRs. Since the synchrotron X-rays suggest the existence of extremely high energy charged particles in the SNR shell, our discovery should have a strong impact on the origin of cosmic X-rays.
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Monthly Notices of the Royal Astronomical Society 287(3) 651-662 1997年We present the results of high-energy resolution X-ray spectroscopy of AM Herculis (Her) carried out with ASCA on 1993 September. Owing to the high sensitivity of the solid-state imaging spectrometer (SIS) down to ∼ 0.4 keV, we have detected the Wien tail of the soft blackbody component during the rotational maximum phase. The rotational intensity modulation of the soft blackbody and the hard bremsstrahlung are in phase, indicating that they originate from the same accretion pole. Using Extreme Ultraviolet Explorer (EUVE) data taken simultaneously with ASCA, we find the soft excess to be as great as 17 ± 7 if we approximate the soft component observed by EUVE and ASCA with a single-temperature blackbody. From the blackbody luminosity, the fractional area is determined to be of order 10-5. The spectrum during the rotational minimum phase is characterized by a strong fluorescent iron Kα emission with an equivalent width of ∼1 keV. This indicates that the hard X-ray emission during the rotational minimum phase consists entirely of scattered emission, and geometrical consideration suggests the pre-shock accretion column as a possible scattering site. The observed spectrum is softer than would be expected from optically thick scattering matter, and suggests that the column density of the scattering matter is not more than ∼ 1023 cm-2. The high-energy resolution of the SIS has enabled us to resolve the emission lines from hydrogenic and He-like Kα emission lines from iron. However, the emission lines from the other light elements are generally weaker than those seen in EX Hya, in which a significant post-shock cooling flow is found from the ASCA observation. The spectrum of AM Her in the bright phase is, on the other hand, consistent with a single-temperature optically thin thermal plasma spectrum with the abundance of 0.4-0.1+0.2 ⊙. These facts indicate that most of the cooling part of the post-shock plasma is hidden from the observer in AM Her. A possible interpretation is that the post-shock plasma is highly inhomogeneous, and it penetrates the photosphere before it has cooled significantly. © 1997 RAS.
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Astrophysical Journal 491(2) 638-652 1997年 査読有りX-ray spectra of the Galactic ridge emission in the Scutum arm region have been obtained with ASCA GIS and SIS in the energy range 0.7-10 keV. The observed spectra are basically of thermal emission from thin hot plasmas, and individual K emission lines from helium-like Mg, Si, S, and Fe ions are confirmed in both the GIS and SIS spectra. This means that the Galactic ridge X-ray emission cannot be explained by a single-temperature ionization-equilibrium plasma model. It cannot, however, be reproduced even if a nonequilibrium ionization model is introduced thus multiple plasma components are required. The GIS spectra are fairly well fitted by a double-temperature nonequilibrium ionization plasma model with temperatures of kT ∼ 0.8 keV and kT ∼7 keV. The softer component is found to be in an extremely low ionization state, with net ∼ 109 cm-3 s, while the harder component is in a relatively high ionization state, though not yet in a full equilibrium. The GRXE properties obtained with the GIS are carefully reexamined by the highly resolved spectral-line features with the SIS. The soft and hard components are absorbed by equivalent hydrogen columns of 0.7 × 1022 cm-2 and 4.6 × 1022 cm-2, respectively. The surface brightness of the soft and hard components at b ∼ 0° are estimated to be 1.9 × 10-6 and 5.3 × 10-7 ergs cm-2 s-1 sr-1 respectively, both in the 0.5-10 keV band. The surface brightness of the softer component extends toward significantly higher (∼2°) Galactic latitudes than the harder component, although their actual scale heights may be similar at ∼100 pc if the differences in their observable depths are taken into account. Spectral properties of the two components are seen to depend on the latitude the most noticeable effect is a rapid decrease in the Fe K line equivalent width seen in the hard component. Attempts are made to interpret the two components in terms of diffuse hot plasmas filling the interstellar space. © 1997. The American Astronomical Society. All rights reserved.
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ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES 120(4) C645-C648 1996年12月 査読有りThe Hard X-ray Detector (HXD) is one of three instruments on the fifth Japanese X-ray astronomy satellite, ASTRO-E, scheduled for launch in 2000. The HXD consists of a 4x4 = 16 modular assembly of identical counters, each consisting of a combination of YAP(or GSO)/BGO well-type phoswich counters and silicon PIN diodes. The field of view of the detector for high energy photons is restricted to 4 degrees x 4 degrees by active collimators made of BGO and the fov for low energy photons is restricted to 0.5 degrees x 0.5 degrees by the fine passive collimators made of phosphor bronze. The detector is characterized by a low background reaching severalx10(-6) c/s/cm(2)/keV. Combined with the other two instruments for soft X-ray observations (0.5-12 keV), the ASTRO-E mission will cover the entire range of soft and hard X-rays with the highest sensitivity ever achieved. Furthermore, thick EGO counters which surround the 4x4 matrix of well-type phoswich counters act as a gamma-ray burst detector in the energy band of 100-2000 keV.
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1995 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE RECORD, VOLS 1-3 224-228 1996年 査読有り
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Proceedings of SPIE - The International Society for Optical Engineering 2806 314-328 1996年 査読有り
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Publications of the Astronomical Society of Japan 48(2) L15-L20 1996年 査読有りWe report on the ASCA results of hard X-ray imaging and spectroscopic observations of the galactic ridge (the Scutum arm region). The bulk of X-rays in the field of view could not be explained by an integrated emission of resolved sources, indicating that most of the galactic-ridge X-rays are due to a diffuse thin hot plasma. The X-ray luminosity of discrete sources contributing to the galactic-ridge emission was estimated to be less than -2x1033 erg s-1 in the 2-10 keV energy band. Emission lines from helium-like Si, S, and Fe ions were confirmed in the spectra, which means that the galactic ridge X-ray emission can not be explained by a single temperature ionization equilibrium plasma model. We give some constraints on the origin of the galactic-ridge emission.
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Proceedings of SPIE - The International Society for Optical Engineering 2518 2-12 1995年The fourth Japanese x-ray astronomy satellite, ASCA, carries two imaging gas scintillation proportional counters (GIS) on its focal plane. Extensive ground calibration has established its position resolution to be 0.5 mm and FWHM energy resolution to be 8.0% both at 6 keV. When combined with the x-ray telescope, a sensitivity range becomes 0.7 - 10 keV. These properties have been confirmed through in-orbit calibrations. The in-orbit background of the GIS has been confirmed to be as low as (5 - 7) × 10 -4 c s -1cm -2keV -1 over the 1 - 10 keV range. The long-term detector gain is stable within a few % for two years. Gain dependence on the position and temperature has been calibrated down to 1%. The overall energy response is calibrated very accurately. Thus the GIS is working as an all-round cosmic x-ray detector.
MISC
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月13日
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月13日
主要な講演・口頭発表等
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第67回宇宙科学技術連合講演会 2023年10月19日 日本航空宇宙学会This paper shows the system design and development status of the data handling system, ISC(DH), for the Martian Moons eXploration (MMX) mission. ISC(DH) consists of SMU (Spacecraft Management Unit), MDP (Mission Data Processor) and PDCU (Power Distribution Control Unit). System overviews and configuration are described.
共同研究・競争的資金等の研究課題
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日本学術振興会 科学研究費助成事業 2007年 - 2009年
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日本学術振興会 科学研究費助成事業 2004年 - 2005年
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日本学術振興会 科学研究費助成事業 2002年 - 2004年
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日本学術振興会 科学研究費助成事業 2002年 - 2002年
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日本学術振興会 科学研究費助成事業 2000年 - 2001年
