研究者業績
基本情報
- 所属
- 埼玉大学大学院 理工学研究科 教授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 特任教授
- 学位
- 修士（理学）(東京大学)博士（理学）(東京大学)
- J-GLOBAL ID
- 200901083726265608
- researchmap会員ID
- 1000161587
- 外部リンク
研究キーワード
14学歴
6-
- 1993年
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- 1990年
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- 1988年
委員歴
2-
2020年11月 - 現在
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2009年1月 - 2013年5月
受賞
4-
2007年
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2007年
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1999年
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1999年
論文
165-
The Astrophysical Journal 2023年8月1日
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Journal of Geophysical Research: Space Physics 128(2) 2023年2月21日 査読有り
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Nature Astronomy 6(12) 1364-1375 2022年12月12日 査読有り
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Nature Astronomy 7(1) 80-87 2022年12月8日 査読有り
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Journal of Low Temperature Physics 209(5-6) 1088-1096 2022年9月19日 査読有り
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 2022年8月31日 査読有り
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Monthly Notices of the Royal Astronomical Society, 512(4) 5995-6006 2022年6月 査読有りAbstract The far infrared counterpart of hot spot D, the terminal hot spot of the eastern jet hosted by the radio galaxy Cygnus A, is detected with Herschel Aperture photometery of the source performed in 5 photometric bands covering the wavelength range of 70–350 μm. After removing the contamination from another nearby hot spot, E, the far-infrared intensity of hot spot D is derived as 83 ± 13 and 269 ± 66 mJy at 160 and 350 μm, respectively. Since the far-infrared spectrum of the object smoothly connects to the radio one, the far-infrared emission is attributed to the synchrotron radiation from the radio-emitting electron population. The radio-to-near-infrared spectrum is confirmed to exhibit a far-infrared break feature at the frequency of $\nu _\mathrm{br}=2.0^{+1.2}_{-0.8} \times 10^{12}$ Hz. The change in energy index at the break (Δα = 0.5) is interpreted as the impact of radiative cooling on an electron distribution sustained by continuous injection from diffusive shock acceleration. By ascribing the derived break to this cooling break, the magnetic field, B, in the hot spot is determined as a function of its radius, R within a uniform one-zone model combined with the strong relativistic shock condition. An independent B-R constraint is obtained by assuming the X-ray spectrum is wholly due to synchrotron-self-Compton emission. By combining these conditions, the two parameters are tightly determined as B = 120–150 μG and R = 1.3–1.6 kpc. A further investigation into the two conditions indicates the observed X-ray flux is highly dominated by the synchrotron-self-Compton emission.
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Publications of the Astronomical Society of Japan 2022年5月 査読有り
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International Journal of Modern Physics D, 31(2) id 2230001 2022年1月 査読有り招待有り筆頭著者
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Journal of Astronomical Telescopes, Instruments, and Systems 7(03) 2021年7月1日 査読有り
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Journal of Geophysical Research: Space Physics 126(4) 2021年4月 査読有り
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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
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The Astrophysical Journal 899(1) 17-17 2020年8月7日 査読有り
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The Astrophysical Journal 891(2) 126-126 2020年3月12日 査読有り
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年© 2020 SPIE The X-Ray Imaging and Spectroscopy Mission, XRISM, is currently scheduled to launch in 2022 with the objective of building on the brief, but significant, successes of the ASTRO-H (Hitomi) mission in solving outstanding astrophysical questions using high resolution X-ray spectroscopy. The XRISM Science Operations Team (SOT) consists of the JAXA-led Science Operations Center (SOC) and NASA-led Science Data Center (SDC), which work together to optimize the scientific output from the Resolve high-resolution spectrometer and the Xtend wide-field imager through planning and scheduling of observations, processing and distribution of data, development and distribution of software tools and the calibration database (CaldB), support of ground and in-flight calibration, and support of XRISM users in their scientific investigations of the energetic universe. Here, we summarize the roles and responsibilities of the SDC and its current status and future plans. The Resolve instrument poses particular challenges due to its unprecedented combination of high spectral resolution and throughput, broad spectral coverage, and relatively small field-of-view and large pixel-size. We highlight those challenges and how they are being met.
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年© 2020 SPIE The XRISM is the X-ray astronomical mission led by JAXA/NASA/ESA with international participation, plan to be launched in 2022 (Japanese fiscal year), to quickly recover the high-resolution X-ray spectroscopy of astrophysical objects using the micro-calorimeter array after the failure of Hitomi. To enhance the scientific outputs of the mission, the Science Operations Team (SOT) is structured independently from the instrument teams and the mission operation team (MOT). The responsibilities of the SOT are summarized into four categories: 1) Guest observer program and data distributions, 2) Distribution of the analyses software and calibration database, 3) Guest observer supporting activities, and 4) the performance verification and optimization (PVO) activities. Before constructing the Operations Concept of the XRISM mission, the lessons on the Science Operations learned from the past Japanese X-ray missions (ASCA, Suzaku, and Hitomi) are reviewed, and 16 kinds of lessons are identified by the above categories: lessons on the importance of avoiding nonpublic (“animal”) tools, coding quality of public tools both on the engineering viewpoint and the calibration accuracy, tight communications with instrument teams and operations team, well-defined task division between scientists and engineers etc. Among these lessons, a) importance of the early preparations of the operations from the ground stage, b) construction of the independent team for the Science Operations from the instrument developments, and c) operations with well-defined duties by appointed members are recognized as the key lessons for XRISM. Then, i) the task division between the Mission and Science Operations and ii) the subgroup structure within the XRISM team are defined in detail as the XRISM Operations Concept. Then, following the Operations Concept, the detail plan of the Science Operations is designed as follows. The Science Operations tasks are shared among Japan, US, and Europe operated by three centers, the Science Operations Center (SOC) at JAXA, the Science Data Center (SDC) at NASA, and European Space Astronomy Centre (ESAC) at ESA. The SOT is defined as a combination of the SOC and SDC; the SOC is designed to perform tasks close to the spacecraft operations, such as spacecraft planning of science targets, quick-look health checks, pre-pipeline data processing, etc., and the SDC covers the tasks on the data calibration processing (pipeline processing), maintenance of the analysis tools etc. The data-archive and users-support activities are planned to be covered both by the SOC and SDC. Finally, the details of the Science Operations tasks and the tools for the Science Operations are also described in this paper. This information would be helpful for a construction of Science Operations of future X-ray missions.
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The Astrophysical Journal 884(2) L58-L58 2019年10月21日 査読有り
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Publications of the Astronomical Society of Japan 71(4) 2019年8月1日We have systematically studied the spectral properties of 302 localized gamma-ray bursts (GRBs) observed by the Suzaku wide-band all-sky monitor (WAM) from 2005 August to 2010 December. The energy spectra in the 100-5000 keV range integrated over the entire emission and the 1 s peak were fitted by three models: a single power law, a power law with an exponential cutoff (CPL), and the GRB Band function (GRB). Most of the burst spectra were well fitted by a single power law. The average photon index α was -2.11 and -1.73 for long and short bursts, respectively. For the CPL and GRB models, the low-energy and high-energy photon indices (α and β) for the entire emission spectra were consistent with previous measurements. The averages of the α and β were -0.90 and -2.65 for long-duration GRBs, while the average α was -0.55 and the β was not well constrained for short-duration GRBs. However, the average peak energy Epeak was 645 and 1286 keV for long- and short-duration GRBs respectively, which are higher than previous Fermi/GBM measurements (285 keV and 736 keV). The α and Epeak of the 1 s peak spectra were larger, i.e., the spectra were harder, than the total fluence spectra. Spectral simulations based on Fermi-GBM results suggest that the higher Epeaks measured by the Suzaku WAM could be due to detector selection bias, mainly caused by the limited energy range above 100 keV.
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The Astrophysical Journal 878(1) 2019年6月12日 査読有りWe present the first radio polarimetric observations of a fast-rising blue optical transient, AT2018cow. Two epochs of polarimetry with additional coincident photometry were performed with the Atacama Large Millimeter/submillimeter Array. The overall photometric results based on simultaneous observations in the 100 and 230 GHz bands are consistent with the nonthermal radiation model reported by Ho et al. and indicate that the spectral peaks (similar to 110 GHz at the first epoch and similar to 67 GHz at the second epoch) represent the synchrotron self-absorption frequency. The non-detection of linear polarization with <0.15% in the 230 GHz band at the phase when the effect of synchrotron self-absorption was quite small in the band may be explained by internal Faraday depolarization with high circumburst density and strong magnetic field. This result supports the stellar explosion scenario rather than the tidal disruption model. The maximum energy of accelerating particles at the shocks of AT2018cow-like objects is also discussed.
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Journal of Low Temperature Physics 1-7 2018年3月8日 査読有りThe pulse shape processor is the onboard digital electronics unit of the X-ray microcalorimeter instrument—the soft X-ray spectrometer—onboard the Hitomi satellite. It processes X-ray events using the optimum filtering with limited resources. It was operated for 36 days in orbit continuously without issues and met the requirement of processing a (Formula presented.) event rate during the observation of bright sources. Here, we present the results obtained in orbit, focusing on its performance as the onboard digital signal processing unit of an X-ray microcalorimeter.
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日The soft x-ray spectrometer (SXS) was a cryogenic high-resolution x-ray spectrometer onboard the Hitomi (ASTRO-H) satellite that achieved energy resolution of 5 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from room temperature to the ADR heat sink was composed of two-stage Stirling cryocoolers, a 4He Joule-Thomson cryocooler, and superfluid liquid helium and was installed in a dewar. It was designed to achieve a helium lifetime of more than 3 years with a minimum of 30 L. The satellite was launched on February 17, 2016, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the helium tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and the cryocoolers.
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Publications of the Astronomical Society of Japan 70(2) 2018年 査読有りThe X-Ray Spectrometer (XRS) instrument of Suzaku provided the first measurement of the non-X-ray background (NXB) of an X-ray calorimeter spectrometer, but the data set was limited. The Soft X-ray Spectrometer (SXS) instrument of Hitomi was able to provide a more detailed picture of X-ray calorimeter background, with more than 360 ks of data while pointed at the Earth, and a comparable amount of blank-sky data. These data are important not only for analyzing SXS science data, but also for categorizing the contributions to the NXB in X-ray calorimeters as a class. In this paper, we present the contributions to the SXS NXB, the types and effectiveness of the screening, the interaction of the screening with the broad-band redistribution, and the residual background spectrum as a function of magnetic cut-off rigidity. The orbit-averaged SXS NXB in the range 0.3-12 keV was 4 x 10(-2) counts s(-1) cm(-2). This very low background in combination with groundbreaking spectral resolution gave SXS unprecedented sensitivity to weak spectral lines.
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 011218 2018年1月1日 査読有りThe soft x-ray spectrometer (SXS) instrument was launched aboard the Astro-H (Hitomi) observatory on February 17, 2016. The SXS is based on a high-sensitivity x-ray calorimeter detector system that has been successfully deployed in many ground and suborbital spectrometers. The instrument was to provide essential diagnostics for nearly every class of x-ray emitting objects from the atmosphere of Jupiter to the outskirts of galaxy clusters, without degradation for spatially extended objects. The SXS detector system consisted of a 36-pixel cryogenic microcalorimeter array operated at a heat sink temperature of 50 mK. In preflight testing, the detector system demonstrated a resolving power of better than 1300 at 6 keV with a simultaneous bandpass from below 0.3 keV to above 12 keV with a timing precision better than 100 μs. In addition, a solid-state anticoincidence detector was placed directly behind the detector array for background suppression. The detector error budget included the measured interference from the SXS cooling system and the spacecraft. Additional margin for on-orbit gain stability and on-orbit spacecraft interference were also included predicting an on-orbit performance that meets or exceeds the 7-eV FWHM at 6-keV requirement. The actual on-orbit spectral resolution was better than 5 eV FWHM at 6 keV, easily satisfying the instrument requirement. Here, we discuss the actual on-orbit performance of the SXS detector system and compare this to performance in preflight testing and the on-orbit predictions. We will also discuss the on-orbit gain stability, additional on-orbit interference, and measurements of the on-orbit background.
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JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS 4(1) 2018年1月 査読有りFast timing capability in x-ray observation of astrophysical objects is one of the key properties for the ASTRO-H (Hitomi) mission. Absolute timing accuracies of 350 or 35 mu s are required to achieve nominal scientific goals or to study fast variabilities of specific sources. The satellite carries a GPS receiver to obtain accurate time information, which is distributed from the central onboard computer through the large and complex SpaceWire network. The details of the time system on the hardware and software design are described. In the distribution of the time information, the propagation delays and jitters affect the timing accuracy. Six other items identified within the timing system will also contribute to absolute time error. These error items have been measured and checked on ground to ensure the time error budgets meet the mission requirements. The overall timing performance in combination with hardware performance, software algorithm, and the orbital determination accuracies, etc. under nominal conditions satisfies the mission requirements of 35 mu s. This work demonstrates key points for space-use instruments in hardware and software designs and calibration measurements for fine timing accuracy on the order of microseconds for midsized satellites using the SpaceWire (IEEE1355) network. (c) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日 査読有り© The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. We summarize all of the in-orbit operations of the soft x-ray spectrometer (SXS) onboard the ASTRO-H (Hitomi) satellite. The satellite was launched on February 17, 2016, and the communication with the satellite ceased on March 26, 2016. The SXS was still in the commissioning phase, in which the set-ups were progressively changed. This paper is intended to serve as a concise reference of the events in orbit in order to properly interpret the SXS data taken during its short lifetime and as a test case for planning the in-orbit operation for future microcalorimeter missions.
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems vol.4 011217 2018年1月 査読有り
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The Astrophysical Journal 850(2) 193-193 2017年12月1日 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 69(3) 2017年6月 査読有りWe will review results for gamma-ray bursts (GRBs) and soft gamma repeaters (SGRs), obtained from the Suzaku Wide-band All-sky Monitor (WAM) which operated for about 10 years from 2005 to 2015. The WAM is a BGO (bismuth germanate: Bi4Ge3O12) lateral shield for the Hard X-ray Detector (HXD),used mainly for rejecting its detector background, but it also works as an all-sky monitor for soft gamma-ray transients in the 50-5000 keV range thanks to its large effective area (similar to 600 cm(2) at 1MeV for one detector) and wide field of view (about half of the entire sky). The WAM actually detected more than 1400 GRBs and 300 bursts from SGRs, and this detection number is comparable to that of other GRB-specific instruments. Based on the 10 years of operation, we describe timing and spectral performance for short GRBs, weak GRBs with high redshifts, and time-resolved pulses with good statistics.
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ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 229(2) 2017年4月 査読有りInterPlanetary Network (IPN) data are presented for the gamma-ray bursts in the second Fermi Gamma-Ray Burst Monitor (GBM) catalog. Of the 462 bursts in that catalog between 2010 July 12 and 2012 July 11, 428, or 93%, were observed by at least 1 other instrument in the 9-spacecraft IPN. Of the 428, the localizations of 165 could be improved by triangulation. For these bursts, triangulation gives one or more annuli whose half-widths vary between about 2 3 degrees and 16 degrees, depending on the peak flux, fluence, time history, arrival direction, and the distance between the spacecraft. We compare the IPN localizations with the GBM 1s, 2s, and 3s error contours and find good agreement between them. The IPN 3s error boxes have areas between about 8 square arcminutes and 380 square degrees, and are an average of 2500 times smaller than the corresponding GBM 3s localizations. We identify four bursts in the IPN/ GBM sample whose origins were given as "uncertain," but may in fact be cosmic. This leads to an estimate of over 99% completeness for the GBM catalog.
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JOURNAL OF LOW TEMPERATURE PHYSICS 184(1-2) 498-504 2016年7月 査読有りCalorimetric X-ray detectors are very sensitive to their environment. The boundary conditions can have a profound effect on the gain including heat sink temperature, the local radiation temperature, bias, and the temperature of the readout electronics. Any variation in the boundary conditions can cause temporal variations in the gain of the detector and compromise both the energy scale and the resolving power of the spectrometer. Most production X-ray calorimeter spectrometers, both on the ground and in space, have some means of tracking the gain as a function of time, often using a calibration spectral line. For small gain changes, a linear stretch correction is often sufficient. However, the detectors are intrinsically non-linear and often the event analysis, i.e., shaping, optimal filters etc., add additional non-linearity. Thus for large gain variations or when the best possible precision is required, a linear stretch correction is not sufficient. Here, we discuss a new correction technique based on non-linear interpolation of the energy-scale functions. Using Astro-H/SXS calibration data, we demonstrate that the correction can recover the X-ray energy to better than 1 part in 10 over the entire spectral band to above 12 keV even for large-scale gain variations. This method will be used to correct any temporal drift of the on-orbit per-pixel gain using on-board calibration sources for the SXS instrument on the Astro-H observatory.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 2016年6月 査読有りWe report on the T-90 and T-50 duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly bimodal in three energy ranges (50-120, 120-250, and 250-550 keV), but is unclear in the 550-5000 keV range, probably because of the limited sample size. The WAM durations decrease with energy according to a power-law index of -0.058(-0.034, +0.033). The hardness-duration relation reveals the presence of short-hard and long-soft GRBs. The short: long event ratio tends to be higher with increasing energy. We compared the WAM distribution with ones measured by eight other GRB instruments. The WAM T-90 distribution is very similar to those of INTEGRAL/SPI-ACS and Granat/PHEBUS, and least likely to match the Swift/BAT distribution. The WAM short: long event ratio (0.25:0.75) is much different from Swift/BAT (0.08:0.92), but is almost the same as CGRO/BATSE (0.25:0.75). To explain this difference for BAT, we examined three effects: BAT trigger types, energy dependence of the duration, and detection sensitivity diffe
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Publications of the Astronomical Society of Japan 68(SP1) S10-S10 2016年6月 査読有り
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日本物理学会講演概要集 71 367-367 2016年<p>2016年2月17日に打ち上げられたASTRO-H (ひとみ) 衛星に搭載された精密X線分光装置 SXS (Soft X-ray Spectrometer) は，40日弱の限られた期間ではあったが，軌道上において正常に動作し，天体のデータも取得できた．SXS の軌道上での性能について報告する．</p>
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Review of Scientific Instruments 87(11) 2016年 査読有り
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年The Soft X-ray Spectrometer (SXS) is a cryogenic high-resolution X-ray spectrometer onboard the ASTRO-H satellite, that achieves energy resolution better than 7 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator. The cooling chain from room temperature to the ADR heat sink is composed of 2-stage Stirling cryocoolers, a He-4 Joule-Thomson cryocooler, and superfluid liquid He, and is installed in a dewar. It is designed to achieve a helium lifetime of more than 3 years with a minimum of 30 liters. The satellite was launched on 2016 February 17, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the He tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and cryocoolers.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年The SXS instrument was launched aboard the Astro-H observatory on February 17, 2016. The SXS spectrometer is based on a high sensitivity x-ray calorimeter detector system that has been successfully deployed in many ground and sub-orbital spectrometers. The instrument was to provide essential diagnostics for nearly every class of x-ray emitting objects from the atmosphere of Jupiter to the outskirts of galaxy clusters, without degradation for spatially extended objects. The SXS detector system consisted of a 36-pixel cryogenic microcalorimeter array operated at a heat sink temperature of 50 mK. In pre-flight testing, the detector system demonstrated a resolving power of better than 1300 at 6 keV with a simultaneous band-pass from below 0.3 keV to above 12 keV with a timing precision better than 100 mu s. In addition, a solid-state anti-coincidence detector was placed directly behind the detector array for background suppression. The detector error budget included the measured interference from the SXS cooling system and the spacecraft. Additional margin for on-orbit gain-stability, and on-orbit spacecraft interference were also included predicting an on-orbit performance that meets or exceeds the 7 eV FWHM at 6 keV requirement. The actual on-orbit spectral resolution was better than 5 eV FWHM at 6 keV, easily satisfying the instrument requirement. Here we discuss the actual on-orbit performance of the SXS detector system and compare this to performance in pre-flight testing and the on-orbit predictions. We will also discuss the on-orbit gain stability, additional on-orbit interference, and measurements of the on-orbit background.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年 査読有りWe present the overall design and performance of the Astro-H (Hitomi) Soft X-Ray Spectrometer (SXS). The instrument uses a 36-pixel array of x-ray microcalorimeters at the focus of a grazing-incidence x-ray mirror Soft X-Ray Telescope (SXT) for high-resolution spectroscopy of celestial x-ray sources. The instrument was designed to achieve an energy resolution better than 7 eV over the 0.3-12 keV energy range and operate for more than 3 years in orbit. The actual energy resolution of the instrument is 4-5 eV as demonstrated during extensive ground testing prior to launch and in orbit. The measured mass flow rate of the liquid helium cryogen and initial fill level at launch predict a lifetime of more than 4 years assuming steady mechanical cooler performance. Cryogen-free operation was successfully demonstrated prior to launch. The successful operation of the SXS in orbit, including the first observations of the velocity structure of the Perseus cluster of galaxies, demonstrates the viability and power of this technology as a tool for astrophysics.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年 査読有りWe summarize all the in-orbit operations of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H (Hitomi) satellite. The satellite was launched on 2016/02/17 and the communication with the satellite ceased on 2016/03/26. The SXS was still in the commissioning phase, in which the setups were progressively changed. This article is intended to serve as a reference of the events in the orbit to properly interpret the SXS data taken during its short life time, and as a test case for planning the in-orbit operation for future micro-calorimeter missions.
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Publications of the Astronomical Society of Japan vol.67 46 2015年6月 査読有り
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Publications of the Astronomical Society of Japan vol.67 41 2015年6月 査読有り
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SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY 9144 2014年 査読有りWe present the development status of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H mission. The SXS provides the capability of high energy-resolution X-ray spectroscopy of a FWHM energy resolution of < 7eV in the energy range of 0.3 - 10 keV. It utilizes an X-ray micorcalorimeter array operated at 50 mK. The SXS microcalorimeter subsystem is being developed in an EM-FM approach. The EM SXS cryostat was developed and fully tested and, although the design was generally confirmed, several anomalies and problems were found. Among them is the interference of the detector with the micro-vibrations from the mechanical coolers, which is the most difficult one to solve. We have pursued three different countermeasures and two of them seem to be effective. So far we have obtained energy resolutions satisfying the requirement with the FM cryostat.
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SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY 9144 2014年 査読有りThe soft X-ray spectrometer (SXS) aboard ASTRO-H is equipped with dedicated digital signal processing units called pulse shape processors (PSPs). The X-ray microcalorimeter system SXS has 36 sensor pixels, which are operated at 50 mK to measure heat input of X-ray photons and realize an energy resolution of 7 eV FWHM in the range 0.3-12.0 keV. Front-end signal processing electronics are used to filter and amplify the electrical pulse output from the sensor and for analog-to-digital conversion. The digitized pulses from the 36 pixels are multiplexed and are sent to the PSP over lowvoltage differential signaling lines. Each of two identical PSP units consists of an FPGA board, which assists the hardware logic, and two CPU boards, which assist the onboard software. The FPGA board triggers at every pixel event and stores the triggering information as a pulse waveform in the installed memory. The CPU boards read the event data to evaluate pulse heights by an optimal filtering algorithm. The evaluated X-ray photon data (including the pixel ID, energy, and arrival time information) are transferred to the satellite data recorder along with event quality information. The PSP units have been developed and tested with the engineering model (EM) and the flight model. Utilizing the EM PSP, we successfully verified the entire hardware system and the basic software design of the PSPs, including their communication capability and signal processing performance. In this paper, we show the key metrics of the EM test, such as accuracy and synchronicity of sampling clocks, event grading capability, and resultant energy resolution.
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2014 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC) 2014年 査読有り
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SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY 9144 2014年 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 65(5) 2013年10月We present the results of X-ray mapping observations of the western radio lobe of the Fornax A galaxy, using the X-ray Imaging Spectrometer (XIS) onboard the Suzaku satellite with a total exposure time of 327 ks. The purpose of this study is to investigate the nature and spatial extent of the diffuse thermal emission around the lobe by exploiting the low and stable background of XIS. The diffuse thermal emission had been consistently reported in all previous studies of this region, but its physical nature and relation to the radio lobe had not been examined in detail. Using a data set covering the entire western lobe and the central galaxy NGC 1316, as well as comparison sets in the vicinity, we find convincingly the presence of thermal plasma emission with a temperature of similar to 1 keV in excess of conceivable background and contaminating emission (cosmic X-ray background, Galactic halo, intra-cluster gas of Fornax, interstellar gas of NGC 1316, and the ensemble of point-like sources). Its surface brightness is consistent with having a spherical distribution peaking at the center of the western lobe with a projected radius of similar to 12'. If the volume filling factor of the thermal gas is assumed to be unity, its estimated total mass amounts to similar to 10(10) M-circle dot, which would be similar to 10(2) times that of the central black hole, and comparable to that of the current gas mass of the host galaxy. Its energy density is comparable to or larger than those in the magnetic field and non-thermal electrons responsible for the observed radio and X-ray emission.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 65(5) 2013年10月 査読有りThe cluster of galaxies MS 1512.4+3647 (z = 0.372) was observed with Suzaku for 270 ks. Besides the Fe abundance, the abundances of Mg, Si, S, and Ni were separately determined for the first time in a medium redshift cluster (z > 0.3). The derived abundance pattern of MS 1512.4+3647 is consistent with those of nearby clusters, suggesting that the system has similar contributions from supernovae (SNe) Ia and SNe II to nearby clusters. The number ratio of SNe II to SNe Ia is similar to 3. The estimated total numbers of both SNe II and SNe Ia against the gas mass indicate similar correlations with those for the nearby clusters. The abundance results of MS 1512.4+3647 is consistent with the standard scenario that the SN II rate history roughly follows the star-formation history, which has a peak at 1 < z < 2, and then declines by about one order of magnitude toward z similar to 0. The similar number of SNe Ia to the nearby clusters suggests that the SN Ia rate declines steeply from z = 0.37 to z = 0, and/or SN Ia explosions occurred predominantly at larger redshifts.
MISC
364講演・口頭発表等
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The Astrophysical Journal Letters 2009年
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Publications of the Astronomical Society of Japan 2009年
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The Astrophysical Journal 2009年
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Publications of the Astronomical Society of Japan 2009年
共同研究・競争的資金等の研究課題
16-
日本学術振興会 科学研究費助成事業 2020年7月 - 2023年3月
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日本学術振興会 科学研究費助成事業 2015年4月 - 2018年3月
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日本学術振興会 科学研究費助成事業 2010年4月 - 2015年3月
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日本学術振興会 科学研究費助成事業 2008年 - 2008年
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日本学術振興会 科学研究費助成事業 2006年 - 2008年
