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 教授総合研究大学院大学 先端学術院 宇宙科学コース 教授東京工業大学 理学院 特定教授
- 学位
- 博士（理学）(東京大学)修士(東京大学)
- 研究者番号
- 20280555
- ORCID ID
https://orcid.org/0000-0002-2374-7073- J-GLOBAL ID
- 200901095989600566
- researchmap会員ID
- 1000363020
X線マイクロカロリメータを用いた極低温精密X線分光装置の開発に取り組み，2023年9月打ち上げのXRISM衛星に搭載されたResolve観測装置として実現しました．
研究指導のテーマとしては，(1) XRISM衛星による精密X線分光観測データを解析し，銀河団ガスの運動を調べて，宇宙の大規模構造形成過程の理解を深める，(2) 宇宙マイクロ波背景放射の偏光観測を目指すLiteBIRD衛星を見据えた実験的研究を行なう等．特定の自然現象について理解を深めると同時に，複雑な自然現象の背景にある物理法則に至る過程を，実験・解析手法とともにしっかりと身につけてもらいたいと考えています．
研究キーワード
6経歴
8-
2024年6月 - 現在
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2024年3月 - 現在
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2023年6月 - 2024年6月
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2023年6月 - 現在
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2008年4月 - 2023年5月
学歴
4-
1991年4月 - 1995年3月
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- 1995年
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1987年4月 - 1991年3月
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- 1991年
委員歴
2-
2009年4月 - 2011年3月
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2009年 - 2010年
受賞
2-
2010年
論文
155-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 520(1-3) 2004年
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 523(1-2) 2004年
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 520(1-3) 2004年
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 520(1-3) 2004年
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 520(1-3) 456-459 2004年We have developed multi-pixel TES microcalorimeters in order to realize high-energy resolution and X-ray imaging. A Sn absorber and a Bi absorber were formed on Si3N4 and SiO2 membrane using two-step exposure photolithography and electrodeposition. A FEM analysis was carried out to investigate the performance of the X-ray microabsorbers. In addition, a superconducting through-wafer interconnection was demonstrated considering the future X-ray imager using microcalorimeters. Detail of the fabrication techniques, characteristics and simulation results of two types of the microabsorbers, as well as those of the calorimeters are described. (C) 2003 Elsevier B.V. All rights reserved.
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PASJ : publications of the Astronomical Society of Japan 56(6) 939-957 2004年
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 520(1-3) 2004年
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Japanese journal of applied physics. Pt. 1, Regular papers & short notes 43(3) 1190-1195 2004年An X-ray microcalorimeter is a cryogenic energy-dispersive spectrometer, which has an energy resolution almost comparable to that of conventional wavelength-dispersive spectrometers. Using a transition edge sensor (TES) as a temperature sensor, the energy resolution can be further improved. We have developed a new method of achieving an array of TES microcalorimeters for the purpose of X-ray imaging. To achieve this, mushroom-shaped X-ray microabsorbers formed using electrodeposition were applied. The temperature of the TES, which is easily degraded by thermal diffusion, was kept sufficiently low throughout the process to achieve practical use. On the bases of this new method, a $2\times 2$ ($\times$ 4) array of TES microcalorimeters was fabricated and tested. A high energy resolution of 13.0 eV at 6 keV was achieved and the filling factor was improved to 83%. Although several issues still need to be investigated, we verified that our method is useful for fabricating a Ti–Au TES microcalorimeter array.
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Astrophysical Journal 605(2 I) 2004年
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Digest of Papers - Microprocesses and Nanotechnology 2003 - 2003 International Microprocesses and Nanotechnology Conference, MNC 2003 182-183 2003年 査読有りIn this paper we developed through-wafer interconnections using only a simple fabrication process. The interconnection was successfully transformed into the superconducting state. A current density of 13 cm/sup 2//mA was obtained in the superconducting state. We realize high energy-resolution X-ray imaging using the superconducting through-wafer interconnections.
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X-RAY AND GAMMA-RAY TELESCOPES AND INSTRUMENTS FOR ASTRONOMY, PTS 1 AND 2 4851 831-841 2003年We are developing a superconducting transition-edge sensor (TES) calorimeter for future Japanese X-ray astronomy missions (e.g. NeXT mission). The performance of our single pixel TES calorimeter is presented. We fabricated a Ti/Au (40 nm/110 nm) bilayer TES on a thin silicon-nitride membrane, which is adjusted to have a transition temperature of about 100 mK. The size of the TES is 500 mum x 500 mum, and 300 mum x 300 mum gold with a thickness of 300 nm is deposited with sputtering as an X-ray absorber. The TES calorimeter was installed in a dilution refrigerator operated at similar to 40 mK, with a combination of 400-series SQUID array as an ammeter. Collimated 5.9 keV X-rays (200 pm in diameter) from 55 Fe isotope were irradiated and X-ray pulses were obtained. Simultaneously with a fast falling time constant of 74.2 mus, the energy resolution of 6.6 +/- 0.4 eV was attained, while the baseline noise was 6.4 eV. The contents of the energy resolution are 5.1 eV of the excess noise, 3.3 eV of the readout noise, 1.6 eV of the pulse by pulse variation, and 1.9 eV of the intrinsic noise. The baseline noise are dominated by an unknown excess noise, which increases roughly in proportion to the inverse of the TES resistance. The pulse height is sensitive to the operating conditions, and the superconducting shield appears to have improved it by a factor of similar to 2. The calorimeter works fine over six months surviving five thermal cycles, even though it is kept in air.
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X-RAY AND GAMMA-RAY TELESCOPES AND INSTRUMENTS FOR ASTRONOMY, PTS 1 AND 2 4851 965-974 2003年We are developing a superconducting Transition-Edge Sensor (TES) calorimeter array. We adopt calorimeter multiplex in frequency domain to read signals from the calorimeter array with a small number of front-end electronics and wirings. We further utilize Calorimeter Bridge Biased by an AC Generator (CABBAGE) approach(1,2) to eliminate the AC carrier in the output. We tested the method using a TES calorimeter, which has a transition temperature of 390 mK. Because of the high operating temperature, energy resolution (DeltaE) of the calorimeter is limited to 200 eV at 5.9 keV even when it is biased with a DC current. We operated the calorimeter in CABBAGE circuit with 30 kHz sinusoidal bias and obtained DeltaE of 250 eV. We found that there remains a small-amplitude residual in the output even at the bridge balance point. The residual contains not only 30 kHz component but also odd-order harmonics. We consider that this is due to the variation of the TES resistor with the bias current. Some of the degradation of DeltaE from DC bias to AC bias can be explained by the fact that some of signal power is carried in the odd-order harmonics, which we did not utilize in the data reduction process. We also succeeded in operate the CABBAGE by 100 kHz, although DeltaE was degraded to 380 eV because of unstable bath temperature during the data acquisition and probably because of low response of the signal readout circuit at the frequency.
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Physica B: Condensed Matter 329-333(II) 2003年
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Astronomy and Astrophysics 411(2) 2003年
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Journal of Electroanalytical Chemistry 559 2003年
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LOW TEMPERATURE DETECTORS 605 235-238 2002年 査読有りFor the next generation of astronomical X-ray imaging detectors, arrays with large numbers of microstructures (similar to1000 pixels) will be required. To meet this requirement, a tin absorber for an X-ray microcalorimeter, which has a so-called "mushroom" shape, is fabricated by electrodeposition and polishing. This method enables the fabrication of a large number of arrayed microcalorimeters. Details of the fabrication process, the characteristics of the absorber and the fabricated microcalorimeters are reported.
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LOW TEMPERATURE DETECTORS 605 231-234 2002年A superconducting phase-transition microcalorimeter is a promising detector for high resolution X-ray spectroscopy. We are developing such a detector for future Japanese X-ray astronomy missions. In our design, a tin absorber is electrodeposited as a mushroom structure to achieve a high covering fraction. We have succeeded in detecting X-rays with the first model of our calorimeter with an electrodeposited absorber, though the energy resolution was limited due to residual resist. We are also developing a phase-transition microcalorimeter with a low transition temperature. We describe the results of these experiments, and discuss the limiting factors of their performance.
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LOW TEMPERATURE DETECTORS 605 313-316 2002年In order to realize a large format (e.g. similar to 32 x 32) calorimeter array, it is essential to multiplex calorimeter signals at cryogenic temperatures without losing signal to noise ratio. For this purpose we propose a brand-new readout method, the CABBAGE ((ca) under bar lorimeter (B) under bar ridge (B) under bar iased by an (A) under barC Generator) where an AC biased calorimeters are placed in resistance bridges. In this paper we first describe the principles of CABBAGE and investigate its response and noise.We propose the large format calorimeter array readout using CABBAGEs, and discuss the new TES microcalorimeter readout method without using SQUIDs.
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Astrophysical Journal 581(1 I) 2002年
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Superconductor Science and Technology 15(1) 2002年
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NEW CENTURY OF X-RAY ASTRONOMY 251 292-293 2001年 査読有りWe analyzed ASCA data of 28 luminous infrared galaxies including 16 ultraluminous infrared galaxies (ULIRGs) to study the nature of the AGN and to reveal the energy source of their far infrared luminosity. Our primary conclusion is that the circumnuclear starburst activity is the main energy source of most ULIRGs. We also found that the ULIRGs with unabsorbed AGN tend to have a narrow-line Seyfert I nucleus.
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NEW CENTURY OF X-RAY ASTRONOMY 251 516-517 2001年 査読有りWe describe the transmission calibration of the Astro-E XRS blocking filters. XRS was the prime instrument on board the Japanese-US ASTRO-E observatory which was lost due to a rocket failure. XRS's high spectral resolution makes us sensitive to fine structure in the X-ray absorption edges of the filters for the oxygen and aluminum edges around 0.5 and 1.5 keV. Thus, it is important that we measure these features on the ground. A spare XRS microcalorimeter is now being used for laboratory astrophysics at LLNL and it is hoped that future missions such as ASTRO-EII might carry similar detectors. We thus continue to calibrate the spare XRS optical blocking filters.
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NEW CENTURY OF X-RAY ASTRONOMY 251 534-535 2001年A superconducting phase-transition microcalorimeter is a promising detector for high resolution X-ray spectroscopy. We are developing such a detector for future Japanese X-ray astronomy missions. The outline and the status of our development are described.
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NEW CENTURY OF X-RAY ASTRONOMY 251 548-549 2001年Development of an X-ray microcalorimeter utilizing the superconducting transition edge sensor (TES) is under way. We fabricated a Ti-Au bilayer TES calorimeter on a sillicon wafer. A tin film of 0.5 x 0.5 x 0.015 mm was glued on it with epoxy as an absorber. Operating it at 100-200 mK, we successfully detected Mn Kalpha X-rays (5.9 keV) with the calorimeter, although the energy resolution was about 100 eV (FWHM).
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NEW CENTURY OF X-RAY ASTRONOMY 251 584-585 2001年A SQUID array amplifier and a 4-input SQUID array amplifier produced by SEIKO Instruments Inc. (SII) are used as readouts of our calorimeter system. Both achieve good performance with low noise (3-4 pA/rootHz). The 4-input SQUID array amplifier is a device that has recently been developed for multiplexing calorimeter signals, and is directly applicable to the AC multiplexing method. The performance of these SQUID array amplifiers is described.
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Monthly Notices of the Royal Astronomical Society 328(1) 2001年
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Astrophysical Journal 563(2 PART 2) L103-L106 2001年We present the X-ray energy spectrum of the lensed broad absorption line QSO H1413+117 (the Cloverleaf) at z = 2.56 observed with the Chandra X-ray observatory. We detected 293 photons in a 40 ks Advanced CCD Imaging Spectrometer (ACIS-S) observation. The X-ray image consists of four lensed image components, thus the photons are from the lensed QSO itself. The overall spectrum can be described with a power-law function heavily absorbed by neutral matter at a redshift consistent with the QSO redshift. This supports the idea that intrinsic absorption is significant for BAL QSOs. The spectral fit significantly (99% confidence) improves when we include an emission line. The centroid energy and intrinsic width (Gaussian sigma) of the line are 6.21 +/- 0.16 keV and 220(-130+)(270) eV (90% errors), respectively, in the QSO rest frame, assuming the absorbed power law as the continuum. The equivalent width of the line in the QSO rest frame is 960(-480)(+1400) eV. We suggest that the large equivalent width, the centroid energy, and the line broadness can be explained by iron K emission arising from X-ray reprocessing in the BAL flow, assuming it has a conical thin-sheet structure.
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日本物理學會誌 55(5) 340-348 2000年5月5日大多数の放射線検出器は,放射線によるイオン化によって生じた電荷を何らかの方法で電気信号に変換し,放射線を検出する.これに対しマイクロカロリメータは,放射線の吸収により生じた熱を温度変化として検出する.我が国5番目のX線天文衛星ASTRO-E衛星には,高い検出効率と高いエネルギー分解能を兼ね備えたX線分光検出器としてX線マイクロカロリメータが衛星としては史上初めて搭載されている.ここでは,X線マイクロカロリメータの動作原理,ASTRO-Eに搭載される検出器の構造,素子を動作温度60mKに冷却する冷却システムについて解説する.最後に,地上試験で実証された検出器の性能と,その性能(～10eVのエネルギー分解能)により期待される宇宙観測の新しい展開について述べる.
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 444(1) 2000年
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 444(1) 180-183 2000年By applying a transition edge sensor (TES) as the thermometer in an X-ray microcalorimeter, the intrinsic energy resolution is expected to be significantly improved. The extremely low intrinsic noise allows us to operate the calorimeter at temperatures as high as one can obtain by pumping liquid He-3 ( similar to 0.3 K) and still achieve an energy resolution comparable to conventional semiconducting microcalorimeters operating at similar to 60 mK (Delta E similar to 10 eV FWHM). Taking this advantage into account, we are developing a titanium/gold bilayer TES calorimeter fabricated on a silicon wafer. The transition temperature is about 0.5 K. We have succeeded in detecting X-ray photons from 3 to 25 keV, which proves that this TES calorimeter works in a wide energy range. The energy resolution is, however, still much worse than we expected - 550 eV (FWHM) at 5.9 keV. This is because the design parameters are not optimized. Several approaches to improve the performance are described. (C) 2000 Elsevier Science B.V. All rights reserved.
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Proceedings of SPIE - The International Society for Optical Engineering 4230 58-65 2000年An X-ray microcalorimeter that consists of an x-ray absorber to transfer the incident photon energy to the temperature rise, a temperature sensor to detect the temperature change and suspending beams for thermal isolation from the substrate have been fabricated. Titanium/Gold thin film transition edge sensor (TES) is used as the temperature sensor. We fabricated and tested the first prototype in the previous study and obtained the transition temperature of 0.52K, energy resolution of 550eV (FWHM) for 6keV radiation. These values were smaller than that of expected. We applied a Sn absorber and redesigned the microstructure of the x-ray microcalorimeter. Consequently, we have obtained 158eV at 5.9keV radiation of the energy resolution, which is about 4 times higher than that of the first prototype. This value is nearly equal to the conventional X-ray CCD. The highest energy resolution of the x-ray microcalorimeter of our design is estimated to similar to5 eV at the operating point of 0.2K. To realize such a good energy resolution calorimeter array, we are going to improve the sensitivity of the TES by optimizing the process condition. A Sn absorber formed by electroplating is also under evaluating simultaneously. It is necessary to fabricate uniform array structures.
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GALAXY INTERACTIONS AT LOW AND HIGH REDSHIFT (186) 341-344 1999年 査読有り
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EUV, X-RAY, AND GAMMA-RAY INSTRUMENTATION FOR ASTRONOMY X 3765 137-147 1999年 査読有りXRS is the microcalorimeter X-ray detector aboard the US-Japanese ASTRO-E observatory, which is scheduled to be launched in early 2000. XRS is a high resolution spectrometer- with less than 9 eV resolution at 3 keV and better than 14 eV resolution over its bandpass ranging from about 0.3 keV to 15 keV. Here we present the results of our first calibration of the XRS instrument. We describe the methods used to extract detailed information about the detection efficiency and spectral redistribution of the instrument. We also present comparisons of simulations and real data to test our detector models.
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EUV, X-RAY, AND GAMMA-RAY INSTRUMENTATION FOR ASTRONOMY X 3765 751-761 1999年 査読有りWe describe the transmission calibration of the Astro-E XRS blocking filters. The XRS instrument has five aluminized polymide blocking filters. These filters are located at thermal stages ranging from 200 K to 60 mK. They are each about 1000 Angstrom thick. XRS will have high energy resolution which will enable it to see some of the extended fine structure around the oxygen and aluminum K edges of these filters. Thus, we are conducting a high spectral resolution calibration of the filters near these energies to resolve out extended fine structure and absorption lines.
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EUV, X-RAY, AND GAMMA-RAY INSTRUMENTATION FOR ASTRONOMY X 3765 114-127 1999年 査読有りThe Astro-E High Resolution X-ray Spectrometer (XRS) was developed jointly by the NASA/Goddard Space Flight Center and the Institute of Space and Astronautical Science in Japan. The instrument is based on a new approach to spectroscopy, the X-ray microcalorimeter. This device senses the energies of individual X-ray photons as heat with extreme precision. A 32 channel array of microcalorimeters is being employed, each with an energy resolution of about 12 eV at 6 keV (the Fe-K region). This will provide spectral resolving power 10 times higher than any other non;dispersive X-ray spectrometer. The instrument incorporates a three stage cooling system capable of operating the array at 60 mK for about two years in orbit. The array sits at the focus of a grazing incidence conical mirror. The quantum efficiency of the microcalorimeters and the reflectivity of the X-ray mirror system combine to give high throughput over the 0.3-12 keV energy band. This new capability will enable the study of a wide range of high-energy astrophysical sources with unprecedented spectral sensitivity. This paper presents the basic design requirements and implementation of the XRS, and also describes the instrument parameters and performance.
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Astronomische Nachrichten 320(4-5) 246-247 1999年We made a series of ASCA observations of Ultra Luminous Infrared Galaxies (ULIRGs), to reveal the origin of their luminosities and to test a proposed evolutionary scenario of ULIRGs. We discovered embedded AGN in some galaxies, but the relative contribution of AGN activity to the total luminosity varies significantly from galaxy to galaxy and has no correlation with the evolutionary sequence as mergers.
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 436(1-2) 252-255 1999年We propose a new method to readout signals from a TES (superconducting Transition-Edge Sensor) calorimeter array with a single or a small number of SQUIDs, Since phonon noise and Johnson noise of a calorimeter can be made very small in these calorimeters, an increase in noise, thus a degradation of energy resolution by adding signals from plural pixels together at some stage of signal processing may be acceptable for some applications of TES calorimeters. We propose to use a SQUID with multi-input coils which will sense signals from different pixels. The input coils of a SQUID are electrically well-isolated from each other. The pixel that generates a signal can be identified by utilizing additional information, such as the pulse shape. We studied the feasibility of this method with analysis and simulations, and show for example, that a 16 x 16 pixel array can be read out with 16 SQUIDs. (C) 1999 Elsevier Science B.V. All rights reserved.
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Astronomische Nachrichten 320(4-5) 303-303 1999年
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Astrophysics and Space Science 266(1-2) 43-48 1999年
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Astronomische Nachrichten 320(4-5) 352-352 1999年
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GAMMA-RAY BURSTS, PTS 1 AND 2 (428) 435-440 1998年 査読有りASCA has made observations of the fields of six gamma-ray bursts after detections by BeppoSAX and RXTE. We summarize these observations.
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Astrophysical Journal 496(1 PART I) 1998年
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Astrophysical Journal 486(2 PART I) 1997年
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Monthly Notices of the Royal Astronomical Society 290(4) 1997年
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Monthly Notices of the Royal Astronomical Society 287(3) 1997年
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Astrophysical Journal 474(2 PART I) 1997年
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Publications of the Astronomical Society of Japan 49(2) 179-185 1997年We report on ASCA observations of two ultraluminous far-infrared galaxies, IRAS 15307+3252 and IRAS 20460+1925. An X-ray flux of 1.53 × 10 erg cm s in the 2-10 keV band was detected from IRAS 20460+1925. The continuous spectrum is well represented by a power law with a photon index of 1.99 and excess photoelectric absorption by a column of (2.6 ) × 10 cm in the rest frame. The spectrum also shows an iron K emission line with an equivalent width of 260 eV and a centroid energy of 6.36±0.08 keV in the rest frame. These spectral properties are consistent with those of Seyfert-2 galaxies, although the intrinsic 2-10 keV X-ray luminosity (corrected for absorption) of 1.20 × 10 erg s is high and close to that of quasars. No X-rays were detected from IRAS 15307+3252, and the upper limit to the X-ray flux is 7.2 × 10 erg cm s in the 2-10 keV band. However, the upper limit on the ratio of the X-ray flux to the far-infrared flux is not inconsistent with a source containing a highly obscured quasar. -12 -2 -1 +0.18 +0.29 22 -2 +145 44 -1 -14 -2 -1 -0.15 -0.32 -137
MISC
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Publications of the Astronomical Society of Japan 70(2) 2018年We report a Hitomi observation of IGR J16318-4848, a high-mass X-ray binary<br /> system with an extremely strong absorption of N_H~10^{24} cm^{-2}. Previous<br /> X-ray studies revealed that its spectrum is dominated by strong fluorescence<br /> lines of Fe as well as continuum emission. For physical and geometrical insight<br /> into the nature of the reprocessing material, we utilize the high spectroscopic<br /> resolving power of the X-ray microcalorimeter (the soft X-ray spectrometer;<br /> SXS) and the wide-band sensitivity by the soft and hard X-ray imager (SXI and<br /> HXI) aboard Hitomi. Even though photon counts are limited due to unintended<br /> off-axis pointing, the SXS spectrum resolves Fe K{\alpha_1} and K{\alpha_2}<br /> lines and puts strong constraints on the line centroid and width. The line<br /> width corresponds to the velocity of 160^{+300}_{-70} km s^{-1}. This<br /> represents the most accurate, and smallest, width measurement of this line made<br /> so far from any X-ray binary, much less than the Doppler broadening and shift<br /> expected from speeds which are characteristic of similar systems. Combined with<br /> the K-shell edge energy measured by the SXI and HXI spectra, the ionization<br /> state of Fe is estimated to be in the range of Fe I--IV. Considering the<br /> estimated ionization parameter and the distance between the X-ray source and<br /> the absorber, the density and thickness of the materials are estimated. The<br /> extraordinarily strong absorption and the absence of a Compton shoulder<br /> component is confirmed. These characteristics suggest reprocessing materials<br /> which are distributed in a narrow solid angle or scattering primarily with warm<br /> free electrons or neutral hydrogen.
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Publications of the Astronomical Society of Japan 70(6) 2018年We present the results from the Hitomi Soft Gamma-ray Detector (SGD)<br /> observation of the Crab nebula. The main part of SGD is a Compton camera, which<br /> in addition to being a spectrometer, is capable of measuring polarization of<br /> gamma-ray photons. The Crab nebula is one of the brightest X-ray / gamma-ray<br /> sources on the sky, and, the only source from which polarized X-ray photons<br /> have been detected. SGD observed the Crab nebula during the initial test<br /> observation phase of Hitomi. We performed the data analysis of the SGD<br /> observation, the SGD background estimation and the SGD Monte Carlo simulations,<br /> and, successfully detected polarized gamma-ray emission from the Crab nebula<br /> with only about 5 ks exposure time. The obtained polarization fraction of the<br /> phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1<br /> $\pm$ 10.6)% and, the polarization angle is 110.7$^o$ + 13.2 / $-$13.0$^o$ in<br /> the energy range of 60--160 keV (The errors correspond to the 1 sigma<br /> deviation). The confidence level of the polarization detection was 99.3%. The<br /> polarization angle measured by SGD is about one sigma deviation with the<br /> projected spin axis of the pulsar, 124.0$^o$ $\pm$0.1$^o$.
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Publications of the Astronomical Society of Japan 70(2) 2018年The present paper investigates the temperature structure of the X-ray<br /> emitting plasma in the core of the Perseus cluster using the 1.8--20.0 keV data<br /> obtained with the Soft X-ray Spectrometer (SXS) onboard the Hitomi Observatory.<br /> A series of four observations were carried out, with a total effective exposure<br /> time of 338 ks and covering a central region $\sim7'$ in diameter. The SXS was<br /> operated with an energy resolution of $\sim$5 eV (full width at half maximum)<br /> at 5.9 keV. Not only fine structures of K-shell lines in He-like ions but also<br /> transitions from higher principal quantum numbers are clearly resolved from Si<br /> through Fe. This enables us to perform temperature diagnostics using the line<br /> ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of<br /> the excitation temperature and ionization temperature in the Perseus cluster.<br /> The observed spectrum is roughly reproduced by a single temperature thermal<br /> plasma model in collisional ionization equilibrium, but detailed line ratio<br /> diagnostics reveal slight deviations from this approximation. In particular,<br /> the data exhibit an apparent trend of increasing ionization temperature with<br /> increasing atomic mass, as well as small differences between the ionization and<br /> excitation temperatures for Fe, the only element for which both temperatures<br /> can be measured. The best-fit two-temperature models suggest a combination of 3<br /> and 5 keV gas, which is consistent with the idea that the observed small<br /> deviations from a single temperature approximation are due to the effects of<br /> projection of the known radial temperature gradient in the cluster core along<br /> the line of sight. Comparison with the Chandra/ACIS and the XMM-Newton/RGS<br /> results on the other hand suggests that additional lower-temperature components<br /> are present in the ICM but not detectable by Hitomi SXS given its 1.8--20 keV<br /> energy band.
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Publications of the Astronomical Society of Japan 70(2) 2018年The Hitomi SXS spectrum of the Perseus cluster, with $\sim$5 eV resolution in<br /> the 2-9 keV band, offers an unprecedented benchmark of the atomic modeling and<br /> database for hot collisional plasmas. It reveals both successes and challenges<br /> of the current atomic codes. The latest versions of AtomDB/APEC (3.0.8), SPEX<br /> (3.03.00), and CHIANTI (8.0) all provide reasonable fits to the broad-band<br /> spectrum, and are in close agreement on best-fit temperature, emission measure,<br /> and abundances of a few elements such as Ni. For the Fe abundance, the APEC and<br /> SPEX measurements differ by 16%, which is 17 times higher than the statistical<br /> uncertainty. This is mostly attributed to the differences in adopted<br /> collisional excitation and dielectronic recombination rates of the strongest<br /> emission lines. We further investigate and compare the sensitivity of the<br /> derived physical parameters to the astrophysical source modeling and<br /> instrumental effects. The Hitomi results show that an accurate atomic code is<br /> as important as the astrophysical modeling and instrumental calibration<br /> aspects. Substantial updates of atomic databases and targeted laboratory<br /> measurements are needed to get the current codes ready for the data from the<br /> next Hitomi-level mission.
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