2021/06/22 更新

写真b

サトウ トシキ
佐藤 寿紀
SATO Toshiki
*大学が定期的に情報更新している項目(その他は、researchmapの登録情報を転載)
所属*
理学部 物理学科
職名*
助教
学位
博士(理学) ( 2018年3月   首都大学東京 )
研究キーワード
  • 高エネルギー宇宙物理学

  • 宇宙線

  • X線天文学

  • 超新星残骸

  • 超新星

  • X線望遠鏡

  • 宇宙物理学

  • 担当科目*
    学内職務経歴*
    • 2021年4月 - 現在 
      理学部   物理学科   助教
     

    研究分野

    • 自然科学一般 / 素粒子、原子核、宇宙線、宇宙物理にする理論

    • 自然科学一般 / 天文学

    経歴

    • 2021年4月 - 現在 
      立教大学   理学部 物理学科   助教

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    • 2018年4月 - 2021年3月 
      理化学研究所   玉川高エネルギー宇宙物理研究室   基礎特別研究員

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    • 2018年7月 - 2020年12月 
      NASA ゴダード宇宙飛行センター 客員研究員

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    • 2016年4月 - 2018年3月 
      日本学術振興会 特別研究員 数物系科学 (DC2)

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    学歴

    • 2015年4月 - 2018年3月 
      首都大学東京   理工学研究科   物理学専攻 博士課程

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    • 2013年4月 - 2015年3月 
      首都大学東京   理工学研究科   物理学専攻 修士課程

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    • 2009年4月 - 2013年3月 
      首都大学東京   都市教養学部   都市教養学科 物理コース

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    受賞

    • 2015年  
      NASA  2015 NASA ’s Robert H. Goddard Exceptional Achievement for Science Team 
       
      佐藤 寿紀, ASTRO-H SXT

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    • 2014年  
      NASA  2014 NASA's Group Achievement Award 
       
      佐藤 寿紀, ASTRO-H SXT

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    • 2014年  
      ASTRO-H science working group  Best poster prize at 5th ASTRO-H Summer School 
       
      佐藤 寿紀

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    論文

    • High-entropy ejecta plumes in Cassiopeia A from neutrino-driven convection

      Toshiki Sato, Keiichi Maeda, Shigehiro Nagataki, Takashi Yoshida, Brian Grefenstette, Brian J. Williams, Hideyuki Umeda, Masaomi Ono, John P. Hughes

      Nature592 ( 7855 ) 537 - 540   2021年4月

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      掲載種別:研究論文(学術雑誌)  

      Recent multi-dimensional simulations suggest that high-entropy buoyant plumes help massive stars to explode . Outwardly protruding iron (Fe)-rich fingers of gas in the galactic supernova remnant Cassiopeia A seem to match this picture. Detecting the signatures of specific elements synthesized in the high-entropy nuclear burning regime (that is, α-rich freeze out) would constitute strong substantiating evidence. Here we report observations of such elements—stable titanium (Ti) and chromium (Cr)—at a confidence level greater than 5 standard deviations in the shocked high-velocity Fe-rich ejecta of Cassiopeia A. We found that the observed Ti/Fe and Cr/Fe mass ratios require α-rich freeze out, providing evidence of the existence of the high-entropy ejecta plumes that boosted the shock wave at explosion. The metal composition of the plumes agrees well with predictions for strongly neutrino-processed proton-rich ejecta . These results support the operation of the convective supernova engine via neutrino heating in the supernova that produced Cassiopeia A. 1,2 3,4 2,5,6

      DOI: 10.1038/s41586-021-03391-9

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    • From supernova to supernova remnant: Comparison of thermonuclear explosion models 査読有り

      Gilles Ferrand, Donald C. Warren, Masaomi Ono, Shigehiro Nagataki, Friedrich K. Röpke, Ivo R. Seitenzahl, Florian Lach, Hiroyoshi Iwasaki, Toshiki Sato

      Astrophysical Journal906 ( 2 )   2021年1月10日

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      掲載種別:研究論文(学術雑誌)  

      Progress in the three-dimensional modeling of supernovae (SNe) prompts us to revisit the supernova remnant (SNR) phase. We continue our study of the imprint of a thermonuclear explosion on the SNR it produces, which we started with a delayed detonation model of a Chandrasekhar-mass white dwarf. Here we compare two different types of explosion models, each with two variants: two delayed detonation models (N100ddt, N5ddt) and two pure deflagration models (N100def, N5def), where the N number parameterizes the ignition. The output of each SN simulation is used as input to an SNR simulation carried on until 500 yr after the explosion. While all SNR models become more spherical over time and overall display the theoretical structure expected for a young SNR, clear differences are visible among the models, depending on the geometry of the ignition and on the presence or not of detonation fronts. Compared to N100 models, N5 models have a strong dipole component and produce asymmetric remnants. N5def produces a regular-looking, but offset remnant, while N5ddt produces a two-sided remnant. Pure deflagration models exhibit specific traits: a central overdensity, because of the incomplete explosion, and a network of seam lines across the surface, boundaries between burning cells. Signatures from the SN dominate the morphology of the SNR up to 100-300 yr after the explosion, depending on the model, and are still measurable at 500 yr, which may provide a way of testing explosion models.

      DOI: 10.3847/1538-4357/abc951

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    • Formation pathway for lonely stripped-envelope supernova progenitors: Implications for Cassiopeia A 査読有り

      Ryosuke Hirai, Toshiki Sato, Philipp Podsiadlowski, Alejandro Vigna-Gómez, Ilya Mandel

      Monthly Notices of the Royal Astronomical Society499 ( 1 ) 1154 - 1170   2020年11月1日

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      掲載種別:研究論文(学術雑誌)  

      We explore a new scenario for producing stripped-envelope supernova progenitors. In our scenario, the stripped-envelope supernova is the second supernova of the binary, in which the envelope of the secondary was removed during its red supergiant phase by the impact of the first supernova. Through 2D hydrodynamical simulations, we find that ~50-90 per cent of the envelope can be unbound as long as the pre-supernova orbital separation is ≤5 times the stellar radius. Recombination energy plays a significant role in the unbinding, especially for relatively high mass systems (≥18M⊙). We predict that more than half of the unbound mass should be distributed as a one-sided shell at about ~10-100 pc away from the second supernova site. We discuss possible applications to known supernova remnants such as Cassiopeia A, RX J1713.7-3946, G11.2-0.3, and find promising agreements. The predicted rate is ~0.35-1 per cent of the core-collapse population. This new scenario could be a major channel for the subclass of stripped-envelope or type IIL supernovae that lack companion detections like Cassiopeia A.

      DOI: 10.1093/mnras/staa2898

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    • A Subsolar Metallicity Progenitor for Cassiopeia A, the Remnant of a Type IIb Supernova 査読有り

      Toshiki Sato, Takashi Yoshida, Hideyuki Umeda, Shigehiro Nagataki, Masaomi Ono, Keiichi Maeda, Ryosuke Hirai, John P. Hughes, Brian J. Williams, Yoshitomo Maeda

      ASTROPHYSICAL JOURNAL893 ( 1 )   2020年4月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      We report the detection of the Mn-K alpha line in the SN-IIb remnant, Cassiopeia A. Manganese (Mn-55 after decay of Co-55), a neutron-rich element, together with chromium (Cr-52 after decay of Fe-52), is mainly synthesized in core-collapse supernovae at the explosive incomplete Si-burning regime. Therefore, the Mn/Cr mass ratio with its neutron excess reflects the neutronization at the relevant burning layer during the explosion. Chandra's deep archival X-ray data of Cassiopeia A indicate a low Mn/Cr mass ratio with values in the range 0.10-0.66, which, when compared to one-dimensional SN explosion models, requires that the electron fraction be 0.4990 less than or similar to Y-e less than or similar to 0.5 at the incomplete Si-burning layer. An explosion model assuming a solar-metallicity progenitor with a typical explosion energy (1 x 10(51) erg) fails to reproduce such a high electron fraction. We can satisfy the observed Mn/Cr mass ratio if the explosive Si-burning regime was to extend into the O/Ne hydrostatic layer, which has a higher Y-e. This would require an energetic (>2 x 10(51) erg) and/or asymmetric explosion of a subsolar-metallicity progenitor (Z less than or similar to 0.5Z) for Cassiopeia A. The low initial metallicity can be used to rule out a single-star progenitor, leaving the possibility of a binary progenitor with a compact companion. We discuss the detectability of X-rays from Bondi accretion onto such a compact companion around the explosion site. We also discuss other possible mass-loss scenarios for the progenitor system of Cassiopeia A.

      DOI: 10.3847/1538-4357/ab822a

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    • An ejecta kinematics study of kepler's supernova remnant with high-resolution chandra hetg spectroscopy 査読有り

      Matthew J. Millard, Jayant Bhalerao, Sangwook Park, Toshiki Sato, John P. Hughes, Patrick Slane, Daniel Patnaude, David Burrows, Carles Badenes

      Astrophysical Journal893 ( 2 )   2020年4月

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      掲載種別:研究論文(学術雑誌)  

      We report our measurements of the bulk radial velocity from a sample of small, metal-rich ejecta knots in Kepler's supernova remnant (SNR). We measure the Doppler shift of the He-like Si Kα line-center energy in the spectra of these knots based on our Chandra High-Energy Transmission Grating Spectrometer observation to estimate their radial velocities. We estimate high radial velocities of up to ∼8000 km s for some of these ejecta knots. We also measure proper motions for our sample based on the archival Chandra Advanced CCD Imaging Spectrometer data taken in 2000, 2006, and 2014. Our measured radial velocities and proper motions indicate that some of these ejecta knots are almost freely expanding after ∼400 yr since the explosion. The fastest moving knots show proper motions of up to ∼0.″2 per year. Assuming that these high-velocity ejecta knots are traveling ahead of the forward shock of the SNR, we estimate the distance to Kepler's SNR d ∼ 4.4-7.5 kpc. We find that the ejecta knots in our sample have an average space velocity of v ∼ 4600 km s (at a distance of 6 kpc). We note that 8 of the 15 ejecta knots from our sample show a statistically significant (at the 90% confidence level) redshifted spectrum, compared to only two with a blueshifted spectrum. This may suggest an asymmetry in the ejecta distribution in Kepler's SNR along the line of sight; however, a larger sample size is required to confirm this result. -1 -1 s

      DOI: 10.3847/1538-4357/ab7db1

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    • A Nucleosynthetic Origin for the Southwestern Fe-rich Structure in Kepler's Supernova Remnant 査読有り

      Toshiki Sato, Eduardo Bravo, Carles Badenes, John P. Hughes, Brian J. Williams, Hiroya Yamaguchi

      ASTROPHYSICAL JOURNAL890 ( 2 )   2020年2月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      Chandra X-ray observations of Kepler's supernova remnant indicate the existence of a high-speed Fe-rich ejecta structure in the southwestern region. We report strong K-shell emission from Fe-peak elements (Cr, Mn, Fe, Ni), as well as Ca, in this Fe-rich structure, implying that those elements could be produced in the inner area of the exploding white dwarf. We found Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe mass ratios of 1.0%-4.1%, 1.0%-4.6%, 1%-11%, and 2%-30%, respectively. In order to constrain the burning regime that could produce this structure, we compared these observed mass ratios with those in 18 one-dimensional Type Ia nucleosynthesis models (including both near-MCh and sub-MCh explosion models). The observed mass ratios agree well with those around the middle layer of incomplete Si burning in Type Ia nucleosynthesis models with a peak temperature of similar to(5.0-5.3) x 10(9) K and a high metallicity, Z > 0.0225. Based on our results, we infer the necessity for some mechanism to produce protruding Fe-rich clumps dominated by incomplete Si-burning products during the explosion. We also discuss the future perspectives of X-ray observations of Fe-rich structures in other Type Ia supernova remnants.

      DOI: 10.3847/1538-4357/ab6aa2

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    • Concept for an X-ray telescope system with an angular resolution booster 査読有り

      Yoshitomo Maeda, Ryo Iizuka, Takayuki Hayashi, Toshiki Sato, Nozomi Nakaniwa, Mai Takeo, Hitomi Suzuki, Manabu Ishida, Shiro Ikeda, Mikio Morii

      Publications of the Astronomical Society of Japan71 ( 5 )   2019年10月1日

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      掲載種別:研究論文(学術雑誌)  

      © 2019 The Author(s). Published by Oxford University Press on behalf of the Astronomical Society of Japan. We present a concept for an X-ray imaging system with a high angular resolution and moderate sensitivity. In this concept, a two-dimensional detector, i.e., an imager, is put at a slightly out-of-focus position of the focusing mirror, rather than just at the mirror focus, as in the standard optics, to capture miniature images of objects. In addition, a set of multi-grid masks (or a modulation collimator) is installed in front of the telescope. We find that the masks work as a coded aperture camera and that they boost the angular resolution of the focusing optics. The major advantage of this concept is that a much better angular resolution, having an order of 2-3 or more than in the conventional optics, is achievable, while a high throughput (large effective area) is maintained, which is crucial in photon-limited high-energy astronomy, because any type of mirrors, including lightweight reflective mirrors, can be employed in our concept. If the signal-to-noise ratio is sufficiently high, we estimate that angular resolutions at the diffraction limit of 4″ and 0.″4 at ∼7 keV can be achieved with a pair of masks at distances of 1 m and 100 m, respectively.

      DOI: 10.1093/pasj/psz081

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    • Genus Statistic Applied to the X-Ray Remnant of SN 1572: Clues to the Clumpy Ejecta Structure of Type Ia Supernovae 査読有り

      Toshiki Sato, John P. Hughes, Brian J. Williams, Mikio Morii

      ASTROPHYSICAL JOURNAL879 ( 2 )   2019年7月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      Clumpy structures are a common feature in X-ray images of young Type Ia supernova remnants (SNRs). Although the precise origin of such clumps remains unclear, there are three generic possibilities: dumpiness imposed during the explosion, hydrodynamic instabilities that act during the remnant's evolution, and preexisting structures in the ambient medium. In this article we focus on discriminating between clumping distributions that arise from the explosion and those from the remnant's evolution using existing 3D hydrodynamical simulations. We utilize the genus statistic for this discrimination, applying it to the simulations and to Chandra X-ray observations of the wellknown SN Ia remnant of SN 1572 (Tycho's SNR). The genus curve of Tycho's SNR strongly indicates a skewed non-Gaussian distribution of the ejecta clumps and is similar to the genus curve for the simulation with initially clumped ejecta. In contrast, the simulation of perfectly smooth ejecta where clumping arises from the action of hydrodynamic instabilities produced a genus curve that is similar to a random Gaussian field, but disagrees strongly with the genus curve of the observed image. Our results support a scenario in which the observed structure of SN Ia remnants arises from initial dumpiness in the explosion.

      DOI: 10.3847/1538-4357/ab24db

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    • Concept for the X-ray telescope system with an angular-resolution booster 査読有り

      Yoshitomo Maeda, Ryo Iizuka, Takayuki Hayashi, Toshiki Sato, Nozomi Nakaniwa, Mai Takeo, Hitomi Suzuki, Manabu Ishida, Shiro Ikeda, Mikio Morii

      Publications of the Astronomical Society of Japan71 ( 5 )   2019年

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      We present a concept of the X-ray imaging system with high angular-resolution and moderate sensitivity. In this concept, a two-dimensional detector, i.e., imager, is put at a slightly out-of-focused position of the focusing mirror, rather than just at the mirror focus as in the standard optics, to capture the miniature image of objects. In addition, a set of multi-grid masks (or a modulation collimator) is installed in front of the telescope. We find that the masks work as a coded aperture camera and that they boost the angular resolution of the focusing optics. The major advantage of this concept is that a much better angular resolution an order of 2--3 or more than in the conventional optics is achievable, while a high throughput (large effective area) is maintained, which is crucial in photon-limited high-energy astronomy, because any type of mirrors, including light-weight reflective mirrors, can be employed in our concept. If the signal-to-noise ratio is sufficiently high, we estimate that angular resolutions at the diffraction limit of 4" and 0"4 at about 7 keV can be achieved with a pair of masks at separations of 1~m and 100~m, respectively, at the diffraction limit.

      DOI: 10.1093/pasj/psz081

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    • Asymmetric expansion of the Fe ejecta in Kepler's supernova remnant 査読有り

      Kasuga Tomoaki, 佐藤 寿紀, Mori Koji, Yamaguchi Hiroya, Bamba Aya

      Publ. Astron. Soc. Japan   2018年8月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Vortical Amplification of the Magnetic Field at an Inward Shock of Supernova Remnant Cassiopeia A 査読有り

      F. Fraschetti, S. Katsuda, T. Sato, J. R. Jokipii, J. Giacalone

      Physical Review Letters120 ( 25 )   2018年6月21日

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Physical Society  

      We present an interpretation of the time variability of the x-ray flux recently reported from a multiepoch campaign of 15 years of observations of the supernova remnant Cassiopeia A by Chandra. We show for the first time quantitatively that the [4.2-6] keV nonthermal flux increase up to 50% traces the growth of the magnetic field due to a vortical amplification mechanism at a reflection inward shock colliding with inner overdensities. The fast synchrotron cooling as compared with shock-acceleration time scale qualitatively supports the flux decrease.

      DOI: 10.1103/PhysRevLett.120.251101

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    • In-flight verification of the calibration and performance of the ASTRO-H (Hitomi) soft x-ray spectrometer 査読有り

      Maurice A. Leutenegger, Marc Audard, Kevin R. Boyce, Gregory V. Brown, Meng P. Chiao, Megan E. Eckart, Ryuichi Fujimoto, Akihiro Furuzawa, Matteo Guainazzi, Daniel Haas, Takayuki Hayashi, Jan-Willem Den Herder, Ryo Iizuka, Manabu Ishida, Yoshitaka Ishisaki, Naomichi Kikuchi, Caroline A. Kilbourne, Shu Koyama, Sho Kurashima, Yoshitomo Maeda, Maxim Markevitch, Dan Mccammon, Kazuhisa Mitsuda, Hideyuki Mori, Nozomi Nakaniwa, Takashi Okajima, Stéphane Paltani, Robert Petre, F. Scott Porter, Kosuke Sato, Toshiki Sato, Makoto Sawada, Peter J. Serlemitsos, Hiromi Seta, Gary Sneiderman, Yang Soong, Satoshi Sugita, Andrew E. Szymkowiak, Yoh Takei, Makoto Tashiro, Yuzuru Tawara, Masahiro Tsujimoto, Cor P. De Vries, Tomomi Watanabe, Shinya Yamada, Noriko Yamasaki

      Journal of Astronomical Telescopes, Instruments, and Systems4 ( 2 )   2018年4月1日

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPIE  

      The Soft X-ray Spectrometer onboard the Astro-H (Hitomi) orbiting x-ray observatory featured an array of 36 silicon thermistor x-ray calorimeters optimized to perform high spectral resolution x-ray imaging spectroscopy of astrophysical sources in the 0.3-To 12-keV band. Extensive preflight calibration measurements are the basis for our modeling of the pulse height-energy relation and energy resolution for each pixel and event grade, telescope collecting area, detector efficiency, and pulse arrival time. Because of the early termination of mission operations, we needed to extract the maximum information from observations performed only days into the mission when the onboard calibration sources had not yet been commissioned and the dewar was still coming into thermal equilibrium, so our technique for reconstructing the per-pixel time-dependent pulse height-energy relation had to be modified. The gain scale was reconstructed using a combination of an absolute energy scale calibration at a single time using a fiducial from an onboard radioactive source and calibration of a dominant time-dependent gain drift component using a dedicated calibration pixel, as well as a residual time-dependent variation using spectra from the Perseus cluster of galaxies. The energy resolution was also measured using the onboard radioactive sources. It is consistent with instrument-level measurements accounting for the modest increase in noise due to spacecraft systems interference. We use observations of two pulsar wind nebulae to validate our models of the telescope area and detector efficiency and to derive a more accurate value for the thickness of the gate-valve Be window, which had not been opened by the time mission operations ceased. We use observations of the Crab nebula to refine the pixel-To-pixel timing and validate the absolute timing.

      DOI: 10.1117/1.JATIS.4.2.021407

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    • Hitomi Observations of the LMC SNR N132D: Highly Redshifted X-ray Emission from Iron Ejecta 査読有り

      Hitomi collaboration, 佐藤, 寿紀を含む

      Publ. Astron. Soc. Japan70 ( 2 )   2018年4月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Hitomi X-ray Observation of the Pulsar Wind Nebula G21.5-0.9 査読有り

      Hitomi collaboration, 佐藤, 寿紀を含む

      Publ. Astron. Soc. Japan70 ( 3 )   2018年4月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Inflight Calibration of Hitomi Soft X-ray Spectrometer (2) Point Spread Function 査読有り

      Maeda, Yoshitomo, 佐藤 寿紀, Hayashi, Takayuki, Iizuka, Ryo, Angelini, Lorella, Asai, Ryota, Furuzawa, Akihiro, Kelley, Richard, Koyama, Shu, Kurashima, Sho, Ishida, Manabu, Mori, Hideyuki, Nakaniwa, Nozomi, Okajima, Takashi, Serlemitsos, Peter J, Tsujimoto, Masahiro, Yaqoob, Tahir

      Publ. Astron. Soc. Japan70 ( 2 )   2018年4月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • Search for Thermal X-ray Features from the Crab nebula with Hitomi Soft X-ray Spectrometer 査読有り

      Hitomi collaboration, 佐藤, 寿紀を含む

      Publ. Astron. Soc. Japan70 ( 2 )   2018年4月

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      担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

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    • In-flight calibration of Hitomi Soft X-ray Spectrometer. (3) Effective area 査読有り

      Masahiro Tsujimoto, Takashi Okajima, Megan E. Eckart, Takayuki Hayashi, Akio Hoshino, Ryo Iizuka, Richard L. Kelley, Caroline A. Kilbourne, Maurice A. Leutenegger, Yoshitomo Maeda, Hideyuki Mori, Frederick S. Porter, Kosuke Sato, Toshiki Sato, Peter J. Serlemitsos, Andrew Szymkowiak, Tahir Yaqoob

      PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN70 ( 2 )   2018年3月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:OXFORD UNIV PRESS  

      We present the result of the in-flight calibration of the effective area of the Soft X-ray Spectrometer (SXS) on board the Hitomi X-ray satellite using an observation of the Crab nebula. We corrected for artifacts when observing high count rate sources with the Xray microcalorimeter. We then constructed a spectrum in the 0.5-20 keV band, which we modeled with a single power-law continuum attenuated by interstellar extinction. We evaluated the systematic uncertainty of the spectral parameters by various calibration items. In the 2-12 keV band, the SXS result is consistent with the literature values in flux (2.20 +/- 0.08 x 10(-8) erg s(-1) cm(-2) with a 1 sigma statistical uncertainty) but is softer in the power-law index (2.19 +/- 0.11). The discrepancy is attributable to the systematic uncertainty of about +6%/-7% and +2%/-5% respectively for the flux and the power-law index. The softer spectrum is affected primarily by the systematic uncertainty of the Dewar gate valve transmission and the event screening.

      DOI: 10.1093/pasj/psy008

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    • In-orbit performance of the soft X-ray imaging system aboard Hitomi 査読有り

      Nakajima Hiroshi, Maeda Yoshitomo, Uchida Hiroyuki, Tanaka Takaaki, Tsunemi Hiroshi, Hayashida Kiyoshi, Tsuru Takeshi G, Dotani Tadayasu, Nagino Ryo, Inoue Shota, Ozaki Masanobu, Tomida Hiroshi, Natsukari Chikara, Ueda Shutaro, Mori Koji, Yamauchi Makoto, Hatsukade Isamu, Nishioka Yusuke, Sakata Miho, Beppu Tatsuhiko, Honda Daigo, Nobukawa Masayoshi, Hiraga Junko S, Kohmura Takayoshi, Murakami Hiroshi, Nobukawa, Kumiko K, Bamba Aya, Doty John P, Iizuka Ryo, Sato Toshiki, Kurashima Sho, Nakaniwa Nozomi, Asai Ryota, Ishida Manadu, Mori Hideyuki, Soong Yang, Okajima Takashi, Serlemitsos Peter, Tawara Yuzuru, Mitsuishi Ikuyuki, Ishibashi Kazunori, Tamura Keisuke, Hayashi Takayuki, Furuzawa Akihiro, Sugita Satoshi, Miyazawa Takuya, Awaki Hisamitsu, Miller Eric D, Yamaguchi Hiroya

      Publications of the Astronomical Society of Japan70 ( 2 )   2018年3月

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      We describe the in-orbit performance of the soft X-ray imaging system consisting of the Soft X-ray Telescope and the Soft X-ray Imager aboard Hitomi. Verification and calibration of imaging and spectroscopic performance are carried out, making the best use of the limited data of less than three weeks. Basic performance, including a large field of view of 38′<br />
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      38<br />
      ′<br />
      ⁠, is verified with the first-light image of the Perseus cluster of galaxies. Amongst the small number of observed targets, the on-minus-off pulse image for the out-of-time events of the Crab pulsar enables us to measure the half-power diameter of the telescope as ∼1′.3<br />
      1<br />
      .<br />
      ′<br />
      3<br />
      ⁠. The average energy resolution measured with the onboard calibration source events at 5.89 keV is 179 ± 3 eV in full width at half maximum. Light leak and crosstalk issues affected the effective exposure time and the effective area, respectively, because all the observations were performed before optimizing an observation schedule and the parameters for the dark-level calculation. Screening the data affected by these two issues, we measure the background level to be 5.6 × 10−6 counts s−1 arcmin−2 cm−2 in the energy band of 5–12 keV, which is seven times lower than that of the Suzaku XIS-BI.

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    • Ground-based x-ray calibration of the Astro-H/Hitomi soft x-ray telescopes 査読有り

      Ryo Iizuka, Takayuki Hayashi, Yoshitomo Maeda, Manabu Ishida, Kazuki Tomikawa, Toshiki Sato, Naomichi Kikuchi, Takashi Okajima, Yang Soong, Peter J. Serlemitsos, Hideyuki Mori, Takanori Izumiya, Sari Minami

      Journal of Astronomical Telescopes, Instruments, and Systems4 ( 1 )   2018年1月1日

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPIE  

      We present the summary of the on-ground calibration of two soft x-ray telescopes (SXT-I and SXT-S), developed by NASA's Goddard Space Flight Center (GSFC), onboard Astro-H/Hitomi. After the initial x-ray measurements with a diverging beam at the GSFC 100-m beamline, we performed the full calibration of the x-ray performance, using the 30-m x-ray beamline facility at the Institute of Space and Astronautical Science of Japan Aerospace Exploration Agency in Japan. We adopted a raster scan method with a narrow x-ray pencil beam with a divergence of ∼15″. The on-axis effective area (EA), half-power diameter, and vignetting function were measured at several energies between 1.5 and 17.5 keV. The detailed results appear in tables and figures in this paper. We measured and evaluated the performance of the SXT-S and the SXT-I with regard to the detector-limited field-of-view and the pixel size of the paired flight detector, i.e., SXS and the SXI, respectively. The primary items measured are the EA, image quality, and stray light for on-axis and off-axis sources. The accurate measurement of these parameters is vital to make the precise response function of the ASTRO-H SXTs. This paper presents the definitive results of the ground-based calibration of the ASTRO-H SXTs.

      DOI: 10.1117/1.JATIS.4.1.011213

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    • On-ground calibration of the Hitomi Hard X-ray Telescopes 査読有り

      Hideyuki Mori, Takuya Miyazawa, Hisamitsu Awaki, Hironori Matsumoto, Yasunori Babazaki, Ayako Bandai, Tadatsugu Demoto, Akihiro Furuzawa, Yoshito Haba, Takayuki Hayashi, Ryo Iizuka, Kazunori Ishibashi, Manabu Ishida, Naoki Ishida, Masayuki Itoh, Toshihiro Iwase, Hiroyoshi Kato, Hiroaki Kobayashi, Tatsuro Kosaka, Hideyo Kunieda, Shou Kurashima, Daichi Kurihara, Yuuji Kuroda, Yoshitomo Maeda, Yoshifumi Meshino, Ikuyuki Mitsuishi, Yuusuke Miyata, Housei Nagano, Yoshiharu Namba, Yasushi Ogasaka, Keiji Ogi, Takashi Okajima, Shigetaka Saji, Fumiya Shimasaki, Takuro Sato, Toshiki Sato, Naotsugu Shima, Satoshi Sugita, Yoshio Suzuki, Kenji Tachibana, Sasagu Tachibana, Shun'Ya Takizawa, Keisuke Tamura, Yuzuru Tawara, Kazuki Tomikawa, Tatsuharu Torii, Kentaro Uesugi, Koujun Yamashita, Shigeo Yamauchi

      Journal of Astronomical Telescopes, Instruments, and Systems4 ( 1 ) 011210-1 - 011210-22   2018年1月1日

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      記述言語:英語   掲載種別:研究論文(学術雑誌)  

      © 2018 The Authors. We present x-ray characteristics of the Hard X-ray Telescopes (HXTs) on board the Hitomi (ASTRO-H) satellite. Measurements were conducted at the SPring-8 BL20B2 beamline and the ISAS/JAXA 27-m beamline. The angular resolution defined by a half-power diameter was 1.9′ (HXT-1) and 2.1′ (HXT-2) at 8 keV, 1.9′ at 30 keV, and 1.8′ at 50 keV. The effective area was found to be 620cm2 at 8 keV, 178cm2 at 30 keV, and 82cm2 at 50 keV per mirror module. Although the angular resolutions were slightly worse than the requirement (1.7′), the effective areas sufficiently exceeded the requirements of 150cm2 at 30 keV and 55cm2 at 50 keV. The off-axis measurements of the effective areas resulted in the field of view being 6.1′ at 50 keV, 7.7′ at 30 keV, and 9.7′ at 8 keV in diameter. We confirmed that the main component of the stray x-ray light was significantly reduced by mounting the precollimator as designed. Detailed analysis of the data revealed that the angular resolution was degraded mainly by figure errors of mirror foils, and the angular resolution is completely explained by the figure errors, positioning errors of the foils, and conical approximation of the foil shape. We found that the effective areas were ∼80% of the designed values below 40 keV, whereas they steeply decline above 40 keV and become only ∼50%. We investigated this abrupt decline and found that neither the error of the multilayer design nor the errors of the incident angles induced by the positioning errors of the foils can be the cause. The reflection profile of each foil pair from the defocused image strongly suggests that the figure errors of the foils probably bring about the reduction in the effective areas at higher energies.

      DOI: 10.1117/1.JATIS.4.1.011210

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    • X-Ray Measurements of the Particle Acceleration Properties at Inward Shocks in Cassiopeia A 査読有り

      Toshiki Sato, Satoru Katsuda, Mikio Morii, Aya Bamba, John P. Hughes, Yoshitomo Maeda, Manabu Ishida, Federico Fraschetti

      ASTROPHYSICAL JOURNAL853 ( 1 )   2018年1月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      We present new evidence that the bright nonthermal X-ray emission features in the interior of the Cassiopeia A supernova remnant are caused by inward-moving shocks, based on Chandra and NuSTAR observations. Several bright inward-moving filaments were identified using monitoring data taken by Chandra in 2000-2014. These inward-moving shock locations are nearly coincident with hard X-ray (15-40 keV) hot spots seen by NuSTAR. From proper-motion measurements, the transverse velocities were estimated to be in the range of similar to 2100-3800 km s(-1) for a distance of 3.4 kpc. The shock velocities in the frame of the expanding ejecta reach values of similar to 5100-8700 km s(-1), which is slightly higher than the typical speed of the forward shock. Additionally, we find flux variations (both increasing and decreasing) on timescales of a few years in some of the inward-moving shock filaments. The rapid variability timescales are consistent with an amplified magnetic field of B similar to 0.5-1 mG. The high speed and low photon cut-off energy of the inward-moving shocks are shown to imply a particle diffusion coefficient that departs from the Bohm regime (k(0) = D-0/D-0,D-Bohm similar to 3-8) for the few simple physical configurations we consider in this study. The maximum electron energy at these shocks is estimated to be similar to 8-11 TeV, which is smaller than the values of similar to 15-34 TeV that were inferred for the forward shock. Cassiopeia A is dynamically too young for its reverse shock to appear to be moving inward in the observer frame. We propose instead that the inward-moving shocks are a consequence of the forward shock encountering a density jump of 5-8 in the surrounding material.

      DOI: 10.3847/1538-4357/aaa021

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    • Freely Expanding Knots of X-Ray-emitting Ejecta in Kepler's Supernova Remnant 査読有り

      Toshiki Sato, John P. Hughes

      ASTROPHYSICAL JOURNAL845 ( 2 )   2017年8月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      We report measurements of proper motion, radial velocity, and elemental composition for 14 compact X-ray-bright knots in Kepler's supernova remnant (SNR) using archival Chandra data. The knots with the highest speed show both large proper motions (mu similar to 0.'' 11- 0,'' 14 yr(-1)) and high radial velocities (v similar to 8700-10,020 km s(-1)). For these knots the estimated space velocities (9100 km s(-1)less than or similar to v(3D)less than or similar to 10,400 km s(-1)) are similar to the typical Si velocity seen in supernovae (SNe) Ia near maximum light. High-speed ejecta knots appear only in specific locations and are morphologically and kinematically distinct from the rest of the ejecta. The proper motions of five knots extrapolate back over the age of Kepler's SNR to a consistent central position. This new kinematic center agrees well with previous determinations, but is less subject to systematic errors and denotes a location about which several prominent structures in the remnant display a high degree of symmetry. These five knots are expanding at close to the free expansion rate (expansion indices of 0.75 less than or similar to m less than or similar to 1.0), which we argue indicates either that they were formed in the explosion with a high density contrast (more than 100 times the ambient density) or that they have propagated through regions of relatively low density (n(H) < 0.1 cm(-3)) in the ambient medium. X-ray spectral analysis shows that the undecelerated knots have high Si and S abundances, a lower Fe abundance, and very low O abundance, pointing to an origin in the partial Si-burning zone, which occurs in the outer layer of the exploding white dwarf for models of SNe Ia. Other knots show lower speeds and expansion indices consistent with decelerated ejecta knots or features in the ambient medium overrun by the forward shock. Our new accurate location for the explosion site has well-defined positional uncertainties, allowing for a great reduction in the area to be searched for faint surviving donor stars under non-traditional single-degenerate SNe Ia scenarios; because of the lack of bright stars in the search area the traditional scenario remains ruled out.

      DOI: 10.3847/1538-4357/aa8305

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    • Direct Ejecta Velocity Measurements of Tycho's Supernova Remnant 査読有り

      Toshiki Sato, John P. Hughes

      ASTROPHYSICAL JOURNAL840 ( 2 )   2017年5月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      We present the first direct ejecta velocity measurements of Tycho's supernova remnant (SNR). Chandra's high angular resolution images reveal a patchy structure of radial velocities in the ejecta that can be separated into distinct redshifted, blueshifted, and low velocity ejecta clumps or blobs. The typical velocities of the redshifted and blueshifted blobs are less than or similar to 7800 and less than or similar to 5000 km s(-1), respectively. The highest velocity blobs are located near the center, while the low velocity ones appear near the edge as expected for a generally spherical expansion. Systematic uncertainty on the velocity measurements from gain calibration was assessed by carrying out joint fits of individual blobs with both the ACIS-I and ACIS-S detectors. We determine the three-dimensional kinematics of the Si-and Fe-rich clumps in the southeastern (SE) quadrant and show that these knots form a distinct, compact, and kinematically connected structure, possibly even a chain of knots strung along the remnant's edge. By examining the viewing geometries, we conclude that the knots in the SE region are unlikely to be responsible for the high velocity Ca II absorption features seen in the light-echo spectrum of SN. 1572, the originating event for Tycho's SNR.

      DOI: 10.3847/1538-4357/aa6f60

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    • Multi-year X-Ray Variations of Iron-K and Continuum Emissions in the Young Supernova Remnant Cassiopeia A 査読有り

      Toshiki Sato, Yoshitomo Maeda, Aya Bamba, Satoru Katsuda, Yutaka Ohira, Ryo Yamazaki, Kuniaki Masai, Hironori Matsumoto, Makoto Sawada, Yukikatsu Terada, John P. Hughes, Manabu Ishida

      ASTROPHYSICAL JOURNAL836 ( 2 )   2017年2月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

      We found a simultaneous decrease of the Fe-K line and 4.2-6 keV continuum of Cassiopeia A with the monitoring data taken by the Chandra X-ray Observatory in 2000-2013. The flux change rates in the whole remnant are -0.65 +/- 0.02% yr(-1) in the 4.2-6.0 keV continuum and -0.6 +/- 0.1% yr(-1) in the Fe-K line. In the eastern region where the thermal emission is considered to dominate, the variations show the largest values: -1.03 +/- 0.05% yr(-1) (4.2-6 keV band) and -0.6 +/- 0.1% yr(-1) (Fe-K line). In this region, the time evolution of the emission measure and the temperature have a decreasing trend. This could be interpreted as adiabatic cooling with the expansion of m = 0.66. On the other hand, in the non-thermal emission dominated regions, variations of the 4.2-6 keV continuum show smaller rates: -0.60 +/- 0.04% yr(-1) in the southwestern region, -0.46 +/- 0.05% yr(-1) in the inner region, and + 0.00 +/- 0.07% yr(-1) in the forward shock region. In particular, flux does not show significant change in the forward shock region. These results imply that strong braking in shock velocity has not been occurring in Cassiopeia A (< 5 km s(-1) yr(-1)). All of our results support the idea that X-ray flux decay in the remnant is mainly caused by thermal components.

      DOI: 10.3847/1538-4357/836/2/225

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    • An angular-resolution booster on the broadband X-ray telescope system 査読有り

      Yoshitomo Maeda, Ryo Iizuka, Toshiki Sato, Manabu Ishida, Takayuki Hayashi, Ryoko Nakamura

      OPTICS FOR EUV, X-RAY, AND GAMMA-RAY ASTRONOMY VIII10399   2017年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      We present a design of the broad band telescope with the angular resolution booster. A concept of the Xray imaging system with high angular-resolution and moderate sensitivity was presented by Maeda et al. (submitted). In the concept, a two-dimensional detector, i.e., imager, is put at a slightly defocused position of the focusing mirror, rather than right at the mirror focus as in the standard optics. The detector at the off-focus captures the microcosm of front mask-slits that are placed on the front of the mirror. The masks work as a modulation collimator and boost the angular resolution of the focusing telescope. The major advantage of this concept is that a much better angular resolution by an order of 2-3 or more than in the conventional optics is achievable, while a high throughput (large effective area) is maintained. We therefore present an example of a booster for a broad-band telescope. Using the technique of the Pt/C depth-graded supermirror, the broadband coverage up to 80 keV is discussed.

      DOI: 10.1117/12.2273466

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    • Reflectivity around the gold L-edges of x-ray reflector of the soft x-ray telescope onboard ASTRO-H

      Yoshitomo Maeda, Naomichi Kikuchi, Sho Kurashima, Manabu Ishida, Ryo Iizuka, Takayuki Hayashi, Takashi Okajima, Hironori Matsumoto, Ikuyuki Mitsuishi, Shigetaka Saji, Toshiki Sato, Sasagu Tachibana, Hideyuki Mori, Finn Christensen, Nicolai Brejnholt, Kiyofumi Nitta, Tomoya Uruga

      OPTICS FOR EUV, X-RAY, AND GAMMA-RAY ASTRONOMY VIII10399   id. 99053Z   2017年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      We report the atomic scattering factor in the 11.2-15.4 keV for the ASTRO-H Soft X-ray Telescope (SXT)2 obtained in the ground based measurements. The large effective area of the SXT covers above 10 keV. In fact, the flight data show the spectra of the celestical objects in the hard X-ray band. In order to model the area, the reflectivity measurements in the 11.2-15.4 keV band with the energy pitch of 0.4 0.7 eV were made in the synchrotron beamline Spring-8 BL01B1. We obtained atomic scattering factors fl and f2 by the curve fitting to the reflectivities of our witness sample. The edges associated with the gold's L-I, II, and III transitions are identified, of which the depths are found to be roughly 60% shallower than those expected from the Henke's atomic scattering factor.

      DOI: 10.1117/12.2275605

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    • Atomic scattering factor of the ASTRO-H (Hitomi) SXT reflector around the gold's L edges 査読有り

      Naomichi Kikuchi, Sho Kurashima, Manabu Ishida, Ryo Iizuka, Yoshitomo Maeda, Takayuki Hayashi, Takashi Okajima, Hironori Matsumoto, Ikuyuki Mitsuishi, Shigetaka Saji, Toshiki Sato, Sasagu Tachibana, Hideyuki Mori, Finn Christensen, Nicolai Brejnholt, Kiyofumi Nitta, Tomoya Uruga

      OPTICS EXPRESS24 ( 22 ) 25548 - 25564   2016年10月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:OPTICAL SOC AMER  

      The atomic scattering factor in the energy range of 11.2-15.4 keV for the ASTROH Soft X-ray Telescope (SXT) is reported. The large effective area of the SXT makes use of photon spectra above 10 keV viable, unlike most other X-ray satellites with total-reflection mirror optics. Presence of gold's L-edges in the energy band is a major issue, as it complicates the function of the effective area. In order to model the area, the reflectivity measurements in the 11.2-15.4 keV band with the energy pitch of 0.4-0.7 eV were made in the synchrotron beamline Spring-8 BL01B1. We obtained atomic scattering factors f1 and f2 by the curve fitting to the reflectivities of our witness sample. The edges associated with the L-I, II, and III transitions are identified, of which the depths are found to be roughly 60% shallower than those expected from the Henke's atomic scattering factor. (C) 2016 Optical Society of America

      DOI: 10.1364/OE.24.025548

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    • Examining the angular resolution of the ASTRO-H's soft x-ray telescopes 査読有り

      Toshiki Sato, Ryo Iizuka, Manabu Ishida, Naomichi Kikuchi, Yoshitomo Maeda, Sho Kurashima, Nozomi Nakaniwa, Kazuki Tomikawa, Takayuki Hayashi, Hideyuki Mori, Takashi Okajima, Peter J. Serlemitsos, Yang Soong, Takanori Izumiya, Sari Minami

      JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS2 ( 4 )   2016年10月

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      担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

      The international x-ray observatory ASTRO-H was renamed "Hitomi" after launch. It covers a wide energy range from a few hundred eV to 600 keV. It is equipped with two soft x-ray telescopes (SXTs: SXT-I and SXT-S) for imaging the soft x-ray sky up to similar to 12 keV, which focus an image onto the respective focal-plane detectors: CCD camera (SXI) and a calorimeter (SXS). The SXTs are fabricated in a quadrant unit. The angular resolution in half-power diameter (HPD) of each quadrant of the SXTs ranges between 1.1 and 1.4 arc min at 4.51 keV. It was also found that one quadrant has an energy dependence on the HPD. We examine the angular resolution with "spot scan" measurements. In order to understand the cause of imaging capability deterioration and to reflect it to the future telescope development, we carried out spot scan measurements, in which we illuminate all over the aperture of each quadrant with a square beam 8 mm on a side. Based on the scan results, we made "maps" of image blurring and a focus position. The former and the latter reflect figure error and positioning error, respectively, of the foils that are within the incident 8 mm x 8 mm beam. As a result, we estimated those errors in a quadrant to be similar to 0.9 to 1.0 and similar to 0.6 to 0.9 arc min, respectively. We found that the larger the positioning error in a quadrant is, the larger its HPD is. The HPD map, which manifests the local image blurring, is very similar from quadrant to quadrant, but the map of the focus position is different from location to location in each telescope. It is also found that the difference in local performance causes energy dependence of the HPD. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

      DOI: 10.1117/1.JATIS.2.4.044001

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    • First peek of ASTRO-H Soft X-ray Telescope (SXT) in-orbit performance 査読有り

      Takashi Okajima, Yang Soong, Peter Serlemitsos, Hideyuki Mori, Larry Olsen, David Robinson, Richard Koenecke, Bill Chang, Devin Hahne, Ryo Iizuka, Manabu Ishida, Yoshitomo Maeda, Toshiki Sato, Naomichi Kikuchi, Sho Kurashima, Nozomi Nakaniwa, Takayuki Hayashi, Kazunori Ishibashi, Takuya Miyazawa, Kenji Tachibana, Keisuke Tamura, Akihiro Furuzawa, Yuzuru Tawara, Satoshi Sugita

      Proceedings of SPIE - The International Society for Optical Engineering9905   2016年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE  

      ASTRO-H (Hitomi) is a Japanese X-ray astrophysics satellite just launched in February, 2016, from Tanegashima, Japan by a JAXA's H-IIA launch vehicle. It has two Soft X-ray Telescopes (SXTs), among other instruments, that were developed by NASA's Goddard Space Flight Center in collaboration with ISAS/JAXA and Nagoya University. One is for an X-ray micro-calorimeter instrument (Soft X-ray Spectrometer, SXS) and the other for an X-ray CCD camera (Soft X-ray Imager, SXI), both covering the X-ray energy band up to 15 keV. The two SXTs were fully characterized at the 30-m X-ray beamline at ISAS/JAXA. The combined SXT+SXS system effective area is about 250 and 300 cm2 at 1 and 6 keV, respectively, although observations were performed with the gate valve at the dewar entrance closed, which blocks most of low energy X-rays and some of high energy ones. The angular resolution for SXS is 1.2 arcmin (Half Power Diameter, HPD). The combined SXT+SXI system effective area is about 370 and 350 cm2 at 1 and 6 keV, respectively. The angular resolution for SXI is 1.3 arcmin (HPD). The both SXTs have a field of view of about 16 arcmin (FWHM of their vignetting functions). The SXT+SXS field of view is limited to 3 × 3 arcmin by the SXS array size. In-flight data available to the SXT team was limited at the time of this conference and a point-like source data is not available for the SXT+SXS. Although due to lack of attitude information we were unable to reconstruct a point spread function of SXT+SXI, according to RXJ1856.5-3754 data, the SXT seems to be working as expected in terms of imaging capability. As for the overall effective area response for both SXT+SXS and SXT+SXI, consistent spectral model fitting parameters with the previous measurements were obtained for Crab and G21.5-0.9 data. On the other hand, their 2-10 keV fluxes differ by about 20% at this point. Calibration work is still under progress. The SXT is the latest version of the aluminum foil X-ray mirror, which is extremely light-weight and very low cost, yet produces large effective area over a wide energy-band. Its area-mass ratio is the largest, 16 cm2/kg, among ASTRO-H, Chandra, and XMM-Newton mirrors. The aluminum foil mirror is a still compelling technology depending on the mission science goal.

      DOI: 10.1117/12.2231705

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    • In-flight verification of the calibration and performance of the ASTRO-H (Hitomi) Soft X-Ray Spectrometer 査読有り

      Maurice A. Leutenegger, Marc Audard, Kevin R. Boyce, Gregory V. Brown, Meng P. Chiao, Megan E. Eckart, Ryuichi Fujimoto, Akihiro Furuzawa, Matteo Guainazzi, Daniel Haas, Jan-Willem Den Herder, Takayuki Hayashi, Ryo Iizuka, Manabu Ishida, Yoshitaka Ishisaki, Richard L. Kelley, Naomichi Kikuchi, Caroline A. Kilbourne, Shu Koyama, Sho Kurashima, Yoshitomo Maeda, Maxim Markevitch, Dan McCammon, Kazuhisa Mitsuda, Hideyuki Mori, Nozomi Nakaniwa, Takashi Okajima, Stéphane Paltani, Robert Petre, F. Scott Porter, Kosuke Sato, Toshiki Sato, Makoto Sawada, Peter J. Serlemitsos, Hiromi Seta, Gary Sneiderman, Yang Soong, Satoshi Sugita, Andrew E. Szymkowiak, Yoh Takei, Makoto Tashiro, Yuzuru Tawara, Masahiro Tsujimoto, Cor P. De Vries, Tomomi Watanabe, Shinya Yamada, Noriko Yamasaki

      Proceedings of SPIE - The International Society for Optical Engineering9905   2016年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE  

      The Soft X-ray Spectrometer (SXS) onboard the Astro-H (Hitomi) orbiting x-ray observatory featured an array of 36 silicon thermistor x-ray calorimeters optimized to perform high spectral resolution x-ray imaging spectroscopy of astrophysical sources in the 0.3-12 keV band. Extensive pre-flight calibration measurements are the basis for our modeling of the pulse-height-energy relation and energy resolution for each pixel and event grade, telescope collecting area, detector efficiency, and pulse arrival time. Because of the early termination of mission operations, we needed to extract the maximum information from observations performed only days into the mission when the onboard calibration sources had not yet been commissioned and the dewar was still coming into thermal equilibrium, so our technique for reconstructing the per-pixel time-dependent pulse-height-energy relation had to be modified. The gain scale was reconstructed using a combination of an absolute energy scale calibration at a single time using a fiducial from an onboard radioactive source, and calibration of a dominant time-dependent gain drift component using a dedicated calibration pixel, as well as a residual time-dependent variation using spectra from the Perseus cluster of galaxies. The energy resolution was also measured using the onboard radioactive sources. It is consistent with instrument-level measurements accounting for the modest increase in noise due to spacecraft systems interference. We use observations of two pulsars to validate our models of the telescope area and detector efficiency, and to derive a more accurate value for the thickness of the gate valve Be window, which had not been opened by the time mission operations ceased. We use observations of the Crab pulsar to refine the pixel-to-pixel timing and validate the absolute timing.

      DOI: 10.1117/12.2234230

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    • Point spread function of ASTRO-H Soft X-ray Telescope (SXT) 査読有り

      Takayuki Hayashi, Toshiki Sato, Naomichi Kikuchi, Ryo Iizuka, Yoshitomo Maeda, Manabu Ishida, Sho Kurashima, Nozomi Nakaniwa, Takashi Okajima, Hideyuki Mori, Yang Soong, Peter J. Serlemitosos

      SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY9905   2016年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      ASTRO-H (Hitomi) satellite equips two Soft X-ray Telescopes (SXTs), one of which (SXT-S) is coupled to Soft X-ray Spectrometer (SXS) while the other (SXT-I) is coupled to Soft X-ray Imager (SXI). Although SXTs are lightweight of similar to 42 kg module(-1) and have large on-axis effective area (EA) of similar to 450cm(2) at 4.5 keV module(-1) by themselves, their angular resolutions are moderate similar to 1.2 arcmin in half power diameter. The amount of contamination into the SXS FOV (3.05 x 3.05 arcmin(2)) from nearby sources was measured in the ground-based calibration at the beamline in Institute of Space and Astronautical Science. The contamination at 4.5 keV were measured with sources distant from the SXS center by one width of the FOV in perpendicular and diagonal directions, that is, 3 and 4.5 arcmin-off, respectively. The average EA of the contamination in the four directions with the 3 and 4.5 arcmin-off were measured to be 2 and 0.6% of the on-axis EA of 412 cm(2) for the SXS FOV, respectively. The contamination from a source distant by two FOV widths in a diagonal direction, that is, 8.6 arcmin-off was measured to be 0.1% of the on-axis at 4.5 keV. The contamination amounts were also measured at 1.5 keV and 8.0 keV which indicated that the ratio of the contamination EA to that of on-axis hardly depended on the source energy. The off-axis SXT-I images from -4.5 to 27 arcmin were acquired at intervals of 4.5 arcmin for the SXI FOV of 38 x 38 arcmin(2). The image shrinked as the off-axis angle increased. Above 13.5 arcmin of off-angle, a stray appeared around the image center in the off-axis direction. As for the on-axis image, a ring-shaped stray appeared at the edge of SXI of similar to 18 arcmin distant from the image center.

      DOI: 10.1117/12.2232007

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    • Reflectivity around the gold L-edges of x-ray reflector of the soft x-ray telescope onboard ASTRO-H

      Yoshitomo Maeda, Naomichi Kikuchi, Sho Kurashima, Manabu Ishida, Ryo Iizuka, Takayuki Hayashi, Takashi Okajima, Hironori Matsumoto, Ikuyuki Mitsuishi, Shigetaka Saji, Toshiki Sato, Sasagu Tachibana, Hideyuki Mori, Finn Christensen, Nicolai Brejnholt, Kiyofumi Nitta, Tomoya Uruga

      Proceedings of SPIE - The International Society for Optical Engineering9905   id. 99053Y   2016年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE  

      We report the atomic scattering factor in the 11.2{15.4 keV for the ASTRO-H Soft X-ray Telescope (SXT)9 obtained in the ground based measurements. The large effective area of the SXT covers above 10 keV. In fact, the flight data show the spectra of the celestical objects in the hard X-ray band. In order to model the area, the reflectivity measurements in the 11.2-15.4 keV band with the energy pitch of 0.4 - 0.7 eV were made in the synchrotron beamline Spring-8 BL01B1. We obtained atomic scattering factors f1 and f2 by the curve fitting to the reflectivities of our witness sample. The edges associated with the gold's L-I, II, and III transitions are identified, of which the depths are found to be roughly 60% shallower than those expected from the Henke's atomic scattering factor.

      DOI: 10.1117/12.2232727

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    • The ASTRO-H SXT performance to the large off-set angles 査読有り

      Toshiki Sato, Ryo Iizuka, Hideyuki Mori, Takayuki Hayashi, Yoshitomo Maeda, Manabu Ishida, Naomichi Kikuchi, Sho Kurashima, Nozomi Nakaniwa, Takashi Okajima, Yang Soong, Peter J. Serlemitosos

      SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY9905   2016年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      The X-ray astronomy satellite ASTRO-H, which is the 6th Japanese X-ray astronomy satellite and is renamed Hitomi after launch, is designed to observe celestial X-ray objects in a wide energy band from a few hundred eV to 600 keV. The Soft X-ray Telescopes (SXTs) onboard ASTRO-H play a role of collecting and imaging X-rays up to similar to 12 keV. Although the field of view of the SXT is similar to 15' (FWHM), due to the thin-foil-nested Wolter-I type optics adopted in the SXTs, X-rays out of the field of view can reach the focal plane without experiencing a normal double reflection. This component is referred to as "stray light". Owing to investigation of the stray light so far, "secondary reflection" is now identified as the main component of the stray light, which is composed of X-rays reflected only by secondary reflectors. In order to cut the secondary reflections, a "pre-collimator" is equipped on top of the SXTs. However, we cannot cut all the stray lights with the pre-collimator in some off-axis angle domain. In this study, we measure the brightness of the stray light of the SXTs at some representative off-axis angles by using the ISAS X-ray beam line.ASTRO-H is equipped with two modules of the SXT; one is for the Soft X-ray Spectrometer (SXS), an X-ray calorimeter, and the other is for the Soft X-ray Imager (SXI), an X-ray CCD camera. These SXT modules are called SXT-S and SXT-I, respectively. Of the two detector systems, the SXI has a large field of view, a square with 38' on a side. To cope with this, we have made a mosaic mapping of the stray light at a representative off-axis angle of 30' in the X-ray beam line at the Institute of Space and Astronautical Science. The effective area of the brightest secondary reflection is found of order similar to 0.1% of the on-axis effective area at the energy of 1.49 keV. The other components are not so bright (<5x10(-4) times smaller than the on-axis effective area). On the other hand, we have found that the effective area of the stray light in the SXS field of view (similar to 3'x3') at large off-axis angles (>15') are similar to 10(-4) times smaller than the on-axis effective area (similar to 590 cm(2) at 1.49 keV).

      DOI: 10.1117/12.2232175

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    • Upgrade of the 30-m x-ray pencil beam line at the Institute of Space and Astronautical Science 査読有り

      Takayuki Hayashi, Toshiki Sato, Naomichi Kikuchi, Sho Kurashima, Nozomi Nakaniwa, Takuro Sato, Ryo Iizuka, Yoshitomo Maeda, Manabu Ishida

      JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS1 ( 4 )   2015年10月

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

      The 30-m x-ray pencil beam line at the Institute of Space and Astronautical Science has been upgraded. The vacuum chamber has been replaced by a new cylindrical chamber of diameter 1.8 m and length 11.3 m. Stages on which a telescope and detectors had been mounted were also replaced. At the same time, a new charge-coupled device consisting of 1240 x 1152 pixels of size 22.5 x 22.5 mu m(2) was introduced. The detector stage can be moved along the x-ray beam in the vacuum chamber, which enables us to vary the distance between the sample and the detectors from 0.7 to 9 m. The two stages can be moved in a square region 500 x 500 mm(2) in the plane normal to the x-ray beam. The pitching of moving axes of Y direction (horizontal and normal to the beam) of the sample and the detector stages is somewhat large, but does not exceed 60 arc sec. The pitching of the other axes and the yawing of all the axes are less than 30 arc sec. As for rolling, we could obtain only the upper limits because of the difficulty in measuring them. The upper limit of the Z direction (vertical and normal to the beam) of the detector stage moving axis is somewhat large and is about 60 arc sec, and those of the other axes are less than 30 arc sec. A summary of the beam line performance is presented. Soon after the upgrade, the ASTRO-H Soft X-ray telescopes were calibrated in this beam line. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

      DOI: 10.1117/1.JATIS.1.4.044004

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    • Thermal stress test of the depth-graded platinum/carbon reflectors 査読有り

      Yoshitomo Maeda, Kou Ichihara, Hiroaki Kan, Yu Shionome, Takuro Sato, Toshiki Sato, Takayuki Hayashi, Manabu Ishida, Yoshiharu Namba, Hideaki Takahashi, Takuya Miyazawa, Kazunori Ishibashi, Michito Sakai, Satoshi Sugita, Yoshito Haba, Hironori Matsumoto, Hideyuki Mori

      Journal of Astronomical Telescopes, Instruments, and Systems1 ( 3 ) id. 034001   2015年7月1日

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      記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPIE  

      The ASTRO-H hard x-ray telescope (HXT) is designed to reflect hard x-rays with energies up to 80 keV. It will make use of thin-foil, multinested conical optics with depth-graded platinum/carbon (Pt/C) multilayers. We report on thermal stress tests of the HXT reflectors. The reflectors were fabricated on a heat-formed aluminum substrate of thickness gauged at 200 μm of the alloy 5052. This was followed by an epoxy replication on Pt/C-sputtered smooth Pyrex cylindrical mandrels to acquire the x-ray reflective surface. For the thermal tests, the reflectors were maintained at three different temperatures: -5, 50, and 60°C, respectively, for a week. We found that the surface of the reflectors were significantly changed at temperatures of 60°C or higher. The change appears as wrinkles with a typical scale length of a few tens of microns. No changes on the surface were observed from the -5 and 50°C samples. There was also no change in the x-ray reflectivity for these two temperatures.

      DOI: 10.1117/1.JATIS.1.3.034001

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    • Hard x-ray telescopes to be onboard ASTRO-H 査読有り

      Hisamitsu Awaki, Hideyo Kunieda, Manabu Ishida, Hironori Matsumoto, Yasunori Babazaki, Tadatsugu Demoto, Akihiro Furuzawa, Yoshito Haba, Takayuki Hayashi, Ryo Iizuka, Kazunori Ishibashi, Naoki Ishida, Masayuki Itoh, Toshihiro Iwase, Tatsuro Kosaka, Daichi Kurihara, Yuuji Kuroda, Yoshitomo Maeda, Yoshifumi Meshino, Ikuyuki Mitsuishi, Yuusuke Miyata, Takuya Miyazawa, Hideyuki Mori, Housei Nagano, Yoshiharu Namba, Yasushi Ogasaka, Keiji Ogi, Takashi Okajima, Shigetaka Saji, Fumiya Shimasaki, Takuro Sato, Toshiki Sato, Satoshi Sugita, Yoshio Suzuki, Kenji Tachibana, Sasagu Tachibana, Shunya Takizawa, Keisuke Tamura, Yuzuru Tawara, Tatsuharu Torii, Kentato Uesugi, Koujun Yamashita, Shigeo Yamauchi

      Applied Optics53 ( 32 ) 7664 - 7676   2014年11月10日

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      掲載種別:研究論文(学術雑誌)  

      © 2014 Optical Society of America. The new Japanese x-ray astronomy satellite, ASTRO-H, will carry two identical hard x-ray telescopes (HXTs), which cover the energy range of 5 to 80 keV. The HXT mirrors employ tightly nested, conically approximated thin-foil Wolter-I optics, and the mirror surfaces are coated with Pt/C depth-graded multilayers to enhance the hard x-ray effective area by means of Bragg reflection. The HXT comprises foils 120-450 mm in diameter and 200 mm in length, with a focal length of 12 m. To obtain a large effective area, 213 aluminum foils 0.2 mm in thickness are tightly nested confocally. The requirements for HXT are a total effective area of >300 cm2 at 30 keV and an angular resolution of <1.70 in halfpower diameter (HPD). Fabrication of two HXTs has been completed, and the x-ray performance of each HXT was measured at a synchrotron radiation facility, SPring-8 BL20B2 in Japan. Angular resolutions (HPD) of 1.9′ and 1.8′ at 30 keV were obtained for the full telescopes of HXT-1 and HXT-2, respectively. The total effective area of the two HXTs at 30 keV is 349 cm2.

      DOI: 10.1364/AO.53.007664

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    • ASTRO-H Soft X-ray Telescope (SXT) 査読有り

      Yang Soong, Takashi Okajima, Peter J. Serlemitsos, Stephen L. Odell, Brian D. Ramsey, Mikhail V. Gubarev, Manabu Ishida, Yoshitomo Maeda, Ryo Iizuka, Takayuki Hayashi, Yuzuru Tawara, Akihiro Furuzawa, Hideyuki Mori, Takuya Miyazawa, Hideyo Kunieda, Hisamitsu Awaki, Satoshi Sugita, Keisuke Tamura, Kazunori Ishibashi, Takanori Izumiya, Sari Minami, Toshiki Sato, Kazuki Tomikawa, Naomichi Kikuchi, Toshihiro Iwase

      SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY9144   2014年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      ASTRO-H is an astrophysics satellite dedicated for non-dispersive X-ray spectroscopic study on selective celestial X-ray sources. Among the onboard instruments there are four Wolter-I X-ray mirrors of their reflectors' figure in conical approximation. Two of the four are soft X-ray mirrors(1), of which the energy range is from a few hundred eV to 15 keV within the effective aperture being defined by the nested reflectors' radius ranging between 5.8 cm to 22.5 cm. The focal point instruments will be a calorimeter (SXS) and a CCD camera (SXI), respectively. The mirrors were in quadrant configuration with photons being reflected consecutively in the primary and secondary stage before converging on the focal plane of 5.6 m away from the interface between the two stages. The reflectors of the mirror are made of heat-formed aluminum substrate of the thickness gauged of 152 mu m, 229 mu m, and 305 mu m of the alloy 5052 H-19, followed by epoxy replication on gold-sputtered smooth Pyrex cylindrical mandrels to acquire the X-ray reflective surface. The epoxy layer is 10 mu m nominal and surface gold layer of 0.2 mu m. Improvements on angular response over its predecessors, e.g. Astro-E1/Suzaku mirrors, come from error reduction on the figure, the roundness, and the grazing angle/radius mismatching of the reflecting surface, and tighter specs and mechanical strength on supporting structure to reduce the reflector positioning and the assembly errors.Each soft x-ray telescope (SXT), SXT-1 or SXT-2, were integrated from four independent quadrants of mirrors. The stray-light baffles, in quadrant configuration, were mounted onto the integrated mirror. Thermal control units were attached to the perimeter of the integrated mirror to keep the mirror within operating temperature in space. The completed instrument went through a series of optical alignment, thus made the quadrant images confocal and their optical axes in parallel to achieve highest throughput possible. Environmental tests were carried out, and optical quality of the telescopes has been confirmed. SXT-1 and -2 were tested with the broad but slightly divergent beam, up to 8 arc-minutes, at Goddard. The full characterization were carried out in Japan which includes: angular resolution, effective area in the energy range of similar to 0.4 - 12keV, off-axis response at various energies, etc. We report the calibration results of the SXT-1 and -2 that were obtained at NASA/Goddard and JAXA/ISAS. The detailed calibration are reported in the two papers in this conference: 9144-206, "Ground-based x-ray calibration of the ASTRO-H soft x-ray telescopes" by R. Iizuka et al. and 9144-207, "Revealing a detailed performance of the soft x-ray telescopes of the ASTRO-H mission" by T. Sato, et al. Some small but significant discrepancies existed between ISAS and Goddard measurements that were attributed to the difference of the X-ray beams - pencil beam vs divergent beam.

      DOI: 10.1117/12.2056804

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    • Ground-based X-ray calibration of the Astro-H soft X-ray telescopes 査読有り

      Ryo Iizuka, Takayuki Hayashi, Yoshitomo Maeda, Manabu Ishida, Kazuki Tomikawa, Toshiki Sato, Naomichi Kikuchi, Takashi Okajima, Yang Soong, Peter J. Serlemitosos, Hideyuki Mori, Takanori Izumiya, Sari Minami

      SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY9144   2014年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      The X-ray astronomy satellite Astro-H, planed to be launched in 2015, will have several instruments for covering a wide energy band from a few hundreds eV to 600 keV. There are four X-ray telescopes, and two of them are soft X-ray telescopes (SXTs) covering up to about 15 keV. One is for an X-ray micro-calorimeter detector (SXS) and the other is for an X-ray CCD detector (SXI). The design of the SXTs is a conical approximation of the Wolter Type-I optics, which is also adopted for the telescopes on the previous mission Suzaku launched in 2005. It consists 203 thin-foil reflectors coated with gold monolayer (2000 angstrom) on the aluminum substrate (101.6 mm length) with the thickness of 0.15, 0.23 and 0.31 mm. These are nested confocally within the radius of 58 to 225 mm. The focal length of SXTs is 5.6 m. The weight is as light as similar to 43 kg per telescope.
      We present the current status of the calibration activity of two SXTs (SXT-1 and SXT-2). The developments of two SXTs were completed by NASA's Goddard Space Flight Center (GSFC). First X-ray measurements with a diverging beam at the GSFC 100m beamline found an angular resolution at 8.0 keV to be 1.1 and 1.0 arcmin (HPD) for SXT-1 and SXT-2, respectively. The full characterization of the X-ray performance has been now continuously calibrated with the 30m X-ray beamline facility at the Institute of Space and Astronautical Science (ISAS) of Japan Aerospace eXploration Agency (JAXA) in Japan. We adopted a raster scan method with a narrow X-ray pencil beam with the divergence of similar to 15". X-ray characterization of the two SXTs has been measured from May and December 2013, respectively.
      In the case of SXT-1, the on-axis effective area was approximately 580, 445, 370, 270, 185 and 90 cm(2) at energies of 1.5, 4.5, 8.0, 9.4, 11.1 and 12.9 keV respectively. The effective area of SXT-2 is 2% larger than that of SXT-1 irrespective to X-ray energy. The on-axis angular resolution of SXT-1 was evaluated as 1.3 - 1.5 arcmin (HPD) in the 1.5 13 keV band. The resolution was slightly got worse at higher energies by similar to 0.3 arcmin. Otherwise, the resolution of SXT-2 is 1.2 arcmin, almost irrespective to X-ray energy. The field of view (FOV) was similar to 16 arcmin at 1.5 keV, decreasing with increasing X-ray energy, and became 8 arcmin at 13 keV. The FOV is defined here as the full-width at half-maximum (FWHM) of the vignetting curve.
      The X-ray performance of SXT-1 and SXT-2 meets the system requirements. Because all the parameters of the SXT-2 is slightly better that of SXT-1, we adopted the SXT-2 telescope for the SXS detector of the Astro-H primary instrument with the narrow FOV.

      DOI: 10.1117/12.2054626

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    • Upgrade of the thirty-meter x-ray pencil beam line at the institute of space and astronautical science 査読有り

      Takayuki Hayashi, Toshiki Sato, Kazuki Tomikawa, Naomichi Kikuchi, Takuro Sato, Ryo Iizuka, Yoshitomo Maeda, Manabu Ishida

      SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY9144   2014年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

      The thirty-meter X-ray pencil beam line at the Institute of Space and Astronautical Science (ISAS) was utilized for ground-based calibrations of X-ray telescopes (XRTs) onboard the ASTRO-D, the ASTRO-E and the ASTRO-E2 satellites. Recent upsizing or downsizing of XRT required upgrade of the ISAS beam line. We replaced a vacuum chamber in which the stages had been installed by a new cylindrical chamber whose diameter and length are 1.8 m and 11.3 m, respectively. Stages on which a telescope and detectors had been mounted were also replaced. At same time, a new CCD consists of 1240 x 1152 pixels whose size are 22.5 x 22.5 mu m was introduced. The detector stage can be moved along the X-ray beam in the vacuum chamber, which allows us to change the distance between the sample and the detectors from 0.7 m to 9 m. The two stages can move in at least 500 x 500 mm(2) of square in the plane normal to the X-ray beam. The pitching of some moving axes are measured at 60 arcsec at most. The others are no more than about 30 arcsec. From April 2013, the ASTRO-H Soft X-ray telescopes (SXTs) have been calibrated at the new ISAS beam line.

      DOI: 10.1117/12.2055741

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    • Assembly of a MEMS-based Wolter type-I X-ray optic toward a future planetary exploration mission 査読有り

      Ikuyuki Mitsuishi, Yuichiro Ezoe, Tomohiro Ogawa, Takuya Kakiuchi, Masahiro Ikuta, Takayuki Hayashi, Toshiki Sato, Takaya Ohashi, Kazuhisa Mitsuda, Kohei Morishita, Kazuo Nakajima

      International Conference on Optical MEMS and Nanophotonics   115 - 116   2013年

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      記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

      We have been developing original MEMS-based X-ray optics toward future astronomical missions such as a planetary exploration mission. In this paper, we report results on the first X-ray irradiation test for a 2-stage MEMS-based optic. The obtained FWHM of the focusing image is 13±2 arcmin. However, an occultation effect and a deformation accuracy possibly affect a reduction of effective area. © 2013 IEEE.

      DOI: 10.1109/OMN.2013.6659086

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    ▼全件表示

    講演・口頭発表等

    • X線観測によるケプラーの超新星残骸の明るい塊構造の三次元速度測定

      佐藤 寿紀

      日本天文学会秋季年会  2017年9月 

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      記述言語:日本語   会議種別:口頭発表(一般)  

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    • In-flight Calibration Status of the Soft X-ray Telescopes (SXTs) onboad the Hitomi Satellite 国際会議

      佐藤 寿紀, alf of, Hitomi's SXT

      12th IACHEC meeting  2017年3月27日 

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      記述言語:英語   会議種別:口頭発表(一般)  

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    • カシオペア A の逆行衝撃波の固有運動とスペクトル変動の調査

      佐藤 寿紀

      日本天文学会春季年会  2017年3月 

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      記述言語:日本語   会議種別:口頭発表(一般)  

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    • Plasma Study of the Cassiopeia A Supernova Remnant 国際会議

      佐藤 寿紀

      Spectroscopy of Cosmic Plasma in the Era of ASTRO-H  2015年8月 

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      記述言語:英語   会議種別:口頭発表(一般)  

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    • Time variation of Cassiopeia A and a new evidence of the variation 国際会議

      佐藤 寿紀

      COSPAR MOSCOW 2014  2014年8月 

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      記述言語:英語   会議種別:口頭発表(一般)  

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    所属学協会

    共同研究・競争的資金等の研究

    • 44Ti専用硬X線望遠鏡で明らかにする銀河系内陽電子の起源

      日本学術振興会  科学研究費助成事業 若手研究 

      佐藤 寿紀

      詳細を見る

      2019年4月 - 2023年3月

      課題番号:19K14749

      担当区分:研究代表者  資金種別:競争的資金

      配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

      本研究では、銀河系内陽電子起源の有力候補として考えられているIa型超新星(Double Detonation model)の観測的証拠を掴むための観測機器の開発と観測研究を行なっている。Ia型超新星モデルの中でも、厚いHe外層の核燃焼の衝撃波で白色矮星の爆発を誘発するタイプのIa型超新星では、その外層の核燃焼時に大量の44Tiが合成されると考えられており、その崩壊時に放出される陽電子が我々の銀河内で供給されている可能性がある。つまり、Ia型超新星で44Tiが合成されている現場を捉えられれば、このIa型超新星の陽電子起源の最も強い証拠になる。
      我々は、この44Ti崩壊γ線(68 keV, 78 keV)の観測精度の飛躍的向上のため、ニューハンプシャー大やNASAと協力し、γ線TESカロリメータと硬X線望遠鏡を組み合わせた気球実験計画を進めている。今年度は米国の気球計画にプロポーザルを提出したが、未採択となったため、次回に向け再度提案書を作成している。硬X線望遠鏡の開発に関しては、多層膜研究をNASA/GSFCで開始した。Ni コーティングを可能にするため、新たなスパッタ装置を導入し、現在その立ち上げ作業を行なっており、次の年度から実際に膜付け研究を行う予定である。
      観測研究に関しては、Ia型超新星の残骸(ケプラーの超新星残骸)の膨張速度を Chandra 衛星のグレーティング観測で測定し、その三次元構造に迫った(Matthew et al. 2020, ApJ)。加えて、Ia型超新星の残骸の構造と超新星シミュレーションの構造を直接比較できる手法を開発した(Sato et al. 2019, ApJ)。これらの構造研究の他にも、超新星残骸内の元素組成に着目し、その爆発機構へ迫る研究を行なった(Sato et al. 2020a,b)。

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    • Constraint of the Nuclear Burning Condition in the Deep Core of the Massive Star’s Explosion

      理化学研究所  奨励課題 

      佐藤 寿紀

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      2019年9月 - 2021年3月

      担当区分:研究代表者  資金種別:競争的資金

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    • Ia型超新星の爆発機構解明に向けた観測的三次元モデルの構築

      日本学術振興会  科学研究費助成事業 研究活動スタート支援 

      佐藤 寿紀

      詳細を見る

      2018年8月 - 2020年3月

      課題番号:18H05865

      配分額:2210000円 ( 直接経費:1700000円 、 間接経費:510000円 )

      X線を用いた超新星残骸の観測研究に関して二本の共著論文を査読論文として出版し、一本の主著論文と一本の共著論文を査読誌へ投稿した。また、国際学会での口頭発表一件と天文学会年会でのポスター発表一件を行った。
      本研究ではIa型超新星残骸の三次元的構造から、その爆発機構の解明を目指した。特に、今年度は超新星残骸内に存在する塊状構造に着目し、これらがどのようにして形成されたかを議論するため「ジーナス統計」という手法を世界で初めて超新星残骸の観測研究に適応し、Ia型超新星残骸の三次元流体モデルとの比較を行った。結果として、これらの塊構造は爆発初期から存在していた事が示唆され、その形成過程は爆発機構を議論する上でも非常に重要なプロセスである事を指摘できた。本研究内容に関しては、米国 Astrophysical Journal 誌にて、現在査読中である。
      加えて、Ia型超新星残骸内のドップラー偏移に着目した三次元構造の調査に関連する研究も順調に進める事ができた(Kasuga, Sato+19, PASJ & Millard+19, submitted to ApJ)。これらの結果は今後、三次元超新星モデルとの比較により、爆発機構の同定の重要な情報になりうる。
      その他にも、超新星残骸 Cassiopeia A 内で起こる非熱的放射(宇宙線電子からのシンクロトロン放射)の時間変動に関して、多数の塊状の構造内を衝撃波が伝搬する際の、渦状乱流によって解析的に説明できる事を示し、Physical Review Letters 誌に掲載された(Fraschetti, Katsuda, Sato+18)。

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    • 44Tiの合成量に基づいた対称・非対称な重力崩壊型超新星爆発の元素合成の解明

      日本学術振興会  科学研究費助成事業 特別研究員奨励費 

      佐藤 寿紀

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      2016年4月 - 2018年3月

      課題番号:16J03448

      担当区分:研究代表者  資金種別:競争的資金

      配分額:1300000円 ( 直接経費:1300000円 )

      本研究の目的は、重力崩壊型超新星の44Tiの合成量を調査することで、爆発モデルに伴う元 素合成過程を明らかにすることであり、その実現のために、実験・観測の両面から研究を行った。本年度の研究成果を以下の3つに分けて記す。
      (I) 2016年に打ち上げられたひとみ衛星の軌道上キャリブレーションと観測研究を行った。ひとみ衛星に搭載された超精密X線分光システムは、Cassiopeia A内の44Tiが崩壊した後の44ScからのX線輝線検出が期待されていた。しかしながら、Cassiopeia A の観測前に運用停止となってしまったため、他の重力崩壊型超新星の残骸である、カニ星雲、G21.5-0.9、N132Dの観測研究を行った。カニ星雲では、爆発噴出物由来の熱的X線放射をこれまでにない精度で上限値を決める事に成功し、その爆発起源の推定を行った。N132Dに関しては、爆発噴出物の鉄が偏った方向に飛び交っている事を初めて示し、爆発の非対称性を議論する事が出来た。観測結果は、査読論文としてPASJから出版された。
      (II) Cassiopeia A は重力崩壊型超新星であり、本研究の鍵を握る44Tiからの崩壊ガンマ線が硬X線観測で発見されている数少ないサンプルである。今年度私は、この天体内の衝撃波で加速された宇宙線電子からの非熱的放射に着目した研究を行った。本研究では逆行する衝撃波に着目し、通常の前進している順行衝撃波よりも、それらの衝撃波速度が早くなっていることを観測的に初めて明らかにした。この結果は、査読論文(主著)として、APJ誌に掲載された。
      (III) Ia型超新星残骸ティコ、ケプラーの膨張速度をドップラー効果を用いる事で測定することに成功し、その三次元的な空間構造に迫る研究を行った。結果として、ティコとケプラーではそれぞれ対称、非対称な膨張であることがわかって来た。これらの研究内容は、それぞれ2本の査読論文(主著)として、APJ誌に掲載された。

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