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 教授東京大学 大学院理学系研究科 物理学専攻 教授
- 学位
- 博士(理学)(東京大学)修士(理学)(東京大学)
- J-GLOBAL ID
- 200901060914122911
- researchmap会員ID
- 1000363024
- 外部リンク
研究キーワード
5研究分野
1委員歴
3-
2014年4月 - 現在
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2011年9月 - 現在
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2006年 - 2009年
受賞
2論文
382-
Astronomy & Astrophysics 2023年10月
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The Astrophysical Journal 2023年8月1日
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The Astrophysical Journal 2023年7月1日
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The Astronomical Journal 165(4) 162-162 2023年3月17日Abstract The Subaru telescope is currently performing a strategic program (SSP) using the high-precision near-infrared (NIR) spectrometer IRD to search for exoplanets around nearby mid/late M dwarfs via radial velocity (RV) monitoring. As part of the observing strategy for the exoplanet survey, signatures of massive companions such as RV trends are used to reduce the priority of those stars. However, this RV information remains useful for studying the stellar multiplicity of nearby M dwarfs. To search for companions around such “deprioritized” M dwarfs, we observed 14 IRD-SSP targets using Keck/NIRC2 with pyramid wave-front sensing at NIR wavelengths, leading to high sensitivity to substellar-mass companions within a few arcseconds. We detected two new companions (LSPM J1002+1459 B and LSPM J2204+1505 B) and two new candidates that are likely companions (LSPM J0825+6902 B and LSPM J1645+0444 B), as well as one known companion. Including two known companions resolved by the IRD fiber injection module camera, we detected seven (four new) companions at projected separations between ∼2 and 20 au in total. A comparison of the colors with the spectral library suggests that LSPM J2204+1505 B and LSPM J0825+6902 B are located at the boundary between late M and early L spectral types. Our deep high-contrast imaging for targets where no bright companions were resolved did not reveal any additional companion candidates. The NIRC2 detection limits could constrain potential substellar-mass companions (∼10–75 MJup) at 10 au or further. The failure with Keck/NIRC2 around the IRD-SSP stars having significant RV trends makes these objects promising targets for further RV monitoring or deeper imaging with the James Webb Space Telescope to search for smaller-mass companions below the NIRC2 detection limits.
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The Astronomical Journal 2023年2月1日
MISC
674-
日本物理学会講演概要集 64 217-217 2009年
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日本機械学会スターリングサイクルシンポジウム講演論文集 12th 63-64 2009年The 20K-class Double-staged Stirling cooler is a key cryogenic technology for cooling the optical detectors and telescopes of the highly-sophisticated astronomy satellite missions proposed by JAXA, for instance, the x-ray astronomy mission Astro-H(2013) and the cryogenic infrared telescope mission SPICA(2018). Therefore, it is required that the advanced double-staged Stirling cooler with improvement of mechanical reliability and cooling performance will be developed, based on the existing one onboard the first Japanese infrared astronomy mission Akari(2006) with cooling power of 200mW at 20K (90W power input). This paper describes about development status of the advanced double-staged Stirling cooler with cooling performance and long lifetime test.
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Publications of the Astronomical Society of Japan 61(4) 737-750 2009年We present the characterization and calibration of the Slow-Scan observation mode of the Far-Infrared Surveyor (FIS) onboard the AKARI satellite. The FIS, one of the two focal-plane instruments on AKARI, has four photometric bands between 50-180 μm with two types of Ge:Ga array detectors. In addition to the All-Sky Survey, FIS has also taken detailed far-infrared images of selected targets by using the Slow-Scan mode. The sensitivity of the Slow-Scan mode is one to two orders of magnitude better than that of the All-Sky Survey, because the exposure time on a targeted source is much longer. The point spread functions (PSFs) were obtained by observing several bright point-like objects, such as asteroids, stars, and galaxies. The derived full widths at the half maximum (FWHMs) are ∼30" for the two shorter wavelength bands and ∼40" for the two longer wavelength bands, being consistent with those expected by optical simulation, although a certain amount of excess is seen in the tails of the PSFs. A flux calibration was performed by observations of well-established photometric calibration standards (asteroids and stars) over a wide range of fluxes. After establishing the method of aperture photometry, the photometric accuracy for point-sources is better than ±15% in all of the bands, expect for the longest wavelength. © 2009. Astronomical Society of Japan.
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Astrophysical Journal 695(1 PART 2) L88-L91 2009年Photometry of the A0 V main-sequence star HD 106797 with AKARI and Gemini/T-ReCS is used to detect excess emission over the expected stellar photospheric emission between 10 and 20 μm, which is best attributed to hot circumstellar debris dust surrounding the star. The temperature of the debris dust is derived as T ∼ 190 K by assuming that the excess emission is approximated by a single temperature blackbody. The derived temperature suggests that the inner radius of the debris disk is ∼14 AU. The fractional luminosity of the debris disk is 1000 times brighter than that of our own zodiacal cloud. The existence of such a large amount of hot dust around HD 106797 cannot be accounted for by a simple model of the steady state evolution of a debris disk due to collisions, and it is likely that transient events play a significant role. Our data also show a narrow spectral feature between 11 and 12 μm attributable to crystalline silicates, suggesting that dust heating has occurred during the formation and evolution of the debris disk of HD 106797. © 2009. The American Astronomical Society. All rights reserved. d
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Publications of the Astronomical Society of Japan 60(SPECIAL ISUE) S531-S542 2008年There is a huge gap between the properties of red-sequence selected massive galaxy clusters at z < 1 and Lyman-break selected proto-clusters at z > 3. It is important to understand when and how the z > 3 proto-clusters evolve into passive clusters at z < 1. We aim to fill this cluster desert by using space-based N4 (4 μm) imaging with AKARI. The z′- N4 color is a powerful separator of cluster galaxies at z > 1, taking advantage of the 4000 Å break and the 1.6 μm bump. We carefully selected 16 promising cluster candidates at 0.9 < z < 1.7, which all show an obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared S /S flux ratio is an extinction-free indicator of galaxy star-formation activity due to the redshifted PAH emission lines (6.2, 7.7, and 8.6 μm). We show statistically that the cluster galaxies have a lower S /S flux ratio than do field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9 < z < 1.7, pushing the formation epoch of these galaxy clusters to a higher redshift. © 2008. Astronomical Society of Japan. 15μm 9μm 15μm 9μm
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Applied Optics 46(11) 2049-2056 2007年4月We report on the microscopic surface structure of carbon-fiber-reinforced silicon carbide (C/SiC) composite mirrors that have been improved for the Space Infrared Telescope for Cosmology and Astrophysics (SPICA) and other cooled telescopes. The C/SiC composite consists of carbon fiber, silicon carbide, and residual silicon. Specific microscopic structures are found on the surface of the bare C/SiC mirrors after polishing. These structures are considered to be caused by the different hardness of those materials. The roughness obtained for the bare mirrors is 20 nm rms for flat surfaces and 100 nm rms for curved surfaces. It was confirmed that a SiSiC slurry coating is effective in reducing the roughness to 2 nm rms. The scattering properties of the mirrors were measured at room temperature and also at 95 K. No significant change was found in the scattering properties through cooling, which suggests that the microscopic surface structure is stable with changes in temperature down to cryogenic values. The C/SiC mirror with the SiSiC slurry coating is a promising candidate for the SPICA telescope. © 2007 Optical Society of America.
共同研究・競争的資金等の研究課題
49-
日本学術振興会 科学研究費助成事業 2023年4月 - 2028年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2024年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2026年3月
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日本学術振興会 科学研究費助成事業 2023年6月 - 2025年3月
● 専任大学名
1-
専任大学名東京大学（University of Tokyo)
