HISAKI Project Team
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 特任助教
- ORCID ID
https://orcid.org/0000-0002-7962-4136- J-GLOBAL ID
- 202501003078234700
- researchmap会員ID
- R000092664
経歴
5-
2025年8月 - 現在
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2022年4月 - 2025年7月
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2020年2月 - 2022年3月
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2019年4月 - 2020年1月
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2017年4月 - 2019年3月
論文
85-
The Astrophysical Journal 1002(2) 222-222 2026年5月8日Abstract We present updated hard X-ray polarization measurements of the Crab pulsar and nebula obtained with the balloon-borne polarimeter XL-Calibur in the ∼19–64 keV energy range. During the flight, intermittent failure of the Global Positioning System (GPS) receiver resulted in poorly constrained timing for ∼38% of the Crab dataset. By implementing a new phase recovery method that reconstructs timing during extended GPS-off intervals, phase tag data are recovered for ∼95% of the GPS-off dataset, increasing the precision of the phase-resolved analysis. Phase information for the data is recovered by using the Crab pulsar, with its 33 ms period, as an external timing source. Using a Markov Chain Monte Carlo framework to jointly fit phase offsets and frequency derivatives, sufficient phase accuracy is achieved across multiple periods without GPS for a phase-resolved analysis. This enables inclusion of nearly the full dataset in the polarization study. The polarization degree of the nebular emission is found to be (27.7 ± 4.9)% at a polarization angle of 127 2 ± 5 1, confirming previous XL-Calibur results and remaining aligned with the Crab’s spin axis, consistent with synchrotron emission from the inner nebula. Phase-resolved measurements show that the off-pulse and bridge intervals exhibit a strong polarization, while the pulsar peaks, although weakly constrained, remain in agreement with the softer-energy trends of IXPE. These findings reinforce a scenario in which hard X-ray emission arises primarily in the nebular torus and wind regions. The successful recovery of precise phase tagging from GPS-off data demonstrates the capacity to use the pulsar as an external clock even in the case of sparsely populated data.
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Publications of the Astronomical Society of Japan 2026年4月28日Abstract We present the first high-resolution spectroscopy of the black hole high-mass X-ray binary Cygnus X-1 with XRISM, including orbital-phase-resolved analyses and tentative evidence of short-term variability in the Fe K band on second timescales. Using data from the Performance Verification phase in 2024 April, we analyzed spectral variability across orbital phases with the Resolve microcalorimeter and the Xtend CCD imager. The unprecedented resolution of Resolve reveals variability in highly ionized Fe absorption lines. The absorption features show orbital-phase-dependent variability in column density, ionization state, and blueshifted velocity, suggesting structural variations in the focused stellar wind along the line of sight. We also find indications of subtle broadening of the neutral Fe emission profile. In addition, intensity-sorted spectroscopy during dip phases suggests possible variability on timescales of a few seconds in the absorption features, consistent with cooler, denser, and lower-ionized gas clumps. Although the statistical significance is limited, these results hint that the stellar wind and the X-rays from the accretion disk around the black hole may interact on timescales as short as a few seconds. These XRISM results constrain wind-fed accretion in Cyg X-1 and highlight Resolve’s capability to probe plasma environments in high-mass X-ray binaries.
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The Astrophysical Journal Letters 2026年4月20日
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Nature Astronomy 2026年3月31日
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Nature 651(8107) 909-913 2026年3月25日
MISC
44講演・口頭発表等
104所属学協会
3-
2013年12月 - 現在
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- 現在
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- 現在
共同研究・競争的資金等の研究課題
3-
日本学術振興会 科学研究費助成事業 2021年4月 - 2024年3月
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日本学術振興会 科学研究費助成事業 2019年4月 - 2022年3月
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日本学術振興会 科学研究費助成事業 2017年4月 - 2019年3月
