| 1. |
- Aharonian, Felix, et al.
(författare)
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Hitomi X-ray observation of the pulsar wind nebula G21.5-0.9
- 2018
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 70:3
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Tidskriftsartikel (refereegranskat)abstract
- We present results from the Hitomi X-ray observation of a young composite-type supernova remnant (SNR) G21.5-0.9, whose emission is dominated by the pulsar wind nebula (PWN) contribution. The X-ray spectra in the 0.8-80 keV range obtained with the Soft X-ray Spectrometer (SXS), Soft X-ray Imager, and Hard X-ray Imager (HXI) show a significant break in the continuum as previously found with the NuSTAR observation. After taking into account all known emissions from the SNR other than the PWN itself, we find that the Hitomi spectra can be fitted with a broken power law with photon indices of Gamma(1) = 1.74 +/- 0.02 and Gamma(2) = 2.14 +/- 0.01 below and above the break at 7.1 +/- 0.3 keV, which is significantly lower than the NuSTAR result (similar to 9.0 keV). The spectral break cannot be reproduced by time-dependent particle injection one-zone spectral energy distribution models, which strongly indicates that a more complex emission model is needed, as suggested by recent theoretical models. We also search for narrow emission or absorption lines with the SXS, and perform a timing analysis of PSR J1833-1034 with the HXI and the Soft Gamma-ray Detector. No significant pulsation is found from the pulsar. However, unexpectedly, narrow absorption line features are detected in the SXS data at 4.2345 keV and 9.296 keV with a significance of 3.65 sigma. While the origin of these features is not understood, their mere detection opens up a new field of research and was only possible with the high resolution, sensitivity, and ability to measure extended sources provided by an X-ray microcalorimeter.
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| 2. |
- Aharonian, Felix, et al.
(författare)
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Hitomi X-ray studies of giant radio pulses from the Crab pulsar
- 2018
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Ingår i: Publications of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 0004-6264 .- 2053-051X. ; 70:2
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Tidskriftsartikel (refereegranskat)abstract
- To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2-300 keV band and the Kashima NICT radio telescope in the 1.4-1.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 sigma fluctuations of the X-ray fluxes at the pulse peaks, and the 3 sigma upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2-300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.5-10 keV and 70-300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) x 10(-11) erg cm(-2), respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magneto-sphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a > 0.02% brightening of the pulse-peak flux under such conditions.
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| 3. |
- Kobayashi, Shintaro, et al.
(författare)
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Linear Trimer Formation with Antiferromagnetic Ordering in 1 T-CrSe2 Originating from Peierls-like Instabilities and Interlayer Se-Se Interactions
- 2019
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 58:21, s. 14304-14315
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Tidskriftsartikel (refereegranskat)abstract
- Anomalous successive structural transitions in layered 1T-CrSe 2 with an unusual Cr 4+ valency were investigated by synchrotron X-ray diffraction. 1T-CrSe 2 exhibits dramatic structural changes in in-plane Cr-Cr and interlayer Se-Se distances, which originate from two interactions: (i) in-plane Cr-Cr interactions derived from Peierls-like trimerization instabilities on the orbitally assisted one-dimensional chains and (ii) interlayer Se-Se interactions through p-p hybridization. As a result, 1T-CrSe 2 has the unexpected ground state of an antiferromagnetic metal with multiple Cr linear trimers with three-center-two-electron σ bonds. Interestingly, partial substitution of Se for S atoms in 1T-CrSe 2 changes the ground state from an antiferromagnetic metal to an insulator without long-range magnetic ordering, which is due to the weakening of interlayer interactions between anions. The unique low-temperature structures and electronic states of this system are determined by the competition and cooperation of in-plane Cr-Cr and interlayer Se-Se interactions.
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| 4. |
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| 5. |
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| 6. |
- Umegaki, Izumi, et al.
(författare)
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Magnetic phase diagram of Eu 1- x Ca x Co 2 P 2 determined using muon spin rotation and relaxation
- 2024
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 109:14
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigated the magnetic nature of a solid solution system consisting of EuCo2P2 and CaCo2P2 using a muon spin rotation and relaxation (mu +SR) technique, which is sensitive to local magnetic environments. The former compound EuCo2P2 is known to enter an incommensurate helical antiferromagnetic (AF) phase below 66 K with neutrons, which was confirmed by the present mu +SR. The magnitude of the ordered Eu moments proposed with neutrons was found to be consistent with that estimated by mu +SR. Furthermore, the latter lattice-collapsed tetragonal phase compound CaCo2P2 is known to enter an A-type AF phase below 90 K, and mu +SR measurements on single crystals revealed the presence of a spin reorientation transition at around 40 K, below which the A-type AF order is likely to be completed. Although all Eu1-xCaxCo2P2 compounds were found to enter a magnetic phase at low temperatures regardless of x, a static ordered state was formed only at the vicinity of the two end compounds, i.e., 0 x 0.4 and 0.9 x 1. Instead, a disordered state, i.e., a random spin-glass state, short-range ordered state, or highly fluctuating state was found in the x range between 0.4 and 0.9, even at the lowest measured temperature (2 K). Together with the magnetization data, our findings clarified the magnetic phase diagram of Eu1-xCaxCo2P2, where a ferromagnetic exchange interaction between Co ions through the Eu2+ ion competes with a direct AF interaction among the Co ions, particularly in the x range between 0.57 and 0.9. This competition yielded multiple phases in Eu1-xCaxCo2P2.
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| 7. |
- Umegaki, Izumi, et al.
(författare)
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Magnetic phase diagram of Eu1−?Ca?Co2P2 determined using muon spin rotation and relaxation
- 2024
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 109:14
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigated the magnetic nature of a solid solution system consisting of EuCo2P2 and CaCo2P2 using a muon spin rotation and relaxation (?+SR) technique, which is sensitive to local magnetic environments. The former compound EuCo2P2 is known to enter an incommensurate helical antiferromagnetic (AF) phase below 66 K with neutrons, which was confirmed by the present ?+SR. The magnitude of the ordered Eu moments proposed with neutrons was found to be consistent with that estimated by ?+SR. Furthermore, the latter lattice-collapsed tetragonal phase compound CaCo2P2 is known to enter an ?-type AF phase below 90 K, and ?+SR measurements on single crystals revealed the presence of a spin reorientation transition at around 40 K, below which the ?-type AF order is likely to be completed. Although all Eu1−?Ca?Co2P2 compounds were found to enter a magnetic phase at low temperatures regardless of ?, a static ordered state was formed only at the vicinity of the two end compounds, i.e., 0≤?≤0.4 and 0.9≤?≤1. Instead, a disordered state, i.e., a random spin-glass state, short-range ordered state, or highly fluctuating state was found in the ? range between 0.4 and 0.9, even at the lowest measured temperature (2 K). Together with the magnetization data, our findings clarified the magnetic phase diagram of Eu1−?Ca?Co2P2, where a ferromagnetic exchange interaction between Co ions through the Eu2+ ion competes with a direct AF interaction among the Co ions, particularly in the ? range between 0.57 and 0.9. This competition yielded multiple phases in Eu1−?Ca?Co2P2.
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| 8. |
- Yanagisawa, Akihiro, et al.
(författare)
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Knee osteoarthritis associated with different kinds of amyloid deposits and the impact of aging on type of amyloid
- 2016
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Ingår i: Amyloid. - : Informa UK Limited. - 1350-6129 .- 1744-2818. ; 23:1, s. 26-32
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Tidskriftsartikel (refereegranskat)abstract
- Amyloidosis is a protein conformational disorder in which amyloid fibrils accumulate in the extracellular space and induce organ dysfunction. Recently, two different amyloidogenic proteins, transthyretin (TTR) and apolipoprotein A-I (Apo A-I), were identified in amyloid deposits in knee joints in patients with knee osteoarthritis (OA). However, clinicopathological differences related to those two kinds of amyloid deposits in the knee joint remain to be clarified. Here, we investigated the clinicopathological features related to these knee amyloid deposits associated with knee OA and the biochemical characteristics of the amyloid deposits. We found that all of our patients with knee OA had amyloid deposits in the knee joints, especially in the meniscus, and those deposits were primarily derived from TTR and/or Apo A-I. Some patients with knee OA, however, had unclassified amyloid deposits. One of our interesting observations concerned the different effects of aging on each type of amyloid formed. The frequency of formation of ATTR deposits clearly increased with age, but that of AApo A-I deposits decreased. Furthermore, we found that similar to 16% of patients with knee OA developed ATTR/AApo A-I double deposits in the meniscus. Amyloid deposition may therefore be a common histopathological feature associated with knee OA. Also, aging may induce ATTR formation in the knee joint in elderly patients with knee OA, whereas AApo A-I formation may be inversely correlated with age.
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