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Sökning: WFRF:(Yamashita Satoshi)

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1.
  • Morokuma, Tomoki, et al. (författare)
  • OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSSJ110006.07+442144.3
  • 2017
  • Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 69:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSSJ110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to similar to 5 mu m in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of alpha(upsilon) similar to -1.4, where f(v) proportional to v(alpha upsilon), synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seemsmost plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low.peak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations.
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2.
  • Yabuta, Hikaru, et al. (författare)
  • Macromolecular organic matter in samples of the asteroid (162173) Ryugu
  • 2023
  • Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 379:6634
  • Tidskriftsartikel (refereegranskat)abstract
    • Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugus parent body.
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