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Sökning: WFRF:(Takahashi Yasuhiro H.)

  • Resultat 11-13 av 13
  • Föregående 1[2]
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11.
  • Ryu, Tsuguru, et al. (författare)
  • HIGH-CONTRAST IMAGING OF INTERMEDIATE-MASS GIANTS WITH LONG-TERM RADIAL VELOCITY TRENDS
  • 2016
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 825:2
  • Tidskriftsartikel (refereegranskat)abstract
    • A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to gamma Hya B (0.61(-0.14)(+0.12)M(circle dot)), HD 5608 B (0.10 +/- 0.01M(circle dot)), and HD 109272 B (0.28 +/- 0.06M(circle dot)). For the remaining targets (iota Dra, 18 Del, and HD 14067), we exclude companions more massive than 30-60 M-Jup at projected separations of 1 ''-7 ''. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets iota Dra b, HD 5608 b, and HD 14067 b.
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12.
  • Yang, Yi, et al. (författare)
  • High-contrast Polarimetry Observation of the T Tau Circumstellar Environment
  • 2018
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 861:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We conducted high-contrast polarimetry observations of T Tau in the H-band, using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics instrument mounted on the Subaru Telescope, revealing structures as near as 0 1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebulalike envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearly face-on circumstellar disk of T Tau N is no larger than 0.''8, or 117 au, in the northwest, based on the existence of a hole in this direction, and no larger than 0.''27, or 40 au, in the south. A new structure, N5, extends to about 0.''42, or 59 au, southwest of the star, and is believed to be part of the disk. We suggest that T Tau S is surrounded by a highly inclined circumbinary disk with a radius of about 0.''3, or 44 au, with a position angle of about 30 degrees, that is misaligned with the orbit of the T Tau S binary. After analyzing the positions and polarization vector patterns of the outflow-related structures, we suggest that T Tau S should trigger the well-known E-W outflow, and is also likely to be responsible for a southwest precessing outflow coil and a possible south outflow.
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13.
  • Yang, Yi, et al. (författare)
  • NEAR-INFRARED IMAGING POLARIMETRY OF INNER REGION OF GG TAU A DISK
  • 2017
  • Ingår i: Astronomical Journal. - 0004-6256 .- 1538-3881. ; 153:1
  • Tidskriftsartikel (refereegranskat)abstract
    • By performing non-masked polarization imaging with Subaru/HiCIAO, polarized scattered light from the inner region of the disk around the GG Tau A system was successfully detected in the H band, with a spatial resolution of approximately 0 07, revealing the complicated inner disk structures around this young binary. This paper reports the observation of an arc-like structure to the north of GG Tau Ab, and part of a circumstellar structure that is noticeable around GG Tau Aa, extending to a distance of approximately 28 au from the primary star. The speckle noise around GG Tau Ab constrains its disk radius to < 13 au. Based on the size of the circumbinary ring and the circumstellar disk around GG Tau Aa, the semimajor axis of the binary's orbit is likely to be 62 au. A comparison of the present observations with previous Atacama Large Millimeter Array and near-infrared H-2 emission observations suggests that the north arc could be part of a large streamer flowing from the circumbinary ring to sustain the circumstellar disks. According to the previous studies, the circumstellar disk around GG Tau Aa has enough mass and can sustain itself for a duration sufficient for planet formation; thus, our study indicates that planets can form within close (separation. 100 au) young binary systems.
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  • Resultat 11-13 av 13
  • Föregående 1[2]
 
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