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Träfflista för sökning "WFRF:(Kanagawa Kazuhiro D.) "

Sökning: WFRF:(Kanagawa Kazuhiro D.)

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1.
  • Momose, Munetake, et al. (författare)
  • Detailed structure of the outer disk around HD169142 with polarized light in H-band
  • 2015
  • Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - 0004-6264. ; 67:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Coronagraphic imagery of the circumstellar disk around HD 169142 in H-band polarized intensity (PI) with Subaru/HiCIAO is presented. The emission scattered by dust particles at the disk surface in 0.2 <= r <= 1.2, or 29 <= r <= 174 AU, is successfully detected. The azimuthally-averaged radial profile of the PI shows a double power-law distribution, in which the PIs in r=29-52 AU and r=81.2-145 AU respectively show r(-3)-dependence. These two power-law regions are connected smoothly with a transition zone (TZ), exhibiting an apparent gap in r=40-70 AU. The PI in the inner power-law region shows a deep minimum whose location seems to coincide with the point source at lambda = 7 mm. This can be regarded as another sign of a protoplanet in TZ. The observed radial profile of the PI is reproduced by a minimally flaring disk with an irregular surface density distribution or with an irregular temperature distribution or with the combination of both. The depletion factor of surface density in the inner power-law region (r<50 AU) is derived to be >= 0.16 from a simple model calculation. The obtained PI image also shows small scale asymmetries in the outer power-law region. Possible origins for these asymmetries include corrugation of the scattering surface in the outer region, and shadowing effect by a puffed up structure in the inner power-law region.
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2.
  • Ida, Shigeru, et al. (författare)
  • Slowing Down Type II Migration of Gas Giants to Match Observational Data
  • 2018
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X. ; 864:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The mass and semimajor axis distribution of gas giants in exoplanetary systems obtained by radial velocity surveys shows that super-Jupiter-mass planets are piled up at 1 au, while Jupiter/sub-Jupiter-mass planets are broadly distributed from ∼0.03 au to beyond 1 au. This feature has not been explained by theoretical predictions. In order to reconcile this inconsistency, we investigate evolution of gas giants with a new type II migration formula by Kanagawa et al., by comparing the migration, growth timescales of gas giants, and disk lifetime, and by population synthesis simulation. While the classical migration model assumes that a gas giant opens up a clear gap in the protoplanetary disk and the planet migration is tied to the disk gas accretion, recent high-resolution simulations show that the migration of gap-opening planets is decoupled from the disk gas accretion and Kanagawa et al. proposed that type II migration speed is nothing other than type I migration speed with the reduced disk gas surface density in the gap. We show that with this new formula, type II migration is significantly reduced for super-Jupiter-mass planets, if the disk accretion is driven by the disk wind as suggested by recent magnetohydrodynamic simulations. Population synthesis simulations show that super-Jupiter-mass planets remain at 1 au without any additional ingredient such as disk photoevaporation. Therefore, the mystery of the pile-up of gas giants at 1 au will be theoretically solved if the new formula is confirmed and wind-driven disk accretion dominates.
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