| 1. |
- Currie, Thayne, et al.
(författare)
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Direct imaging and astrometric detection of a gas giant planet orbiting an accelerating star
- 2023
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Ingår i: Science. - 0036-8075 .- 1095-9203. ; 380:6641, s. 198-203
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Tidskriftsartikel (refereegranskat)abstract
- Direct imaging of gas giant exoplanets provides information on their atmospheres and the architectures of planetary systems. However, few planets have been detected in blind surveys with direct imaging. Using astrometry from the Gaia and Hipparcos spacecraft, we identified dynamical evidence for a gas giant planet around the nearby star HIP 99770. We confirmed the detection of this planet with direct imaging using the Subaru Coronagraphic Extreme Adaptive Optics instrument. The planet, HIP 99770 b, orbits 17 astronomical units from its host star, receiving an amount of light similar to that reaching Jupiter. Its dynamical mass is 13.9 to 16.1 Jupiter masses. The planet-to-star mass ratio [(7 to 8) × 10−3] is similar to that of other directly imaged planets. The planet’s atmospheric spectrum indicates an older, less cloudy analog of the previously imaged exoplanets around HR 8799.
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| 2. |
- Lawson, Kellen, et al.
(författare)
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SCExAO/CHARIS Near-infrared Integral Field Spectroscopy of the HD 15115 Debris Disk
- 2020
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 160:4
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Tidskriftsartikel (refereegranskat)abstract
- We present new, near-infrared (1.1-2.4 mu m) high-contrast imaging of the debris disk around HD 15115 with the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS). The SCExAO/CHARIS resolves the disk down to rho similar to 02 (r(proj) similar to 10 au), a factor of similar to 3-5 smaller than previous recent studies. We derive a disk position angle of PA similar to 2794-2805 and an inclination ofi similar to 853-86.2. While recent SPHERE/IRDIS imagery of the system could suggest a significantly misaligned two-ring disk geometry, CHARIS imagery does not reveal conclusive evidence for this hypothesis. Moreover, optimizing models of both one- and two-ring geometries using differential evolution, we find that a single ring having a Hong-like scattering phase function matches the data equally well within the CHARIS field of view (rho less than or similar to 1 ''). The disk's asymmetry, well evidenced at larger separations, is also recovered; the west side of the disk appears, on average, around 0.4 mag brighter across the CHARIS bandpass between 025 and 1 ''. Comparing Space Telescope Imaging Spectrograph (STIS) 50CCD optical photometry (2000-10500 A) with CHARIS near-infrared photometry, we find a red (STIS/50CCD-CHARIS broadband) color for both sides of the disk throughout the 04-1 '' region of overlap, in contrast to the blue color reported at similar wavelengths for regions exterior to similar to 2 ''. Further, this color may suggest a smaller minimum grain size than previously estimated at larger separations. Finally, we provide constraints on planetary companions and discuss possible mechanisms for the observed inner disk flux asymmetry and color.
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| 3. |
- Uyama, Taichi, et al.
(författare)
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Atmospheric Characterization and Further Orbital Modeling of kappa Andromeda b
- 2020
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 159:2
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Tidskriftsartikel (refereegranskat)abstract
- We present kappa Andromeda b's photometry and astrometry taken with Subaru/SCExAO+HiCIAO and Keck/NIRC2, combined with recently published SCExAO/CHARIS low-resolution spectroscopy and published thermal infrared photometry to further constrain the companion's atmospheric properties and orbit. The Y/Y-K colors of kappa And b are redder than field dwarfs, consistent with its youth and lower gravity. Empirical comparisons of its Y-band photometry and CHARIS spectrum to a large spectral library of isolated field dwarfs reaffirm the conclusion from Currie et al. that it likely has a low gravity but admit a wider range of most plausible spectral types (L0-L2). Our gravitational classification also suggests that the best-fit objects for kappa And b may have lower gravity than those previously reported. Atmospheric models lacking dust/clouds fail to reproduce its entire 1-4.7 mu m spectral energy distribution (SED), and cloudy atmosphere models with temperatures of similar to 1700-2000 K better match kappa And b data. Most well-fitting model comparisons favor 1700-1900 K, a surface gravity of log(g) similar to 4-4.5, and a radius of 1.3-1.6 R-Jup; the best-fit model (Drift-Phoenix) yields the coolest and lowest-gravity values: T-eff = 1700 K and log g = 4.0. An update to kappa And b's orbit with ExoSOFT using new astrometry spanning 7 yr reaffirms its high eccentricity (0.77 0.08). We consider a scenario where unseen companions are responsible for scattering kappa And b to a wide separation and high eccentricity. If three planets, including kappa And b, were born with coplanar orbits, and one of them was ejected by gravitational scattering, a potential inner companion with mass greater than or similar to 10 M-Jup could be located at less than or similar to 25 au.
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