Spitzer Phase-curve Observations and Circulation Models of the Inflated Ultrahot Jupiter WASP-76b

Abstract The large radii of many hot Jupiters can only be matched by models that have hot interior adiabats, and recent theoretical work has shown that the interior evolution of hot Jupiters has a significant impact on their atmospheric structure. Due to its inflated radius, low gravity, and ultraho...

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Bibliographic Details
Published in:The Astronomical journal 2021-10, Vol.162 (4), p.158
Main Authors: May, Erin M., Komacek, Thaddeus D., Stevenson, Kevin B., Kempton, Eliza M.-R., Bean, Jacob L., Malik, Matej, Ih, Jegug, Mansfield, Megan, Savel, Arjun B., Deming, Drake, Desert, Jean-Michel, Feng, Y. Katherina, Fortney, Jonathan J., Kataria, Tiffany, Lewis, Nikole, Morley, Caroline, Rauscher, Emily, Showman, Adam
Format: Article
Language:English
Subjects:
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ATMOSPHERES
Atmospheric dynamics
Atmospheric models
Atmospheric structure
BRIGHTNESS
Brightness temperature
CLOUDS
Cold
Controlled atmospheres
Drag
Evolution
Exoplanet astronomy
Exoplanet atmospheres
Extrasolar planets
Gas giant planets
GENERAL CIRCULATION MODELS
GRAVITATION
Hot Jupiters
Jupiter
JUPITER PLANET
Model matching
Offsets
Planetary atmospheres
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Summary:Abstract The large radii of many hot Jupiters can only be matched by models that have hot interior adiabats, and recent theoretical work has shown that the interior evolution of hot Jupiters has a significant impact on their atmospheric structure. Due to its inflated radius, low gravity, and ultrahot equilibrium temperature, WASP-76b is an ideal case study for the impact of internal evolution on observable properties. Hot interiors should most strongly affect the nonirradiated side of the planet, and thus full phase-curve observations are critical to ascertain the effect of the interior on the atmospheres of hot Jupiters. In this work, we present the first Spitzer phase-curve observations of WASP-76b. We find that WASP-76b has an ultrahot dayside and relatively cold nightside with brightness temperatures of 2471 ± 27 K/1518 ± 61 K at 3.6 μ m and 2699 ± 32 K/1259 ± 44 K at 4.5 μ m, respectively. These results provide evidence for a dayside thermal inversion. Both channels exhibit small phase offsets of 0.68 ± 0.°48 at 3.6 μ m and 0.67 ± 0.°2 at 4.5 μ m. We compare our observations to a suite of general circulation models (GCMs) that consider two endmembers of interior temperature along with a broad range of frictional drag strengths. Strong frictional drag is necessary to match the small phase offsets and cold nightside temperatures observed. From our suite of cloud-free GCMs, we find that only cases with a cold interior can reproduce the cold nightsides and large phase-curve amplitude at 4.5 μ m, hinting that the hot interior adiabat of WASP-76b does not significantly impact its atmospheric dynamics or that clouds blanket its nightside.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/ac0e30