TY - JOUR
T1 - Time-resolved rotational velocities in the upper atmosphere of WASP-33 b
AU - Wilson Cauley, P.
AU - Wang, Ji
AU - Shkolnik, Evgenya L.
AU - Ilyin, Ilya
AU - Strassmeier, Klaus G.
AU - Redfield, Seth
AU - Jensen, Adam G.
N1 - Publisher Copyright: © 2021. The American Astronomical Society. All rights reserved.
PY - 2021/3/1
Y1 - 2021/3/1
N2 - While steady empirical progress has been made in understanding the structure and composition of hot-planet atmospheres, direct measurements of velocity signatures, including winds, rotation, and jets, have lagged behind. Quantifying atmospheric dynamics of hot planets is critical for a complete understanding of their atmospheres, and such measurements may even illuminate other planetary properties, such as magnetic field strengths. In this manuscript we present the first detection of the Balmer lines Hα and Hβ in the atmosphere of the ultra-hot Jupiter WASP-33 b. Using atmospheric models that include the effects of atmospheric dynamics, we show that the shape of the average Balmer line transmission spectrum is consistent with rotational velocities in the planet’s thermosphere of vrot = 10.1-+1.00.8 km s-1. We also measure a low-significance day- to nightside velocity shift of -4.6-+3.43.4 km s-1 in the transmission spectrum, which is naturally explained by a global wind across the planet’s terminator. In a separate analysis the time-resolved velocity centroids of individual transmission spectra show unambiguous evidence of rotation, with a best-fit velocity of 10.0-+2.02.4 km s-1, consistent with the value of vrot derived from the shape of the average Balmer line transmission spectrum. Our observations and analysis confirm the power of time-resolved transmission spectra with a high signal-to-noise ratio to measure the velocity structures in exoplanet atmospheres. The high rotational and wind velocities we measure highlight the need for more detailed 3D global climate simulations of the rarefied upper atmospheres of ultra-hot gas giants.
AB - While steady empirical progress has been made in understanding the structure and composition of hot-planet atmospheres, direct measurements of velocity signatures, including winds, rotation, and jets, have lagged behind. Quantifying atmospheric dynamics of hot planets is critical for a complete understanding of their atmospheres, and such measurements may even illuminate other planetary properties, such as magnetic field strengths. In this manuscript we present the first detection of the Balmer lines Hα and Hβ in the atmosphere of the ultra-hot Jupiter WASP-33 b. Using atmospheric models that include the effects of atmospheric dynamics, we show that the shape of the average Balmer line transmission spectrum is consistent with rotational velocities in the planet’s thermosphere of vrot = 10.1-+1.00.8 km s-1. We also measure a low-significance day- to nightside velocity shift of -4.6-+3.43.4 km s-1 in the transmission spectrum, which is naturally explained by a global wind across the planet’s terminator. In a separate analysis the time-resolved velocity centroids of individual transmission spectra show unambiguous evidence of rotation, with a best-fit velocity of 10.0-+2.02.4 km s-1, consistent with the value of vrot derived from the shape of the average Balmer line transmission spectrum. Our observations and analysis confirm the power of time-resolved transmission spectra with a high signal-to-noise ratio to measure the velocity structures in exoplanet atmospheres. The high rotational and wind velocities we measure highlight the need for more detailed 3D global climate simulations of the rarefied upper atmospheres of ultra-hot gas giants.
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U2 - 10.3847/1538-3881/abde43
DO - 10.3847/1538-3881/abde43
M3 - Article
SN - 0004-6256
VL - 161
JO - Astronomical Journal
JF - Astronomical Journal
IS - 3
M1 - 152
ER -