Is the Atmosphere of the Ultra-hot Jupiter WASP-121 b Variable?
Journal article, 2024
We present a comprehensive analysis of the Hubble Space Telescope observations of the atmosphere of WASP-121 b, an ultra-hot Jupiter. After reducing the transit, eclipse, and phase-curve observations with a uniform methodology and addressing the biases from instrument systematics, sophisticated atmospheric retrievals are used to extract robust constraints on the thermal structure, chemistry, and cloud properties of the atmosphere. Our analysis shows that the observations are consistent with a strong thermal inversion beginning at similar to 104 Pa on the dayside, solar to subsolar metallicity Z (i.e., -0.77<log(Z)<0.05 ), and supersolar C/O ratio (i.e., 0.59 < C/O < 0.87). More importantly, utilizing the high signal-to-noise ratio and repeated observations of the planet, we identify the following unambiguous time-varying signals in the data: (i) a shift of the putative hotspot offset between the two phase curves and (ii) varying spectral signatures in the transits and eclipses. By simulating the global dynamics of WASP-121 b's atmosphere at high resolution, we show that the identified signals are consistent with quasiperiodic weather patterns, hence atmospheric variability, with signatures at the level probed by the observations (similar to 5% to similar to 10%) that change on a timescale of similar to 5 planet days; in the simulations, the weather patterns arise from the formation and movement of storms and fronts, causing hot (as well as cold) patches of atmosphere to deform, separate, and mix in time.
Author
Q. Changeat
University College London (UCL)
European Space Agency (ESA)
J. W. Skinner
California Institute of Technology (Caltech)
Brandeis University
J. y-k. Cho
Flatiron Institute
Brandeis University
J. Nattila
Flatiron Institute
Columbia University
I. P. Waldmann
University College London (UCL)
A. F. Al-Refaie
University College London (UCL)
A. Dyrek
University Paris-Saclay
B. Edwards
Netherlands Institute for Space Research (SRON)
University College London (UCL)
T. Mikal-Evans
Max Planck Society
M. Joshua
Blue Skies Space Ltd
Giuseppe Morello
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
N. Skaf
University of California
A. Tsiaras
University College London (UCL)
O. Venot
Paris Cité University
Univ Paris Est Creteil
K. H. Yip
University College London (UCL)
Astrophysical Journal, Supplement Series
0067-0049 (ISSN) 1538-4365 (eISSN)
Vol. 270 2 34Subject Categories (SSIF 2011)
Physical Sciences
DOI
10.3847/1538-4365/ad1191