Exoplanets & Exomoons

CRIRES+ Transmission Spectroscopy of WASP-127b. Detection Of The Resolved Signatures Of A Supersonic Equatorial Jet And Cool Poles In A Hot Planet

By Keith Cowing
Press Release
April 20, 2024
Filed under , , , , , , , , , , ,
CRIRES+ Transmission Spectroscopy of WASP-127b. Detection Of The Resolved Signatures Of A Supersonic Equatorial Jet And Cool Poles In A Hot Planet
Different scenarios of super-rotating atmospheric material. Panels a, b and c show the scenario of a homogeneously rotating planet. The purple solid line shows the velocity kernel of the material at rotation consistent with tidally locked rotation (panel b) and the resulting shape of the cross-correlation function (panel c). The turquoise dashed line shows the effect of the planet rotating approximately six times faster. Panels d, e and f show two cases of a super-rotating equatorial jet, with the poles rotating at tidally locked velocities. The difference between the two cases is the opening angle of the equatorial region (35◦ orange dashed, and 65◦ solid green). Panels g, h and i explore the case of the velocity kernel of a super-rotating equatorial jet (blue and red solid lines in panel h) with the polar region represented by the velocity kernel of super-rotating velocity (grey dash-dotted line) or tidally locked velocity (grey dotted line) but not contributing to the transmission spectrum due to muted atmospheric features, leading in both cases to only two peaks in the CCF (panel i). — astro-ph.EP

General circulation models of gas giant exoplanets predict equatorial jets that drive inhomogeneities across the planetary atmosphere. We studied the transmission spectrum of the hot Jupiter WASP-127b during one transit in the K band with CRIRES+.

Telluric and stellar signals were removed from the data using SYSREM and the planetary signal was investigated using the cross-correlation (CCF) technique. After detecting a spectral signal indicative of atmospheric inhomogeneities, we employed a Bayesian retrieval framework with a 2D modelling approach tailored to address this scenario. We detected strong signals of H2O and CO, which exhibited not one but two distinct CCF peaks.

The double peaked signal can be explained by a supersonic equatorial jet and muted signals at the poles, with the two peaks representing the signals from the planet’s morning and evening terminators, respectively. We calculated an equatorial jet velocity of 7.7±0.2km/s from our retrieved overall equatorial velocity and the planet’s tidally locked rotation, and derive distinct atmospheric properties for the two terminators as well as the polar region.

The evening terminator is found to be hotter than the morning terminator by 175+116−133K and the muted signals from the poles can be explained by significantly lower temperatures or a high cloud deck. Our retrieval yields a solar C/O ratio and metallicity and challenges previous studies of WASP-127b’s atmosphere. The presence of a double peaked signal highlights the importance of accounting for planetary 3D structure during interpretation of atmospheric signals.

The measured supersonic jet velocity and the lack of signal from the polar regions, representing a detection of latitudinal inhomogeneity in a spatially unresolved target, showcases the power of high-resolution transmission spectroscopy for the characterization of global circulation in exoplanets.

L. Nortmann, F. Lesjak, F. Yan, D. Cont, S. Czesla, A. Lavail, A. D. Rains, E. Nagel, L. Boldt-Christmas, A. Hatzes, A. Reiners, N. Piskunov, O. Kochukhov, U. Heiter, D. Shulyak, M. Rengel, U. Seemann

Comments: 18 pages 13 figures, submitted to Astronomy & Astrophysics (A&A)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2404.12363 [astro-ph.EP] (or arXiv:2404.12363v1 [astro-ph.EP] for this version)
Submission history
From: Lisa Nortmann
[v1] Thu, 18 Apr 2024 17:45:49 UTC (4,696 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻