Atmospheres & Climate

Phase-resolving the Absorption Signatures of Water and Carbon Monoxide in the Atmosphere of the Ultra-hot Jupiter WASP-121b with GEMINI-S/IGRINS

By Keith Cowing
Status Report
July 9, 2024
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Phase-resolving the Absorption Signatures of Water and Carbon Monoxide in the Atmosphere of the Ultra-hot Jupiter WASP-121b with GEMINI-S/IGRINS
Kp–Vsys maps for CO, H2O, and OH when removing 5 SVD components from the data. The first three columns are obtained from the individual transits, while the right column shows the maps when combining the three observations. The white dotted lines mark the known (Kp ∼ 218 km/s, Vsys ∼ 38 km/s) values of WASP-121b (e.g., Borsa et al. 2021), with the black crosses indicating the location associated with the maximum SNR value in the shown domain. The SNR values were computed using the σ-clipping method (see text and Fig. 4), which produces slightly more conservative detections for CO and H2O. The SNR values for OH are not significant enough to claim a detection, but the maps are included here for reference. — astro-ph.EP

Ultra-hot Jupiters are among the best targets for atmospheric characterization at high spectral resolution. Resolving their transmission spectra as a function of orbital phase offers a unique window into the 3D nature of these objects.

In this work, we present three transits of the ultra-hot Jupiter WASP-121b observed with Gemini-S/IGRINS. For the first time, we measure the phase-dependent absorption signals of CO and H2O in the atmosphere of an exoplanet, and we find that they are different. While the blueshift of CO increases during the transit, the absorption lines of H2O become less blueshifted with phase, and even show a redshift in the second half of the transit.

These measurements reveal the distinct spatial distributions of both molecules across the atmospheres of ultra-hot Jupiters. Also, we find that the H2O signal is absent in the first quarter of the transit, potentially hinting at cloud formation on the evening terminator of WASP-121b.

To further interpret the absorption trails of CO and H2O, as well as the Doppler shifts of Fe previously measured with VLT/ESPRESSO, we compare the data to simulated transits of WASP-121b. To this end, we post-processes the outputs of global circulation models with a 3D Monte-Carlo radiative transfer code.

Our analysis shows that the atmosphere of WASP-121b is subject to atmospheric drag, as previously suggested by small hotspot offsets inferred from phase-curve observations. Our study highlights the importance of phase-resolved spectroscopy in unravelling the complex atmospheric structure of ultra-hot Jupiters and sets the stage for further investigations into their chemistry and dynamics.

Joost P. Wardenier, Vivien Parmentier, Michael R. Line, Megan Weiner Mansfield, Xianyu Tan, Shang-Min Tsai, Jacob L. Bean, Jayne L. Birkby, Matteo Brogi, Jean-Michel Désert, Siddharth Gandhi, Elspeth K. H. Lee, Colette I. Levens, Lorenzo Pino, Peter C. B. Smith

Comments: 24 pages, 16 figures, resubmitted to PASP
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2406.09641 [astro-ph.EP] (or arXiv:2406.09641v1 [astro-ph.EP] for this version)
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Submission history
From: Joost Wardenier
[v1] Fri, 14 Jun 2024 00:16:20 UTC (4,293 KB)

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