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Spatially-resolving the terminator : variation of Fe, temperature and winds in WASP-76 b across planetary limbs and orbital phase
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Gandhi, Siddharth, Kesseli, Aurora, Snellen, Ignas, Brogi, Matteo, Wardenier, Joost P., Parmentier, Vivien, Welbanks, Luis and Savel, Arjun B. (2022) Spatially-resolving the terminator : variation of Fe, temperature and winds in WASP-76 b across planetary limbs and orbital phase. Monthly Notices of the Royal Astronomical Society, 515 (1). pp. 749-766. doi:10.1093/mnras/stac1744 ISSN 1365-2966.
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Official URL: https://doi.org/10.1093/mnras/stac1744
Abstract
Exoplanet atmospheres are inherently three-dimensional systems in which thermal/chemical variation and winds can strongly influence spectra. Recently, the ultra-hot Jupiter WASP-76 b has shown evidence for condensation and asymmetric Fe absorption with time. However, it is currently unclear whether these asymmetries are driven by chemical or thermal differences between the two limbs, as precise constraints on variation in these have remained elusive due to the challenges of modelling these dynamics in a Bayesian framework. To address this we develop a new model, HyDRA-2D, capable of simultaneously retrieving morning and evening terminators with day-night winds. We explore variations in Fe, temperature profile, winds and opacity deck with limb and orbital phase using VLT/ESPRESSO observations of WASP-76 b. We find Fe is more prominent on the evening for the last quarter of the transit, with $\log (X_\mathrm{Fe}) = {-4.03}^{+0.28}_{-0.31}$, but the morning shows a lower abundance with a wider uncertainty, $\log (X_\mathrm{Fe}) = {-4.59}^{+0.85}_{-1.0}$, driven by degeneracy with the opacity deck and the stronger evening signal. We constrain 0.1 mbar temperatures ranging from $2950^{+111}_{-156}$ K to $2615^{+266}_{-275}$ K, with a trend of higher temperatures for the more irradiated atmospheric regions. We also constrain a day-night wind speed of $9.8^{+1.2}_{-1.1}$ km/s for the last quarter, higher than $5.9^{+1.5}_{-1.1}$ km/s for the first, in line with general circulation models. We find our new spatially- and phase-resolved treatment is statistically favoured by 4.9σ over traditional 1D-retrievals, and thus demonstrate the power of such modelling for robust constraints with current and future facilities.
| Item Type: | Journal Article | ||||||||
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| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
| SWORD Depositor: | Library Publications Router | ||||||||
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||
| Publisher: | Oxford University Press (OUP) | ||||||||
| ISSN: | 1365-2966 | ||||||||
| Official Date: | September 2022 | ||||||||
| Dates: |
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| Volume: | 515 | ||||||||
| Number: | 1 | ||||||||
| Page Range: | pp. 749-766 | ||||||||
| DOI: | 10.1093/mnras/stac1744 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Reuse Statement (publisher, data, author rights): | ** Article version: AM ** From Crossref journal articles via Jisc Publications Router ** History: epub 23-06-2022; issued 23-06-2022. ** Licence for AM version of this article starting on 23-06-2022: https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model | ||||||||
| Access rights to Published version: | Open Access (Creative Commons) | ||||||||
| Date of first compliant deposit: | 23 August 2022 | ||||||||
| Date of first compliant Open Access: | 23 August 2022 | ||||||||
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