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(2022) The GAPS Programme at TNG. Astronomy & Astrophysics, 668 . A176. doi:10.1051/0004-6361/202244593 ISSN 0004-6361.
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WRAP-the-GAPS-Programme-TNG-Brogi-2022.pdf - Published Version - Requires a PDF viewer. Available under License Creative Commons Attribution 4.0. Download (2993Kb) | Preview |
Official URL: http://dx.doi.org/10.1051/0004-6361/202244593
Abstract
Aims. We present a novel method for studying the thermal emission of exoplanets as a function of orbital phase at very high spectral resolution, and use it to investigate the climate of the ultra-hot Jupiter KELT-9b.
Methods. We combine three nights of HARPS-N and two nights of CARMENES optical spectra, covering orbital phases between quadratures (0.25 < φ < 0.75), when the planet shows its day-side hemisphere with different geometries. We co-add the signal of thousands of Fe I lines through cross-correlation, which we map to a likelihood function. We investigate the phase-dependence of two separate observable quantities, namely (i) the line depths of Fe I and (ii) their Doppler shifts, introducing a new method that exploits the very high spectral resolution of our observations.
Results. We confirm a previous detection of Fe I emission, and demonstrate a precision of 0.5 km s−1 on the orbital properties of KELT-9b when combining all nights of observations. By studying the phase-resolved Doppler shift of Fe I lines, we detect an anomaly in the planet's orbital radial velocity well-fitted with a slightly eccentric orbital solution (e = 0.016 ± 0.003, ω = 150−11+13°, 5σ preference). However, we argue that this anomaly is caused by atmospheric circulation patterns, and can be explained if neutral iron gas is advected by day-to-night atmospheric wind flows of the order of a few km s−1. We additionally show that the Fe I emission line depths are symmetric around the substellar point within 10° (2σ), possibly indicating the lack of a large hot-spot offset at the altitude probed by neutral iron emission lines. Finally, we do not obtain a significant preference for models with a strong phase-dependence of the Fe I emission line strength. We show that these results are qualitatively compatible with predictions from general circulation models (GCMs) for ultra-hot Jupiter planets.
Conclusions. Very high-resolution spectroscopy phase curves are of sufficient sensitivity to reveal a phase dependence in both the line depths and their Doppler shifts throughout the orbit. They constitute an under-exploited treasure trove of information that is highly complementary to space-based phase curves obtained with HST and JWST, and open a new window onto the still poorly understood climate and atmospheric structure of the hottest planets known to date.
| Item Type: | Journal Article | ||||||||||||
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| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
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| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||
| Library of Congress Subject Headings (LCSH): | Extrasolar planets -- Atmopsheres, Planets, Astrophysics | ||||||||||||
| Journal or Publication Title: | Astronomy & Astrophysics | ||||||||||||
| Publisher: | EDP Sciences | ||||||||||||
| ISSN: | 0004-6361 | ||||||||||||
| Official Date: | 2022 | ||||||||||||
| Dates: |
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| Volume: | 668 | ||||||||||||
| Article Number: | A176 | ||||||||||||
| DOI: | 10.1051/0004-6361/202244593 | ||||||||||||
| Status: | Peer Reviewed | ||||||||||||
| Publication Status: | Published | ||||||||||||
| Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||
| Date of first compliant deposit: | 2 February 2023 | ||||||||||||
| Date of first compliant Open Access: | 2 February 2023 | ||||||||||||
| RIOXX Funder/Project Grant: |
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