Issue |
A&A
Volume 693, January 2025
|
|
---|---|---|
Article Number | A316 | |
Number of page(s) | 20 | |
Section | Planets, planetary systems, and small bodies | |
DOI | https://doi.org/10.1051/0004-6361/202451937 | |
Published online | 29 January 2025 |
The GAPS programme at TNG
LXVI. A homogeneous search for Na I and its possible variability in ten gas giant exoplanets★
1
INAF – Osservatorio Astrofisico di Catania,
Via S. Sofia 78,
95123
Catania,
Italy
2
Dipartimento di Fisica e Astronomia “Galileo Galilei” – Università degli Studi di Padova,
Vicolo dell’Osservatorio 3,
35122
Padova,
Italy
3
INAF – Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
Padova
35122,
Italy
4
Space Research Institute, Austrian Academy of Sciences,
Schmiedl- strasse 6,
8042
Graz,
Austria
5
INAF – Osservatorio Astrofisico di Torino,
Via Osservatorio 20,
10025
Pino Torinese,
Italy
6
INAF – Osservatorio Astronomico di Brera,
Via E. Bianchi 46,
23807
Merate,
Italy
7
INAF – Osservatorio Astrofisico di Arcetri,
Largo E. Fermi 5,
50125
Firenze,
Italy
8
DISAT, Università degli Studi dell’Insubria,
via Valleggio 11,
22100
Como,
Italy
9
University of Palermo, Department of Physics and Chemistry “Emilio Segrè”,
Via Archirafi 36,
Palermo,
Italy
10
INAF – Osservatorio Astronomico di Palermo,
Piazza del Parlamento, 1,
90134
Palermo,
Italy
11
Fundación Galileo Galilei-INAF,
Rambla José Ana Fernandez Pérez 7,
38712
Breña Baja,
TF,
Spain
★★ Corresponding author; daniela.sicilia@inaf.it
Received:
20
August
2024
Accepted:
26
November
2024
The neutral sodium resonance doublet (Na I D) has been detected in the upper atmosphere of several close-in gas giants, through high-resolution transmission spectroscopy. We aim to investigate whether its variability is linked to the planets’ properties, the data quality, or the accuracy of the system parameters used. Using the public code SLOPpy, we extracted the transmission spectrum in the Na I D region of ten gas giants for which a large number of HARPS-N observations are available. We modelled the absorption signals found, performing an MCMC analysis, and converted the measured absorption depth to the corresponding atmospheric height over which most sodium absorption occurs. While two targets (GJ 436 b and KELT-7 b) show no Na I D feature, we found variability in the transmission spectrum of the other targets. Three of them (HD 209458 b, WASP-80 b, and WASP-127 b) present absorption on only some nights, while in the other five targets (HD 189733 b, KELT-9 b, KELT-20 b, WASP-69 b, and WASP-76 b), a significant absorption signal is present on most of the nights analysed. Except for WASP-69 b, the measured absorption depths lead to a ratio of the two Na I D depths that is compatible with or slightly larger than one. As was expected from literature, the relative atmospheric height follows an empirical exponential trend as a function of a scaled product of the planet’s equilibrium temperature and surface gravity. We confirm the sodium detection on HD 189733 b, KELT-9 b, KELT-20 b, WASP-69 b, and WASP-76 b. The signal detected in WASP- 127 b requires further observations for definitive confirmation. We exclude a planetary origin for the signals found on HD 209458 b and WASP-80 b. The sodium absorption variability does not appear to be related to planetary properties, but rather to data quality, sub-optimal data treatment, or stellar activity.
Key words: techniques: spectroscopic / planets and satellites: atmospheres
Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei (FGG) of the Istituto Nazionale di Astrofisica (INAF) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.