Issue |
A&A
Volume 689, September 2024
|
|
---|---|---|
Article Number | A8 | |
Number of page(s) | 15 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202449935 | |
Published online | 05 September 2024 |
ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b★
1
Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP,
Rua das Estrelas,
4150-762
Porto, Portugal
e-mail: ana.rita@astro.up.pt
2
Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto,
Rua do Campo Alegre,
4169-007
Porto, Portugal
3
Observatoire Astronomique de l’Université de Genève,
Chemin Pegasi 51,
1290
Versoix, Switzerland
4
Centre Vie dans l’Univers, Faculté des sciences, Université de Genève,
Genève 4, Switzerland
5
INAF − Osservatorio Astronomico di Trieste,
via G. B. Tiepolo 11,
34143
Trieste, Italy
6
Instituto de Astrofísica de Canarias,
c/ Vía Láctea s/n,
38205
La Laguna, Tenerife, Spain
7
Departamento de Astrofísica, Universidad de La Laguna,
38206
La Laguna, Tenerife, Spain
8
Consejo Superior de Investigaciones Cientícas,
Spain
9
Centro de Astrobiología, CSIC-INTA,
Camino Bajo del Castillo s/n,
28692
Villanueva de la Cañada, Madrid
10
Physics Institute, University of Bern,
Sidlerstrasse 5,
3012
Bern, Switzerland
11
Département de Physique, Institut Trottier de Recherche sur les Exoplanètes, Université de Montréal,
Montréal, Québec,
H3T 1J4, Canada
12
INAF − Osservatorio Astronomico di Brera,
Via E. Bianchi 46,
23807
Merate (LC), Italy
13
Centro de Astrobiología, CSIC-INTA,
Crta. Ajalvir km 4,
28850
Torrejón de Ardoz, Madrid, Spain
14
European Southern Observatory,
Alonso de Córdova 3107,
Vitacura, Región Metropolitana, Chile
15
Centro de Astrofísica da Universidade do Porto,
Rua das Estrelas,
4150-762
Porto, Portugal
16
Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências da Universidade de Lisboa,
Campo Grande,
PT1749-016
Lisboa, Portugal
17
INAF − Osservatorio Astrofisico di Torino,
Via Osservatorio 20,
10025
Pino Torinese, Italy
Received:
11
March
2024
Accepted:
9
July
2024
Context. Ultra hot Jupiters (gas giants with Teq > 2000 K) are intriguing exoplanets due to the extreme physics and chemistry present in their atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy.
Aims. We search for signatures of neutral and singly ionised iron (Fe I and Fe II, respectively) in the dayside of the ultra hot Jupiter WASP-76 b, as these species were detected via transmission spectroscopy in this exoplanet. Furthermore, we aim to confirm the existence of a thermal inversion layer, which has been reported in previous studies, and attempt to constrain its properties.
Methods. We observed WASP-76 b on four epochs with ESPRESSO at the VLT, at orbital phases shortly before and after the secondary transit, when the dayside is in view. We present the first analysis of high-resolution optical emission spectra for this exoplanet. We compare the data to synthetic templates created with petitRADTRANS, using cross-correlation function techniques.
Results. We detect a blueshifted (−4.7 ± 0.3 km s−1) Fe I emission signature on the dayside of WASP-76 b at 6.0σ. The signal is detected independently both before and after the eclipse, and it is blueshifted in both cases. The presence of iron emission features confirms the existence of a thermal inversion layer. Fe II was not detected, possibly because this species is located in the upper layers of the atmosphere, which are more optically thin. Thus the Fe II signature on the dayside of WASP-76 b is too weak to be detected with emission spectroscopy.
Conclusions. We propose that the blueshifted Fe I signature is created by material rising from the hot spot to the upper layers of the atmosphere, and discuss possible scenarios related to the position of the hotspot. This work unveils some of the dynamic processes ongoing on the dayside of the ultra hot Jupiter WASP-76 b through the analysis of the Fe I signature from its atmosphere, and complements previous knowledge obtained from transmission studies. It also highlights the ability of ESPRESSO to probe the dayside of this class of exoplanets.
Key words: methods: observational / techniques: spectroscopic / planets and satellites: atmospheres / planets and satellites: gaseous planets / planets and satellites: individual: WASP-76b
© The Authors 2024
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.
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