ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b

Context. Ultra hot Jupiters (gas giants with T eq > 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 6.0 σ . 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.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-09-01
DOI
https://doi.org/10.1051/0004-6361/202449935
Citations
8
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
2.65

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article

ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b

N. J. Nunes, Ana Rita Costa Silva, J. V. Seidel, Y. Alibert et al.
8 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
2.65
article

ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b

N. J. Nunes, Ana Rita Costa Silva, J. V. Seidel, Y. Alibert, M. Lendl, M. Steiner, A. Mehner, P. Figueira, M. R. Zapatero Osorio, S. Cristiani, C. J. A. P. Martins, V. Adibekyan, A. Suárez Mascareño, Romain Allart, Alessandro Sozzetti, F. Borsa, P. Di Marcantonio, E. Palle, F. Pepe, C. Lovis, D. Ehrenreich, Stefan Pelletier, N. C. Santos, R. Rébolo, J. I. Gónzalez Hernández, A. M. Silva, T. Azevedo Silva, V. Bourrier, E. Esparza-Borges, G. Lo Curto, E. Cristo, S. Udry, E. Herrero-Cisneros, S. G. Sousa, H. Chakraborty, Carlos Allende Prieto, O. D. S. Demangeon
article en
8 citations

Abstract

Context. Ultra hot Jupiters (gas giants with T eq > 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 6.0 σ . 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.

Astronomy and AstrophysicsVol. 689
University of Geneva (CH), University of Bern (CH), University of Lisbon (PT), Universidad de La Laguna (ES), Universidade do Porto (PT), Trieste Astronomical Observatory (IT), Brera Astronomical Observatory (IT), HES-SO Genève (CH), Institute of Astrophysics and Space Sciences (PT), Osservatorio Astrofisico di Torino (IT), Centro de Astrofísica da Universidade do Porto (PT), Centro de Astrobiología (ES), European Southern Observatory (CL), Instituto de Astrofísica de Canarias (ES), Université de Montréal (CA)
National Science Foundation, European Commission, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Ministero dell’Istruzione, dell’Università e della Ricerca, Ministerio de Ciencia e Innovación, European Research Council, Fundação para a Ciência e a Tecnologia, Fonds de recherche du Québec – Nature et technologies, European Regional Development Fund, Agencia Estatal de Investigación
Life below water
Openalex Percentile: Top 11%
Stellar, planetary, and galactic studies
2.65
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