Letter to the Editor

Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b^⋆

Together with new detections of Co and Sr+ on WASP-121b

¹ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
e-mail: Tomas.Silva@astro.up.pt; Olivier.Demangeon@astro.up.pt
² Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
³ Department of Physics, and Institute for Research on Exoplanets, Université de Montréal, Montréal H3T 1J4, Canada
⁴ Observatoire astronomique de l’Université de Genève, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁵ INAF – Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy
⁶ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
⁷ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁸ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Region Metropolitana, Chile
⁹ Instituto de Astrofísica de Canarias, C. Vía Lèctea, s/n 38205, Spain
¹⁰ Centro de Astrobiología (CSIC-INTA), Crta. Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
¹¹ INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
¹² Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
¹³ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
¹⁴ Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Miramare, Trieste, Italy
¹⁵ Centre Vie dans l’Univers, Faculté des sciences de l’Université de Genève, Quai Ernest-Ansermet 30, 1205 Geneva, Switzerland
¹⁶ Universidad de La Laguna (ULL), Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
¹⁷ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁸ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, Palermo, Italy
¹⁹ Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Miramare, Trieste, Italy
²⁰ Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal
²¹ Departamento de Física, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Edificio C8, 1749-016 Lisboa, Portugal
²² INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, TO, Italy

Received: 13 July 2022
Accepted: 6 September 2022

Abstract

Context. High-resolution spectroscopy studies of ultra-hot Jupiters have been key in our understanding of exoplanet atmospheres. Observing into the atmospheres of these giant planets allows for direct constraints on their atmospheric compositions and dynamics while laying the groundwork for new research regarding their formation and evolution environments.

Aims. Two of the most well-studied ultra-hot Jupiters are WASP-76b and WASP-121b, with multiple detected chemical species and strong signatures of their atmospheric dynamics. We take a new look at these two exceptional ultra-hot Jupiters by reanalyzing the transit observations taken with ESPRESSO at the Very Large Telescope and attempt to detect additional species.

Methods. To extract the planetary spectra of the two targets, we corrected for the telluric absorption and removed the stellar spectrum contributions. We then exploited new synthetic templates that were specifically designed for ultra-hot Jupiters in combination with the cross-correlation technique to unveil species that remained undetected by previous analyses.

Results. We add a novel detection of Ba+ to the known atmospheric compositions of WASP-76b and WASP-121b, the heaviest species detected to date in any exoplanetary atmosphere, with additional new detections of Co and Sr+ and a tentative detection of Ti+ for WASP-121b. We also confirm the presence of Ca+, Cr, Fe, H, Li, Mg, Mn, Na, and V on both WASP-76b and WASP-121b, with the addition of Ca, Fe+, and Ni for the latter. Finally, we also confirm the clear asymmetric absorption feature of Ca+ on WASP-121b, with an excess absorption at the bluer wavelengths and an effective planet radius beyond the Roche lobe. This indicates that the signal may arise from the escape of planetary atmosphere.