Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode

Transit spectroscopy usually relies on the integration of one or several transits to achieve the signal-to-noise ratio (S/N) necessary to resolve spectral features. Consequently, high-S/N observations of exoplanet atmospheres, where we can forgo integration, are essential for disentangling the complex chemistry and dynamics beyond global trends. In this study, we combined two partial 4-UT transits of the ultrahot Jupiter WASP-121 b, observed with the ESPRESSO at the European Southern Observatory’s Very Large Telescope in order to revisit its titanium chemistry. Through cross-correlation analysis, we achieved detections of H I , Li I , Na I , K I , Mg I , Ca I , Ti I , V I , Cr I , Mn I , Fe I , Fe II , Co I , Ni I , Ba II , Sr I , and Sr II . Additionally, narrow-band spectroscopy allowed us to resolve strong single lines, resulting in significant detections of H α , H β , H γ , Li I , Na I , K I , Mg I , Ca II , Sr I , Sr II , and Mn I . Our most notable finding is the high-significance detection of Ti I (∼5 σ per spectrum, and ∼19 σ stacked in the planetary rest frame). Comparison with atmospheric models reveals that Ti I is indeed depleted compared to V I . We also resolve the planetary velocity traces of both Ti I and V I , with Ti I exhibiting a significant blueshift toward the end of the transit. This suggests that Ti I primarily originates from low-latitude regions within the super-rotating jet observed in WASP-121 b. Our observations suggest limited mixing between the equatorial jet and the mid-latitudes, in contrast with model predictions from General Circulation Models. We also report the non-detection of TiO, which we attribute to inaccuracies in the line list that could hinder its detection, even if present. Thus, the final determination of the presence of TiO must await space-based observations. We conclude that the 4-UT mode of ESPRESSO is an excellent testbed for achieving high S/N on relatively faint targets, paving the way for future observations with the Extremely Large Telescope.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-02-01
DOI
https://doi.org/10.1051/0004-6361/202452405
Citations
9
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
10.39

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article

Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode

J. V. Seidel, H. J. Hoeijmakers, Lorenzo Pino, M. Steiner et al.
9 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
10.39
article

Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode

J. V. Seidel, H. J. Hoeijmakers, Lorenzo Pino, M. Steiner, Brett M. Morris, M. R. Zapatero Osorio, N. W. Borsato, Bibiana Prinoth, A. Suárez Mascareño, Romain Allart, F. Borsa, Elyar Sedaghati, D. Kitzmann, M. Baratella, N. C. Santos, H. M. Tabernero, Vivien Parmentier, Y. C. Damasceno
article en
9 citations

Abstract

Transit spectroscopy usually relies on the integration of one or several transits to achieve the signal-to-noise ratio (S/N) necessary to resolve spectral features. Consequently, high-S/N observations of exoplanet atmospheres, where we can forgo integration, are essential for disentangling the complex chemistry and dynamics beyond global trends. In this study, we combined two partial 4-UT transits of the ultrahot Jupiter WASP-121 b, observed with the ESPRESSO at the European Southern Observatory’s Very Large Telescope in order to revisit its titanium chemistry. Through cross-correlation analysis, we achieved detections of H I , Li I , Na I , K I , Mg I , Ca I , Ti I , V I , Cr I , Mn I , Fe I , Fe II , Co I , Ni I , Ba II , Sr I , and Sr II . Additionally, narrow-band spectroscopy allowed us to resolve strong single lines, resulting in significant detections of H α , H β , H γ , Li I , Na I , K I , Mg I , Ca II , Sr I , Sr II , and Mn I . Our most notable finding is the high-significance detection of Ti I (∼5 σ per spectrum, and ∼19 σ stacked in the planetary rest frame). Comparison with atmospheric models reveals that Ti I is indeed depleted compared to V I . We also resolve the planetary velocity traces of both Ti I and V I , with Ti I exhibiting a significant blueshift toward the end of the transit. This suggests that Ti I primarily originates from low-latitude regions within the super-rotating jet observed in WASP-121 b. Our observations suggest limited mixing between the equatorial jet and the mid-latitudes, in contrast with model predictions from General Circulation Models. We also report the non-detection of TiO, which we attribute to inaccuracies in the line list that could hinder its detection, even if present. Thus, the final determination of the presence of TiO must await space-based observations. We conclude that the 4-UT mode of ESPRESSO is an excellent testbed for achieving high S/N on relatively faint targets, paving the way for future observations with the Extremely Large Telescope.

Astronomy and AstrophysicsVol. 694
University of Geneva (CH), University of Bern (CH), Universidad Complutense de Madrid (ES), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), Universidad de La Laguna (ES), Universidade do Porto (PT), Lund University (SE), Université Côte d'Azur (FR), Arcetri Astrophysical Observatory (IT), Brera Astronomical Observatory (IT), Institute of Astrophysics and Space Sciences (PT), Observatoire de la Côte d’Azur (FR), Centro de Astrobiología (ES), European Southern Observatory (CL), Instituto de Astrofísica de Canarias (ES), Université de Montréal (CA), International Space Science Institute (CH), Macquarie University (AU)
National Science Foundation, Comunidad de Madrid, European Commission, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Ministerio de Ciencia e Innovación, European Research Council, Fundação para a Ciência e a Tecnologia
Life below water
Openalex Percentile: Top 2%
Stellar, planetary, and galactic studies
10.39
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