The ESPRESSO transmission spectrum of HD189733 b

Article Article scientifique Article The ESPRESSO transmission spectrum of HD189733 b eng 2025-08-01 2025-08 author Mounzer Dany 0000-0002-8070-2058 807263 author Dethier W. 0009-0007-3622-0928 author Lovis Cédric 511748 author Bourrier Vincent 828250 Département d'astronomie (ASTRO) author Psaridi Angeliki 0000-0002-4797-2419 942153 author Allart Romain 0000-0002-1199-9759 751868 author Chakraborty Hritam 0000-0002-5177-1898 973565 Département d'astronomie (ASTRO) author Lendl Monika 0000-0001-9699-1459 715612 Département d'astronomie (ASTRO) author Seidel Julia Victoria 0000-0002-7990-9596 873327 author Zapatero Osorio M. R. author Molaro P. 0000-0002-0571-4163 author Steiner Michal 0000-0003-3036-3585 920126 author Ehrenreich David 789146 Département d'astronomie (ASTRO) author Alibert Y. author Carleo I. 0000-0002-0810-3747 author Cristiani S. 0000-0002-2115-5234 author González Hernández J. I. 0000-0002-0264-7356 author Martins C. J. A. P. 0000-0002-4886-9261 author Palle E. 0000-0003-0987-1593 author Rodrigues J. 0000-0001-5164-3602 author Santos N. 0000-0003-4422-2919 author Sozzetti A. 0000-0002-7504-365X author Suárez Mascareño A. 0000-0002-3814-5323 A41 10.1051/0004-6361/202554785 0004-6361 https://www.aanda.org/10.1051/0004-6361/202554785 Context . While transmission spectroscopy has allowed us to detect many atomic and molecular species in exoplanet atmospheres, the improvement in resolution and signal-to-noise ratio (S/N) enabled us to become sensitive to planet-occulted line distortions (POLDs) in the spectrum that are induced by center-to-limb variations (CLV) and the Rossiter-McLaughlin effect (RM). POLDs can bias the interpretation of the transmission spectrum, and it is hard to correct for them with stellar models. Aims . We analyzed two ESPRESSO transits ( R ~ 140 000) of the archetypal hot Jupiter HD 189733 b. The transmission spectrum of this aligned system is heavily affected by POLDs, stellar activity, and instrumental effects. It is therefore a challenging study case of how to account for these effects when the planetary signal is retrieved from chemical species through transmission spectroscopy. Methods . We used the ANTARESS workflow to process the datasets to ensure an accurate correction for telluric and instrumental contamination. With improved architectural parameters derived using the RM revolutions technique, we tested several methods of including and correcting the strong POLDs in the transmission spectrum. We then derived the absorption spectrum from sodium through simultaneous forward-modeling of the star and planet using the code called evaporating exoplanets (EvE). Results . We confirm the previous detections of the sodium doublet signature in the upper atmosphere of HD 189733 b. When we accounted for POLDs and isolated the planetary signal from uncorrected stellar residuals, we found a shallower (0.432 ± 0.027%) and more strongly blueshifted (−7.97 ± 0.28 km s −1 ) signal. We attempted to reinterpret the other high-resolution sodium studies of this system in light of our results. We suggest that the POLDs and stellar activity are insufficiently corrected for in all analyses, including ours. We also detected a planetary lithium signature of 0.102 ± 0.016% (6.4σ) at a blueshift of -2.4 ± 1.8 km s −1 . Conclusions . We have probably reached limitations in the accuracy of theoretical stellar spectra and in our understanding of stellar variability at the timescale of a transit because we are unable to fully correct for the effect of POLDs in HD 189733 b transmission spectra. As we shift toward a new generation of ground-based spectrographs on the ELT with an even higher S/N and resolution, addressing these issues will be paramount for a proper characterization of exoplanet atmospheres with transit spectroscopy. Dewey 520 Swiss National Science Foundation NCCR PlanetS: Origin, evolution and characterisation of planets (phase II) 182901 CH Swiss National Science Foundation NCCR PlanetS: Origin, evolution and characterisation of planets (phase III) 205606 CH European Commission Future of upper atmospheric characterisation of exoplanets with spectroscopy 724427 FOUR ACES EU H2020 Unidad de Excelencia María de Maeztu CEX2020-001058-M Swiss National Science Foundation Probing Exoplanet Atmospheres: Harnessing the Synergy of JWST and High-Resolution Spectrographs 222212 CH Swiss National Science Foundation Spectroscopy of hot twilights in exoplanetary atmospheres 200726 CH European Commission FInding ExoeaRths: tackling the ChallengEs of stellar activity 101052347 FIERCE EU HE 26 Département d'astronomie 12 false Astronomy & astrophysics 700 bf220b7c-6291-4ef2-a5dd-641fe72efdf1 Article (Published version) Public Article_scientifique_from_crossref.pdf 9251919 application/pdf CC BY-4.0 0619a40d35e31acfda667fb4435ad6b1582c57d4d0f79f320c78a6a4e359e377 openAccess Faculté des sciences / Département d'astronomie

Title	Published in	Year	Views	Downloads

Exploration of Exoplanetary Atmospheres Through High-Resolution Transmission Spectroscopy		2025	105	77
The ESPRESSO transmission spectrum of HD189733 b	Astronomy & astrophysics	2025	12	414

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