Exoplanetology: Exoplanets & Exomoons

A Closer Look at LTT 9779b: The ESPRESSO Endeavour to Pierce the Atmospheric Veil

By Keith Cowing

Status Report

February 3, 2025

Filed under astro-ph.EP, atmosphere, CHEOPS, ESPRESSO, exoplanet, JWST, LTT9779 b, Spitzer, TESS

A Closer Look at LTT 9779b: The ESPRESSO Endeavour to Pierce the Atmospheric Veil — Top: Transmission Spectroscopy showing extra absorption in the Na doublet’s core lines across different global abundances, measured in PPM. This plot compares three injected models, illustrating the presence or absence of TiO and VO. It features one example with error bars plus a main strand after several runs. In light blue, regions below 200 ppm are highlighted, indicating areas under the estimated error threshold coming from models without signals. Bottom: Three examples of Transmission Spectroscopy in PPM are presented. Black points represent data binned by a factor of 100, the light blue area denotes a 95% confidence interval, magenta highlights the core lines, and red dashed lines indicate the standard deviation of the continuum. Below these plots are normalised flux profiles centred on the core lines, with a dashed blue line marking the Na doublets. — astro-ph.EP

The proliferation of exoplanet discoveries in exotic environments like the Neptune desert challenges our understanding of planetary atmospheres under intense irradiation. The unexpected discovery of LTT9779 b, an ultra-hot Neptune within this desert, offers a prime opportunity for atmospheric studies.

We build on prior observations of LTT9779 b from TESS, Spitzer, and CHEOPS, incorporating new VLT/ESPRESSO data to probe its atmospheric dynamics. Preliminary analyses suggest a metal-rich atmosphere and a high day-side geometric albedo, possibly indicating silicate clouds. Minimal atmospheric escape is observed, contrasting existing models of planetary evolution under extreme irradiation.

We obtained the transmission spectrum of LTT9779 b between 0.4 and 0.78 microns with ESPRESSO, addressing systematics across three transits. Our analysis focused on the sodium doublet and H-alpha, using cross-correlation with models containing Na, K, FeH, TiO, and VO. No significant atmospheric signal was detected, with metallicity limits set at [Fe/H] >= 2.25 (>= 180 times solar).

The non-detection aligns with a high-metallicity, cloud-free model, implying a high mean molecular weight and reduced atmospheric scale height. We interpret this as evidence for a metal-rich atmosphere with suppressed spectral features, possibly due to high-altitude clouds or hazes. These findings are consistent with JWST observations, supporting the hypothesis of metal-rich atmospheres obscured by aerosols in extreme environments.

R. Ramírez Reyes, James S. Jenkins, Elyar Sedaghati, J. V. Seidel, Yakiv Pavlenko, E. Palle, Mercedes López-Morales, Douglas Alves, José Vines, Pablo A. Peña R, Matías R. Díaz, Patricio Rojo

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2501.17272 [astro-ph.EP] (or arXiv:2501.17272v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2501.17272
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Submission history
From: Ricardo Ramirez Reyes
[v1] Tue, 28 Jan 2025 20:05:19 UTC (7,955 KB)
https://arxiv.org/abs/2501.17272
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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