A closer look at LTT 9779b: The ESPRESSO endeavour to pierce the atmospheric veil

Abstract

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] $\ge$ 2.25 ($\ge$ 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.

arXiv comment12 pages, 11 figures, 3 tables, Accepted for publication in Astronomy and Astrophysics

References in corpus (45)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The Spitzer Space Telescope Mission
• Fast and scalable Gaussian process modeling with applications to astronomical time series
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Automated data reduction workflows for astronomy
• Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments
• petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
• On the radiative equilibrium of irradiated planetary atmospheres
• ESPRESSO@VLT -- On-sky performance and first results
• Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
• Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres
• 3D mixing in hot Jupiter atmospheres. I. application to the day/night cold trap in HD 209458b
• A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b
• Spectrally resolved detection of sodium in the atmosphere of HD189733b with the HARPS spectrograph
• A Framework for Characterizing the Atmospheres of Low-Mass Low-Density Transiting Planets
• The CHEOPS mission
• A diagram for the evaporation status of extrasolar planets
• Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b
• Photoevaporation and High-Eccentricity Migration Created the Sub-Jovian Desert
• A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
• A short-period censor of sub-Jupiter mass exoplanets with low density
• Atmospheric circulation of tidally locked exoplanets: a suite of benchmark tests for dynamical solvers
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
• Emerging Trends in a Period-Radius Distribution of Close-in Planets
• POLLUX : a database of synthetic stellar spectra
• Connecting Giant Planet Atmosphere and Interior Modeling: Constraints on Atmospheric Metal Enrichment
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) I. Detection of hot neutral sodium at high altitudes on WASP-49b
• Detection of neutral atomic species in the ultra-hot jupiter WASP-121b
• Na I and H$\alpha$ absorption features in the atmosphere of MASCARA-2b/KELT-20b
• Atmospheric Circulation of Brown Dwarfs and Jupiter and Saturn-like Planets: Zonal Jets, Long-term Variability, and QBO-type Oscillations
• An Ultra-Hot Neptune in the Neptune desert
• The effect of the stellar absorption line centre-to-limb variation on exoplanet transmission spectrum observations
• The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation
• The atmosphere of HD 209458b seen with ESPRESSO. No detectable planetary absorptions at high resolution
• WASP-127b: A misaligned planet with a partly cloudy atmosphere and tenuous sodium signature seen by ESPRESSO
• RASSINE: Interactive tool for normalising stellar spectra I. Description and performance of the code
• Survival of a planet in short-period Neptunian desert under effect of photo-evaporation
• A New Model of Roche-lobe Overflow for Short-Period Gaseous Planets and Binary Stars
• Phase Curves of Hot Neptune LTT 9779b Suggest a High-Metallicity Atmosphere
• Is the atmosphere of the ultra-hot Jupiter WASP-121b variable?
• Spitzer Reveals Evidence of Molecular Absorption in the Atmosphere of the Hot Neptune LTT 9979b
• Assessing telluric correction methods for Na detections with high-resolution exoplanet transmission spectroscopy
• The Hot Neptune WASP-166 b with ESPRESSO II: Confirmation of atmospheric sodium

Cited by in corpus (4)

• A High Geometric Albedo for LTT9779b Points Towards a Metal-rich Atmosphere and Silicate Clouds
• No TiO detected in the hot Neptune-desert planet LTT-9779 b in reflected light at high spectral resolution
• HST/WFC3 Constraints on the Abundances of OH and FeH in the Atmosphere of the Ultra-Hot Neptune LTT-9779 b
• TOI-333b: A Neptune Desert planet around a F7V star