arXiv subjects

Adrien Simonnin

Publications and source records attributed to Adrien Simonnin.

3 recordsLinked to original sources

arXiv2026

Magnetic field strengths of hot giant exoplanets consistent with Solar System values

Magnetic fields are ubiquitous in the universe. They play a key role in shaping the activity of stars, the habitability of rocky planets, and the long-term retention of planetary atmospheres. Theoretical scaling laws are largely constrained by the limited set of stars and Solar System planets, leading to a wide range of possible values for hot giant planets outside of the Solar System from fractions of the Jovian field to orders of magnitude larger. Ultra-hot Jupiters, with their highly ionised atmospheres, provide a new avenue to probe magnetic effects, as their atmospheric circulation could be directly sensitive to atmospheric magnetic field strength. Using high-spectral resolution observations targeting the iron lines of ultra-hot Jupiters we measure the Doppler shift and thus the wind speed of seven transiting ultra-hot Jupiters. We find a clear decrease of wind speed with increasing planetary temperature, a trend inconsistent with purely hydrodynamic mechanisms but naturally reproduced by magnetic drag. From this relation we estimate the possible strength of magnetic fields of hot giant planets to at most a few gauss - comparable to the Jovian equatorial field. Our results support the idea that magnetic fields affect the atmospheric circulation of ultra-hot Jupiters and could provide a crucial benchmark for scaling laws used to predict magnetic fields in exoplanets, from hot Jupiters to rocky Earths with additional implications for future direct observations.

astro-ph.EP↗

arXiv2026

A population view of transiting hot giant exoplanets: Tracing Fe and Ti chemistry with ESPRESSO and MAROON-X

Hot and ultra-hot Jupiters offer a unique laboratory to study atmospheric chemistry at the population level using ground-based high-resolution spectroscopy. Fe and Ti are key tracers of thermal and chemical structure, yet they exhibit different observational trends across the population. We present a homogeneous reanalysis of high-resolution transmission spectra of ten hot and ultra-hot Jupiters observed with VLT/ESPRESSO and Gemini-N/MAROON-X. We search for neutral Fe and Ti absorption and perform injection-recovery tests using models spanning a range of Ti-depletion levels and T-p profiles. For direct comparison across observations, we introduce the relative cross-correlation metric, $\Delta$Ti-Fe. We detect Fe in 7 and Ti in 4 planets above 5$\sigma$. Across the population, $\Delta$Ti-Fe decreases sharply towards lower equilibrium temperatures. Under the assumption of equal Ti depletion across planets, isothermal models fail to reproduce this trend, instead requiring a temperature-dependent depletion of Ti that increases toward cooler planets, consistent with cold-trapping processes in cooler atmospheres. Models with inverted T-p profiles naturally reproduce the decline without invoking temperature-dependent depletion. There, Ti is converted into TiO in deeper, cooler layers and then removed from the gas phase through condensation, leading to strong suppression of the observable atomic Ti signal. Nevertheless, even in the gradient models, overall depletion of Ti relative to Fe is required to match the hottest planets. Our results demonstrate that observable refractory chemistry is governed by the interplay of molecular partitioning, ionisation, condensation, and cold-trapping processes, as well as the vertical structure of ultra-hot Jupiter atmospheres. Additional observations will be necessary to distinguish between temperature-dependent cold-trapping and overall depletion.(abbrev.)

astro-ph.EP↗

arXiv2023

Ground-breaking Exoplanet Science with the ANDES spectrograph at the ELT

In the past decade the study of exoplanet atmospheres at high-spectral resolution, via transmission/emission spectroscopy and cross-correlation techniques for atomic/molecular mapping, has become a powerful and consolidated methodology. The current limitation is the signal-to-noise ratio during a planetary transit. This limitation will be overcome by ANDES, an optical and near-infrared high-resolution spectrograph for the ELT. ANDES will be a powerful transformational instrument for exoplanet science. It will enable the study of giant planet atmospheres, allowing not only an exquisite determination of atmospheric composition, but also the study of isotopic compositions, dynamics and weather patterns, mapping the planetary atmospheres and probing atmospheric formation and evolution models. The unprecedented angular resolution of ANDES, will also allow us to explore the initial conditions in which planets form in proto-planetary disks. The main science case of ANDES, however, is the study of small, rocky exoplanet atmospheres, including the potential for biomarker detections, and the ability to reach this science case is driving its instrumental design. Here we discuss our simulations and the observing strategies to achieve this specific science goal. Since ANDES will be operational at the same time as NASA's JWST and ESA's ARIEL missions, it will provide enormous synergies in the characterization of planetary atmospheres at high and low spectral resolution. Moreover, ANDES will be able to probe for the first time the atmospheres of several giant and small planets in reflected light. In particular, we show how ANDES will be able to unlock the reflected light atmospheric signal of a golden sample of nearby non-transiting habitable zone earth-sized planets within a few tenths of nights, a scientific objective that no other currently approved astronomical facility will be able to reach.

astro-ph.IM↗