Contexte
The postdoctoral position will be based at LESIA, on the Paris Observatory premises in Meudon. The successful candidate will work with Benjamin Charnay and Bruno Bézard (LESIA), Jérémy Leconte (LAB, Bordeaux) as well as the ANR MIRAGE team (PI : Arthur Vigan) and the PhD students and post-docs of the LESIA exoplanet group. Applications are open to candidates of any nationality.
The successful candidate will benefit of full health insurance. In addition, financial support will be provided to cover research expenses.
Missions
The ANR MIRAGE (Multi-Resolution Analysis of Giant Exoplanets) project aims to characterise the atmospheres of young giant exoplanets using medium- and high-resolution spectroscopy and a combination of observations from different instruments, in particular Hirise, coupling SPHERE to CRIRES+ on VLT (https://www.cnrs.fr/fr/presse/premiere-lumiere-pour-hirise-nouvel-instrument-detude-des-exoplanetes). The goal is to constrain the planetary formation processes as well as the atmospheric processes (chemistry, clouds, atmospheric dynamics) that lead to the diversity of the exoplanets observed. To do this, the observations must lead to the measurement of atmospheric/planetary parameters (temperature, gravity, metallicity, C/O ratio, isotopologue ratios, etc.) using atmospheric inversion models. As part of the ANR MIRAGE project, we are proposing to develop an atmospheric inversion model based on the optimal estimation method (a method consisting of iteratively converging towards profiles of temperature, chemical composition and clouds), which is widely used to study the atmospheres in the solar system. In the case of exoplanets, inversion models are generally based on a Bayesian approach (MCMC and nested sampling), which allows a wide exploration of the parameter domain. Optimal estimation, however, is much more efficient, allowing more accurate derivation of vertical variations. It is ideally suited to high-quality observations of giant exoplanets and brown dwarfs, such as those from JWST and VLT-CRIRES+/Hirise.
Activités
The person recruited will adapt the exo_k library (https://perso.astrophy.u-bordeaux.fr/~jleconte/exo_k-doc/index.html) to retrievals by optimal estimation. Atmospheric opacities and initial states can be taken from the Exo-REM model and associated grids (https://gitlab.obspm.fr/Exoplanet-Atmospheres-LESIA/exorem). He/she will then apply the model to observations of brown dwarfs and giant exoplanets observed by direct imaging, in particular the publicly available JWST data. This tool could also be applied to transiting exoplanets observed with JWST or with the future Ariel and ELT telescopes.
Compétences
– PhD in physics, astronomy, atmospheric science or a related discipline
– Expertise in radiative transfer
– Knowledge of Python language
– Good command of written and spoken English
Modalités
Candidates should provide : – a CV ; – a letter of motivation ; – a complete list of publications and a separate list of first-author publications ; – the PhD certificate or, if not yet earned, the date of defense ; – two reference letters.
The initial deadline for application is set to August 25, 2024 and evaluation will start immediately after. But applications will be received until the position is filled. The position could start as early as October 2024 and until February 2025.
Applications must be submitted electronically to benjamin.charnay obspm.fr.