Niall Whiteford — Directly-imaged atmospheric characterisation with TauREx retrievals

Inverse methods have become a fundamental analysis technique for modelling exoplanetary atmospheres. This technique explores a variety of potential bulk and atmospheric model parameters that combine to best-fit an observed spectrum. TauREx (Tau Retrieval of Exoplanets) is a Bayesian retrieval suite designed to be applied to spectroscopic observations of extrasolar planetary atmospheres. We have adapted TauREx for analysis of near-infrared spectrophotometry from a variety of directly-imaged gas giant exoplanets and brown dwarfs. This includes the HR 8799 system, Beta Pic b, 51 Eri b, and PSO 318 observed using instruments such as SPHERE, GPI and GNIRS. We also perform retrieval analysis on L and T dwarf spectra from the IRTF SpeX Spectral Library. This analysis returns estimates for target mass, radius, surface gravity, temperature-pressure structure and cloud properties, as well as confirming and constraining the presence of a variety of molecular species including H2O, CO and CH4. Inverse techniques have mainly been applied to transit spectroscopy in the past and as a result, this is the first application of retrieval analysis to many directly-imaged targets. This project aims to help bridge directly-imaged exoplanet observations with robust, efficient and precise characterisation. The development and adaptation of this retrieval tool is timely and relevant given the upcoming launch of JWST. In this talk I will present a summary of the novel retrieval results from this project.