Abstract

Atmospheric abundances play an important role in planetary physics, allowing us to probe the formation mechanisms of exoplanets through bulk constraints on metallicity and carbon-to-oxygen ratios. Recently however, we have been able to constrain isotope ratios in exoplanetary atmospheres, both for transiting and directly-imaged companions. These add an extra dimension to probe formation processes, as well as providing insights into interstellar chemistry. While carbon isotope ratios are broadly consistent across the Solar System, in molecular clouds and protoplanetary disks, carbon isotope ratios can be altered by gas/ice partitioning, isotopic ion-exchange reactions and isotope-selective photodissociation. Hence we can obtain a great deal of insight into the planet’s history through studying the isotopic ratio. In this talk I will discuss the results from two directly-imaged companions, VHS 1256 b and AB Pictoris b, which show differences in the 12/13C ratios in their atmospheres from observations with JWST and VLT respectively. I will compare and contrast these isotope ratios to the Solar System, transiting exoplanets as well as other directly-imaged targets and field brown dwarfs, to understand their formation histories. I will also delve into the oxygen isotope ratio constraints that we are able to constrain for VHS 1256 b, and the variability that we see between night to night for the AB Pictoris b observations. Finally, I will discuss the orbital solution of AB Pictoris b, and the orbital obliquity and inclination constraints that we obtain from the high resolution observations.