PF-07-0014

Probing the Formation of Three Directly-Imaged Planetary-Mass Objects using Atmospheric Retrievals

Jacob Meadus, Marta Bryan, Jerry W. Xuan, Paul Molliere, Heather Knutson

Constraining the atmospheric composition of an exoplanet can potentially grant insight into its formation history, since the materials available to build a planet can depend on where, when, and how that planet forms. Here we explore the formation history of a young super-Jupiter discovered by direct imaging by measuring the atmospheric C/O ratios and metallicities of three planetary-mass objects. All three objects are in the beta Pic moving group, meaning they have similar ages and formation conditions. The objects also have comparable early L spectral types, and therefore similar masses. The main difference is that two of the three objects are free-floating and are likely to have formed from gravitational collapse, whereas the third is bound to a host star and has a formation history that is unknown. We use low-resolution (R~100) spectra for these three objects with the open-source atmospheric retrieval code petitRADTRANS, and explore whether the presence of clouds affect the retrieved abundances from the low-resolution spectra. Next we will obtain abundance constraints using high-resolution (R~25,000) spectra, and compare atmospheric compositions between the three objects. If the two isolated objects have similar compositions and the bound one does not, this could point to a difference in formation history for the bound companion. Further work will expand this pilot sample to a larger population of objects.