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Precision Abundances of Ultracool T-T Pairs: A Critical Comparison to Directly Imaged and Transiting Planets

Presentation #626.18 in the session Planetary Atmospheres - Directly Imaged Planets and Brown Dwarfs.

Published onApr 03, 2024
Precision Abundances of Ultracool T-T Pairs: A Critical Comparison to Directly Imaged and Transiting Planets

Measurements of atmospheric abundances in brown dwarf and exoplanet companions provide key insight into formation pathways. Formation models make specific predictions on the atmospheric abundances of Carbon (C) and Oxygen (O) in companion atmospheres relative to their host stars that are dependent on formation via core accretion in a disk or gravitational collapse in a cloud core. Using sensitive Wield Field Camera 3 grism observations, we obtained spatially resolved spectra for WISE1217+1626 and WISE1711+3500, two directly imaged brown dwarf - brown dwarf binaries with late T to early Y spectral classification types, for each component. The effective temperatures of these ultra-cool objects make them amenable to atmospheric retrievals which provide the means to measure the abundances of the dominant Carbon and Oxygen bearing species in these substellar atmospheres. Using these measured abundances we calculate C/O and metallicity for each component, making this study a benchmark comparison for the atmospheres of both directly imaged and transiting exoplanet systems. Measuring these quantities for each component enables a test of whether brown dwarf companions form more akin to stellar binaries or like planets in a disk. By studying brown dwarfs in a binary pair, we are able to apply the same modeling and retrieval scheme for each component of the pair, unlike similar analysis with star-planet systems. We will present the initial comparison of the C/O and metallicity for each component in these benchmark systems.

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