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The Horse in Front of the Cart: Ensemble Validation of Ultracool Model Atmospheres for Imaged Exoplanets and Brown Dwarfs

Presentation #626.01 in the session Planetary Atmospheres - Directly Imaged Planets and Brown Dwarfs.

Published onApr 03, 2024
The Horse in Front of the Cart: Ensemble Validation of Ultracool Model Atmospheres for Imaged Exoplanets and Brown Dwarfs

Model atmospheres lie at the crux of converting observable quantities (colors, magnitudes and spectra) into the physical measurements needed to advance our understanding of imaged exoplanets and brown dwarfs (e.g., temperatures, gravities, metallicities, and radii). Such work is handicapped both by the systematic uncertainties/errors in the models and a shortfall of data-versus-model comparisons, as most studies focus on individual objects or small samples of particular interest. Here we present another path for understanding the strengths and limitations of current model atmospheres, through large-scale homogenous analysis of brown dwarfs and planetary-mass objects. Using an unprecedently large sample (1000+ objects), we fit near-IR spectra and photometry for objects from the stellar/substellar boundary down to a few Jupiter masses using model atmospheres and then examine the results en masse. Such ensemble analysis allows us to validate the model atmospheres as a function of wavelength range, temperature, and age, as well as to robustly highlight model shortcomings. We also compare such work to more precise studies with smaller samples of substellar benchmarks, namely objects with with well-established ages and compositions, found both as companions and in young stellar moving groups.

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