Resolving Mass Benchmarks for Ultracool Atmospheres
Abstract
The atmospheres of low-mass stars and brown dwarfs have cool temperatures that foster abundant molecules, complex chemical and dynamical processes, and poorly understood condensate clouds. Developing accurate models of these atmospheres is critical for a wide range of problems, from interpreting the spectra of directly imaged planets to accurate modeling of the long-term evolution of the lowest-mass planetary systems. Despite increasing theoretical sophistication, evaluating the accuracy of these models has been long been limited by the lack of objects with well-determined fundamental properties.
We propose to obtain spatially-resolved optical and IR spectra for a unique sample of ultracool dwarf binaries (M7-T5 spectral types) that have high-precision dynamical masses for the individual components (30-100 Jupiter masses), derived from more than decade of orbit monitoring. Mass measurements break degeneracies between poorly known model parameters, such as those governing cloud formation and fundamental properties like surface gravity. Our HST spectra for this sample of binary systems will establish the gold standard for studies of ultracool atmospheric physics. This is the only sample of ultracool binaries that are resolvable by HST (and JWST in the future) that have precisely measured component masses.- Publication:
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HST Proposal
- Pub Date:
- May 2020
- Bibcode:
- 2020hst..prop16268D