Cloud composition and origin of the reddest known sub-stellar companion HD 206893 B
Abstract
JWST will open up a new parameter space for studying exoplanet atmospheres in the near- and mid-infrared beyond ~3 microns. The reddest known sub-stellar companion HD 206893 B represents an important and extreme test case for atmospheric models of exoplanets and brown dwarfs, and its unusual color sets constraints on the cloud composition and dust parameters which such models need to predict. Currently, no atmospheric model can predict the extremely red color of HD 206893 B. We aim to study the composition and size distribution of the dust grains causing the red color of HD 206893 B. Moreover, we aim to constrain the C/O abundance ratio of HD 206893 B, which will in turn unravel its formation history and resolve the current uncertainty about its age and mass. Located at an angular separation of ~200 mas from its host star and with a contrast of ~7.5-8.5 mag, we identify aperture masking interferometry with NIRISS as the only way to study this companion at ~4-5 microns with sufficient precision to discriminate dust grain properties and constrain its C/O abundance. L- and M-band observations with JWST are key for understanding the nature of HD 206893 B's atmosphere and the formation history of this enigmatic object. Ultimately, these observations will provide a benchmark test for improving atmospheric models of very cloudy and dusty sub-stellar objects and increase the reliability of such models in the ~4-5 microns regime which is hardly accessible from the ground.
- Publication:
-
JWST Proposal. Cycle 1
- Pub Date:
- March 2021
- Bibcode:
- 2021jwst.prop.1843K