| Abstract: | We present the highest fidelity spectrum to date of a planetary-mass object.
VHS 1256 b is a $<$20 M$_mathrm{Jup}$ widely separated ($sim$8", a = 150 au),
young, brown dwarf companion that shares photometric colors and spectroscopic
features with the directly imaged exoplanets HR 8799 c, d, and e. As an L-to-T
transition object, VHS 1256 b exists along the region of the color-magnitude
diagram where substellar atmospheres transition from cloudy to clear. We
observed VHS 1256 b with JWST’s NIRSpec IFU and MIRI MRS modes for coverage
from 1 $mu$m to 20 $mu$m at resolutions of $sim$1,000 - 3,700. Water,
methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in
several portions of the JWST spectrum based on comparisons from template brown
dwarf spectra, molecular opacities, and atmospheric models. The spectral shape
of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly
detect silicate clouds, the first such detection reported for a planetary-mass
companion. |
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