Water depletion and 15NH3 in the atmosphere of the coldest brown dwarf observed with JWST/MIRI

• DOI: 10.48550/arxiv.2410.10933
• Publication Date: 2024-10-14
• Authors: H. Kühnle; Polychronis Patapis; P. Mollière; Pascal Tremblin; Elisabeth C. Matt...; Adrian M. Glauser; Niall Whiteford; Malavika Vasist; Olivier Absil; D. Barrado; M. Min; Pierre-Olivier La...; L. B. F. M. Waters; M. Güedel; Th. Henning; B. Vandenbussche; Pierre Baudoz; L. Decin; J. P. Pye; P. Royer; E. F. van Dishoeck; Göran Östlin; T. P. Ray; Gillian Wright
• Keywords: Modified atmosphere

With a temperature of $\sim 285$ K WISE0855 is the coldest brown dwarf observed so far. Using James Webb Space Telescope (JWST) we obtained observations that allow us to characterize WISE0855s atmosphere focusing on vertical variation in water steam abundance, measuring trace gas abundances and receiving bulk parameters for this cold object. We ultra cool using Mid-Infrared Instrument Medium Resolution Spectrometer (MIRI/MRS) onboard JWST at spectral resolution up 3750. combined observation with published data from Near Infrared Spectrograph (NIRSpec) G395M PRISM modes yielding spectrum ranging 0.8 22 um. apply atmospheric retrievals petitRADTRANS measure abundances, pressure-temperature structure, radius gravity dwarf. also employ publicly available clear cloudy self-consistent grid models estimate properties such as effective temperature, radius, metallicity. Atmospheric constrain variable abundance profile atmosphere, predicted by equilibrium chemistry. detect 15NH3 isotopologue infer ratio mass fraction 14NH3/15NH3 = 332+63-43 retrieval. bolometric luminosity integrating presented obtain value log(L/L$_{\odot}$) -7.291+/-0.008. The detected depletion indicates condenses out upper due very low WISE0855. height where occurs covered MIRI/MRS data, thus demonstrates potential MIRI giants atmospheres. Comparing models, do not signs ice clouds, although their features have been previous studies.