Characterization of HD 206893 B from Near- to Thermal-infrared
Résumé
HD 206893 B is a brown dwarf companion orbiting inside the debris disk of its host star. We detect the brown dwarf in M s-band using the Keck/NIRC2 instrument and vortex coronagraph. We measure its magnitude to be M s = 12.97 0.10 −0.11. It is at an angular separation of 0.22 ± 0.03 arcsec, and a position angle (PA) of 39.6 ± 5.4 deg East of North. Using this M s-band measurement and the system age, we use three evolutionary models to estimate the mass to be 12-78 M Jup. We analyze the atmospheric properties from 1 to 5 microns using a grid of simulated atmospheric models. We find that a sedimentation flux f sed value ∼0.2 provides the best fit to the data, suggesting high vertically extended clouds. This may be indicative of high altitude grains or a circumplanetary disk. Our model radii and luminosities for the companion find the best-fits are ages of <100 Myr and masses <20 M Jup , consistent with our mass estimate from the evolutionary models using the M s-band data alone. We detect orbital motion of the brown dwarf around the host star in comparison to the discovery image and derive orbital parameters. Finally we analyze how the companion brown dwarf interacts with the debris disk by estimating the location of the chaotic zone around the brown dwarf using values derived from this study's estimated mass and orbital constraints. We find that the collisions within the debris belt are likely driven by secular perturbations from the brown dwarf, rather than self-stirring.
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