Characterization of HD 206893 B from Near- to Thermal-infrared

Creators: Meshkat, Tiffany; Gao, Peter; Lee, Eve J.; Mawet, Dimitri; Choquet, Élodie; Ygouf, Marie; Patel, Rahul; Ruane, Garreth; Wang, Jason; Wallack, Nicole; Absil, Olivier; Beichman, Charles

Abstract

HD 206893 B is a brown-dwarf companion orbiting inside the debris disk of its host star. We detect the brown dwarf in the Ms band using the Keck/NIRC2 instrument and vortex coronagraph. We measure its magnitude to be M_s 12.97_(-0.11)^(0.10). It is at an angular separation of 0farcs22 ± 0farcs03, and a position angle of 39.6° ± 5.4° east of north. Using this Ms-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 1–5 μm 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 Ms-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.

Additional Information

© 2021. The American Astronomical Society. Received 2020 December 7; revised 2021 June 5; accepted 2021 June 8; published 2021 August 17. We thank the anonymous referee for their helpful suggestions that improved this paper. We thank our Keck/NIRC2 support staff, without whom the data could not have been obtained: Cynthia, Terry Stickel, Greg Doppmann, Bruno Femenía Castellá, and Carlos Alvarez. P.G. and J.W. acknowledge support from the 51 Pegasi b Fellowship sponsored by the Heising-Simons Foundation. P.G. is also supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51456.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Part of this work has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 819155). This research has made use of the SVO Filter Profile Service (http://svo2.cab.inta-csic.es/theory/fps/) supported from the Spanish MINECO through grant AYA2017-84089. The plots presented in this paper we created using matplotlib in python (Hunter 2007). The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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