Gemini Planet Imager Spectroscopy of the Dusty Substellar Companion HD 206893 B

Creators: Ward-Duong, K.; Patience, J.; Follette, K.; De Rosa, R. J.; Rameau, J.; Marley, M.; Saumon, D.; Nielsen, E. L.; Rajan, A.; Greenbaum, A. Z.; Lee, J.; Wang, J. J.; Czekala, I.; Duchêne, G.; Macintosh, B.; Ammons, S. Mark; Bailey, V. P.; Barman, T.; Bulger, J.; Chen, C.; Chilcote, J.; Cotten, T.; Doyon, R.; Esposito, T. M.; Fitzgerald, M. P.; Gerard, B. L.; Goodsell, S. J.; Graham, J. R.; Hibon, P.; Hom, J.; Hung, L.-W.; Ingraham, P.; Kalas, P.; Konopacky, Q.; Larkin, J. E.; Maire, J.; Marchis, F.; Marois, C.; Metchev, S.; Millar-Blanchaer, M. A.; Oppenheimer, R.; Palmer, D.; Perrin, M.; Poyneer, L.; Pueyo, L.; Rantakyrö, F. T.; Ren, B.; Ruffio, J.-B.; Savransky, D.; Schneider, A. C.; Sivaramakrishnan, A.; Song, I.; Soummer, R.; Tallis, M.; Thomas, S.; Wallace, J. Kent; Wiktorowicz, S.; Wolff, S.

Abstract

We present new near-infrared Gemini Planet Imager (GPI) spectroscopy of HD 206893 B, a substellar companion orbiting within the debris disk of its F5V star. The J, H, K1, and K2 spectra from GPI demonstrate the extraordinarily red colors of the object, confirming it as the reddest substellar object observed to date. The significant flux increase throughout the infrared presents a challenging atmosphere to model with existing grids. Best-fit values vary from 1200 to 1800 K for effective temperature and from 3.0 to 5.0 for log(g), depending on which individual wavelength band is fit and which model suite is applied. The extreme redness of the companion can be partially reconciled by invoking a high-altitude layer of submicron dust particles, similar to dereddening approaches applied to the peculiar red field L dwarf population. However, reconciling the HD 206893 B spectra with even those of the reddest low-gravity L dwarf spectra still requires the contribution of additional atmospheric dust, potentially due to the debris disk environment in which the companion resides. Orbit fitting from 4 yr of astrometric monitoring is consistent with a ~30 yr period, an orbital inclination of 147°, and a semimajor axis of 10 au, well within the estimated disk inner radius of ~50 au. As one of a very few substellar companions imaged interior to a circumstellar disk, the properties of this system offer important dynamical constraints on companion–disk interaction and provide a benchmark for substellar and planetary atmospheric study.

Additional Information

© 2020. The American Astronomical Society. Received 2019 September 16; revised 2020 October 15; accepted 2020 October 15; published 2020 December 2. We thank the anonymous referee for an exceptionally thoughtful and comprehensive report that greatly benefited this manuscript. K.W.D. thanks Alan Jackson for helpful conversations on debris disk dust properties, and Brian Svoboda, Sarah Betti, Mike Petersen, Daniella Bardalez-Gagliuffi, Sarah Logsdon, and Emily Martin for helpful discussions and feedback. This work is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina), and Ministerio da Ciencia, Tecnologia e Inovacao (Brazil). This research has made use of the SIMBAD and VizieR databases, operated at CDS, Strasbourg, France. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract No. DE-AC02-05CH11231. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant No. ACI-1548562. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work was supported by NSF grants AST-1411868 (K.W.D., A.R., J.P., B.M., E.L.N., and K.B.F.), AST-141378 (G.D.), and AST-1518332 (R.D.R., J.J.W., T.M.E., J.R.G., and P.G.K.). Some authors were supported by NASA grants NNX14AJ80G (E.L.N., S.C.B., B.M., F.M., and M.P.), NNX15AC89G and NNX15AD95G (B.M., J.E.W., T.M.E., R.J.D.R., G.D., J.R.G., and P.G.K.), NN15AB52l (D.S.), and NNX16AD44G (K.M.M). K.W.D. was supported by an NRAO Student Observing Support Award (SOSPA3-007). D.S.'s contribution was supported by NASA grant NNH15AZ59I. J.R., R.D., and D.L. acknowledge support from the Fonds de Recherche du Quebec. J.R.M.'s work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. Support for M.M.B.'s work was provided by NASA through Hubble Fellowship grant No. 51378.01-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. J.J.W. is supported by the Heising-Simons Foundation 51 Pegasi b postdoctoral fellowship. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. This work benefited from NASA's Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA's Science Mission Directorate.

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