Ross 19B: An Extremely Cold Companion Discovered via the Backyard Worlds: Planet 9 Citizen Science Project

Creators: Schneider, Adam C.; Meisner, Aaron M.; Gagné, Jonathan; Faherty, Jacqueline K.; Marocco, Federico; Burgasser, Adam J.; Kirkpatrick, J. Davy; Kuchner, Marc J.; Gramaize, Léopold; Rothermich, Austin; Brooks, Hunter; Vrba, Frederick J.; Bardalez Gagliuffi, Daniella; Caselden, Dan; Cushing, Michael C.; Gelino, Christopher R.; Line, Michael R.; Casewell, Sarah L.; Debes, John H.; Aganze, Christian; Ayala, Andrew; Gerasimov, Roman; Gonzales, Eileen C.; Hsu, Chih-Chun; Kiman, Rocio; Popinchalk, Mark; Theissen, Christopher; Backyard Worlds: Planet 9 Collaboration

Abstract

Through the Backyard Worlds: Planet 9 citizen science project, we have identified a wide-separation (∼10', ∼9900 au projected) substellar companion to the nearby (∼17.5 pc), mid-M dwarf Ross 19. We have developed a new formalism for determining chance alignment probabilities based on the BANYAN Σ tool, and find a 100% probability that this is a physically associated pair. Through a detailed examination of Ross 19A, we find that the system is metal-7.2^(+3.8)_(−3.6) poor ([Fe/H] = −0.40 ± 0.12) with an age of Gyr. Combining new and existing photometry and astrometry, we find that Ross 19B is one of the coldest known wide-separation companions, with a spectral type on the T/Y boundary, an effective temperature of 500^(+115)_(−100) K, and a mass in the range 15–40 M_(Jup). This new, extremely cold benchmark companion is a compelling target for detailed characterization with future spectroscopic observations using facilities such as the Hubble Space Telescope or James Webb Space Telescope.

Additional Information

© 2021. The American Astronomical Society. Received 2021 June 25; revised 2021 July 30; accepted 2021 August 9; published 2021 November 9. The Backyard Worlds: Planet 9 team would like to thank the many Zooniverse volunteers who have participated in this project, from providing feedback during the beta review stage to classifying flipbooks to contributing to the discussions on TALK. We would also like to thank the Zooniverse web development team for their work creating and maintaining the Zooniverse platform and the Project Builder tools. This research was supported by NASA grant 2017-ADAP17-0067. This material is based upon work supported by the National Science Foundation under grant No. 2007068, 2009136, and 2009177. F.M. also acknowledges support from grant 80NSSC20K0452 under the NASA Astrophysics Data Analysis Program. E.G. acknowledges support from the Heising-Simons Foundation. (Some of) 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. 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. Software: crowdsource (Schlafly et al. 2018, 2019), BANYAN Σ (Gagné et al. 2018a), CoMover (Gagné et al. 2021), SEDkit (Filippazzo 2020), SpeXTool (Cushing et al. 2004).

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