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

November 2021 • 2021ApJ...921..140S

Authors • 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-poor ([Fe/H] = -0.40 ± 0.12) with an age of ${7.2}_{-3.6}^{+3.8}$ 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 ${500}_{-100}^{+115}$ 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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2021ApJ...921..140S
• PDF https://iopscience.iop.org/article/10.3847/1538-4357/ac1c75/pdf
• PREPRINT http://arxiv.org/abs/2108.05321
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2021ApJ...921..140S
• DATA https://irsa.ipac.caltech.edu/bibdata/2021/S/2021ApJ...921..140S.html
• ELECTR https://doi.org/10.3847%2F1538-4357%2Fac1c75