A Wide Planetary Mass Companion Discovered through the Citizen Science Project Backyard Worlds: Planet 9
Journal
Date Issued
2021
Author(s)
Faherty, Jacqueline K.
•
Gagné, Jonathan
•
Popinchalk, Mark
•
Vos, Johanna M.
•
Burgasser, Adam J.
•
Schümann, Jörg
•
Schneider, Adam C.
•
Kirkpatrick, J. Davy
•
Meisner, Aaron M.
•
Kuchner, Marc J.
•
Bardalez Gagliuffi, Daniella C.
•
Marocco, Federico
•
Caselden, Dan
•
Gonzales, Eileen C.
•
Rothermich, Austin
•
Casewell, Sarah L.
•
Debes, John H.
•
Aganze, Christian
•
Ayala, Andrew
•
Hsu, Chih-Chun
•
Cooper, William J.
•
•
Gerasimov, Roman
•
Theissen, Christopher A.
•
Backyard Worlds: Planet 9 Collaboration
Abstract
Through the Backyard Worlds: Planet 9 citizen science project we discovered a late-type L dwarf co-moving with the young K0 star BD+60 1417 at a projected separation of 37″ or 1662 au. The secondary-CWISER J124332.12+600126.2 (W1243)-is detected in both the CatWISE2020 and 2MASS reject tables. The photometric distance and CatWISE proper motion both match that of the primary within ~1σ and our estimates for a chance alignment yield a zero probability. Follow-up near-infrared spectroscopy reveals W1243 to be a very red 2MASS (J-K s = 2.72), low surface gravity source that we classify as L6-L8γ. Its spectral morphology strongly resembles that of confirmed late-type L dwarfs in 10-150 Myr moving groups as well as that of planetary mass companions. The position on near- and mid-infrared color-magnitude diagrams indicates the source is redder and fainter than the field sequence, a telltale sign of an object with thick clouds and a complex atmosphere. For the primary we obtained new optical spectroscopy and analyzed all available literature information for youth indicators. We conclude that the Li I abundance, its loci on color-magnitude and color-color diagrams, and the rotation rate revealed in multiple TESS sectors are all consistent with an age of 50-150 Myr. Using our re-evaluated age of the primary and the Gaia parallax, along with the photometry and spectrum for W1243, we find T eff = 1303 ± 31 K, log g = 4.3 ± 0.17 cm s-2, and a mass of 15 ± 5 M Jup. We find a physical separation of ~1662 au and a mass ratio of ~0.01 for this system. Placing it in the context of the diverse collection of binary stars, brown dwarfs, and planetary companions, the BD+60 1417 system falls in a sparsely sampled area where the formation pathway is difficult to assess.
Volume
923
Issue
1
Start page
48
Issn Identifier
0004-637X
Ads BibCode
2021ApJ...923...48F
Rights
open.access
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