TOI-1278 B: SPIRou Unveils a Rare Brown Dwarf Companion in Close-in Orbit around an M Dwarf
Torres, Guillermo; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Ciardi, David R.; Lund, Michael B.; Gagné, Jonathan; Fausnaugh, Michael; Ting, Eric B.; Bouchy, François; Vandal, Thomas; Doyon, René; Donati, Jean-François; Ricker, George; Lafrenière, David; Martioli, Eder; Bonfils, Xavier; Forveille, Thierry; Figueira, Pedro; Delfosse, Xavier; Santos, Nuno C.; Morin, Julien; Artigau, Étienne; Cook, Neil J.; Gomes da Silva, João; Carmona, Andres; Moutou, Claire; Fouqué, Pascal; Hébrard, Guillaume; Pelletier, Stefan; Rowe, Jason; Cadieux, Charles; Jahandar, Farbod; Arnold, Luc; Boisse, Isabelle; Frasca, Antonio; Papini, Riccardo; Cortés-Zuleta, Pía; Martins, Jorge H. C.; Malo, Lison; Marino, Giuseppe
Canada, France, Brazil, Italy, United States, Portugal, Switzerland, Chile
Abstract
We present the discovery of an 18.5 ± 0.5 MJup brown dwarf (BD) companion to the M0V star TOI-1278. The system was first identified through a percent-deep transit in Transiting Exoplanet Survey Satellite photometry; further analysis showed it to be a grazing transit of a Jupiter-sized object. Radial velocity (RV) follow-up with the SPIRou near-infrared high-resolution velocimeter and spectropolarimeter in the framework of the 300-night SPIRou Legacy Survey carried out at the Canada-France-Hawaii Telescope led to the detection of a Keplerian RV signal with a semi-amplitude of 2306 ± 10 m s-1 in phase with the 14.5 day transit period, with a slight but nonzero eccentricity. The intermediate-mass ratio (M⋆/Mcomp ~ 31) is unique for having such a short separation (0.095 ± 0.001 au) among known M-dwarf systems. Interestingly, M-dwarf-BD systems with similar mass ratios exist with separations of tens to thousands of astronomical unit.