TOI-1278 B: SPIRou Unveils a Rare Brown Dwarf Companion in Close-in Orbit around an M Dwarf

October 2021 • 2021AJ....162..144A

Authors • Artigau, Étienne • Hébrard, Guillaume • Cadieux, Charles • Vandal, Thomas • Cook, Neil J. • Doyon, René • Gagné, Jonathan • Moutou, Claire • Martioli, Eder • Frasca, Antonio • Jahandar, Farbod • Lafrenière, David • Malo, Lison • Donati, Jean-François • Cortés-Zuleta, Pía • Boisse, Isabelle • Delfosse, Xavier • Carmona, Andres • Fouqué, Pascal • Morin, Julien • Rowe, Jason • Marino, Giuseppe • Papini, Riccardo • Ciardi, David R. • Lund, Michael B. • Martins, Jorge H. C. • Pelletier, Stefan • Arnold, Luc • Bouchy, François • Forveille, Thierry • Santos, Nuno C. • Bonfils, Xavier • Figueira, Pedro • Fausnaugh, Michael • Ricker, George • Latham, David W. • Seager, Sara • Winn, Joshua N. • Jenkins, Jon M. • Ting, Eric B. • Torres, Guillermo • Gomes da Silva, João

Abstract • We present the discovery of an 18.5 ± 0.5 M_Jup 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_⋆/M_comp ~ 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.

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David Ciardi

Senior Scientist