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

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

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17 Scopus citations


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.

Original languageEnglish (US)
Article number144
JournalAstronomical Journal
Issue number4
StatePublished - Oct 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Brown dwarfs
  • M dwarf stars
  • Radial velocity
  • Transit photometry
  • Transits


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