TOI-2119: A transiting brown dwarf orbiting an active M-dwarf from NASA’s TESS mission

Theron W. Carmichael*, Jonathan M. Irwin, Felipe Murgas, Enric Pallé, Keivan G. Stassun, Matthew Bartnik, Karen A. Collins, Jerome de Leon, Emma Esparza-Borges, Jeremy Fedewa, William Fong, Akihiko Fukui, Jon M. Jenkins, Taiki Kagetani, David W. Latham, Michael B. Lund, Andrew W. Mann, Dan Moldovan, Edward H. Morgan, Norio NaritaShane Painter, Hannu Parviainen, Elisa V. Quintana, George R. Ricker, Jack Schulte, Richard P. Schwarz, Sara Seager, Kirill Sokolovsky, Joseph D. Twicken, Joshua N. Winn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report the discovery of TOI-2119b, a transiting brown dwarf (BD) that orbits and is completely eclipsed by an active Mdwarf star. Using light curve data from the Transiting Exoplanet Survey Satellite mission and follow-up high-resolution Doppler spectroscopic observations, we find the BD has a radius of 𝑅𝑏 = 1.08 ± 0.03RJ, a mass of 𝑀𝑏 = 64.4 ± 2.3MJ, an orbital period of 𝑃 = 7.200865 ± 0.00002 days, and an eccentricity of 𝑒 = 0.337 ± 0.002. The host star has a mass of 𝑀★ = 0.53 ± 0.02M⊙, a radius of 𝑅★ = 0.50 ± 0.01R⊙, an effective temperature of 𝑇eff = 3621 ± 48K, and a metallicity of [Fe/H] = +0.06 ± 0.08.
TOI-2119b joins an emerging population of transiting BDs around M-dwarf host stars, with TOI-2119 being the ninth such system. These M-dwarf–brown dwarf systems typically occupy mass ratios near 𝑞 = 𝑀𝑏/𝑀★ ≈ 0.1 − 0.2, which separates them from the typical mass ratios for systems with transiting substellar objects and giant exoplanets that orbit more massive stars. The
nature of the secondary eclipse of the BD by the star enables us to estimate the effective temperature of the substellar object to be 2030 ± 84K, which is consistent with predictions by substellar evolutionary models.
Original languageEnglish
Pages (from-to)4944-4957
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date16 Jun 2022
Publication statusPublished - 1 Aug 2022


  • astro-ph.SR
  • astro-ph.EP
  • techniques: radial velocities
  • techniques: photometric
  • techniques: spectroscopic
  • (stars:) brown dwarfs
  • stars: low-mass


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