An M dwarf accompanied by a close-in giant orbiter with SPECULOOS

Amaury H.M.J. Triaud, Georgina Dransfield, Taiki Kagetani, Mathilde Timmermans, Norio Narita, Khalid Barkaoui, Teruyuki Hirano, Benjamin V. Rackham, Mayuko Mori, Thomas Baycroft, Zouhair Benkhaldoun, Adam J. Burgasser, Douglas A. Caldwell, Karen A. Collins, Yasmin T. Davis, Laetitia Delrez, Brice Oliver Demory, Elsa Ducrot, Akihiko Fukui, Clàudia Jano MuñozEmmanuël Jehin, Lionel J. García, Mourad Ghachoui, Michaël Gillon, Yilen Gómez Maqueo Chew, Matthew J. Hooton, Masahiro Ikoma, Kiyoe Kawauchi, Takayuki Kotani, Alan M. Levine, Enric Pallé, Peter P. Pedersen, Francisco J. Pozuelos, Didier Queloz, Owen J. Scutt, Sara Seager, Daniel Sebastian, Motohide Tamura, Samantha Thompson, Noriharu Watanabe, Julien de Wit, Joshua N. Winn, Sebastián Zúñiga-Fernández

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


In the last decade, a dozen close-in giant planets have been discovered orbiting stars with spectral types ranging from M0 to M4, a mystery since known formation pathways do not predict the existence of such systems. Here, we confirm TOI-4860 b, a Jupiter-sized planet orbiting an M4.5 host, a star at the transition between fully and partially convective interiors. First identified with TESS data, we validate the transiting companion’s planetary nature through multicolour photometry from the TRAPPIST-South/North, SPECULOOS, and MuSCAT3 facilities. Our analysis yields a radius of 0.76 ± 0.02 RJup for the planet, a mass of 0.34 M for the star, and an orbital period of 1.52 d. Using the newly commissioned SPIRIT InGaAs camera at the SPECULOOS-South Observatory, we collect infrared photometry in zYJ that spans the time of secondary eclipse. These observations do not detect a secondary eclipse, placing an upper limit on the brightness of the companion. The planetary nature of the companion is further confirmed through high-resolution spectroscopy obtained with the IRD spectrograph at Subaru Telescope, from which we measure a mass of 0.67 ± 0.14 MJup. Based on its overall density, TOI-4860 b appears to be rich in heavy elements, like its host star.

Original languageEnglish (US)
Pages (from-to)L98-L104
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - Oct 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • exoplanets
  • infrared: planetary systems
  • techniques: photometric
  • techniques: radial velocities


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