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

  • Triaud, Amaury H. M. J.
  • Dransfield, Georgina
  • Kagetani, Taiki
  • Timmermans, Mathilde
  • Narita, Norio
  • Barkaoui, Khalid
  • Hirano, Teruyuki
  • Rackham, Benjamin V.
  • Mori, Mayuko
  • Baycroft, Thomas
  • Benkhaldoun, Zouhair
  • Burgasser, Adam J.
  • Caldwell, Douglas A.
  • Collins, Karen A.
  • Davis, Yasmin T.
  • Delrez, Laetitia
  • Demory, Brice-Oliver
  • Ducrot, Elsa
  • Fukui, Akihiko
  • Muñoz, Clàudia Jano
  • And 23 more
Publication Date
Oct 01, 2023
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peer reviewed / 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 R_Jup for the planet, a mass of 0.34 M_\odot 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 M_Jup. Based on its overall density, TOI-4860 b appears to be rich in heavy elements, like its host star.

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