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

2023; Oxford University Press; Volume: 525; Issue: 1 Linguagem: Inglês

10.1093/mnrasl/slad097

1745-3933

A. H. M. J. Triaud, Georgina Dransfield, T. Kagetani, Mathilde Timmermans, Norio Narita, Khalid Barkaoui, Teruyuki Hirano, Benjamin V. Rackham, M. Mori, Thomas Baycroft, Z. Benkhaldoun, Adam J. Burgasser, Douglas A. Caldwell, Karen A. Collins, Yasmin Davis, L. Delrez, Brice-Olivier Demory, Elsa Ducrot, Akihiko Fukui, Clàudia Jano Muñoz, Emmanuël Jehin, L. J. Garcia, Mourad Ghachoui, M. Gillon, Y. Gómez Maqueo Chew, M. J. Hooton, Masahiro Ikoma, Kiyoe Kawauchi, Takayuki Kotani, Alan M. Levine, Ε. Πάλλη, P. P. Pedersen, F. J. Pozuelos, D. Queloz, Owen J Scutt, Sara Seager, Daniel Sebastian, Motohide Tamura, Samantha Thompson, Noriharu Watanabe, Julien de Wit, Joshua N. Winn, Sebastián Zúñiga-Fernández,

Astronomy and Astrophysical Research

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 $0.76 \pm 0.02~ \rm R_{Jup}$ for the planet, a mass of $0.34~\rm M_\odot$ 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 $0.67 \pm 0.14~\rm M_{Jup}$ . Based on its overall density, TOI-4860 b appears to be rich in heavy elements, like its host star.