TOI-4860 b, a short-period giant planet transiting an M3.5 dwarf
J. M. Almenara, X. Bonfıls, Edward M. Bryant, Andrés Jordán, G. Hébrard, Eder Martioli, A. C. M. Correia, N. Astudillo-Defru, Charles Cadieux, L. Arnold, Étienne Artigau, G. Á. Bakos, S. C. C. Barros, Daniel Bayliss, F. Bouchy, Gwenaël Boué, Rafael Brahm, A. Carmona, D. Charbonneau, David R. Ciardi, Ryan Cloutier, Marion Cointepas, Neil J. Cook, Nicolas B. Cowan, X. Delfosse, J.-D. do Nascimento, J.‐F. Donati, René Doyon, T. Forveille, P. Fouqué, Eric Gaidos, Emily A. Gilbert, J. Gomes da Silva, J. D. Hartman, Katharine Hesse, Mélissa J. Hobson, Jon M. Jenkins, F. Kiefer, Veselin B. Kostov, J. Laskar, M. Lendl, Alexandrine L’Heureux, J. H. C. Martins, Kristen Menou, C. Moutou, F. Murgas, Alex S. Polanski, David Rapetti, Elyar Sedaghati, Hsien Shang
Abstract
We report the discovery and characterisation of a giant transiting planet orbiting a nearby M3.5V dwarf ( d = 80.4pc, G = 15.1 mag, K =11.2mag, R * = 0.358 ± 0.015 R ⊙ , M * = 0.340 ± 0.009 M ⊙ ). Using the photometric time series from TESS sectors 10, 36, 46, and 63 and near-infrared spectrophotometry from ExTrA, we measured a planetary radius of 0.77 ± 0.03 R J and an orbital period of 1.52 days. With high-resolution spectroscopy taken by the CFHT/SPIRou and ESO/ESPRESSO spectrographs, we refined the host star parameters ([Fe/H] = 0.27 ± 0.12) and measured the mass of the planet (0.273 ± 0.006 M J ). Based on these measurements, TOI-4860 b joins the small set of massive planets (>80 M E ) found around mid to late M dwarfs (<0.4 R ⊙ ), providing both an interesting challenge to planet formation theory and a favourable target for further atmospheric studies with transmission spectroscopy. We identified an additional signal in the radial velocity data that we attribute to an eccentric planet candidate ( e = 0.66 ± 0.09) with an orbital period of 427 ± 7 days and a minimum mass of 1.66 ± 0.26 M J , but additional data would be needed to confirm this.