TOI-4860 b, a short-period giant planet transiting an M3.5 dwarf

J. M. Almenara; X. Bonfils; E. M. Bryant; A. Jordán; G. Hébrard; E. Martioli; A. C. M. Correia; N. Astudillo-Defru; C. Cadieux; L. Arnold; É. Artigau; G. Á. Bakos; S. C. C. Barros; D. Bayliss; F. Bouchy; G. Boué; R. Brahm; A. Carmona; D. Charbonneau; D. R. Ciardi; R. Cloutier; M. Cointepas; N. J. Cook; N. B. Cowan; X. Delfosse; J. Dias do Nascimento; J. -F. Donati; R. Doyon; T. Forveille; P. Fouqué; E. Gaidos; E. A. Gilbert; J. Gomes da Silva; J. D. Hartman; K. Hesse; M. J. Hobson; J. M. Jenkins; F. Kiefer; V. B. Kostov; J. Laskar; M. Lendl; A. L'Heureux; J. H. C. Martins; K. Menou; C. Moutou; F. Murgas; A. S. Polanski; D. Rapetti; E. Sedaghati; H. Shang

arXiv · 2308.01454

TOI-4860 b, a short-period giant planet transiting an M3.5 dwarf

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Abstract

We report the discovery and characterisation of a giant transiting planet orbiting a nearby M3.5V dwarf (d = 80.4 pc, $G$ = 15.1 mag, $K$=11.2 mag, R$_\star$ = 0.358 $\pm$ 0.015 R$_\odot$, M$_\star$ = 0.340 $\pm$ 0.009 M$_\odot$). 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 $\pm$ 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 $\pm$ 0.12) and measured the mass of the planet (0.273 $\pm$ 0.006 M$_J$). Based on these measurements, TOI-4860 b joins the small set of massive planets ($>$80 M$_E$) found around mid to late M dwarfs ($<$0.4 R$_\odot$), providing both an interesting challenge to planet formation theory and a favourable target for further atmospheric studies with transmission spectroscopy. We identified an additional signal in the radial velocity data that we attribute to an eccentric planet candidate ($e=0.66\pm0.09$) with an orbital period of $427\pm7$~days and a minimum mass of $1.66\pm 0.26$ M$_J$, but additional data would be needed to confirm this.

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J. M. Almenara, X. Bonfils, E. M. Bryant, A. Jordán, G. Hébrard, E. Martioli, A. C. M. Correia, N. Astudillo-Defru, C. Cadieux, L. Arnold, É. Artigau, G. Á. Bakos, S. C. C. Barros, D. Bayliss, F. Bouchy, G. Boué, R. Brahm, A. Carmona, D. Charbonneau, D. R. Ciardi, R. Cloutier, M. Cointepas, N. J. Cook, N. B. Cowan, X. Delfosse, J. Dias do Nascimento, J. -F. Donati, R. Doyon, T. Forveille, P. Fouqué, E. Gaidos, E. A. Gilbert, J. Gomes da Silva, J. D. Hartman, K. Hesse, M. J. Hobson, J. M. Jenkins, F. Kiefer, V. B. Kostov, J. Laskar, M. Lendl, A. L'Heureux, J. H. C. Martins, K. Menou, C. Moutou, F. Murgas, A. S. Polanski, D. Rapetti, E. Sedaghati, H. Shang. 2023-08-02. TOI-4860 b, a short-period giant planet transiting an M3.5 dwarf. https://arxiv.org/abs/2308.01454

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