A Massive Hot Jupiter Orbiting a Metal-rich Early M Star Discovered in the TESS Full-frame Images

Gan, Tianjun; Cadieux, Charles; Jahandar, Farbod; Vazan, Allona; Wang, Sharon X.; Mao, Shude; Alvarado-Montes, Jaime A.; Lin, D. N. C.; Artigau, Étienne; Cook, Neil J.; Doyon, René; Mann, Andrew W.; Stassun, Keivan G.; Burgasser, Adam J.; Rackham, Benjamin V.; Howell, Steve B.; Collins, Karen A.; Barkaoui, Khalid; Shporer, Avi; de Leon, Jerome; Arnold, Luc; Ricker, George R.; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Burdanov, Artem; Charbonneau, David; Dransfield, Georgina; Fukui, Akihiko; Furlan, Elise; Gillon, Michaël; Hooton, Matthew J.; Lewis, Hannah M.; Littlefield, Colin; Mireles, Ismael; Narita, Norio; Ormel, Chris W.; Quinn, Samuel N.; Sefako, Ramotholo; Timmermans, Mathilde; Vezie, Michael; de Wit, Julien
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The Astronomical Journal

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Observations and statistical studies have shown that giant planets are rare around M dwarfs compared with Sun-like stars. The formation mechanism of these extreme systems has remained under debate for decades. With the help of the TESS mission and ground-based follow-up observations, we report the discovery of TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so far with a radius of 1.22 ± 0.04 R J and a mass of 2.48 ± 0.09 M J, about 5 times heavier than most other giant planets around M dwarfs. It also has the highest planet-to-star mass ratio (q ~ 4 × 10-3) among such systems. The host star is an early M dwarf with a mass of 0.61 ± 0.02 M ⊙ and a radius of 0.63 ± 0.02 R ⊙. It has significant supersolar iron abundance ([Fe/H] = 0.52 ± 0.08 dex). However, interior structure modeling suggests that its planet TOI-4201b is metal-poor, which challenges the classical core-accretion correlation of stellar-planet metallicity, unless the planet is inflated by additional energy sources. Building on the detection of this planet, we compare the stellar metallicity distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We find that hot/warm Jupiters show a similar metallicity dependence around G-type stars. For M-dwarf host stars, the occurrence of hot Jupiters shows a much stronger correlation with iron abundance, while warm Jupiters display a weaker preference, indicating possible different formation histories.