Journal ArticleTOI-3785 b: A Low-density Neptune Orbiting an M2-dwarf StarPowers, Luke C.; Libby-Roberts, Jessica; Lin, Andrea S.; Cañas, Caleb I.; Kanodia, Shubham; Mahadevan, Suvrath; Ninan, Joe P.; Stefánsson, Guđmundur; Gupta, Arvind F.; Jones, Sinclaire; Kobulnicky, Henry A.; Monson, Andrew; Parker, Brock A.; Swaby, Tera N.; Bender, Chad F.; Cochran, William D.; Hebb, Leslie; Metcalf, Andrew J.; Robertson, Paul; Schwab, Christian; Wisniewski, John; Wright, Jason T.Abstract Using both ground-based transit photometry and high-precision radial velocity spectroscopy, we confirm the planetary nature of TOI-3785 b. This transiting Neptune orbits an M2-Dwarf star with a period of ∼4.67 days, a planetary radius of 5.14 ± 0.16 R ⊕ , a mass of 14.95 − 3.92 + 4.10 M ⊕ , and a density of ρ = 0.61 − 0.17 + 0.18 g cm −3 . TOI-3785 b belongs to a rare population of Neptunes (4 R ⊕ < R p < 7 R ⊕ ) orbiting cooler, smaller M-dwarf host stars, of which only ∼10 have been confirmed. By increasing the number of confirmed planets, TOI-3785 b offers an opportunity to compare similar planets across varying planetary and stellar parameter spaces. Moreover, with a high-transmission spectroscopy metric of ∼150 combined with a relatively cool equilibrium temperature of T eq = 582 ± 16 K and an inactive host star, TOI-3785 b is one of the more promising low-density M-dwarf Neptune targets for atmospheric follow up. Future investigation into atmospheric mass-loss rates of TOI-3785 b may yield new insights into the atmospheric evolution of these low-mass gas planets around M dwarfs.2023-07-0410435508The Astronomical Journal1662440004-6256https://doi.org/10.3847/1538-3881/acd8bf2108493; 1910954; 2108801; 2108512National Science Foundation