TOI-3785 b: A Low-density Neptune Orbiting an M2-dwarf Star

Luke C. Powers, Jessica Libby-Roberts, Andrea S.J. Lin, Caleb I. Cañas, Shubham Kanodia, Suvrath Mahadevan, Joe P. Ninan, Guđmundur Stefánsson, Arvind F. Gupta, Sinclaire Jones, Henry A. Kobulnicky, Andrew Monson, Brock A. Parker, Tera N. Swaby, Chad F. Bender, William D. Cochran, Leslie Hebb, Andrew J. Metcalf, Paul Robertson, Christian SchwabJohn Wisniewski, Jason T. Wright

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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.

Original languageEnglish (US)
Article number44
JournalAstronomical Journal
Issue number2
StatePublished - Aug 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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