A Cold and Superpuffy Planet on a Prograde Orbit

Journal article

We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density <0.2 g cm−3 on a 105 days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M⊕ at 95% confidence. The radial velocities also exhibit the Rossiter–McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity λ=−15−44+50 ° (∣λ∣ < 80° at 3σ). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest “superpuff” planets yet discovered.

Authors: Espinoza-Retamal, JI; Brahm, R; Petrovich, C; Jordán, A; Henning, T

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal Letters
• Volume: 996
• Issue: 1
• Article number: L13
• Publication date: 2025-12-30
• Acceptance date: 2025-12-08
• DOI: 10.3847/2041-8213/ae2bfa
• EISSN: 2041-8213
• ISSN: 2041-8205
• Language: English
• Keywords: Exoplanets; Cold Neptunes; Radial velocity; Transit photometry