TOI-1173 A b: The First Inflated Super-Neptune in a Wide Binary System

Galarza J.Y.; Ferreira T.; Lorenzo-Oliveira D.; Simon J.D.; Reggiani H.; Piro A.L.; Butler R.P.; Netto Y.; Valio A.; Ciardi D.R.; Safonov B.

TOI-1173 A b: The First Inflated Super-Neptune in a Wide Binary System

Tipo

Artigo

Data de publicação

2024

Periódico

Astronomical Journal

Citações (Scopus)

1

Autores

Galarza J.Y.
Ferreira T.
Lorenzo-Oliveira D.
Simon J.D.
Reggiani H.
Piro A.L.
Butler R.P.
Netto Y.
Valio A.
Ciardi D.R.
Safonov B.

Resumo

© 2024. The Author(s). Published by the American Astronomical Society.Among Neptunian mass exoplanets (20−50 M ⊕), puffy hot Neptunes are extremely rare, and their unique combination of low mass and extended radii implies very low density (ρ < 0.3 g cm−3). Over the last decade, only a few puffy planets have been detected and precisely characterized with both transit and radial velocity observations, most notably including WASP-107 b, TOI-1420 b, and WASP-193 b. In this paper, we report the discovery of TOI-1173 A b, a low-density ( ρ = 0.195 − 0.017 + 0.018 g cm−3) super-Neptune with P = 7.06 days in a nearly circular orbit around the primary G-dwarf star in the wide binary system TOI-1173 A/B. Using radial velocity observations with the MAROON-X and HIRES spectrographs and transit photometry from TESS, we determine a planet mass of M p = 27.4 ± 1.7 M ⊕ and radius of R p = 9.19 ± 0.18 R ⊕. TOI-1173 A b is the first puffy super-Neptune planet detected in a wide binary system (projected separation ∼11,400 au). We explore several mechanisms to understand the puffy nature of TOI-1173 A b and show that tidal heating is the most promising explanation. Furthermore, we demonstrate that TOI-1173 A b likely has maintained its orbital stability over time and may have undergone von-Zeipel-Lidov-Kozai migration followed by tidal circularization, given its present-day architecture, with important implications for planet migration theory and induced engulfment into the host star. Further investigation of the atmosphere of TOI-1173 A b will shed light on the origin of close-in low-density Neptunian planets in field and binary systems, while spin-orbit analyses may elucidate the dynamical evolution of the system.