Searching for GEMS: Confirmation of TOI-5573 b, a Cool, Saturn-like Planet Orbiting an M Dwarf

  • Rachel B. Fernandes
  • , Shubham Kanodia
  • , Megan Delamer
  • , Andrew Hotnisky
  • , Te Han
  • , Caleb I. Cañas
  • , Jessica Libby-Roberts
  • , Varghese Reji
  • , Arvind F. Gupta
  • , Jaime A. Alvarado-Montes
  • , Chad F. Bender
  • , Cullen H. Blake
  • , William D. Cochran
  • , Zoë L. de Beurs
  • , Scott A. Diddams
  • , Jiayin Dong
  • , Mark E. Everett
  • , Eric B. Ford
  • , Samuel Halverson
  • , Jesus Higuera
  • Henry A. Kobulnicky, Daniel M. Krolikowski, Alexander Larsen, Andrea S.J. Lin, Suvrath Mahadevan, Michael W. McElwain, Andrew Monson, Joe P. Ninan, Leonardo A. Paredes, Yatrik G. Patel, Paul Robertson, Gabrielle Ross, Arpita Roy, Christian Schwab, Gudmundur Stefansson, Daniel J. Stevens, Andrew M. Vanderburg, Jason Wright

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We present the confirmation of TOI-5573 b, a Saturn-sized exoplanet on an 8.79 days orbit around an early M dwarf (3790 K, 0.59 R, 0.61 M, 12.30 Jmag). TOI-5573 b has a mass of 11 2 − 19 + 18 M(0.35 ± 0.06 MJup) and a radius of 9.75 ± 0.47 R(0.87 ± 0.04 RJup), resulting in a density of 0.6 6 − 0.13 + 0.16 g cm−3, akin to that of Saturn. The planet was initially discovered by the Transiting Exoplanet Survey Satellite (TESS) and confirmed using a combination of 11 transits from four TESS Sectors (20, 21, 47, and 74), ground-based photometry from the Red Buttes Observatory, and high-precision radial velocity data from the Habitable-zone Planet Finder and NN-EXPLORE Exoplanet Investigations with Doppler spectrographs, achieving a 5σ precision on the planet’s mass. TOI-5573 b is one of the coolest Saturn-like exoplanets discovered around an M-dwarf, with an equilibrium temperature of only 528 ± 10 K, making it a valuable target for atmospheric characterization. Saturn-like exoplanets around M dwarfs likely form through core accretion, with increased disk opacity slowing gas accretion and limiting their mass. The host star’s supersolar metallicity supports core accretion, but uncertainties in M-dwarf metallicity estimates complicate definitive conclusions. Compared to other GEMS (Giant Exoplanets around M-dwarf Stars) orbiting metal-rich stars, TOI-5573 b aligns with the observed pattern that giant planets preferentially form around M-dwarfs with supersolar metallicity. Further high-resolution spectroscopic observations are needed to explore the role of stellar metallicity in shaping the formation and properties of giant exoplanets like TOI-5573 b.

Original languageEnglish (US)
Article number55
JournalAstronomical Journal
Volume170
Issue number1
DOIs
StatePublished - Jul 1 2025

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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