The Astronomical Journal (Jan 2024)

The TESS-Keck Survey. XII. A Dense 1.8 R ⊕ Ultra-short-period Planet Possibly Clinging to a High-mean-molecular-weight Atmosphere after the First Gigayear

  • Ryan A. Rubenzahl,
  • Fei Dai,
  • Andrew W. Howard,
  • Jack J. Lissauer,
  • Judah Van Zandt,
  • Corey Beard,
  • Steven Giacalone,
  • Joseph M. Akana Murphy,
  • Ashley Chontos,
  • Jack Lubin,
  • Casey L. Brinkman,
  • Dakotah Tyler,
  • Mason G. MacDougall,
  • Malena Rice,
  • Paul A. Dalba,
  • Andrew W. Mayo,
  • Lauren M. Weiss,
  • Alex S. Polanski,
  • Sarah Blunt,
  • Samuel W. Yee,
  • Michelle L. Hill,
  • Isabel Angelo,
  • Emma V. Turtelboom,
  • Rae Holcomb,
  • Aida Behmard,
  • Daria Pidhorodetska,
  • Natalie M. Batalha,
  • Ian J. M. Crossfield,
  • Courtney Dressing,
  • Benjamin Fulton,
  • Daniel Huber,
  • Howard Isaacson,
  • Stephen R. Kane,
  • Erik A. Petigura,
  • Paul Robertson,
  • Nicholas Scarsdale,
  • Teo Mocnik,
  • Tara Fetherolf,
  • Luca Malavolta,
  • Annelies Mortier,
  • Aldo Fiorenzano,
  • Marco Pedani

DOI
https://doi.org/10.3847/1538-3881/ad28bb
Journal volume & issue
Vol. 167, no. 4
p. 153

Abstract

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The extreme environments of ultra-short-period planets (USPs) make excellent laboratories to study how exoplanets obtain, lose, retain, and/or regain gaseous atmospheres. We present the confirmation and characterization of the USP TOI-1347 b, a 1.8 ± 0.1 R _⊕ planet on a 0.85 day orbit that was detected with photometry from the TESS mission. We measured radial velocities of the TOI-1347 system using Keck/HIRES and HARPS-N and found the USP to be unusually massive at 11.1 ± 1.2 M _⊕ . The measured mass and radius of TOI-1347 b imply an Earth-like bulk composition. A thin H/He envelope (>0.01% by mass) can be ruled out at high confidence. The system is between 1 and 1.8 Gyr old; therefore, intensive photoevaporation should have concluded. We detected a tentative phase-curve variation (3 σ ) and a secondary eclipse (2 σ ) in TESS photometry, which, if confirmed, could indicate the presence of a high-mean-molecular-weight atmosphere. We recommend additional optical and infrared observations to confirm the presence of an atmosphere and investigate its composition.

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