TOI-1685 b Is a Hot Rocky Super-Earth

Author(s): Jennifer A. Burt, Matthew J. Hooton, Eric E. Mamajek, Oscar Barragán, Sarah C. Millholland, Tyler R. Fairnington, Chloe Fisher, Samuel P. Halverson, Chelsea X. Huang, Madison Brady, Andreas Seifahrt, Eric Gaidos, Rafael Luque, David Kasper, Jacob L. Bean
Abstract: We present an updated characterization of the TOI-1685 planetary system, which consists of a P _b = 0.69 day ultra-short-period super-Earth planet orbiting a nearby (d = 37.6 pc) M2.5V star (TIC 28900646, 2MASS J04342248+4302148). This planet was previously featured in two contemporaneous discovery papers, but the best-fit planet mass, radius, and bulk density values were discrepant, allowing it to be interpreted either as a hot, bare rock or a 50% H₂O/50% MgSiO₃ water world. TOI-1685 b will be observed in three independent JWST Cycle 2 programs, two of which assume the planet is a water world, while the third assumes that it is a hot rocky planet. Here we include a refined stellar classification with a focus on addressing the host star’s metallicity, an updated planet radius measurement that includes two sectors of TESS data and multicolor photometry from a variety of ground-based facilities, and a more accurate dynamical mass measurement from a combined CARMENES, InfraRed Doppler, and MAROON-X radial velocity data set. We find that the star is very metal-rich ([Fe/H] ≃ +0.3) and that the planet is systematically smaller, lower mass, and higher density than initially reported, with new best-fit parameters of R _pl = 1.468 − 0.051 + 0.050 R _⊕ and M _pl = 3.03 − 0.32 + 0.33 M _⊕. These results fall in between the previously derived values and suggest that TOI-1685 b is a hot rocky planet with an Earth-like density (ρ _pl = 5.3 ± 0.8 g cm⁻³, or 0.96 ρ _⊕), high equilibrium temperature (T _eq = 1062 ± 27 K), and negligible volatiles, rather than a water world.
Organisation(s): Department of Astrophysics
External organisation(s): California Institute of Technology (Caltech), University of Cambridge, University of Oxford, Massachusetts Institute of Technology, University of Southern Queensland, University of Chicago, University of Hawaii at Manoa
Journal: Astrophysical Journal Letters
Volume: 971
No. of pages: 21
ISSN: 2041-8205
DOI: https://doi.org/10.3847/2041-8213/ad5b52
Publication date: 08-2024
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/fa9cac39-2e2a-40a6-8e1d-d2a7d5a50c05

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