TOI-2458 b: A mini-Neptune consistent with in situ hot Jupiter formation
Journal article, 2025
We report on the discovery and spectroscopic confirmation of TOI-2458 b, a transiting mini-Neptune around an F-type star leaving the main-sequence with a mass of M∗ = 1.05 ± 0.03 M⊙, a radius of R∗ = 1.31 ± 0.03 R⊙, an effective temperature of Teff = 6005 ± 50 K, and a metallicity of 0.10 ± 0.05 dex. By combining TESS photometry with high-resolution spectra acquired with the HARPS spectrograph, we found that the transiting planet has an orbital period of 3.74 days, a mass of Mp = 13.31 ± 0.99 M⊕ and a radius of Rp = 2.83 ± 0.20 R⊕. The host star TOI-2458 shows a short activity cycle of ∼54 days revealed in the HARPS S-index and Ha times series. We took the opportunity to investigate other F stars showing activity cycle periods comparable to that of TOI-2458 and found that they have shorter rotation periods than would be expected based on the gyrochronology predictions. In addition, we determined TOI-2458's stellar inclination angle to be i∗ = 10.610.6+13.3 degrees. We discuss that both phenomena (fast stellar rotation and planet orbit inclination) could be explained by in situ formation of a hot Jupiter interior to TOI-2458 b. It is plausible that this hot Jupiter was recently engulfed by the star. Analysis of HARPS spectra has identified the presence of another planet with a period of P = 16.55 ± 0.06 days and a minimum mass of Mp sin i = 10.22 ± 1.90 M⊕. Using dynamical stability analysis, we constrained the mass of this planet to the range Mc ≃ (10, 25) M⊕
Techniques: photometric
Planetary systems
Techniques: spectroscopic
Planets and satellites: dynamical evolution and stability
Planets and satellites: formation
Techniques: radial velocities
Author
J. Šubjak
Czech Academy of Sciences
Harvard-Smithsonian Center for Astrophysics
D. Gandolfi
University of Turin
E. Goffo
Thüringer Landessternwarte Tautenburg
University of Turin
D. Rapetti
Universities Space Research Association
NASA Ames Research Center
Dawid Jankowski
Nicolaus Copernicus University
Toshiyuki Mizuki
National Astronomical Observatory of Japan
National Institutes of Natural Sciences
Fei Dai
University of Hawaii
L. M. Serrano
University of Turin
T.G. Wilson
The University of Warwick
Krzysztof Goåºdziewski
Nicolaus Copernicus University
G. Nowak
Nicolaus Copernicus University
Jon M. Jenkins
NASA Ames Research Center
J. D. Twicken
SETI Institute
NASA Ames Research Center
J. N. Winn
Princeton University
Allyson Bieryla
Harvard-Smithsonian Center for Astrophysics
D. R. Ciardi
National Aeronautics and Space Administration (NASA)
William Cochran
The University of Texas at Austin
College of Natural Sciences
Karen A. Collins
Harvard-Smithsonian Center for Astrophysics
H. Deeg
Instituto de Astrofísica de Canarias
University of La Laguna
R. A. García
University Paris-Saclay
E. W. Guenther
Thüringer Landessternwarte Tautenburg
A. Hatzes
Thüringer Landessternwarte Tautenburg
Petr Kabath
Czech Academy of Sciences
Judith Korth
Lund University
D. W. Latham
Harvard-Smithsonian Center for Astrophysics
J.H. Livingston
National Institutes of Natural Sciences
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
M. B. Lund
National Aeronautics and Space Administration (NASA)
S. Mathur
Instituto de Astrofísica de Canarias
University of La Laguna
Norio Narita
Instituto de Astrofísica de Canarias
University of Tokyo
National Institutes of Natural Sciences
J. Orell-Miquel
University of La Laguna
Instituto de Astrofísica de Canarias
Enric Palle
University of La Laguna
Instituto de Astrofísica de Canarias
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
S. Redfield
Wesleyan University
R. Schwarz
Harvard-Smithsonian Center for Astrophysics
David Watanabe
Planetary Discoveries
C. Ziegler
Stephen F. Austin State University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 693 A235Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)
Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.
Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.
Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202451057
Related datasets
TOI-2458 b: A mini-Neptune consistent with in situ hot Jupiter formation (Additional material) [dataset]
URI: https://zenodo.org/records/14362145