The TOI-2427 system: Two close-in planets orbiting a late K-dwarf star
Journal article, 2025
Using high-precision photometry, NASA’s TESS space mission has discovered many intriguing transiting planet candidates. These discoveries require ground-based follow-up observations, including high-precision Doppler spectroscopy, to rule out false positive scenarios and measure the mass of the transiting planets. In this study, we present an intensive Doppler follow-up campaign of the TESS object of interest TOI-2427, carried out with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph to determine the mass of the previously validated transiting planet (TOI-2427 b) and search for additional orbiting companions. By analyzing TESS transit photometry alongside our HARPS radial velocity measurements, we spectroscopically confirmed the transiting planet TOI-2427 b, which orbits its host star every ~1.3 d. We also discovered the presence of a second non-transiting planetary companion with an orbital period of ~5.15 d, which is very close to four times the orbital period of the inner transiting planet. We found that TOI-2427 b is a short-period, high-density super-Earth with a mass of Mb = 5.69+−005150 Mand a radius of Rb = 1.64+−001211 R, implying a mean density of b = 7.1+−1184 g cm−3. Its interior seems to be composed of a predominantly iron core and a silicate mantle and crust. Despite its high density, it is unlikely that TOI-2427 b can sustain any atmosphere composed of lighter gases; however, it could still retain heavier gases. The outer non-transiting planet TOI-2427 c has a minimum mass of Mc sin ic = 6.46+−007978 M. Assuming that TOI-2427 b and c are coplanar, a statistical analysis suggests that planets with a mass of ~6.5 M tend to have radii around 2.7+−1018 R. This would place TOI-2457 c near the sub-Neptune regime, while also leaving open the possibility of it being a super-Earth.
techniques: radial velocities
planets and satellites: atmospheres
planets and satellites: detection
instrumentation: photometers
planets and satellites: interiors
Author
H. Schmerling
University of Cologne
E. Goffo
Thüringer Landessternwarte Tautenburg
University of Turin
S. Grziwa
University of Cologne
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
D. Gandolfi
University of Turin
Martin Pätzold
University of Cologne
A. Hatzes
Thüringer Landessternwarte Tautenburg
Coel Hellier
National Astronomical Observatory of Japan
J.H. Livingston
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
National Institutes of Natural Sciences
L. Acuña
Keele University
Max Planck Society
A. Aguichine
University of California
E. Costanza
University of Turin
H. Deeg
Instituto de Astrofísica de Canarias
University of La Laguna
T. Masseron
University of La Laguna
Instituto de Astrofísica de Canarias
Enric Palle
University of La Laguna
Instituto de Astrofísica de Canarias
William D. Cochran
The University of Texas at Austin
G. Nowak
Instituto de Astrofísica de Canarias
Nicolaus Copernicus University (SGMK)
University of La Laguna
D. Jankowski
Nicolaus Copernicus University (SGMK)
K. Goździewski
Nicolaus Copernicus University (SGMK)
R. Luque
University of Chicago
S. Mathur
Instituto de Astrofísica de Canarias
University of La Laguna
Dinil B. Palakkatharappil
University Paris-Saclay
R. A. García
University Paris-Saclay
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 699 A185Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
Meteorology and Atmospheric Sciences
Subatomic Physics
DOI
10.1051/0004-6361/202452620