Company for the Ultra-high Density, Ultra-short Period Sub-Earth GJ 367 b: Discovery of Two Additional Low-mass Planets at 11.5 and 34 Days
Journal article, 2023
GJ 367 is a bright (V ≈ 10.2) M1 V star that has been recently found to host a transiting ultra-short period sub-Earth on a 7.7 hr orbit. With the aim of improving the planetary mass and radius and unveiling the inner architecture of the system, we performed an intensive radial velocity follow-up campaign with the HARPS spectrograph—collecting 371 high-precision measurements over a baseline of nearly 3 yr—and combined our Doppler measurements with new TESS observations from sectors 35 and 36. We found that GJ 367 b has a mass of M b = 0.633 ± 0.050 M ⊕ and a radius of R b = 0.699 ± 0.024 R ⊕, corresponding to precisions of 8% and 3.4%, respectively. This implies a planetary bulk density of ρ b = 10.2 ± 1.3 g cm−3, i.e., 85% higher than Earth’s density. We revealed the presence of two additional non-transiting low-mass companions with orbital periods of ∼11.5 and 34 days and minimum masses of M c sin i c = 4.13 ± 0.36 M ⊕ and M d sin i d = 6.03 ± 0.49 M ⊕, respectively, which lie close to the 3:1 mean motion commensurability. GJ 367 b joins the small class of high-density planets, namely the class of super-Mercuries, being the densest ultra-short period small planet known to date. Thanks to our precise mass and radius estimates, we explored the potential internal composition and structure of GJ 367 b, and found that it is expected to have an iron core with a mass fraction of 0.91 − 0.23 + 0.07 . How this iron core is formed and how such a high density is reached is still not clear, and we discuss the possible pathways of formation of such a small ultra-dense planet.
Author
E. Goffo
University of Turin
Thüringer Landessternwarte Tautenburg
D. Gandolfi
University of Turin
J. A. Egger
University of Bern
A. J. Mustill
Lund University
Simon Albrecht
Aarhus University
T. Hirano
National Astronomical Observatory of Japan
National Institutes of Natural Sciences
Oleg Kochukhov
Uppsala University
N. Astudillo-Defru
Universidad Catolica de la Santisima Concepcion
O. Barragán
University of Oxford
L. M. Serrano
University of Turin
A. Hatzes
Thüringer Landessternwarte Tautenburg
Y. Alibert
University of Bern
E. W. Guenther
Thüringer Landessternwarte Tautenburg
F. Dai
California Institute of Technology (Caltech)
K. W.F. Lam
German Aerospace Center (DLR)
Szilárd Csizmadia
German Aerospace Center (DLR)
A. M.S. Smith
German Aerospace Center (DLR)
L. Fossati
Institut fur Weltraumforschung
R. Luque
University of Chicago
F. Rodler
European Southern Observatory Santiago
Mark L. Winther
Aarhus University
Jakob L. Rørsted
Aarhus University
Javier Alarcon
European Southern Observatory Santiago
X. Bonfils
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
William D. Cochran
The University of Texas at Austin
H. Deeg
Instituto de Astrofísica de Canarias
University of La Laguna
Jon M. Jenkins
NASA Ames Research Center
Judith Korth
Lund University
J.H. Livingston
National Astronomical Observatory of Japan
National Institutes of Natural Sciences
The Graduate University for Advanced Studies (SOKENDAI)
Annabella Meech
University of Oxford
F. Murgas
Instituto de Astrofísica de Canarias
University of La Laguna
J. Orell-Miquel
University of La Laguna
Instituto de Astrofísica de Canarias
H. L.M. Osborne
University College London (UCL)
Enric Palle
Instituto de Astrofísica de Canarias
University of La Laguna
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
S. Redfield
Wesleyan University
George R. Ricker
Massachusetts Institute of Technology (MIT)
S. Seager
Massachusetts Institute of Technology (MIT)
Roland K. Vanderspek
Massachusetts Institute of Technology (MIT)
Vincent Van Eylen
University College London (UCL)
J. N. Winn
Princeton University
Astrophysical Journal Letters
2041-8205 (ISSN) 2041-8213 (eISSN)
Vol. 955 1 L3Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.3847/2041-8213/ace0c7