Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

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

Goffo, Elisa ; Gandolfi, Davide ; Egger, Jo Ann ; Mustill, Alexander J. LU orcid ; Albrecht, Simon H. ; Hirano, Teruyuki ; Kochukhov, Oleg ; Astudillo-Defru, Nicola ; Barragan, Oscar and Serrano, Luisa M. , et al. (2023) In Astrophysical Journal Letters 955(1).
Abstract
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,... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
; ; ; ; ; ; ; ; and , et al. (More)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; and (Less)
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Exoplanet detection methods, Exoplanet systems, Exoplanets, Extrasolar rocky planets, Astrophysics - Earth and Planetary Astrophysics
in
Astrophysical Journal Letters
volume
955
issue
1
article number
L3
publisher
IOP Publishing
external identifiers
  • scopus:85173121663
ISSN
2041-8213
DOI
10.3847/2041-8213/ace0c7
project
A unified picture of white dwarf planetary systems
Consolidating CHEOPS and preparing for PLATO: Exoplanet studies in the 2020s
language
English
LU publication?
yes
id
19d97945-59b3-4527-81e7-41ab84620d86
date added to LUP
2023-12-13 15:45:17
date last changed
2024-01-12 11:07:20
@article{19d97945-59b3-4527-81e7-41ab84620d86,
  abstract     = {{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<sub> ⊕</sub> and a radius of R b = 0.699 ± 0.024 R<sub> ⊕</sub>, 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 <sub>⊕</sub> and M d sin i d = 6.03 ± 0.49 M <sub>⊕</sub>, 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       = {{Goffo, Elisa and Gandolfi, Davide and Egger, Jo Ann and Mustill, Alexander J. and Albrecht, Simon H. and Hirano, Teruyuki and Kochukhov, Oleg and Astudillo-Defru, Nicola and Barragan, Oscar and Serrano, Luisa M. and Hatzes, Artie P. and Alibert, Yann and Guenther, Eike and Dai, Fei and Lam, Kristine W.~F. and Csizmadia, Szilárd and Smith, Alexis M.~S. and Fossati, Luca and Luque, Rafael and Rodler, Florian and Winther, Mark L. and Rørsted, Jakob L. and Alarcon, Javier and Bonfils, Xavier and Cochran, William D. and Deeg, Hans J. and Jenkins, Jon M. and Korth, Judith and Livingston, John H. and Meech, Annabella and Murgas, Felipe and Orell-Miquel, Jaume and Osborne, Hannah L.~M. and Palle, Enric and Persson, Carina M. and Redfield, Seth and Ricker, George R. and Seager, Sara and Vanderspek, Roland and Van Eylen, Vincent and Winn, Joshua N.}},
  issn         = {{2041-8213}},
  keywords     = {{Exoplanet detection methods; Exoplanet systems; Exoplanets; Extrasolar rocky planets; Astrophysics - Earth and Planetary Astrophysics}},
  language     = {{eng}},
  month        = {{09}},
  number       = {{1}},
  publisher    = {{IOP Publishing}},
  series       = {{Astrophysical Journal Letters}},
  title        = {{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}},
  url          = {{http://dx.doi.org/10.3847/2041-8213/ace0c7}},
  doi          = {{10.3847/2041-8213/ace0c7}},
  volume       = {{955}},
  year         = {{2023}},
}