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.; Albrecht, Simon H.; Hirano, Teruyuki; Kochukhov, Oleg; Astudillo-Defru, Nicola; Barragan, Oscar; Serrano, Luisa M.; Hatzes, Artie P.; Alibert, Yann; Guenther, Eike; Dai, Fei; Lam, Kristine W. F.; Csizmadia, Szilárd; Smith, Alexis M. S.; Fossati, Luca; Luque, Rafael; Rodler, Florian; Winther, Mark L.; Rørsted, Jakob L.; Alarcon, Javier; Bonfils, Xavier; Cochran, William D.; Deeg, Hans J.; Jenkins, Jon M.; Korth, Judith; Livingston, John H.; Meech, Annabella; Murgas, Felipe; Orell-Miquel, Jaume; Osborne, Hannah L. M.; Palle, Enric; Persson, Carina M.; Redfield, Seth; Ricker, George R.; Seager, Sara; Vanderspek, Roland; Van Eylen, Vincent; Winn, Joshua N.
Bibliographical reference

The Astrophysical Journal

Advertised on:
9
2023
Number of authors
41
IAC number of authors
4
Citations
1
Refereed citations
1
Description
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 ${M}_{{\rm{c}}}\sin {i}_{{\rm{c}}}$ = 4.13 ± 0.36 M ⊕ and ${M}_{{\rm{d}}}\sin {i}_{{\rm{d}}}$ = 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. *Based on observations made with the ESO-3.6 m telescope at La Silla Observatory under programs 1102.C-0923 and 106.21TJ.001.
Related projects
Helio and Asteroseismology
Helio and Astero-Seismology and Exoplanets Search

The principal objectives of this project are: 1) to study the structure and dynamics of the solar interior, 2) to extend this study to other stars, 3) to search for extrasolar planets using photometric methods (primarily by transits of their host stars) and their characterization (using radial velocity information) and 4) the study of the planetary

Savita
Mathur
Projects' name image
Exoplanets and Astrobiology

The search for life in the universe has been driven by recent discoveries of planets around other stars (known as exoplanets), becoming one of the most active fields in modern astrophysics. The growing number of new exoplanets discovered in recent years and the recent advance on the study of their atmospheres are not only providing new valuable

Enric
Pallé Bago