A Radial Velocity Study of the Planetary System of π Mensae: Improved Planet Parameters for π Mensae c and a Third Planet on a 125 Day Orbit

Journal article

Abstract π Men hosts a transiting planet detected by the Transiting Exoplanet Survey Satellite space mission and an outer planet in a 5.7 yr orbit discovered by radial velocity (RV) surveys. We studied this system using new RV measurements taken with the HARPS spectrograph on ESO’s 3.6 m telescope, as well as archival data. We constrain the stellar RV semiamplitude due to the transiting planet, π Men c, as K c = 1.21 ± 0.12 m s −1 , resulting in a planet mass of M c = 3.63 ± 0.38 M ⊕ . A planet radius of R c = 2.145 ± 0.015 R ⊕ yields a bulk density of ρ c = 2.03 ± 0.22 g cm −3 . The precisely determined density of this planet and the brightness of the host star make π Men c an excellent laboratory for internal structure and atmospheric characterization studies. Our HARPS RV measurements also reveal compelling evidence for a third body, π Men d, with a minimum mass M d sin i d = 13.38 ± 1.35 M ⊕ orbiting with a period of P orb,d = 125 days on an eccentric orbit ( e d = 0.22). A simple dynamical analysis indicates that the orbit of π Men d is stable on timescales of at least 20 Myr. Given the mutual inclination between the outer gaseous giant and the inner rocky planet and the presence of a third body at 125 days, π Men is an important planetary system for dynamical and formation studies.

Authors: Hatzes, AP; Gandolfi, D; Korth, J; Rodler, F; Sabotta, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: The Astronomical Journal
• Volume: 163
• Issue: 5
• Pages: 223-223
• Publication date: 2022-04-20
• DOI: 10.3847/1538-3881/ac5dcb
• EISSN: 1538-3881
• ISSN: 0004-6256
• Language: English
• Keywords: Astrophysics; Astrobiology; Stars; Planetary system; Radial velocity; Astronomy; Orbit (dynamics); Aerospace engineering; Planet; Physics; Exoplanet