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
A. P. Hatzes, D. Gandolfi, J. Korth, F. Rodler, S. Sabotta, M. Esposito, Oscar Barragán, Vincent Van Eylen, John H. Livingston, L. M. Serrano, R. Luque, A. M. S. Smith, Seth Redfield, C. M. Persson, M. Pätzold, Ε. Πάλλη, G. Nowak, H. L. M. Osborne, Norio Narita, S. Mathur, K. W. F. Lam, P. Kábath, Marshall C. Johnson, E. W. Guenther, S. Grziwa, Elisa Goffo, Malcolm Fridlund, Michael Endl, H. J. Deeg, Szilárd Csizmadia, William D. Cochran, L. González-Cuesta, P. Chaturvedi, I. Carleo, J. Cabrera, P. G. Beck, Simon Albrecht
Abstract
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.