Volume 631, November 2019
|Number of page(s)||8|
|Section||Planets and planetary systems|
|Published online||06 November 2019|
Precise radial velocities of giant stars
Instituto de Astrofísica de Canarias (IAC),
38205 La Laguna,
2 Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
3 Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
4 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
5 Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong
6 Department of Physics, The University of Hong Kong, Pokfulman Road, Hong Kong
7 Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
8 Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109, Australia
Accepted: 8 October 2019
We report the discovery of a second planet orbiting the K giant star 7 CMa based on 166 high-precision radial velocities obtained with Lick, HARPS, UCLES, and SONG. The periodogram analysis reveals two periodic signals of approximately 745 and 980 d, associated with planetary companions. A double-Keplerian orbital fit of the data reveals two Jupiter-like planets with minimum masses mb sini ~ 1.9 MJ and mc sini ~ 0.9 MJ, orbiting at semimajor axes of ab ~ 1.75 au and ac ~ 2.15 au, respectively. Given the small orbital separation and the large minimum masses of the planets, close encounters may occur within the time baseline of the observations; thus, a more accurate N-body dynamical modeling of the available data is performed. The dynamical best-fit solution leads to collision of the planets and we explore the long-term stable configuration of the system in a Bayesian framework, confirming that 13% of the posterior samples are stable for at least 10 Myr. The result from the stability analysis indicates that the two planets are trapped in a low-eccentricity 4:3 mean motion resonance. This is only the third discovered system to be inside a 4:3 resonance, making this discovery very valuable for planet formation and orbital evolution models.
Key words: techniques: radial velocities / planetary systems / planets and satellites: dynamical evolution and stability / planets and satellites: detection
RV data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/631/A136
© ESO 2019
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