Precise radial velocities of giant stars XIII. A second Jupiter orbiting in 4:3 resonance in the 7 CMa system

Abstract

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 to planetary companions. A double-Keplerian orbital fit of the data reveals two Jupiter-like planets with minimum masses $m_b\sin i\sim 1.9{\mathrm{M}}_{\mathrm{J}}$ and $m_c\sin i\sim 0.9{\mathrm{M}}_{\mathrm{J}}$, orbiting at semi-major axes of $a_b\sim 1.75\mathrm{au}$ and $a_c\sim 2.15\mathrm{au}$, 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 it very valuable for planet formation and orbital evolution models.

Accepted in A&A

References in corpus (16)

• Astrophysics Source Code Library
• Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Southern Sample
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Precise Radial Velocities of Giant Stars VII. Occurrence Rate of Giant Extrasolar Planets as a Function of Mass and Metallicity
• Precise radial velocities of giant stars. III. Spectroscopic stellar parameters
• First Results From The Hertzsprung Song Telescope: Asteroseismology Of The G5 Subgiant Star {\Mu}Her
• Precise radial velocities of giant stars: I. Stable stars
• Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties
• Newly-Discovered Planets Orbiting HD~5319, HD~11506, HD~75784 and HD~10442 from the N2K Consortium
• Traditional formation scenarios fail to explain 4:3 mean motion resonances
• Formation and evolution of the two 4/3 resonant giants planets in HD 200946
• Disentangling 2:1 resonant radial velocity orbits from eccentric ones and a case study for HD 27894
• Precise radial velocities of giant stars VI. A possible 2:1 resonant planet pair around the K giant star $\eta$ Cet
• Truly eccentric. II. When can two circular planets mimic a single eccentric orbit?
• Two Jovian planets around the giant star HD202696. A growing population of packed massive planetary pairs around massive stars?
• Precise radial velocities of giant stars. XI. Two brown dwarfs in 6:1 mean motion resonance around the K giant star $\nu$ Ophiuchi

Cited by in corpus (1)

• Modeling Radial Velocity Data of Resonant Planets to Infer Migration Histories