2019AJ....157...93T -
Astron. J., 157, 93-93 (2019/March-0)
Two jovian planets around the giant star HD 202696: a growing population of packed massive planetary pairs around massive stars?
TRIFONOV T., STOCK S., HENNING T., REFFERT S., KURSTER M., LEE M.H., BITSCH B., BUTLER R.P. and VOGT S.S.
Abstract (from CDS):
We present evidence for a new two-planet system around the giant star HD 202696 (=HIP 105056, BD +26 4118). The discovery is based on public HIRES radial velocity (RV) measurements taken at Keck Observatory between 2007 July and 2014 September. We estimate a stellar mass of 1.91–0.14+0.09M☉ for HD 202696, which is located close to the base of the red giant branch. A two-planet self-consistent dynamical modeling MCMC scheme of the RV data followed by a long-term stability test suggests planetary orbital periods of Pb = 517.8–3.9+8.9 and Pc = 946.6–20.9+20.7 days, eccentricities of eb = 0.011–0.011+0.078 and ec = 0.028–0.012+0.065, and minimum dynamical masses of mb = 2.00–0.10+0.22 and mc = 1.86–0.23+0.18MJup, respectively. Our stable MCMC samples are consistent with orbital configurations predominantly in a mean period ratio of 11:6 and its close-by high-order mean-motion commensurabilities with low eccentricities. For the majority of the stable configurations, we find an aligned or anti-aligned apsidal libration (i.e., Δω librating around 0° or 180°), suggesting that the HD 202696 system is likely dominated by secular perturbations near the high-order 11:6 mean-motion resonance. The HD 202696 system is yet another Jovian-mass pair around an intermediate-mass star with a period ratio below the 2:1 mean-motion resonance. Therefore, the HD 202696 system is an important discovery that may shed light on the primordial disk-planet properties needed for giant planets to break the strong 2:1 mean-motion resonance and settle in more compact orbits.
Abstract Copyright:
© 2019. The American Astronomical Society. All rights reserved.
Journal keyword(s):
planetary systems - planets and satellites: detection - planets and satellites: dynamical evolution and stability - techniques: radial velocities
Simbad objects:
11
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