Eccentric loners, or resonant couples?

The figure shows an example of RV exoplanet systems currently having a single-planet status. The available RV data can be modeled well with a single eccentric planet but is much better fitted with two planets close to the 2:1 MMR, which is a major exoplanet bias (e.g., Kürster et al. 2015). Indeed, many RV exoplanet discoveries have been announced based on sparse RV data samples, insufficient precision, and sometimes incomplete phase coverage. 

We aim to disentangle the two competing models using follow-up observations and N-body dynamical modeling tests (Trifonov et al. 2017).