A collage of small planets from the Lick Carnegie Exoplanet Survey : Exploring the super-Earth and sub-Neptune mass regime

Analysis of new precision radial velocity measurements from the Lick Automated PlanetFinder and Keck HIRES have yielded the discovery of three new exoplanet candidatesorbiting the nearby stars HD 190007 and HD 216520. We also report new velocitiesfrom the APF and the Planet Finder Spectrograph and updated orbital ts for theknown exoplanet host stars GJ 686 and HD 180617. Of the newly discovered planets,HD 190007 b has a period of P = 11.72 days, an RV semi-amplitude of K = 5.640.55ms􀀀1, a minimum mass of Mpl = 16.461.66 M, and orbits the slightly metal-rich, activeK4V star HD 190007. For HD 216520 b we nd P = 35.45 days, K = 2.280.20 ms􀀀1,and Mpl = 10.260.99 M, while for HD 216520 c, P = 154.43 days, K = 1.290.22 ms􀀀1,and Mpl = 9:44 1:63 M. Both planets orbit the slightly metal-poor, inactive K0V starHD 216520. Our updated best t models for HD 180617 b and GJ 686 b are in goodagreement with the published results. For HD 180617 b we obtain P = 105.91 days andMpl = 12.2141.05 M. For GJ 686 b we nd P = 15.53 days and Mpl = 6.6240.432M. Using an injection-recovery exercise, we nd that HD 190007 b and HD 216520 bare unlikely to have additional planets with masses and orbital periods within a factor oftwo, in marked contrast to 85% of planets in this mass and period range discovered byKepler.