Top: dependence of the equivalent width of the Ca II K emission on temperature of the parent star. Empty triangles denote exoplanetary systems with a ≤ 0.15 AU, full triangles are systems with a > 0.15 AU, and red squares are our data from FEROS. Emission and chromospheric activity increase with decreasing temperature. Cooler stars (T_eff ≤ 5500 K) with close-in planets are more active than stars with more distant planets. Middle: statistical Student’s t-test (empty circles) and Kolmogorov-Smirnov test (full circles) show whether the two distributions are the same. Bottom: the same statistical tests performed on systems discovered by the RV technique alone.