Detection criteria for all observations. Panel a: detection criterion N2 for the observable quantity Q1b. Panel b: detection criterion N6 for the observable quantity Q4f. Only the lowest frequency band (15–38 MHz for τ Boo and υ And and 26–50 MHz for 55 Cnc) and |V| is shown. The median value for all post-processing runs is shown as a dashed line. The 1 σ standard deviation is shown as the gray area.