From top left, across: a) survey completeness or “coverage” C, in terms of the fraction of the survey (or specific samples) in which a flare with peak X-ray flux, >f_X,peak,min(erg cm^-2 s^-1) could be detected, for a flare S:N> 10 and a duration of 10⁴ s; f_X,peak,min scales as [S:N threshold]/[]. Key: blue line: serendipitous variable sample (SV); grey line: serendipitous non-variable sample (SNV); the line for all serendipitous stars with time-series is indistinguishable from that for the SNV sample. b) As a), but for peak X-ray luminosity, >L_X,peak,min(erg s^-1); L_X,peak,min scales as [S:N threshold]/[]. c) As a), but for X-ray emitted energy, >E_X,min (erg); E_X,min scales as [S:N threshold] × []. d) As a), but for maximum distance, <d_max (pc) to which a flare with L_X,peak> 10²⁹ or E_X> 10³³ could be detected; d_max scales as or .