Coherent transient duty-cycle variation of the |$\widehat{SK^{\ast }}$| estimator (thick lines) and its expected |$\widehat{SK^{\ast }}\pm \sigma ^2_{\widehat{SK^{\ast }}}$| fluctuations (thin lines) for M = 97 (panel a) and M = 9766 (panel b), and three selected signal-to-noise ratios, ρ = 5, 7, and 10 (solid, dashed, and dot–dashed lines, respectively).