Simulation of the effect of a very unstable P_sh in evaluating the scatter of intensity in various Φ_sh. a) The intensity curve artificially shifted in Φ_sh. The folded data were smoothed by the two-sided moving averages for various Q (in units of Φ_sh) (see the legend). b) Smoothed residuals σ_resSim of the fits. c) The number of data included in calculation of each mean. d) Dependence of the relative intensity and σ_resSim for the simulated data. They were smoothed by the moving averages with various Q. The observed data for S1 are included, too. Some Φ_sh are marked. See Sect. 3.2 for details. (This figure is available in color in electronic form.)