Alias tests for HD 238090. The top plot (a) shows simulations motivated by a sampling frequency of . The bottom plot (b) shows simulations motivated by a sampling frequency of . Each row in these plots corresponds to one set of simulations for which the frequency of the injected signal is indicated by a vertical dashed blue line. The first row shows simulations with a period of 13.6838 d, and the second and third row show the simulations where the first-order aliases of 13.68 d, regarding the investigated sampling frequency were injected. Each column shows informative ranges of the periodograms, which are based on the assumed sampling frequency, and can be used for the comparison of data and simulations. From 1000 simulated data sets each, the median of the obtained periodograms (solid black line), the inter-quartile range and the ranges of 90% and 99% (gray shades) are shown. For comparison, the periodogram of the observed true data is plotted with a solid red line. The angular mean of the phase of some peaks and their standard deviation are shown in the clockdiagrams (black line and gray shades) and can be compared to the phase of these peaks in the observed periodogram (red line).