Upper panel: resulting peak bagging best-fit for KIC 9139163 as derived by means of Diamonds  by using Approach 1 based on the background that is estimated in Sect. 6.2 (red thick line) overlaid on the PSD smoothed by 0.25 μHz (gray). The mean background level is shown as a dashed blue line. Dotted vertical lines mark the oscillation peaks for which the detection probability is below 99% with labels indicating the corresponding peak identification, as reported in Table A.1 and as explained in Appendix A. Lower panel: ratio between the smoothed PSD and the resulting red line fit that is shown in the upper panel.