Relationship between $\overline{{\sigma }_{\text{b}}}$ and the NIV in simulated pink-noise eROSITA-like light curves. The relationship depends on both the number of bins and the count rate, so this figure showcases two examples. The top panel depicts the relationship for 1000-bin light curves with a mean count rate of 30 cts s⁻¹. The lower panel shows the relationship for light curves of 135 bins, with a mean count rate of 0.3 cts s⁻¹. The solid black line depicts the best fit of $\overline{{\sigma }_{\text{b}}}\left(\text{NEV},\overline{R_{\text{S}}},N_{\text{b}}\right)$, using Eq. (6) and the parameters listed in Table 1. The dashed line represents using a simpler version of Eq. (6), in which the parameters a, b, and c are constant. The dotted line shows the fit of ${\text{NEV}}_{\text{b}}\propto \sqrt{\overline{{\sigma }_{\text{b}}}}$ for simulated values of NIV above the detection limit.