& $5\times10^{-4}$\
BPL & $\phm{+}3.3\pm1.3$ & $2.0\pm0.6$ & $1.6\pm1.1$ & $-3.3\pm0.8$ & & & & $\phm{-}0.31\pm0.82$ & $1\times10^{-3}$\
SPL+Periodic & $-2.1\pm0.3$ & $1.6\pm0.1$ & & & $-1.2\pm1.3$ & $-3.87\pm0.30$ & $-4.5\pm0.8$ & $-3.34\pm1.14$ &\
DRW+Periodic & $\phm{+}3.4\pm0.5$ & & & $-3.2\pm0.3$ & $-1.2\pm1.1$ & $-3.88\pm0.23$ & $-4.7\pm0.8$ & $-1.75\pm0.97$ &\
BPL+Periodic & $\phm{+}2.5\pm1.2$ & $2.3\pm0.8$ & $1.7\pm0.9$ & $-2.8\pm0.8$ & $-1.5\pm1.4$ & $-3.80\pm0.36$ & $-4.5\pm0.9$ & $-2.78\pm0.76$ &

Power Spectral Density Analysis
===============================

In Figure \[fig\_psd\], we [show]{} the PSD of the merged light curve. We resample the light curve into an even time grid, subtract the mean flux to eliminate the zero-frequency power, and then calculate the modulus squared of the discrete Fourier transform at each sampled frequency $f_j$ (@Uttley2002) $$|F_N(f_j)|^2 = \left[\sum_{i=1}^{N} x_i\cos(2\pi f_j t_i) \right]^2 + \left[ \sum_{i=1}^{N} x_i\sin(2\pi f_j t_i) \right]^2,$$ where $x_i$ is the flux at time $t_i$, $f_j=j/N\Delta T$ with $j=1, ..., N/2$, $\Delta T$ is the sampling interval, and $N$ is the number of points in the data. The PSD is defined with an adopted normalization as $$P(f_j) = \frac{2\Delta T}{N}|F_N(f_j)|^2.$$ To compare with the X-ray PSD, we also bin the logarithm of the PSD over a logarithmically spaced frequency grid, with a 