Left panel: SPIRou B_ℓ measurements from Donati et al. (2023) and associated LS periodogram. The horizontal dashed lines represent the FAP levels of 0.1%, 1%, and 10% respectively. A significant peak at Ρ = 13.87 days (and lyr alias at 14.98 days) is clearly observed, which is associated with to 13.91 ± 0.09 day rotational period of the star Donati et al. (2023). An additional significant peak is seen at 9.41 days. No signals are seen at Ρ = 6.02 days. Right panel: quasi-periodic GP model fit (blue-line) of the SPIRou B_ℓ time series (black dots). Details of the GP are given in Table C.1. The corner plot of the fit is given in Fig. D.1.