Model combining a long-period planet with a GP model at shorter periods for HIP 64823. Top left: the combined 1P+GP model fitted to the data. Top right: RV residuals after subtracting the GP model, phase-folded to highlight the contribution of the planet. Bottom left: RV residuals after removing the contribution of the planet to highlight the GP model. Bottom right: residual RV periodogram showing only tentative periodicity at shorter periods. The FAPs of 5% (dashed), 1% (dash-dotted), and 0.1% (dotted) are plotted as gray horizontal lines.