Example long-term light curves of variable sources in 4XMM-DR9s. Red: mean all-EPIC flux and flux error. Blue: observation-level fluxes. The plot symbols code the variability. Information on short-term variability within an observation is inherited from 4XMM-DR9. Filled circle: variability. Open circle: no variability. Box: short-term variability unknown. Dot: non-detection in 4XMM-DR9. From top to bottom: flaring M dwarf, star of unknown optical variability, gamma-ray burst afterglow, which became undetectable in single XMM-Newton observations after about two years, and a quasar.