BAT (15–50 keV; black circles) and XRT (0.5–10 keV; blue squares) light curves of GX 304–1 from January 1, 2012, to October 30, 2018. The time of our NuSTAR observation is indicated with the yellow lines. The three insets show the behaviour of the source during different states (see main text for details). Vertical lines correspond to periastron passages (determined using the ephemeris of Sugizaki et al. 2015).