Chandra background-subtracted light curves in bins of 5500 s. From top to bottom: 0.3−8 keV count rates of the whole NGC 6240 galaxy, 0.3−8 keV count rates of the southern nucleus, 0.3−8 keV count rates of the northern nucleus, and 6.4−8 keV count rates of the northern nucleus. The dot-dashed lines correspond to the values of the count rate weighted means. Left panels: the light curves of the two ACIS-S Chandra observations (see Table 2): 1590 (magenta open dots) and 12713 (black solid dots). Right panels: the light curves of the zero-order ACIS-S HETG Chandra data: 6909 (blue solid squares) and 6908 (red open squares). We note that the X-axis does not represent the real time.