Multi-wavelength light curves of PSR J1311−3430. Top panel: 0.15–10 keV energy range, XMM-Newton/EPIC data (background-subtracted, 500 s binning). A count rate to flux conversion was performed using results of time-averaged spectroscopy. The approximate time of the centres of the six ‘pulses’ is marked by vertical dashed-dotted lines (adopting 7450 s as the recurrence time – see Sect. 2.1). We also extended to earlier times the expected time of arrivals (dotted lines) to show the possible alignment of a further peak at T = 4000 s with the pulses. The first pulse peak occurs at orbital phase 0.08 ± 0.03 (as computed from the U-band light curve, phase 0.75 marking the companion star superior conjunction). Middle panel: U band, XMM-Newton/OM data (background-subtracted, 500 s binning). Bottom panel: g′ band, Las Cumbres Observatory – 1 m telescope data. Black points represent 103 observations lasting 300 s; red points correspond to the sum of four observations (totalling 1200 s integration) collected around the times of two different g′ light-curve minima, with the first being associated with quiescent X-ray emission (g′ = 23.4 ± 0.5) and the second being associated with an X-ray pulse (g′ = 21.6 ± 0.3); and upper limits are shown as blue arrows. For all of the panels, time was measured in seconds since 2018 February 09 22:18:50.8. Error bars show uncertainties at the 1σ confidence level.