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tokens: rotational periods cannot be confidently measured because double-peaked and evolving light curves have been observed in many variable brown dwarfs to date (e.g. Apai et al. 2017 ; Vos et al. 2018 ). Longer duration follow-up observations are necessary to robustly measure the rotational periods of the variable objects detected in this survey. 5 SENSITIVITY TO VARIABILITY SIGNALS We construct a sensitivity plot for each observation to determine our sensitivity to variability signals of given amplitudes and periods. We inject simulated sinusoidal curves into random permutations of each target light curve. For targets found to be variable in the survey we divide the light curve by a polynomial fit to the light curve before injecting the simulated sinusoidal signals. The 1000 simulated sine curves have peak-to-peak amplitudes of and periods of 1.5−20 h, with randomly assigned phase shifts. Each simulated light curve is put through our periodogram analysis, which allows us to produce a sensitivity plot, showing thepercentage of recovered signals as a function of amplitude and period. Sensitivity plots for all light curves are shown in the bottom panel of Fig. 5 for variable objects and Fig. A3 (available online) for non-variables in the survey. Figure 5. Light curves, periodograms, and sensitivity plots for variable objects. Top panel: Relative photometry of target. Middle panel: Periodogram of target light curve (black) and periodograms of reference stars (grey). Blue dashed lines show the and significance thresholds. Bottom panel: Sensitivity plot showing the percentage of recovered signals for injected sinusoidal signals of various variability amplitude and periods. 6 SIGNIFICANT DETECTIONS OF VARIABILITY We detect significant variability in seven objects in the survey. Variable objects and their estimated variability amplitudes are presented in Table 2 . We present the light curves of these variable objects along with their reference stars in Fig. 4 . We show their periodograms and sensitivity plots in Fig. 5 . We discuss the first epoch variability detection of each object below. Table 2. Measured first epoch variability amplitudes for variability detections. 2MASS J00452143+1634446 – Gagné et al. ( 2014a ) classify the L2 object 2M0045+16 as a very low gravity brown dwarf, with H α emission and unusually red colours. It has been identified as a bona fide member of the Argus association (30−50 Myr), giving it an estimated mass of 14.7 ± 0.3 M Jup (Gagné et al. 2015a ), however recent work by Bell et al. ( 2015 ) has called into question the validity of the Argus association. We observed 2M0045+16 on 2014 November 11 using NTT SofI. We detect highly significant variability in this object at this epoch. The light curve of 2M0045+16 and the reference stars used for detrending are shown in Fig. 4 and the periodogram and sensitivity plots are shown in Fig. 5 . A lack of stars in the field resulted in only three references stars suitable for