tokens: for the SR effect in H and K. To convert stellar fluxes to magnitudes, we set the zero-point magnitude to the instrumental zero-point (one ADU/s in H and K, are 25.2 and 24.8 magnitudes, respectively). To double check our calibration, we compared H and K magnitudes of 26 sources (located r ≥ 3 ′′ from R136a1) common between our catalogue and the VLT/MAD (Campbell et al. 2010 ) in H and K. 2 We cannot compare our zero-points with the MAD/H and K magnitudes in the central 2.8 ′′ region because of the completeness issue and the very low AO correction (SR ∼ 15–30 per cent) of their data. Fig. 2 shows the completeness and contrast problem of the previous data, leading to an inability to distinguish certain sources. By way of example R136a6 (H19) and H26 3 – are very close in terms of brightness (flux ratio of about 90 per cent) and location (separation of about 70 mas). These bright O-type stars are most easily detectable in our data compared with others (Figs 2 and A2 ). Cases like these close bright stars, bring confusion even in the HST spectroscopic analysis (Bestenlehner et al. 2020 ). The K magnitude of R136a1 and R136a2 (11.15 mag and 11.43 mag) increased about 0.08 and 0.11 mag, compared to their K mag in the first epoch (11.07 mag and 11.32 mag). The brightness of R136a3 and R136b in K (11.45 mag and 11.67 mag) is consistent with the first epoch K data (11.44 mag and 11.66 mag). R136c in the K (11.31 mag) is 0.17 mag brighter than in 2015 (11.48 mag), making this source the second brightest in our K catalogue. In previous studies, R136c shows indications of binarity based on its strong X-ray emission (Portegies Zwart, Pooley Lewin 2002 ; Townsley et al. 2006 ; Guerrero Chu 2008 ) and possible low-amplitude RV variations (Schnurr et al. 2009 ). Comparing the brightness of common detected sources within two epochs, the K magnitude of 56 per cent of the sources has changed more than twice their photometric errors. 4 To make sure that this is not due to Starfinder photometry analysis (which is based on the reference input PSF), we have used daophot algorithm for this analysis as well. The variation of the K magnitude of these sources still remains. 5 The K mag of about 67 per cent of the sources located outside of the core ( r > 3 ′′ ) has changed more than twice their photometric errors. Since the observations were made in different nights and the AO correction in the outer part of the FOV is not as good as its centre, this inconsistency is probably an observational effect; otherwise, it is originated from physical reasons like variables or multiple systems with periods less than 3 yr. 4 COMPLETENESS We produced 6.2 × 10 4 artificial stars (500 per magnitude) in H and K, in order to determine the completeness as a function of magnitude. These artificial stars are created using the same PSF as we used for source extraction process. They are added to the original image one by one (500 times per magnitude) and the same photometric tools and
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