V² measurements of 2017 and 2019. Two uniform-disk plus background models are shown: the average best-fit in the continuum (2.1–2.2 μm, black line) and the average uniform-disk diameter in the CO 5-3 band head (2.381–2.387 μm, colored lines), both of them with the measured background level in parenthesis. Only the data in those two wavelength ranges are shown. The dotted line reveals the pure UD fit of the visibilities in the continuum assuming no incoherent background.