C¹⁸O J = 2−1 radial intensity profiles derived from fitting the synthetic observations. Shown are the results for an inclination of 45° at five different times (given in the panels) in the post-burst phase and in the quiescent phase (last panel). Each individual panel shows the “real” beam convolved simulations (black solid line), a fit using one Gaussian (1GF, red dashed line) and a fit using two Gaussians (2GF, blue dashed line). In the legend the FWHM/2 (R_50%) value for the fitted Gaussian(s) is denoted (indicated by the big dots). For the 2GF both radii (for each Gaussian) and the ratio of the two radii are provided. For comparison, the actual CO ice lines in the quiescent phase and in the burst phase are located at R_Q(CO#) ≈ 300 au and R_B(CO#) ≈ 2500 au, respectively (see Sect. 3.2 and Fig. 3).