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tokens: Apart from the much higher signal-to-noise ratio, the real part of the visibilities show a behavior similar to that shown by Andrews et al. (2012) , with a drop off from 1.72 Jy at the shortest baselines to a minimum of 0.057 Jy near 190 k, followed by a second maximum of 0.123 Jy around 275 k and a subsequent decrease to 0.028 Jy at our longest baseline of 410 k. The data of Andrews et al. (2012) continue to longer baselines of 600 k with fluxes approaching 0 Jy. Fig. 2 Real (black points) and imaginary (red points) parts of the visibilities of project 340.S (previously presented in Qi et al. 2013 ) in Jy vs deprojected baseline length in k. The inset shows the region of 120–420 k in greater detail. The dashed black curve shows the recalculated single power-law model of Andrews et al. (2012, their model pC) , which fails to reproduce the data on baselines 290 k. A much better fit is found for a broken power-law model described in Sect. 3 (solid blue curve). Because both models are symmetric, the imaginary parts of their visibilities are all 0 (not shown). We overplot the data with the model presented by Andrews et al. (2012, their model pC) which they find to best fit the continuum data. We recalculate the model at the exact observing wavelengths of the ALMA data. Our model is geometrically thin and uses only the midplane temperatures as calculated by Andrews et al. (2012) (see Sect. 3 ). Our model curve therefore differs in detail from the one shown by Andrews et al. (2012) , but qualitatively shows the same behavior. In particular, it fits the data well out to baselines of 290 k but severely underpredicts the emission on baselines of 300 and 400 k, corresponding to angular scales of – (27–37 au). In the next section we attempt to find a model description that provides a better fit. 3. Model fitting To further investigate the disk structure that best describes the observed emission, we consider the deprojected and radially binned real visibilities of data set 340.S. We fit to the 41 data points plotted in Fig. 2 rather than the full set of complex visibilities to speed up calculations. Since the observed emission is symmetric (imaginary visibilities are all 0) and the 41 data points in Fig. 2 fully sample the curve and do not average out any detected asymmetric structure, this simplification is allowed. As a consequence of using only the binned visibilities, our fitting places relatively little weight on the shortest baselines, which represent the total flux. Because we are primarily interested in the spatial distribution of the emission, rather than the total amount, our results are not affected. However, even a small discrepancy in total flux would be accentuated if we would calculate a residual image. For this reason, we refrain from imaging the residuals and exclusively work with the visibilities. The real part of the visibilities, , are related to the intensity distribution of the source by where is the baseline length, is the