although not as steep as in L1544, is clear in Fig. \[dv\_b\], where the average value of $\Delta v$ within bins of 15 (see big dots) ranges between 0.3  at the dust peak to 0.25  at a projected distance of 80.

One might interpret this line width gradient as being due to increased optical depth towards the dust peak. This however seems unlikely as illustrated in Fig. \[dv\_phil\], where the profiles of the isolated hyperfine component of the (1–0) line along the 45 and -45 axes, passing through the dust peak position, are shown. If the line is self–absorbed toward the core center, the hyperfine components with the largest statistical weight will be broadened compared to the weakest ones, affecting the hfs fit. However, we performed gaussian fits to all the hyperfines components, finding the same $\Delta v$ values within the uncertainties. In fact, a similar trend is also observed if one plots the linewidth of the $F_1 \, F$ = 1 0 $\rightarrow$ 1 1 (or weakest) component of the (1–0) line versus the impact parameter. This line, being thin and symmetric across the core, is not affected by self–absorption.

We believe that this is a characteristic of unstable 