Fitted parameters and , for the three models. The colour scale goes from blue (cold) to red (warm). The filled symbols correspond to the SEDs shown in Fig. 1. All points have similar relative uncertainty; the error bars for the lowest U_min are shown. The uncertainties are systematic, so they affect each point in the same way; errors on the two axes are strongly anti-correlated (see Sect. 3.1). The horizontal grey lines show and the 15% uncertainty in the A_V normalisation (Sect. 2.1). The slanted grey lines are the least-square fits for each model; they were added to more easily tell apart the three models.