Total density, kinetic temperature, molecular abundance, and velocity profile used for the models of Fig. 5 for IK Tau. We also show for comparison the temperatures obtained by Bujarrabal et al. (1989; dashed line) and Decin et al. (2010; dotted line). In the velocity plot we include, for comparison, the velocity by Decin et al. (2010; dotted line). The velocity stays constant at 1 km s⁻¹ up to the distance R_d, and then gradually increases as described in Eqs. (3) and (4).