The interaction of an isotropic stellar wind with a stratified environment leads to collimate the stellar wind outflow, forming a narrow jet especially in non-adiabatic cases. A jet opening angle, i.e, a jet collimation increases with a jet cooling, in which a free-free radio continuum is dominantly contributed. After a qualitative comparison of the theoretically derived jet boundaries with the optically observed ones have been carried out in order to know the physical parameters of the observed ones as well as to study the jet dynamical interaction with the surrounding medium. Instead of the morphological jet boundary fitting, the free-free radio continuum shapes have been suggested and recalculated.

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