Abstract
A preliminary model that reproduces the general characteristics of equivalent widths and profiles of ultraviolet spectral lines corresponding to ions such as C IV, Si IV, and N V which frequently exhibit asymmetric profiles and which are particularly observed in early type objects undergoing mass loss, is presented. The model considers terms due to kinetic and potential energies as well as radiative losses in solving for the energy balance equation. In a first approximation, it is shown how the kinetic energy can account for the heating of the material up to temperatures compatible with the formation of ions like C IV and Si IV by collisional processes. Agreement, at least as to the order of magnitude, between the model and the observations is found if the existence of some kind of braking mechanism is postulated.
