Our
idea: fit lines with the simplest model that can do the job, and use
one that, while based in physics, is general in the sense that any
number of physical models can be tested or constrained based on
the model fits.
From Owocki & Cohen (2001): spherically symmetric,
two-fluid (hot plasma is interspersed
in the cold, x-ray absorbing bulk wind); beta velocity law.
Visualizations of the wind use hue to
indicate line-of-sight velocity and saturation to indicate emissivity; corresponding
profiles are plotted vs. scaled velocity where x = -1,1 correspond to the
terminal velocity.