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.