What Line Profiles Can Tell Us
The wavelength of an emitted photon is proportional to the line-of-sight velocity:
Line shape maps emission measure at each velocity/wavelength interval
Continuum absorption by the cold stellar wind affects the line shape
Correlation between line-of-sight velocity and absorption optical depth will cause asymmetries in emission lines
X-ray line profiles can provide the most direct observational constraints on the X-ray production mechanism in hot stars