We identified 12 narrow unblended N III lines,
and used their line wavelengths
to create a template spectrum consisting of deltafunctions convolved
with the instrumental broadening (3km/s Gaussian σ).
For each phase bin we computed the cross-correlation function
of the stellar spectrum and the template spectrum. This effectively
combines the information contained in 12 separate spectral lines into
one CCF profile.
The resulting CCF profiles have improved S/N,
and can be used as if they were real line profiles in the mode
identification.
