Vogt & Penrod (1983) investigated the
origin of the line-profile variability in the bright O9.5 Ve star
ζ Oph, with rotational velocity Veqsin(i) = 370
km/s. They modelled
- surface spots
- circumstellar blobs/spokes
- NRP ← ← ← ←
and concluded that the observations favour the NRP model.
However, this paper did not completely
settle the debate about the origin of LPV in early-type stars, but
did spark off the development of the Doppler-Imaging technique.
