1996A&A...311..616R

We present time-resolved echelle spectroscopy of the O4 I(n)f supergiant ζ Puppis. Variations are observed in all absorption-line profiles, with typical peak-to-peak amplitudes of ∼2% of the continuum intensity (∼4% in He II λ5411A). All observed absorption lines (He I, He II, N IV, and C IV) show the same gross characteristics, with `bumps' and `dips' moving blue-to-red through the profiles, with no detectable line-to-line velocity shifts in the variability pattern (<15km/s) although there are differences in the relative amplitudes across the lines. The time dependence of the variability is investigated by using a 2-D clean power-spectrum analysis. Significant power is found at a period of ∼8.54hr; the underlying signal is marginally consistent with sectorial, prograde non-radial pulsations with l=-m=2, although this does not account for all the observed variability. The blue emission wing of Hα was included in the echellograms, and, in contrast to the absorption lines, shows features moving red-to-blue with a period of 8.5hr (the absorption-line period). The Hα data also show features at a period of 19.6hr (the recurrence time of the `discrete absorption features' observed in UV P-Cygni resonance lines), moving blue-to-red at velocities more positive than -280km/s and red-to-blue at more negative velocities. The temporal behaviour of Hα provides the first direct evidence for a dynamical response of a radiation-driven wind to basal velocity fields.