Time-Series Observations of O Stars. III. IUE and HST Spectroscopy of zeta Ophiuchi and Implications for the ``Photospheric Connection''

Stellar-wind variability in the archetypal nonradially pulsating O star ζ Oph (O9.5 V) is discussed on the basis of new time-series IUE and HST spectroscopy and archival results. Time-variable discrete absorption components are first observed at high velocities (≥10 3 km s −1 ≃0.8v∞) and then migrate blueward; the recurrence time scale for the phenomenon is ∼20 hr. This is the first record of this type of variability in a luminosity-class V star and provides support for the previously inferred ubiquity of such behavior across the O-star regime. The accelerations are slower than predicted by steady state wind models and are unlikely to represent the time-averaged velocity law of the outflow