Propagating absorption enhancements in the wind of the extreme Of supergiant HD 151804

Variations in the shape, position, and strength of the absorption trough of the He I 5876 P Cygni profile have been detected in high-quality Reticon spectra of the extreme Of supergiant HD 151804. These changes are primarily caused by the propagation of absorption enhancements through the trough of the profile. The short time series presented here is dominated by the progressive motion of two enhancement episodes, one of which could be traced for four consecutive days as it accelerated blueward from an initial velocity of -180 km/s to -700 km/s. The acceleration of this enhancement was less than 25 percent of the acceleration expected for the ambient stellar wind. The absorption enhancements could be due to either density enhancements that propagate through the wind or to extended velocity plateaus through which the material of the wind flows. Both of these interpretations are discussed briefly, and the behavior of the absorption enhancements is compared with the behavior of the discrete absorption components that are frequently seen in P Cygni profiles of UV resonance lines.