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OB stars exhibit various types of spectral variability historicallyassociated with wind structures, including the apparently ubiquitous discreteabsorption components (DACs). These features have been proposed to be causedeither by magnetic fields or non-radial pulsations. In this second paper ofthis series, we revisit the canonical phenomenological hydrodynamical modellingused to explain the formation of DACs by taking into account modernobservations and more realistic theoretical predictions. Using constraints onputative bright spots located on the surface of the O giant $\xi$ Perseiderived from high precision space-based broadband optical photometry obtainedwith the Microvariability and Oscillations of STars (MOST) space telescope, wegenerate two-dimensional hydrodynamical simulations of co-rotating interactionregions in its wind. We then compute synthetic ultraviolet (UV) resonance lineprofiles using Sobolev Exact Integration and compare them with historicaltimeseries obtained by the International Ultraviolet Explorer (IUE) to evaluateif the observed behaviour of $\xi$ Persei's DACs is reproduced. Testing threedifferent models of spot size and strength, we find that the classical patternof variability can be successfully reproduced for two of them: the model withthe smallest spots yields absorption features that are incompatible withobservations. Furthermore, we test the effect of the radial dependence ofionization levels on line driving, but cannot conclusively assess theimportance of this factor. In conclusion, this study self-consistently linksoptical photometry and UV spectroscopy, paving the way to a betterunderstanding of cyclical wind variability in massive stars in the context ofthe bright spot paradigm.

monthly notices of the royal astronomical society

Investigating the origin of cyclical wind variability in hot, massive  stars - II. Hydrodynamical simulations of co-rotating interaction regions  using realistic spot parameters for the O giant $\xi$ Persei