Identify the physical origin of the surface structures driving DACs

Identify the physical origin of the transient spots or surface inhomogeneities that drive the corotating interaction regions and cyclic discrete absorption components observed in ξ Per and other OB stars.

Background

The paper distinguishes stable, strictly periodic variability attributed to a putative large-scale magnetic field from stochastic or cyclic DAC variability attributed to transient surface spots or inhomogeneities. Although these structures can reproduce aspects of the observed wind variability through CIRs, their underlying physical origin is not established.

References

We suggest that this points to the existence of two distinct drivers: one that must remain stable over timescales of years to decades (i.e. for the entire temporal span of ξ Per's UV dataset), and one that varies in a more stochastic fashion, in a manner consistent with the driving of DACs in other OB stars (presumably spots or surface inhomogeneities whose physical origin remains to be conclusively determined, as previously mentioned).

— Rotation period of the O giant xi Persei: Coexistence of cyclic and periodic variability. A weakly magnetic candidate star  (2610.12323 - Henrichs et al., 8 Oct 2026) in Section 6, “Interpretation of the period”