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From $5.5$ months of dual-band optical photometric monitoring at the $1$ mmaglevel, BRITE-Constellation has revealed two simultaneous types of variabilityin the O4I(n)fp star $\zeta$ Puppis: one single periodic non-sinusoidalcomponent superimposed on a stochastic component. The monoperiodic component isthe $1.78$ d signal previously detected by Coriolis/SMEI, but this time alongwith a prominent first harmonic. The shape of this signal changes over time, abehaviour that is incompatible with stellar oscillations but consistent withrotational modulation arising from evolving bright surface inhomogeneities. Bymeans of a constrained non-linear light curve inversion algorithm we mapped thelocations of the bright surface spots and traced their evolution. Oursimultaneous ground-based multi-site spectroscopic monitoring of the starunveiled cyclical modulation of its He II $\lambda4686$ wind emission line withthe $1.78$-day rotation period, showing signatures of Corotating InteractionRegions (CIRs) that turn out to be driven by the bright photospheric spotsobserved by BRITE. Traces of wind clumps are also observed in the He II$\lambda4686$ line and are correlated with the amplitudes of the stochasticcomponent of the light variations probed by BRITE at the photosphere,suggesting that the BRITE observations additionally unveiled the photosphericdrivers of wind clumps in $\zeta$ Pup and that the clumping phenomenon startsat the very base of the wind. The origins of both the bright surfaceinhomogeneities and the stochastic light variations remain unknown, but asubsurface convective zone might play an important role in the generation ofthese two types of photospheric variability.

monthly notices of the royal astronomical society

BRITE-Constellation high-precision time-dependent photometry of the  early-O-type supergiant $\zeta$ Puppis unveils the photospheric drivers of  its small- and large-scale wind structures