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Hot, massive (OB) stars experience strong line-driven stellar winds and massloss. As the majority of efficient driving lines are metallic, the amount ofwind driving and mass loss is dependent on the stellar metallicity Z. Inaddition, line-driven winds are intrinsically inhomogeneous and clumpy.However, to date, neither theoretical nor empirical studies of line-drivenwinds have investigated how such wind clumping may also depend on Z. Wetheoretically investigated the degree of wind clumping due to theline-deshadowing instability (LDI) as a function of Z. We performedtwo-dimensional hydrodynamic simulations of the LDI with an assumedone-dimensional radiation line force for a grid of O-star wind models withfixed luminosity, but with different metal contents by varying the accumulativeline strength Qbar describing the total ensemble of driving lines. We findthat, for this fixed luminosity, the amount of wind clumping decreases withmetallicity. The decrease is clearly seen in the statistical properties of oursimulations, but is nonetheless rather weak; a simple power-law fit for thedependence of the clumping factor f_cl = <rho^2>/<rho>^2 on metallicity yieldsf_cl ~ Z^(0.15 +/- 0.01). This implies that empirically derived power-lawdependencies of mass-loss rate Mdot on metallicity -- which were previouslyinferred from spectral diagnostics effectively depending on Mdot*sqrt(f_cl) butwithout having any constraints on f_cl(Z) -- should be only modestly altered byclumping. We expect that this prediction can be directly tested using new datafrom the Hubble Space Telescope Ultraviolet Legacy Library of Young Stars asEssential Standards (ULLYSES) project.

Theoretical wind clumping predictions from 2D LDI models of O-star winds at different metallicities