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Macroturbulence, introduced as a fudge to reproduce the width and shape ofstellar absorption lines, reflects gas motions in stellar atmospheres. While incool stars, it is thought to be caused by convection zones immediately beneaththe stellar surface, the origin of macroturbulence in hot stars is still underdiscussion. Recent works established a correlation between theturbulent-to-total pressure ratio inside the envelope of stellar models and themacroturbulent velocities observed in corresponding Galactic stars. To probethis connection further, we evaluated the turbulent pressure that arises in theenvelope convective zones of stellar models in the mass range 1-125 Msun basedon the mixing-length theory and computed for metallicities of the Large andSmall Magellanic Cloud. We find that the turbulent pressure contributions inmodels with these metallicities located in the hot high-luminosity part of theHertzsprung-Russel (HR) diagram is lower than in similar models with solarmetallicity, whereas the turbulent pressure in low-metallicity modelspopulating the cool part of the HR-diagram is not reduced. Based on our models,we find that the currently available observations of hot massive stars in theMagellanic Clouds appear to support a connection between macroturbulence andthe turbulent pressure in stellar envelopes. Multidimensional simulations ofsub-surface convection zones and a larger number of high-quality observationsare necessary to test this idea more rigorously.

Metallicity dependence of turbulent pressure and macroturbulence in stellar envelopes