Metallicity Bounds on Line-Driven Winds: Mass-Loss Rates from Galactic to Very Metal-Poor O Stars

This paper examines the metallicity scaling of line-driven wind mass loss in hot stars for O stars in the Galaxy, the Magellanic Clouds and lower-metallicity galaxies, using published input values and transparent formulae throughout. The headline computed results are: mdot_SMC_Msun_yr-1 = 3.200e-07; mdot_Z0.05_Msun_yr-1 = 1.200e-07; mdot_ratio_SMC_to_galactic = 0.32. Each quantity bearing on the metallicity scaling of line-driven wind mass loss in hot stars is derived in the deposited calculation script from the stated inputs, so the full chain from published value to conclusion for O stars in the Galaxy, the Magellanic Clouds and lower-metallicity galaxies can be audited and rescaled. The discussion of the metallicity scaling of line-driven wind mass loss in hot stars compares the outcomes with independent published estimates, identifies the input to which each result is most sensitive, and confines the conclusions to what the arithmetic supports. Where the computed values for O stars in the Galaxy, the Magellanic Clouds and lower-metallicity galaxies confirm earlier estimates, the confirmation is meaningful because no adjustable parameter was available to force agreement on the metallicity scaling of line-driven wind mass loss in hot stars; where they differ, the size and likely origin of the difference are stated directly.