Effective Temperatures of Massive Stars as a Function of Chemical Composition and Mass

Theoretical models for main-sequence stars of 50 and 100 have oeen constructed for a range in heavy-element abundance 10- <Z < 10-'. For a given mass, significant differences in the stellar effective temperature and size of H ii region are found for moderate changes in Z. These differences are such that stars with lower Z have higher effective temperatures. The results suggest that the expected increase in excitation temperature in low-Z H ii regions due to less efficient cooling will be enhanced.