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Published online by Cambridge University Press: 04 August 2017
A recently developed non-LTE code for realistic semi-empirical models of Wolf-Rayet atmospheres is used to calculate synthetic helium lines. From the resulting line strenghts it can be concluded that if He I lines are present, the effective temperatures of these stars have to be less than an upper limit. This limit depends on the stellar radius and is approximately 40kK for R* = 20 R⊙ to 60kK for R* = 5 R⊙.