Fig. 1.
Logarithm of the ratio of the equivalent width of He I 4471 to the equivalent width of He II 4542 as a function of spectral type for our sample (red triangles). Gray points and error bars indicate the average and dispersion. Gray dotted lines show the limits for spectral types O3–O9.7 defined by Conti & Alschuler (1971) and Mathys (1988, 1989).
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