Predictions of White's (1985) nonthermal radio model as applied to the Cyg OB2 stars. The contour plot shows the expected dependence of the combined nonthermal and thermal radio emission (solid lines incremented by 0.5 mJy ranging from 0.5 to 5 mJy) on the stellar mass‐loss rate and the stellar surface magnetic field strength (B). The dashed lines are the resultant radio spectral indices ranging from 0.1 to 0.6. This shows that when the Cyg OB2 stars display nonthermal radio characteristics with α < 0.6, the predicted mass‐loss rate is found to be a factor of 10–100 times smaller than that predicted by assuming a free‐free thermal radio source. The transition between a nonthermal (α < 0.6) and a thermal radio (α = 0.6) spectrum is clearly visible at large mass‐loss rates where the contours become essentially vertical, independent of B as expected.