TVS peak intensity as a function of fraction of the line formed in the wind. Filled symbols correspond to the sample stars showing variability on a daily timescale. The solid open triangles show the variability of synthetic lines for which the mass loss rate varies by 25%, starting from the best fit model of ϵ Ori. The dotted triangles represent the theoretical variability due to changes in β (from 0.8 to 1.4) in the best fit model of ϵ Ori. The points for Hα, Hβ, and Hγ are out of the plot (amplitudes of 0.135, 0.104, and 0.070, respectively).