Left: Surface abundance of N for the binaries (stars) and the single stars from the sample of Nieva & Przybilla (2012) (circles) as a function of the surface gravity. The horizontal line is the average value of N from Nieva & Przybilla (2012), which we used to compute the stellar models in this work. The color scale shows the surface rotational velocity v sin i in km s⁻¹. Right: Same but for various samples from the literature, with the addition of 33 stars from Aerts et al. (2014) and 28 stars from Morel et al. (2022). Typical error bars for the single stars are shown in light grey in both panels and for the binaries in dark grey in the left panel.