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Fig. 1

image

Comparison between our results (cooler and hotter stars are depicted (from top to bottom) in rows 1 and 2) and those of some previous non-LTE studies for nearby OB stars (rows 3–6 for Gies & Lambert 1992; Hunter et al. 2009; Nieva & Przybilla 2012; and Martins et al. 2015a,b). Green histograms/symbols represent supergiant stars. The blue and black histograms/symbols in the bottom panels correspond to the sample of normal O and ON stars analysed by Martins et al. (2015a,b), respectively. Columns 1–3 show the C, N, and O abundances, respectively, and Cols. 4 and 5 the [N/C] and [N/O] abundance ratios. Lower and upper limits are ignored in all plots. The solar values of Grevesse & Sauval (1998) and Asplund et al. (2009) are shown in these panels as blue solid and blue dashed lines, respectively. The baseline values adopted in the Bonn and Geneva evolutionary models are shown as red solid and red dashed lines, respectively. The two rightmost columns show the breakdown of vsini values (the percentage of stars with vsini ≥ 200 km s-1 in each sample is indicated) and the position of targets in the Kiel diagram. In the last column, evolutionary tracks from the Geneva group at solar metallicity and including rotation are overplotted with initial stellar masses (in M) indicated. Rotational velocities at the ZAMS for stellar masses higher than 12 M are listed in Table 1; for 7, 9, and 12 M, the initial rotational velocities are 352, 381, and 404 km s-1, respectively.

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