Left: [C/N] and log (¹²C /¹³C) in the ejecta as a function of the ejected mass for the 20s7 model. The thick lines in the yellow zone represent the integrated ratios in the wind (Eq. (2)) as a function of . The thin lines show the integrated ratios in the ejecta (Eq. (5)) as a function of . The grey shaded area shows the location of the He-burning shell (where the energy produced by He-burning ϵ_He> 10³ erg g^-1 s^-1) at the end of the evolution. Middle and right: distribution of observed log (¹²C/¹³C) and [C/N] for the CEMP-no stars with [ Fe / H ] < − 2.5, [ C / Fe ] > 0.7 and [ Ba / Fe ] < 1 (Cohen et al. 2004, 2013; Honda et al. 2004; Christlieb et al. 2004; Sivarani et al. 2006; Beers et al. 2007; Johnson et al. 2007; Lai et al. 2008; Masseron et al. 2010; Caffau et al. 2011; Allen et al. 2012; Norris et al. 2012, 2013; Yong et al. 2013; Spite et al. 2013; Placco et al. 2014a; Roederer et al. 2014b,c; Hansen et al. 2014, 2015). The green histogram represents the MS stars or subgiants close to the turnoff with T_eff> 5500 K and log g ≥ 3.25, as by Norris et al. (2013). The blue histogram shows the other stars.