Top panel: abundance pattern of HE0107-5240 (blue filled circles, from Christlieb et al. 2004; and Bessell et al. 2004). Black solid and dashed lines represent the surface abundance of models M2 and Z7 (see Sect. 6 for more details on this model) respectively. Blue lines show the abundance patterns after dilution by factors of f_D = 7.4 × 10^-3 and 5.4 × 10^-3 (models M2 and Z7 respectively), which are derived by matching the observed carbon abundance. Arrows indicate upper limits. Li abundance is given as log   ϵ(Li) = log    (N_Li/N_H) + 12. The zero point on the y-axis corresponds to [Fe/H] = − 5.3. Bottom panel: same as above but for HE-1327-2326 (red filled circles, data from Frebel et al. 2008). For this star, the models shown are M2 and M5. Abundance patterns after dilution (f_D = 1.3 × 10^-3 and 2.1 × 10^-3 for M2 and M5 respectively) are shown in red solid and dashed lines, as indicated in the plot. The zero point of the y-axis corresponds to [Fe/H] = − 5.96.