Fig. 1: Phosphorus abundances as a function of metallicity.

Red stars and black diamonds show, respectively, the P-rich and P-normal stars analyzed in this work. Error bars represent measurement uncertainties such as shown in Supplementary Tables 2 and 4. The P-normal stars are the group of comparison (twins) stars with very similar stellar parameters to the P-rich ones but with a chemical abundance pattern similar to field stars (see Methods: Chemical abundance analysis). The dotted line shows the empirical definition adopted here to distinguish the P-rich stars from the P-normal ones. Open squares, crosses, and plus signs are literature values from ref. ⁸, ref. ¹³ and refs. ^11,12, respectively. The long-dashed line shows the chemical evolution model from ref. ⁵, short-dashed line from ref. ⁶ and solid line from ref. ⁷ Error bars have been adopted from same literature references.