Violin plots of key stellar parameters for the 8 inferences used to define the asteroseismic measurement in Table 1, as well as for the helium-free inference (right-most). Left-most inference defines the reference for the median measurement and statistical uncertainty in Table 1, while the maximum median difference to the remaining 7 constrained-helium inferences defines the systematic uncertainty on the quoted parameters. See the Sect. 2.7 and Appendix G.3 for details. The median parameter values of the reference fit is drawn through the whole plot (grey dashed line). The helium-free inference here has a lower bound on initial helium of 0.248 corresponding to the primordial helium fraction.