Iron Spread in globular clusters

We used the Python-based tool Q2 to determine both differential stellar parameters and iron abundances for 92 sibling stars -- defined by the similarities in their stellar parameters -- across 13 Galactic globular clusters. This differential approach reduces the influence of non-local thermodynamic equilibrium effects, and minimises observational errors, and systematic biases linked to stellar parameters. We performed Monte Carlo simulations to evaluate the statistical significance of the measured spreads.

Most of the globular clusters in our sample do not show evidence of statistically significant iron spreads. Only a few exceptions emerge, namely NGC1851, NGC3201, and NGC5634, which display a highly significant iron spread. In particular, NGC3201 shows a particularly pronounced spread in its first-generation population, reflecting a potential inhomogeneous iron abundance in its pristine material.

Finally, through statistical tests, we conclude that our data do not support the presence of a widespread iron variation in globular clusters.