M67 solar twins chemical compositions

M67-1315 is warmer than M67-1194 by ~=150K as well as slightly more metal-poor than M67-1194 by ~=0.05dex. M67-1194 is also found to have identical chemical composition to the Sun, confirming its solar-twin nature. The abundance ratios [X/Fe] of M67-1315 are similar to the solar abundances for elements with atomic number Z<=30, while most neutron-capture elements are enriched by ~=0.05dex, which might be attributed to enrichment from a mixture of asymptotic giant branch ejecta and r-process material.

The distinct chemical abundances for the neutron-capture elements in M67-1315 and the lower metallicity of this star compared to M67-1194, indicate that the stars in M67 are likely not chemically homogeneous. This poses a challenge for the concept of chemical tagging since it is based on the assumption of stars forming in the same star-forming aggregate.