Non-LTE abundance patterns in M67

One of the main goals of the Galah survey is to find stellar siblings in the Galactic disk and associate them to a common parent cluster by means of chemistry and dynamics. The success of such chemical tagging hinges critically on our ability to determine the abundances of late-type dwarf and giant stars with high precision, but also to assess whether their present-day abundance patterns truly reflect their original compositions. Open clusters are the perfect laboratories to put our analysis methods to the test.

We use Galah high-resolution data of M67 to determine abundances for 60 high-fidelity members with good quality spectra. Seven elements; Li, O, Na, Mg, Al, Si, and Fe are treated in non-LTE, using recently published grids for late-type stars. We discuss abundance trends with evolutionary phase in the context of systematic errors inferred by LTE analysis as well as atomic diffusion of chemical species.

The NLTE grids will subsequently be incorporated in the main Galah analysis pipeline.

The project is lead by PhD student Xudong Gao at MPIA, with supervisors Karin Lind and Anish Amarsi.

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