Program: GS-2023A-Q-412

The discovery and analysis of so-called extremely metal-poor stars (EMP, [Fe/H] < -3) have been the primary scientific drivers for many large-scale observational campaigns over the past 50 years. In this stellar archaeology endeavor, innovative techniques and novel data sets are constantly looked for in the quest of finding these EMP stars as they are crucial for advancing our knowledge about the early chemodynamical evolution of the Galaxy as well the properties of the first stars and their associated supernovae. For this program, low-resolution “XP” spectra from Gaia DR3 are used to find EMP star candidates with unprecedented purity (predicted to be ~90% in comparison to <15% from recent similar efforts in the literature). This is achieved by determining metallicities for low-metallicity stars with available XP spectra with data-driven methods and robust training sets. In this context, the goal of this proposal is to spectroscopically confirm the EMP status for a sample of 60 bright (Gaia’s BP < 16) candidates by measuring stellar parameters for them from GMOS/Gemini South spectra. With this new data, it will also be possible to measure carbon and alpha-element abundances which are useful for selecting the most interesting EMP stars for further follow-up with higher-resolution spectroscopy with GHOST. If the new strategy’s efficiency in finding genuine EMP stars can be confirmed by these new GMOS data, it would represent a >70% improvement in comparison to past works, completely shifting the paradigm on how to best search for the lowest-metallicity stars in the Galaxy.