Abstract We present a comprehensive data-driven spectroscopic analysis of 357,415 red giant stars using Gaia DR3 Radial Velocity Spectrometer (RVS) spectra (8460–8700 Å; R ≈ 11, 500), aimed at deriving precise stellar parameters and elemental abundances (collectively referred to as stellar labels). We employ The Cannon, a generative model based on 2747 giants in common with GALAH DR4, adopting GALAH labels (R ≈ 28, 000) for training. The resulting model predicts eleven stellar labels for RVS giants: effective temperature (Teff), surface gravity (log g), projected rotational velocity (vsin i), and abundances of Fe/H, Ca/Fe, Si/Fe, Ni/Fe, Ti/Fe, as well as the neutron-capture elements Zr/Fe, Ce/Fe, and Nd/Fe. Building on these results, we develop a probabilistic framework to chemically identify debris from the Gaia–Sausage–Enceladus (GSE) accretion event. A logistic regression classifier, optimised via Markov Chain Monte Carlo sampling and trained on a small reference sample of GSE members and comparison stars, identifies stars with high GSE membership probabilities based solely on their chemical abundances, with the resulting candidates exhibiting distinctive abundance-ratio patterns, including Ca/Ti, Ti/Ce, and Nd/Zr. Applying independent kinematic constraints yields a robust sample of GSE candidates, demonstrating that the characteristic chemical signatures remain consistent after applying these constraints. This work demonstrates the power of data-driven analysis techniques to extract detailed chemical information from medium-resolution spectra and establishes a framework for tracing Galactic accretion events using chemical abundances.
Das et al. (Tue,) studied this question.