Stellar atmospheric parameters from Gaia BP/RP spectra using Uncertain Neural Networks

ABSTRACT With the plentiful information available in the Gaia BP/RP spectra, there is significant scope for applying discriminative models to extract stellar atmospheric parameters and abundances. We describe an approach to leverage an ‘Uncertain Neural Network’ model trained on APOGEE data to provide high-quality predictions with robust estimates for per-prediction uncertainty. We report median formal uncertainties of 0.068 dex, 69.1 K, 0.14 dex, 0.031 dex, 0.040 dex, and 0.029 dex for Fe/H, Teff, log g, C/Fe, N/Fe, and α/M, respectively. We validate these predictions against our APOGEE training data, LAMOST, and Gaia GSP-phot stellar parameters, and see a strong correlation between our predicted parameters and those derived from these surveys. We investigate the information content of the spectra by considering the ‘attention’ our model pays to different spectral features compared to expectations from synthetic spectra calculations. Our model’s predictions are applied to the Gaia data set, and we produce a publicly available catalogue of our model’s predictions.