CEMP prediction abundances

They are often the result of mass-transfer from a companion, but some of the most metal-poor C-rich objects are likely carrying the imprint of the metal-free First Stars from birth. In this work, we employ a neural network to predict metallicities and carbon abundances for over 10 million stars with Gaia low-resolution XP spectra, down to [Fe/H]=-3.0 and up to [C/Fe]=~+2.

We identify ~2000 high-confidence bright (G<16) carbon-enhanced metal-poor (CEMP) stars with [Fe/H]<-2.0 and [C/Fe]>+0.7. The majority of our C-rich candidates have [Fe/H]>-2.0 and are expected to be binary mass-transfer products, supported by high barium abundances in GALAH and/or their Gaia RUWE and radial velocity variations. We confirm previous findings of an increase in C-rich stars with decreasing metallicity, adopting a definition of 3{sigma} outliers from the [C/Fe] distribution, although our frequency appears to flatten for -3.0<[Fe/H]<-2.0 at a level of 6-7%.