Identifying Ae/Be stars in Gaia low-resolution BP/RP spectra

Classical Be, and Herbig Ae/Be stars are mainly characterized by emission in the Halpha and Hbeta lines. These lines are essential to understanding the formation of massive stars and describing mass loss and stellar winds during stellar evolution. This study aims to characterize and detect classical Be and Herbig Ae/Be stars in Gaia BP/RP spectra, which allow us to investigate the complete stellar spectral range. Synthetic ∆a and Hα index magnitude values were calculated from Gaia BP/RP spectra. Colour-colour diagrams were employed to distinguish emission-line objects from normal stars. With the proposed method here, we could unambiguously retrieve 90% of a sample of well-known emission-line objects. This shows that analyzing the 520 nm and Hα region efficiently discriminates emission-line objects from normal stars. No further assumptions about astrophysical parameters such as reddening, effective temperature, or IR excess are necessary.