Emission-line studies of young stars. I - The T Tauri stars. II - The Herbig Ae/Be stars

Optical spectra are obtained and analyzed for 53 T Tauri stars (TTSs) and 32 Herbig Ae/Be to constrain models of their stellar environments by separating star and envelope emissions. Specific attention is given to such emission lines as the near-IR Ca II triplet, weak blue lines, and standard optical lines including H-alpha. Distinct broad and narrow emission-line components are noted which correspond to the outer envelope and the active stellar chromospheres, respectively. The chromospheric interpretation of the narrow lines is shown to be significant particularly because it supports prevous interpretations of the TTS dense high-velocity envelopes. The emission-line diagnostics of the Herbig star envelopes are compared to classical TTSs with strong H-alpha emissions, and the accretion-disk models for the classical TTSs is shown to be applicable to Herbig stars with TTS-like spectra. The similarities between Herbig and TTS objects imply that accretion disks play a key role in the Herbig stars.