EMISSION-LINE DIAGNOSTICS OF T-TAURI MAGNETOSPHERIC ACCRETION - I - LINE-PROFILE OBSERVATIONS

We present high-resolution spectra of classical T Tauri stars in Tauru s in the range 5800-9000 Angstrom to critically examine the current th eories of magnetospheric accretion. In this paper, we focus on the emi ssion lines of hydrogen (the higher Paschen series and H alpha), He I lambda 5876, O I lambda 7773 and lambda 8446, the Na D lines, and the Ca II infrared triplet. We argue that the magnetospheric infall zone i s the likely source of emission for the hydrogen, oxygen, and sodium l ines for most of the stars in our sample. As has been previously shown , the calcium and helium lines have a narrow and a broad component; fo cusing on the broad components, we find that they are likely formed in the magnetosphere for at least several of the stars in the sample. Pr eliminary calculations indicate that the magnetospheric models develop ed to explain the Balmer lines predict significant Ca II, Paschen, and O I emission, roughly comparable to what is observed. However, in som e of the stars, especially at high veilings, the case for line formati on in the accretion flow is not clear. Finally, our results suggest th at the Ca II IR triplet lines are good indicators of the accretion rat e for all but the most weakly accreting T Tauri stars.