LINE-PROFILE VARIATIONS OF THE CLASSICAL T-TAURI STAR BP-TAURI

We have collected 51 high resolution echelle spectra of the classical T Tauri star BP Tauri during two observing periods. The spectra were s ampled on time intervals ranging from 30 minutes to several days. Simu ltaneous UBV photometric observations were made during some of the obs ervations. The Balmer lines from H alpha to H epsilon, He I lambda 587 6 Angstrom, the Na I D doublet and Ca II lambda 3933, lambda 3968, lam bda 8542, lambda 8662 Angstrom were covered within the spectral orders . From the analyses of the line variability we have found that the H a lpha and H beta emission show significant variations in both line stre ngth and profile shape on time scales from about 2 hours to days. Also the lines of Ca II, Na I and He I are variable both between and durin g single nights in equivalent widths and/or in line profiles. The prof iles of the Ca II emission lines show centrally peaked emission superi mposed on a broader, slightly blue asymmetric, emission component that appeared on different occasions. The appearance of this feature coinc ided with the appearance of a red displaced feature in the H alpha lin e. The absorption components of the Na I D doublet showed a change in their central positions from +40 to +140 km/s within a few days. From the analysis of the time scales of the variations in different parts o f the emission lines and of the correlation of the variability between different lines we conclude that the bulk of the line emission is pro duced in infalling gas. The night-to-night behaviour of the profiles s trongly support the hypothesis that the accretion flow is channeled by an inclined magnetosphere. This scenario is also supported by the sim ultaneous photometric observations carried out. In addition, the symme try of the extended H alpha line wings, the blue asymmetry of the high er Balmer lines and the longer characteristic time scales of variabili ty for the extended wings of the H alpha and H beta lines indicate tha t line emission from a stellar wind is present as well.