Alencar, Silvia H. P.

Contact Email: alencar@iagusp.usp.br
Institute: Astronomy Department - IAG - University of Sao
Paulo
First Coauthor: Celso Batalha
Subject Area: Star Formation, Very Young Stars, T-Tauri, H-H Objects
Waveband: Optical
Technique: Spectroscopy
Presentation: Oral Contribution: Monday
Title: The spectral variability of TW Hya, a 10 Myr old classical T Tauri star
Abstract: We present the analysis of 50 spectra of the Classical T Tauri star TW Hya observed with the FEROS echelle spectrograph over the last two years. The star exhibits strong emission lines that show a variety and variability in profile shapes. The system shows periodic variations in line and veiling intensities that are consistent with magnetospheric accretion models with an inclined dipole field. Our results suggest the system is viewed at low inclinations ( $i < 20\deg$), in agreement with recent imaging results of the TW Hya circumstellar disk. TW Hya presents typical spectral characteristics of the low mass accretion rate stars in Taurus. A comparison of the observed NaD lines with the predicted magnetospheric accretion profiles seem to point to a variation in the mass accretion rate over a 1 year period (from 10^-8 to 10^-9 M$_\odot$ ${\rm yr}^{-1}$). Winds can become important in this system and seem to be related to the accretion process. Our results indicate that active accretion disks can survive up to 10 Myr without changing much, which is rather surprising.