Magnetospheric Accretion and Winds on the T Tauri Star SU Aurigae: Multi-Spectral Line Variability and Cross-Correlation Analysis

Abstract

SU Aurigae is a T Tauri star that was well monitored during the MUSICOS 96 multi-site campaign. We present the results of the spectroscopic analysis of the circumstellar environment of this star, particularly of the Halpha, Hbeta, Na I D and He I D3 line profiles. The signatures of modulated outflows and mass accretion events are analysed, as well as transient spectral features. We compute the cross-correlation function (CCF) of several pairs of (velocity bins in) spectral lines to better investigate the profiles' temporal variability. We found increasing time lags between the variability of He I D3, Na I D and Hbeta. We propose this may be understood in terms of azimuthal distortion of the magnetic field lines due to the different rotation rates of the star and the disk. We find the slightly blueshifted absorption features in Halpha, Hbeta and Na I D to be anti-correlated with the accretion flow signatures. We propose that the transient absorption features in the blue wings of Halpha, Hbeta and Na I D (signatures of mass outflows), and flare brightenings are related to the disruption of distorted magnetospheric field lines.