THE SPECTRAL VARIABILITY OF THE T-TAURI STAR DF-TAURI

We analyze 117 echelle spectra of the T Tauri star DF Tau, concentrati ng on variations in the optical continuum veiling and the strong emiss ion lines. Although this star was the inspiration for the original sug gestion of magnetospheric accretion in T Tauri stars (TTSs), this hypo thesis is only partially supported in our data. We find that variation s in the Ca II infrared triplet lines correlate with the veiling varia tions; there is some evidence that the broad component of the He I lin e does, too. The narrow component of He I is shown to arise at the ste llar surface, but it correlates with the broad component. There is a s urprising lack of periodicity in the lines, and it does not occur wher e expected when seen. The correlation between continuum veiling and th e line components expected to be most related to the veiling is poor. There is a great deal of variability in all the lines and line compone nts; a snapshot spectrum is a poor way to characterize the star as a w hole. The total Balmer line fluxes are poorly correlated with the veil ing, unlike previous results on a large sample of TTSs. Redshifted abs orption components are found in the weaker lines but are not common. T he strength of the blueshifted absorption feature in H alpha is correl ated with the veiling, but changes in it perhaps occur before veiling changes by about one day. This time delay supports the idea that the w ind originates at some distance for the stellar surface and is related to accretion. Spherically symmetric wind models are unable to reprodu ce well the relative absorption levels on the blue side of the H alpha and H beta lines simultaneously. H alpha does not display the asymmet ries expected of magnetospheric accretion, but it is sometimes suggest ive of azimuthally asymmetric corotating structures. The lines wings i ndicate that the formation region of the H alpha lines is dominated by high turbulence. H beta does show more of the asymmetry expected of m agnetospheric accretion.