Periodic variability in the emission spectrum of T Tauri

Context. Long timescale periodic variations in T Tauri stars may be related to changes in their protoplanetary disks. Aims. A lengthy homogeneous series of spectral observations of the CTTS T TauN has been analyzed. Methods. We search for periodicity in the equivalent widths of the emission lines in the optical and in the UV. Results. Significant periodic variation is found in the equivalent widths of Hβ and CaII emission features on a time scale of 33 ± 1.5 days. Variations in the UV emission lines based on archival IUE spectra are also consistent with this period. Conclusions. This is clearly not the rotation period of the star, which is known to be 2.8 days, and must arise somewhere in the magnetosphere, disk or outflow region