Photometric monitoring of the ROSAT selected weak-line T Tauri stars in   the Taurus-Auriga field
  We monitored the light variations of 22 weak-line T Tauri stars (WTTS) discovered among the X-ray sources in the field of the Taurus-Auriga cloud. The photometric variability of 12 out of these WTTS samples is confirmed. They are all proved to be in periodic variations. By using the methods of the Phase Dispersion Minimization (PDM) and Fourier analysis, the rotational periods of these stars were determined based on this observation. Most of them are found to be shorter than one day. This gives further evidences for the spin up of solar-type stars as predicted by models of angular momentum evolution of pre-main sequence stars. 
Li-Feng Xing, Xiao-Bin Zhang and Jian-Yan Wei