  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.
