SIMBAD references

We present results from a rotation period study of 21 pre-main-sequence stars in the Upper Scorpius OB association. Eleven stars have periodic variability consistent with stellar rotation. We discuss the period-searching methods and false-alarm probability calculations. Since the pre-main-sequence population of the Upper Sco region has not been examined as thoroughly as those of other star-forming regions, we compare our results with the Taurus-Auriga and Trapezium star-forming regions. We note a different distribution of P_rot in Upper Sco. We use the P_rot distribution to estimate the stellar spin-up times in this association.