... The only criterion used for inclusion of a star in the monitoring program was that the star had to be an X--ray source. ... He also found a similar relation between rotation period and X--ray flux. ... Thus, one is more likely to find periods for either more massive or more active stars. ... Because of this, the data are not very sensitive to periods longer than 11 days. ... Taking these biases as a whole, some of the higher FAP periods listed as just below one day may be just above one day. ...