Preston (1970) included the sharp-lined B9p star HD 200311 (
) in a list of CP stars that may have long
periods. A high dispersion line identification study (Adelman
1974) and spectrophotometry (Adelman 1980) both show that
this is an interesting magnetic star.
During years 2 through 5, 157 uvby observations of HD
200311 were made with the FCAPT. The periodogram showed
two possible periods 1.037 and 26.0042 days. As on some nights
two sets of photometric observations were made and as HD
200311 is a sharp-lined star, I was able to exclude the shorter
period. The period is a relatively long one which is consistent
with Preston's 
value. The observations are phased
according to
Figure 4 (click here) shows that with this ephemeris HD 200311 exhibits an in-phase variability of u, v, b, and y with amplitudes, respectively, of 0.035 mag, 0.030 mag, 0.030 mag, and 0.025 mag. There are possibly some slight differences between the light curves, but these require additional observations.