Wolff & Morrison (1975) confirmed Winzer's (1974) discovery that the magnetic CP star BX Boo (= HD 133029 = HR 5597) was variable with a period of 2.8881 days. The amplitudes of variation were 0.02 mag or less. Subsequent studies including those of Rakosh & Fielder (1978) and Borra & Landstreet (1980) have confirmed essentially this period.
Observations of BX Boo were made with the FCAPT (those in
1990-91 not being used in the analysis as they were made with
choices of filter sets which are different from the set used
subsequently). A periodogram analysis of this data showed that the
period was 
days. As a phase zero point, I adopted
2448720.181 
which is close to the light minimum and makes
phase 0.50 the light maximum. It would be useful to have an earlier
set of uvby photometry to improve the period, but
Wolff & Morrison
did not publish their values. Although comparison with
Winzer's
(1974) photometry shows that there may be a phase shift, attempts to
use this data to improve the period were not successful. In Fig. 4 (click here),
I show the FCAPT photometry plotted according to my derived
ephemeris for 1.4 periods. The single wave low amplitude light
curves are similar to those presented by Winzer and Wolff &
Morrison. The amplitudes are 0.02 mag in u and y
and perhaps 0.025 mag in v and b.
Figure 4: FCAPT uvby observations of the magnetic CP star BX Boo plotted
according to this paper's ephemeris