1 Introduction

Differential Strömgren photometry of three early type stars from the six years (September 1990 - July 1996) of the 0.75-m Four College Automated Photoelectric Telescope (FCAPT) on Mt. Hopkins, AZ and from the first year after the telescope was moved to nearby Washington Camp, AZ (October 1966 - July 1997) are examined. After the dark count, the telescope measured the sky-ch-c-v-c-v-c-v-c-ch-sky in each filter where sky is a reading of the sky, ch that of the check star, c that of the comparison star, and v that of the variable star. Table 1 contains group (a variable along with two supposedly non-variable stars, the comparison and check, against which the brightness of the variable is compared) information (Hoffleit 1982). Tables 2-4 present the data and their yearly means and standard deviations. Corrections were not made for neutral density filter differences among the stars of each group. The comparison and check stars were chosen from supposedly non-variable stars in the vicinity of the variable on the sky that had similar V magnitudes and B-V colors. The standard deviations in Tables 2-4 of the check-comparison star differences indicate that these stars are constant at least for the period when they were observed except for HR 7721.

  

Table 1: Photometric groups

For each group we plotted each variable's data using the best published period to see if the data approximately confirmed this period. Then we used the Scargle periodogram (Scargle 1982; Horne & Baliunas 1986) and considered our data and those of other observers separately in calculating periodograms. If the periodograms confirmed the published period, then we adjusted the period to make all data coincide as well as possible in phase.