1 Introduction

I examine differential Strömgren uvby photometry of four Chemically Peculiar (CP) stars obtained during the two years after Four College Automated Photoelectric Telescope (FCAPT) was moved to Washington Camp, AZ (October 1996-July 1998) and during its last year on nearby Mt Hopkins, AZ (October 1995-July 1996). The telescope obtains the dark count and then measures 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 information (Hoffleit 1982; Hoffleit et al. 1983; Schneider 1986) on each variable as well as on the two supposedly non-variable stars, the comparison and check, against which the brightness of the variable is compared. Table 2 summarizes the yearly and ensemble means and standard deviations, v-c and ch-c for the four magnitudes for HD 15980 and 33 Gem. Tables 3-6 present the data for all stars. Corrections were not made if neutral density filters were used for one or two of the stars of each group.

  

Table 1: Photometric groups

  

Table 2: Summary of uvby photometry for HD 15980 and 33 Gem

Notes: ¹ With HD 48097 as the comparison star and HD 47863 as the check star. ² With HD 47863 as the comparison star and HD 49059 as the check star.

FCAPT studies of the magnetic Chemically Peculiar (mCP) stars have both improved periods and better defined the shapes of their light curves (see, e.g. Adelman 1997). From such studies one can relate observations taken at different times, check whether such stars have variable light curves, gain some information on the uniformity of the surface abundances, and study the distribution of periods. But a few such stars have been found to be constant, as have Mercury-Manganese and metallic-line stars. Hipparcos satellite data have been used to confirm such variability studies.