I present differential Strömgren photometry of the Mercury-manganese (Hg-Mn) binary star AR Aurigae and of the magnetic CP stars 49 Cancri, 3 Hydrae, and BX Bootis obtained during the six years (September 1990 - July 1996) of the 0.75-m Four College Automated Photoelectric Telescope (FCAPT) on Mt. Hopkins, AZ. These results are part of a continuing program (see, e.g. Adelman 1993) devoted to obtaining high quality periods and light curves in the four Strömgren bandpasses. Precise rotational period of magnetic CP stars are needed when detailed studies are made of these stars, for example of magnetic fields and abundance distributions in their photospheres. Comparison of light curves taken at different epochs are important for understanding these stars.
| Star | HD Number | Type | V | B-V | Spectral Type |
| AR Aur | 34364 | v | 6.14 | -0.06 | B9.5 V |
| 18 Aur | 34499 | c | 6.49 | +0.24 | A7 V |
| 19 Aur | 34578 | ch | 5.03 | +0.26 | A5 II |
| 3 Hya | 72968 | v | 5.72 | -0.03 | Ap1SrCrEu |
| HR 3437 | 73997 | c | 6.63 | -0.02 | A1 Vn |
| HR 3342 | 71766 | ch | 6.00 | +0.42 | F2 III |
| 49 Cnc | 74721 | v | 5.66 | -0.11 | A1pEuCr |
| 34 Cnc | 72359 | c | 6.46 | -0.02 | A1 IV |
| 50 Cnc | 74873 | ch | 5.87 | +0.11 | A1 V |
| BX Boo | 133029 | v | 6.37 | -0.14 | B9pSiSrCr |
| 47 Boo | 133962 | c | 5.57 | -0.00 | A1 V |
| 38 Boo | 130945 | ch | 5.74 | +0.48 | F7 IV |
After the dark count, the telescope obtained measurements of 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 (click here) contains information on each group, a variable along with two supposedly non-variable stars, the comparison and check, against which the brightness of the variable is compared (Hoffleit 1982). Tables 2-5 present the data with their yearly means and standard deviations. Corrections were not made for neutral density filter differences among the stars of each group, each of which had one star with a different neutral density filter. The comparison and check stars were selected 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 2-5 of the check-comparison star differences indicate that these stars are constant at least for the period when they were observed.
For each magnetic CP star I plotted each variable's data using the best published period to see if the data approximately confirmed this period. Then I used the Scargle periodogram (Scargle 1982; Horne & Baliunas 1986) and considered my data and those of other observers separately in calculating periodograms. If the periodograms confirmed the published period, then I adjusted the period to make all data coincide as well as possible in phase.