During the first six years (September 1990 - July 1996) of operation of the
0.75-m Four College Automated Photoelectric Telescope (FCAPT) on Mt.
Hopkins, AZ, I obtained differential Strömgren uvby photometry of
several magnetic Chemically Peculiar stars. The dark count and then in
each filter the following measurements were obtained:
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. This paper presents observations of HD 37776, HR 2258, HR
6958, and 108 Aquarii. Table 1 (click here) gives information on the stars
(Hoffleit 1982 and Hoffleit et al. 1983) of each
group which consists of a variable along with two supposedly non-variable
stars, the comparison and check, against which the brightness of the
variable is compared. The data are given in Tables 2-5 along with their
means and their standard deviations. No corrections have been made for
neutral density filter differences among the stars of each group. The
comparison and check stars were selected from those stars in the vicinity
of the variable on the sky that had similar V magnitudes and B-V colors.
Known variables were not selected. 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.
| Star | Type | V | B-V | Spectral Type |
| HD 37776 | v | 6.96 | -0.14 | B2IV/V |
| HR 1861 | c | 5.35 | -0.19 | B1IV |
| HR 2109 | ch | 6.63 | -0.07 | B8IIIn |
| HR 2258 | v | 6.32 | -0.07 | B9IIIpSiCr: |
| 72 Ori | c | 5.30 | -0.14 | B7V |
| 64 Ori | ch | 5.14 | -0.11 | B8III |
| HR 6958 | v | 6.43 | -0.04 | A0pSiCr |
| HR 6900 | c | 6.74 | +0.02 | B9V |
| HD 172046 | ch | 6.64 | -0.04 | B8 |
| 108 Aqr | v | 5.18 | -0.10 | B9pSiSrCr |
| 106 Aqr | c | 5.24 | -0.08 | B9Vn |
| 2 Cet | ch | 4.55 | -0.05 | B9.5Vn |
Figure 1: The uvby photometry of HD 37776 using the ephemeris
JD(
. The closed squares are data from Pedersen & Thomsen and the plus
signs are FCAPT data
Figure 2: The uvby photometry of HR 2258 with the ephemeris HJD
(maximum light) = 2441254.16 + 15.0305 E. The closed squares are V
photometry of Winzer transformed to y and the plus signs are data from
the FCAPT
Figure 3: The uvby photometry of HR 6958 plotted according to HJD
(
. The FCAPT values are plotted
as plus signs and the transformed U values of Winzer
(1974) and Burke & Barr (1981) as solid
diamonds and open circles, respectively
For each variable I plotted the 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.