Lanz & Mathys (1990) discovered that the sharp-lined (
) hot Am prototype star o Peg (spectral type A1 IV) has a magnetic
field of order 2 kG using the Stenflo & Lindegren (1977) multiline and
another technique. Recently Savanov & Savalyeva (1996) used the former on
the spectrum of the mild Am star 15 Vul and derived a magnetic field of
about 2.4 kG. Following the example of the magnetic CP stars, one might
expect to observe spectral and light variability although in this case, the
scale size of the field, which is not detected using a standard Zeeman
analyzer (Babcock 1958), is expected to be much smaller and the field
geometry much more complex. However, despite previous claims of low
amplitude variability, Adelman (1993) showed that another prototype hot Am
star 68 Tau was not variable within an observing season.
In years 1 and 2, 15 and 30 FCAPT uvby observations, respectively,
were made of 68 Tau (= HR 1389 = HD 27962). A careful reexamination of that
data shows that observation 12 of year 1 and observations 10 and 11 of year 2
should have been omitted. In year 3 I obtained 14 new observations (Table 2).
There is no evidence of variability within a year. The data for year 3 has
smaller errors than those for previous years and for each filter the
ch-c standard deviations of the means are equal or larger than those for
v-c. The agreement of the v-c averages for years 2 and 3 is
excellent. The largest difference between the v-c values for years 1
and 2 are for v and y and are about 
which is within the
expected errors. Thus 68 Tau is photometrically constant to within the
errors of the data. It would be useful to get another year of data with
the quality of year 3 and many more observations to reduce the upper limit
on any variability. This is particularly important as 68 Tau is a blue
straggler in the Hyades.
With the use of electronic detectors for spectroscopy and the
resultant increase in the signal-to-noise ratios in the last decade or two,
one can also use high dispersion spectra to set stricter limits on the
spectral variability of supposedly non-variable stars. I found, for example,
that the 
Dominion Astrophysical Observatory spectra of 68
Tau (67 Å in length) obtained with a Reticon (pixel width 
) used in
the analysis of this star (Adelman 1994) agreed well in the regions of
overlap to within the errors expected for spectra with signal-to-noise ratios
of 200 and that 
.
In the past year 43 uvby observations of 15 Vul (= HR 7653 = HD
189849) were obtained (Table 3). The standard deviation of the mean v-c
for all four magnitudes is about 0.004 mag. while for the v-ch and
ch-c values about 0.009 mag. Thus 15 Vul is more stable than 21 Vul
and probably is constant. Bolcal et al. (1992) found it has
rather mild abundance anomalies and 
.
I obtained 23 and 2 differential uvby observations of o Peg (= HR 8641 = HD 214994) (Table 4) in the fall of 1995 and the spring of 1996, respectively. The ch-c and v-c star standard deviations about the mean for v, b, and y are typically 0.003 mag. Both values for u are 0.008 mag. Thus the variability of o Peg in the best observed filters v, b, and y is at most of order 0.003 mag.