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\IBVShead{4111}{8 November 1994}                      % Use it with dummy or empty arguments

% Call for macro \title {Title of the paper}
\title{PHOTOELECTRIC OBSERVATIONS OF AB DORADUS}

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    AB Doradus is a chromospherically active rapidly rotating single star
that has been extensively observed for over 16 years. Photoelectric 
measurements were made at Mt Molehill in November 1993 (13 \& 22) and in
January 1994 (5, 19, 27, 28 \& 30). A 200mm f10 Schmidt-Cassegrain 
Telescope, an RCA 931b P.M.T., standard Johnson B \& V filters and DC electronics
were used to make the observations. 
AB Doradus was monitored continuously in two colours,using differential 
photometry. Measurements of the comparison star and check were made regularly
at about 15 minute intervals. 

Reductions to the UBV standard system were 
carried out in accordance with the methods described by Henden and
Kaitchuck (1982).

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\centerline{Figure 1. The two light curves collected in November 1993 (top) and}
\centerline{in January 1994 (bottom). The square symbols are January 27, 28 \&30}
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\centerline{Figure 2. The B$-$V plotted against phase, November 1993 (top) and}
\centerline{Januar 1994 (bottom). The square symbols are January 27, 28 \& 30}
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\centerline{\epsffile{4111-f3.ps}}
\centerline{Figure 3. Overall light level and range of V light plotted against year.}
\centerline{Each bar gives the range and light level at the observed epochs.}
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\centerline{Table 1. Check Star HD\,37279}
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\hbox to 13cm {
\begin{tabular}{cccccc}
\hline 
     Date &             n&    V mag&  S.D.&   B$-$V &   S.D.\\
\hline
\\          
     individual nights& & & & & \\
     J.D.  2449304     &   9 &  7.425&  .009 &   0.263 & .009\\
     J.D.  2449313     &   7 &  7.425&  .005 &   0.275 & .008\\
     J.D.  2449357     &   9 &  7.433&  .011 &   0.261 & .011\\
     J.D.  2449371     &   6 &  7.438&  .004 &   0.254 & .008\\
     J.D.  2449380     &   11&  7.429&  .005 &   0.260 & .010\\
\hline
\end{tabular}}
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\centerline{S.D. = standard deviation}
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The observing sequence was sky-comp-var-comp-sky-var-check-comp-sky
etc. Check star measurements (Table 1) had a standard deviation of 0.011
or less. Each data point on the light curve is the sum of three 10 sec
integrations. Both the November and January light curves have amplitudes
of approximately 0.14 magnitudes (Figure 1).
The more complete light curve for January 1994 (Figure 1b) shows what
appears to be a second spot at phase 0.37. Figure 1 shows the amplitude of
the light curves and the phase angle of the spots in relation to each other.
There is a three hour phase shift between the November 1993 and January 
1994 light curves. This corresponds to a linear phase shift of 1\fdg 7 per
day when using the period of 0.51479 days derived by Innis et al. (1988).
By changing the period to 0.5138 days the two data sets can be brought
back into phase. The January 1994 (Figure 1b) light curve is a composite
of five nights. The rise was observed on January 5 and the fall on January
28, thirteen days apart, and the resulting light curve is distorted.
The rise and the fall on November 13, 1993 (Figure 1a) were observed during
one observing session, and therefore would be more accurate. 
The B$-$V (Figures 2a \& 2b) shows an apparent drop from 0.82 to 0.84 coinciding
with the minimum of the V light curves. 
(Figure 3) is a plot of the overall brightness and amplitude  of AB Doradus 
since 1978. Each bar gives the range and light level at the observed epochs.

Since observations started  at Mt Molehill in December of 1990 AB Doradus
has been steadily increasing in brightness, the light curves for November
1993 and January 1994 are in agreement with this.
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% Call for macros \authors - \authorsrightcol - \endauthors
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Marc BOS
Mt Molehill Observatory
83a Hutton Street, Otahuhu
Auckland, New Zealand
\endauthors

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\references

 Henden, A. A., Kaitchuck, R. H., 1982,  Astronomical Photometry, Van Nostrand
 Reinhold

 Innis, J. L.,Thompson, K., Coates, D. W., Lloyd Evans, T., 1988,
{\it Mon. Not. R. Astr. Soc.}, {\bf 235}, 1411

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