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\IBVShead{4153}{31 January 1995}                      % Use it with dummy or empty arguments

% Call for macro \title {Title of the paper}
\centerline{\ft PHOTOELECTRIC OBSERVATIONS OF THE ECLIPSING}
\centerline{\ft VARIABLE DO Cas}
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\begintext

  During the 1992 observational season we turned our attention 
  to the eclipsing variable star DO Cas (SAO\,12388), in order to check 
  the correctness of the ephemeris reported in the literature 
  and to obtain the entire light curve.
  
  The photoelectric observations were carried out at the station of Capanne 
  di Cosola (AL, Italy) for six nights spanning from August 26 to September 
  4, collecting a total of 573 points in the instrumental V filter. 
  The adopted photometric device was an OPTEC SSP5 photoelectric photometer 
  (spectral sensitivity S-5) attached to a 200 mm Schmidt-Cassegrain f15
  telescope. The integration time was fixed to ten seconds per count.
  The adopted comparison star was HIC\,1228 (SAO\,23474), the check one was 
  HD\,15963 (SAO\,23451).
  The data of the involved stars are listed in the Table 1.

  We obtained 4 heliocentric times of minimum, two primary and two 
  secondary ones, listed in Table 2. 
  These moments of minimum have been obtained processing the
  data by the Minimum Entropy SOP procedure (MEMSOP, Gaspani, 1993).
  Table 2 shows the residuals computed with respect to the following
  ephemeris:
  \vskip 2mm					      
  \centerline{Min.I = J.D.(hel) 2433926.4573 + 0\fd 6846661$\times$E}
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  \noindent listed by the General Catalogue of Variable Stars (Kholopov et al.,
  1985).
  The values of the residuals suggest that the ephemeris listed above is
  still valid, the phase curve obtained using this ephemeris is
  shown in Figure 1.

  In order to recover a convenient estimate of the true signal from the
  noisy phased data we processed them by a signal recovery technique based
  on an artificial neural network implementing a multilayer perceptron
  according to Haykin (1994), Masters (1994) and others.
  The restored signal is graphed as a solid line, across the original data
  points, in Figure 1.
  The flat secondary minimum is well evident.
  A further analysis of our observations in view to solving the light
  curve and determining the orbital parameters of the binary system is in 
  progress.

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\centerline{Table 1. Data of the involved stars}
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\small
\begin{center}
\begin{tabular}{lllrrl}
\hline
 &RA (2000)&Decl. (2000)&V\ \ \ \ \ &B$-$V&Sp.\\
\hline
\\
DO Cas (HIC\,12543=BD+59\degr 529&02\fh 41\fmm 24\fs&+60\degr 33' 11''&8.39-9.01&0.11&A4V\\
=HD\,16506=SAO\,12388)& & & & & \\
\\
HIC\,1228 (BD+59\degr 521=&02\fh 37\fmm 26\fs&+60\degr 05' 18''&7.407&1.129&F0III \\
HD\,16088=SAO\,23474)& & &$\pm$0.031&$\pm$0.015& \\
\\
HD\,15963 (SAO\,23451)&02\fh 36\fmm 12\fs&+58\degr 04' 32''&8.03&0.06&A2Ib\\
\hline
\end{tabular}
\end{center}
\large
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\centerline{2}
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\centerline{\epsffile{4153-f1.ps}}
\centerline{Figure 1. Photoelectric observations of DO Cas (open squares). The}
\centerline{solid line is the signal restored by neurocomputing techniques.}
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\centerline{Table 2. Observed times of minimum}
\vskip 1mm
\begin{center}
\begin{tabular}{clccr}
\hline
      Date  &\ \ Epoch &     Times of minimum &    Residual&   Type\\
	    &\ \ \ \ E &     Heliocentric J.D.&     O$-$C  &       \\
\hline
\\
     27 Aug. 1992&   21815  &   2448862.450$\pm$0.014 &   +0.002    &  I\\
     1 Sep. 1992&   21822.5&   2448867.572$\pm$0.020 &   $-$0.011  &   II\\
     2 Sep. 1992&   21824  &   2448868.620$\pm$0.003 &   +0.010    &  I\\
     3 Sep. 1992&   21825.5&   2448869.628$\pm$0.003&   $-$0.009  &   II\\
\hline
\end{tabular}
\end{center}

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% Call for macros \authors - \authorsrightcol - \endauthors
\beginauthors
Marco ALUIGI
GEOS - 3, Promenade Venezia,
F-78000 Versailles (France)
\authorsrightcol
Gianni GALLI
GEOS - 3, Promenade Venezia,
F-78000 Versailles (France)
\endauthors
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\centerline{Adriano GASPANI}
\centerline{Osservatorio Astronomico di Brera}
\centerline{Via Brera 28, Milano (Italy)}
\centerline{and}
\centerline{GEOS - 3, Promenade Venezia,}
\centerline{F-78000 Versailles (France)}
\centerline{e-mail: gaspani@bach.mi.astro.it}

% Call for macro \references
\references

Kholopov et al., 1985, ``General Catalogue of Variable Stars" (GCVS), 
    Moscow
    
Gaspani A., 1993: ``The algorithms useful in finding the extrema of
    the light curves". Final Report of the Second GEOS Workshop 
    on the Eclipsing Variable Stars and their Data Processing", 
    S.Pellegrino Terme (Italy), 1993, 21-22 May
    
Haykin S., 1994: ``Neural Networks, A Comprehensive Foundation", Macmillan
    College Publishing Company Inc., p. 498
    
Masters T., 1994, ``Signal and Image Processing with Neural Networks",
    J. Wiley, New York


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