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\IBVShead{4280}{19 December 1995}

\title{SMALL-AMPLITUDE VARIABLES IN THE OPEN CLUSTER IC\,4665}
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\begintext

     The open cluster IC\,4665 (r = 364 pc) is known to have a high
percentage of  spectral  binaries  among  its  bright members (Abt
et al., 1972; Grampton et al., 1976).  With the purpose of detecting
these binaries   eclipsing   variables, we  performed  in  1984  a
photoelectric B,V monitoring, using the  60-cm  telescope  of  the
Maidanak Observatory.  However, no  sign  of  light  weakening was
detected in the moments of expected minima  (Zakirov, 1987).  This
photoelectric material has been recently used by us to search for
periodic small-amplitude  variations  in  the  brightness  of  the
observed binaries.  As  a  result, the periods of light variations
have been discovered for five  stars, which  are  given  in
Table 1. Here, star  names  are  taken  from  the  list  of Kopff
(1943), and in the column P(Sp), spectroscopic period is given according
to Abt et al. (1972). The  value  k is the average signal-to-noise
ratio. Light  curves of these stars are displayed in Figures 1-5.
The  periods  of the binaries are close to, or multiple of, P(Sp). 
We conclude that these light variations are related to the effect 
of axial rotation or orbital motion of the components rather than of
eclipse in the double systems.
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\centerline{Table 1}
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\begin{tabular}{lccccclll}
\hline
    Kopff& HD  & Max  &   A  &   k  &$\langle$B$-$V$\rangle$&     P& P(Sp) &  Sp\\
\hline
\\
 
    32  & 161261 &8\fm 290 & 0\fm 017 & 2\fm 19 &  0\fm 057 & \ 1\fm 60  &\ 8\fm 23 &   B8+Shell\\
    64   &161603 &7.366 & 0.021 & 2.82 &  0.040 &   41.5  &  43.5 &   B5IV\\
    72   & 161660&7.759 & 0.017 & 2.15 &  0.012 &  15.61  & 15.58 &   B7V\\
    76AB & 161698&8.214 & 0.028 & 2.69 &  0.120  & 15.42  & \ 7.25 &   B8.5p\\
    105  & 162028&7.517 & 0.022 & 1.95 &  0.027  & 15.05  & \ 8.01 &   B6V\\
\hline
\end{tabular}
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\centerline{Figure 1. The light curve for star 32.}
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\centerline{2}
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\centerline{Figure 2. The light curve for star 64.}
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\centerline{Figure 3. The light curve for star 72.}
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\centerline{Figure 4. The light curve for star 76.}
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\centerline{3}
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\centerline{Figure 5. The light curve for star 105.}

    One of   us   (MMZ)   was   supported   by   Fund for Fundamental
Research of Republic Uzbekistan (Contract 33).
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\beginauthors
\authorsrightcol
Mamnun M. ZAKIROV
Gurgen C. ARZUMANYANTS
Mt.Maidanak Observatory of
Astronomical Institute
Astronomicheskaya,33
Tashkent, 700052, Uzbekistan
E-mail:mzakirov@silk.glas.apc.org
\endauthors

\references
   
Abt H.A., Bolton C.T., Levy S.G., 1972, {\it Astrophys. J.}, {\bf 171}, 259
    
Grampton D., Hill G., Fisher W.A., 1976, {\it Astrophys. J.}, {\bf 204}, 502
    
Kopff E., 1943, {\it Astron. Nachr.}, {\bf 274}, 69
    
Zakirov M.M., 1987, {\it Kinematika i Fiz. Nebesn. Tel.}, T.3, N1, 25

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