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\IBVShead{4457}{13 March 1997}

\title{Variable Stars in the Globular Cluster NGC\,6266}

\begintext


M62 (NGC\,6266, C1658-300) is located close to the 
galactic center ($l = 353\fdg 6$, $b = 7\fdg 3$). This rather metal rich cluster ([Fe/H] = $-$1.28 (Zinn \& West, 1984)) belongs to the concentration
class CC IV, its apparent 
radius is $r=7\farcm1$ (Kukarkin, 1974) and the tidal radius 
$10\farcm5$  (Webbink, 1985). M62  is rich in variables:
89 variables were discovered in the cluster (Sawyer-Hogg, 1973), periods 
are defined for 74 of these stars. Twelve of them are classified as 
RRc and 66 as RRab variables. Values of P$_{ab}$, N$_c$/N$_{ab}$ confirm the classification 
of the cluster as OoI variable rich one.


\vskip 2mm
\centerline{Table 1. Positions and photometric data for suspected variables}
\vskip 1mm
\begin{center}
\begin{tabular}{rrrrrrrrrrr}
\hline
 $N$ & $X_{SH}$ & $Y_{SH}$ & ${\Delta}V$ & ${\Delta}B$ & & $N$ & $X_{SH}$ & $Y_{SH}$ & ${\Delta}V$ & ${\Delta}B$\\
     & (arcsec) & (arcsec) &  & & & & (arcsec) & (arcsec) &  &   \\
\hline
\\
  1 &  $-$102.5 &   $-$71.6 &   0.23 &   0.25 &   & 23 &   119.8 &    44.7 &   0.62 &   0.63 \\
  2 &   $-$73.8 &   $-$24.5 &   0.25 &   0.35 &   & 24 &   119.7 &   $-$22.7 &   0.10 &   0.08 \\
  3 &   $-$59.3 &    89.4 &   0.04 &   0.07 &   & 25 &   121.8 &     9.4 &   0.43 &   0.39 \\
  4 &   $-$57.5 &    97.5 &   0.38 &   0.31 &   & 26 &   $-$87.0 &   $-$87.3 &   0.02 &   0.23 \\
  5 &   $-$55.3 &    86.6 &   0.35 &   0.34 &   & 27 &   $-$65.9 &    71.1 &   0.11 &   0.29 \\
  6 &   $-$68.5 &  $-$119.2 &   0.05 &   0.02 &   & 28 &  $-$42.9 &   $-$84.3 &   0.48 &   0.40 \\
  7 &   $-$50.6 &    65.9 &   0.09 &   0.07 &   & 29 &   $-$31.4 &   $-$75.4 &   0.17 &   0.70 \\
  8 &   $-$50.2 &   $-$56.1 &   0.75 &   0.67 &   & 30 &   $-$20.2 &   $-$60.0 &   0.12 &   0.13 \\
  9 &   $-$33.5 &   $-$62.1 &   0.34 &   0.44 &   & 31 &    34.0 &   $-$92.7 &   0.93 &   1.24 \\
 10 &   $-$16.3 &    63.5 &   0.76 &   0.51 &   & 32 &    59.7 &  $-$106.7 &   0.54 &   0.58 \\
 11 &   $-$14.0 &  $-$118.2 &   0.16 &   0.19 &   & 33 &    89.8 &    49.8 &   0.27 &   0.29 \\
 12 &    10.3 &    87.6 &   0.22 &   0.32 &   & 34 &    91.8 &    71.7 &   0.40 &   0.47 \\
 13 &     7.8 &   $-$61.1 &   0.04 &   0.07 &   & 35 &    81.8 &  $-$115.3 &   0.13 &   0.17 \\
 14 &    22.0 &   $-$99.2 &   0.29 &   0.28 &   & 36 &    94.2 &    71.8 &   0.29 &   0.50 \\
 15 &    50.7 &    86.9 &   0.05 &   0.04 &   & 37 &    84.3 &  $-$127.5 &   0.45 &   0.35 \\
 16 &    60.1 &    67.1 &   0.19 &   0.18 &   & 38 &    88.4 &   $-$15.7 &   0.05 &   0.10 \\
 17 &    51.5 &  $-$116.6 &   0.44 &   0.37 &   & 39 &   131.6 &   $-$48.4 &   0.00 &   0.00 \\
 18 &    65.9 &    13.0 &   0.08 &   0.13 &   & 40 &   136.1 &   $-$34.5 &   0.01 &   0.02 \\
 19 &    74.6 &    42.2 &   0.05 &   0.03 &   & 41 &   144.1 &   $-$82.0 &   0.01 &   0.02 \\
 20 &    84.7 &   $-$86.4 &   0.04 &   0.03 &   & 42 &   152.9 &    $-$6.6 &   0.03 &   0.00 \\
 21 &    98.1 &    10.5 &   0.14 &   0.12 &   & 43 &   193.7 &  $-$113.0 &   0.00 &   0.02 \\
 22 &   103.5 &    48.3 &   0.35 &   0.57 &   &    &         &         &        &        \\                                                
\hline                               
\end{tabular}                        
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\centerline{2}
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\centerline{\epsffile{4457-f1.ps}}
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\normalsize
Figure 1. The color - magnitude diagram for the globular cluster NGC\,6266
corrected for different reddening, the known RR Lyrae stars are 
denoted by circles, suspected variables are marked by squares
\end{center}
\vskip 1mm

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\centerline{\epsffile{4457-f2.ps}}
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\normalsize
Figure 2. Finding chart for NGC\,6266. The known RR Lyrae stars are denoted 
by circles and by their number from the catalog of SH, suspected variables
are marked by squares
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\large
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\centerline{3}
\vskip 1mm

  This study is based on CCD observations (Brocato et al., 1996). We used the 
same method of search for RR Lyrae variables as Kadla
et al., 1996). In the investigation area ($3\farcm81 \times 6\farcm30$) 
there are  31 known variables. The identification of V1 and V13 was 
made using coordinates of SH catalog only.
They were not marked on Plate 3 of Van Agt and Oosterhoff (1959) since
the stars are situated in the crowded central part of the cluster.  Variables V2, V23 and V37 
are brighter than the other variables. In order to eliminate errors due to crowding of the central 
part of the cluster, we have not considered the region of the cluster center 
($r < 2\farcmm$ ).


  The differential reddening across the cluster field (Van Agt and Oosterhoff, 1959) causes an additional difficulty for the investigation of this cluster.

The colour--magnitude diagram after correction for  differential reddening is shown in Figure 1.
Apart from 31 known variables, there are 43 stars in the instability strip. 
All data for suspected variable stars are given in Table 1. The 
coordinates of stars in arcseconds in the system of SH's catalog and the 
maxima of magnitude variations $\Delta$B and $\Delta$V, during our observations  are listed in columns 2-5  of Table 1. In Figure 1 
and in the finding chart (Figure 2) the known and suspected variables are marked by  circles  and squares correspondingly.

Because of its position in Figure 1 we suppose that V13 is a red giant. 
The stars V2, V23 and V37 seem to be field variables.


We are grateful to the Russian Foundation for Basic Research for financial
support.

\vskip 1cm

\beginauthors  
\authorsrightcol
Yu.N. MALAKHOVA
A.N. GERASHCHENKO
Z.I. KADLA
Central Astronomical Observatory of 
the Russian Academy of Sciences at 
Pulkovo, 196140 Saint--Petersburg, 
Russia, e-mail: mal@pulkovo.spb.su
\endauthors

\references

Brocato, E., Buonanno, R., Malakhova, Yu. \& Piersimoni, A.M.,
 1996, {\it A\&A}, {\bf 312}, 80

Kadla, Z.I., Gerashchenko, A.N., Malakhova, Yu.N., 1996, {\it IBVS}, No.\,4413

Kukarkin, B.V., 1974, The General Catalogue of Globular Clusters 
 of our Galaxies. Publishing House Nauka, Moscow

Sawyer-Hogg, H., 1973, {\it Publ. David Dunlap Obs.}, {\bf 3}, No.\,6 [SH]


Van Agt, S., Oosterhoff, P.Th., 1959, {\it Leiden Ann.}, {\bf 21}, 253

Webbink, R.F., 1985, IAU Symposium No.\,113, 541
    eds by J. Goodman \& P. Hut, Reidel, Dordrecht

Zinn, R., West, M.J., 1984, {\it ApJSS}, {\bf 55}, 45

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