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\begin{document}
\IBVShead{4391}{4 November 1996}

\title{New Type and Elements for V939 Cygni}
\vspace{-2em}
\centerline{[BAV Mitteilungen Nr.\,92]}
\vskip 8mm

\begintext

V939~Cyg = S~7821 Cyg was discovered by Hoffmeister (1963) on
photographic plates of the Sonneberg Observatory. The first investigation
of this variable was performed by Gessner (1966) on photographic plates
taken with the Heidelberg Bruce-Astrograph in the years 1958 and 1959
and with Sonneberg astrographs after 1960. She classified the variable
as a W~UMa-type in the range between 12\fm 1 and 12\fm 5 and determined
first elements as:
\vskip 1mm
\hspace*{32mm}Min\,I = HJD\,2437917.62  + 0\fd558 $\times$ E \hfill (1)
\vskip 1mm

With these data V939 Cyg is listed in the fourth edition of the GCVS
(Kholopov et al.\ 1985). Since then the variable
has not been observed, until we put V939 Cyg on our observing
program. The observations were made with SBIG ST6 CCD-cameras without
filters, attached to a 32\,cm RC telescope (W.M.) and a 20\,cm SC
telescope (F.A.). GSC 3942.1581 served as comparison star and several
other stars in the same field were used to check its constancy. The
individual measurements can be requested via e-mail.
\epsfysize=9cm
\centerline{\epsffile{4391-f1.ps}}
\centerline{Figure 1. Differential light curve of V939~Cyg drawn with the new
ephemeris (2)}
\vfill \eject

\centerline{2}
\vskip 1mm

\begin{center}
Table 1. Heliocentric times of CCD-measured maxima for V939~Cyg,
 epochs and residuals computed with respect to the ephemeris (2)
 derived in this paper
\vskip 3mm
\begin{tabular}{rrll}
\hline 
JD hel.&{Epoch} & O$-$C & Observer \\
\hline
2449788.5612 &    0 &     +0.0026   & Moschner \\
49789.7173&       3 &     $-$0.0039 & Moschner \\
49793.599\ \ &      13 &    +0.002     & Agerer \\
49800.572\ \ &      31 &     $-$0.000  & Agerer \\
49933.502\ \ &     374 &     +0.005    & Agerer \\
50027.2695&     616 &     $-$0.0104 & Moschner \\
50152.4536&     939 &     +0.0000   & Moschner \\
50195.4748&    1050 &     +0.0049   & Moschner \\
50300.4915&    1321 &     $-$0.0003 & Agerer \\
\hline
\end{tabular} 
\end{center}
\vskip 7mm
A period analysis program, based on the algorithm of
Schwarzenberg--Czerny (1989) resulted in a period much shorter than
the GCVS period. As our CCD observations show, the variable is of
RR~Lyr type (see Figure 1). In our instrumental system the amplitude of variability is 0\fm45 and M$-$m = 0\fp32.

On the basis of maxima observed in the years 1995 and 1996 (listed in Table 1), using a least squares fit, we calculated the new, preliminary elements:
 \vskip 1mm
\hspace*{32mm}Max = HJD\,2449788.5586 + 0\fd 3875346 $\times$ E \hfill (2)
\hspace*{78mm}$\pm$3\hspace*{19mm}$\pm$5
\vskip 1cm

\beginauthors
\authorsrightcol 
 F.~AGERER
 W.~MOSCHNER
 Bundesdeutsche Arbeitsge\-mein\-schaft
 f\"ur Ver\"anderliche Sterne e.V. (BAV)
 Munsterdamm 90,
 D-12169 Berlin, Germany
E-mail:
agerer.zweik@t-online.de                           %email

wolfgang.moschner@t-online.de                      %email
\endauthors

\references

Gessner, H.: 1966, {\it Ver\"offentlichungen der Sternwarte in Sonneberg}, {\bf 7}, 61
%Original: Gessner, H.: 1966, {\it Ver\"offentlichungen der Sternwarte in Sonneberg}, {\bf 7}, 65
%Modified: Tue Sep 27 10:54:08 MEST 2005

Hoffmeister, C.: 1963, {\it Astronomische Nachrichten}, {\bf 287}, 169

Kholopov, P.~N.~et al.: 1985, General Catalogue of Variable Stars,
4th Edition, Nauka, Moscow

Schwarzenberg-Czerny, A.: 1989, {\it Monthly Notices R. Astr. Soc.},
 {\bf 241}, 153

\end{document}

