\documentstyle[twoside,epsf]{article}

\input ibvs2.sty
\begin{document}
\IBVShead{4750}{16 August 1999}

\IBVStitletl{CCD Photometry of the Eclipsing Binary V1193 Cygni}

\IBVSauth{ROGER DIETHELM$^1$, MAREK WOLF$^2$}

\IBVSinst{Astronomical Institute, University of Basel,
CH - 4102 Binningen, Venusstrasse 7, Switzerland\\
\indent E-mail: {\tt diethelm@astro.unibas.ch}}

\IBVSinst{Astronomical Institute, Charles University Prague,
CZ-180 00 Praha 8, V Hole\v{s}ovi\v{c}k\'ach 2, Czech Republic\\
\indent E-mail: {\tt wolf@mbox.cesnet.cz}}

\SIMBADobj{V1193 Cyg}

\begintext

The eclipsing binary V1193 Cygni (= S 7895 Cyg = GSC 3949.0797 = FL 3046;
$\alpha = 20\hr21\mm11\fsec48$, $\delta = +59\deg36\arcm3\farcs5$, J2000; $V_{\rm max} = 12.7 mag$) was discovered photographically in the field of the star 33 Cygni by Hoffmeister (1963) in Sonneberg. Later Gessner (1966) recognized the W~UMa-type and derived the first light elements of low accuracy
\begin{equation}
{\rm Pri.~Min. = HJD}~2\,437\,668.228 + 0.674 \times E.
\end{equation}
The CCD photometry of V1193~Cyg presented here was carried out during eight nights in August and November 1998 at the R. Szafraniec Observatory, Metzerlen, Switzerland, with the 35-cm Schmidt-Cassegrain telescope and an unfiltered CCD camera (SBIG ST-6). Additional measurements were done
during the night of JD 2451361 with the same equipment. The standard error of the measurements varies from 0.01~mag to 0.02~mag. The stars GSC~3949.0039 ($V = 11.0$~mag) and GSC~3949.0271 ($V = 12.1$~mag) on the same frame as the variable served as comparison and check star, respectively (Figure 1). It is also remarkable, that V1193~Cyg is superimposed on a faint galaxy ($\sim$ 16 mag), whose nucleus lays slightly west of the 
variable. This galaxy as well as V1193 Cyg could be also identified 
with the source IRAS 20201+5926 ($\alpha = 20\hr21\mm12\fsec8$, $\delta = +59\deg36\arcm19\arcs$, J2000).
Altogether 247 frames of this field were obtained and analysed.
Table~1 contains three new epochs for minima, $N$ denotes the 
number of measurements used for the precise determination of minimum time.

\IBVSfig{10cm}{4750-f1.ps}{Finding chart of V1193~Cyg with the size of the field $8 \times 6$ arcmin.}

\IBVSfig{10cm}{4750-f2.eps}{Composite light curve of V1193~Cyg for the period of 0.50376471 days.} 

\begin{table}
\begin{center}
\caption{Times of minimum of V1193~Cyg.}
\medskip
\begin{tabular}{lrrc}
\hline
HJD $-$ & Epoch & Epoch & \\ 
2\,400\,000 & Gessner (1966) & this paper & \\ 
\hline 
37668.228 & 0.0 & 0.0 & \\
37669.224 & 1.5 & 2.0 & \\
37898.455 & 341.5 & 457.0 & \\
37906.516 & 353.5 & 473.0 & \\
37917.585 & 370.0 & 495.0 & \\
37944.557 & 410.0 & 548.5 & \\
37964.441 & 439.5 & 588.0 & \\
38348.316 & 1009.0 & 1350.0 & \\ 
\hline
& Error & \raise-6pt\hbox{Epoch} & \raise-6pt\hbox{$N$} \\[-6pt]
& [days] & & \\ \hline
51052.3768 & 0.0003 & 26568.5 & 38 \\
51107.2871 & 0.0005 & 26677.5 & 12 \\ 
51361.4369* & 0.0011 & 27182.0 & 14 \\
\hline
\end{tabular}

{* \it published also in BBSAG Bull.\ No.\ 120}
\end{center}
\end{table}

\vskip-24pt

Our CCD observations confirm the W~UMa-type of this eclipsing binary, but we find a substantially shorter orbital period of about 0.50376 days. This period also fits the minima of Gessner (1966) better, the corresponding new cycle counts are given in Table~1. A recalculation of the light elements using the 8 original times of minimum published by Gessner (1966) and 
our new epochs gives the following result: 
\begin{equation}
{\rm Pri.~Min. = HJD}~2\,437\,668.2323 + 0.5037599 \times E. 
\end{equation}
Our photoelectric light curve was solved independently 
using a method of treating photometric data described by 
Mikul\'a\v{s}ek at al. (1995), which is a weighted LSM iterative 
procedure. Using this method we derive the current light elements, 
which could be used in the near future:
\begin{equation}
\begin{array}{r@{}r@{}l}
{\rm Pri.~Min. = HJD}~2\,451\,361.4371 & {} + 0.50376471 & {} \times E. \\ \pm 0.0001 & \pm 0.00000005 \\
\end{array}
\end{equation}
Figure~2 shows the light curve folded with this period. The light amplitude for the primary minimum according to our measurement is $A_1 = 0.41 \pm 0.03$ mag, for the secondary minimum we find $A_2 = 0.33 \pm 0.01$ mag.

The difference of both derived periods ($\sim 5 \times 10^{-6}$ day) and a number of epochs elapsed since the first observations ($\sim 27\ 000$) gives value of 0.135 days, which is smaller than the value of period $P$ or $P/2$. Our newly determined epochs and the cycle count given in Table 1 is correct, which might hints towards the existence of a period change in the time interval between Gessner's data and ours. Further observations of this eclipsing system are necessary in order to establish a better value of the orbital period and/or its probable changes. Also, an investigation on photographic plates could help solve this questions.

\bigskip
{\it Acknowledgements.} This work has been supported in part by the Swiss National Science Foundation. M.W. is very grateful for the use of the facilities and the hospitality at the Astronomical Institute of University Basel in the August 1998. R.D. wishes to thank the ``Emilia Guggenheim-Schnurr Foundation'' for financial support.

\references
Gessner H., 1966, {\it Ver\"off.\ Sternwarte Sonneberg}, {\bf 7}, 65

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

Mikul\'a\v{s}ek Z., Han\v{z}l D., Hornoch K., 1995, {\it Contributions
of Nicholas Copernicus Observatory Brno}, {\bf 31}, 43

\endreferences

\newpage

\IBVStitle{Erratum}

\bigskip
In the Table of IBVS No.\,4612 all spectral types MS should read M5. Therefore M5 spectral type is assigned to XX~CMa, TU~Car, DL~Cen, BS~Mon, HW~Mon, W~Mus, BO~Pup, ES~Pup, AD~Vel, and NSV~5061. The original manuscript was correct. The errors occurred when the OCR software was utilized. With our apologies

\bigskip
\rightline{THE EDITORS\qquad}

\end{document}
