\documentstyle[twoside, epsf]{article}

\input ibvs2.sty
\input ibvst.sty

\begin{document}

\IBVShead{5144}{25 July 2001}

\IBVStitletl{The First Ground-Based Photometric}{ Observations of GM Draconis}

\IBVSauth{\c{C}\.{i}\c{c}ek, C.$^{1}$; Dem\.{i}rcan, O.$^{1}$; Erdem, A.$^{1}$; \"Ozdem\.{i}r, S.$^{1}$; Bulut, \.{I}.$^{1}$; Soydugan, E.$^{1}$; \\ \indent Soydugan, F.$^{1}$; Kesk\.{i}n, V.$^{2}$}

\IBVSinst{\c{C}anakkale Onsekiz Mart University, Faculty of
Arts and Sciences, Department of Physics, \\ \indent TR-17100 \c{C}anakkale, Turkey, email: canerk@bornova.ege.edu.tr, demircan@comu.edu.tr}

\IBVSinst{Ege University, Faculty of Science, Department of
Astronomy and Space Sciences, TR-35100 \.{I}zmir,
Turkey}

\SIMBADobj{GM Dra}

\begintext

\IBVSTnam{GM Dra = BD +58\deg 1721 = HIP 84837 = HD 238677}

\IBVSTcoo{17\hr20\mm21\fsec89}{+57\deg58\arcm26\farcs92}{2000}

\IBVSTobs{T\"{U}B\.{I}TAK (Scientific and Technical Research
Council of Turkey) National Observatory, 40-cm Cassegrain
telescope}

\IBVSTdet{Hamamatsu, R 4457 (PMT)}

\IBVSTfil{Johnson $B$, $V$ and $R$}

\IBVSTcomp{BD +58\deg1716}

\IBVSTchk{BD +58\deg1730}

\IBVSTsysn

\IBVSTdata{Upon request}

\IBVSTtyp{ EW }

\IBVSfig{12cm}{5144-f1.eps}{The light and color curves of GM Dra}

\begin{table}
\caption{Photometric minima times of GM Dra}
\begin{center}
\begin{tabular}{lcrl}
\hline
JD Hel. & Min & \lower6pt\hbox{$O-C$} & \lower6pt\hbox{Reference}\\[-3pt]
2400000\,+ & Type & \\
\hline
48500.1791 & I & $-0.0001$ & HIPPARCOS ESA (1998) \\
51743.4579(3) & II & $0.0011$ & This work \\
51750.3999(7) & I & $-0.0011$ & This work \\
\hline
\end{tabular}
\end{center}

\bigskip

\caption{The light levels and their differences in the light
curves of GM Dra}
\begin{center}
\begin{tabular}{lrrr}
\hline
& \multicolumn1c{$B$} & \multicolumn1c{$V$} & \multicolumn1c{$R$} \\
\hline
Max.~light at $0.75$ & $-0.665$ & $-0.708$ & $-0.735$ \\
Max.~light at $0.25$ & $-0.685$ & $-0.715$ & $-0.743$ \\
Min.~light at $0.00$ & $-0.404$ & $-0.462$ & $-0.507$ \\
Min.~light at $0.50$ & $-0.413$ & $-0.470$ & $-0.510$ \\
$\Delta$max.~($m_{0.75}-m_{0.25}$) & $0.020$ & $0.007$ & $0.008$ \\
$\Delta$min.~($m_{0.00}-m_{0.50}$) & $0.009$ & $0.008$ & $0.003$ \\
Depth of Min.~I & $0.271$ & $0.250$ & $0.232$ \\
Depth of Min.~II & $0.262$ & $0.242$ & $0.229$ \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSTrem{
The variability of GM Dra was first discovered by HIPPARCOS (ESA,
1998). The photometric observations of the system by HIPPARCOS show a
$\beta$ Lyrae type light curve with an amplitude of 0\fmm27 ranging
from 8\fmm77 to 9\fmm04. The mean orbital period derived by HIPPARCOS
from the best light curve fit is 0\fday338736 and the epoch is given as
HJD 2448500.1791 (ESA, 1998). The spectral type of the system is given
as F8.\\
The first ground-based photometric observations of GM Dra were made on
3 nights during 2000 observing season. The instrumental differential
$B$, $V$ and $R$ light and $B-V$ and $V-R$ color curves are shown in
Figure~1. During the observations, we obtained one primary and one
secondary times of minimum light. These times of minima and their
errors, which were determined by using the method of Kwee \& van
Woerden (1956), are presented in Table~1. The times of the minima
given in Table~1 are averaged values of the eclipse times obtained in
$B$, $V$ and $R$ colors during the same observing night. We have
combined the epoch derived by HIPPARCOS with our values in order to
derive the new epoch and period of the system and calculated the
following improved light elements by using the least squares method:
$$
{\rm HJD_{min\,I}} = 2451750.4010(11) + 0\fday3387412(2) \times E.
$$
The $O-C$ values in column 3 in Table~1 were calculated using the
ephemeris given in this formula.\\
The photometric phases in Figure~1 were calculated with this formula.
The shape of the light curves of GM Dra in Figure~1 is a typical of EW
type, although it was noted to be EB type in HIPPARCOS (ESA, 1998). An
asymmetry between the light level of maximum I (0.25 phase) and that of
maximum II (0.75 phase), is clearly seen in the $B$ light curve, but
not seen in the $V$ and $R$ light curves (see Table 2). There are
irregular variations in the $B-V$ and $V-R$ color curves in the
Figure~1. Especially, there is a significant blueing at about 1.3 phase
in the $B-V$ color curve and a significant reddening at about 1.38
phase in the $V-R$ color curve.}

\IBVSTack{We would like to present our thanks to the T\"{U}B\.{I}TAK
National Observatory for partial financial and equipment support. We
also would like to present our thanks to the Research Fund of
\c{C}anakkale Onsekiz Mart University for partial financial support.}

\references

ESA, 1998, The Hipparcos \& Tycho Catalogues, SP--1220

Kwee, K.K., and van Woerden, H., 1956, {\it B.A.N.}, {\bf 12}, 327

\end{document}
