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\IBVShead{4990}{1 December 2000} 
 
\IBVStitletl{BV-Photometry and the First Ephemeris}{ of the Eclipsing Binary System GV\,D\lowercase{ra}} 
 
\IBVSauth{Dallaporta, Sergio$^1$; Tomov, Toma$^{2,3}$; Zwitter, Toma\'z$^4$; Munari, Ulisse$^{2,3}$}

\IBVSinst{Via Filzi 9, I-38034 Cembra (TN), Italy} 
\IBVSinst{Osservatorio Astronomico di Padova, Sede di Asiago, I-36032 Asiago (VI), Italy} 
\IBVSinst{CISAS -- Center of Studies and Activities for Space, Univ.\ of Padova ``G. Colombo'', Italy}
\IBVSinst{University of Ljubljana, Department of Physics, Jadranska 19, 1000 Ljubljana, Slovenia}
 
\SIMBADobjAlias{GV Dra}{HD 163467} 
\IBVStyp{ EA } 
\IBVSkey{photometry} 
\IBVSabs{B and V light curves of GV Dra are presented.} 
\IBVSabs{For the first time the binary period (23.85433d) is estimated.} 
\IBVSabs{The position of the secondary minimum indicates very high eccentricity (e > 0.38).} 
 
\begintext 
 
GV\,Dra (HIP 87576, $V_{\rm max}=8\fmm53$, $B-V=0\fmm42$, F2)  was
between the stars with accurately known position even before  the
Hipparcos mission so it was included in the extension of the  Fifth
Fundamental Catalogue (Oja 1985; Fricke et al.\ 1991).  Hipparcos
satellite discovered that GV\,Dra is an eclipsing binary and it is
listed in the Hipparcos catalogue (ESA, 1997) as an unsolved EA
variable.

Here we present the results of regular photometric monitoring  in $B$
and $V$ bands that spanned 122 nights between March 1998 and September
2000.  We observed from a private observatory near Cembra, Italy. The
instrument was  a 28-cm Schmidt--Cassegrain Celestron telescope
equipped with Optec SSP5 photometer  and standard $B$ and $V$ filters.
The diaphragm had the size of 77 arcsec, and usual exposure time was 10
seconds. HD\,162131 (HIP\,86982, $V=7\fmm60$,  $B-V=0\fmm16$, A2) was
chosen as a comparison and  HD\,162035 (HIP\,86955, $V=8\fmm27$,
$B-V=0\fmm03$, A0) as a check star.

All the observations were corrected for atmospheric extinction and
colour corrections and the instrumental differential magnitudes were
transformed into standard $UBV$ system. The variable, comparison and
check stars are  very close to each other so the atmospheric
corrections were rather small. Altogether  we obtained 228 observations
in the $B$ and 371 in the $V$ band.  Typical error of the $B$ and $V$
magnitudes is 0\fmm01. The light curves of GV\,Dra in each band as well
as the $B-V$ colour variations are shown in Fig.~1.  Expanded plots
around primary and secondary eclipse are shown in Fig.~2.

The ephemeris for GV\,Dra, estimated on the base of our $B$ and $V$
photometric observations is:
$$ \begin{array}{r@{}r@{}l} 
{\rm Min.\ I = HJD\ }2451738.411 & {} + 23\fday85433 & {} \times E. \\ 
\pm 5 & \pm 3 & \\ 
\end{array} $$ 

The $B$ and $V$ light curves show that the depths of the eclipses are remarkably 
different. The estimated values are 0\fmm58 and 0\fmm28 for the primary and
the  secondary minima respectively. The duration of the primary eclipse is
about  11.5 hours. The secondary one lasts significantly longer, about 19
hours. The  system is detached with both components well inside their Roche
lobes. The  position of the secondary minimum at phase 0.736 indicates a
considerable  eccentricity of the orbit ($e > 0.38$).   
 
\IBVSfig{12cm}{4990-f1.ps}{Light curves of GV\,Dra in $B$ and $V$ filters for the 
estimated period of 23\fday85433. The bottom panel gives the $B-V$ colour 
variations.} 
 
\IBVSfig{8cm}{4990-f2.ps}{Expanded view around the primary and secondary eclipses
in the $V$ band.} 

The high orbital eccentricity makes GV\,Dra an interesting target for  further
spectral and photometric observations  in order to determine the  physical
parameters of this eclipsing system. 

The data are available upon request from dallas@inwind.it.  %email

 
\references 
 
ESA, 1997, {\it The Hipparcos and Tycho Catalogues}, ESA SP-1200 
 
Fricke, W., Schwan, H., Corbin, T., et al., 1991, {\it VeARI}, {\bf 33}, 1 
\BIBCODE{1991VeARI..33....1F} 
 
Oja, T., 1985, {\it A\&AS}, {\bf 59}, 461 % \BIBCODE{1985A&AS...59..461O} 
 
 \endreferences 

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