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\IBVShead{4257}{4 October 1995}

\title{THE OVERCONTACT BINARY SYSTEM NSV\,05798}

\begintext

	The variability of NSV\,05798 (HV\,10097, GSC\,4951.0769,
CSV\,001901) was announced by Hughes Boyce 
(1939) in a photographic survey carried  out by the Harvard
College Observatory in 1939 with the 10-inch Metcalf triplet in
South Africa. According to her  measurements, she
preliminarily classified the star as an overcontact binary star
with a photographic range from 12\fm 2 to 12\fm 8. The star was
catalogued as NSV\,05798 (Kholopov, 1982) awaiting for further
confirmation of Hughes' results. No ephemeris was given and
type F is the only spectral information available.

	During 18 nights, from March 21 to April 18, 1995, NSV\,05798
was observed in the V band using a LYNXX-2 CCD camera, attached
to the Newton focus of the 0.4-m telescope at Observatorio de
Mollet (Spain). SAO 138882 was used as comparison star (see
Figure~1).

	The result of this surveillance program proved that NSV\,05798
is an overcontact or nearly overcontact eclipsing binary star
with a period slightly shorter than 9 hours. Figure 2 shows the
obtained light curve in the V band. NSV\,05798 fades 0.63 and
0.61 magnitudes at the primary and secondary minima
respectively. 
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\centerline{Figure 1}
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\centerline{2}
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Figure 2. Light curve of NSV\,05798 in the V band (points) and
superimposed synthetic light curve (solid) for the given
physical parameters.
\large

\vskip 5mm
	From our set of data we computed the following ephemeris for
the primary minimum:
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\centerline{Min.\,I = HJD\,2449825.54948  +  0\fd 36942$\times$E}
\hspace*{8cm}$\pm$50 \hspace*{13mm}$\pm$6
\vskip 1mm

	Although both minima are almost identical in depth, they are
different in shape. The primary minimum is sharper than
the secondary one, suggesting that during the primary we observe
a transit while during the secondary we observe an occultation.

	We used Binary Maker 2.0 (Bradstreet, 1993) to obtain the
physical elements for the light curve (Figure 2). For an assumed spectral
type F5V, we adopted a limb darkening coefficient of 0.6 for both
stars and a gravity darkening coefficient of 0.32. We also adopted a 
value of 0.5 for the reflection coefficient. The physical elements in 
the V band are:
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\begin{center}
\begin{tabular}{ll}

			mass ratio &     q : 0.55 $\pm$ 0.05\\
			fillout    &     f : 0.02 $\pm$ 0.02\\
			           &     i : 79\degr 8 $\pm$ 0\degr 2\\
		a$_g$ = 0.46 $\pm$ 0.01 &   a$_s$ = 0.36 $\pm$ 0.01\\
		b$_g$ = 0.43 $\pm$ 0.01 &   b$_s$ = 0.32 $\pm$ 0.01\\
		c$_g$ = 0.41 $\pm$ 0.01 &   c$_s$ = 0.31 $\pm$ 0.01\\
		d$_g$ = 0.56 $\pm$ 0.01 &   d$_s$ = 0.44 $\pm$ 0.01\\
		L$_1$ = 0.64 $\pm$ 0.02 &   L$_2$ = 0.36 $\pm$ 0.02\\
		g$_1$ = 0.32          &     g$_2$ = 0.32\\
		x$_1$ = 0.60          &     x$_2$ = 0.60\\
		A$_1$ = 0.5           &     A$_2$ = 0.5\\
		T$_1$ = 6620K $\pm$ 50K &   T$_2$ = 6600K $\pm$ 50K\\ 
\end{tabular}
\end{center}
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\centerline{3}

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	To have a deeper understanding of this binary system, it is
important that future research on this star be directed to
perform multicolor photometry, spectroscopic analysis to exactly
determine its spectral type, and search for radial velocities.

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\beginauthors
\authorsrightcol
Josep M. GOMEZ-FORRELLAD
Enrique GARCIA-MELENDO
Grup d'Estudis Astronomics
Apartado 9481
08080 Barcelona
Spain
e-mail: jmgomez@astro.gea.cesca.es
\endauthors

\references

Bradstreet, D. H., 1993, Binary Maker 2.0 User Manual, Contact
Software, Norristown, Pennsylvania

Hughes Boyce, E., 1939, {\it Bulletin of the Hardvard College
Observatory}, No.\,911

Kholopov, P. N. editor, 1982, New Catalogue of Suspected
Variable Stars, Moscow

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