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\IBVShead{5303}{6 August 2002}

\IBVStitle{{\large $\mathbf{O-C}$} Analysis of SV C\lowercase{am} Over a Century}


\IBVSauth{ZBORIL, M.$^{1,2}$}

\IBVSinst{Astrophysical Institute, Potsdam, D-14482, Germany, e-mail: mzboril@aip.de}
\IBVSinst{Astronomical Institute, Tatransk\'{a} Lomnica, 059 60, Slovakia,
e-mail: zboril@astro.sk}

\SIMBADobj{SV Cam}
\IBVStyp{ RS }
\IBVSkey{photometry}
\IBVSabs{Primary photoelectric minima of RS CVn star SV Cam during}
\IBVSabs{the period 1896 up to 2002 are analysed.}                           

\begintext

The RS CVn star SV Cam (HD\,44982, SAO 1038, HIC32015,
G2-3V/K4V, SB1, m$_{V_{\rm max}}$=9.34 ) is a totally eclipsing binary system 
with
a short orbital period of 0.59~days. The system has been studied mainly 
photometrically
since the 30-ties (Guthnick, 1929) and both components display magnetic 
activity similarly to the Sun. The presence of a third body was
considered by several authors (e.g. Sarma et al., 1985 or Albayrak et al., 
2001). The following $O-C$~analysis covers the years 1896 up to 2002
and thus represents more than 60,000 orbits.\\   
\\
The following linear ephemeris (Pojma\'{n}ski, 1998) has been used

\begin{equation}
{\rm MinI} = {\rm HJD}~ 2~449~350.3037 + 0\fday593071~\times E
\end{equation}

The final $O-C$ analysis consists of all primary minima from several
database-like sources including recent observations by Zboril (2002). Most of
these data are based on Albayrak et al.'s (2001) collected minima and, finally,
from Hall and Kreiner (1980), Pierce (1938) and Wood (1946). Another potential 
source (Albayrak et al., 1999) contains mainly visual observations which did 
not improve the $O-C$ diagram. The times of minima in Table~1 (only available
electronically via IBVS Web-page as file 5303-t1.txt) were processed according to the equation (1) and the $O-C$ residuals are displayed in
Figure~1. The data suggest a quadratic term plus a sinusoidal variation. We fit
the data with such an equation which gives the final ephemeris of:

\begin{equation}
\begin{array}{rl}
{\rm MinI} =\ &{\rm HJD}~2~449~350.3045 +0.5930718\times E + 0.11075\cdot10^{-10}\times E^{2} +\\
              &\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \pm.0013\,\,\,\pm.0000017 \,\,\,\,\,\ \ \ \ \ \pm.0001\\
             & +0.0086\times\sin[2\pi\times(E - 3319.6)/36073.77301]\\
              & \,\,\,\pm.0004\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \,\,\,\,\,\,\pm3.3\ \ \,\,\,\,\,\,\pm4.8\\
\end{array}
\end{equation}

\IBVSedata{5303-t1.txt}
%\IBVSdataKey{5303-t1.txt}{SV Cam}{minima times}

The $O-C$ residuals give further support for the existence of a third body 
orbit with a period that is close to that derived in Sarma et al. (1985), i.e. 
approximately 50 years. Note though that the first few observations (3 points 
in 1896) are uncertain.\\

If only the more precise photoelectric minima are considered the period
from Albayrak et al. (2001) is confirmed. As pointed out by them, adopting the 
distance by Hipparcos, the angular separation of the third body
from the eclipsing pair is about 0\farcs19 and should be observable. 


\IBVSfig{7.8cm}{5303-f1.eps}{$O-C$ residuals based on the equation (1) for SV 
Cam and the fit with the equation (2).}
%IBVSfigKey{5303-f1.eps}{SV Cam}{O-C diagram}


{\it Acknowledgements:} The work was supported by the grant No. 2/1024/21 of 
Slovak Grant Agency for Science. The support of AIP Potsdam is gratefully 
acknowledged (DFG No. STR 645/1). 
Dr. Albayrak is cordially thanked for the data from his papers.


\references

Albayrak, B., \"{O}zeren, F.F., Ekmekci, F., Demircan, O., 1999, {\it Rev. Mex. Astron. Astrofis.}, {\bf 35}, 3

Albayrak, B., Demircan, O., Djura\v{s}evi\v{c}, G., Erkapi\v{c}, S., Ak H., 2001, {\it A\&A}, {\bf 376}, 158

Guthnick, P., 1929, {\it Astron. Nachr.}, {\bf 235}, 83

Hall, D. S., Kreiner, J. M., 1980, {\it Acta. Astron.}, {\bf 30}, 387

Pierce, N. L., 1938, {\it Contrib. Princeton Univ. Obs.}, {\bf 18}, 3

Pojma\'{n}ski, G., 1998, {\it Acta. Astron.}, {\bf 48}, 711

Sarma, C.V.S.R., Sarma, M.B.K., Abhyankar, K.D., 1985, {\it Bull. Astron. Soc. India}, {\bf 13}, 346

Wood, F. B., 1946, {\it Contrib. Princeton Univ. Obs.}, {\bf 21}, 1

Zboril, M., 2002, {\it IBVS}, No. 5245

\endreferences


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