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\begin{document}

\IBVShead{5056}{7 April 2001}

\IBVStitletl{New Photoelectric Minima and Updated Ephemerides}{ of Selected Eclipsing Binaries}

\IBVSauth{Pribulla, T.$^1$; Va\v{n}ko, M.$^1$; Parimucha, \v{S}.$^2$; Chochol, D.$^1$}

\IBVSinst{Astronomical Institute of the Slovak Academy of Sciences,
059 60 Tatransk\'a Lomnica, Slovak Republic, \\ \indent e-mail: pribulla@ta3.sk, vanko@ta3.dk, chochol@ta3.sk}

\IBVSinst{Faculty of Science, Department of the Theoretical Physics and
Geophysics, University of P.J. \v{S}af\'arik,\\ \indent 040 01 Ko\v{s}ice,
Slovak Republic, e-mail: parimuch@ta3.sk}

\IBVSabs{This report presents minima times and updated ephemerides}
\IBVSabs{of selected eclipsing binaries}

\IBVStyp{ Eclipsing binary }

\begintext

We present 58 new minima times of 23 eclipsing close binaries obtained
from July 1999 to March 2001 as a part of the program of their full
light-curve coverages. The $UBVR$ photoelectric observations were taken
at the Skalnat\'e Pleso (SP) and Star\'a Lesn\'a (SL) observatories of
the Astronomical Institute of the Slovak Academy of Sciences. In both
cases the 0.6-m Cassegrain telescope equipped with a single-channel
pulse-counting photoelectric photometer was used. For all observations
a 10-second integration was used. Data reduction, the atmospheric
extinction correction and transformation to the standard international
$UBV$ system were carried out in the usual way. We have calculated
the times of minima separately for all filters using the Kwee and Van
Woerden's method, parabola fit, sliding integration method, tracing
paper and ``center of mass'' method which were described in detail by
Ghedini (1982). The computer codes were kindly provided by
Kom\v{z}\'{\i}k (2000). To eliminate the influence of the photospheric
activity on the minima times (e.g., for RT And and XY UMa), for
computations of the primary and secondary minima we have used only
observations in the phase intervals $\pm0.02$ and $\pm0.04$,
respectively. The average times of the primary (I) and secondary (II)
minima in different passbands and their probable errors are given in
Table~1.

We have also collected all available minima times of these eclipsing
binaries from literature and from compilations kindly provided by
Kreiner (2000). The CCD, photoelectric and visual minima were weighted
according to their average precision. Since the period changes in close
binaries are rather often and pronounced, the presented ephemerides
(Table~2) were obtained by fitting the data in the last section of the
$O-C$ diagram which is approximately linear. The orbital periods of a
large fraction of the presented binaries (AB And, BX And, SV Cam, VW
Cep, EF Dra, SW Lac, XY UMa) are modulated by the presence of further
component(s) in the system. Hence, the linear ephemerides of these
systems are expected to be valid with a sufficient precision
(0.01--0.02 in phases) only during few years. This is the case for
multiple systems like VW Cep or EF Dra, where apparent changes of the
orbital period has recently been quite large.

Detailed light-curve analysis and study of the period changes will be
published elsewhere.

\begin{table}
\caption{New times of primary (I) and secondary (II) minima. 
The standard errors are given in parentheses}
\begin{center}
\normalsize
\begin{tabular}{llccc|llccc}
\hline
\lower6pt\hbox{System} & JD$_{\rm hel}$ & \lower6pt\hbox{Min.} & \lower6pt\hbox{Obs.} & \lower6pt\hbox{Fil.} &
\lower6pt\hbox{System} & JD$_{\rm hel}$ & \lower6pt\hbox{Min.} & \lower6pt\hbox{Obs.} & \lower6pt\hbox{Fil.} \\[-2pt]
 & 2400000\,+ & & & &
 & 2400000\,+ & & & \\
\hline
AB And & 51776.53314(5) & I & SL & B & SV Cam & 51921.2796(9) & I & SP & V \\
 & 51776.53387(3) & I & SL & V & & 51924.5381(4) & II& SP & R \\
 & 51777.36296(3) & II& SL & B & & 51924.5388(3) & II& SP & V \\
 & 51777.36365(5) & II& SL & V & & 51997.4852(9) & II& SP & R \\
 & 51833.2869(1) & I & SL & V & & 51997.4898(9): & II& SP & V \\
 & 51833.28697(3) & I & SL & B & EG Cep & 51718.44352(15)& I & SP & R \\
 & 51833.45306(5) & II& SL & V & & 51718.44389(5) & I & SP & V \\
 & 51833.45315(10)& II& SL & B & & 51718.44413(13)& I & SP & B \\
 & 51925.22047(6) & I & SL & B & & 51772.36150(8) & I & SL & B \\
 & 51925.22064(2) & I & SL & V & & 51772.36160(12)& I & SL & V \\
BX And & 51800.5452(3) & I & SL & B & GW Cep & 51968.3054(1) & II& SL &BV \\
 & 51800.5454(2) & I & SL & V & VW Cep & 51707.4008(2) & I & SL & V \\
 & 51838.3734(1) & I & SL & B & & 51707.4013(4) & I & SL & B \\
 & 51838.3739(1) & I & SL & V & & 51716.4465(3) & II& SL & B \\
 & 51838.3743(1) & I & SL & U & & 51716.4478(2): & II& SL & V \\
RT And & 51776.45476(4) & I & SL & V & & 51772.52501(6) & I & SL & V \\
 & 51776.45495(4) & I & SL & B & & 51772.52522(8) & I & SL & U \\
 & 51778.3411(2): & I & SP & R & & 51772.52561(8) & I & SL & B \\
 & 51778.3416(2) & I & SP & B & & 51777.5339(2) & I & SL & V \\
 & 51778.3417(1) & I & SP & V & & 51777.5346(2) & I & SL & B \\
SS Ari & 51928.25849(5) & I & SL & V & YY CrB & 51975.6053(1) & I & SL & V \\
 & 51928.25893(3) & I & SL & B & & 51975.6056(1) & I & SL & B \\
44i Boo& 51704.4907(2) & I & SL & V & EF Dra & 51968.5766(1) & I & SL & B \\
 & 51704.4909(2) & I & SL & B & & 51968.5772(1) & I & SL & V \\
 & 51705.4260(2) & II& SL & B & FU Dra & 51925.67608(5) & I & SL & B \\
 & 51705.4270(2) & II& SL & V & & 51925.6756(1) & I & SL & V \\
 & 51556.6529(2) & I & SP & V & & 51927.6701(4) & II& SL & V \\
 & 51556.6530(3) & I & SP & R & & 51927.6710(1) & II& SL & B \\
 & 51556.6538(1) & I & SP & B & & 51952.5134(3) & II& SL & V \\
 & 51668.4679(2) & II& SL & V & & 51952.5140(1) & II& SL & B \\
 & 51668.4689(13):& II& SL & B & & 51952.6665(2) & I & SL & B \\
 & 51968.4253(1) & II& SL & V & & 51952.6679(1) & I & SL & V \\
 & 51968.4265(1): & II& SL & B & SW Lac & 51389.51309(2) & I & SL & V \\
V523 Cas&51822.4264(2) & I & SP & V & & 51389.51313(2) & I & SL & B \\
 & 51822.4267(2) & I & SP & R & & 51389.51316(5) & I & SL & U \\
 & 51822.4269(1) & I & SP & B & & 51536.24001(13)& II& SP & B \\
AO Cam & 51798.5673(2) & II& SL & V & & 51536.24003(8) & II& SP & R \\
 & 51798.5675(1) & II& SL & B & & 51536.24012(8) & II& SP & V \\
SV Cam & 51435.54893(9) & I & SL & U & & 51772.4445(1) & I & SL & B \\
 & 51435.54893(3) & I & SL & B & & 51772.4448(1) & I & SL & V \\
 & 51435.54909(3) & I & SL & V & & 51860.32001(3) & I & SL & V \\
 & 51536.37178(5) & I & SP & V & & 51860.32028(8) & I & SL & B \\
 & 51536.37209(2) & I & SP & R & UV Lyn & 51898.4814(1) & I & SL & B \\
 & 51536.37238(4) & I & SP & B & & 51898.4821(2) & I & SL & V \\
 & 51550.3096(3) & II& SL & B & & 51929.39972(5) & II& SL & V \\
 & 51550.3116(3) & II& SL & V & & 51929.4004(2) & II& SL & B \\
 & 51878.5746(4) & I & SP & V & & 51929.6066(1) & I & SL & V \\
 & 51878.5757(5) & I & SP & R & & 51929.6068(2) & I & SL & B \\
 & 51878.5762(4) & I & SP & B & & 51958.4490(2) & II& SL & V \\
 & 51921.2792(6) & I & SP & R & & 51958.4496(5) & II& SL & B \\
 & 51921.2793(4) & I & SP & B & U Peg & 51778.4966(1) & II& SL & B \\
\hline
\end{tabular}
\end{center}
\end{table}

\begin{table}
\addtocounter{table}{-1}
\caption{(continued)}
\begin{center}
\normalsize
\begin{tabular}{llccc|llccc}
\hline
\lower6pt\hbox{System} & JD$_{\rm hel}$ & \lower6pt\hbox{Min.} & \lower6pt\hbox{Obs.} & \lower6pt\hbox{Fil.} &
\lower6pt\hbox{System} & JD$_{\rm hel}$ & \lower6pt\hbox{Min.} & \lower6pt\hbox{Obs.} & \lower6pt\hbox{Fil.} \\[-2pt]
 & 2400000\,+ & & & &
 & 2400000\,+ & & & \\
\hline
U Peg & 51778.4970(1) & II& SL & V & EQ Tau & 51930.2550(5): & II& SL & V \\
 & 51794.4230(4): & I & SL & B & & 51930.2565(1) & II& SL & B \\
 & 51794.4241(1) & I & SL & V & AW UMa & 51536.5917(1) & I & SP & R \\
 & 51860.3852(1) & I & SL & B & & 51536.5922(1) & I & SP & B \\
 & 51860.3858(2) & I & SL & V & & 51536.5923(2) & I & SP & V \\
V432 Per&51911.2699(8): & I & SP & R & & 51928.5919(3): & II& SL & B \\
 & 51911.2714(7) & I & SP & B & & 51928.5933(1) & II& SL & V \\
 & 51911.2728(12) & I & SP & V & W UMa & 51556.48346(10) & II& SL & B \\
AH Tau & 51956.24554(6) & II& SL & V & & 51556.48373(4) & II& SL & V \\
 & 51956.2459(2) & II& SL & B & & 51597.52083(7) & II& SL & B \\
EQ Tau & 51896.2932(1) & I & SL & B & & 51597.52084(8) & II& SL & V \\
 & 51896.29324(5) & I & SL & V & XY UMa & 51919.5420(2) & I & SL & U \\
 & 51911.3122(2) & I & SL & V & & 51919.5421(2) & I & SL & B \\
 & 51911.31279(6) & I & SL & B & & 51919.54283(3) & I & SL & V \\
\hline
\end{tabular}
\vspace{0.5cm}
\caption{New ephemerides of the selected eclipsing close binaries.
The standard errors are given in parentheses, e.g., the entry 51534.2504(5)
should be interpreted as $51534.2504\pm0.0005$. The reference gives last 
paper dedicated to the system or particularly to study of period change.}
\vspace{4mm}
\begin{tabular}{lllcll}
\hline
\lower6pt\hbox{System} & JD$_0$ & \lower6pt\hbox{Period} & \lower6pt\hbox{Interval} & Period & \lower6pt\hbox{Reference} \\[-2pt]
 & 2400000\,+ & & & change & \\
\hline
AB And & 51534.2504(5) & 0\fday33189106(4) & 1981--2001 & LT + $\nearrow$ & Borkovits et al.\ (1996) \\
BX And & 36528.8118(22)& 0.61011285(11)& 1981--2000 & LT ? & Demircan et al.\ (1993) \\
RT And & 32443.7967(5) & 0.62892932(2) & 1968--2000 & $\searrow$ & Pribulla et al.\ (2000a) \\
SS Ari & 41947.151(5) & 0.4059836(2) & 1993--2001 & $\searrow$ & Demircan et al.\ (1993) \\
44i Boo & 50945.4898(6) & 0.26781916(7) & 1988--2001 & $\nearrow$ & Gherega et al.\ (1994) \\
V523 Cas& 47000.1839(5) & 0.23369229(4) & 1987--2000 & $\nearrow$ & Lister et al.\ (2000)\\
AO Cam & 45745.6391(6) & 0.32990473(7) & 1980--2000 & $\rightarrow$ & Rucinski et al.\ (2000)\\
SV Cam & 33777.389(2) & 0.59307318(8) & 1979--2001 & LT ? & Albayrak et al.\ (1999) \\
EG Cep & 26929.3962(20)& 0.54462278(5) & 1976--2000 & $\nearrow$ & Chochol et al.\ (1998) \\
GW Cep & 47000.1436(12)& 0.31882954(11)& 1989--2001 & $\searrow$ & Pribulla et al.\ (2001b) \\
VW Cep & 33898.424(23) & 0.2783131(4) & 1997--2000 & LT + $\searrow$ & Pribulla et al.\ (2000b) \\
YY CrB & 50955.8688(12)& 0.37656421(9) & 1998--2001 & $\rightarrow$ & Rucinski et al.\ (2000) \\
EF Dra & 51789.2125(12)& 0.4240257(2) & 1989--2001 & LT + $\nearrow$ ? & Pribulla et al.\ (2001b) \\
FU Dra & 50866.2768(5) & 0.30671682(13)& 1991--2001 & $\rightarrow$ & Rucinski et al.\ (2000) \\
SW Lac & 51056.2896(3) & 0.32071510(9) & 1993--2000 & LT + $\nearrow$ & Pribulla et al.\ (1999a) \\
UV Lyn & 47000.4197(10)& 0.41498460(15)& 1988--2001 & $\nearrow$ & Lu et al.\ (1999) \\
U Peg & 33512.032(4) & 0.37477742(10)& 1985--2000 & $\searrow$ & Borkovits et al.\ (1996) \\
V432 Per& 48601.3750(7) & 0.3833120(2) & 1991--2001 & LT ? & Agerer (1992) \\
AH Tau & 47000.2689(5) & 0.33267164(7) & 1975--2001 & $\searrow$ ? & Liu et al.\ (1991)\\
EQ Tau & 47000.3566(7) & 0.34134666(10)& 1984--2001 & LT or $\searrow$ & Buckner et al.\ (1998) \\
AW UMa & 38044.892(10) & 0.4387259(3) & 1994--2001 & $\searrow$ + LT ? & Pribulla et al.\ (1999b) \\
W UMa & 50554.7428(2) & 0.33363551(3) & 1984--2000 & LT ? & Depasquale et al.\ (1999)\\
XY UMa & 35216.398(5) & 0.47899819(16)& 1994--2001 & LT + $\nearrow$ & Pribulla et al.\ (2001a) \\
\hline
\multicolumn{6}{l}{LT: light-time effect, $\nearrow$: period increase,
$\searrow$: period decrease, $\rightarrow$: constant period}
\end{tabular}
\end{center}
\end{table}

{\it Acknowledgements:} This study was supported by VEGA grant 1157/2001 of the
Slovak Academy of Sciences.

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\end{document}
