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\IBVShead{4739}{4 August 1999}

\IBVStitle{TIMES OF MINIMA OF SOME SOUTHERN ECLIPSING BINARIES }


\IBVSauth{Z. Kv\'{i}z~\dag $^1$, M. Zejda$^2$, L. Kohoutek$^3$, J. Grygar$^4$}

\IBVSinst{Observatoire de Gen\`{e}ve, 1920 Sauverny, Switzerland}
\IBVSinst{N. Copernicus Observatory and Planetarium, Krav\'{\i} hora 2, 616 00 Brno, Czech Republic}
\IBVSinst{Hamburg Observatory, Gojenbergsweg 112, 21029 Hamburg, Germany}
\IBVSinst{Institute of Physics, Na Slovance 2, 180 40 Praha 8 -- Libe\v{n}, Czech Republic}

\begintext

Moments of minima were derived for eight southern eclipsing binaries from photoelectric observations made with the seven channel photometer in the Geneva photometric system by one of the authors (Z. Kv\'{\i}z) in the years 1977--1988. The photometer was attached to the 0.7-m Swiss reflector operating at the European Southern Observatory, La Silla (Chile). The reason for these observations was to study the interesting systems, especially to investigate the possible period changes of these short period binaries (see e.g.\ Kv\'{\i}z, Rufener, 1981). Unfortunately, Zden\v{e}k Kv\'{\i}z was not able to continue this programme. 

The programme stars are listed in Table~1, where the columns are as follows:
name of the star, brightness of the binary outside the eclipse and in the centre of the primary minimum, system of magnitudes used (the letter P means photographic magnitudes and the letter V denotes visual or photovisual magnitudes), equatorial co-ordinates (1950.0) and orbital elements $M(0)$ and $P$ of the systems given in GCVS (Kholopov et al., Samus' et al., 1998), used in Table~2.

The results are given in Table~2, where HJD are the heliocentric JD of the
respective minima together with their mean errors, and $n$ is the number of
individual observations used. We also give the respective phases and the epochs (see Table~1 for the orbital elements).

The times of the 21 minima were determined using the programme TINT4 (Gaspani, 1995) based on the artificial neural network. The presented error is similar to the standard deviation of the time of minimum. The programme uses measurements made in all colours and the V-magnitudes were weighted separately from the magnitudes of six colour indices. The calculated phases of the minima differ significantly from 0.0 and 0.5, respectively, so that small changes of periods can be expected with most of the mentioned stars.

We wish to acknowledge the help of G. Burki who gave us important information, and of A. Gaspani for the possibility of using the programme TINT4. We thank the director of the Geneva Observatory for supporting the work of Z. Kv\'{\i}z at La Silla.

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\normalsize
Table~1: List of programme stars.
\vskip 3mm
\begin{tabular}{lrrcllll}
\hline
\raise-6pt\hbox{Star} & \multicolumn{2}{c}{Brightness [mag]} & \raise-6pt\hbox{Branch} & \multicolumn{1}{c}{RA} & \multicolumn{1}{c}{DEC} & $M(0)$ & \raise-6pt\hbox{$P$ [days]} \\[-6pt] 
& \multicolumn{1}{l}{Max} & Min I & & \multicolumn{2}{c}{(1950.0)} & (${\rm JD}-2400000$) & \\
\hline
U Col & 10.40 & 11.00 & P & 06 13 02 & $-33$ 03 36 & 28521.774 & 1.24617466 \\
V Lep & 9.60 & 10.10 & V & 06 08 50 & $-20$ 12 00 & 18873.723 & 1.0701048 \\
RS Lep & 9.91 & 10.38 & V & 05 57 09 & $-20$ 13 36 & 36191.148 & 1.2885439 \\
RU Lep & 11.23 & 12.12 & V & 06 01 50 & $-24$ 54 00 & 43516.670 & 4.459601 \\
UX Men & 8.80 & 9.57 & P & 05 31 59 & $-76$ 17 00 & 41984.64388 & 4.181100 \\
$\zeta$ Phe & 3.91 & 4.42 & V & 01 06 17.3 & $-55$ 30 46 & 41643.6890 & 1.6697671 \\
BQ Sgr & 9.40 & 11.87 & V & 19 10 54.4 & $-36$ 19 51 & 22224.378 & 8.019537 \\
CW Vel & 10.10 & 11.12 & V & 09 00 49.2 & $-52$ 38 36 & 44248.7584 & 2.360927 \\
\hline
\end{tabular}

\vfil

Table~2: Times of minima.
\vskip 3mm
\begin{tabular}{lllrrrll}
\hline
\raise-6pt\hbox{Star} & Type of & HJD & \multicolumn{1}{l}{\raise-6pt\hbox{Error*}} & \multicolumn{1}{c}{\raise-6pt\hbox{$n$}} & \multicolumn{1}{l}{\raise-6pt\hbox{Epoch}} & \raise-6pt\hbox{Phase} & \raise-6pt\hbox{Note} \\[-6pt]
& minima & ($-2400000$) & & & & & \\
\hline
U Col & prim & 44993.676 & 0.001 & 28 & 13218.0 & 0.973 & normal min. (3 nights) \\
& sec & 43482.691 & 0.007 & 46 & 12005.5 & 0.474 & normal min. (2 nights) \\
& sec & 44945.696 & 0.006 & 23 & 13179.5 & 0.471 & \\
V Lep & prim & 43478.727 & 0.003 & 36 & 22993.0 & 0.079 & normal min. (2 nights) \\
& sec & 43471.774 & 0.001 & 13 & 22986.5 & 0.582 & \\
RS Lep & prim & 45678.702 & 0.004 & 32 & 7363.0 & 0.004 & \\
& sec & 45680.633 & 0.010 & 9 & 7364.5 & 0.502 & \\
RU Lep & prim & 43516.670 &$<$0.001 & 11 & 0.0 & 0.000 & \\
& prim & 45670.654 &$<$0.001 & 9 & 483.0 & 0.999 & \\
& prim & 45719.727 & 0.002 & 30 & 494.0 & 0.003 & \\
& prim & 45728.648 & 0.002 & 24 & 496.0 & 0.003 & \\
& prim & 46058.654 & 0.003 & 49 & 570.0 & 0.003 & normal min. (3 nights) \\
& sec & 45699.662 & 0.021 & 45 & 489.5 & 0.504 & normal min. (7 nights) \\
UX Men & prim & 43485.659 & 0.003 & 23 & 359.0 & 0.000 & \\
$\zeta$ Phe & prim & 43473.755 & 0.010 & 43 & 1096.0 & 0.001 & normal min. (5 nights) \\
& sec & 43469.593 & 0.001 & 18 & 1093.5 & 0.508 & \\
& sec & 43474.605 & 0.002 & 31 & 1096.5 & 0.510 & normal min. (2 nights) \\
BQ Sgr & prim & 47253.07 & 0.10~ & 10 & 3121.0 & 0.96 & normal min. (10 nights) \\
& sec & 47305.54 & 0.08~ & 7 & 3127.5 & 0.51 & normal min. (7 nights) \\
CW Vel & prim & 46491.639 & 0.002 & 31 & 950.0 & 0.000 & normal min. (6 nights) \\
& sec & 46485.745 & 0.002 & 35 & 947.5 & 0.504 & normal min. (6 nights) \\
\hline
\end{tabular}
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{\normalsize * The error given in TINT4 (a version of TINAGEL) is very similar to a standard deviation and it describes the true uncertainty of $t(0)$ better, than only the statistical properties of the data set would do.}

\references

Gaspani A., 1995, private communication

Kholopov P.N. (ed.)\ et al., Samus' N. N. (ed.)\ et al., 1998, {\it General Catalogue of Variable Stars}, electronic edition v4.1 (ftp://ftp.sai.msu.su/pub/groups/clusters/gcvs/gcvs)

Kv\'{\i}z Z., Rufener F., 1981, {\it IBVS} No.\,2014

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