\documentstyle[twoside,epsf]{article}

\input ibvs2.sty
\input ibvst.sty

\begin{document}

\IBVShead{5152}{8 August 2001}

\IBVStitletl{UBV Photometry of The Newly Found Active Star}{ YY Coronae Borealis}

\IBVSauth{Erdem, A.; Budding, E.; Dem\.{i}rcan, O.; \c{C}\.{i}\c{c}ek, C.; \"Ozdem\.{i}r, S.;  Bulut, \.{I}.;  \\ \indent Soydugan, E.; Soydugan, F.}

\IBVSinsto{\c{C}anakkale Onsekiz Mart University, Faculty of
Arts and Sciences, Department of Physics, \\ \indent TR-17100 \c{C}anakkale, Turkey, aerdem@bornova.ege.edu.tr} %email


\SIMBADobjAlias{YY CrB}{HD 141990}

\begintext

\IBVSTnam{YY CrB = BD +38\deg2706 = HIP 77598 = HD 141990}

\IBVSTcoo{15\hr50\mm32\fsec43}{+37\deg50\arcm07\farcs6}{2000}

\IBVSTobs{Ankara University Observatory, 30-cm Maksutov telescope}

\IBVSTdet{Hamamatsu, R 1414 (PMT)}

\IBVSTfil{Johnson $U$, $B$ and $V$}

\IBVSTcomp{BD +38\deg2708}

\IBVSTchk{BD +38\deg2701}

\IBVSTsysn

\IBVSTdata{Upon request}

\IBVSTtyp{ EW }

\IBVSfig{16cm}{5152-f1.ps}{The light and color curves of YY CrB}

\begin{table}
\caption{The light levels and their differences in the light
curves of YY CrB}
\begin{center}
\begin{tabular}{lrcc}
\hline
    & \multicolumn1c{$U$}  & $B$ & $V$ \\
\hline
Max.~light at 0.75 &  $-0.676$  &  $ 0.372$  &  $ 0.919$  \\
Max.~light at 0.25 &  $-0.736$  &  $ 0.324$  &  $ 0.867$  \\
Min.~light at 0.00 &  $-0.176$  &  $ 0.854$  &  $ 1.375$  \\
Min.~light at 0.50 &  $-0.177$  &  $ 0.840$  &  $ 1.352$  \\
$\Delta$max. ($m_{0.75}-m_{0.25}$) & $0.060$ &  $0.048$  &  $0.052$ \\
$\Delta$min. ($m_{0.00}-m_{0.50}$) & $0.001$ &  $0.014$  &  $0.023$ \\
Depth of Min.~I  &  $0.530$  &  $0.506$  &  $0.482$  \\
Depth of Min.~II &  $0.529$  &  $0.492$  &  $0.459$  \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSTrem{
The EW type active eclipsing binary star YY CrB was discovered by
HIPPARCOS (ESA, 1997). The system has a spectral type of G5 and an
amplitude of 0\fmm491 ranging from 8\fmm643 to 9\fmm134 in $V$ band (ESA,
1997). Sipahi et al.\ (2000) carried out the first ground based
photometric observations of the system in $B$, $V$ and $R$ bands. Both the
light curve of HIPPARCOS and light curves of Sipahi et al.\ have almost
equal maxima and minima, and there are no significant asymmetries in
their data. The star was observed photoelectrically  with the 30-cm
Maksutov telescope at the Ankara University Observation on the nights
of 8 and 9 May, 2000. The phases of the observations were calculated
using the following light elements given by Soydugan et al.\ (2000):
$$
{\rm HJD_{min\,I}} = 2448500.2535 + 0\fday3765694 \times E.
$$
The differential $U$, $B$ and $V$ light, and $U-B$ and $B-V$ color
curves in the instrumental system are shown in Figure~1. The shape of
the light curves are typical of W UMa type. A pronounced asymmetry is
evident in the light curves. This asymmetry is located between the
descending and ascending shoulders of the primary minimum (see
Table~1). There is no significant variation due to maculation or
proximity effects at either minimum in the $U-B$ and $B-V$ color curves
in Figure~1.}

\IBVSTack{We acknowledge the observing time at the Ankara
University Observatory. This work was supported by \c{C}anakkale
Onsekiz Mart University Research Fund (Project No.\ 99/FE/012).}

\references

ESA, 1997, The Hipparcos \& Tycho Catalogues, SP--1220

Sipahi, E., Keskin, V., Ya\c{s}arsoy, B.,  2000, {\it IBVS}, No.\
4859

Soydugan, F., Erdem, A., \"Ozdemir, S., Demircan, O., Soydugan, E,
Bulut, \.{I}, 2000, in XII. National Astronomy Meeting, ed.\
\.{I}bano\v{g}lu, C., Ege University Press, in press

\end{document}
