\documentstyle[twoside,epsf]{article}
\input ibvs2.sty
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\begin{document}
\IBVShead{5635}{21 July 2005}


\IBVStitle{2004 UBVR Photometry of the Eclipsing Binary KR C\lowercase{yg}}


\IBVSauth{S\.{i}pah\.{i}, E.}


\IBVSinsto{Ege University Observatory, 35100 Bornova, \.{I}zmir, Turkey. 
e-mail: sipahi@astronomy.sci.ege.edu.tr}


\SIMBADobj{KR Cyg}


\begintext


\IBVSTcoo{20\hr 09\mm 17\fsec6 }{+30\deg 33\arcm 55\arcs}{2005.0}


\IBVSTobs{Ege University Observatory, 48 cm Cassegrain telescope.}


\IBVSTdet{High Speed Three-Channel Photon counting photometer (HSTCP).}


\IBVSTfil{UBVR}


\IBVSTdateobs{2004.06.25~-~2004.07.08}


\IBVSTcomp{HD 191398}


\IBVSTchk{HD 333664}

\IBVSTsys{Yes}{HD 185025 (from Landolt, 1992)} 


\IBVSTdata{upon request}


\IBVSTtyp{ EB }


\IBVSTrem{Using the latest published minima taken from Ta\c{s} et al. (2004) 
with the minima 
times in Table II of Sipahi and G\"{u}lmen (2004), the light elements are 
improved using the linear least squares method and expressed in the
following equation with the probable errors:
$$ {\rm HJD\ Min\ I} = 2429106.3987 (14) + 0.84515252(7)  { \times E}$$
The O-C's were computed according to Vetesnik (1965). In this study
the UBVR light curves of the system obtained in the year 2004 is presented. 
The light curves obtained in four colours are shown in Figure 1. The first U-B 
colour curve of KR~Cyg in the literature is observed and is plotted together 
with the other colour index curves in Figure 2. The amplitudes of primary 
minima for U, B, V, R bands are 0\fmm882, 0\fmm878, 0\fmm833 and 0\fmm800
magnitudes, respectively. The asymmetrical shape of the lowest part of the 
primary minimum is rather a striking feature. Similar effect appears in the
light curve of some Algols and $\beta$ Lyr type systems like BL~And, V1425 Cyg 
and of Algol itself. It is generally accepted that this asymmetry is
caused by the presence of the gaseous stream or by an accretion disc. In Fig. 2
another striking feature appears: the $B-V$ and $V-R$ colour curves become
redder in primary minimum, while they get bluer in secondary minimum. This 
would indicate that primary eclipse is an occultation: the radiation from
hotter, bluer star is being blocked by the secondary. On the other hand, $U-B$ 
colour curve gets bluer during both minima. This interesting behaviour of 
colour curves of KR Cyg will be investigated in an other study.} 

\IBVSTack{I am grateful to Dr. G. Ta\c{s} for her comments.}


\IBVSfig{10cm}{5635-f1.eps}{The UBVR light curves of KR Cyg.}
\IBVSfigKey{5635-f1.eps}{KR Cyg}{light curve}

\IBVSfig{10cm}{5635-f2.eps}{The colour curves of KR Cyg.}
\IBVSfigKey{5635-f2.eps}{KR Cyg}{color curve}


\references

Landolt, A. U., 1992, {\it AJ}, {\bf 104}, 340.

Sipahi, E. and G\"{u}lmen, \"{O}, 2004, {\it ApSS}, {\bf 293}, 307.

Ta\c{s} et al., 2004, {\it IBVS} No. 5548.

Vetesnik, M., 1965, {\it BAC}, {\bf 16}, 326. 

\endreferences

\vfill\eject

\IBVSerratum{5549}

There is a typographical error in the GSC identification of V3886 Sgr 
as listed in IBVS 5549. The article identified the variable as GSC 7492 3038. 
The correct identification is GSC 7942 3038.

\bigskip

Shawn Dvorak


\end{document}


