\documentstyle[twoside,epsf]{article}

\input ibvs2.sty
\input ibvst.sty

\begin{document}

\IBVShead{4883}{25 April 2000}

\IBVStitletl{Three-Colour Photometry of MM Herculis}{ During 1998--1999 }

\IBVSauth{Ta\c{s}, G.}

\IBVSinsto{Ege University Observatory, 35100 Bornova, Izmir, Turkey,
email: tas@alpha.sci.ege.edu.tr}

\SIMBADobjAlias{MM Her}{HD 341475}

\begintext

\IBVSTnam{MM Her = BD\,+22\deg3245 = HD 341475}

\IBVSTcoo{17\hr 58\mm 35\fsec99}{22\deg 08\farcm78}{1999}

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

\IBVSTdet{Hamamatsu, R4457 (PMT)}

\IBVSTfil{$B$, $V$ and $R$ filters of Johnson $UBV$ system}

\IBVSTcomp{BD\,+21\deg 3274 = HD 341480}

\IBVSTchk{BD\,+22\deg 3250 = HD 164306}

\IBVSTsys{UBV}{Pleiades stars}

\IBVSTdata{Upon request}

\IBVSTtyp{ EA }

\IBVSfig{9.9cm}{4883-f1.eps}{The light curves of MM Herculis obtained in
1998 and 1999.}

\IBVSfig{9.9cm}{4883-f2.eps}{The colour curves of MM Her obtained in
1998 (upper panel) and 1999 (bottom panel). The open circle
and plus symbols indicate $B-V$ and $V-R$ colours, respectively.}

\IBVSTrem{
The eclipsing binary MM Herculis is one of the most active binary
systems in the class of RS CVn stars.  The system was first observed
visually by Tsesevich (1954). Recently, its light variations were
examined by Heckert and Ordway (1995), Evren and Ta\c{s} (1999) and
Ta\c{s} et al.\ (1999).  Our observing run includes 42 nights between
May 5 and October 8, 1998 and 45 nights between March 1 and October 6,
1999. We obtained 749 and 912 data points for each colour in 1998
and 1999, respectively. The light (in $V$) and colour (in $B-V$ and
$V-R$) curves obtained in these years are shown in Figures 1a,b and
2a,b.  The phase of each observation was computed by the following light
elements
$$
{\rm HJD_{min I}}=2445551.4274+7\fday960326 \times E.
$$
Wave-like distortions outside the eclipses are clearly seen from
Fig~1. The amplitudes of the waves are about 0\fmm04 and 0\fmm05
in 1998 and 1999, respectively.  The light variations seen outside
eclipses are caused by star spots and the distortion waves possess
two minima separated by almost half a period.  The brightness at
mid-primary minimum of the system obtained in 1999 is about 0\fmm04
fainter than the one in 1998.}

\IBVSTack{
I would like to thank Drs.\ C.~Ibanoglu and S.~Evren for their advice
and guidance.  This work was supported by Ege University Research Fund
(Project No.\ 99/FEN/014).}

\references

Evren, S. and Ta\c{s}, G., 1999, {\it IBVS}, No.\ 4687

Heckert, P.A. and Ordway, J.I., 1995, {\it AJ}, {\bf 109}, 2169

Ta\c{s}, G., Evren, S. and Ibanoglu, C., 1999, {\it A\&A}, {\bf 349}, 546

Tsesevich, V.P., 1954, {\it Odessa Izv.}, {\bf 4}, Part 2, 116

\end{document}
