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\IBVShead{4691}{2 April 1999}

\IBVStitle{New Observations of the Fuor V1057 C\lowercase{yg}}

\IBVSauth{Mansur A. Ibrahimov}

\IBVSinsto{Ulugh Beg Astronomical Institute, 33 Astronomical Str., Tashkent 700052, Uzbekistan,\\ mansur@astrin.uzsci.net} %email


\begintext

\IBVSTnam{V1057 Cyg}

\IBVSTcoo{20\hr57\mm06\fsec24}{+44\deg03\arcm46\farcs4}{1950.0}

\IBVSTobs{Mt.\ Maidanak High Altitude Observatory, 0.6-m Zeiss reflector}

\IBVSTdet{Single-channel pulse-counting photometer}

\IBVSTfil{Johnson's UBVR}

\IBVSTcomp{BD +43\deg3781}

\IBVSTchk{BD +40\deg4147}

\IBVSTsys{Johnson system}{Selected Areas Nos.\ 104--112 by Landolt (1983)}

\IBVSTdata{Upon request}

\IBVSTtyp{ FU (= FU Orionis type variable) }

\IBVSTrem{Figure 1 shows that the star is still fading. There is no
clear trend to recover the normal brightness so far. Color-magnitude
diagrams of the star during decline in 1995--98 (Table 1) show that the
smooth reddening of optical colors have been changed towards becoming
bluer in last two years. Evolution of the U$-$B color differs from that
of two other colors and proceeds slower (Fig.\ 1).  The recent blueing
of the colors of V1057 Cyg provides additional support for the dust
condensation hypothesis.}

\IBVSTack{This work is partly supported by CRDF grant ZP1-341.}

\newpage

\begin{table}
\caption{Yearly averaged brightness and color variations of V1057 Cyg during the recent decline}
\begin{center}
\begin{tabular}{crrrrrcccc}
\hline
Year & JDH 24\dots & \multicolumn{1}{c}{V} & \multicolumn{1}{c}{B$-$V} & \multicolumn{1}{c}{U$-$B} & \multicolumn{1}{c}{V$-$R} & N$_{\rm V}$ & N$_{\rm BV}$ & N$_{\rm UB}$ & N$_{\rm VR}$ \\
\hline
1995 & 49882--50045 & 12.231 & +2.030 & +1.595 & +1.868 & 56 & 56 & 36 & 56 \\
     &              &     71 &     45 &    243 &     32 \\
1996 & 50209--50415 & 12.200 & +2.091 & +1.655 & +1.885 & 72 & 72 & 23 & 71 \\
     &              &    144 &    101 &    338 &     48 \\
1997 & 50596--50764 & 12.463 & +2.053 & +1.929 & +1.868 & 74 & 73 & 17 & 73 \\
     &              &    106 &     58 &    453 &     41 \\
1998 & 50995--51168 & 12.696 & +1.983 & +1.695 & +1.786 & 68 & 68 & 21 & 68 \\
     &              &     96 &     58 &    343 &     32 \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSfig{10.5cm}{4691-f1.ps}{Brightness and color variations of V1057 Cyg in 1993--98.}

\references

Hartmann, L., Kenyon, S.J., 1996, {\it ARA\&A}, {\bf 34}, 207

Herbig, G.H., 1977, {\it ApJ}, {\bf 217}, 693

Ibrahimov, M.A., 1997, {\it Astr.\ Lett.}, {\bf 23}, 103

Ibrahimova, V.M., Ibrahimov M.A., 1997, {\it IBVS}, No.\,4479

Kolotilov, E.A., Kenyon, S.J., 1997, {\it IBVS}, No.\,4494

Landolt, A.U., 1983, {\it AJ}, {\bf 88}, 439


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