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\input ibvs2.sty
\input ibvst.sty

\begin{document}

\IBVShead{4996}{6 December 2000}

\IBVStitletl{CCD Light Curves of ROTSE1 Variables, VIII:}{ GSC\,3920.882 Cygni, GSC\,3547.216 Cygni, GSC\,3921.1531 Cygni}

\IBVSauth{Bl\"attler, E.$^1$; Diethelm, R.$^2$}

\IBVSinst{BBSAG, Schl\"usselacher 1, CH-8636 Wald,
Switzerland; e-mail: blaettler-wald@bluewin.ch}

\IBVSinst{BBSAG, Rennweg 1, CH-4118 Rodersdorf, Switzerland; e-mail: diethelm@astro.unibas.ch}

\SIMBADobj{GSC 3920-882}
\SIMBADobj{GSC 3547-216}
\SIMBADobj{GSC 3921-1531}

\begintext

{\bf VAR1}\smallskip\hrule

\IBVSTnam{GSC\,3920.882 = ROTSE1 J191635.07+524853.6}

\IBVSTcoo{19\hr 16\mm 35.07\sec}{+52\deg 48\arcm 53.6\arcs}{2000.0}

\IBVSTcomp{GSC\,3920.760}
 
\IBVSTchk{GSC\,3920.1408}

{\bf VAR2}\smallskip\hrule

\IBVSTnam{GSC\,3547.216 = ROTSE1 J192143.82+480356.3}

\IBVSTcoo{19\hr 21\mm 43.82\sec}{+48\deg 03\arcm 56.3\arcs}{2000.0}

\IBVSTcomp{GSC\,3547.1774}

\IBVSTchk{GSC\,3547.1876}

{\bf VAR3}\smallskip\hrule

\IBVSTnam{GSC\,3921.1531 = ROTSE1 J192537.72+532520.0}

\IBVSTcoo{19\hr 25\mm 37.72\sec}{+53\deg 25\arcm 20.0\arcs}{2000.0}

\IBVSTcomp{GSC\,3921.1760}

\IBVSTchk{GSC\,3921.1595}

\IBVSfig{10cm}{4996-f1.eps}{CCD light curve (without filter) of GSC\,3920.882}

\IBVSfig{10cm}{4996-f2.eps}{CCD light curve (without filter) of GSC\,3547.216}

\IBVSfig{10cm}{4996-f3.eps}{CCD light curve (without filter) of GSC\,3921.1531}

\hrule

\IBVSTobs{Private observatory, Schl\"usselacher, Wald,
0.15-m refractor}

\IBVSTdet{SBIG ST-7 CCD camera}

\IBVSTfil{None}

\IBVSTdata{Upon request from diethelm@astro.unibas.ch} %email


\IBVSTtyp{ EW (possibly $\delta$ Sct [VAR3]) }

\newpage

\IBVSTrem{
As a byproduct of the ROTSE1 CCD survey, a large number of new
variables have been discovered (Akerlof et al., 2000). In a series of
papers, we report unfiltered CCD observations for some of the close
binary systems (type EW and E) in the list of Akerlof et al.\ (2000).
GSC\,3920.882 (VAR1 in this paper) was observed with our CCD equipment
as mentioned above during 5 nights between JD\,2451806 and JD\,2451850,
while the data on GSC\,3547.216 (here VAR2) was collected during 4
nights between JD\,2451809 and JD\,2451850. In the case of
GSC\,3921.1531 (VAR3), we obtained the data in 6 nights between
JD\,2451801 and JD\,2451850. A total of 158 CCD frames were measured
for VAR1, 164 frames for VAR2 and 166 frames for VAR3. Figures 1, 2 and
3 show our observations folded with the elements
\begin{center}
\begin{tabular}{ll}
GSC\,3920.882: & ${\rm JD(min,hel)} = 2451806.4044(44) + 0.361812(20) \times E$; \\
GSC\,3547.216: & ${\rm JD(min,hel)} = 2451806.4870(9) + 0.353358(6) \times E$; \\
GSC\,3921.1531: & ${\rm JD(min,hel)} = 2451811.3124(9) + 0.3359535(12) \times E$ \\
& (see note in the text). \\
\end{tabular}
\end{center}
These elements of variation are deduced from a linear fit to the newly
determined normal minima from the ROTSE1 data (VAR1: JDH\,2451312.7120(4),
secondary; VAR2: JDH\,2451259.8407(1), primary, JDH\,2451291.8229(15),
secondary; VAR3: JDH\,2451258.8357(6), secondary (?), JDH\,2451308.7271(5),
primary (?)) as well as the minima derived from our data and given in 
Bl\"attler (2001).\\
The light curve of GSC\,3920.882 (VAR1) shows much more scatter than could
be expected from the accuracy of the photometry. This might be due to
intrinsic variability or erroneous classification, because variability of the
comparison star can be ruled out.\\
GSC\,3921.1531 (VAR3) shows a small amplitude and minima as well as
maxima of equal brightness. Therefore, it might well be that this star
is a pulsating variable of the $\delta$ Scuti type and half the period
value stated in the elements above. Since we have no colour
information, a definitive conclusion is not possible at the moment.}

\IBVSTack{This research made use of the Simbad data base, operated
at CDS, Strasbourg, France.}

\references

Akerlof, C., Amrose, S., Balsano, R., Bloch, J., Casperson, D., Fletcher,
S., Gisler, G., Hills, J., Kehoe, R., Lee, B., Marshall, S., McKay, T.,
Pawl, A., Schaefer, J., Szymanski, J., Wren, J., 2000, {\it AJ}, {\bf 119}, 
1901

Bl\"attler, E., 2001, {\it BBSAG Bulletin}, {\bf 124}, in preparation

\end{document}
