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\IBVShead{4998}{7 December 2000}

\IBVStitletl{Light Elements and a Preliminary Solution for the}{ Light Curve of the Eclipsing Binary GSC 1534.0753}

\IBVSauth{Lubcke, G.C.$^1$; Baldwin, M.E.$^2$; Billings, G.W.$^3$; Guilbault, P.R.$^4$; Hager, T.$^5$;\\ \indent Henden, A.A.$^6$; Terrell, D.$^7$}

\IBVSinst{3817 Patrick Henry Way, Middleton, Wisconsin 53562, USA,
e-mail: gil2@ix.netcom.com}

\IBVSinst{8655 N. Co.\ Road 775 E, Butlerville, Indiana 47223,
USA, e-mail: mbald00@hsonline.net}

\IBVSinst{2320 Cherokee Drive NW, Calgary, Alberta, Canada T2L
OX7, e-mail: obs681@telusplanet.net}

\IBVSinst{P.O. Box 287, Chepachet, Rhode Island 02814, USA, e-mail: pete1199@aol.com}

\IBVSinst{34 Mount Tom Road, New Milford, Connecticut 06776, USA,
e-mail: thager@pcnet.com}

\IBVSinst{Universities Space Research Association/U.S. Naval
Observatory, P.O. Box 1149, Flagstaff, \\ \indent Arizona
86002-1149, USA, e-mail: aah@nofs.navy.mil}

\IBVSinst{Dept.\ of Space Studies, Southwest Research Institute,
1050 Walnut St., Suite 426 Boulder, CO 80302, \\ \indent e-mail: terrell@boulder.swri.edu}

\IBVSabs{We report on the variability of GSC 1534.0753}

\SIMBADobj{GSC 1534-0753}

\IBVStyp{  EB  }

\begintext

The ROTSE1 CCD survey (Akerlof et al., 2000) has discovered many new
variables, a large number of which are eclipsing binary stars. A group
of AAVSO members using CCD, visual and photographic observations have
observed GSC 1534.0753 = ROTSE1 J170250.47.  In this note we report the
results of our investigation which include precision light elements and
a light curve, as well as standard $UBVRI$ magnitudes for the variable
and comparison stars. We also present a preliminary solution for the
light curve using the Wilson--Devinney program.

Baldwin began a program of  intensive visual monitoring of the star. A
total of 69 observations were made over 24 nights. The star was seen in
eclipse on five nights and from these observations preliminary
light elements were determined. At the same time, Guilbault and Hager
examined 211 photographic plates at the Harvard College Observatory.
These photographic data enabled the elements to be further refined so
that CCD observations could commence.

Lubcke observed the system with a 0.28-m  Schmidt--Cassegrain
telescope (SCT) equip\-ped with an ST9E CCD camera from his private
observatory. Billings used a 0.35-m SCT with a AP-7 CCD to
observe the star at secondary minimum. The star was observed from
JD 2451748 to JD 2451777 in the $V$ passband. A total of 517 CCD
observations were made and from these data five times of
primary minimum and three times of secondary minimum were
extracted. The times of primary minimum from all sources appear
in Table 1.

\begin{table}[t]
\caption{Times of primary minimum, GSC 1534.0753}
\begin{center}
\begin{tabular}{cccccc}
\hline
HJD 2400000\,+ & Error $\pm$ &  Epoch & $O-C$   &   Observer     &  Type\\
\hline

43335.669     &-          &$-$16494 & $-$0.002  & Harvard     &   ptg\\
43659.740     &-          &$-$15860 & $-$0.004  & Harvard     &   ptg\\
43960.833     &-          &$-$15271 & $+$0.018  & Harvard     &   ptg\\
44045.671     &-          &$-$15105 & $+$0.004  & Harvard     &   ptg\\
44540.474     &-          &$-$14137 & $+$0.009  & Harvard     &   ptg\\
45170.699     &-          &$-$12904 & $-$0.021  & Harvard     &   ptg\\
45556.633     &-          &$-$12149 & $-$0.010  & Harvard     &   ptg\\
45618.490     &-          &$-$12028 & $-$0.003  & Harvard     &   ptg\\
45963.513     &-          &$-$11353 & $-$0.010  & Harvard     &   ptg\\
46028.456     &-          &$-$11226 & $+$0.016  & Harvard     &   ptg\\
46590.729     &-          &$-$10126 & $+$0.018  & Harvard     &   ptg\\
46612.652     &-          &$-$10083 & $-$0.039  & Harvard     &   ptg\\
46674.543     &-          &$-$9962  & $+$0.002  & Harvard     &   ptg\\
46937.806     &-          &$-$9447  & $+$0.020  & Harvard     &   ptg\\
46999.649     &-          &$-$9326  & $+$0.013  & Harvard     &   ptg\\
47084.489     &-          &$-$9160  & $+$0.001  & Harvard     &   ptg\\
47085.496     &-          &$-$9158  & $-$0.014  & Harvard     &   ptg\\
51748.7831     & 0.0009    & $-$35  & $-$0.001   & Lubcke     &   CCD, $V$ filter\\
51763.6073     & 0.0009    & $-$6   & $-$0.000   & Lubcke     &   CCD, $V$ filter\\
51764.6315     & 0.0015    & $-4$   & $+$0.002   & Lubcke     &   CCD, $V$ filter\\
51766.6744     & 0.0002    & $+0$   & $-$0.000   & Lubcke     &   CCD, $V$ filter\\
51767.6961     & 0.0002    & $+2$   & $-$0.001   & Lubcke     &   CCD, $V$ filter\\
\hline
\end{tabular}
\end{center}
\end{table}

From the Harvard minima listed above a period of 0\fday5111552 was
determined. The exposure time of the plates was generally one
hour and the mid-point of the exposure is the time of minimum.
The CCD minima were determined with the computer program {\it AVE\/}
(Barbera, 2000) which uses the Kwee--van Woerden (1956) method.
In order to refine the period further, a least squares solution
was applied to all minima shown in Table 1. The CCD minima were
weighted as 100 and the photographic minima were weighted as 1.
From that analysis we extracted the best period and combined with
the most accurate time of minimum to yield the following light
elements:
$$ \begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~} 2451766.6744 & {} + 0\fday51115576 & {} \times E.\\
\pm 0.0001 &  \pm 0.00000005 \\
\end{array} $$

The CCD observations in the $V$ passband were folded using the
elements above and the phased and normalized $V$ light curve is
shown in Figure 1. For the purpose of illustration the brightness
of the variable is expressed in light units rather than
magnitudes. The light curve varies continuously between eclipses
and indicates that GSC 1534.0753 is a Beta Lyrae (EB) type
eclipsing binary with one or both of the components being highly
ellipsoidal.

In the instrumental system our $V$-filtered observations
indicate that the star fades from a maximum of $11\fmm94\pm0.01$
to $13\fmm09\pm0.01$ at primary minimum. A secondary eclipse with
a depth of $0\fmm50\pm0.01$ occurs at phase 0.50.

From the US Naval Observatory's Flagstaff Station, Henden used
the 1.0-m telescope and an SITe/Tektronix $1024\times1024$ CCD to observe
the field of GSC 1534.0753. On four photometric nights
observations were made in the $UBVRI$ bandpasses with magnitude
and color errors less than 0\fmm01. The comparison (GSC
1534.1027) and check (GSC 1534.0962) stars were standardized as
follows:

\newpage

\IBVSfig{10cm}{4998-f1.eps}{Phased and normalized $V$ light curve
and star figures\\ based on the preliminary solution}

\begin{table}[h]
\caption{Comparison stars}
\begin{center}
\begin{tabular}{lrrccccc}
\hline
Star & \multicolumn2c{RA (J2000) DEC} & $V$ & $B-V$ & $U-B$ & $V-R$ & $R-I$ \\
\hline
Comp.&17:02:54.93 &+21:36:36.5 &12.451&0.609&0.081&0.354&0.336\\
Check&17:02:29.25 &+21:44:40.8 &12.607&0.589&0.281&0.378&0.348\\
\hline
\end{tabular}
\end{center}
\end{table}

\vskip-12pt
Extensive photometric information about all stars within 5 arcmin
of the variable is available in Henden (2000). Using these stars,
and again with errors less than 0\fmm01,  the magnitude and color
indices of GSC 1534.0753 at four different epochs were determined as:
\begin{center}
\begin{tabular}{ccccccc} \hline
HJD 2400000\,+& Phase &$V$ & $B-V$ & $U-B$ & $V-R$ & $R-I$ \\
\hline
51754.6881 & 0.4494 & 12.324 & 0.723 & 0.247 & 0.405 & 0.358 \\
51757.6891 & 0.5784 & 12.256 & 0.765 & 0.319 & 0.445 & 0.399 \\
51761.7423 & 0.6489 & 12.084 & 0.765 & 0.315 & 0.446 & 0.388 \\
51791.6953 & 0.9497 & 12.656 & 0.861 & 0.571 & 0.500 & 0.451 \\
\hline
\end{tabular}
\end{center}

The colors suggest that the primary star is approximately spectral
type G8 with a temperature of 5300 K using the Flower (1996)
tables.

Terrell used the latest version of the Wilson--Devinney program
(Wilson and Devinney, 1971; Wilson, 1979) to arrive at a
preliminary solution for the system parameters. Inspection of
Figure 1 shows that the system has a noticeable O'Connell effect
(Davidge and Milone, 1984). To model this asymmetry in the maxima,
two spots were used on the hotter component. While the available
data are insufficient to reliably determine the properties of any
spots in the system, the solution illustrates the nature of the
asymmetries. Table 3 shows the parameters of the best-fit solution
which should be regarded as provisional until further data, in
particular radial velocities, can be obtained. As seen in Figure 1,
the solution shows the system to be in marginal contact with the
less-massive star eclipsed at primary minimum. The poor thermal contact
suggests that the system may be a B-type W UMa system
(Lucy and Wilson, 1979).

\begin{table}[h]
\begin{center}
\caption{Solution parameters}
\begin{tabular}{ccc} 
\hline
Parameter &  Value & Std.\ deviation \\
\hline
$i$ & $82\fdeg6$ & 0\fdeg12 \\
$T_1$ & 5300 K &  \\
$T_2$ & 4483 K & 5 K \\
$\Omega$ & 4.190 & 0.017 \\
$M_2/M_1$ & 1.28 & 0.01 \\
${(L_1/L_2)}_V$ & 1.96 & \\
\hline
\end{tabular}

\bigskip

\caption{Spot parameters} 
\begin{tabular}{cccccccc}
\hline
Star &  Co-Latitude (rad) & Longitude (rad) & Radius (rad) & Temperature factor \\
\hline
 1  &    1.57   &   1.0   &   0.10   &   1.20 \\
 1  &    1.57   &   6.0   &   0.15   &   0.88 \\
\hline
\end{tabular}
\end{center}
\end{table}

We wish to thank Dr.\ Martha Hazen, Curator of the Astronomical
Photographic Collection at the Harvard College Observatory, for
allowing us to use the plates for this and other projects. We are
grateful to Dan Kaiser of the AAVSO for his valuable help in the
preparation of this report. GWB acknowledges the use of software
(KAPPA, PHOTOM) provided by the Starlink Project which is run by
CCLRC on behalf of PPARC.

\references

Akerlof, C., et al., 2000, {\it AJ}, {\bf 119}, 1901

Barbera, R., {\tt http://www.gea.cesca.es}

Davidge, T.J. and Milone, E.F, 1984, {\it ApJS}, {\bf 55}, 571

Flower, P.J., 1996, {\it ApJ}, {\bf 469}, 355

Kwee, K. K., and van Woerden, H., 1956, {\it BAN}, {\bf
12}, No.\ 464, 327

Henden, A., 2000,\\ {\tt
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/g1534.dat}

Lucy, L.B., and Wilson, R.E., 1979, {\it ApJ}, {\bf 231}, 502

Wilson, R.E., 1979, {\it ApJ}, {\bf 234}, 1054

Wilson, R.E., and Devinney, E.J., 1971, {\it ApJ}, {\bf 166}, 605

\endreferences


\IBVSedata{4998-t5.txt}

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