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\begin{document}
\IBVShead{4685}{17 March 1999}

\IBVStitletl{DISCOVERY OF THE VARIABILITY}{ OF GSC 1009.766 AND GSC 1057.1309}

\IBVSauth{C.~LLOYD$^1$, K.~BERNHARD$^2$}

\IBVSinst{Space Science Department, Rutherford Appleton Laboratory,
Chilton, Didcot, Oxon. OX11 0QX, UK, e-mail: cl@ast.star.rl.ac.uk}
\IBVSinst{Kafkaweg 5, A-4030 Linz, Austria, e-mail: klaus.bernhard@vpn.at}

\SIMBADobj{GSC 1009-766 and GSC 1057-1309}
\IBVStyp{ unknown }
\IBVSkey{eclipsing binary, period, beta Cephei, delta Scuti }
\IBVSabs{Photometric observations of GSC 1009.766 show it to be an}
\IBVSabs{eclipsing binary with a period of 2.16252+/-0.00023 days.}
\IBVSabs{The epoch of primary minimum is JD 2451072.55+/-0.02. }
\IBVSabs{The light curve is Algol like, with minima about 0.5 and 0.1 }
\IBVSabs{magnitudes deep. The spectral type is unknown which allows a wide}
\IBVSabs{range of possible system parameters. }
\IBVSabs{GSC 1057.1309 is a short period variable, probably a}
\IBVSabs{beta Cephei or delta Scuti with a period of 0.172675 days,}
\IBVSabs{but three other periods are possible.}

\begintext

\vskip-1pt
CCD observations of selected fields on the edge of the northern Milky Way
have been made as part of a programme to discover and classify
new variables (eg.\ Bernhard et al.\ 1997, Bernhard 1999).
In this paper the observations of two new variables resulting from this
programme are reported.
GSC 1009.766 is an EA binary with a period of 2.16252 days
and GSC 1057.1309 is a short-period variable, possibly a $\beta$ Cephei,
$\delta$ Scuti or W~UMa variable.
Following the practice in previous reports of discoveries from this programme 
these stars are also referred to as BeV7 and BeV8 respectively.
The observations were made using a 20-cm Schmidt-Cassegrain telescope and
a Starlight Xpress SX CCD camera without filter. In each observing run
typically 300 images are taken of several survey fields.
The CCD camera uses a Sony
ICX027B chip which has a very broad response, peaking near 5500 \AA, 
giving approximate V-band magnitudes. 
The frames are processed automatically; de-biased using a mean dark frame 
and flat fielded. The magnitudes are derived using a simple aperture
photometry procedure with a 5$\times$5 pixel square for the star+sky and
7$\times$7 pixel square window frame for the sky.

\bigskip\noindent
GSC 1009.766

\smallskip 
GSC 1009.766 is classified as non stellar in the Guide Star Catalog
and this is attributable to a faint companion, which is clearly seen on the
CCD images, but is not completely resolved from the brighter, variable 
component. The separation between the two components is estimated to be
about 2 pixels, or $\sim$5 arcsec on the sky. 
All the
magnitude estimates of GSC 1009.766 completely include the faint companion. 
Examination of the images suggests that the faint companion is {\it
slightly\/} fainter than the variable at minimum light, although this
estimate is rather subjective.
The comparison stars used were GSC 1009.1116 (GSC 11.0) and GSC 1009.842
(12.2), and showed a constant magnitude difference consistent with the
GSC magnitudes. The magnitude scale used assumes that GSC 1009.1116 has V
= 11.0.

\IBVSfig{10cm}{4685-f1.eps}{The observed light curve of GSC 1009.766
with a photometric solution, assuming no contribution from the faint
companion}

\IBVSfig{10cm}{4685-f2.eps}{The relative light curve of GSC 1009.766
corrected for the contribution from the faint companion, with a solution
over plotted.}

\IBVSfig{10cm}{4685-f3.eps}{The light curve of GSC 1057.1309 folded
with a period of 0.172675 days.}

\IBVSfig{10cm}{4685-f4.eps}{The light curve GSC 1057.1309 folded
with a period of 0.417570 days.}

\vskip-43pt
GSC 1009.766 was observed 113 times during the second half 1998.
Initially, during the survey phase the observations are relatively sparse
but following the discovery of variations the star was observed more
intensively. 
The observations show GSC 1009.766 to be an Algol-type 
eclipsing binary with
primary and secondary eclipses of $\sim$ 0.5 and 0.1 mag respectively.
The ephemeris of primary minimum is
$$
{\rm Min.\ I} = {\rm JD} 2\,451\,072.55(\pm 0.02) + 2\fday16252(\pm 0.00023) \times E.
$$
Attempts to produce viable light curves with alias periods have failed,
so insofar as it is possible to determine, this period is unambiguous. 


An attempt has been made to model the system using the {\sc Light2} code
of Hill et al.\ (1989). 
In the first instance it has been assumed that the faint
companion makes no contribution to the light curve. The solution
plotted over the observed light curve is shown in Figure 1. For the
second solution the faint companion was assumed to contribute a constant
luminosity equivalent to the variable at minimum light (which is probably
too large) and the light curve had this constant component removed. The
corrected relative light curve and solution are shown in Figure 2.

Without any other photometric or spectroscopic information
about this system the photometric solutions are poorly constrained. A
wide range of system parameters give very similar light curves. The ratio of
stellar temperatures is $\sim$\,1.5--2, although the temperatures themselves
are largely unconstrained. The radii of the two stars are broadly similar but
secondaries both larger and smaller than the primary are possible
depending on the mass ratio. The solutions in which the secondary is
constrained to fill its Roche lobe are equally consistent with the light
curve. For the solution plotted in Figure 1 the secondary fills its Roche
lobe and the other parameters are; $T_{1}=10000$ K (fixed),
$T_{2}=5200\pm400$ K, $R_{1}/a=0.22\pm0.02$, $R_{2}/a=0.30$ (fixed),
$i=71\pm1$, $q=0.5$ (fixed). A similar solution is shown in Figure 2 for
the corrected light curve.
The true variation of GSC 1009.766 will lie between these two extremes
(with $\Delta$V between 0.5 and 0.8 mag)
and the evidence suggests it is a classical Algol binary.

\bigskip\noindent
GSC 1057.1309

\smallskip 
GSC 1057.1309 was observed 163 times between July and November 1998
with several runs of approximately 20 observations. The magnitudes are
given relative to GSC 1057.1973 (11.8) and the second comparison star
used was GSC 1057.1527 (12.7). From a period analysis of the observations
GSC 1057.1309 appears to be a short period variable although it is not
possible to derive the period unambiguously. Four possible periods
emerge, two with single maxima and minima, characteristic of a $\beta$
Cephei or $\delta$ Scuti variable, and double these periods, giving two
maxima and minima, characteristic of a W UMa variable. Arguably the most
likely period is 0.172675$\pm$0.000006 days, which is shown in Figure 3,
although there is some suggestion of secondary variations superimposed.
For a $\beta$ Cephei or $\delta$ Scuti variable other periods may be
present which would easily account for this additional variation. The
other single maximum period is 0.208791$\pm$0.000007 days which shows a
very similar variation and evidence of possible secondary periods.

The two other periods, 0.345346$\pm$0.000010 and 0.417570$\pm$0.000015 days,
show W UMa-like light curves, but there are asymmetries in slope and
differences in both the maxima and minima which are not typical of
classical W~UMa stars. 
These light curves also show scatter that would have to
be interpreted as cycle to cycle variation.
The light curve of the 0.417570 days period is shown in Figure 4.

\references

Bernhard K., Quester W., Bastian U., 1997, {\it IBVS}, No.,4540

Bernhard K., 1999, {\it Der Sternenbote}, 2/1999, Astronomisches
Buero, A-1238 Wien p.\ 34

Hill G., Fisher W.A., Holmgren D., 1989, {\it A\&A} {\bf 211}, 81

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