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\input ibvs2.sty

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\IBVShead{5260}{17 April 2002}

\IBVStitletl{GSC 1377-0969 (B\lowercase{rh} V65), GSC 0477-0889 (B\lowercase{rh} V100) and}{ GSC 0669-0674 (B\lowercase{rh} V102) are new W UM\lowercase{a} variables}

\IBVSsubtitle{(BAV Mitteilungen No. 150)}

\IBVSauth{Lloyd, C.$^{1}$; Frank, P.$^{2,5}$; Bernhard, K.$^{3,5}$; Moschner, W.$^{4,5}$}

\IBVSinst{Space Science \& Technology Department, Rutherford Appleton
Laboratory,
Chilton, Didcot, \\ \indent Oxon.\ OX11 0QX, UK, e-mail: {\tt cl@astro1.bnsc.rl.ac.uk}}
\IBVSinst{D--84149 Velden, Germany, e-mail: {\tt frank.velden@t-online.de}}
\IBVSinst{A--4030 Linz, Austria, e-mail: {\tt kl.bernhard@aon.at}}
\IBVSinst{D-57368 Lennestadt, Germany, e-mail: {\tt wolfgang.moschner@t-online.de}}
\IBVSinst{Bundesdeutsche Arbeitsge\-mein\-schaft f\"{u}r Ver\"{a}nderliche
Sterne e.V. (BAV), Munsterdamm 90,\\ \indent D--12169~Berlin, Germany}

\SIMBADobj{GSC 1377-0969}
\SIMBADobj{GSC 0477-0889}
\SIMBADobj{GSC 0669-0674}
\IBVStyp{ W UMa }
\IBVSkey{W UMa - variable stars - photometry}
\IBVSabs{CCD observations of the full light curves of these three new}
\IBVSabs{variable stars show that they are all W UMa variables with periods}
\IBVSabs{of 0.494514, 0.60933 and 0.38785 days respectively, and}
\IBVSabs{amplitudes of 0.15 - 0.35 mag.}

\begintext

The three stars described here result from a programme to discover and
classify new variables on the edge of the northern Milky Way. A
discussion of the first group of stars and a more detailed description of
the programme is given by Bernhard \& Lloyd (2000, Paper1). Further
information and an up-to-date list of the variables can be found at \\
{\tt http://mitglied.tripod.de/KlausBernhard/index.html}~.

\vskip 6pt
The survey and follow-up observations by Bernhard were made using a 20-cm
Schmidt-Cassegrain telescope with an unfiltered Starlight Xpress SX CCD
camera, with a Sony ICX027B chip. Further details are given in Paper 1.
The observations by Frank were made using a 30-cm flat-field camera and
an OES-LcCCD11 camera with a Kodak KAF-400 chip. An IR cut-off filter was
used for the later observations, those of Brh V100 and V102, but not for V65.
The observations of Moschner were made using a 32-cm Ritchey-Chr\'{e}tien
telescope with an unfiltered SBIG ST9 CCD camera and Kodak KAF-0261E
chip. All the detectors have a very broad response, peaking near 6000\AA,
giving approximate $V$ to $R$-band magnitudes, depending on the colour of
the star.

\vskip 6pt
The magnitudes of the variables are determined relative to an ensemble of
comparison stars and are then calibrated approximately with respect to
one reference star with a GSC magnitude. In most cases small offsets have
been applied to correctly align the data due to differences in the
instrumental response. 

\IBVSfig{8cm}{5260-f1.eps}{The phase diagram of GSC 1377-0969 = Brh V65
assuming that the reference star GSC 1377-0370 has $V=11\fmm5$. The CCD
observations of Moschner (open squares), Frank (open circles) and
Bernhard (filled circles) are folded with the ephemeris given in the
text. No relative offsets have been applied to the major data sets.}

GSC 1377-0969 = Brh V65 (Bernhard 2001a) (08\hr15\mm46\fsec8
+16\deg21\arcm57\arcs\ 2000) was re-observed after the survey
observations on six nights by Moschner and two nights by Frank in
February 2001, and February and March 2002. The reference star used was
GSC 1377-0370 ($V\approx11\fmm5$). Brh V65 has $b=12.3$ and $r=11.2$ in the
USNO A2.0 catalogue, and $B_T=12\fmm2\pm0\fmm2$ and $V_T=12\fmm3\pm0\fmm3$ in
the Tycho-2 catalogue. The light curve is almost sinusoidal so there is a
possible uncertainty of a factor of two in the period from the photometry
alone. However, an almost complete light curve has been observed by
Moschner which shows a small difference in alternate minima. The most
likely interpretation is that the star is a W UMa variable with almost
identical eclipses. The colour, although poorly determined, the range of
variation, 0\fmm35, and the galactic co-ordinates, $l=207, b=+26$, are
all consistent with this interpretation, and argue against it being a
$\beta$ Cephei or $\delta$ Scuti variable. In total seven eclipses have
been observed and the times of minima (and errors) are given in
Table 1. The light curve is shown in Figure 1 and the ephemeris of
primary minimum is given by

\[
\begin{array}{r@{}r@{}l}
HJD_{\rm MinI} = 2451968.495 & {} + 0\fday494514 & {} \times E. \\
\pm 1 & \pm 2 \\
\end{array}
\]


\begin{table}\centering
\normalsize
\caption{Brh V65 - Times of minima}
\vskip 2pt
\begin{tabular}{cccccc} \hline
HJD & $O-C$ & Min & HJD & $O-C$ & Min \\ \hline
2451955.3907(2)~ & +0.0003 & II & 2452321.3306(2) &$-0.0001$ & II\\ 
2451956.3787(2)~ & $-0.0007$& II & 2452338.3917(8)&+0.0002 & I~\\
2451964.2923(4)~ & +0.0007 & II & 2452342.3502(8) & +0.0026 & I~\\
2451968.4929(10) & $-0.0021$ & I~ \\ \hline
\end{tabular}
\end{table}


\IBVSfig{8cm}{5260-f2.eps}{The phase diagram of GSC 0477-0889 = Brh V100
assuming that the reference star GSC 0477-1815 has $V$=11\fmm1. The CCD
observations of Frank (open circles) and Bernhard (filled circles) are
folded with the ephemeris given in the text.}

\IBVSfig{8cm}{5260-f3.eps}{The phase diagram of GSC 0669-0674 = Brh V102
assuming that the reference star GSC 0669-0620 has $V=12\fmm0$. The CCD
observations of Bernhard (open circles), Frank (filled circles) and
Moschner (open squares) are folded with the ephemeris given in the text.}

GSC 0477-0889 = Brh V100 (Bernhard 2001b) (19\hr26\mm28\fsec1
+07\deg11\arcm49\arcs\ 2000,\ $l=43,\ b=-4$) is classed as non-stellar in
GSC 1.1 and 1.2 and does not appear in the USNO A2.0 catalogue, which
does note a faint companion at 8\arcs\ with $r=14.3$. The star does
appear in GSC 2.2 with $b=12.5$ and $r=11.3$. Brh V100 was observed on 14
nights during the survey phase and on a further two nights by Bernhard
and six nights by Frank, in August 2001. The reference star used was GSC
0477-1815 ($V\approx11\fmm1$). The period has been determined unambiguously
and the resulting light curve is shown in Figure 1. The two minima are
slightly unequal and suggest that the star is a W UMa variable. The
amplitude of 0\fmm15 and the GSC 2.2 colour are at least not inconsistent
with this interpretation. An almost complete light curve was observed by
Frank which shows a small but clear difference in the eclipses. The
ephemeris of primary minimum is

\[
\begin{array}{r@{}r@{}l}
HJD_{\rm MinI} = 2452140.960 & {} + 0\fday60926 & {} \times E. \\
\pm 2 & \pm 6 \\
\end{array}
\]

Following the initial observations by Bernhard (2002) GSC 0669-0674 = Brh
V102 (04\hr29\mm24\fsec9 +09\deg05\arcm31\arcs\ 2000) was observed on a
further night by Moschner and six nights by Frank, during January and
February 2002. The reference star used was GSC 0669-0620
($V\approx12\fmm0$). The period of Brh V102 has also been determined
unambiguously and the star is also shown to be a W UMa variable with an
amplitude of 0\fmm3. Frank observed a complete light curve and in this
case there is a clear difference between the two minima. The galactic
co-ordinates, $l=186, b=-26$, are consistent with this interpretation.
The $b-r$ colour from the GSC 2.2 and USNO A2.0 catalogues is 1.4 and 0.9
respectively, and while not well determined, is also consistent with the
classification. Times of minima from six eclipses are given in Table 2.
The ephemeris of primary minimum is

\[
\begin{array}{r@{}r@{}l}
HJD_{\rm MinI} = 2452308.291 & {} + 0\fday38786 & {} \times E. \\
\pm 1 & \pm 3 \\
\end{array}
\]

\begin{table}[!h]\centering
\normalsize
\caption{Brh V102 - Times of minima}
\vskip 2pt
\begin{tabular}{cccccc} \hline
HJD & $O-C$ & Min & HJD & $O-C$ & Min \\ \hline
2452307.3195(9) & $-0.0019$ & II & 2452309.4592(14)&+0.0046 & I~\\
2452308.2914(7) & +0.0004 & I~ & 2452310.4216(11)& $-0.0026$ & II\\
2452309.2610(6) & +0.0003 & II & 2452320.3142(4)~& $-0.0005$ & I~\\ \hline
\end{tabular}
\end{table}

\vskip 6pt
{\it Acknowledgements.} It is a pleasure the acknowledge the use of the 
SIMBAD database,
operated by the CDS at Strasbourg, France.


\references

Bernhard K., 2001a, vsnet-newvar, No. 757\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-newvar/msg00757.html

Bernhard K., 2001b, vsnet-newvar, No. 1058\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-newvar/msg01058.html

Bernhard K., 2002, vsnet-newvar, No, 1393; to appear at:\\
http: //www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-newvar/msg01393.html

Bernhard, K., Lloyd, C., 2000, {\it IBVS}, No.\ 4920

\endreferences

\end{document}

