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\IBVShead{4981}{7 November 2000}

\IBVStitletl{GSC 2293-1021:}{ a Newly Discovered W Ursae Majoris Variable}

\IBVSauth{Liu, Z. L.; Zhou, A. Y.; Xu, D. W.; Lu, Y.}

\IBVSinsto{Beijing Astronomical Observatory, Chinese Academy of Sciences,
Beijing 100012, P.R. China, \\ \indent
e-mail: lzl@bao.ac.cn }

\SIMBADobj{GSC 2293-1021}
\IBVStyp{ DSCT }
\IBVSkey{photometry}
\IBVSabs{This note presents the discovery of a new W UMa-type variable}
\IBVSabs{GSC 2293-1021 (RA = 01h 28m 54s, DEC = 30d 08' 02", }
\IBVSabs{equinox = 1950.0, 14.1 V), which shows a 0.13 day periodic variation.}

\begintext

The new variable star GSC 2293-1021 ($\alpha=01\hr28\mm54\fsec54$,
$\delta=30\deg08\arcm02\farcs7$, B1950, $V=14.1$) was chosen as one of
the comparison stars during the observations of the high-amplitude
$\delta$ Scuti variable UV~Tri. GSC 2293-1021 was first suspected to be
a variable star on November 17, 1999. Since then, it was observed until
January 2000 using the red-sensitive Thomson TH 7882 CCD photometer
(Wei et al.\ 1990) attached to the 85-cm Cassegrain telescope at the
Xinglong Station of the Beijing Astronomical Observatory (BAO). The
dimensions of the CCD detector are 13.25 mm${}\times{}$8.83 mm,
consisting of $576\times384$ pixels, which corresponds to a sky
field-of-view of $12\farcm3\times8\farcm4$. The Johnson $V$ filter and
5 comparison stars ($C_{1}$, $C_{2}$, $C_{3}$, $C_{4}$, $C_{5})$ were
used.
$C_{1}$ = GSC 2293-1422 ($\alpha=01\hr29\mm15\fsec73$,
$\delta=30\deg06\arcm08\farcs4$, B1950, $V=13.4$),
$C_{2}$ = GSC 2293-1028 ($\alpha=01\hr29\mm19\fsec64$,
$\delta=30\deg08\arcm13\farcs4$, B1950, $V=12.9$),
$C_{3}$ = GSC 2293-1027 ($\alpha=01\hr29\mm11\fsec76$,
$\delta=30\deg11\arcm53\farcs2$, B1950, $V=13.6$),
$C_{4}$ = GSC 2293-1461 ($\alpha=01\hr29\mm13\fsec83$,
$\delta=30\deg02\arcm19\farcs6$, B1950, $V=14.0$),
$C_{5}$ = GSC 2293-1456 ($\alpha=01\hr29\mm03\fsec60$,
$\delta=30\deg05\arcm54\farcs8$, B1950, $V=14.1$).
The relative positions of the new variable and the comparison stars are shown
in Fig.~1.  Depending on the weather conditions from night to night, different
exposure times (ranging from 20 to 80 seconds) were used. No variability higher
than 0.01 mag was found for any of the 5 comparison stars. However, we found
the magnitude difference between GSC 2293-1021 and all other comparison stars
to vary as a sine-like curve. We used Hao's (1991) program and {\sc PERIOD96}
(Sperl 1996) to complete the period analysis. An oscillation frequency of 7.665
cd$^{-1}$ (period${}={}$0.131 days) was obtained. However, we found the magnitudes
of both maxima to be unequal. So, we think that this might indicate two
eclipses evenly spaced with a period of 0.262 days. The light curve of two
nights of observations folded with $P=0.262$ days is shown in Fig.~2.  To
identify the type of the new variable star, we obtained two spectra on February
6 and March 11, 2000 using the low-dispersion Cassegrain spectrograph of the
2.16-m telescope at the Xinglong Station of BAO. The spectrum of GSC 2293-1021
obtained on March 11, 2000 is shown in Fig.~3. In addition to two O$_{2}$
telluric bands at 6870~\AA\ and 7620~\AA, some neutral metal lines, such as Na
ID (5890~\AA, 5896~\AA), Cr I (5192~\AA, 5273~\AA, 7219~\AA), and Ca I
(5601~\AA), can easily be identified the spectrum. Thus, we estimate the
spectral type of GSC 2293-1021 to be between late-G and early-K. According to
the spectral type and the shape of the folded light curve, we think that this
may be a W Ursae Majoris type variable.

\IBVSfig{10cm}{4981-f1.ps}{Identification chart of the new variable GSC
2293-1021 (labelled ``6'') and 5 comparison stars denoted with No. 1--5
respectively. The scale of the field is marked on the right bottom part. North
is up and East is to the left}

\IBVSfig{8cm}{4981-f2.eps}{Folded light curve of GSC 2293-1021. The ordinate,
$\Delta V$, is the magnitude difference between the new variable star and
the comparison star $C_{1}$}

\IBVSfig{10.5cm}{4981-f3.eps}{Spectrum of GSC 2293-1021 obtained on March 11,
2000. The ordinate is relative intensity}

{\it Acknowledgements.} We acknowledge the grant from the National
Natural Science Fund of China.

\references

Hao J.X., 1991, {\it Publ.\ of Beijing Astron.\ Obs.}, {\bf 18}, 35

Sperl M., 1996, {\it Delta Scuti Star Newsletter}, {\bf 10}, 5 (Vienna)
% Original: Sperl M., 1996, {\it Delta Scuti Star Newsletter} (Vienna), {\bf 10}, 5
% Corrected: Thu Aug 14 11:06:40 MET DST 2003

Wei M.Z., Chen J.S., Jiang Z.J., 1990, {\it PASP}, {\bf 102}, 698


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