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\IBVShead{4989}{28 November 2000}

\IBVStitle{New Field Variable Stars III\IBVSfm}
\IBVSfoot{Based on observations taken at the German--Spanish
Astronomical Centre, Calar Alto, operated by the Max-Planck-Institute
for Astronomy, Heidelberg, jointly with the Spanish National Commission
for Astronomy}


\IBVSauth{Cs\'ak, B.$^{1,4}$; Kiss, L.L.$^{2,4}$; Szab\'o, Gy.$^{2,4}$; Szil\'adi, K.$^{2,4}$; S\'arneczky, K.$^{3,4}$}

\IBVSinst{Department of Optics \& Quantum Electronics and Astronomical
Observatory, University of Szeged,\\ \indent
P.O. Box 406, H-6701 Hungary, e-mail: csakb@neptun.physx.u-szeged.hu}

\IBVSinst{Department of Experimental Physics and Astronomical Observatory,
University of Szeged}

\IBVSinst{Department of Physical Geography, ELTE University, Hungary}

\IBVSinst{Guest Observer at the Konkoly Observatory}

\IBVStyp{ EA, EW, DSCT }
\IBVSkey{CCD photometry}
\IBVSabs{We report the discovery of thirteen new field variable stars based on}
\IBVSabs{CCD observations carried out between April and July, 2000. The}
\IBVSabs{obtained light curves do not enable an accurate classification. The}
\IBVSabs{shapes of light curves suggest eclipsing binary nature for the}
\IBVSabs{majority of new variable stars.}

\begintext

We have continued the search for new short period variable stars on the
CCD frames made for photometry and astrometry of minor planets (see
Cs\'ak et al.\ 2000ab, Paper~1, Paper~2). In this note we report the
discovery of thirteen new variable stars found between April and July,
2000.

The observations in Hungary leading to the discovery of V18 were
carried out with the 60/90/180 cm Schmidt telescope of the
Piszk\'estet\H{o} Mountain Station of the Konkoly Observatory.  The
detector was a Photometrics AT200 CCD camera (1536$\times$1024 pixels)
giving a $29\arcm\times18\arcm$ field of view (FOV).  The majority of
the presented new variable stars was discovered with the 1.23-m
telescope of the German--Spanish Astronomical Center at Calar Alto,
Spain. The applied instruments was a SITe\#2b CCD camera
($2048\times2048$ pixels) yielding to a $17\arcm\times17\arcm$ FOV\@.
The observations were made through Cousins $R_C$ filter at both
places.  The exposure time was chosen between 1--5 minutes, depending on
the brightness of the target asteroids (Szab\'o et al., in
preparation).

The data reduction and analysing methods were the same that described
in Paper~1. The candidate new variables were checked in the SIMBAD
Database. We have to note that although two fields (those of V24 and
V25) were also observed by the FASTT instrument (Henden \& Stone 1998,
Stone et al.\ 1999) down to a limiting magnitude of 17.8 ($R$), both
stars escaped the detection as variable stars. The only possible hint
for variation is the larger photometric error of V25 in Stone et
al.\ (1999). V27 was identified with GSC~03947-01632 using Guide CD-ROM
Star Chart (1997).  The light curves of 13 new variables are plotted in
Figures~1--3. The individual measurements are available upon request
from the first author.

The basic data of these stars (celestial coordinates,
USNO-A2.0 blue and red magnitudes and suspected types)
are summarized in Table~1. The type of variability is exclusively
based on the light curve shape, thus it is likely to be quite uncertain
in some cases. Follow-up observations are desirable to provide more reliable
classification for most of the stars.


\IBVSfig{15cm}{4989-f1.eps}{Light curves of 6 new variable stars}

\IBVSfig{15cm}{4989-f2.eps}{Light curves of 6 new variable stars}

\IBVSfig{5cm}{4989-f3.eps}{Light curve of the new variable star V30}

\begin{table}
\begin{center}
\caption{Basic data of the new variables. The coordinates,
red and blue magnitudes were taken from USNO-A2.0. The coordinates for
V24 and V25 are the improved values from Stone et al.\ (1999).
The given types are based on the light curve shapes, thus they should
be considered as approximative ones.}
\vskip2mm
\begin{tabular} {clclll}
\hline
Variable & R.A. (2000) & Dec.\ (2000) & Red mag. & Blue mag. & Type\\
\hline
V18 & 08\hr26\mm32\fsec5 & +09\deg43\arcm18\farcs2 & 17.1 & 19.7 & --\\
V19 & 17\hr33\mm08\fsec2 & +10\deg43\arcm16\farcs5 & 18.3 & 19.2 & eclipsing\\
V20 & 17\hr33\mm20\fsec2 & +10\deg46\arcm09\farcs4 & 17.5 & 19.1 & pulsating\\
V21 & 17\hr33\mm24\fsec3 & +10\deg47\arcm03\farcs0 & 17.8 & 19.3 & pulsating\\
V22 & 17\hr33\mm39\fsec0 & +10\deg47\arcm02\farcs9 & 18.6 & 19.5 & --\\
V23 & 17\hr33\mm53\fsec5 & +10\deg49\arcm25\farcs6 & 18.4 & 20.3 & --\\
V24 & 18\hr03\mm58\fsec7 & +00\deg59\arcm53\farcs9 & 16.9 & 18.4 & --\\
V25 & 18\hr04\mm16\fsec8 & +01\deg02\arcm52\farcs0 & 15.2 & 17.5 & eclipsing\\
V26 & 19\hr55\mm21\fsec5 & +58\deg33\arcm30\farcs9 & 16.9 & 18.2 & --\\
V27 & 19\hr56\mm18\fsec9 & +58\deg35\arcm17\farcs3 & 14.0 & 14.1 & eclipsing\\
    &                    &                         & 13.4$^a$    &          \\
V28 & 19\hr56\mm23\fsec9 & +58\deg43\arcm07\farcs2 & 17.7 & 19.3 & --\\
V29 & 20\hr18\mm31\fsec4 & +60\deg41\arcm18\farcs8 & 17.6 & 18.5 & eclipsing\\
V30 & 20\hr18\mm36\fsec2 & +60\deg37\arcm03\farcs0 & 18.1 & 20.0 & --\\
\hline
\multicolumn6l{$^a$ V27 = GSC~03947-01632}
\end{tabular}
\end{center}
\end{table}

{\it Acknowledgements:} This work has been supported by OTKA Grant \#T032258,
Pro Renovanda Cultura Hungariae Foundation Grant DT 2000 m\'aj./43,
m\'aj./44, m\'aj./48, and ``Bolyai J\'anos'' Research Scholarship
of LLK from the Hungarian Academy of Sciences.
The warm hospitality of the staff of the Konkoly Observatory
and Calar Alto Observatory is gratefully acknowledged.
We used the SIMBAD database, operated at CDS, Strasbourg, France.

\references

Cs\'ak, B., Kiss, L.L., Szab\'o, Gy., S\'arneczky, K., Szil\'adi, K., 2000a,
{\it IBVS}, No.\ 4875

Cs\'ak, B., Kiss, L.L., Szil\'adi, K., S\'arneczky, K., Szab\'o, Gy., 2000b,
{\it IBVS}, No.\ 4881

Guide CD-ROM Star Chart, 1997, Project Pluto, {\tt http://www.projectpluto.com}

Henden, A.A., Stone, R.C., 1998, {\it AJ}, {\bf 115}, 296

Stone, R.C., Pier, J.R., Monet, D.G., 1999, {\it AJ}, {\bf 118}, 2488

Szab\'o, Gy., S\'arneczky, K., Cs\'ak, B. et al., 2001, in preparation

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