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\input ibvs2.sty

\begin{document}

\IBVShead{4875}{5 April 2000}

\IBVStitle{New Field Variable Stars I}


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

\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}

\SIMBADobj{GSC 1170-0969}
\SIMBADobj{USNO-A2.0 0975-21294458}
\SIMBADobj{USNO-A2.0 1125-00465282}
\SIMBADobj{USNO-A2.0 1125-04132575}
\SIMBADobj{USNO-A2.0 0975-01669094}
\SIMBADobj{USNO-A2.0 0975-01021894}
\SIMBADobj{USNO-A2.0 0975-01289581}
\SIMBADobj{USNO-A2.0 1275-03337668}
\SIMBADobj{USNO-A2.0 1125-04142724}
\SIMBADobj{USNO-A2.0 0975-01671424}
\SIMBADobj{USNO-A2.0 1275-03360781}


\IBVStyp{ EW, EA, DSCT, RRab }
\IBVSkey{CCD photometry}
\IBVSabs{We report the discovery of eleven new field variable stars based on}
\IBVSabs{CCD observations carried out between 1998 April and 2000 January. 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

In the course of photometric and astrometric observations of selected
minor planets, we obtained 4415 individual CCD frames at the Konkoly
Observatory between April 1998 and January 2000 (S\'arneczky et al.\
1999, Kiss et al.\ 1999, Szab\'o et al.\ 2000). In order to extract as
much information as possible, we have surveyed this large amount of
data to identify known or new variable stars captured on those frames
which were obtained as time-series CCD photometry of certain asteroids.
As the typical observations covered 4-6 hours per night, we could
only find short-period variable stars.

The observations were carried out with the 60/90/180-cm Schmidt
telescope at the Piszk\'estet\H{o} Mountain Station of the Konkoly
Observatory.  The detector was a Photometrics AT200 CCD camera
($1536\times1024$ pixels, KAF-1600 chip with UV-coating). The field of
view was $29\arcm\times18\arcm$. The observations were mostly
unfiltered, but in several cases we used the Cousins $R_C$ filter.

The photometric reductions were done with the {\it ROMAFOT} package of
ESO-MIDAS version 98NOVpl2.1. We have examined time-series observations
that covered at least 90 minutes. For constructing light curves we used
a multi-object multi-frame analysing software developed by Balog et al.\
(2000). This software, called APPLE, determines interactively the
sub-pixel size shifts of the frames caused by the guiding errors of the
telescope. Differential instrumental magnitudes were determined
relative to an average value calculated from many (typically 10-20)
stars. The resulting light curves were checked interactively by
plotting them on the computer screen. The photometric accuracy is
between 0.01--0.05 mag, depending on the target brightness.

We have found seventeen variable stars on the examined CCD frames.  The
SIMBAD database was used to identify them with previously known
variables, but all of them turned out to be new discoveries. Six
variables were observed in February, 2000 with an objective prism at
the Konkoly Observatory in order to determine approximate spectral
types.  We present light curves for the other eleven variables in this
paper (Figs.~1,~2), while the remaining six stars together with their
spectra will be published in a subsequent paper. The presented
observational data are available upon request from the first author.

\IBVSfig{17cm}{4875-f1.eps}{Light curves of 6 new variable stars}

\IBVSfig{17cm}{4875-f2.eps}{Light curves of 5 new variable stars}

\vskip-22pt
Basic data (identifications, celestial coordinates and magnitudes) of
the new variables are summarized in Table~1.  The sparse phase
coverage did not allow reliable classification of the variable stars,
therefore, we give only a rough estimate of the type of variability
based on the light curve shapes and USNO-A2.0 colours. Further
multicolour photometry is needed to clarify the real nature of these
new variables.

\begin{table*}
\begin{center}
\caption{Basic data of the new variables. The coordinates,
red and blue magnitudes have been taken from USNO-A2.0}
\vskip2pt
\begin{tabular} {lccccl}
\hline
Variable & R.A. (2000) & Dec. (2000) & Red mag. & Blue mag. & Type\\
\hline
V01 & 01\hr 23\mm 02\fsec75 & +25\deg 37\arcm 12\farcs90 & 16.3 & 17.0 & EW\\
V02 & 04\hr 29\mm 31\fsec58 & +39\deg 52\arcm 47\farcs45 & 15.7 & 16.2 & --\\
V03 & 04\hr 30\mm 35\fsec11 & +39\deg 45\arcm 44\farcs51 & 17.0 & 18.2 & EW\\
V04 & 04\hr 31\mm 16\fsec85 & +13\deg 06\arcm 41\farcs83 & 17.0 & 18.1 & --\\
V05 & 05\hr 02\mm 00\fsec46 & +10\deg 37\arcm 23\farcs31 & 16.2 & 17.1 & --\\
V06 & 05\hr 31\mm 03\fsec25 & +10\deg 28\arcm 43\farcs57 & 15.2 & 17.6 & -- \\
V07 & 05\hr 31\mm 12\fsec78 & +10\deg 27\arcm 42\farcs99 & 16.7 & 17.4 & EW\\
V08 & 06\hr 32\mm 27\fsec44 & +27\deg 17\arcm 04\farcs79 & 14.7 & 15.2 & EA \\
V09 & 06\hr 32\mm 49\fsec06 & +27\deg 20\arcm 09\farcs16 & 16.0 & 16.4 & -- \\
V10 & 23\hr 29\mm 24\fsec67 & +10\deg 01\arcm 17\farcs08 & 15.6 & 15.6 & RRab\\
V11 & 23\hr 47\mm 39\fsec84 & +09\deg 20\arcm 29\farcs93 & 15.1 & 16.1 & EW\\
\hline
\end{tabular}
\end{center}
\end{table*}

This work has been supported by Hungarian OTKA Grant \#F032258,
Pro Renovanda Cultura Hungariae Foundation Grant DT 1999 \'apr./36.
and Szeged Observatory Foundation. The warm hospitality of the staff
of the Konkoly Observatory and their provision of telescope time
is gratefully acknowledged. We used the SIMBAD database,
operated at CDS, Strasbourg, France.

\references

Balog, Z., Vink\'o, J., Delgado, A.J., Alfaro, E.J., F\H{u}r\'esz, G.,
Kasz\'as, G., Moitinho, A., 2000, {\it MNRAS}, in preparation

Kiss, L.L., Szab\'o, Gy., S\'arneczky, K., 1999, {\it A\&AS}, {\bf 140}, 21

S\'arneczky, K., Szab\'o, Gy., Kiss, L.L., 1999, {\it A\&AS}, {\bf 137}, 363

Szab\'o, Gy., S\'arneczky, K., Kiss, L.L., Szil\'adi, K., 2000,
{\it A\&AS}, in preparation

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