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\IBVShead{5425}{11 June 2003}

\IBVStitle{Eclipsing Binaries Discovered on Stardial Images}

\IBVSauth{Wils, P.$^1$; Dvorak, S. W.$^2$}
\IBVSinst{Vereniging Voor Sterrenkunde, Belgium; e-mail: patrick.wils@cronos.be}
\IBVSinst{Rolling Hills Observatory, Clermont, FL USA; e-mail: sdvorak@rollinghillsobs.org}

\SIMBADobj{BD-2 2221}
\SIMBADobj{HD 296761}
\SIMBADobj{HD 51697}
\SIMBADobj{HD 67093}
\SIMBADobj{BD-4 2739}
\SIMBADobj{GSC 04904-01087}
\SIMBADobj{HD 89027}
\SIMBADobj{BD-3 3419}
\SIMBADobj{BD-0 2900}
\SIMBADobj{HD 162905}
\IBVSkey{Eclipsing binary stars - photometry}
\IBVSabs{Details are presented on ten new eclipsing binaries discovered}
\IBVSabs{on Stardial images.}

\begintext

The Stardial system, run by
the University of Illinois at Urbana-Champaigne (\hbox{McCullough} and Thakkar, 1997), has been
found useful for the discovery and follow-up of long period variables.  
This paper however reports on the discovery of ten short period eclipsing binaries
on the images from this system.  

The procedure used to reduce the images to star and magnitude lists
was described by Wils (2003).  For some stars 250 data points were obtained.  
For the brightest stars (mag. $<$ 10), an internal accuracy of 0.03 mag could be obtained,
depending on the quality of the night.  
For stars with more than 100 observations, the PDM technique (Stellingwerf, 1978) was used
to search for periodic variability.
  
Since Stardial images are always taken when
the region crosses the meridian, strong aliasing is present, and in fact it is impossible
to distinguish between the genuine period and its aliases. 
The stars so discovered were then verified using the ASAS-3 archive (Pojmanski, 2002), 
which aided in establishing the correct period.  Some of the stars were also followed for one
or more nights at Rolling Hills Observatory
(see Dvorak 2003 for a description of the instruments used). 
For three of the stars, V and I data were also available from the TASS Mk III survey
(Richmond et al., 2000).  For four others limited unpublished data from the TASS Mk IV data (Droege, 2003)
provided further confirmation of the variability and the period.

The new eclipsing binaries are presented in Table~1.  
The first column gives the identification of the objects (HD, BD or GSC number).  
The following columns contain the type of variability, the epoch of minimum, 
period (in days) and
the V range derived from the ASAS-3 database.

Phased light curves of these stars are presented in figures 1 and 2, with V  
data from the ASAS (open squares) and TASS (filled circles) surveys, 
and from Rolling Hills Observatory (crosses).
The Stardial data (dashes) are taken through a non-standard red filter, 
and their zero-point was shifted
to be in agreement with the available V data (which means that the amplitude may differ).

\begin{table}[!ht]
\begin{center}
{\normalsize Table 1. Data on the new eclipsing binaries} \vskip2mm
\begin{tabular}{cccccccc}
\hline
Identification & Type & HJD Min & Period & Max & Min I & Min II & Remarks \\
 & & $-$2450000 & days & V & V & V & \\
\hline
HD 51697 & EA & 2684.68 & 2.51640 & 9.2 & 9.4 & 9.35 & 1\\
HD 296761 & EW & 2667.755 & 0.35843 & 9.9 & 10.6 & 10.5 & 2,3 \\
BD $-$2 2221 & EW & 2681.731 & 0.63772 & 8.9 & 9.4 & 9.3 & 2,4 \\
HD 67093 & EA & 2252.86 & 2.16780 & 8.8 & 9.2 & $-$ & 5 \\
BD $-$4 2739 & EA & 2705.73 & 0.71958 & 9.9 & 10.5 & $-$ & 5,6 \\
GSC 04904-01087 & EB & 2722.77 & 1.05917 & 9.8 & 10.2 & 10.0 & \\
HD 89027 & EW & 2314.79 & 0.54011 & 9.3 & 9.55 & 9.5 & \\
BD $-$3 3419 & EW & 1661.69 & 0.31125 & 9.6 & 10.1 & 10.0 & 7 \\
BD $-$0 2900 & EB & 0938.73 & 0.58040 & 10.1 & 10.6 & 10.5 & \\
HD 162905 & EW & 2369.95 & 0.42651 & 9.2 & 9.4 & 9.4 & 8 \\
\hline
\end{tabular}
\end{center}
1  Visual pair (mag. 9.8 and 10.4) with 3\arcs\ separation (not separated on Stardial images)\\
2  Minimum measured at Rolling Hills Observatory \\
3  = 1RXS-F J071507.4-044437 \\
4  Eclipse is probably total \\
5  No secondary minimum detected, period may be double the value given \\
6  = 1RXS J0950391.1-053029 \\
7  = 1RXS J131032.4-040934 \\
8  According to literature the spectral type is K0, so the given period may be too long \\
\end{table}

\IBVSfig{8cm}{5425-f1.eps}{Phased light curves of six of the new eclipsing binaries.}
%%\IBVSfigKey{5425-f1.eps}{HD 51697 ;  HD 296761 ;  BD -2 2221 ;  HD 67093 ;  BD -4 2739 ;  GSC 04904-01087}{light curve}

\IBVSfig{8cm}{5425-f2.eps}{Phased light curves of the remaining four eclipsing binaries.}
%%\IBVSfigKey{5425-f2.eps}{HD 89027 ;  BD -3 3419 ;  BD -0 2900 ;  HD 162905}{light curve}

{\bf Acknowledgements:} 
This research has made use of the SIMBAD and VizieR 
databa\-ses operated at the {\it Centre de Donn\'ees Astronomiques (Strasbourg)} in France.
The authors would like to thank Michael Richmond for providing the XVista and match programs
to reduce the Stardial images.
The Stardial, TASS and ASAS teams are acknowledged for providing public access to their archives.


\references

Droege, T.F., 2003, {\it private communication}

Dvorak, S.W., 2003, {\it IBVS}, No.\,5378

McCullough, P., Thakkar, U., 1997, {\it PASP}, {\bf 109}, 1264 

Pojmanski, G., 2002, {\it Acta Astronomica}, {\bf 52}, 397

Richmond, M.W., Droege, T.F., Gombert, G., Gutzwiller, M., Henden, A.A., Albertson, C., 
  Beser, N., Molhant, N., Johnson, H., 2000, {\it PASP}, {\bf 112}, 397 

Stellingwerf, R.F., 1978, {\it ApJ}, {\bf 224}, 953

Wils, P., 2003, {\it IBVS}, No.\,5401

\endreferences

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%From: IBVS 5725
\IBVSerratum{5425}

Geert Hoogeveen reported the following error:

\begin{table}[h!]
\begin{tabular}{c l l l}
\hline
IBVS No. & item & printed & correct \\
\hline
5425 & identifier (BD -4\deg 2739) & 1RXS J0950391.1-053029 & 1RXS J095039.1-053029 \\
\hline
\end{tabular}
\end{table}

\end{document}

