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\IBVShead{5401}{8 April 2003}

\IBVStitle{New and Suspected Mira Variables on Stardial Images}

\IBVSauth{Wils, P.}

\IBVSinsto{Vereniging Voor Sterrenkunde, Belgium; email: Patrick.Wils@cronos.be}

\SIMBADobj{CSS 401}
\SIMBADobj{StM 138} % = NSV 18400 
\IBVSobj{NSV 4082}
\IBVSobj{NSV 7549}
\IBVSobj{NSV 11266}
\IBVSkey{Mira stars - photometry}
\IBVSabs{Three new Mira variables and six previously suspected variables,}
\IBVSabs{ which are also Mira variables, were observed on Stardial images.}

\begintext

The Stardial system consists of an autonomous drift-scan CCD camera, run by
the University of Illinois at Urbana-Champaign (McCullough and Thakkar, 1997). 
One image per day is taken of each 8$\times$5 degree area of sky centered at a declination of $-4\deg$, 
when the region is near the meridian.
The system is therefore ideally suited to follow long period variables (see e.g. Bedient, 2001).
Images are publicly available at {\tt http://www.astro.uiuc.edu/stardial/}. 

This paper reports on observations of 9 Mira stars, six of which were suspected variables 
already before, four of them catalogued in the NSV and NSVS.  
The three other Mira variables are new. \\

The available images, spanning the years 1999 to the end of 2002 or early 2003, of a particular region were treated as follows.  
First, photometry was done using the XVista programs 
written by Michael Richmond\footnote{\tt http://spiff.rit.edu/tass/pipeline/pipeline.html}. His match programs
were then used to transform image coordinates to sky coordinates by comparing star positions from
the Tycho catalogue. 
The programs have at this time essentially produced lists of sky coordinates with raw magnitudes.
Then the technique of ensemble photometry (Honeycutt, 1992) was applied to produce homogeneous
magnitudes for all the images of the region.  Since a non-standard red broadband filter is used by Stardial, 
the magnitudes obtained
cannot really be compared to magnitudes obtained with standard filters.  Therefore no attempt was 
made to transform the magnitudes to a standard system.  Only a simple
translation was applied to fix the zero point of the magnitude scale, in such a way that
for Tycho stars with $-0.1 < B-V < 0.1$, Tycho $V$ magnitudes and Stardial magnitudes are aligned as 
much as possible.  Error bars on the magnitudes are a combination of the photon statistics errors
and the errors on the ensemble solution for a particular night. \\

In the data set, long period variables were then searched for by using 
the Mean Square Successive Difference
technique (von Neumann et al., 1941).  This method assumes that the deviation between subsequent data points
is small compared to the total variation for a time series showing a trend.  In this way a number
of long period variables could be discovered and known and suspected variables recovered.  
This paper reports on nine Mira variable stars, presented in Table~1.  
The first column gives the USNO-B1.0 identification of the objects, except for two cases where exact
identification proved impossible (note that the Stardial pixel size
is 36\arcs, which is not accurate enough for correct identification in crowded fields).  
The following columns contain the IRAS identification when available, 
the Julian Date of an observed maximum, the period in days, the amplitude in Stardial magnitudes,
and remarks and other identifications.
The periods of these stars have been determined
using the PDM technique (Stellingwerf, 1978).  
Light curves are presented in Figures~1 and 2. \\

\begin{center}
{\normalsize {\bf Table 1}. Data on nine Mira variables} \vskip2mm
\begin{tabular}{ccclrl}
\hline
USNO-B1.0 & IRAS & JD Max & Period & Amplitude & Remark \\
          &      &        & [d]    &  [m]      &        \\
\hline
0874-0221669 & 07454-0228 & 2451491 & 293 & 2.0 & 1 \\
0867-0188840 & 08239-0307 & 2451538 & 323 & 2.0 & 2 \\
0824-0264160 & -- & 2451950 & 364 & 2.0 & 3\phantom{.0} \\
0834-0296187 & 16112-0624 & 2451350 & 232? & $>3$\phantom{.0} & 4 \\
0858-0334726 & 17440-0407 & 2451310 & 349 & $>2.0$ & 5 \\
? & 18108-0503 & 2452491 & 340 & 1.5 &  \\
? & 18413-0641 & 2452516 & 260: & $>3$\phantom{.0} & 6 \\
0847-0554572 & 19456-0522 & 2452470 & 290: & 2.5 & 7 \\
0839-0602533 & 19582-0613 & 2452540 & 115? & $>1.5$ & \\
\hline
\end{tabular}
{\normalsize
\begin{tabular}{ll}
1 & GSC 04836-01821 = CSS 401 (Stephenson 1984) \\
  & Magnitude in maximum varies by at least 0.5 mag \\
2 & NSV 4082 = GSC 04853-01862 \\
3 & NSV 18400 = MSX5C G252.1851+40.6061 = StM 138 (Stephenson 1986) \\
4 & NSV 7549 = BV 1112, amplitude from USNO-B1.0 B1 and R1 \\
5 & TASS J174643.5-040811 (Richmond et al. 2000) \\
6 & NSV 11266 = BV 1635 \\
7 & GSC 05154-01249, close companion 5\arcs E \\
\end{tabular}
}
\end{center}

\IBVSfig{22.5cm}{5401-f1.eps}{Light curves of five Mira stars.}
%%\IBVSfigKey{5401-f1.eps}{IRAS 07454-0228 ; NSV 4082 ; NSV 18400 ; NSV 7549 ; IRAS 17440-0407}{light curve}

\IBVSfig{17.5cm}{5401-f2.eps}{Light curves of the remaining four Mira stars.}
%%\IBVSfigKey{5401-f2.eps}{IRAS 18108-0503 ; NSV 11266 ; IRAS 19456-0522 ; IRAS 19582-0613}{light curve}

{\bf Acknowledgements:} 
This research has made use of the USNOFS Image and Catalogue Archive operated by the 
United States Naval Observatory, Flagstaff Station \\
{\tt (http://www.nofs.navy.mil/data/fchpix/)}, and of the SIMBAD and 
VizieR 
database operated at the {\it Centre de Donn\'ees Astronomiques (Strasbourg)} in France.
The author would like to thank Michael Richmond for providing the XVista and match programs, 
and John Greaves and Paul Van Cauteren for helpful discussions.


\references

Bedient, J. R., 2001, {\it IBVS}, No.\,5164

Honeycutt, R. K., 1992, {\it PASP}, {\bf 104}, 435 

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

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

Stephenson, C. B., 1984, {\it Publ. Warner \& Swasey Obs.}, {\bf 3}, 1

Stephenson, C. B., 1986, {\it ApJ}, {\bf 301}, 927

von Neumann, J., Kent, R. H., Bellinson, H. R., Hart, B. I., 1941, {\it Ann. Math. Stat.}, {\bf 12}, 153

\endreferences

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