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\input ibvs2.sty

\begin{document}
\IBVShead{4930}{26 July 2000}

\IBVStitle{GSC 4847\_1513 (FASTT 448) --- a New Eclipsing Variable}

\IBVSauth{Hager, Timothy$^1$; Guilbault, Peter~$^2$}

\IBVSinst{Western Connecticut State University, 181 White Street,
Danbury, CT 06810, USA\\ \indent e-mail: thager@pcnet.com}

\IBVSinst{P.O. Box 287, Chepachet, RI 02814, USA, e-mail: pete1199@aol.com}

\SIMBADobj{GSC 4847-1513}
\IBVStyp{ EA }

\begintext

GSC 4847\_1513 = FASTT 448 was first reported as a possible
variable by Henden and Stone (1998) in their table of suspected
variable stars discovered during the FASTT survey.  They noted
that the star had an observation 1.37 magnitudes below the mean of
all observations. This suggested to the authors that the star
might be an eclipsing binary and we began a program to determine
the nature of the variability using photographic, visual and CCD
observations.

Hager examined 230 patrol plates from the Harvard plate stacks
covering the periods 1929--1951 and 1968--1989 and found five
minima.  Guilbault initiated random visual observations of the
star using a 0.32 meter reflector to try to find the period.
Those observations permitted a rough determination of the period
and additional minima could be predicted and confirmed by
Guilbault's observations.

CCD observations commenced in 1999 with the goal of refining the 
period and the shape of the lightcurve. Those observations were 
made with the 0.51 meter Ritchey-Chretien reflector of the Western 
Connecticut State University (WCSU) Observatory and an ISI Systems 
CCD800 CCD camera using a $V$ filter. Additional minima were 
observed and the times of minimum found by all methods of 
observation are listed in Table 1. Both the visual and the CCD 
times of minimum were determined using a computer program based on 
the Kwee--Van Woerden (1956) method. 

All minima were fitted into a least squares solution with the CCD 
minima weighted as 10 and the visual and photographic minima 
weighted as 1. From that analysis we extracted the best period and 
combined it with the most accurate time of minimum to derive the 
following elements: 

$$ \begin{array}{r@{}r@{}l} {\rm Min.~I = HJD~} 2451621.55863 & {}
+ 1\fday0797024 & {} \times E.\\
                      \pm 0.00006 &  \pm 0.0000001 \\
\end{array} $$

The phased $V$ lightcurve in the instrumental system is shown in
Figure 1. Each point contains an error bar showing the estimated 
internal photometric error of each observation. The curve shows 
that the star fades from a maximum of $11\fmm86\pm0.01$ to 
$13\fmm77\pm0.04$ at primary minimum. A secondary eclipse 
with a depth of $0\fmm14\pm0.01$ occurs at phase 0.50. Both 
eclipses are partial and their duration is about 0.2~$P$. 

\newpage

\begin{center}
{\normalsize Table 1. Times of minimum, GSC 4847\_1513 (FASTT 448)}
\vskip2mm
\begin{tabular}{lrrl}
\hline
HJD 2400000\,+   &   Epoch&       $O-C$  &      Observer\\
\hline
25301.636&  $-$24377     &  $-$0.017        &     Harvard ptg\\
25314.622&  $-$25365     &  $+$0.012        &     Harvard ptg\\
25954.863&  $-$23772     &  $-$0.010        &     Harvard ptg\\
26059.612&  $-$23675     &  $+$0.008        &     Harvard ptg\\
27193.303&  $-$22625     &  $+$0.011        &     Harvard ptg\\
51255.5346(4)& $-$339       &  $-$0.005        &     Guilbault vis\\
51490.9191(2)& $-$120       &  $+$0.004        &     Guilbault vis\\
51502.7906(4)& $-$110       &  $-$0.001        &     Guilbault vis\\
51502.7909(4)& $-$110    &     0.000        &     Hager ccd \\
51555.6977(2)& $-$61     &  $+$0.001        &     Hager ccd \\
51621.55863(6)& 0        &     0.000        &     Hager ccd\\
\hline
\end{tabular}
\end{center}

\IBVSfig{10cm}{4930-f1.ps}{Phased lightcurve --- $V$ Filter}

The comparison and check stars are listed in Table 2. The $V$
magnitude and $V-I$ color index of GSC 4847\_1694 was taken from 
the {\it tenxcat} catalog produced by the TASS group (Richmond 
{\it et al}.\ 2000). The $V$ magnitude and color indices for GSC 
4847\_1605 are from the average of two nights of all sky 
photometry using observations of Landolt standards (Landolt, 1992) 
in March 1998 with the Lowell 31 inch telescope of the National 
Undergraduate Research Observatory (NURO) in Flagstaff, Arizona. 

\newpage
\begin{center}
{\normalsize 
Table 2. Comparison Stars}
\vskip2mm
\begin{tabular}{@{}lccccc@{}}
\hline &  Star    &    $V$ & $B-V$ & $V-R$ & $V-I$\\
\hline
Comp. & GSC 4847\_1694 &11.565${}\pm{}$0.065 & & &1.331${}\pm{}$0.165\\
Check & GSC 4847\_1605 &14.182${}\pm{}$0.044 &0.631${}\pm{}$0.038 &0.362${}\pm{}$0.060 &0.673${}\pm{}$0.060\\
\hline
\end{tabular}
\end{center}

We wish to thank Dr.~Martha Hazen, curator of astronomical photographs
at Harvard College Observatory, for use of the Harvard Patrol Plates.
We are also grateful to Dr.~Doug Welch and Dr.~Chris Lloyd for their
help in confirming our period. Hager's travel to NURO was made possible
by a grant from Western Connecticut State University and he also wishes
to thank his advisors Dr.~Dennis Dawson and Dr.~Phillip Lu for their
valuable help.

\IBVSedata{4930-t3.txt}

\references

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

Kwee, K. K., and Van Woerden, H., 1956, {\it BAN}, {\bf 12}, No.\,464, 327

Landolt, A. U., 1992, {\it AJ}, {\bf 104}, 340 

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

\endreferences

\end{document}

