\documentstyle[twoside, epsfig]{article}

\input ibvs2.sty

\begin{document}
\IBVShead{5891}{29 June 2009}

\IBVStitle{A Period Analysis of the {\large {\boldmath $\delta$}} Scuti Variable GSC 03973-01698}

\IBVSauth{HINTZ, E. G.$^1$; BUGNO, J. L.$^1$; JONER, M. D.$^1$}

\IBVSinst{Brigham Young University, Dept. of Physics and Astronomy, Provo, UT 84602, USA}

\IBVSinsto{e-mail: doctor@tardis.byu.edu; batgirl3220@aim.com; jonerm@forty-two.byu.edu}

\SIMBADobj{GSC 3973-1698}
\IBVStyp{ DSCT }
\IBVSkey{CCD Photometry}

\begintext

\vspace*{-1cm}

As part of an undergraduate summer research program, we examined the High Mass \hbox{X-ray} Binary system (HMXB) 4U
2206+543. On a finder chart for this system provided by the American Association of Variable Star Observers
(AAVSO), they identify one of the comparison stars, GSC 3973-1698, as a $\delta$ Scuti variable with a period of
0.06 d. GSC 3973-1698 was present in our field of view on all nights of observations during our campaign;
therefore we present an analysis of its light curves.

Our\,data consists of 20\,nights of photometric\,observations on the field near 4U\,2206+543. A finder chart is
given in Fig. 1 which includes the $\delta$ Scuti, 4U 2206+543, and the five comparison stars. A total of 19
nights were obtained with the 0.41-m David Derrick Telescope of the Orson Pratt Observatory (OPO), which is
located in the center of the BYU~campus. Observations were made with an unbinned ST-10XME CCD. Six nights of
data were obtained with the 0.31-m telescope of the BYU West Mountain Observatory (WMO) using another ST-10XME
CCD which was binned $2\times2$. These six nights overlapped with six of the nights secured on the OPO system. Finally
we obtained two nights of data with the 0.51-m telescope at the BYU West Mountain Observatory using a SBIG
STL-1001 CCD. One of these nights was in common with the OPO data, while the other provided our 20th night of
data.  All observations were made with a standard $V$ filter (Bessell, 1990) and yielded an error per observation
on the order of 0.004 mag. The observational dara are available on the IBVS
website as {\tt 5891-t3.txt}.

\IBVSedata{5891-t3.txt} 
\IBVSdataKey{5891-t3.txt}{GSC 3973-1698}{photometry}

Differential magnitudes were determined relative to an ensemble of four comparison stars (Star 2 was not used
since it is an eclipsing binary system). Apparent magnitudes were determined using GSC 3973-1066 (Star 3, $V =
11.946\pm0.013$) and GSC 3973-1906 (Star 4, $V = 11.837\pm0.008$). The magnitudes given were taken from the
calibration of the field obtained by A. Henden\IBVSfm.  In Fig. 2 we show simultaneous light curves from data taken at both observatory facilities.
The light curves for all nights are presented in Fig. 3. The denser portions of the light curves indicate when
simultaneous data were obtained.

\IBVSfoot{\tt http://homepage.usask.ca/\~{}ges125/Astronomy/LPH128\_aavso.pdf
ftp://ftp.aavso.org/public/calib/3a2206.dat}

Both a Fourier analysis using the {\tt Period04} (Lenz \& Breger, 2005) program and a traditional time of maximum light
argument were utilized to determine a period for GSC~3973-1698. We note that a time of maximum light analysis is
not always reliable for low amplitude, multiperiodic stars.  In Table 1 we present the 19 times of maximum light
found for GSC 3973-1698. From this we find an ephemeris of
\begin{equation}
{\rm HJD } =  2454630.942(\pm0.003) + 0.06501(\pm 0.00001) {\rm E}.
\end{equation}

From the Fourier analysis we find four frequencies that have detection signal-to-noise values higher than four
(Breger et al., 1993, 2007).  The four main frequencies are reported in Table 2 and the power spectrum is shown
in Fig. 4.  Overlaid in Fig. 3 we show the four-frequency model generated from our Fourier solution. From the
final panel in Fig.~4, and the fit in Fig. 3, it is clear that additional frequencies exist in GSC 3973-1698,
but their detection level is too low from this data set. Our primary frequency of 15.3843~cycles/day corresponds
to a period of 0.06500 days and is consistent with the value and errors found in Equation 1.

GSC\,3973-1698 is a typical low amplitude $\delta$\,Scuti variable with a complex frequency content.\,The thing
that makes this star so interesting is that it is in the field of 4U\,2206+543, which means that a great deal of
data will be obtained in many filters as observations are taken of the HMXB.

\textbf{Acknowledgements} We would like to acknowledge the Brigham Young University Department of Physics and
Astronomy for their continued support.  We acknowledge a grant for the Theodore Dunham, Jr. Grant for Research
in Astronomy. We finally acknowledge NSF grant PHY-0552795.

\IBVSfig{6.8cm}{5891-f1.eps}{Finder chart for GSC 3973-1698 with 4U 2206+543 and comparison stars
marked. The field is 20' wide and 15' high with North being up and East to the left.}
\IBVSfigKey{5891-f1.eps}{GSC 3973-1698}{finding chart}
\vspace*{-1.6cm}
\IBVSfig{6cm}{5891-f2.eps}{Simultaneous light curves from the OPO (solid) and WMO (open) facilities.}
\IBVSfigKey{5891-f2.eps}{GSC 3973-1698}{light curve}

\IBVSfig{9cm}{5891-f3.eps}{All 20 nights of $V$ photometry are presented on the same magnitude and time scales. The data from WMO and OPO are plotted together.} 
\IBVSfigKey{5891-f3.eps}{GSC 3973-0812}{light curve}

\IBVSfig{21.50cm}{5891-f4.eps}{Power spectra of GSC 3973-1698.  The spectral window in the top panel is scaled to the same frequency range as the individual power spectra. } 
\IBVSfigKey{5891-f4.eps}{GSC 3973-0812}{periodogram}

\vspace*{-1cm}
\centerline{{\bf Table 1.} Times of Maximum Light for GSC 3973-1698} \vskip 2mm
\begin{center}
\begin{tabular}{rccccc}
\hline
Cycle   &  HJD  &  Cycle & HJD  & Cycle & HJD \\
\hline
0   &   2454630.9375  & 228 &   2454645.7687 & 398 &   2454656.8164\\
13  &   2454631.7871  & 229 &   2454645.8370 & 399 &   2454656.8795\\
14  &   2454631.8481  & 258 &   2454647.7103 & 551 &   2454666.7485\\
76  &   2454635.8808  & 259 &   2454647.7693 & 552 &   2454666.8103\\
77  &   2454635.9492  & 306 &   2454650.8319 & 752 &   2454679.8403\\
198 &   2454643.8204  & 322 &   2454651.8699 & \\
199 &   2454643.8853  & 383 &   2454655.8394 & \\
\hline
\end{tabular}
\end{center}

\bigskip

\centerline{{\bf Table 2.} Frequency Content of GSC 3973-1698} \vskip 2mm
\begin{center}
\begin{tabular}{lrcr}
\hline
    & \multicolumn{1}{c}{Frequency}   & Amplitude & \multicolumn{1}{c}{Detection} \\
ID  & \multicolumn{1}{c}{(cycles/day)}& (mag)     & \multicolumn{1}{c}{S/N}       \\
\hline
$f_{1}$  & 15.3843 & 0.010    & 12.5 \\
$f_{2}$  & 16.3310 & 0.006    & 7.3\\
$f_{3}$  & 13.4091 & 0.005    & 6.2\\
$f_{4}$  & 6.0763  & 0.004    & 5.0\\
 \hline
\end{tabular}
\end{center}

\references

Bessell, M., S., 1990, {\it PASP}, {\bf 102}, 1181

Breger, M et al., 1993, {\it A\&A}, {\bf 271}, 482

Breger, M., Rucinski, S. M. \& Reegen, P., 2007, {\it AJ}, {\bf 134}, 1994

Lenz, P. \& Breger, M., 2005, {\it Commun. Asteroseismol.}, {\bf 146}, 53

\endreferences

\end{document}
