\documentstyle[twoside,epsf]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{4927}{21 July 2000}

\IBVStitle{The \boldmath{$\delta$} Scuti Star QS Geminorum}

\IBVSauth{Hintz, E.G.; Carroll, D.D.; Fugal, J.P.; Hale, D.T.; Ahlstrom, P.F.}

\IBVSinsto{Brigham Young University, Dept.\ of Physics \&
Astronomy, Provo, Utah, 84602, USA \\ \indent e-mail: doctor@tardis.byu.edu}

\SIMBADobjAlias{QS Gem}{SAO 78728} %{HD 263446}{HIP 32459}

\begintext

QS Geminorum ($\alpha_{2000} = 06\hr46\mm28\fsec6$, $\delta_{2000}
=+20\deg50\arcm37\farcs1$, HIP 32459, HD 263446, GSC 01342-00231)
was found to be a variable star by the HIPPARCOS satellite. The
Variability Annex of the HIPPARCOS Catalogue (ESA 1997) reports QS
Gem to have a period of 0.134613 d with $H_{p}$ magnitudes ranging
between 8.874 to 8.973.  The spectral type is listed as A3 and the
star is classified as a $\delta$ Scuti.

As part of our ongoing $\delta$ Scuti star program, and as part of
our Phscs 329 Observational Astronomy class, we selected stars
from the Variability Annex of the HIPPARCOS Catalogue that showed
$\delta$ Scuti type characteristics. During winter semester of
both 1999 and 2000, QS Gem was observed by groups of Phscs 329
students. Observations were made with the 0.4-m David Derrick
Telescope of the Orson Pratt Observatory at Brigham Young
University (Hereafter DDT). Data were obtained with a Pictor 416XT
CCD mounted at the newtonian focus of the telescope. This gave a
plate scale of 0.93 arcsec/pixel. Observations were made through a
standard Johnson $V$ filter modeled after Bessell (1990). A total
of nine nights of data were obtained between 23 February 1999 and
12 April 2000. The CCD field for the DDT is shown in Fig.~1 with
QS Gem and the comparison stars labeled.

All frames were reduced using standard IRAF functions. Apparent
magnitudes were determined using comparison stars 4 and 5 as shown in
Fig.~1.  Star 4 is identified as HD 263542 (GSC 01342-01109, $V =
9.72$) and star 5 is identified as HD 48995 (GSC 01342-00517, $V =
8.61$). From this we found an average magnitude for QS Gem of $V =
8.85$. The two other comparison stars labeled in Fig.~1 were considered
too faint to use in the final analysis.  However, star 3 (GSC
01342-01261) was found to be an eclipsing variable and is detailed in a
separate paper (Carroll \& Hintz, 2000).

From the light curves, ten times of maximum light were determined.
These times are given in Table~1. Using linear regression
techniques we determined an ephemeris for QS Gem as given in
Eq.~1. The period determined is similar to the value found by
HIPPARCOS although significantly shorter.
\begin{equation}
{\rm HJD_{max}} = 2451222.8693 + 0.131955 (\pm 0.000002) \times E.
\end{equation}

In Fig.~2 we show a light curve for QS Gem from HJD 2451444 and in
Fig.~3 we show a light curve from HJD 2451626.  Clearly the
amplitude of QS Gem is not constant. The amplitude varies from
0.08 to 0.20. Due to this variable amplitude we chose to examine
the data with the frequency search program Period98. From this
analysis only $f_{1}$ and 2$f_{1}$ were found to be reliable
frequencies as shown in Table~2. The value for $f_{1}$ is in
excellent agreement with the period found by linear regression. A
larger data set is called for to find the true frequency spectra.

QS Gem appears to be a normal low-amplitude $\delta$ Scuti
variable with a complex light curve. Since this star is relatively
bright with a moderate amplitude it would be an ideal star for an
international campaign or for one of the small variability
satellites currently under development.


\IBVSfig{7cm}{4927-f1.eps}{CCD field of QS Gem with comparison
stars labeled. The field of view is $8\arcm\times12\arcm$.}

\IBVSfig{8cm}{4927-f2.eps}{Light Curve of QS Geminorum from HJD
2451444}

\IBVSfig{8cm}{4927-f3.eps}{Light Curve of QS Geminorum from HJD
2451626}

\begin{table}
\caption{New Times of Maximum Light for QS Geminorum}
\begin{center}
\begin{tabular}{ccr}
\hline HJD & \lower6pt\hbox{Cycle} & \lower6pt\hbox{$O-C$}\\ [-3pt] 2451000.0+ & &\\ \hline
    222.8692   & 0      & $-$0.0001\\
    444.9492   & 1683   & $-$0.0004\\
    463.9563   & 1827   &  0.0052\\
    489.8115   & 2023   & $-$0.0028\\
    489.9398   & 2024   & $-$0.0064\\
    496.8071   & 2076   & $-$0.0008\\
    597.7505   & 2841   & $-$0.0030\\
    626.6504   & 3060   & $-$0.0012\\
    632.5904   & 3105   &  0.0008\\
    632.7199   & 3106   & -0.0016\\
\hline
\end{tabular}
\end{center}

\bigskip

\caption{Frequencies Present in Light Curve of QS Geminorum}
\begin{center}
\begin{tabular}{crcc}
\hline  & Frequency & \lower6pt\hbox{Amplitude} & \lower6pt\hbox{Phase} \\[-3pt]
        & (cycle/day) & & \\ \hline
        $f_{1}$ & 7.5782 & 0.054 & 0.614 \\
        $2f_{1}$ & 15.1564 & 0.004 & 0.445\\
\hline
\end{tabular}
\end{center}
\end{table}

\references

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

Carroll, D. D., Hintz, E. G., 2000, {\it IBVS}, No.\ 4928

ESA, 1997, The HIPPARCOS Catalogue, ESA, SP-1200

\end{document}
