\documentstyle[ibvs2, twoside, epsf, array]{article}

\begin{document}

\IBVShead{5697}{3 May 2006}

\IBVStitle{GSC 1419 0091, an Extreme Mass Ratio Contact Binary }

\IBVSauth{Samec, Ronald G.$^{1,2}$; Scott, Tyler D.$^1$; Branning, Jeremy S.$^1$; Faulkner, Danny R.$^{2,3}$; Hawkins, Nathan C.$^2$; Van Hamme, Walter$^4$}

\IBVSinst{Astronomy program, Department of Physics Bob Jones University, Greenville, SC 29614 USA}
\IBVSinst{Visiting Astronomer, Lowell Observatory, Flagstaff, AZ}
\IBVSinst{U of South Carolina, Lancaster, SC}
\IBVSinst{Florida International University, Miami, Fl}

\SIMBADobj{GSC 1419-0091}

\begintext

\vspace*{-1cm}

   As a part of our study of solar-type eclipsing binaries with extreme mass ratios (EMRB), we observed the variable 
GSC~1419 0091 [Brh V132, $\alpha(2000)$= 10\hr 11\mm 59\fsec15, $\delta(2000)$= +16\deg 52\arcm 30\farcs28].  
This binary was discovered by Bernhard (2003, 2004) and identified as GSC~1419 0091. An 
unfiltered CCD light curve taken by Frank (2005) shows that the variable is unmistakably a low 
amplitude short period totally eclipsing system.  That is the light curve character of an EMRB sometimes referred to as an
AW UMa-type star. He gave the ephemeris: 
\begin{equation}                   
  {\rm HJD\ Tmin\ I} = 2452754.4602 \pm 0.266727 {\rm d \times E}
\end{equation}                   


\IBVSedata{5697-t1.txt}
\IBVSdataKey{5697-t1.txt}{GSC 1419-0091}{photometry}

\IBVSfig{5.3cm}{5697-f1.eps}{}
\IBVSfigKey{5697-f1.eps}{GSC 1419-0091}{finding chart}

\IBVS2fig{7cm}{5697-f2.eps}{}{5697-f3.eps}{}
\IBVSfigKey{5697-f2.eps}{GSC 1419-0091}{light curve}
\IBVSfigKey{5697-f3.eps}{GSC 1419-0091}{light curve}

\vspace*{-1cm}

   Our $B,V,R_c,I_c$ light curves were taken with the Lowell 31 inch reflector in Flagstaff with the LN cooled 
CCD camera and a metachrome coated TEK 512 $\times$ 512 chip and standard $BVR_cI_c$ filters. The light curves were 
taken on 7, 11 and 12,  March 2005  by NCH , RGS, and DRF.  The individual observations included 59 $B$, 63 $V$, 59 $R$ 
and 59 in $I$.  The stars [GSC 1419 0805, $\alpha(2000)$= 10\hr 11\mm 51\fsec30, $\delta(2000)$= +16\deg 50\arcm 13\farcs1],
and [$\alpha(2000)$ = 10\hr 11\mm 58\fsec88, $\delta(2000)$= +16\deg 52\arcm 40\fsec1] were used as the comparison and check stars, 
respectively.  The delta magnitudes are given in electronic Table~1 available on the IBVS
website as {\tt 5697-t1.txt}. A finding chart of GSC~1419~0091~(V), the comparison star 
(C), and check star (K) is given in Figure 1.  The light curves are displayed
in Figure~2 and 3, as normalized flux  versus phase.


    Three precision mean epochs of minimum light were determined from eclipse timings in $B,V,R_c,I_c$ 
using parabola fits: ${\rm HJD\ Tmin\ I} = 2453437.8293\,{\rm d} \pm 0.0003, \\2453441.8291{\rm d} \pm0.0019$ and ${\rm HJD\ Tmin\ II} =
2453437.6973 \pm 0.0012$. Other times of minimum light were determined by H\"ubscher (2005) and by Frank 
(Bernhard 2003, 2004). We also took times of low light from Rotse observations to extend the observational
history for our period study.

    A linear fit to all available timings of minimum light gives:
\begin{equation}                   
{\rm HJD\ TMin\ I} = 2453437.8207\ (\pm 0.0024) + 0.2667249\ (\pm 0.0000007){\rm d \times E}
\end{equation}                   
A quadratic trend is apparent so we also calculated the following ephemeris:
\begin{eqnarray}                   
{\rm HJD\ TMin\ I} = 53437.82924\ (\pm 0.00079) + 0.26673640\ (\pm 000000059){\rm d \times E}  \\
+ 0.00000000153{\rm d \times E}^2\ (\pm 0.00000000007) \nonumber
\end{eqnarray}                   
    In addition, we used the Wilson code to calculate a linear ephemeris using our present observations for the 
purpose of phasing the light curves (van Hamme and Wilson 1998):
\begin{equation}                   
{\rm HJD Tmin I} = 2453437.82835\pm  0. 00029 + 0.266749 \pm 0.000010 {\rm d \times E}
\end{equation}                   
The $O-C$'s for the linear and quadratic fit are given in electronic Table~2
(available on the IBVS website as {\tt 5697-t2.txt}) and the plot
of $O-C$ residuals for Equation 2 and overlaid by a quadratic fit is given as
Figure 4. 

\IBVSedata{5697-t2.txt}
\IBVSdataKey{5697-t2.txt}{GSC 1419-0091}{}

    It is typical for W UMa binaries to have continuously decreasing or increasing periods. In the stage of shallow contact,
binaries may undergo thermal relaxation oscillations (TRO) so, theoretically, the period will alternately increase and decrease.  
(Cyclic changes can also result from stellar magnetic cycles or from a third body.) When binary components reach firm contact, after TRO cycles, 
the solar type binary will steadily lose angular momentum via stellar winds and its period will be characterized by a continuous 
decrease. We found from our light curve solution that the fill-out is still somewhat shallow so TRO may still be acting here. In that case,
and the period can be on the increase as suggested by the quadratic ephemeris. Further observations are needed to confirm the trend suggested 
by our preliminary period study.  

    Standard magnitudes were determined from observations of Landolt standard stars SA~106 700, PG 1323 086,
,PG 1323 086B, PG 1323 086C, and PG 1407-013 on March~7, 2005. They indicate the variable
is a 12th magnitude binary which varies from a \linebreak \hbox{$V=11.78\pm 0.03$} to $12.28\pm 0.07$. The comparison and check stars 
have a $V$ magnitude of $11.64\pm 0.08$ and $15.28\pm 0.08$, respectively. The color indices indicate that GSC~1419~091 is 
of late G to early K-type. The check is late F to early G while the comparison is late K to early M. Details are given in 
electronic Table~3, available on the IBVS website as {\tt 5697-t3.tex}.

\IBVSetable{5697-t3.tex}
\IBVSdataKey{5697-t3.tex}{GSC 1419-0091}{}

    We began by pre-modeling the binary in Binary Maker 3.0 (Bradstreet 2002) and then used Our results as starting values 
for the 5-color synthetic light curve solution in the newest 2004 Wilson Code.(Wilson \& Devinney 1971, Wilson 1990, 1994).

    Our solution indicates that GSC 1419 0091 is a short period AW UMa-type contact binary. The primary 
component is the more massive, slightly cooler star.  The primary component is over five times the mass of the secondary component
($m_2/m_1 = 0.19$) the Roche lobe fillout is 23\%. We would expect this to increase with time.  Other parameters 
include the temperatures, $T_1 = 5000 \pm 300$K (fixed, error from photometry)
and \linebreak $T_2 = 5014 \pm 3$K (formal error, so the actual error is still about $\pm 300$). The orbital inclination was $84\fdeg7 \pm 0\fdeg1$. The eclipses
are total, so we believe our solution is definitive. We note here that errors given in the Table  are formal errors.

    The observed O'Connell effect is evidence for magnetic spot activity; our model includes two weak but 
broad magnetic regions. Both of the magnetic regions were of high latitude which is indicative of strong magnetic activity.

    Our solution is given as electronic Table~4 (available on the IBVS website as \\{\tt 5697-t4.tex}) and the synthetic light curves are shown overlaying the phased, flux-normalized
data in Figure 3. Our geometrical representation of GSC~1419~0091 is given in Figure 5. 

\IBVSfig{10cm}{5697-f4.eps}{}
\IBVSfigKey{5697-f4.eps}{GSC 1419-0091}{O-C diagram}

\IBVSfig{5.2cm}{5697-f5.eps}{}
\IBVSfigKey{5697-f5.eps}{GSC 1419-0091}{}

    We wish to thank the National Undergraduate Research Observatory (NURO) and Lowell Observatory for their allocation 
of observing time, as well as NASA and the American Astronomical Society for their continued support of our undergraduate 
research programs through their small research grants.

\IBVSetable{5697-t4.tex}
\IBVSdataKey{5697-t4.tex}{GSC 1419-0091}{}


\references

Bernhard, K., 2003, {\it BAV Rundbrief}, {\bf 52}, 168

Bernhard, K., 2004, {\it BAVSM}, {\bf 168}, 1

Bradstreet, D. H., 2002, {\it AAS}, {\bf 201}, 7502

Frank, P., 2005, {\it IBVS}, 5599

H\"ubscher, J., 2005, {\it IBVS}, No. 5643

van Hamme, W.V., Wilson, R.E., 1998, {\it Bull. AAS}, {\bf 30}, 1402

Wilson, R. E., Devinney, E. J., 1971, {\it ApJ}, {\bf 166}, 605

Wilson, R. E., 1990, {\it ApJ}, {\bf 356}, 613

Wilson, R. E., 1994, {\it PASP}, {\bf 106}, 921

\endreferences

\end{document}
