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\input ibvs2.sty
 
\begin{document}
 
\IBVShead{5849}{22 August 2008}
 
\IBVStitle{The Cool Dwarf Interacting Eclipsing Binary, HH95-79}


\IBVSauth{Samec, Ronald G.$^{1,2}$; McKenzie, Rob$^{1,2}$; Hawkins, Nathan C.$^{1,2}$; Van Hamme, Walter$^4$; Faulkner, Danny R.$^{2,3}$}


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

\SIMBADobj{GSC 01874-00399}

\begintext

\vspace*{-0.5cm}

HH95-79 ([HH95] FS Aur-79) [Henden and Honeycutt, 1995; GSC~1874-399; 
$\alpha$(2000)= 05\hr 48\mm 03\fsec82, $\delta$(2000)= 28\deg 30\arcm 48\farcs13]
was observed as a part of our study of near-contact, solar-type binaries with possible stream impacts. Also, 
its rare combination of an EB-type light curve and very short period indicated that the system was made up of 
dwarf components, possibly harboring a brown dwarf.

\IBVSfig{8cm}{5849-f1.eps}{Finding chart, HH95-79, comparison star (C) and check star (K).}
\IBVSfigKey{5849-f1.eps}{GSC 01874-00399}{finding chart}

The system was discovered by Robertson et al. (2004) who gave the following ephemeris:
\begin{equation}
{\rm HJD\ Tmin\ I} = 2452963.744(\pm0.004) + 0.2508(\pm0.0001){\rm d\times E}.
\end{equation}

After the initial presentation of the present work in May 2005 (McKenzie et al., 2005), Austin et al. (2007) took 
observations in December 2005 in $UBV$ and obtained single line radial velocity curves of the primary and a spectroscopic 
identification of the primary of spectral type dM3e ($T\sim 4100$K). A synthetic light curve solution was given indicating a 
mass ratio of  0.52. They found that emission features were present confirming chromospheric activity and possibly 
circumstellar material. However, they did no modeling of a third light as we do here. They indicated a near contact 
configuration.  Since their absolute masses were based on single line curves, we can not regard these as definitive. 
The Center for Backyard Astrophysics observed 66 times of minimum light for the paper, some of which are duplicate epochs.  
They give an improved ephemeris:
\begin{equation}
{\rm HJD\ Tmin\ I} = 2452963.74445 + 0.250816 (\pm 0.000001){\rm d\times E}.
\end{equation}

No changes in the period over the rather brief period ($\sim 2$~years) are indicated, which is expected. This does not 
indicate, however, that the period is not changing. 

Our $U,B,V,R,I$ light curves were taken at the taken Southeastern Association for Research in Astronomy (SARA) 
observatory on Kitt Peak using a 0.9-m reflector with the AP7 CCD camera and standard $UBVR_cI_c$ filters. The CCD 
observations were taken on 7, 8 December 2004 and 21 March 2005 in remote mode by RGS and NCH. More than 100 
In the $B,V,R,I$ passbands, 97, 90, 94 and 95 images were taken, respectively as well as a 7 in the $U$ pass band (see Figure~1.). The stars 
[\hbox{GSC~2336-0621}, $\alpha$(2000)= 05\hr 48\mm 10\fsec29, $\delta$(2000)= 28\deg
 27\arcm 34\farcs38] and [GSC~1874-0609, $\alpha$(2000) = 
05\hr 47\mm 47\fsec37, $\delta$(2000)= 28\deg 29\arcm 46\farcs60]
were used as the comparison (C) and check (K) stars, respectively.  
A finding chart of HH95-79 (V), the comparison star (C), and check star (K) is given in Figure 1.  The light curves 
are given in Figure 2, as normalized flux versus phase. Our standardized observations are given in Table 1 (available through the IBVS website as {\tt 5849-t1.txt}) as Variable-comp magnitudes.
 
\IBVSfig{10cm}{5849-f2.eps}{B,V,R normalized flux light curves for HH95-79 with synthetic light curve solution overlaid.}
\IBVSfigKey{5849-f2.eps}{HH95-79}{light curve}

\IBVSedata{5849-t1.txt}
\IBVSdataKey{5849-t1.txt}{GSC 01874-00399}{}

Six mean epochs of minimum light were determined from eclipse timings 
in all pass bands, using parabola fits: 
HJD Tmin I = 2453348.7476 ($\pm$0.0011), 2453349.0008 ($\pm$0.0028) and 
HJD Tmin II = 2453347.8687  ($\pm$0.0015), 2453348.8715 ($\pm$0.0013), 
2453441.6739 ($\pm$0.0010), 2453450.7025 ($\pm$0.0030).

From all available observations (we used only primary eclipses and thus well determined ones from the CBA observations),
we calculated the following definitive improved linear ephemeris:
\begin{equation}
{\rm HJD\ TMin\ I} = 2453348.7473 (\pm0.0001) + 0.25081621 (\pm0.00000008){\rm d\times E}
\end{equation}

\IBVSedata{5849-t2.txt}
\IBVSdataKey{5849-t2.txt}{GSC 01874-00399}{}

The times of minimum light are given in Table 2 (available through the IBVS website as {\tt 5849-t2.txt}). Further observations
are needed to better characterize the period behavior of this system.
  
From standard star measurements taken on 7, 8 December 2004 we were able to obtain standard magnitudes at all quadratures,
and of C and K.  The results are given in Table 3 (available through the IBVS website as {\tt 5849-t3.txt}). The photometrically determined spectral types for the variable ranged 
from K7 to K9 while the comparison was K7$\pm$1 and check, G9$\pm$5. The apparent magnitude range of the variable was 
$V = 13.75-14.47$ mags while the comparison was 10.05$\pm$0.01 and check, 13.83 $\pm$0.02 mags in $V$.

 \IBVSedata{5849-t3.txt}
\IBVSdataKey{5849-t3.txt}{GSC 01874-00399}{}

Our light curves were premodeled with Binary Maker 2.0 (Bradstreet, 1992) and fits were obtained in $B$ and $V$ using 
semi-detached and contact configurations.  The hand model parameters gave starting values for a simultaneous  
$BVR$ synthetic light curve solution using the 2004 version of the Wilson Code (Wilson and Devinney, 1971; Wilson,
1990, 1994; Van Hamme and Wilson, 1998) which includes Kurucz atmospheres, and a detailed reflection treatment along 
with 2-D limb darkening coefficients and iterative spot modeling. We removed the I-curve since it was discrepant. We suppose 
this was due to local atmospheric effects, probably variable humidity. 

Our $BVR$ simultaneous solution yielded a mass ratio of 0.53$\pm$0.01, equal to that of Austin et al. (2007), within the errors.  
We list the parameters of that solution as Table~4, and display the light curve solution overlaying our data in Figure 2. 
The errors accompanying the corrected parameters in Table~4 are from the full set calculation, rather that subsets. Our 
displayed solution uses two hot spots two fit asymmetries.  Our solutions show a hot spot with a temperature factor near 
1.25 on the secondary component. Its location is that of a stream impact spot arising from a coming into contact binary.   
We believe the mass transfer is not vigorous at this time. The other spot is presumably magnetic in nature, 
arising from white light faculae. These may dominate the surfaces of short period, chromospherically active binaries (Guinan, 1990). 
Austin et al. (2007) used cool star spots, only, in their solution. Our Roche lobe model is given as Figure~3~and~4. 
All indications are that the secondary component is not a brown dwarf, but an early M-type main sequence star. \\

\IBVS2fig{7cm}{5849-f3.eps}{Geometrical representation of HH95-79 at phase 0.24 with stream spot shown on component 2.}{5849-f4.eps}{Geometrical representation of HH95-79 at phase 0.81 with second spot region shown on component 2.}
\IBVSfigKey{5849-f3.eps}{GSC 01874-00399}{}
\IBVSfigKey{5849-f4.eps}{GSC 01874-00399}{}

\begin{table}[!hr]
\small
\centerline{{\bf Table 4}: Synthetic Curve Parameters for HH95-79}
\begin{center}
\begin{tabular}{ll}
\hline
Parameter                              & Simultaneous solution\\
\hline
$\lambda_B, \lambda_V, \lambda_R$ (nm) &  440, 550, 640 \\
$x_{\rm bol1,2},y_{\rm bol1,2}$        &  0.540, 0.464, 0.276, 0.290 \\
$x_{\rm 1R,2R},y_{\rm 1R,2R}$          &  0.724, 0.778, 0.219, 0.336 \\
$x_{\rm 1V,2V},y_{\rm 1V,2V}$          &  0.778, 0.824, 0.289, 0.362 \\
$x_{\rm 1B,2B},y_{\rm 1B,2B}$          &  0.822, 0.857, 0.213, 0.341 \\
$g_1,g_2$  		               &  0.32, 0.32 \\
$A_1,A_2$                              &  0.5, 0.5 \\
inclination(\deg)                      &  86$\pm$1 \\
$T_1,T_2$ (K)                          &  4100, 3257$\pm$25 \\
$\Omega_1,\Omega_2$                    &  2.927$\pm$0.018, 3.045$\pm$0.038 \\
$q(m_2/m_1)$                           &  0.53$\pm$0.01  \\
JD Zero	                               &  53448.74716$\pm$0.00017 \\
Period                                 &  0.25081$\pm$0.00009  \\
$L_1/(L_1+L_2)_R$                      &  0.917$\pm$0.004 \\
$L_1/(L_1+L_2)_V$                      &  0.932$\pm$0.004 \\
$L_1/(L_1+L_2)_B$                      &  0.947$\pm$0.004 \\
$r_1, r_2$ (pole)                      &  0.410$\pm$0.002, 0.285$\pm$0.006 \\
$r_1, r_2$ (point)                     &  0.565$\pm$0.005, 0.342$\pm$0.017 \\
$r_1, r_2$ (side)                      &  0.434$\pm$0.002, 0.296$\pm$0.007 \\
$r_1, r_2$ (back)                      &  0.463$\pm$0.002, 0.319$\pm$0.010 \\
\hline
\end{tabular}
~\\
~\\
\centerline{Spot Parameters}
\begin{tabular}{ccccc}
\hline
STAR& Colatitude (\deg)&Longitude (\deg)&Spot Radius (\deg)&Temp. Factor\\
\hline
2   & 88$\pm$9     & 276$\pm$7    & 14$\pm$2    & 1.47$\pm$0.04\\
2   & 91$\pm$15    &  35$\pm$6    & 15$\pm$6    & 1.25$\pm$0.07\\
\hline
\end{tabular}
\end{center}
\end{table}

We wish to thank SARA for their allocation of observing time, and the American Astronomical Society for 
a small research grant which supported our observing runs. 
 
\newpage
\references

Austin, S.J., Robertson, J.W., Tycner, C., Campbell, T., Honeycutt, R.K., 2007, {\it AJ}, {\bf 133}, 1934

Bradstreet, D. H., 1992, {\it BAAS}, {\bf 24}, 1125

Guinan, E. F., 1990, {\it ESA SP}, {\bf 310}, 73, 
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Henden, A.A., Honeycutt, R.K., 1995, {\it PASP}, {\bf 107}, 324

Krajci, T., 2006, {\it IBVS}, 5690

Robertson, J. W., Austin, S.J., Campbell T., Hoskins, J., 2004, {\it IBVS}, 5536

McKenzie, R. T.; Samec, R. G.; Hawkins, N. C.; Faulkner, D. R.; Van Hamme, 2005, {\it BAAS}, {\bf 37}, 495

Van Hamme, W. V., Wilson, R.E., 1998, {\it BAAS}, {\bf 30}, 1402

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

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

\endreferences

\end{document}

