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\IBVShead{4753}{26 August 1999}

\IBVStitletl{UBV Observations of the Mass Exchanging }{ Solar-Type Binary, BE Cephei}

\IBVSauth{Ronald G. Samec$^{1,3}$, N.W. Gothard$^1$, B.C. Parker$^1$, T.W. Savage$^1$, S.D. Anderson$^1$, Danny R. Faulkner$^{2,3}$} 

\IBVSinst{Department of Physics, Bob Jones University, Greenville, SC 29614 USA, rsamec@bju.edu} %email


\IBVSinst{University of South Carolina-Lancaster, Lancaster, SC 29721 USA, faulkner@gwm.sc.edu} %email


\IBVSinst{Visiting Astronomer, Lowell Observatory}

\SIMBADobj{BE Cep}

\begintext

Recently, we began an observation program aimed at obtaining precision multiband photometry of short period solar type binaries in the 0\fday3 to 0\fday5 period range. In this group, we expected to find some eclipsing binaries in a very near a state of contact, with one component experiencing Roche-lobe overflow. Systems with unambiguous EB light curves, and complicating asymmetries were targeted. BE Cephei (SVS~925~Cep, GSC~3996-75, ${\rm RA}(2000) = 22\hr40\mm51\fsec59$, ${\rm DEC}(2000) = 58\deg40\arcm7\farcs5$) is such a candidate. 

\IBVSfig{9cm}{4753-f1.eps}{Finding chart (from The Palomar Sky Survey) of BE Cephei, V, the comparison star, C, and the check star, K.}

\newpage
\IBVSfig{8.5cm}{4753-f2.eps}{$O-C$ residuals for all available timings of minimum light as calculated from Equation (1).}

\IBVSfig{10.5cm}{4753-f3.eps}{$U$, $B$, $V$ light curves and $U-B$, $B-V$ color curves for BE Cephei as standard magnitude differences, variable minus comparison star.}

\newpage

\begin{table}
\caption{Epochs of Minimum Light, BE Cep}
\begin{center}
\begin{tabular}{lrrrc}
\hline
JD Hel. & \multicolumn{1}{c}{\raise-6pt\hbox{Cycles}} & \multicolumn{1}{c}{\raise-6pt\hbox{$(O-C)_1$}} & \multicolumn{1}{c}{\raise-6pt\hbox{$(O-C)_2$}} & \multicolumn{1}{c}{\raise-6pt\hbox{Source}} \\[-6pt]
2400000+ \\
\hline
45647.3090 & 0.0 & 0.0021 & $-0.0036$ & KL \\ 	
51021.8381(2) & 12664.0	& 0.0008 & 0.0020 & PO \\
51022.8970(5) & 12666.5	& $-0.0013$ & $-0.0001$ & PO \\
51069.7933(2) & 12777.0 & $-0.0006$ & 0.0008 & PO \\
51070.8534(4) & 12779.5	& $-0.0014$ & $-0.0001$ &	PO \\
51074.6725(4) & 12788.5	& $-0.0019$ & $-0.0006$ &	PO \\
51074.8854(2) & 12789.0	& $-0.0012$ & $-0.0002$ &	PO \\
51156.3698 & 12981.0 & $-0.0005$ & $-0.0010$ & BE \\
51162.3117 & 12995.0 & $-0.0001$ & 0.0014 & BE \\
\hline
\end{tabular}

\normalsize
\begin{tabular}{rl}
Sources: & KL = Kaluzny (1986),\\
& BE = BBSAG \#118, \#119, E. Blatte, \\
& PO = Present Observations. \\
\end{tabular}
\end{center}
\end{table}

BE Cep was discovered by Florija (1950), whose light curve is of EB-type with an difference of eclipse depths of 0.11 mag. He calculated the following light elements:
$$
{\rm J.D.~Hel~Min~I} = 2428751.314 + 0.424400 \times E.
$$
Hoffman (1984) took $B,V$ photoelectric observations and archived them.
Kaluzny (1986) used the observations to determine two timings of minimum
light and to calculate a $B$ curve solution from phase-binned averages.
He performed a ``grid of solutions'' with nonphysical albedoes (3 to 6),
and gravity darkening (fixed at 0), to accommodate the light curve
distortions. Subsequent times of minimum light have been published by 
Romano (1958), Ashbrook (1952, 1953), Borovicka (1986), Kolarova (1986), and in the BBSAG issues \#98, \#99, \#101 and \#102, all by Kurt Locher, and the BBSAG \#118 and \#119 by Ernst Blatter with CCD. 

Our present $UBV$ observations were taken with the Lowell 0.79-m reflecting telescope on the nights of July 25--27, 29--30 (RGS and DRF) and September 11--13, and 17 (DRF), 1998 with a thermoelectrically blue-enhanced, S-13 cathode, PMT. About 850 observations were taken at each filter. The comparison (GSC 03996-637, ${\rm RA}(2000) = 22\hr 40\mm 51 \fsec59$, ${\rm DEC}(2000) =58 \deg40 \arcm7 \farcs5$), and check star (GSC 03996-1524, ${\rm RA}(2000) = 22 \hr41 \mm01 \fsec25$, ${\rm DEC}(2000) = 58\deg38\arcm59\farcs1$) are shown as C, and K in Figure 1 along with the variable, V. The ${\rm V-C}$ magnitudes averaged 0.12 mags and 0.10 mags in $\Delta(B-V)$ and \hbox{$U-B$}, respectively. Preliminary photometric transformations yield $B-V = 0.74$, which corresponds to a G7 spectral type for the primary component. The magnitude range is 11.80--12.51 in $V$.

Six mean epochs of minimum light were determined from the observations made during three primary and three secondary eclipses by our undergraduate researchers using the bisection of chords technique. These precision epochs of minimum light are given in Table~1 along with their standard errors in parentheses. Linear and quadratic ephemerides were calculated using the available 31 epochs of minimum light:
\begin{equation}
{\rm J.D.~Hel~Min~I} = 2445647.3068(22) + 0.42439438(15) \times E,
\end{equation}
\begin{equation}
{\rm J.D.~Hel~Min~I} =2445647.3126(12) + 0.424394036(71) \times E - 1.6(3) \times 10^{-11} \times E^2.
\end{equation}
Equations 1 and 2 were used to calculate the $(O-C)_1$ and $(O-C)_2$ residuals, respectively, in Table~1. The linear residuals are shown in Figure 2.

The $UBV$ light curves and the $B-V$ and $U-B$ color curves of the variable are shown as Figure 3 as differential standard magnitudes (${\rm V-C}$) versus phase. The probable error of a single observation was 8, 9, and 10 mmag in $U$, $B$ and $V$, respectively. A near contact solution with a stream impact spot and cool spot has been computed using the Wilson Code (Wilson 1994, 1990, Wilson \& Devinney 1971). The final parameters include: $T_1-T_2= 460$~K, $m_2/m_1 = 0.680(6)$, and fill-out-factor = 98.5 \%. The impact spot parameters are co-latitude = 90(4), longitude = 350(1), Spot Radius = 8(2), T-Factor = 1.21(5). 	

We wish to thank Lowell Observatory for their allocation of observing time for the travel support from the University of South Carolina, and Bob Jones University, particularly Dr.\ James Roach, physics chair, for allowing us to include binary star analysis as a part of our regular
department curriculum.

This research was partially supported by a grant from NASA administered
by the American Astronomical Society.

\references

Ashbrook, J. 1952, AJ 57, 63. 

Ashbrook, J. 1953, AJ 58, 171. 

Borovicka, J. 1986, BRNO \#28, 12

Florija, N. 1950, Per.\ Zvezdy 5, 528

Hoffman, M. 1984, Ver\"off.\ der Astron.\ Inst.\ Bonn \#96, 1c6 

Kaluzny, J. 1986, PASP 98, 662

Kolarova, H. 1986 BRNO \#28,12

Romano, R. 1958, Padua Pub.\ 109, 3

Wilson, R. E. 1990, ApJ 356, 613

Wilson, R. E. 1994, PASP 106, 921

Wilson, R. E. \& Devinney, E. J. 1971, ApJ 166, 605

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