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\begin{document}

\IBVShead{4616}{27 July 1998}

\IBVStitletl{UBV Observations of the Solar-Type}{ Near Contact Binary, CN Andromedae}

\IBVSauth{Ronald G. Samec$^{1,3}$, Heidi Laird$^1$, Matthias Mutzke$^1$ and 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, SC 29721 USA, faulkner@gwm.sc.edu} %email


\IBVSinst{Visiting Astronomer, Lowell Observatory, Flagstaff, Arizona}

\SIMBADobj{CN And}

\begintext


CN And (BD+39\deg 59, GSC 2787-1815, PPM 42831) is one of the shortest period eclipsing
binaries with an unmistakable EB-type light curve. Its eclipse depths
differ by some 0.3 mags in V.   It is also an active solar type binary
with components of spectral type in the F5 to G5
range.  Due to these factors it was included as a target object in a
recent observing run at Lowell Observatory. The variable was discovered
by Hoffmeister (1949). L\"{o}chel (1960) was the first to correctly
determine the period, $\sim$0.4628 days. Photoelectric observations have
been made by Bozkurt et al.\ (1976), Seeds and Abernathy (1982), Kaluzny
(1983), Michaels et al. (1984), and Evren et al.\ (1987).  The curves
are characterized by interesting asymmetries (Rafert et al.\ 1985)
similar to V1010 Ophiuchi binaries (Shaw, 1994).  Its high level of
activity is attested by two flares seen by Yu-Lan and Qing-Yao (1985),
as well as its X-ray luminosity of log~L$_x$ = 30.55 (Shaw et al.\ 1996).

Our present observations were taken with the Lowell 0.79m reflecting
telescope in conjunction with a cooled S-13 type PMT on September 4-10,
1997.  Standard U, B, and V filters were used. The comparison
(HIP\#1442, GSC 02786-00787, spectral type G9), and  check stars, (GSC
02787-01843) are given as C, and K in Figure 1 along with the variable,
V. Over 1200 observations were taken in each pass band.  Three mean
epochs of minimum light were determined from one primary, and two
secondary eclipses using the bisection of chords method.  One
additional timing of minimum light, observed on November 25, 1997 was
determined by DRF using the David F. Irons 0.41-m reflector of the
Charlotte Amateur Astronomy Club using an SSP-5 PMT. The Hertzsprung
technique (1928) was used in its determination. The precision epochs of
minimum light are given in Table 1 along with their standard errors of
the last digits in parentheses.  Linear and quadratic ephemerides were
calculated using the available 60 epochs of minimum light:
$$
\hbox{J.D. Hel Min I} = 24 50698.9591(18) + 0.46279372 (13) \times E.
\eqno(1)
$$
$$
\hbox{J.D. Hel Min I} = 2450698.9447(14) + 0.46279092(19) \times E
-9.8(6) \times 10^{-11} \times E^2. \eqno(2)
$$
Equations 1 and 2 were used to calculate the O$-$C1 and O$-$C2
residuals, respectively, in  Table 1.  The linear and quadratic
residuals are given in Figure 2 and 3, respectively.
 

\IBVSfig{7cm}{4616-f1.ps}{Finding chart made from Real Sky of the
Variable, CN And, V, the comparison star, C, and the check star, K.}

\IBVSfig{9cm}{4616-f2.eps}{O--C residuals for all available timings of
minimum light as calculated from equation 1.}

\IBVSfig{9cm}{4616-f3.eps}{O--C residuals for all available timings of
minimum light as calculated from equation 2.}

\IBVSfig{10cm}{4616-f4.eps}{U, B, V light curves and U--B, B--V color
curves for CN And  as magnitude differences, variable minus comparison star.}



\begin{table}
\caption{New Epochs of Minimum Light, CN And}
\begin{center}
\begin{tabular}{lcrrr}
\hline
\hfil JD Hel. & Min & Cycles & O$-$C1 \hfil & O$-$C2 \hfil \\
\hfil 2450000+ \\
\hline
698.9423(9)  & I  & 0.0   & $-$0.0168 & $-$0.0024 \\
701.9521(5)  & II & 6.5   & $-$0.0151 & $-$0.0007 \\
702.8775(5)  & II & 8.5   & $-$0.0153 & $-$0.0010 \\
778.5410(10) & II & 172.0 & $-$0.0186 & $-$0.0037 \\
\hline
\multicolumn{3}{l}{
Std.\ error of all residuals:} & 0.0176	& 0.0100 \\
\hline
\end{tabular}
\end{center}
\end{table}

The quadratic term is statistically valid at the 16 s level. Also, the
O$-$C residuals yield a much better fit to the timings of minimum
light  as evidenced by the standard errors.

This gives strong evidence that the period decrease is a real one. The
period behavior may be due to mass transfer with the secondary
component as the accretor and/or magnetic breaking due to the strong
magnetic activity.  UBV light curves and the B$-$V and U$-$B color
curves of  the variable are shown as Figure 4 as differential standard
magnitudes (variable--comparison) versus phase.  The probable error of a
single observation was 0.4\% in B, 0.5\% in V and 1.8\% in U.  The
analysis of these difficult light  curves is underway.  A spotted
semi-detached light curve synthesis solution has been calculated.
	
We wish to thank  Lowell Observatory for their allocation of
observing time for the travel support from both the University
of South Carolina and Bob Jones University.

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


			
\references

Bozkurt, S., Ibanoglu, C., G\"{u}lmen, O., G\"{u}d\"{u}r, N., 1976,
IBVS  No.\,1087

Evren, S., Ibanoglu, C., Tunca, Z., Akan, M. C., Keskin, V., 1987, IBVS
No.\,3109

Hertzsprung, E., 1928, Bull.\ Astron.\ Inst.\ Neth.\ 4, 179

Hoffmeister, C., 1949, AN 12, 1

Kaluzny, J., 1983, AcA 33, 345
% Original: Kaluzny, J., 1983, AA 33, 345
% Corrected: Mon Aug 11 16:27:25 MET DST 2003

L\"{o}chel, K., 1960, MVS 457 \& 458

Michaels, E.J., Markworth N.L., and Rafert, J.B., 1984, IBVS No.\,2472 

Rafert, J.B., Markworth N.L.,  and Michaels, E.J., 1985, PASP 97, 310 

Seeds, M. A.,  and Abernathy D. K., 1982, PASP 94, 1001 
% Original: Seeds, M. A., 1982, and Abernathy D. K., PASP 94, 1001 
% Corrected: Mon Aug 11 16:27:25 MET DST 2003

Shaw J.S., 1994, Mem. Soc.\ Astron.\ Ital.\ 65, 95
% Original: Shaw J.S., 1994, Soc.\ Astron.\ Ital.\ 65, 1, 95
% Corrected: Mon Aug 11 16:27:25 MET DST 2003

Shaw, J. S., Caillault, J.-P., Schmitt, J.H.M.M., 1996, ApJ 461, 951

Yu-Lan, Y., Qing-Yao, L., 1985, IBVS No.\,2705

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