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\IBVShead{5531}{21 May 2004}

\IBVStitle{Discovery of a {\Large \boldmath $\delta$} Scuti Star in V469 C\lowercase{yg}}

\IBVSauth{Caton, D. B.}

\IBVSinsto{Dark Sky Observatory, Dept. Physics and Astronomy, Appalachian State University, Boone, North Carolina 28608, U.S.A.; email: catondb@appstate.edu}

\SIMBADobj{V469 Cyg}

\begintext

V469 Cygni was first identified as a variable star by Wachmann (1940), with a light curve and ephemeris elements published later (Wachmann, 1948).  The system was also apparently independently discovered to be an eclipsing binary by Whitney (1947).  We added V469 Cygni to our ongoing program of monitoring eccentric orbit, apsidal motion and other systems for period changes based on its appearance on a list of apsidal systems published by Heged\"{u}s (1988).  This system was observed at Appalachian State University's Dark Sky Observatory, using the 0.80-m telescope equipped with a Photometrics (now Roper) CH200 CCD camera with a Tek 1024$^2$ chip and Bessel filter set.  Observations obtained of secondary eclipse on the night of UT 12 July, 2003 showed light variations characteristic of $\delta$ Scuti behavior.  A recent compilation of $\delta$ Scuti stars by Rodr\'{\i}guez et al. (2000) lists 86 stars that are members of multiple systems, with only nine found in eclipsing binaries (Rodr\'{\i}guez and Breger, 2001).  V469 Cyg now appears to be an additional system. We note that a search for $\delta$ Scuti stars in binary systems is under way by Szekely (2003).
    The data were reduced using Mira AP software.\IBVSfm \IBVSfoot{The Mira AP software is produced by Axiom Research Inc.}  The instrumental light curves for the observed secondary, in the B,V and R filters are shown in Figure 1.

The pulsations have a period of about 40 minutes and a total amplitude of about 0.02 magnitudes.
    A primary eclipse was observed on UT 24 August, 2003 (Figure 2).  While the pulsations are visible across secondary, their amplitude appears to drop greatly in primary, possibly indicating that the $\delta$ Scuti star is the hotter of the pair of stars.  However, the pulsation may simply not be visible due to the steeper scale of the primary eclipse.

\IBVSfig{9cm}{5531-f1.eps}{Secondary eclipse of V469 Cyg on the night of UT 12 July 2003}.  
\IBVSfigKey{5531-f1.eps}{V469 Cyg}{light curve}

\IBVSfig{9cm}{5531-f2.eps}{Primary eclipse of V469 Cyg on the night of UT 24 August 2003}
\IBVSfigKey{5531-f2.eps}{V469 Cyg}{light curve}

\vspace*{-0.85cm}

    We had in fact already observed a primary eclipse (in the V filter, only) in 1997 but had not noticed the variations due to the scale of the eclipse and because we had little outside eclipse coverage.  We have also obtained other eclipses, for a total of five.  The times of minimum light for the five events are given in Table 1.

\begin{table}
\begin{center}
{\normalsize Table 1. Times of minimum light.} \vskip2mm 
\begin{tabular}{cccrr}
\hline
Time of minimum & Error & Filter & Type & O -- C\\
(HJD-2400000) & & & & (GCVS)\\
\hline
50751.71107 & 0.00045 & V & I & $-$0.07735\\
52832.68745 & 0.00059 & B & II & \\
52832.68925 & 0.00058 & V & II & \\
52832.69380 & 0.00057 & R & II & \\
52876.66165 & 0.00079 & B & I & $-$0.09018\\
52876.65885 & 0.00161 & V & I & $-$0.09298\\
52876.66115 & 0.00077 & R & I & $-$0.09068\\
52978.63930 & 0.00054 & B & II & \\
52878.63995 & 0.00056 & V & II & \\
52878.63880 & 0.00056 & R & II & \\
52893.72150 & 0.00058 & V & I & $-$0.09304\\
\hline
\end{tabular}
\end{center}
\end{table}

    Our times of minimum and their standard errors were calculated using the method of Kwee \& van Woerden (1956), using an algorithm by Ghedini (1982).  The times for each filter are listed individually since some do not overlap by their formal errors.  This appears to be due to differences of the pulsation amplitude with color.  The pulsation contribution makes it difficult to get an accurate time of minimum light.  In the case of JD 2452876, clouds interrupted the observations briefly, with more V images having been randomly lost than in the B and R. The (O -- C) values in Table I are computed with ephemerides from the General Catalog of Variable Stars (Kholopov et al., 1985).

    A linear regression analysis of our times and those of Hoffmeister et al. (1954) and Whitney results in a new ephemeris for primary eclipse given by $HJD_{\rm min}=2428814.3986+1.3125109 E$.  

    The entry for V469 Cyg in Heged\"{u}s's table of systems with eccentric orbits or displaced secondaries gives the secondary at phase 0.57.  However, using our results we obtain a current phase of 0.508.

    We are grateful for references provided by Greg Shelton and Brenda Corbin at the U.S. Naval Observatory Library.  Other references were obtained at the NASA Astrophysics Data System. This work also made use of the SIMBAD data base and the Space Telescope Science Institute's Digitized Sky Survey.  Support was also received from the National Science Foundation.

\references

Ghedini, S., 1982, {\it Software for Photometric Astronomy}, Willmann-Bell, U.S.A., p.47

Heged\"{u}s, T., 1988, {\it Bulletin Inf. Centre Donnees Stellaires}, {\bf 35}, 15

Hoffmeister, C. Ahnert-Rohlfs, E., Ahnert, P., Huth, H. and Gotz, W., 1954,{\it Ver\-\"of\-fen\-li\-chun\-gen der Sterwarte in Sonneberg}, {\bf 2}, No. 2, 143

Kholopov, P. N., et al., 1985, {\it General Catalog of Variable Stars}, 4th Eds.

Kwee, K. K. \& van Woerden, H., 1956, {\it Bull. Astron. Inst. Neth.}, {\bf 12}, 327

Rodr\'\i guez, E., Breger, M., 2001, {\it A\&A}, {\bf 366}, 178

Rodr\'\i guez, E., L\'opez-Gonz\'alez, M. J., L\'opez de Coca, P., 2000, {\it A\&AS}, {\bf 144}, 469

Sz\'ekely, P., 2003, {\it IBVS}, No. 5467

Wachmann, A.A., 1940, {\it Beobachtungs z.d. Astron. Nach.}, {\bf 22}, no.\,2, p. 10

Wachmann, A.A., 1948, {\it Astron. Abh. Erg\"anzungshefte z.d. Astron. Nach.}, {\bf 11}, no.\,5

Whitney, B., 1947, {\it A.J.}, {\bf 53}, 13

\endreferences

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%From IBVS 5576
\IBVSerratum{5531}

Figure captions in this issue are swapped, Fig. 1. shows the primary eclipse, 
while Fig. 2. is the secondary eclipse.

\bigskip

The Editors


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