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\begin{document}

\IBVShead{5111}{12 June 2001}

\IBVStitle{The Period Behaviour of the Eclipsing Binary LD 328}

\IBVSauth{Lloyd, C.$^1$; Dahlmark, L.$^2$; Guilbault, P.$^3$; Hager, T.$^4$; Henden, A.A.$^5$; James, N.D.$^6$;\\ \indent Kaiser, D.H.$^7$; Kinnunen, T.$^8$; Lubcke, G.C.$^9$}

\IBVSinst{Space Science \& Technology Department, Rutherford Appleton
Laboratory, Chilton, Didcot,\\ \indent Oxon.\ OX11~0QX, UK,
e-mail: {\tt cl@astro1.bnsc.rl.ac.uk}}

\IBVSinst{R\'{e}s.\ Jeanne d'Arc, 176 Av.\ Majoral Arnaud, F-04100 Manosque,
France}

\IBVSinst{P.O. Box 287, Chepachet, Rhode Island 02814, USA,
e-mail: {\tt pete1199@aol.com}}

\IBVSinst{34 Mount Tom Road, New Milford, Connecticut 06776, USA,
e-mail: {\tt thager@pcnet.com}}

\IBVSinst{Universities Space Research Association/U.S. Naval
Observatory, P.O. Box 1149, Flagstaff,\\ \indent  Arizona
86002-1149, USA, e-mail: {\tt aah@nofs.navy.mil}}

\IBVSinst{11 Tavistock Road, Chelmsford, Essex CM1 6JL, UK
e-mail: {\tt ndj@blueyonder.co.uk}}

\IBVSinst{2631 Washington Street, Columbus, Indiana 47201, USA,
e-mail: {\tt dhkaiser@sprynet.com}}

\IBVSinst{Ursa Astronomical Association, Raatimiehenkatu 3 A 2, SF-00140
Helsinke, Finland,\\ \indent
e-mail: {\tt stars@personal.eunet.fi}}

\IBVSinst{3817 Patrick Henry Way, Middleton, Wisconsin 53562, USA,
e-mail: {\tt gil2@ix.netcom.com}}

\SIMBADobjAliasJ2000{LD 328}{GSC 3256-0458}{00 26 49.09 +49 40 35.7}
\IBVStyp{ EA }
\IBVSkey{Algol-type - period change}
\IBVSabs{Photographic, visual and CCD observations of LD 328 show it to be an}
\IBVSabs{eclipsing binary with a period of 1.0838485 days, increasing at}
\IBVSabs{P'/P = 5.6 * 10^{-7}/yr.}

\begintext

LD~328 (GSC 3256-0458, 00\hr26\mm49\fsec09, +49\deg40\arcm35\farcs7 (USNO
A2.0)), was discovered to be variable by Dahlmark (1999) during a
photographic survey of the northern Milky Way. Dahlmark suggested that
the star was an eclipsing binary with an amplitude of 1.0 mag at $V$, but
was unable to find the period. The period has now been determined from
Dahlmark's data and extensive visual observations, and its behaviour over
most of the last century has been followed using further observations
from the Harvard plate archive, and recent CCD observations.

LD~328 has been examined on plates of the Harvard College Observatory
archive RH Patrol Series (1928--1952), limiting magnitude 14-15, Damon
Patrol Series (1965--1990), limiting magnitude 14--15, and AC Series
(1898--1954), limiting magnitude 12, although some are much fainter. The
plates are blue sensitive and magnitudes of LD~328 have been estimated
visually by Guilbault on 171 RH, 119 Damon and 27 AC Series plates
against comparison stars with magnitudes from USNO A2.0 (Monet et al.\
1998). The Harvard data provide 15 times of minima, although one timing
is inconsistent with the others. Dahlmark's (1999) observations were made
between 1967 and 1999 using Kodak 103aD + GG11 and TechPan 4415 + GG495
emulsion/filter combinations, giving approximately $m_{\rm pv}$
magnitudes, which were determined by visual comparison against nearby
stars with GSC magnitudes. The light curve is previously unpublished and
provides six times of minima. An extensive series of visual observations
by Guilbault and Kinnunen, which initially allowed the period to be
resolved, contain eleven times of minima, although all but the last of
these are based on single observations. Recent CCD observations by Hager,
Henden, James, Kaiser and Lubcke have provided a complete light curve at
$V$, and most of the primary minimum in the red (unfiltered CCD). These
observations provide accurate timings of three primary minima and one
secondary minimum, and are described in more detail by Lloyd et al.\
(2001).

\IBVSfig{8cm}{5111-f1.eps}{The $O-C$ diagram of the times of minima using
the linear terms of the ephemeris, with the quadratic fit shown. The
Harvard data are shown by filled circles, Dahlmark's data, open circles,
visual data, open squares and CCD data, filled squares}

\vskip-11pt
All the times of minima have been collected in Table~1 and the $O-C$
diagram is shown in Figure~1. The residuals show clear curvature
indicating a changing period. In fitting a parabolic ephemeris it has
been necessary to give the CCD observations high weights to force the
solution through them. Also, all but the first of Dahlmark's times of
minima have been excluded from the solution as they appear to be
systematically high, although it is not clear if this has any significance. The
visual timings have also not been used as they are relatively recent
and are much less reliable than the CCD timings. The adopted parabolic
ephemeris is
$$
{\rm HJD_I} = 2451559.2824(29) + 1.0838485(14)\times E + 9.0(7)\times
10^{-10}\times E^2
$$
and is subject to small variations depending on the weights used. The
$O-C$ diagram using the linear terms of the ephemeris in shown in
Figure~1. The phase diagrams of the Harvard data for 1928--1951 and
1975--1989 are shown in Figure~2, and are constructed using a changing
period. The linearized phase diagram of Dahlmark's data is shown in
Figure~3.

Photometric modelling of the CCD observations by Lloyd et al.\ (2001) suggests
that the system is a relatively cool Algol binary containing components
of spectral type late A and late G, with the secondary probably filling
its Roche lobe. The rate of period change, $\dot{P}/P=5.6\times
10^{-7}$~yr$^{-1}$ is not unlike other Algol systems, and suggests that
there is continuing mass transfer in the system.

The authors would like to thank Dr.\ Martha Hazen, Curator of the
Astronomical Photograph Collection of the Harvard College Observatory,
for access to the plates of this and other variable stars.

\IBVSfig{12cm}{5111-f2.eps}{The linearized phase diagram of the early Harvard
data, 1928--1951 (top), and the later Harvard data, 1975--1989
(bottom) folded using the parabolic ephemeris}

\IBVSfig{8cm}{5111-f3.eps}{The linearized phase diagram of Dahlmark's data}

\clearpage

\begin{table}[h!]
\begin{center}
\caption{Times of minima of LD~328}
\begin{tabular}{lrrcl} \hline
 HJD  & Cycle & $O-C$ & band & Observer \\ \hline
 2428110.635 & $-$21635 &   0.4149 &  pg  & Guilbault \\
 2428872.551 & $-$20932 &   0.3854 &  pg  & Guilbault \\
 2429246.478 & $-$20587 &   0.3847 &  pg  & Guilbault \\
 2429907.616 & $-$19977 &   0.3751 &  pg  & Guilbault \\
 2433206.730 & $-$16933 &   0.2543 &  pg  & Guilbault \\
 2445668.558 &  $-$5435 &  $-$0.0078 &  pg  & Guilbault \\
 2445757.512 &  $-$5353 &   0.0706 &  pg  & Guilbault \\
 2445991.611 &  $-$5137 &   0.0583 &  pg  & Guilbault \\
 2446055.509 &  $-$5078 &   0.0093 &  pg  & Guilbault \\
 2446107.506 &  $-$5030 &  $-$0.0184 &  pg  & Guilbault \\
 2446728.590 &  $-$4457 &   0.0204 &  pg  & Guilbault \\
 2446998.493 &  $-$4208 &   0.0451 &  pv  & Dahlmark \\
 2447028.817 &  $-$4180 &   0.0213 &  pg  & Guilbault \\
 2447116.568 &  $-$4099 &  $-$0.0194 &  pg  & Guilbault \\
 2447141.536 &  $-$4076 &   0.0201 &  pg  & Guilbault \\
 2447446.731 &  $-$3794 &  $-$0.4302 &  pg  & Guilbault \\
 2449546.571 &  $-$1857 &  $-$0.0047 &  pv  & Dahlmark \\
 2449919.468 &  $-$1513 &   0.0484 &  pv  & Dahlmark \\
 2449957.380 &  $-$1478 &   0.0257 &  pv  & Dahlmark \\
 2450835.310 &   $-$668 &   0.0384 &  pv  & Dahlmark \\
 2451223.317 &   $-$310 &   0.0276 &  pv  & Dahlmark \\
 2451430.355 &   $-$119 &   0.0506 & vis  & Kinnunen \\
 2451431.4354&   $-$118 &   0.0471 & vis  & Guilbault \\
 2451432.4479&   $-$117 &  $-$0.0242 & vis  & Guilbault \\
 2451432.451 &   $-$117 &  $-$0.0211 & vis  & Kinnunen \\
 2451443.3299&   $-$107 &   0.0193 & vis  & Guilbault \\
 2451443.334 &   $-$107 &   0.0234 & vis  & Kinnunen \\
 2451493.211 &    $-$61 &   0.0434 & vis  & Kinnunen \\
 2451522.4722&    $-$34 &   0.0406 & vis  & Guilbault \\
 2451525.7007&    $-$31 &   0.0176 & vis  & Guilbault \\
 2451549.5444&     $-$9 &   0.0166 & vis  & Guilbault \\
 2451559.2854&      0 &   0.0034 & ccd  & James \\
 2451585.2977&     24 &   0.0014 & ccd  & James \\
 2451821.574 &    242 &   0.0003 & vis  & Guilbault \\
 2451931.5829$\dagger$&    343 &  $-$0.0015 &  $V$   & Henden \\
 2451937.5451&    349 &  $-$0.0004 &  $V$   & Lubcke \\
 2451937.5456&    349 &   0.0001 &  $V$   & Kaiser \\ \hline
\end{tabular}

\normalsize $\dagger$: Secondary minimum
\end{center}
\end{table}

\vskip-24pt

\references

Dahlmark, L., 1999, {\it IBVS}, No.\ 4734

Lloyd, C., Hager, T., Henden, A.A., James, N.D., Kaiser, D.H., Lubcke, G.C.,
2001, {\it IBVS}, No.\ 5112

Monet, D., Bird, A., Canzian, B., Dahn, C., Guetter, H., Harris, H., Henden, A.,
Levine, S., Luginbuhl, C., Monet, A.K.B., Rhodes, A., Riepe, B., Sell, S.,
Stone, R., Vrba, F., Walker, R., 1998, The USNO-A2.0 Catalogue

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