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\input ibvs2.sty

\begin{document}

\IBVShead{5044}{9 March 2001}

\IBVStitletl{DP Pegasi: CCD Light Curve and}{ Elements of Variation}

\IBVSauth{Diethelm, R.$^1$; Bl\"attler, E.$^2$; Guilbault, P.R.$^3$}

\IBVSinst{BBSAG and Astr.\ Inst.\ der Universit\"at Basel, Rennweg 1, CH-4118
Rodersdorf, Switzerland, \\ \indent e-mail: diethelm@astro.unibas.ch}
\IBVSinst{BBSAG, Sch\"usselacher 1, CH-8636 Wald, Switzerland, e-mail: blaettler-wald@bluewin.ch}
\IBVSinst{P.O. Box 287, Chepachet, Rhode Island 02814, USA, e-mail: pete1199@aol.com}


\SIMBADobj{DP Pegasi}

\IBVStyp{ EA }

\IBVSabs{For the first time, we report elements of variation for the}
\IBVSabs{neglected eclipsing binary DP Pegasi and give a CCD light curve}
\IBVSabs{based on these elements.}

\begintext

The star DP Pegasi = GSC\,1675.1817 = HV\,6121 (at 21\hr 22\mm
56\fsec0, +22\deg 03\arcm 46\arcs, (J2000); GSC-magnitude: 13.3) was
first reported by Shapley and Hughes (1934) to be variable. They
classified the star as an eclipsing binary of unknown period with a
photographic range of 13\fmm3--14\fmm2 and remarked that they had found
11 minima on their photographic plates, without giving further
information. An intensive search of the Harvard College Observatory's
archive by PG was not successful in locating the original data.
According to the SIMBAD data base, no other source of information
concerning the variability of DP Pegasi is available.

\IBVSfig{8.95cm}{5044-f1.eps}{Phased CCD light curve of DP Pegasi (no filter)}

\begin{center}
\normalsize
Table 1: Times of primary minimum, DP Pegasi
\vskip2mm
\begin{tabular}{llrlllc}
\hline
HJD 2400000\,+ & Error $\pm$ & Epoch & $O-C$ & Observer & 
Method\\
\hline
42743.479 & -- & $-$5279 & +0.140 & Harvard & ptg\\
43050.688 & -- & $-$5094 & +0.011 & Harvard & ptg\\
43070.598 & -- & $-$5082 & $-$0.014 & Harvard & ptg\\
43776.627 & -- & $-$4657 & $-$0.033 & Harvard & ptg\\
44512.628 & -- & $-$4214 & +0.018 & Harvard & ptg\\
44934.532 & -- & $-$3960 & $-$0.046 & Harvard & ptg\\
45635.557 & -- & $-$3538 & $-$0.084 & Harvard & ptg\\
45645.573 & -- & $-$3532 & $-$0.036 & Harvard & ptg\\
45695.453 & -- & $-$3502 & +0.006 & Harvard & ptg\\
45939.641 & -- & $-$3355 & $-$0.016 & Harvard & ptg\\
51513.283 & 0.003 & $ $0 & +0.005 & Diethelm & ccd, no
filter\\
51757.490 & 0.003 & +147 & +0.003 & Diethelm & ccd, no
filter\\
51767.457 & 0.003 & +153 & +0.002 & Diethelm & ccd, no
filter\\
51797.3607 & 0.0010 & +171 & +0.0024 & Bl\"attler & ccd, no
filter\\
\hline
\end{tabular}
\end{center}

\bigskip

We have started an observing campaign with our CCD equipment in order
to clarify these open questions. RD used the 35-cm RC-telescope and a
SBIG ST-6 CCD-camera (no filter) of the R. Szafraniec Observatory,
Metzeren, Switzerland, securing a total of 111 observations in 26
nights between JD\,2451459 and JD\,2451925. EB observed with a SBIG
ST-7 CCD-camera (no filter) mounted on a 15-cm refractor at his private
observatory in Wald, Switzerland. He gathered a total of 124
measurements in two nights, namely JD\,2451797 and JD\,2451799. All
CCD exposures were dark-subtracted and flat-fielded before aperture
photometry was performed. No correction for differential extinction was
applied due to the proximity of the comparison stars to the variable
and the limited accuracy of our photometry at the brightness level of
DP Pegasi ($\pm 0\fmm03$). We used GSC\,1675.1720 (GSC-magnitude: 13.8)
as primary comparison star, while several field stars, some not
contained in the GSC, served as check stars, proving the constancy of
the comparison star.

In Figure 1, we show the results of our photometry, folded with the
period (1\fday661272) we considered to yield the best representation of
our observations.

In order to improve the period value, PG searched the plate collection of
Harvard College Observatory for minima of the variable. The plates of the Damon
and RH patrol series yielded a number of dimmings given in Table 1 along
with the CCD timings already published in the BBSAG Bulletins. The $O-C$ values
are calculated from the elements:
$$ \begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~} 2451513.278 & {}+ 1\fday6612879 & {} \times E.\\
\pm 0.005 & \pm 0.0000060 \\
\end{array} $$

{\it Acknowledgements:} Photometry at the R. Szafraniec Observatory is
supported financially by the ``Emilia Guggenheim-Schnurr'' foundation and
RD wishes to acknowledge this help gratefully. We also wish to express
our gratitude towards A. Doane, acting Curator ofthe Astronomical
Photograph Collection at the Harvard CollegeObservatory, for the use of
the Harvard Patrol Plates on this and other variable star projects.
This research made use of the SIMBAD data base, operated at CDS,
Strasbourg, France.

\reference

Shapley, H., Hughes, E.M., 1934, {\it Harvard Ann.}, {\bf 90}, No.\ 4

\endreferences

\end{document}

