\documentstyle[epsf,twoside]{article}

\input ibvs2.sty
\input ibvst.sty

\begin{document}

\IBVShead{4931}{26 July 2000}

\IBVStitle{HD 218179: a New Long Period Bright EB in Cepheus}

\IBVSauth{Gomez-Forrellad, J.M.}

\IBVSinsto{Grup d'Estudis Astronomics, Apartado 9481, 08080 Barcelona, Spain}

\IBVSinsto{Esteve Duran Observatory Foundation, Montseny 46 --- Urb.\ El Montanya,
08553 Seva, Barcelona, Spain\\ \indent e-mail:jmgomez@astrogea.org}

\SIMBADobjAlias{HD 218179}{BD+63 1925}

\begintext

\IBVSTnam{HD 218179 = BD\,+63\deg1925 = PPM 24170 = SAO 20407 = AGK\,+63\deg1302 = GSC 4286\_80}

\IBVSTcoo{23\hr04\mm47\sec}{+64\deg05\arcm25\arcs}{2000.0}

\IBVSTobs{Mollet Observatory,
8-cm automatic refracting telescope}

\IBVSTdet{CCD}

\IBVSTfil{V}

\IBVSTcomp{SAO 20384 = PPM 24142 = HIP 113793 = HD 217872 = GSC 4282\_919}

\IBVSTchk{
  1: SAO 20422 = PPM 24186 = HIP 114070 = HD 218342 = GSC 4282\_391\\
& 2: SAO 20405 = PPM 24168 = HIP 113947 = HD 218139 = GSC 4282\_255}

\IBVSTsysn

\IBVSTdata{Upon request}

\IBVSTtyp{ EB }

\IBVSTrem{
HD 218179 whose spectral type is F0, is listed in the TYCHO Catalogue with
flag `V' (strong evidence of variability in de Tycho data) with an amplitude
variation between 7.47 and 7.76. The variability of this star was initially
reported by Olsen (1983), who detected light changes while performing
Str\"omgren photometry of nearly all Henry Draper stars of types A5 to G0
and brighter than $m_v=8\fmm3$. This star is also listed in the New Catalogue 
of Suspected Variable Stars Supplement with number 26012 (Kazarovets et al.,
1998). In addition, in an analysis for searching sinusoidal light variations
of the stars in the Tycho Catalogue, Koen and Schumann (1999) concluded that
this star was variable with a 17.950 day period.\\
Satellite photometric data from the Tycho instrument was reanalized and the
results suggested that this star might be an EB variable with a period of
35.9 days. To verify this point the star was observed for 100 nights between
9 September 1997 and 25 February 1999. This star is a visual double (MLR 7)
with 8\fmm1 and 8\fmm9 components separated by 0.4 arcseconds (Olsen, 1980),
so joint photometry had to be performed. Present observations confirmed the
preliminary analysis, showing that HD 218179 is an EB variable with a period
of 35.93 days and a 0.33 magnitude variation (from 7.41 to 7.74 in $V$) for
minimum I\@. In addition, its light curve shows that the secondary minimum,
0\fmm21 deep, is centered at phase $0.486\pm0.006$. In spite
of Tycho data scatter, they were of great help to obtain the following
ephemeris:
$$\begin{array}{r@{}r@{}l}
{\rm HJD~Min\,I} = 2451018.846 & {} + 35.928 & {} \times E.\\
                      \pm 0.2 &   \pm 0.004 \\
\end{array}$$
Also the following single secondary minimum was determined:
${\rm HJD~Min\,II} = 2451036.319 \pm 0.16$.}

\IBVSfig{9cm}{4931-f1.eps}

\newpage

\IBVSTack{
For this research the SIMBAD database, operated by CDS, Strasbourg, France,
was utilized.}

\references

ESA, 1997, The Hipparcos and Tycho Catalogues, ESA SP-1200

Kazarovets E.V., Durlevich O.V., Samus N.N., 1998, New Catalogue of
Suspected Variable Stars. Supplement,
http://www.sai.msu.su/groups/cluster/gcvs/gcvs/nsvsup/

Koen, C., Schumann, R., 1999, {\it MNRAS}, {\bf 310}, 618

Olsen, E.H., 1980, {\it Astron.\ Astrophys, Suppl.\ Ser.}, {\bf 39}, 205

Olsen, E.H., 1983, {\it Astron.\ Astrophys, Suppl.\ Ser.}, {\bf 54}, 55

\end{document}
