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\input ibvs2.sty
\input ibvst.sty

\begin{document}

\IBVShead{4945}{28 August 2000}

\IBVStitle{GSC 05178\_01376: A New W UM\lowercase{a} Variable}

\IBVSauth{Dvorak, S. W.}

\IBVSinsto{Rolling Hills Observatory; e-mail: rollinghillsobs@cfl.rr.com}

\SIMBADobj{GSC 05178-01376}

\IBVStyp{ EW }

\IBVSabs{Observations of a new EW-type variable, GSC 05178\_01376, are }
\IBVSabs{presented.  This variable is one of many discovered by The Amateur }
\IBVSabs{Sky Survey (TASS)}

\begintext

\IBVSTnam{GSC 05178\_01376}

\IBVSTcoo{20\hr48\mm13\sec}{$-01\deg29\arcm26\arcs$}{J2000.0}

\IBVSTobs{Rolling Hills Observatory, 0.20-m Schmidt--Cassegrain telescope}

\IBVSTdet{Cookbook 245 CCD (CB245)}

\IBVSTfil{No, roughly $R$ (CB245 camera)}

\IBVSTcomp{GSC 05178\_01373}

\IBVSfig{7.6cm}{4945-f1.ps}{Phase diagram of GSC 05178\_01376}

\IBVSTsysn

\IBVSTdata{Upon request}

\IBVSTrem{
The Mark III survey of The Amateur Sky Survey (TASS) has collected
numerous measurements of stars along the equator using drift scan CCDs
mounted behind 135-mm telephoto lenses (Richmond et al., 2000).
Analysis of the data has produced a number of new variables
(Gutzwiller, 1999).  One of these, GSC 05178\_01376, was observed by
the author to verify the classification by Gutzwiller and to determine
an ephemeris.\\
%
Data were obtained on five nights. Each ``observation'' was composed
of four or five separate 10\sec\ images. After dark images were
subtracted and flats applied, aperture photometry using sextractor
(Bertin and Arnouts, 1996) was used to generate star lists. The
difference ($\Delta m$) between GSC 05178\_01376 and the nearby star GSC
05178\_01373 ($m_v$ = 9.30) was calculated for each 10\sec\ image. The
data for all images comprising an ``observation'' were averaged and the
standard deviation calculated. A heliocentric correction was applied to
the data.\\
%
The TASS tenxcat database contains 59 $I$ observations of GSC
05178\_01376. The data were sorted to find the faintest measurements;
these should correspond to observations that occurred at or very near a
minimum. Five minima in the $I$-band TASS photometry were identified:
TASS minima ${\rm HJD-2450000} = 740.5650$; 967.8671; 1056.6230;
1059.6140; 1068.5880.  Using these values in conjunction with the
minima determined during the five nights of observation at Rolling
Hills Observatory yields an improved ephemeris:
$$ \begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~} 2451463.5725 & {} + 0\fday272218 & {} \times E. \\
                   {} \pm 0.0004 & {} \pm 0\fday000004 \\
\end{array} $$
The quoted error was estimated by assuming that each of the TASS minima
had a standard error of 5 minutes.  A phase diagram is shown in
Figure~1. The light curve is fairly symmetric, with the primary minimum
being 0\fmm10 fainter than the secondary.  The secondary eclipse occurs
very close to phase 0.5.
}

\IBVSTack{
Michael Gutzwiller has searched through the TASS Mark III database to discover several dozen previously unknown variables.  His work was instrumental in pointing the author to this new variable.\\
Tom Droege is the founder and main driving force behind the TASS organization. Without his efforts there would be no TASS.   
}

\references

Bertin, E., Arnouts, S., 1996, {\it A\&AS}, {\bf 117}, 393

Gutzwiller, M., 1999, {``TASS Variables''}, \\ {\tt http://home.fuse.net/deepsky/TASS\_Variables.htm}

Richmond, M. W., Droege, T. F., Gombert, G., Gutzwiller, M., Henden, A. A., Albertson, C., Beser, N., Molhant, N., Johnson, H., 2000, {\it PASP}, {\bf 112}, 397

\end{document}
