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\input ibvs2.sty

\begin{document}

\IBVShead{5431}{17 June 2003}

\IBVStitle{Four New Short-Period Eclipsing Binary Stars}

\IBVSauth{Maciejewski, Gracjan; Czart, Krzysztof; Niedzielski, Andrzej; Karska, Agata}

\IBVSinsto{Centrum Astronomii, Uniwersytet Miko{\l}aja Kopernika, Pl-87100 Toru\'n, Poland;\\ e-mail: {\tt gm,kczart,aniedzi,agata@astri.uni.torun.pl}}


\SIMBADobjAlias{HD 65498}{BD+42 1795}
\SIMBADobjAlias{HD 67894}{BD+43 1775}
\SIMBADobjAlias{BD+20 2890}{GSC 01473-01049}
\SIMBADobj{GSC 03472-00641}
\IBVStyp{ E }
\IBVSkey{E - photometry}
\IBVSkey{eclipsing binaries - photometry}

\IBVSabs{Four new eclipsing binary stars are identified: HD 65498,}
\IBVSabs{HD 67894, BD+20 2890 and GSC 03472-00641. For all of them new}
\IBVSabs{spectral types and luminosity classes are presented in addition to}
\IBVSabs{ephemerides and periods.}

\begintext

Four new eclipsing binary stars were discovered by the
Semi-Automatic Variability Search\footnotemark. Basic data for new
variables are collected in Table 1. The observations were made at
the Astronomical Observatory of the Miko{\l}aj Kopernik University
in Piwnice with the semi-automatic CCD camera equipped with a
135/2.8 telephoto lens. As a detector SBIG ST-7 CCD camera with
KAF 400 chip was used. All brightness measurements were made in
near-Johnson $V$ filter. No transformation to a standard system
was done. All given magnitudes are determined against comparison
stars, which estimated $V$ magnitudes were calculated from TYCHO-2
Catalogue (H{\o}g et al., 2000) with formula:
$V=V_{T}-0.090(B_{T}-V_{T})$. Times of minima were determined with
the Kwee-van Woerden method (Kwee, van Woerden, 1956). Periods were
found with the ANOVA method of Schwarzenberg-Czerny (1996). All
four stars were also observed with the 0.9m Schmidt-Cassegrain
telescope equipped with the Richardson spectrograph and Wright CCD
camera. With 600 gr/mm grating we obtained spectra between 3500
and 5500 {\AA} with 2 {\AA}/pix reciprocal dispersion. These
spectra, after standard reduction performed with IRAF package were
used for spectral classification.

\footnotetext{For further information on SAVS see {\tt
http://www.astri.uni.torun.pl/\~{}gm/SAVS/}. }

{\small
\begin{center}
{\normalsize {\bf Table 1.} Basic data for new eclipsing
variables} \vskip 2mm
\begin{tabular}{lccll}
\hline
Star name & R.A. (J2000) & DEC. (J2000) & Comp. stars & Type\\
\hline
HD 65498        & 08\hr00\mm45\fsec955 & +42\deg10\arcm33\farcs07 & HD 66174        & EA \\
                &                      &                          & GSC 02976-00001 &    \\
HD 67894        & 08\hr11\mm53\fsec503 & +42\deg54\arcm36\farcs20 & HD 67808        & EB: \\
                &                      &                          & HD 68195        &     \\
BD+20\deg 2890  & 13\hr53\mm53\fsec848 & +20\deg09\arcm43\farcs18 & HD 120831       & EW \\
                &                      &                          & BD+20\deg 2887  &    \\
GSC 03472-00641 & 14\hr21\mm44\fsec058 & +46\deg41\arcm59\farcs37 & BD+47\deg 2136  & EW \\
                &                      &                          & BD+47\deg 2141  &    \\
\hline
\end{tabular}
\end{center}
}

HD 65498 = BD+42\deg 1795 = GSC 02976-01077 is recorded in Simbad
database as a star of $V$=9\fmm75 with $(B-V)$=0\fmm48 and
spectral type G. Our observations collected during 13 nights
between February 23, 2003 and April 4, 2003 and consisting of 232
data points (Figure 1) show that HD 65498 is an algol-type
variable (EA) with period of about 31.5 hour. In the primary
minimum the observed brightness drops by $\Delta$$m_{V}$=0\fmm43.
The secondary minimum is 0\fmm05 shallower and appears exactly in
phase 0.5 indicating circular orbit of the system. Both minima are
of equal duration and last for about 4 hours. Coordinates of HD
65498 coincide with those of an infra-red source 2MASS
J0800459+421033. A preliminary ephemeris for the primary minimum
is:
\begin{equation}
\begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~}2452704.48836 & {} + 1\fday31324 & {} \times E.  \\
\pm 0.00054 & {} \pm 0.00006 &  \\
\end{array}
\end{equation}
%
Our spectrum of HD 65498 shows features characteristic for a F5V
star (see Figure 5).

\IBVSfig{9cm}{5431-f1.eps}{CCD light curve of HD 65498}
%%\IBVSfigKey{5431-f1.eps}{HD 65498}{light curve}

Variability of HD 67894 = BD+43\deg 1775 = GSC 02979-02218 was
discovered during 23~nights between October 23, 2002 and April 10,
2002. 278 data points were collected in total. HD 67894 has
$V$=9\fmm98 and $(B-V)$=0\fmm40, and is classified as a star of
spectral type of G0 in Simbad. As it is seen in Figure 2, the
difference between minima is considerable. The depth of the
primary minimum is $\Delta$$m_{V}$=0\fmm28 and an amplitude of the
secondary minimum is 0\fmm18. Therefore, despite of a short period
and a late spectral type, we classified the system basing on the
light-curve morphology as an eclipsing variable of $\beta$ Lyrae
type. Due to positions coincidence we identify HD 67894 with the
IR source observed within 2MASS survey - 2MASS J0811535+425436. A
preliminary ephemeris is:
\begin{equation}
\begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~}2452722.47342 & {} + 0\fday378018 & {} \times E.  \\
\pm 0.00035 & {} \pm 0.000015 &  \\
\end{array}
\end{equation}
%
Basing on spectrum presented in Figure 5 we classify HD 67894 as a F3V star.

\IBVSfig{9cm}{5431-f2.eps}{CCD light curve of HD 67894}
%%\IBVSfigKey{5431-f2.eps}{HD 67894}{light curve}

\IBVSfig{9cm}{5431-f3.eps}{CCD light curve of BD+20\deg 2890}
%%\IBVSfigKey{5431-f3.eps}{BD +20 2890}{light curve}

BD+20\deg 2890 = GSC 01473-01049 was noted as a variable star with
an amplitude about 0\fmm2 by Oja (1985) during a photoelectric
$UBV$ photometry survey for stars located near the North Galactic
Pole. The $V$ magnitude for the star of interest is 10.4 and color
indices $(B-V)$=0\fmm38 and $(U-B)=-$0\fmm02 (Oja, 1985). Our
photometric data (Figure 3) show that BD+20\deg 2890 is an
eclipsing binary of W UMa type changing its brightness with an
amplitude in the primary minimum by $\Delta$$m_{V}$=0\fmm37 and
with a period of just over a half of a day. The secondary minimum
is 0\fmm07 brighter. Observations were performed during 14 nights
between April 21, 2003 and June 1, 2003. 309 single photometric
measurements were collected. In our data the object is blended
with its fainter companion located 20 arc seconds south. The
ephemeris of a primary minimum is given by formula:
\begin{equation}
\begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~}2452788.42371 & {} + 0\fday53158 & {} \times E.  \\
\pm 0.00025 & {} \pm 0.00002 &  \\
\end{array}
\end{equation}

Optical spectrum (Figure 5) allows us to assign the A9III spectral type to
BD+20\deg 2890.

~\\
~\\
GSC 03472-00641 is the last new variable presented in this paper.
Photometry from to TYCHO-2 Catalogue (H{\o}g et al. 2000) gives
$V$=11\fmm32 and $(B-V)$=0\fmm45. Our 214~data points collected
during 12 nights between April 19, 2003 and May 7, 2003 show that
GSC~03472-00641 is a W UMa system with a period of almost 8 hours.
The obtained light curve is presented in Figure 4. The primary and
secondary minima have an amplitude of $\Delta$$m_{V}$=0\fmm50 and
$\Delta$$m_{V}$=0\fmm39 respectively. Due to positions coincidence
we identify GSC 03472-00641 with the infra-red source 2MASS
J1421440+464159. A preliminary ephemeris for the primary minimum
is following:
\begin{equation}
\begin{array}{r@{}r@{}l}
{\rm Min.~I = HJD~}2452764.50965 & {} + 0\fday318618 & {} \times E.  \\
\pm 0.00030 & {} \pm 0.000081 &  \\
\end{array}
\end{equation}
%
Presented in Figure 5 spectrum of GSC 03472-00641 is most similar to G5III type.

\IBVSfig{9cm}{5431-f4.eps}{CCD light curve of GSC 03472-00641}
%%\IBVSfigKey{5431-f4.eps}{GSC 03472-00641}{light curve}

\textit{Acknowledgements:} This research made use of the SIMBAD
data base, operated by the CDS at Strasbourg, France. This paper
is based on observations collected at Piwnice observatory.

\clearpage

\IBVSfig{13.0cm}{5431-f5.eps}{Optical spectra of the program
stars in the blue. Positions of the most significant spectral
features are indicated}
%%\IBVSfigKey{5431-f5.eps}{HD 65498 ; HD 67894 ; BD+20 289;  03472-00641}{spectra}


\references

H{\o}g, E., Fabricius, C., Makarov, V. V.,  Urban, S., Corbin, T.,
Wycoff, G., Bastian, U., Schwekendiek, P., Wicenec, A., 2000, {\it
A\&A}, {\bf 355}, L27

Kwee, K. K., van Woerden, H., 1956, {\it Bull. Astr. Inst.
Netherlands}, {\bf 12}, No. 464, 327

Oja, T., 1985, {\it A\&AS}, {\bf 61}, 331

Schwarzenberg-Czerny, A., 1996, {\it ApJ}, {\bf 460}, L107

\endreferences

\vfill\eject

%From: IBVS 5725
\IBVSerratum{5431}

Geert Hoogeveen reported the following error:

\begin{table}[h!]
\begin{tabular}{c l l l}
\hline
IBVS No. & item & printed & correct \\
\hline
5431 & RA (BD +20\deg 2890)  & 13\hr53\mm53\fsec848 & 13\hr53\mm13\fsec848 \\
\hline
\end{tabular}
\end{table}

\end{document}
