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\IBVShead{5827}{7 May 2008}

\IBVStitletl{The Unconfirmed Eclipsing Nature of V348~A\lowercase{nd}}{ and Detection of Variability of HD~1438}

\IBVSauth{Zasche, P.$^1$; Svoboda, P.$^2$}

 \IBVSinst{Astronomical Institute, Faculty of Mathematics and Physics, Charles University Prague,
 V~Holesovickach~2, Praha~8, CZ-180 00 Czech Republic, e-mail: zasche@sirrah.troja.mff.cuni.cz}
 \IBVSinst{Private observatory, Vypustky 5, Brno, CZ-614 00 Czech Republic, e-mail: tribase.net@volny.cz}

\SIMBADobj{V348 And}
\SIMBADobj{HD 1438}


\begintext

\vspace*{-1cm}
\IBVSfoot{See {\tt http://integral.sci.muni.cz/cmunipack/}}

Precise photometric observations in standard Johnson-Cousins $BVR_c$ system of a neglected eclipsing binary
V348~And were carried out. All the measurements were obtained with the 34-mm refractor at the Private
observatory in Brno, using the SBIG ST-7XME CCD camera, and standard $B$, $V$ and $R_c$ filters by the
specification by Bessell (1990). The field of view (FOV) is about $2\deg \times 3\deg$, see Fig.~1 left, or
equivalently the angular pixel size is circa 14\arcs$\times$14\arcs. The observations come from the time span
from September 2007 to January 2008. The measurements were processed by the software {\sc C-Munipack}\IBVSfm, which is based on aperture photometry.

{\bf V348~And}. V348~And (= HD~1082 = HIP~1233, R.A.=00\hr 15\mm 18\sec,
Decl.=+44\deg 12\arcm 12\arcs, J2000.0, $V_{max} = 6.76$~mag, sp. B9V, according to Simbad
database) is one member of an astrometric binary A~1256 (the second component is less then 1\arcs~distant). The
observations obtained by the Hipparcos satellite (see Peryman \& ESA, 1997) indicate that the system is an
Algol-type eclipsing binary with its orbital period 5.5392~days (Kruszewski \& Semeniuk, 1999).

\IBVSfig{4.3cm}{5827-f1.eps}{Left: Identification frame for the stars. Right: PDM spectrum for Hipparcos and our
data. Also the different periods are plotted, the dashed one for 5.5392~days, the dash-dotted one for 6.06~days,
and the dotted one for 5.876~days.}
\IBVSfigKey{5827-f1.eps}{V348 And; HD 1438}{finding chart; periodogram}

\IBVSefigure{5827-f1a.eps}
\IBVSefigure{5827-f1b.eps}

\vspace*{-0.9cm}

Since its discovery as an eclipsing binary, the photometric variation has not been confirmed so far. The
Hipparcos observations of the two eclipses were the only ones, which were used for estimation of its light
elements. Regrettably, two minima observed by the Hipparcos satellite were not covered by the data sufficiently,
and only 8 points were used for estimation of these minima and its orbital period. According to a light curve
observed by Hipparcos, a predicted depth of the primary minimum of the star should be at least 0.13~mag and its
duration, $D$ more than 10~hours.

\IBVSfig{3.8cm}{5827-f2.eps}{The $B$, $V$ and $R_c$ light curves of V348~And. The shift $\pm$0.02~mag was applied
to $R_c$ and $B$ observations for the better clarity of the plot.}
\IBVSfigKey{5827-f2.eps}{V348 And}{light curve}

\vspace*{-0.8cm}


\IBVSedata{5827-t2.txt}
\IBVSdataKey{5827-t2.txt}{V348 And}{photometry}
\IBVSedata{5827-t3.txt}
\IBVSdataKey{5827-t3.txt}{V348 And}{photometry}
\IBVSedata{5827-t4.txt}
\IBVSdataKey{5827-t4.txt}{V348 And}{photometry}

Since September 2007, we have tried to reproduce the observations made by Hipparcos and using $B$, $V$ and $R_c$
filters, the star has been observed each clear night, until a phase light curve of the system was covered. The data files are available through the IBVS website as {\tt 5827-t1 $-$ 5827-t3.txt}.
HD~1185 (= HIP~1302, R.A.=00\hr 16\mm 22\sec,
Decl.=+43\deg 35\arcm 42\arcs, J2000.0, $V = 6.15$~mag, sp. A2V, according to Simbad database)
was used as a comparison star. As check stars to control the non-variability of this star we used the two following
stars HD~1448 and HD~1848 (see Fig.~1 left). No visible variabilities between these three stars were observed.
The final result is presented in Fig.~2, where the phase light curves in $B$, $V$ and $R_c$ filters are plotted
(the period 5.5392~days was used). We assumed that the minimum is detectable in all filters, and the light curve
is well covered at least in $R_c$ filter. Despite the scatter in each filter is circa 0.01~mag, there has not
been detected any observable photometric decrease. No minimum occurred during these 19 nights of observations
(more than 100~hours of observations in total). The PDM spectrum of our observations as well as of Hipparcos
data are plotted in Fig.~1 right. The result is that the orbital period of the system is different than presumed
on the basis of the Hipparcos data. Using the Hipparcos photometry, the period could be also a different one,
about 5.876 or 6.06~days (see the different minima in the PDM spectrum in Fig.~1~right and also the Hipparcos
light curves in Fig.~3). According to our new observations only, one is not able to judge whether
the orbital period is one of the suggested periods above or other one,
further photometric observations are still needed.

\IBVSfig{3.7cm}{5827-f3.eps}{The light curves of V348~And according to the Hipparcos data, the periods 5.5392,
5.876, and 6.06~days were used, respectively (from left to right).}
\IBVSfigKey{5827-f3.eps}{V348 And}{light curve}

\vspace*{-0.9cm}

{\bf HD~1438.} Another interesting result from the observing campaign of V348~And was the discovery of a photometric
variability of the star HD~1438 (= 26~And~A = HR~70 = HIP~1501,
R.A.=00\hr 18\mm 42\sec, Decl.=+43\deg 47\arcm 28\arcs, J2000.0,
$V = 6.11~$mag, sp. B8V, according to Simbad database). This star is about 30 arc minutes distant from V348~And.

The star is a primary component of an astrometric binary ADS~254, while the secondary (NSV~119) is about 4
magnitudes fainter and circa 6\farcs 2 distant. No changes in position angles of the two components have been
detected yet, so its possible orbital period is more than a thousand years. Baize (1962) mentioned a possible
long-term photometric variation of the secondary component. This variation is very slow (9.5~mag in 1845,
11.0~mag in 1913, 12.0~mag in 1934, 11.2~mag in 1959) and has not been explained so far. The spectral types were
estimated as B8V+F3V (according to Lindroos, 1985 and Wyatt, 2003), while Soderblom et al. (1991) presented the
spectral types B8V+dG0. Wyatt (2003) also derived a distance of the system about 212~pc, and investigated a
possible presence of a dust disc around the star. The submillimeter observations of the star indicate presence
of the disc with the temperature about 100~K with its total mass about 0.05~M$_\oplus$.

Our new photometric observations of the star from the same time epoch as V348~And indicate a shallow photometric
variability (see Fig.~4). Such a variability has an amplitude about only 0.015~mag, but despite this fact, it is
clearly visible in all $B$, $V$ and $R_c$ filters. Its period is about 1.6~days.

The nature of these variations could be explained by presence of a pulsating component in the system. Due to the
small telescope used (because of the high brightness of the stars), the components A and B could not be resolved
into separate stars and one is not able to judge, whether the variable component is the primary, or the
secondary one.

There could be also an alternative explanation of the variability. Almost sinusoidal oscillations could be also
described as ellipsoidal variations (close binary with tidally distorted stars, where the components are not
eclipsing each other). This solution was presented in Fig.~4 with the theoretical fit, while the parameters of
such fit are in Table~1. The final period of such variation is therefore doubled, about 3.16~days.

\IBVSfig{5.2cm}{5827-f4.eps}{The $B$, $V$ and $R_c$ light curves of HD~1438.}
\IBVSfigKey{5827-f4.eps}{HD 1438}{light curve}

\vspace*{-0.8cm}

\IBVSedata{5827-t5.txt}
\IBVSdataKey{5827-t5.txt}{HD 1438}{photometry}
\IBVSedata{5827-t6.txt}
\IBVSdataKey{5827-t6.txt}{HD 1438}{photometry}
\IBVSedata{5827-t7.txt}
\IBVSdataKey{5827-t7.txt}{HD 1438}{photometry}

Altogether there are 806 ($B$), 855 ($V$) and 1040 ($R_c$) observations, respectively. The data files are available through the IBVS website as {\tt 5827-t5 $-$ 5827-t7.txt}. For analysis the {\sc
Phoebe} programme (see e.g. Pr\v{s}a \& Zwitter, 2005), based on the Wilson-Devinney algorithm (Wilson \&
Devinney, 1971), was used. The value of the mass ratio was estimated via the ``q-search'' method, see Fig.~5 for
the sums of squares in the individual passbands as a function of the mass ratio. This value results in $q = 0.7
\pm 0.2$. The temperature of the primary was fixed at the typical value for B8V stars (11600~K, see Harmanec, 
1988). The amount of the third light was also computed, but its contribution to the total light is only very
small (below 1 percent) and such a low value is comparable with its respective error. The value of the third
light reveals that the variable is the primary component. Nevertheless, further observations are still needed,
especially the spectroscopic ones to confirm the nature of this system.

\IBVSfig{6cm}{5827-f5.eps}{Sum of squares as a function of the mass ratio.}
\IBVSfigKey{5827-f5.eps}{}{}

\vspace*{-1cm}

\begin{table}[!ht]
\small
\centerline{Table 1. The physical parameters of HD~1438.\footnote{$T_i$, $r_i$, and $L_i$ denote the
temperature, relative radius and luminosity for primary and secondary, respectively. $\Omega_i$ stands for the
modified Kopal potential, while $\Omega_{crit}^{Li}$ are the values of critical Kopal potentials in the
Lagrangian points. The "detached binary" mode was used for computing and the eccentricity was set to 0 (circular
orbit). The limb-darkening coefficients were interpolated from van~Hamme's tables (see van~Hamme, 1993). The
values of gravity brightening and bolometric albedo coefficients were set at their suggested values for
convective atmospheres (see Lucy, 1968), i.e. $G_1 = G_2 = 0.32$, $A_1 = A_2 = 0.5$. Also the synchronous
rotation was assumed for each star ($F_1 = F_2 = 1.0$).}}
\begin{center}
 \begin{tabular}{ c c c c c} \hline
 Parameter   &      Value              & &   Parameter   &   Value        \\
 \hline
 $HJD_0$     & 2454360.21 $\pm$ 0.05   & & $T_1 / T_2$   & $>$ 2.68      \\
 $P$ [day]   & 3.163063 $\pm$ 0.000002 & & $r_1 / r_2$   &  0.77           \\
 $i$ [deg]   & 38.8 $\pm$ 3.9          & & $\Omega_{crit}^{L1}$ & 3.24     \\
 $L_1 / L_2$ ($B$) & 63 $\pm$ 3        & & $\Omega_{crit}^{L2}$ & 2.84     \\
 $L_1 / L_2$ ($V$) & 343 $\pm$ 32      & & $\Omega_1$    & 4.18 $\pm$ 0.16 \\
 $L_1 / L_2$ ($R_c$) & 188 $\pm$  14   & & $\Omega_2$    & 3.11 $\pm$ 0.24 \\ \hline
 \end{tabular}
\end{center}
\end{table}

\noindent {\small {\bf Acknowledgements:} This investigation was supported by the Grant Agency of the Czech
Republic, grants No. 205/06/0304 and No. 205/06/0217. We also acknowledge the support from the Research Program
MSMT 0021620860 of the Ministry of Education. This research has made use of the SIMBAD database, operated at
CDS, Strasbourg, France, and of NASA's Astrophysics Data System Bibliographic Services.}

\vspace*{-0.2cm}

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\endreferences

\end{document}
