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\IBVShead{5768}{4 May 2007}

\IBVStitletl{13 New Eclipsing Binaries with Additional}{ Variability in the ASAS Catalogue}

\IBVSauth{Pilecki, B.; Szczygie{\l}, D.M.} 

\IBVSinsto{Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Al.Ujazdowskie 4, 00-478
Warszawa, Poland, \\ e-mail: pilecki@astrouw.edu.pl, dszczyg@astrouw.edu.pl}

\SIMBADobj{V393 Sco}
\SIMBADobj{IV Lib}
\SIMBADobj{HD 302992}
\SIMBADobj{FR Sct}
\SIMBADobj{ALS 1135}
\SIMBADobj{TYC 9253-1392-1}
\SIMBADobj{BD-19 3931}
\SIMBADobj{TYC 9219-3329-1}
\SIMBADobj{CD-52 646}
\SIMBADobj{V395 Sgr}
\SIMBADobj{SV* BV 729}
\SIMBADobj{TYC 9050-298-1}

\IBVSabs{We present 13 new ASAS eclipsing binaries that exhibit additional periodic}
\IBVSabs{variability due to pulsations, eclipses with another period or spots.}
\IBVSabs{All contact and semi-detached binaries from the ASAS Catalogue were}
\IBVSabs{investigated.}

\begintext

The All Sky Automated Survey has already collected over 6 years of observations for the
majority of the sky (declinations $< +28\deg$), down to 14th magnitude. Semi-automatic
classification of variable stars resulted in the ASAS Catalogue of Variable Stars --- ACVS
(Pojma\'nski et al., 2006).  For details on the classification procedure see Pojma\'nski
(2002). A big part of ACVS consists of eclipsing binaries, among them are 5384 contact (EC),
2957 semidetached (ESD), and 2758 detached (ED) binaries. Recently a sub-sample of these has
been searched for period changes (Pilecki et al.\ 2007). During this investigation a side
analysis was performed which resulted in 16 (13 new) binaries which are suspect to additional
periodic behaviour of various origin; secondary variability may be due to spots, pulsations,
or second eclipsing binary in the system. Two of them, namely 115143-6253.2 and 164802-6715.2,
were found by D. Fabrycky, who pointed out (private comm.)\ that these stars showed eclipses
with another period.

The search for second periodicity was performed on residual lightcurves of all EC and ESD
binaries in ACVS (8,341 objects). After detecting an additional frequency for each object, all
the lightcurves were sorted by amplitude of the frequency and the ones with a significant
signal strength were inspected visually. This left us with 14 objects for which (together with
additional two stars mentioned above) a more detailed analysis was performed.

In order to separate the lightcurves for both kinds of variability we applied an iterative
method. In the first step the best fitting model of an eclipsing binary $M_1$ with orbital
period $P_1$ was removed from the original lightcurve. Then we analysed the residual
lightcurve in the search for secondary period $P_2$, which was used to construct the model
$M_2$ of additional variability. This model was then subtracted from the original lightcurve
and the residual lightcurve was again investigated to find a refined $M_1$. After subtracting
the new $M_1$ from the raw lightcurve, the new $M_2$ was once again determined. In some cases
one more step was performed to get a better model $M_1$.

Using residual lightcurves of models $M_1$ and $M_2$, variability was then
classified with periods $P_1$ and $P_2$ using the same procedure as in Pojma\'nski
(2002). However, all pulsating types were combined into one PULS category and, when it was
plausible, we changed automatic classification to `Spot' type.

\IBVSfig{14cm}{5768-f1.eps}{Two examples of double periodic behaviour. Original and residual
lightcurves are showed. Plots of the rest of the light curves are given electronically}
\IBVSfigKey{5768-f1.eps}{V393 Sco ; ASAS 103209-5905.7}{light curve}

\vspace{-12pt}
In Table 1 we listed both periods ($P_1$ and $P_2$), separate variability types
and the possible degree of blending (0 for none, 1 for small and 2 for large) listed in two
columns, designated by I and A{}. The first one (I) is the degree of blending evaluated
subjectively by an examination of higher resolution images from Digitized Sky Survey, whereas
A is the result of brightness comparison in different apertures of ASAS photometry. The radius
of the smallest aperture is 1 pixel and for the largest 3 pixels, so two faint stars close to
each other are separated when using small aperture and counted as one object when using a
large aperture, significantly increasing the brightness. Some additional information from the
SIMBAD database is given (if available) such as an other identifier, spectral type, and
whether the star might be an X-ray source (X).

Two stars were found in the WDS catalogue of astrometric doubles and multiples (Mason et al.,
2001). 234520-3100.5 was identified as a double star (11.58 mag + 11.94 mag) with a separation
of 1\arcs\ and 125523-7322.2 (10.6 mag + 11.5 mag) with a separation of 2.4\arcs.

In the course of this analysis 7 out of 13 objects turned out to be double eclipsing binaries
(ie.\ quadruples that consist of two doubles), whereas one exhibits additional pulsations.  
For one object we have not been able to determine which of the above two scenarios is more
probable. There are also 2 stars whose secondary periods have values close to that of primary
periods. This kind of behaviour is believed to be due to spots on one of the binary's
components. For the remaining two we have no plausible explanation.

\begin{table}
\begin{center}
{Table 1. ASAS eclipsing binaries exhibiting additional periodic variability}
\vskip 2mm
\begin{footnotesize}
\begin{tabular}{@{}crrlrlcll@{}}
\hline
  ASAS ID      &$V_{\rm max}$&\multicolumn1c{$P_1$}& Type& \multicolumn1c{$P_2$} & Type     
&Blend& Other   & Other ID  \\
 (RA-DEC) &  [mag] & \multicolumn1c{[days]} & & \multicolumn1c{[days]} & & I A & data &  \\
\hline
 174848-3503.5 
&   7.45  & 7.71215\phantom{0} & ESD & 253.4\phantom{00000}& PULS   & 0 0 & B3III & V393 Sco \\
 103209-5905.7 &  10.50  & 0.953307    & ESD &  1.110270     & ESD = ED & 2 1 & F & HD 302992   \\ 
 153713-1820.1 
\IBVSefigure{5768-f2.eps}
\IBVSecomment{Light curve of 153713-1820.1}
\IBVSfigKey{5768-f2.eps}{ASAS 153713-1820.1}{light curve}
&   8.38  & 6.86170\phantom{0} & ESD &   6.87811\phantom{0}& Spot   & 0 0 & K1III, X & IV Lib  \\ 
 172738-3808.6 
\IBVSefigure{5768-f3.eps}
\IBVSecomment{Light curve of 172738-3808.6}
\IBVSfigKey{5768-f3.eps}{ASAS 172738-3808.6}{light curve}
&  11.56  & 0.378603    & ESD & 0.423350     & EC/PULS & 2 2 & -----     &   -----     \\
 115143-6253.2
\IBVSefigure{5768-f4.eps}
\IBVSecomment{Light curve of 115143-6253.2}
\IBVSfigKey{5768-f4.eps}{ASAS 115143-6253.2}{light curve}
&   9.93  & 0.876114 & ESD    & 19.11($\times 2$)     & ED     & 2 1 & B5  & BV 729  \\
 164802-6715.2 
\IBVSefigure{5768-f5.eps}
\IBVSecomment{Light curve of 164802-6715.2}
\IBVSfigKey{5768-f5.eps}{ASAS 164802-6715.2}{light curve}
&  10.43  & 0.422509 & EC = ESD & 1.593378      & ED/ESD & 2 2 & ----- & TYC 9050-298-1 \\
 144001-1959.5 
\IBVSefigure{5768-f6.eps}
\IBVSecomment{Light curve of 144001-1959.5}
\IBVSfigKey{5768-f6.eps}{ASAS 144001-1959.5}{light curve}
&  10.00  & 0.354445  & EC = ESD& 0.334349      & ESD/EC & 0 1 & G0, X      & BD-19 3931  \\
 031509-5144.2 
\IBVSefigure{5768-f7.eps}
\IBVSecomment{Light curve of 031509-5144.2}
\IBVSfigKey{5768-f7.eps}{ASAS 031509-5144.2}{light curve}
&9.61& 21.4105\phantom{00}& EC/ESD & 21.1067\phantom{00} & Spot   & 1 0 & K1, X & CD-52 646 \\
 125523-7322.2 
\IBVSefigure{5768-f8.eps}
\IBVSecomment{Light curve of 125523-7322.2}
\IBVSfigKey{5768-f8.eps}{ASAS 125523-7322.2}{light curve}
& 9.74 & 206.1\phantom{00000} & EC  & 250.2\phantom{00000} & ? & 1 0 & ----- & TYC 9253-1392-1 \\
 103513-1206.5 
\IBVSefigure{5768-f9.eps}
\IBVSecomment{Light curve of 103513-1206.5}
\IBVSfigKey{5768-f9.eps}{ASAS 103513-1206.5}{light curve}
&  11.43  & 0.384647    & EC  & 0.353901      & ESD/EC & 0 0 & -----     &   -----     \\
 131055-4844.0 
\IBVSefigure{5768-f10.eps}
\IBVSecomment{Light curve of 131055-4844.0}
\IBVSfigKey{5768-f10.eps}{ASAS 131055-4844.0}{light curve}
&  10.80  & 7.06562\phantom{0} & EC? & 3.537421      & Spots? & 2 0 & -----, X & ----- \\
 103308-7133.8 
\IBVSefigure{5768-f11.eps}
\IBVSecomment{Light curve of 103308-7133.8}
\IBVSfigKey{5768-f11.eps}{ASAS 103308-7133.8}{light curve}
&  10.58  & 0.816190    & EC  & 0.388607      & ESD=ED & 0 0 & -----     & TYC 9219-3329-1 \\
 190004-2741.4 
\IBVSefigure{5768-f12.eps}
\IBVSecomment{Light curve of 190004-2741.4}
\IBVSfigKey{5768-f12.eps}{ASAS 190004-2741.4}{light curve}
&  12.24  & 0.439555    & EC  & 0.537903      & ESD/EC & 2 2 & -----     & V395 Sgr    \\
\hline
\end{tabular}
\end{footnotesize}
\end{center}
\end{table}

Three stars listed in Table 2 were independently found and recently analysed by Pigulski \&
Michalska (2007a, 2007b). They found FR Sct to be a triple VV Cephei-type system,
234520-3100.5 to show additional $\delta$ Scuti behaviour, and 084350-4607.2 to exhibit
$\beta$ Cephei-type variations. For them we quote only our second variability type and an
estimation of a degree of blending.

\begin{table}
\begin{center}
\centerline{Table 2. Objects examined independently by Pigulski \& Michalska}
\vskip 2mm
\begin{footnotesize}
\begin{tabular}{clcl}
\hline
  ASAS ID      & 2nd type &Blend& Other ID  \\
 (RA-DEC)      &          & I A &           \\
\hline
 182323-1240.9 &   PULS   & 2 0 & FR Sct    \\ 
 234520-3100.5 &  EC/PULS & 0 0 & -----     \\
 084350-4607.2 &  ESD/EC  & 2 2 & ALS 1135  \\
\hline
\end{tabular}
\end{footnotesize}
\end{center}
\end{table}

One star, namely 131055-4844.0, has a secondary period value close to (but not the same as)
half the value of the primary variation period. Moreover, a residual lightcurve of the second
variability has an eclipsing-like shape with two minima of different depth. This cautions,
that the primary period may be two times smaller and the primary variability may be due to
pulsations rather than eclipses.

\textbf{Acknowledgements.} We would like to thank D. Fabrycky for pointing out two stars with
additional periodic behaviour. Our analysis made use of the Digitized Sky Survey images made
available by the STScI{}. This work was supported by the MNiSW grant N203 007 31/1328.

\references

Mason, B.D., et al. 2001, {\it AJ}, {\bf 122}, 3466

Pigulski, A., Michalska, G., 2007a, {\it IBVS}, No.\ 5757

Pigulski, A., Michalska, G., 2007b, {\it AcA}, {\bf 57}, 61

Pilecki, B., Fabrycky, D., Poleski, R., 2007, astro-ph/0703705, Accepted to MNRAS

Pojma\'nski, G.,  2002, {\it AcA}, {\bf 52}, 397

Pojma\'nski, G., Maciejewski, G., Pilecki, B., Szczygiel, D.,  2006, {\it VizieR On-line Data Catalog II/264}, \BIBCODE{2006yCat.2264....0P} 

\endreferences

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