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\IBVShead{4834}{27 January 2000}

\IBVStitletl{New Photoelectric Light Curves of AB Andromedae}

\IBVSauth{Parimucha, \v{S}tefan$^1$; Pribulla, Theodor$^1$; Va\v{n}ko, Martin$^2$}

\IBVSinst{Astronomical Institute of Slovak Academy of Sciences, 05960 Tatransk\'a Lomnica, Slovak Republic,\\ \indent email: {\tt parimuch@ta3.sk, pribulla@ta3.sk}}

\IBVSinst{Faculty of Science, Department of the Theoretical Physics and
Astronomy, University of P.J. \v{S}af\'arik,\\ \indent 040 01 Ko\v{s}ice, Slovak Republic, email {\tt vanko@ta3.sk}}

\SIMBADobjAlias{AB And}{SAO 73069}

\begintext

AB And (SAO 73069, BD\,+36\deg 5017), is a W UMa type eclipsing binary (sp.\ type G5+G5V, $P \approx 0.3318$ days, $V_{\rm max} \approx 9.7$). Since the discovery (Guthnick \& Prager 1927) the system is a frequent target of photometric observations (for references see Rovithis-Livaniou \& Rovithis 1981; Demircan et al.\ 1994). The system exhibits asymmetries in minima and deformations in the light curve during maxima, interpreted either by the presence of gaseous streams (Kalchaev \& Trutse, 1968) or by spot activity on the primary component (e.g.\ Bell et al.\ 1984). Observed orbital period changes are caused probably by combination of the mass transfer from the more to less massive component and the light time effect (see Kalimeris et al.\ 1994; Borkovits \& Heged\"{u}s 1996) or a period modulation due to the magnetic activity cycle of the active primary component (Demircan et al.\ 1994)

\begin{table}[b]
\begin{center}
\caption{Journal of photometric observations}
\begin{tabular} {lcccc}
\hline
\lower6pt\hbox{Date} & HJD$_{\rm mean}$ & \lower6pt\hbox{Phases} & \lower6pt\hbox{Filters} & \lower6pt\hbox{Obs.} \\[-3pt]
 & 2400000\,+ & & & \\
\hline
1999 Aug.\ 19 & 51140.4070 & --- & UBV & SL$^*$ \\
1999 Sep.\ 4 & 51426.3828 & .927--.058 & UBV & SL \\
1999 Oct.\ 1 & 51453.4659 & .123--.980 & UBV & SL \\
1999 Dec.\ 8 & 51521.3016 & .782--.195 & BV & SL \\
1999 Dec.\ 21 & 51534.2575 & .839--.259 & BVR & SP \\
1999 Dec.\ 31 & 51544.3079 & --- & UBV & SP$^*$ \\
\hline
\multicolumn{5}{l}{$^*$ Measurement of comparison stars only}
\end{tabular}
\end{center}
\end{table}

Our U, B, V and R~photoelectric photometry was performed over 6 nights from August to December 1999 at the Star\'a Lesn\'a (SL) and Skalnat\'e Pleso (SP) Observatories of the Astronomical Institute of the Slovak Academy of Sciences. The 0.6~m Cassegrain telescope equipped with a single-channel pulse-counting photoelectric photometer was used. The journal of observations is listed in Table~1. For all observations a 10 second integration was chosen. SAO 73071 was used as a comparison star (Table~2). Its stability was checked on two nights (August 19 and December 31, 1999) with respect to six other stars. The comparison star was found to be stable within 0.01 mag. The international magnitude of comparison stars, calculated using the average of the published magnitudes of S6 (see~{\tt
 http://obswww.unige.ch/gcpd/gcpd.html }), are given in Table~2. Their mean errors are lower than 0.01 mag. Data reduction, the atmospheric extinction correction and transformation to the standard system were carried out in the usual way.

\begin{table}[t]
\begin{center}
\caption{Comparison stars and their magnitudes}
\begin{tabular}{ccccccc}
\hline
Star & SAO & BD & U & B & V & Sp.\\
\hline
S1 & 73115 & +35\deg 4988 & 9.54 & 9.48 & 8.93 & --- \\
S2 & 73071 & +36\deg5020 & 10.10 & 9.30 & 8.37 & K2 \\
CH & 73072 & +35\deg4972 & 11.48 & 10.92 & 10.05 & --- \\
S5 & 73093 & +34\deg4870 & 10.72 & 9.75 & 8.65 & --- \\
S6 & 72992 & +36\deg5003 & 9.03 & 7.92 & 6.76 & K0 \\
S7 & 73003 & +37\deg4769 & 9.09 & 8.87 & 8.21 & G5 \\
S8 & 73007 & +34\deg4847 & 8.67 & 7.55 & 6.39 & K0 \\
\hline
\multicolumn {7}{l}{Note: Star S8 was measured only on December 31, 1999}
\end{tabular}
\end{center}
\end{table}

We have calculated the times of minima separately for all filters using the Kwee and Van Woerden's method, parabola fit, sliding integration method, tracing paper and ``center of mass'' method which were described in detail by Ghedini (1982). The computer codes were kindly provided by Dr.\ R. Kom\v{z}\'{\i}k (1999). The average times of the primary (I) and secondary (II) minima and their probable errors found by these methods are given in Table~3.

\begin{table}[b]
\begin{center}
\caption{New times of minima and their standard errors ($\sigma$) of AB And}
\begin{tabular}{cccc|cccc}
\hline
HJD & \lower6pt\hbox{$\sigma$} & Min. & \lower6pt\hbox{Filter} & HJD & \lower6pt\hbox{$\sigma$} & Min. & \lower6pt\hbox{Filter}\\[-3pt]
2400000\,+ & & type & & 2400000\,+ & & type & \\
\hline
51426.38808 & 0.00014 & I & U & 51521.30847 & 0.00013 & I & B\\
51426.38763 & 0.00010 & I & B & 51521.30855 & 0.00004 & I & V\\
51426.38807 & 0.00007 & I & V & 51534.25069 & 0.00024 & I & B\\
51453.43763 & 0.00002 & II & U & 51534.25116 & 0.00018 & I & V\\
51453.43715 & 0.00001 & II & B & 51534.25222 & 0.00021 & I & R\\
51453.43705 & 0.00002 & II & V & & & & \\
\hline
\end{tabular}
\end{center}
\end{table}

Recent times of minima (Borkovits \& B\'{\i}r\'o, 1998; Kiss et al., 1999; Agerer \& H\"ubscher, 1999) together with average times of the minima from U,B,V and R passbands (Table~3) were used to determine the ephemeris suitable for future observations:
\begin{equation}
\begin{array}{r@{}r@{}r}
{\rm Min~(I) = HJD}~2451426.3875 & {}+0\fday3318925 & {} \times E. \\
 {} \pm5 & {} \pm 4 & \\
\end{array}
\end{equation}

All individual U, B and V observations are plotted in Fig.~1, using ephemeris (1). These data sets can be freely downloaded from address:

\centerline{{\tt http://www.ta3.sk/\~{}parimuch/archive.html}.}

\noindent The observed light curves were relatively stable during our observations except small variations in the depth of the primary minimum. The maximum at phase 0.25 was somewhat brighter than maximum at phase 0.75. The descending branch of the primary minimum in B passband observed on December, 21 is fainter than on the other nights.

\IBVSfig{10cm}{4834-f1.ps}{UBV light curves of AB And}

{\bf Acknowledgements:} This work was financially supported by VEGA grant
5038/99.

\references

Agerer, F., H\"ubscher, J., 1999, {\it Inf.\ Bull.\ Var.\ Stars}, No.\ 4711

Bell, S.A., Hilditch, R.W., King, D.J., 1984, {\it Mon.\ Not.\ R. Astron.\ Soc.}, {\bf 208}, 123

Borkovits, T., B\'{\i}r\'o, I.B., 1998, {\it Inf.\ Bull.\ Var.\ Stars.}, No.\ 4633

Borkovits, T., Heged\"us, T., 1996, {\it Astron.\ Astrophys.\ Suppl.\ Ser.}, {\bf 120}, 63

Demircan, O., Derman, E., Akalin, A. et al., 1994, {\it Mon.\ Not.\ R. Astron.\ Soc.}, {\bf 267}, 19

Ghedini, S., 1982, {\it Software for Photometric Astronomy}, Willmann-Bell Publ.\ Comp., Richmond

Guthnick, P., Prager, R., 1927, {\it Astron.\ Nachr.} {\bf 229}, 455

Kalchaev, K., Trutse, Y.L., 1968, {\it Variable Stars} {\bf 16}, 454

Kalimeris, A., Rovithis-Livaniou, H., Rovithis, P. et al., 1994,  {\it Astron.\ Astrophys.}, {\bf 291}, 765

Kiss, L.L., Kasz\'as, G., F\H{u}r\'esz, G. et al., 1999, {\it Inf.\ Bull.\ Var.\ Stars}, No.\ 4681

Kom\v{z}\'{\i}k, R., 1999, {\it private communication}

Rovithis-Livaniou, H., Rovithis P., 1981, {\it Astrophys.\ Space Sci.}, {\bf 76}, 465

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