\documentstyle[twoside, epsfig]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{5859}{7 November 2008}

\IBVStitle{Multicolour CCD Photometry of Three RR\lowercase{ab} Stars}

\IBVSauth{Kun,~E.$^1$; S\'odor,~\'A.$^2$; Jurcsik,~J.$^2$; Hurta,~Zs.$^{3,4}$; Nagy,~I.$^3$; K\H ov\'ari,~Zs.$^2$;\\ Posztob\'anyi,~K.$^5$; Kov\'acs,~G.$^3$; Vida,~K.$^{3,4}$; Belucz,~B.$^3$}

\IBVSinst{University of Szeged, Dept.\ of Exp.\ Physics and Astron.\ Obs.,
          H-6720 Szeged, D\'om t\'er 9, Hungary}
\IBVSinst{Konkoly Observatory of the Hungarian Academy of Sciences, P.O.\ Box 67,
          H-1525 Budapest, Hungary; e-mail: name@konkoly.hu}
\IBVSinst{E\"otv\"os Lor\'and University, Department of Astronomy, P.O.\ Box 32,
          H-1518 Budapest, Hungary}
\IBVSinst{Visiting Astronomer, Konkoly Observatory of the Hungarian Academy of Sciences}
\IBVSinst{AEKI, KFKI Atomic Energy Research Institute, Thermohydraulic Department, H--1525 Budapest 114, PO Box 49, Hungary}

\SIMBADobj{CN Lyr}
\SIMBADobj{CG Peg}
\SIMBADobj{FH Vul}
\GCVSobj{CN Lyr}
\GCVSobj{CG Peg}
\GCVSobj{FH Vul}

\IBVStyp{   RRab   }
\IBVSkey{Variable stars, RR Lyrae stars}
\IBVSabs{Multicolour CCD observations of three RRab stars are presented.}

\begintext
% \vspace*{-5mm}

The fifth set of CCD light curves of monoperiodic fundamental mode RR Lyrae stars based on the observations of the 60\,cm automatic telescope of Konkoly Observatory, Sv\'abhegy, Budapest is published. The equipment and data reduction procedure were the same as described in Jurcsik et al. (2008).

Observations of CN~Lyr, CG~Peg and FH~Vul are presented here. Photometric data on these three variables were published previously by Oosterhoff (1960), Sturch (1966), Stepien (1972), Penston (1973), Schmidt \& Reiswig (1993), and Castellani et al. (1998). The light curve of FH~Vul was considered as a stable one and was used as a calibrator object for deriving the [Fe/H]\,--\,Fourier parameter relation by Jurcsik \& Kov\'acs (1996). Though no indication of light curve variation of any of these variables was evident, small amplitude Blazhko-modulation (e.g. found in Jurcsik et al. 2005, 2006) could not be excluded from the earlier observations.

Based on the accuracy and time coverage of our data we conclude that the light curves of these 3 stars are stable, indeed. There is no apparent light curve modulation with amplitude larger than $0.01-0.02$ mag in the maximum brightness of any of the stars.


\begin{table}[!h]
\centerline{{\bf Table~1.} Log of observations}
\footnotesize
\begin{center}
\begin{tabular}{cccccccc}
\hline
Star & \multicolumn{4}{c}{Comparison}                   &  Observation period & \multicolumn{2}{l}{\hskip8mm No. of}  \\
% \hline
    & GSC 2.3.2 & RA(2000) & DEC(2000) & $V$ [mag]\,$^*$ &  JD 2400000 +          &   nights      & $B / V / I_C$ data\\
\hline
CN Lyr  & N24S000237 & 18 41 42.87 & +28 44 57.1 & 11.90 & 54642 -- 54701 & 8  & 267 / 271 / 242 \\
CG Peg  & N2MC000574 & 24 41 01.91 & +24 44 16.6 & 13.16 & 54656 -- 54751 & 11 & 333 / 292 / 295 \\
FH Vul  & N2P8000417 & 20 40 29.43 & +22 12 24.3 & 12.82 & 54633 -- 54741 & 8  & 218 / 234 / 227 \\
\hline
\multicolumn{7}{l}{\footnotesize{$^*$ $V$ magnitudes of the comparison stars are from GSC 2.3.2}}\\
\end{tabular}
\end{center}
\end{table}

The photometric data are available electronically from the IBVS website (5859-t5.txt\,--\,5859-t16.txt). The tables list the relative $BVI_{\rm C}$ magnitude and relative $B-V$, $V-I_{\rm C}$ colour time series with respect to the comparison stars listed in Table~1. The brightnesses of the comparison stars remained constant during the observations. The $r.m.s.$ scatter of their relative magnitudes measured to several check stars are between 0.005 and 0.015\,mag. For comparison, the $r.m.s.$ scatter of the Fourier fits to the $B, V, I_C$ light curves of CN~Lyr, CG~Peg, and FH~Vul are 0.007/0.006/0.005, 0.010/0.007/0.006, and 0.016/0.009/0.009 mag, respectively.

The $V$ light curves and the colour curves of the three stars are plotted in Figs.~$1-3$.

Normal maximum timings and Fourier parameters of the $V$ light curves of CN~Lyr, CG~Peg, and FH~Vul are listed in Table~2, and Table 3, respectively. Table 4 compares the photometric metallicities calculated from the $V$ light curves of the variables according to Eq.~3 of Jurcsik \& Kov\'acs (1996) to the results of spectroscopic metallicity measurements.



\IBVSedata{5859-t5.txt}
\IBVSdataKey{5859-t5.txt}{CN Lyr}{photometry}
\IBVSedata{5859-t6.txt}
\IBVSdataKey{5859-t6.txt}{CN Lyr}{photometry}
\IBVSedata{5859-t7.txt}
\IBVSdataKey{5859-t7.txt}{CN Lyr}{photometry}
\IBVSedata{5859-t8.txt}
\IBVSdataKey{5859-t8.txt}{CN Lyr}{photometry}
\IBVSedata{5859-t9.txt}
\IBVSdataKey{5859-t9.txt}{CG Peg}{photometry}
\IBVSedata{5859-t10.txt}
\IBVSdataKey{5859-t10.txt}{CG Peg}{photometry}
\IBVSedata{5859-t11.txt}
\IBVSdataKey{5859-t11.txt}{CG Peg}{photometry}
\IBVSedata{5859-t12.txt}
\IBVSdataKey{5859-t12.txt}{CG Peg}{photometry}
\IBVSedata{5859-t13.txt}
\IBVSdataKey{5859-t13.txt}{FH Vul}{photometry}
\IBVSedata{5859-t14.txt}
\IBVSdataKey{5859-t14.txt}{FH Vul}{photometry}
\IBVSedata{5859-t15.txt}
\IBVSdataKey{5859-t15.txt}{FH Vul}{photometry}
\IBVSedata{5859-t16.txt}
\IBVSdataKey{5859-t16.txt}{FH Vul}{photometry}

%\newpage

\IBVSfig{5.93cm}{5859-f1.eps}{Differential $V$, $B-V$ and $V-I_{\rm C}$ light and colour curves of CN~Lyr.}
\IBVSfigKey{5859-f1.eps}{CN Lyr}{light curve}

\IBVSfig{8.2cm}{5859-f2.eps}{Differential $V$, $B-V$ and $V-I_{\rm C}$ light and colour curves of CG~Peg.}
\IBVSfigKey{5859-f2.eps}{CG Peg}{light curve}

\pagebreak

\begin{table}[!ht]
\centerline{{\bf Table~2.} Normal maximum timings of the $V$ light curves.}
\vspace*{-2.mm}
\begin{center}
\begin{tabular}{cccc}
\hline
Star & $T_{\rm max} - 2400000$ & Star & $T_{\rm max} - 2400000$ \\
     & [HJD] & &[HJD]  \\
\hline
CN Lyr & 54671.3549 & FH Vul & 54640.5113 \\
CG Peg & 54703.8288 & FH Vul & 54717.5400 \\
% CN Lyr & 54648.522162 & FH Vul & 54640.507436 \\
% CG Peg & 54701.495274 & FH Vul & 54694.428908 \\
\hline
\end{tabular}
\end{center}
\end{table}

% \vspace*{-5mm}

\IBVSfig{12.5cm}{5859-f3.eps}{Differential $V$, $B-V$ and $V-I_{\rm C}$ light and colour curves of FH~Vul.}
\IBVSfigKey{5859-f3.eps}{FH VUl}{light curve}

\pagebreak


\begin{table}[h!]
\centerline{{\bf Table~3.} Fourier parameters of the $V$ light curves.}
\vspace*{-2.mm}
\begin{center}
\normalsize
\begin{tabular}{c@{\hspace{8pt}}l@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}}c@{\hspace{8pt}
}c@{\hspace{8pt}}c}
\hline
Star & \hskip6mm $P$ & $A_1$    & $R_{21}$ & $R_{31}$ & $R_{41}$ & $R_{51}$ & $\phi_{21}$\,$^*$ & $\phi_{31}$\,$^*$ & $\phi_{41}$\,$^*$ & $\phi_{51}$\,$^*$ \\
     & \hskip6mm [d] & [mag] &     &     &     &     & [rad]       & [rad]       & [rad]       & [rad]     \\
\hline
CN Lyr & 0.41138232$^{**}$ & 0.205 & 0.439 & 0.224 & 0.073 & 0.024 & 2.616 & 5.523 & 2.274 & 5.679 \\
CG Peg & 0.46713820$^{**}$ & 0.312 & 0.542 & 0.327 & 0.186 & 0.099 & 2.574 & 5.435 & 2.035 & 4.742 \\
FH Vul & 0.405413(4) & 0.440 & 0.516 & 0.373 & 0.239 & 0.170 & 2.256 & 4.930 & 1.227 & 3.927 \\
\hline
\multicolumn{10}{l}{\footnotesize{$^*$\hskip2mm Phase differences are given according to sine term decomposition.}} \\
\multicolumn{10}{l}{\footnotesize{$^{**}$ GCVS period.}} \\
\end{tabular}
\end{center}
\end{table}


\begin{table}[h!]
\centerline{{\bf Table~4.} Spectroscopic and photometric [Fe/H] values.}
\vspace*{-2.mm}
\begin{center}
\begin{tabular}{c@{\hspace{26pt}}c@{\hspace{26pt}}cl}
\hline
Star&[Fe/H]$_{\rm phot}$ & [Fe/H]$_{\rm spect}$\,$^a$ & ref.\\
\hline
CN Lyr &  $+0.17$ & $-0.05$ &  Layden (1994)\\
CG Peg &  $-0.25$ & $-0.26$ &  Layden (1994)\\
FH Vul &  $-0.59$ & $-0.61$ &  Layden (1994)\\
\hline
\multicolumn{4}{l}{\small $a$: Spectroscopic metallicities are transformed to the [Fe/H] scale} \\
\multicolumn{4}{l}{\small \hskip4mm used for the photometric metallicities according to Eq. 3 and Eq. 2}\\
\multicolumn{4}{l}{\small \hskip4mm of Jurcsik (1995) and Jurcsik \& Kov\'acs (1996), respectively.}\\
% \multicolumn{4}{l}{\small \,\,\, .}
\end{tabular}
\end{center}
\end{table}

% \vskip 2mm
We thank B\'ela Szeidl for his many helpful comments on this work. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. The financial support of OTKA grants T-048961, and T-068626 is acknowledged. ZsK is a grantee of the Bolyai J\'anos scholarship of the HAS.

\references

Castellani, V., di Paolantonio, A., Piersimoni, A. M., Ripepi, V. 1998, {\it A\&A}, {\bf 333}, 918

Jurcsik, J. 1995, {\it Acta Astronomica}, {\bf 45}, 653

Jurcsik,~J., Kov\'acs,~G. 1996, {\it A\&A}, {\bf 312}, 111

Jurcsik,~J., S\'odor,~\'A, V\'aradi,~M., Szeidl,~B., Washuettl,~A., et al. 2005, {\it A\&A}, {\bf 430}, 1049

Jurcsik,~J., Szeidl,~B., S\'odor,~\'A, D\'ek\'any,~I., Hurta,~Zs., et al. 2006, {\it AJ}, {\bf 132}, 61

Jurcsik,~J., S\'odor,~\'A., Hurta,~Zs., K\H ov\'ari,~Zs., Vida,~K. et al. 2008, {\it IBVS}, {\bf 5844}

Layden, A. 1994,  {\it AJ}, {\bf 108}, 1016

Oosterhoff, P. T. 1960, {\it BAN}, {\bf 15}, 199

Penston, M. J. 1973, {\it MNRAS}, {\bf 164}, 133

Schmidt, E. G., Reiswig, D. E. 1993, {\it AJ}, {\bf 106}, 2429

Stepien, K. 1972, {\it AcA}, {\bf 22}, 175

Sturch, C. 1966, {\it ApJ}, {\bf 143}, 774

\endreferences

\vskip20pt
\IBVSerratum{5793}
\vskip6pt
In IBVS 5793 Table 3 the 2nd line on the maximum timings of BK Cas gives erroneous $T_{\mathrm max}$ value. This line should correctly be: ``BK Cas {\bf 54321.1434} normal''.
% ``BK Cas \hskip5mm 54321.1434 \hskip5mm normal''

\end{document}
