\documentclass[journal]{rmaa}

\def\uv{uvby-\beta}
\newcommand{\casitiny}{\fontsize{6}{7}\selectfont}


\title{$\lowercase{uvby}-\beta$ photoelectric photometry of Cepheid stars\altaffilmark{1}}


\author{
J.~H. Pe\~na,\altaffilmark{2} 
A. Arellano Ferro,\altaffilmark{2} 
R. Pe\~ na-Miller,\altaffilmark{3} 
M. \'Alvarez,\altaffilmark{4} 
Y. Rosas,\altaffilmark{5} 
H. Garc\'ia,\altaffilmark{6}\\ 
G. Mu\~noz,\altaffilmark{7} 
B. Vargas,\altaffilmark{8} 
J.~P. Sareyan,\altaffilmark{9} 
C. A. Guerrero,\altaffilmark{2} 
and A. Renter\'ia\altaffilmark{2}}

\altaffiltext{1}{Based on observations collected at the San Pedro M\'artir Observatory, Mexico.} 
\altaffiltext{2}{Instituto de Astronom\'ia, Universidad Nacional Aut\'o\-noma de M\'exico, Mexico.}
\altaffiltext{3}{Department of Mathematics, Imperial College London, UK.} 
\altaffiltext{4}{Observatorio Astron\'omico Nacional, UNAM, Mexico.}
\altaffiltext{5}{Centro de Radioastronom\'ia y Astrof\'isica, Universidad Nacional Aut\'onoma de M\'exico, Mexico.}
\altaffiltext{6}{Facultad de Ciencia, UNAN-Managua, Nicaragua.}
\altaffiltext{7}{ESIME, Instituto Polit\'ecnico Nacional, Mexico.}
\altaffiltext{8}{Instituto de Geof\'isica, Universidad Nacional Aut\'onoma de M\'exico, Mexico.} 
\altaffiltext{9}{Lesia, Observatoire de Paris-Meudon and Observatoire de la Cote d'Azur, France.}


\fulladdresses{
\item A. Arellano Ferro, C. A. Guerrero, J.~H. Pe\~na, \& A. Renter\'ia: Instituto de Astronom\'ia, Universidad Nacional Aut\'onoma de M\'exico, 
Apdo. Postal 70-264, M\'exico D. F. CP 04510, M\'exico (jhpena@astroscu.unam.mx).
\item M. \'Alvarez: Instituto de Astronom\'ia, Universidad Nacional Aut\'onoma de M\'exico, Ensenada. 
\item J. P. Sareyan: OCA, Department Gemini, Boulevard de l'Observatoire BP 4229, 06304 Nice Cedex 4, France.
\item R. Pe\~ na: Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.}


\shortauthor{Pe\~na et al.} 

\shorttitle{$\lowercase{uvby}-\beta$ photometry of Cepheids}

\listofauthors{J.~H.~Pe\~na, A.~Arellano~Ferro, R.~Pe\~na-Miller, M.~\'Alvarez, Y.~Rosas, H.~Garc\'ia, G.~Mu\~noz, B.~Vargas, J.~P.~Sareyan, 
C.~A.~Guerrero, \& A.~Renter\'ia}

\indexauthor{Pe\~na, J.~H.}
\indexauthor{Arellano~Ferro, A.}
\indexauthor{Pe\~na-Miller, R.}
\indexauthor{\'Alvarez, M.}
\indexauthor{Rosas, Y.}
\indexauthor{Garc\'ia, H.}
\indexauthor{Mu\~noz, G.}
\indexauthor{Vargas, B.}
\indexauthor{Sareyan, J.~P.}
\indexauthor{Guerrero, C.~A.}
\indexauthor{Renter\'ia, A.}


\ReceivedDate{2010 May 4}
\AcceptedDate{2010 June 10}
\SetYear{2010}


\resumen{Presentamos fotometr\'ia fotoel\'ectrica $\uv$ de 41 estrellas Cefeidas cl\'asicas. Se llev\'o a cabo una breve discusi\'on de los datos 
comparados con observaciones an\'alogas.}

\abstract{We present time-series $\uv$ photometry of 41 classical Cepheid stars. A brief discussion of a comparison between the 
present data and previous photometric observations is included.\vspace{0.25cm}}


\addkeyword{stars: variables: Cepheids}
\addkeyword{techniques: photometric}


\begin{document}


\maketitle


\section{INTRODUCTION}

The relevance of classical Cepheids in stellar astrophysics, both as distance indicators and for understanding stellar structure and 
pulsation, has been long acknowledged. The Str\"omgren ($\uv$) photometric system has proven to be very useful for the determination 
of fundamental physical quantities, such as reddening, effective temperature, gravity, and metallicity, for main sequence (Crawford 
1975), giant (Olsen 1984), and supergiant stars (Arellano Ferro \& Parrao 1989; Arellano Ferro \& Mantegazza 1996). Large compilations 
of $\uv$ photometry for Cepheids have been published previously (Feltz \& McNamara 1980; Eggen 1983, 1985; Meakes, Wallerstein, \& Opalko 1991; Arellano 
Ferro et al. 1998). While there are several stars in common to such studies, there remain numerous Cepheids that are still poorly observed. 
This paper presents new $\uv$ data for 41 Cepheids, for many of which there is very little or no previous Str\"omgren photometry.


\section{Observations}

The observations presented here were gathered over different seasons (see Table~1) from 1989 to 2009 at the San Pedro M\'artir Observatory 
in Baja California, Mexico. All data were obtained with the 1.5 m telescope equipped with a six-channel grating spectrophotometer. The 
observational procedure was the same in most seasons; each data point reported is the average of at least five 10 s integrations, and both 
sets of $uvby$ data and the narrow and wide bands that define the $\beta$ index were observed almost simultaneously. A single measurement 
of the sky with an integration time of 10 s was subtracted from the star measurements. On each night several standard stars were observed 
to carry out transformation into the standard system of Olsen (1983) and Crawford (1975, 1979). Photometric reductions were made using the 
NABAPHOT package (Arellano Ferro \& Parrao 1989) that corrects for atmospheric extinction, transforms the data into the standard system, 
and converts the sidereal time into Heliocentric Julian Day. Standard stars were taken from Gr\"onbech, Olsen, \& Stromgren (1976), Gr\"onbech 
\& Olsen (1977) and Olsen (1983), but some bright standard stars were also taken from the list published in the Astronomical Nautical Almanac.


%%%%%% TABLA 1

\begin{table*}[!t]
\vspace{0.1cm}
\centering
\caption{Log of the observing sessions} 
\label{log}
\setlength{\tabnotewidth}{0.78\textwidth}
%\setlength{\tabcolsep}{1.4\tabcolsep}
\tablecols{5}
%\small
\begin{tabular}{lcccl}
\toprule
\multicolumn{1}{c}{Epoch} & No. of stars  & Initial date    &  Final date      & \multicolumn{1}{c}{Observers} \\
      &               & year month day  &  year month day  &           \\
\midrule
1989 OctNov     & 16 &  1989 10 29 & 1989 11 07 & jhp, rpg\\
2005 MayJune    & ~4 &  2005 05 28 & 2005 06 31 & jhp, rpm\\
2006 July       & ~7 &  2006 07 14 & 2006 07 19 & ma, jps\\
2006 November   & 12 &  2006 11 01 & 2006 11 13 & ma, lpl, jps, yr\\
2006 December   & ~8 &  2006 12 09 & 2006 12 11 & jhp, jps, hg\\
2007 MarchApril & ~8 &  2007 03 30 & 2007 04 03 & jhp, gm, bv\\
2007 October    & 12 &  2007 10 05 & 2007 10 26 & jhp, jps, cg\\
2008 October    & ~8 &  2008 10 08 & 2008 10 14 & ma, jps\\
2008 December   & ~9 &  2008 12 09 & 2008 12 14 & jhp, pz, vha\\
2009 June       & ~9 &  2009 06 24 & 2009 06 26 & jhp, hg, arl\\
\bottomrule
\tabnotetext{}{jhp - J.H. Pe\~na; rpg - R. Peniche; rpm - R. Pe\~na Miller; jps - J. P. Sareyan; ma - M. Alvarez; yr - Y. Rosas; lpl - L. Parrao; 
hg - H. Garcia; gm - G. Mu\~noz; bv - B. Vargas; cg - C. Guerrero; pz - P. Zasche; vah - V. H. Alvarado and arl - A. Renteria.}
\end{tabular}
\vspace{0.3cm}
\end{table*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%% TABLA 2

\begin{table*}[!t]
\vspace{0.1cm}
\centering
\caption{Mean values and standard deviations $\langle \sigma \rangle$ for\\ the transformation coefficients during the\\ October 2008 season}
%\small
\begin{tabular}{cccccccc}
\toprule
Season          &  B      &   D    &   F    &   J    &  H     &   I   &   L\\
\midrule 
2008                     & 0.884 & 0.996 & 1.027 & 0.013 & 1.007  & 0.062 & $-$1.319\\
\noalign{\smallskip}
$\langle \sigma \rangle$ & 0.026 & 0.015 & 0.081 & 0.031 & 0.054  & 0.074 & ~~0.065\\
\bottomrule
\end{tabular}
\label{trancoef}
\vspace{0.3cm}
\end{table*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%



The transformation equations used in this work have the following form:
\begin{eqnarray}
V & = & \mathrm{A + B}~(b-y)(\mathrm{inst}) + y (\mathrm{inst})\,, \nonumber \\
(b-y)\mathrm{(std)} & = & \mathrm{C + D}~(b-y)(\mathrm{inst})\,, \nonumber \\
m_1\mathrm{(std)} & = & \mathrm{E + F}~m_1\mathrm{(inst) + J}~(b-y)\mathrm{(inst)}\,, \nonumber \\
c_1\mathrm{(std)} & = & \mathrm{G + H}~c_1\mathrm{(inst) + I}~(b-y)\mathrm{(inst)}\,, \nonumber  \\
\beta~\mathrm{(std)} & = & \mathrm{K + L}~\beta~\mathrm{(inst)}\,. \nonumber
\end{eqnarray}


%%%%% FIGURA 1

\begin{figure*}[!t]
%\vspace{0.1cm}
\centering
\includegraphics[width=0.67\textwidth,clip]{jpenafig1.ps}
\caption{A sample of transformation correlations between instrumental and standard values for a group 
of standard stars for the October 2008 season.} 
\label{transf}
\vspace{0.4cm}
\end{figure*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


Transformations between the instrumental and literature values for a group of standard stars are illustrated in Figure~1 for the night of 
October 11, 2008, while Table~2 presents values for the slopes and color term coefficients averaged for seven nights from the 2008 season. 
Standard deviations for each coefficient are listed at the bottom of the table. Except for the May 2005 season, which was devoted entirely 
to data acquisition of Cepheid stars, most seasons were planned for observation of short period variable stars, and hence few data points 
were obtained on each night for Cepheid and standard stars. Nevertheless, some seasons were long enough to obtain data strings suitable for 
covering the long cycles of some Cepheid stars.


%%%%% TABLA 3

\begin{table}[!t]
\vspace{0.1cm}
\centering
\caption{Photon counting uncertainties for\\ the night of October 11, 2008}
\setlength{\tabcolsep}{0.89\tabcolsep}
\footnotesize
\begin{tabular}{ccccccc}
\toprule
ID  & V & $u$ & $b$ & $v$ & $y$ & N\\
\toprule
BS 1430 & ~5.4 & 0.0004 & 0.0003 & 0.0002 & 0.0003 & ~4\\
RT AUR  & ~5.2 & 0.0005 & 0.0003 & 0.0002 & 0.0003 & ~5\\
SZ TAU  & ~6.5 & 0.0009 & 0.0006 & 0.0004 & 0.0004 & ~6\\
ST TAU  & ~8.5 & 0.0023 & 0.0014 & 0.0010 & 0.0010 & ~6\\
SY AUR  & ~9.0 & 0.0040 & 0.0020 & 0.0020 & 0.0020 & ~6\\
AO AUR  & ~9.1 & 0.0023 & 0.0014 & 0.0010 & 0.0010 & 10\\
AN AUR  & 10.7 & 0.0070 & 0.0040 & 0.0020 & 0.0020 & 10\\
ER AUR  & 11.6 & 0.0090 & 0.0050 & 0.0030 & 0.0030 & 10\\
\bottomrule
\end{tabular}
\label{counts}
\vspace{0.3cm}
\end{table}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%% TABLA 4

\begin{table*}[!t]
\vspace{0.3cm}
\centering
\setlength{\tabnotewidth}{0.7\textwidth}
\tablecols{8}
%\setlength{\tabcolsep}{1.0\tabcolsep}
\caption{Observed stars in $\uv$}
\small
\begin{tabular}{lccccccc}
\toprule
\multicolumn{1}{c}{Star} & Epoch & Period & AF\tablenotemark{1} & Eggen & Meakes & F\&McN\tablenotemark{2} & This paper  \\
                         &       &        & 1998                & 1983  & 1991   & 1980                    &     \\
\midrule
SW TAU  & 41687.77~ & ~1.583584 & ~6 &    & 7 &    & ~5\\
EU TAU  & 41324.22~ & ~2.10248~ &    &    &   &    & 14\\
SZ TAU  & 34628.57~ & ~3.14873~ & ~6 &    &   & 28 & 46\\
SS SCT  & 35315.625 & ~3.671253 & 26 & 13 &   & 29 & ~0\\
RT AUR  & 42361.155 & ~3.728115 &    &    &   &    & 11\\
Y  AUR  & 37203.629 & ~3.859485 & ~1 &    &   &    & 37\\
CM SCT  & 35111.32~ & ~3.916977 &    &    &   &    & 21\\
ST TAU  & 41761.963 & ~4.034299 & ~2 &    &   &    & 42\\
X  SCT  & 34905.58~ & ~4.19807~ &    &    &   &    & 16\\
VZ CYG  & 41705.702 & ~4.864453 & ~9 &    &   & 30 & 10\\
AS PER  & 41723.934 & ~4.972516 &    &    &   &    & 13\\
BG LAC  & 35315.273 & ~5.331908 &    &    &   & 26 & 18\\
UY PER  & 44945.845 & ~5.365106 &    &    &   &    & ~3\\
BX SCT  & 27901.83~ & ~6.41133~ &    &    &   &    & 11\\
AW PER  & 42709.059 & ~6.463589 &    &    &   & 23 & 11\\
AO AUR  & 42815.86~ & ~6.763006 &    &    &   &    & 15\\
CK SCT  & 40855.25~ & ~7.41522~ &    &    &   &    & 13\\
RS ORI  & 42820.794 & ~7.566881 & 10 & 21 &   &    & 25\\
VY CYG  & 43045.282 & ~7.856982 & ~2 &    &   &    & 10\\
RX CAM  & 42766.583 & ~7.912024 &    &    &   &    & ~4\\
BK AUR  & 17377.719 & ~8.002432 &    &    &   &    & 16\\
CN SCT  & 28670.16~ & ~9.9923~~ &    &    &   &    & ~7\\
SY AUR  & 36843.52~ & 10.144698 & ~1 &    &   &    & 36\\
AN AUR  & 36843.309 & 10.29056~ &    &    &   &    & 46\\
Y  SCT  & 34947.2~~ & 10.341504 & 27 &    &   &    & ~5\\
Z  LAC  & 42827.123 & 10.885613 & ~5 &    &   & 25 & 15\\
VX PER  & 43758.994 & 10.88904~ &    &    &   &    & ~4\\
TY SCT  & 37377.09~ & 11.05302~ &    &    &   &    & ~8\\
SV PER  & 43839.296 & 11.129318 & ~1 &    &   &    & 14\\
RX AUR  & 39075.63~ & 11.623515 &    &    &   & 21 & 61\\
Z  Sct  & 36247.16~ & 12.90133~ & 27 &    &   &    & ~5\\
TX CYG  & 43794.971 & 14.7098~~ &    &    &   &    & 10\\
RW CAS  & 35575.227 & 14.7949~~ &    &    &   &    & ~3\\
SZ CYG  & 43306.79~ & 15.10965~ & 10 &    &   &    & ~5\\
ER AUR  & 43861.3~~ & 15.69073~ &    &    &   &    & 11\\
X  CYG  & 43830.387 & 16.386332 & 18 &    &   & 53 & 13\\
RW CAM  & 37389.57~ & 16.41437~ &    &    &   &    & ~4\\
YZ AUR  & 37431.141 & 18.193212 &    &    &   &    & 28\\
RU SCT  & 31174.67~ & 19.70062~ & 27 &    &   &    & ~8\\
VX CYG  & 43783.642 & 20.133407 & ~6 &    &   &    & 13\\
\bottomrule 
\noalign{\smallskip}
\tabnotetext{1} {Arellano Ferro et al. (1998).}
\tabnotetext{2}{Feltz \& McNamara (1980).}
\end{tabular}
\vspace{0.2cm}
\end{table*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%5


%%%%% FIGURA 2

\begin{figure*}[!t]
%\vspace{0.05cm}
\centering
\includegraphics[width=0.8\textwidth]{jpenafig2.eps}
\caption{Light curves in $\uv$ for four stars observed by several authors. Note the good agreement 
between the various sources. Open circles: Arellano Ferro et al. (1998); crosses, Feltz \& McNamara 
(1980); filled circles, present work.}
\label{compas}
\vspace{0.4cm}
\end{figure*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%% TABLA 5

\begin{table*}[!t]
\vspace{0.1cm}
\centering
\setlength{\tabnotewidth}{0.98\textwidth}
\tablecols{10}
\caption{Sample $\uv$ observations of classical Cepheids}
\label{compara}
%\small
\begin{tabular}{lccccccccc}
\toprule
\multicolumn{1}{c}{Star} & $V$ & $b-y$ & $m_1$ & $c_1$ & HJD ($uvby$) & $\beta$ & HJD ($\beta$) & Epoch-2400000 & $P$ (days)\\
\midrule
SWTAU  & ~9.694  & 0.443  & 0.152  & 0.982  & 2447833.9053  & 2.713  & 33.9046  & 41687.77~  & 1.583584 \\
SWTAU  & ~9.712  & 0.410  & 0.112  & 1.076  & 2447837.9903  & 2.729  & 37.9923  & 41687.77~  & 1.583584 \\
SWTAU  & ~9.916  & 0.522  & 0.152  & 0.826  & 2454190.6381  &        &          & 41687.77~  & 1.583584 \\
SWTAU  & ~9.366  & 0.364  & 0.100  & 1.269  & 2454191.6274  &        &          & 41687.77~  & 1.583584 \\
SWTAU  &         & 0.514  & 0.148  & 0.809  & 2454192.6355  &        &          & 41687.77~  & 1.583584 \\     
EUTAU  & ~8.162  &        & 0.165  & 0.660  & 2454040.8979  &        &          & 41324.219  & 2.102480 \\  
EUTAU  & ~7.774  & 0.419  & 0.138  & 0.898  & 2454041.8543  &        &          & 41324.219  & 2.102480 \\  
EUTAU  & ~7.741  & 0.409  & 0.137  & 0.921  & 2454041.9443  &        &          & 41324.219  & 2.102480 \\  
EUTAU  &         & 0.494  & 0.159  & 0.784  & 2454042.8053  &        &          & 41324.219  & 2.102480 \\  
EUTAU  &         & 0.497  & 0.164  & 0.758  & 2454042.8578  &        &          & 41324.219  & 2.102480 \\  
\bottomrule
\tabnotetext{}{The full table is available in the electronic version of this paper.}
\end{tabular}
%\vspace{0.4cm}
\end{table*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\subsection{Photometric uncertainties}

Individual uncertainties were determined by calculating standard deviations for the fluxes in each filter for each star. Bright stars were 
clearly observed more accurately than faint ones, although faint stars were observed long enough to obtain photon counts of high S/N ratio. 
Representative values for the photon counting uncertainties $N/\sqrt{(N)}$ derived from measurements on the night of October 11, 2008, for 
Cepheids with magnitudes ranging from $V = 5.2$ to 11.6 are presented in Table~3, with the standard star BS 1430 included for comparison. 
Given the results, the uncertainties associated with photon counting appear to be negligible.

Seasonal errors were evaluated from the differences (calculated minus observed) between magnitudes and colors for the standard stars, with 
ten to fifteen standard stars being observed on each night. Emphasized is the large range in magnitude and colors for the standards. Figure~1 
presents for illustration standard deviations of the mean values in the differences 
$\langle \delta$($V$, $(b-y)$, $m_1$, $c_1$)$\rangle$ = (0.012, 0.005, 0.007, 0.018) for the October 2008 season.


%%%%% FIGURA 3

\setcounter{figure}{2}
\begin{figure*}[!t]
\centering
\includegraphics[width=16.9cm,height=21.7cm]{jpenafig3a.eps}
\caption{$\uv$ Light curves of program Cepheids.}
\label{lc}
%\vspace{0.4cm}
\end{figure*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%% FIGURA 3 CONTINUA

\setcounter{figure}{2}
\begin{figure*}[!t]
\centering
\includegraphics[width=16.9cm,height=21.7cm]{jpenafig3b.eps}
\caption{Continued.}
%\vspace{0.4cm}
\end{figure*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%% FIGURA 3 CONTINUA

\setcounter{figure}{2}
\begin{figure*}[!t]
\centering
\includegraphics[width=16.9cm,height=21.7cm]{jpenafig3c.eps}
\caption{Concluded.}
%\vspace{0.42cm}
\end{figure*}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\section{Results}

A summary of the program objects is given in Table~4. Column~1 gives the star name, and Columns~2 and 3 the ephemerides elements employed 
to calculate light curve phase. The elements were taken from the General Catalogue of Variable Stars (Samus et al. 2009) in order to provide 
current light curve phasing. Subsequent columns in the table report the number of observations for each star by each of the previously-mentioned 
$\uv$ photometric observers: namely, Feltz \& McNamara (1980), Eggen (1983, 1985), Meakes et al. (1991) and Arellano Ferro et al. (1998). The 
last column lists the number of observations from the present paper. Magnitudes and colors in the standard system obtained here for our sample 
of Cepheids are listed in Table~5. In the printed version only the first few lines of the table are shown as an example. The full table is available 
in the electronic version of this paper. 


\section{Comparison with previous photometry}

The confidence level of our observations can be evaluated from the uncertainties discussed previously, and the good quality of the photometry is 
demonstrated by the good agreement with previously reported $\uv$ observations. The archival sources cited previously and the number of data points 
for each star are listed in Table~4. Of those, four stars with a large number of observations from different observers were selected to demonstrate 
the excellent agreement among the various data sets.

The stars considered for comparison were X Cyg, VZ Cyg, SW Tau, and SS Tau. As evident from Figure~2, the various observations are in excellent 
agreement with each other. A comparison was made between the data of Arellano Ferro et al. (1998) and those of the present paper for all stars, 
and all observations fit in either the light curve or color index diagrams, demonstrating once again the stability of the stellar pulsations and 
the reproducibility and good quality of the observations. Figure~3 illustrates light curves for most of the Cepheids in our sample. The 
figure includes two data sets for each star, namely those of Arellano Ferro et al. (1998), represented by open circles, and those of the present 
paper by filled circles.


\section{Conclusions}

New $\uv$ photoelectric photometry has been acquired and is presented for 41 Cepheid stars. Such data can be useful for various fields of 
Cepheid research, such as the study of secular period changes (Szabados 1991; Arellano Ferro 1983), metallicity (Arellano Ferro \& Mantegazza 
1996), interstellar reddening (Chulhee 2008), and other physical parameters, for instance mean radii through applications of the Baade-Wesselink 
method (Arellano Ferro \& Rosenzweig 2000). The photometry can also be utilized for several other purposes: to establish relationships with 
other basic properties, such as empirical determinations of pulsation mode like those developed for RR Lyrae stars (e.g., Kov\'acs \& Walker 
2001, and references therein) through Fourier decomposition of the light curves (e.g., Pe\~na et al. 2009); to determine metallicity photometrically 
from color indexes compared directly with predictions from theoretical models (e.g., Meakes et al. 1991); to support and improve knowledge of the 
chemical enrichment gradient in the Galaxy (e.g., the series of papers by Andrievsky et al. 2004, and references therein), among other topics.

\vspace{0.25cm}

\acknowledgments

We thank the staff of the OAN for their assistance in securing the observations, and acknowledge the help of several colleagues who participated 
in the observations: R. Peniche, L. Parrao, V.~H. Alvarado and P. Zasche. This work was partially supported by PAPIIT \,IN110102 \,and \,IN108106-3. 
\,RPM, \,GM, \,BV, VHA and HG thank the \,IA-Universidad \,Nacio- \adjustfinalcols nal  Aut\'onoma de M\'exico for the opportunity to carry out the 
observations. Typing was partially done by J. Orta, and proofreading by J. Miller. C. Guzm\'an, F. Ruiz and A. D\'iaz assisted us in the computer 
reductions. We are indebted to an anonymous referee for a series of comments and suggestions that led to improvement of the present paper. This 
research has made use of the Simbad databases operated at CDS, Strasbourg, France, and the NASA ADS Astronomy Query Form.

\vspace{0.4cm}

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\vspace{0.07cm}

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