The Variable Star Population of the globular cluster B514 in the Andromeda %Galaxy\thanks{Based on data collected with the Wide Field Planetary Camera 2 on board of the %Hubble Space Telescope and ACS HST archive data.}
Gisella Clementini\altaffilmark{1}
Rodrigo Contreras\altaffilmark{1,2}
Luciana Federici\altaffilmark{1}
Carla Cacciari\altaffilmark{1}
Roberto Merighi\altaffilmark{1}
Horace A. Smith\altaffilmark{3}
M\'arcio Catelan\altaffilmark{4,5,}
Flavio Fusi Pecci\altaffilmark{1}
Marcella Marconi\altaffilmark{6}
Karen Kinemuchi\altaffilmark{7,8}
and Barton J. Pritzl\altaffilmark{9}
A rich harvest of RR Lyrae stars has been identified for the first time in B514, a metal-poor ([Fe/H]$\sim$ --1.95 $\pm$0.10 dex) globular cluster of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys time-series observations. We have detected and derived periods for 89 RR Lyrae stars (82 fundamental-mode $-$RRab$-$ and 7 first-overtone $-$RRc$-$ pulsators, respectively) among 161 candidate variables identified in the cluster. The average period of the RR Lyrae variables ($\langle Pab \rangle$ = 0.58 days and $\langle Pc \rangle$ = 0.35 days, for RRab and RRc pulsators, respectively) and the position in the period-amplitude diagram both suggest that B514 is likely an Oosterhoff type I cluster. This appears to be in disagreement with the general behaviour of the metal-poor globular clusters in the Milky Way, which show instead Oosterhoff type II pulsation properties. The average apparent magnitude of the RR Lyrae stars sets the mean level of the cluster horizontal branch at $\langle V(RR) \rangle = 25.18 \pm 0.02$ % standard deviation of the mean ($\sigma$=0.16 mag, on 81 stars). By adopting a reddening $E(B-V) = 0.07 \pm 0.02$ mag (\citealt{sc98}), the above metallicity and M$_V$=0.44$\pm$0.05 mag for the RR Lyrae variables of this metallicity (\citealt{clem03}), we derive a distance modulus of $\mu_{0}=24.52 \pm 0.08$ mag, corresponding %ida:$\mu_{0}=20.94 \pm 0.07$ mag to a distance of about $800 \pm 30$ kpc, based on a value of M$_V$ that sets $\mu_{0}$(LMC)=18.52.
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\newcommand{\distance}{$23.36 \pm 0.15$}  %-- nuova dist. con 0.59 at -1.5
\newcommand{\Nvarall}{84}
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\newcommand{\Pmean}{$0.613 \pm 0.028$}   %-- Lara
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\newcommand{\modlmc}{$18.48 \pm 0.05$}
\newcommand{\Mvrrmygal}{0.50}
\newcommand{\Ebv}{0.25}
\newcommand{\RR}{3.1}
\newcommand{\Av}{0.78}

\newcommand{\mygal}{NGC\,6822}
\newcommand{\di}{{dI}}
\newcommand{\rrl}{{RR~Lyrae}}
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\shorttitle{Variable stars in B514}
\shortauthors{Clementini et al.}

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\begin{document}


%\title{The Variable Star Population of the globular cluster B514 in the Andromeda 
%Galaxy\thanks{Based on data collected with the Wide Field Planetary Camera 2 on board of the
%Hubble Space Telescope and ACS HST archive data.}}
\title{The Variable Star Population of the globular cluster B514 in the Andromeda 
Galaxy\altaffilmark{*}}
\author{ Gisella Clementini\altaffilmark{1}, Rodrigo Contreras\altaffilmark{1,2},
Luciana Federici\altaffilmark{1}, Carla Cacciari\altaffilmark{1}, Roberto Merighi\altaffilmark{1}, Horace A. 
Smith\altaffilmark{3}, M\'arcio Catelan\altaffilmark{4,5,}, Flavio Fusi Pecci\altaffilmark{1}, Marcella 
Marconi\altaffilmark{6}, Karen Kinemuchi\altaffilmark{7,8}, and Barton J. 
Pritzl\altaffilmark{9}}
\altaffiltext{1}{INAF, Osservatorio Astronomico di Bologna, Bologna, 
Italy; gisella.clementini@oabo.inaf.it 
%rodrigo.contreras@oabo.inaf.it, luciana.federici@oabo.inaf.it, 
%carla.cacciari@oabo.inaf.it, roberto.merighi@oabo.inaf.it, flavio.fusipecci@oabo.inaf.it
}
\altaffiltext{2}{Dipartimento di Astronomia, Universit\`a di Bologna, Bologna, Italy}
\altaffiltext{3}{Department of Physics and Astronomy, Michigan State
University, East 
Lansing, MI 48824, USA; kuehncha@msu.edu, smith@pa.msu.edu, beers@pa.msu.edu}
\altaffiltext{4}{Pontificia Universidad Cat$\rm{\acute{o}}$lica de Chile, Departamento de Astronom\'{\i}a y Astrof\'{\i}sica, 
Santiago, Chile; mcatelan@astro.puc.cl}
%\altaffiltext{5}{On sabbatical leave at Michigan State University, Department of Physics and Astronomy, 3215 Biomedical and Physical 
%Sciences Bldg., East Lansing, MI 48824} 
\altaffiltext{5}{John Simon Guggenheim Memorial Foundation Fellow} 
\altaffiltext{6}{INAF, Osservatorio Astronomico di Capodimonte, Napoli, Italy; marcella@na.astro.it}
\altaffiltext{7}{Universidad de Concepci\'on, Departamento de Astronom\'{\i}a, Concepci\'on, Chile, kkinemuchi@astro-udec.cl}
\altaffiltext{8}{Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055, USA; 
kinemuchi@astro.ufl.edu}
\altaffiltext{9}{Department of Physics and Astronomy, 
University of Wisconsin Oshkosh, Oshkosh, WI 54901, USA; pritzlb@uwosh.edu}
\altaffiltext{*}{Based on data collected with the Wide Field Planetary Camera 2 on board of the
Hubble Space Telescope and ACS HST archive data.}
%---------------
%\altaffiltext{1}{Based on data collected with the Wide Field Planetary Camera 2 on board of the
%Hubble Space Telescope and ACS HST archive data.
%}


\begin{abstract}
A rich harvest of RR Lyrae stars has been identified for the first time in B514, a 
metal-poor ([Fe/H]$\sim$ --1.95 $\pm$0.10 dex) globular cluster of the Andromeda galaxy (M31),  
based on Hubble Space 
Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys time-series 
observations. We have detected and derived periods for 89 RR Lyrae stars (82 fundamental-mode $-$RRab$-$ and 
7 first-overtone $-$RRc$-$ pulsators, respectively) among 161 candidate variables identified in the cluster. 
The average period of the RR Lyrae variables ($\langle Pab \rangle$ = 0.58 days 
and $\langle Pc \rangle$ = 0.35 days, for RRab and RRc pulsators, respectively) and the position in the 
period-amplitude diagram both suggest that B514 is likely an Oosterhoff type I 
cluster. This appears to be in disagreement with the general behaviour of the metal-poor globular 
clusters in the Milky Way, which show instead Oosterhoff type II pulsation properties.

The average apparent magnitude of the RR Lyrae stars sets the mean level of the cluster 
horizontal branch at $\langle V(RR) \rangle = 25.18 \pm 0.02$ 
% standard deviation of the mean 
($\sigma$=0.16 mag, on 81 stars). By adopting a reddening $E(B-V) = 0.07 \pm 0.02$ mag 
(\citealt{sc98}), the above metallicity and M$_V$=0.44$\pm$0.05 mag for the RR Lyrae variables 
of this metallicity (\citealt{clem03}), 
we derive a distance modulus of $\mu_{0}=24.52 \pm 0.08$ mag, corresponding 
%ida:$\mu_{0}=20.94 \pm 0.07$ mag
to a distance of about $800 \pm 30$ kpc, based on a value of M$_V$ that sets 
 $\mu_{0}$(LMC)=18.52. 
  



\end{abstract}

\keywords{
galaxies: individual (M31)
---globular clusters: individual (B514)
---stars: distances
---stars: variables: other 
---techniques: photometric
}


\section{Introduction}
The Andromeda galaxy provides us with a unique opportunity to study the 
formation and  evolution of a massive spiral galaxy other than  the Milky Way
(MW). 
%%$\Lambda$-cold-dark-matter 
%%hierarchical models of galaxy formation predict 
%%that the halo of a large galaxy is assembled via merging of smaller 
%%subsystems. 
Various authors (\citealt{vdb00,vdb06}) suggested that M31 originated as an 
early merger of two or more massive metal-rich progenitors, accounting for the galactic halo 
wide range in metallicity (\citealt{dhp01}) and age (\citealt{bro03}) compared to the MW.
There is also an interesting suggestion by \citet{kra02} that the ``young'' second-parameter 
globular clusters in our Galaxy, as well as at least some of the MW dwarf spheroidal companions, 
were in fact accreted 
from M31 when Andromeda was forming its Population II stars.


The pulsation properties of the variable stars in the field and globular
clusters (GCs) of M31 have the potential
to provide essential insights on the galaxy formation and to trace the
merging episodes that led to the early assembling of the galaxy.
The RR Lyrae stars, in particular, belonging to the old stellar population 
(t $> 10$ Gyr), were eyewitnesses to the first epochs of star formation in M31. 
Their mean periods along with the metallicities of the parent clusters can be used to 
set the luminosity of the horizontal branch (HB), and hence can provide 
% an independent estimate of the M31 cluster ages and, in turn, of the time scale of the M31 halo formation by 
precious information on how the M31 halo formed and evolved, in comparison with their 
MW counterparts (see e.g. \citealt{cat04}, 2009).

In the MW the vast majority of GCs which contain significant numbers of 
RR Lyrae stars sharply divide into two very distinct classes, the Oosterhoff
types I and II (\citealt{oo39}; see \citealt{cat09} for a recent review) according 
to the mean 
pulsation periods of their RR Lyrae variables. Oosterhoff type I (OoI) GCs have 
$\langle Pab \rangle \simeq 0.56$ days, 
Oosterhoff type II clusters (OoII) have $\langle Pab \rangle \simeq$ 0.66 days (\citealt{cle01}). 
This phenomenon is referred to as the Oosterhoff dichotomy. 
There is evidence that OoI and OoII clusters in the MW may have different 
kinematical and spatial distributions thus possibly resulting from different 
accretion or formation events in the halo. This is supported also by a 
difference in mean chemical abundance, OoII clusters being on average more 
metal-poor than OoI clusters, and possibly by a difference in age, metal-poor
clusters being on average slightly older than the intermediate-metallicity
ones (\citealt{vdb93};  \citealt{dea05}; \citealt{mar09}).
Whatever the mechanism, it is clear 
that the Oosterhoff dichotomy reflects conditions within the MW halo at the 
time of GC formation.
The existence or absence of the Oosterhoff phenomenon among the  M31 GCs  
therefore provides  information on the halo formation processes  and thus on 
the chemical/dynamical  evolution history of the dominant galaxy of the 
Local Group (\citealt{cat04}, 2009). 
Detection and characterization of RR Lyrae stars in M31 globular clusters 
is challenging since they are too crowded to be well-studied 
with ground-based telescopes. 
There has been only one previous attempt
at detecting RR Lyrae stars in the globular clusters of M31.
Clementini et al. (2001) used archival data obtained with the Wide Field Planetary Camera 2 
(WFPC2) onboard the Hubble Space Telescope 
(HST) to make the first tentative detection of RR Lyrae stars in 
4 clusters, namely, G11, G33, G64, and G322.
A number of RR Lyrae candidates were identified in each cluster (two, four, eleven,  and eight variables, 
in G11, G33, G64, and G322, respectively), but 
the small number of available data points and the short time baseline did not 
allow a definition of light curves and hence periods.
As part of a Cycle 15 HST program we have observed a number of M31 GCs to properly characterize their variable star population.
The clusters were selected as to have metallicities that, in the Milky Way, would place them either in the OoI or in the OoII groups.
%yin metallacitiy as to have  
Here we present results 
for B514, a globular cluster 
%recently discovered in Andromeda, which is 
located at a projected distance 
of $\sim55$ Kpc from the M31 center, not far from the galaxy's major axis 
(\citealt{gal05}). The color-magnitude diagram (CMD) indicates that B514 
is a classical, old metal-poor globular cluster.  The metallicity [Fe/H] is estimated as the 
weighted mean value of a few independent determinations, namely --1.8$\pm$0.3 
(spectroscopic from \citealt{gal05}), 
--1.8$\pm$0.15 (from the CMD, \citealt{gal06}), and --2.14$\pm$0.15 (from the CMD, \citealt{mck07}). 
The integrated absolute magnitude 
$M_V$ has been estimated of $\sim -9.1$ mag, and classifies the cluster among the 
brightest globulars of M31. Moreover, the observed half-light radius $r$ = 1.6 arcsec, corresponding to 
$\sim$ 6 pc at the distance of M31 (see below), is significantly larger than for most clusters 
of the same luminosity (\citealt{fed07}). 
%({\bf GC: qualcuno qui aggiunga qualcosa sul fatto che B514 potrebbe essere una galassia, dire delle possibili code mareali citando l'articolo 
%sul profilo di brillanza \citealt{fed07}.})
%
%%
%%The Oosterhoff-intermediate nature of these systems may provide constraints on possible accretion 
%%scenarios for the Galactic halo.

In this Letter we present results of a search for variable stars 
which lead us to the discovery of about a hundred RR Lyrae stars in B514.
This number is larger than found in the vast majority of the MW globular clusters, and since 
we are not able to resolving the cluster's core, there are likely many more RR Lyrae stars
in B514.
This is the first time that a large sample of RR Lyrae stars is discovered in an M31 globular cluster
and that their pulsation properties (periods, amplitudes, etc.) are fully characterized
thus allowing to establish the cluster's Oosterhoff type. 
Here we focus on the Oosterhoff classification of B514 and on its importance to get hints on the 
formation of the Andromeda galaxy by comparison with the properties of variables in the MW globular clusters.
%
% 
%, and use the RR Lyrae stars that were discovered to establish its Oosterhoff classification.  
We also present a $V, V-I$ CMD of B514 based on the ACS data extending 
to $V = 28$ mag. This is about half a magnitude fainter than the cluster CMDs  by \citet{gal06} and 
\citet{mck07}. %Here we will focus on the Oosterhoff classification and its importance by comparison with 
%the MW GCs. 
The complete list of the cluster variables with ephemerides, photometric data and light curves, will be presented 
in Contreras et al. (2009, in preparation), where we will discuss in  more detail their specific 
pulsation and evolutionary properties.
%%%% and
%%%%allows us to obtain insight on the stellar components of CVn\,I by fitting the 
%%%%galaxy CMD 
%%%%to the mean ridge lines of Galactic GCs and 
%%%%to 
%%%%theoretical isochrones of different metallicity and age.

\section{Observations and Data Reduction}
Time-series F606W, F814W observations of B514 (R.A.= 00$^h$ 31$^m$ 09$^s$.83, 
decl.= 37$^{\circ}$ 53$^{\prime}$ 59$^{\prime \prime}$.6) were obtained with 
the WFPC2 under HST program GO
11081 (PI G. Clementini) in June 12-14, 2007.
The time series consisted of fifteen individual exposures in each filter, of 1100$^s$ length, 
taken by alternating the filters. 
They were scheduled in three 10-orbit blocks executed almost continuously from 2007,  
June 12, UT 18$^h$ 16$^m$ 19$^s$, to  2007, June 14, UT 01$^h$ 23$^m$ 38$^s$, for total exposure times of 4 hours and 35 min in each band.  
The WFPC2 proprietary data were combined with ACS/WFC archive data from program GO 10394 (PI  N.R. Tanvir),
covering the period 2005, July 19-20, and from program GO 10565 (PI S. Galleti)
obtained in 2006, June 10, making a total of 20 phase-points 
in the F606W-band and 21 phase-points in the F814W-band.
Photometric reduction of the individual pre-reduced images supplied by the STScI
pipeline was performed using HSTPHOT and Dolphot/ACSPHOT (\citealt{dol00a,dol00b}). These are PSF-fitting photometry packages 
specifically designed to perform photometry on point sources 
observed with HST/WFPC2 and HST/ACS. The packages identify sources above a fixed flux threshold and perform
photometry on individual frames, taking into account information on CCD defects that are 
attached to the pre-reduced frames and automatically applying the correction for charge transfer efficiency (CTE) (\citealt{dol00a}). 
Position, flight system magnitudes and Johnson-Cousins standard magnitudes of the sources are provided as output, 
along with a number of quality parameters of the measured sources (see \citealt{dol00a}, for details). 
%for a suitable sample selection 
%(Here we have retained 
%all the sources with the global quality flag=1 (i.e. best measured stars), crowding $<$0.3, 0.5$<$sharpness$<$0.5,
%$\chi^2 <$1.5 for V$>$ 24. and $\chi^2 <$2.5 for the brightest stars)}.
%
%
%{\bf  RODRIGO, LUCIANA  complete the part that follows in italic.}
%\\
%
%{\it Images were bias subtracted and flat-field corrected using ......
%IRAF.
%%IRAF\footnote[11]{IRAF is 
%%distributed by the National Optical Astronomical Observatory, which is operated 
%%by the Association 
%%of Universities for Research in Astronomy, Inc., under cooperative agreement 
%%with the National Science Foundation.}.  
%%%%Fringing in the $I$-band  images was corrected using a fringe map for each 
%%%%image.
%%%%Peter Stetson's 
%The .....%{\sc Daophot II/Allstar} packages \citep{st87,st92} 
%package was used to 
%obtain instrumental magnitudes for 
%each star.  
%These were transformed to the standard system using .... calibration .... %observations of the Landolt 
%standard fields 
%PG1323, PG1633, and SA104 \citep{la92} at WIRO, and PG0918 and PG1633 at the 
%WHT.  
%%%%The observed standard 
%%%%stars were then used to derive the calibration equations for each telescope.
Typical errors of the combined photometry (8 ACS frames) for non-variable stars
%of our photometry 
at the magnitude level of the B514 horizontal branch (HB, $V \sim 25.2$ mag)  are
$\sigma_{V}$ = 0.017 mag, $\sigma_{I}$= 0.015 mag for the ACS dataset, 
and $\sigma_{V}$ = 0.019 mag,  $\sigma_{I}$= 0.032 mag for the WFPC2 data. 

\section{Variable Stars}
Variable star candidates were identified from the scatter diagrams of the F606W and F814W datasets, using  VARFIND, 
custom software developed at the Bologna Observatory by 
P. Montegriffo.  
We first analyzed the WFPC2 proprietary data, whose extended time series are optimized for the detection of
variables of RR Lyrae type. The WFPC2 candidate variables were then counteridentified on the ACS data.
A further search with VARFIND  was later performed on the ACS archive data, and the counteridentification with the WFPC2 data was iteratively repeated.
The search procedure returned a final catalogue of 161 candidate variables, most of which are located 
on the cluster HB. Many more will likely exist in the core of the cluster, that we have not detected. 
Periods and classification in type of the candidate variables were derived from the study of the 
light curves with Graphical Analyzer of Time Series (GRaTiS; see \citealt{clem00}).
%
%
% used the F606W-band time series, %which had more phase points than the other bands, 
%to identify variable 
%stars using the scatter diagram XXXXXX  ({\bf Gisella, descrivi qui come e' stato fatto.})
%Variable star candidates were identified with VARFIND (custom 
%software developed at the Bologna Observatory by P. Montegriffo).
%Periods and type classification 
%%were obtained for 89 confirmed variable stars in B514 
%were derived from the study of the  light curves using 
%GRATIS (custom software, by P. Montegriffo).
We obtained reliable periods and light curves for 89 RR Lyrae stars: 82 fundamental-mode 
(RRab) and 7 first-overtone (RRc) pulsators.  
For the remaining 72 candidates we still lack a firm classification, mostly because of scatter 
in the data.  
The time sampling of our data covers nearly 29 hours in three observing blocks of 7 hours 
each, separated by two gaps of 50 minutes and 7 hours respectively. In addition, we have 
6 epochs of archive data spaced by 694 and 368 days. This ensures that all possible periods 
of RR Lyrae stars are well sampled and no bias or alias effects are present, and allows 
us to derive accurate periods mostly to the 4th decimal digit.   
  



Figure~\ref{f:figcmd} shows the $V,V-I$ CMD of B514, 
obtained 
from the ACS data, for stars in four separate regions at increasing distance from the cluster center.
%the PC ({\it panel a}) and in the other cameras
 % of the WHT field of view: 
%annular regions with different distance from the galaxy center: $r < 8.1^{\prime}$, roughly corresponding to the
%total field of the WHT observations,  (Fig. 1{\it a}); 
%$r < 4.5^{\prime}$, (Fig. 1{\it b}); and $4.5^{\prime} < r < 8.1^{\prime}$, (Fig. 1{\it c}). 
Only sources with
%$\sigma_{V}$, $\sigma_{B} \leq X.XX$ mag, $\chi \leq$ X, and shape-defining 
%parameter $\mid SHARP \mid \leq $ 0X.XX ({\bf RODRIGO or LUCIANA provide the right numbers here if applicable}).
%global quality flag=1
object type flag=1 (i.e. best measured stars), crowding $<$0.3, 0.5$<$sharpness$<$0.5,
$\chi^2<$1.5 for V$>$ 24 mag and $\chi^2<$2.5 for brighter stars are shown in the 
figure\footnote{The 
photometric data generating the CMD are available in electronic form upon request.}. 
Confirmed variable stars are plotted as red filled circles, candidate variables 
with sufficient light curve sampling as blue filled circles, and less reliable candidates as green filled circles.
%The blue candidates have better light curve sampling, hnece are more reliable than green ones. 

%The position of the variables on the cluster CMD obtained from the ACS data is shown in Figure~\ref{f:figcmd}
%for different regions with increasing the distance from the cluster centre.
According to their 
position on the CMD, the vast majority of the candidate variables discovered in B514 are likely RR Lyrae stars.
However, our candidate's list also includes a number of binaries and a few objects above and below the HB.
Variable stars are plotted in the CMD using mean magnitudes and colors computed as simple averages of the available photometric measurements.
The scatter observed around the average level of the HB is therefore largely due to variable stars 
with uneven coverage of the light curve, and  will likely be significantly reduced when the mean 
magnitudes will be derived averaging over the full pulsation cycle. 
The upper panel of Figure~2 shows the location of the B514 variable 
stars on the $3^{\prime}$ 22$^{\prime \prime}\times 3^{\prime}$ 22$^{\prime \prime}$ %map, 
%corresponding to the 
field of view covered by the ACS observations of \citet{gal06}. The lower panel of Figure~2 shows an 
enlargement of the variable stars' map corresponding to  a $30^{\prime \prime} \times 30^{\prime \prime}$ region around the cluster center.
%Their position on the cluster is shown in Figs.~2 and 3.
As noted in \citet{fed07}, B514 is rather extended (see their Fig. 6) and its tidal radius was estimated as $\sim$ 17 arcsec 
($\sim$ 65 pc) from the analysis 
of the distribution of the integrated light and star counts. 
However, we have detected variables well beyond this distance, in particular five RR Lyrae stars are 
located farther than 50 arcsec and as far as $\sim$ 90 arcsec from the cluster 
centre (Fig. \ref{f:figisto}). Although they are likely field stars, 
%% This area of the sky is not very crowded, and this density of variables would be unusually high 
%% if they were members of the field population. On the other hand, if they belonged to B514 then the 
%% cluster would be extremely extended, as also suggested by the CMD in the annulus 50-100 arcsec shown in Fig. \ref{f:figcmd}. 
the CMD shown in Fig. \ref{f:figcmd} indicates that a non negligible fraction of the cluster 
population is still present in the annulus 50-100 arcsec, suggesting the possibility that at 
least a few of these distant variables may belong to the cluster. 
Radial velocity membership will be the most reliable way to assess to which population they belong.   
%
%
%({\bf Qui va detto che le variabili si trovano fino a 93 arcsec dal centro del cluster che quindi sembra essere estesissimo, riprendere il discorso 
%che possa essere una galassia. VA BENE COME HO DETTO SOPRA? CC })  
%
% we show the position of
%these variables on the cluster CMD.
%\begin{figure}
%\includegraphics{cdlab.ps}
%\includegraphics{cdlc.ps}
%\caption

%
%
%\caption
%\realfigure{cdlc.ps}
%{$V$, $I$ light curves for RRab (top panels) and RRc (lower panels) variables
%identified in our survey. Filled and open circles indicate WFPC2 and ACS
%data, respectively.}
%In Figure~\ref{f:figlc} we show examples of the
%calibrated $V$ and $I$ light curves for two fundamental mode (RRab) and
%two first-overtone (RRc) RR Lyrae stars, respectively. 
%
%Peter Stetson's {\sc Allframe/Trial} package \citep{st94}.  A total 
%of 84 candidate variables were 
%identified.  
%%%%The majority of these had brightnesses and colors consistent with 
%%%%positions on the HB, 
%%%%but not all of these stars had a sufficient number of good observations for the 
%%%%determination of periods. 
%%%%Period searches were carried out using 
%%%%%Supersmoother \citep{re94}.  The 
%%%%resultant light curves were 
%%%%fit to template light curves \citep{ly98} in order to classify the type of 
%%%variable star; these classifications 
%%%were confirmed by eye.  
%By this procedure
%Comparatively few RRc variables were 
%identified compared 
%to RRab stars, since we had greater difficulty in establishing reliable periods XXXXX {\bf CHECK}
%for RRc candidates
%due to aliasing problems; their number may therefore be underestimated. 
%%%Three brighter variables about 1.5-2 magnitudes
%%%above the galaxy's HB were also identified. They are possibly Anomalous 
%%%Cepheids (ACs), but have incomplete phase coverage.
Examples of  light curves for 2 fundamental-mode and 2 first-overtone RR Lyrae stars we have identified 
in B514 are shown in Figure~\ref{f:figlc}. 
% Time series data for the four variables are available in electronic form upon request. NO, IO NON LO METTEREI cc 
% {\bf  GC: Forse questa tabella si puo' anche togliere, cosa suggerite? IO SUGGERISCO DI NON METTERLA, CI PENSERETE 
%  MAGARI NEL PROSSIMO ARTICOLO PER TUTTE LE VARIABILI CC }  
% Identification and properties (period, $V,I$ amplitudes, and intensity-average mean magnitudes)
% for these 4 confirmed RR Lyrae stars are provided in Table~1.
% in the CVn~ I dSph 
%%\begin{figure}
%%\plotone{cvnI_ltcurves.eps}
%%\caption{$V$ and $B$ light curves of variable stars in CVn\,I.  $Top:$ RRab star.
%%$Middle:$ RRc star.  $Bottom:$ Potential anomalous Cepheid.}
%%\end{figure}
%%\begin{figure}
%%\plotone{cvn_period_amp.ps}
%%\caption{Period-amplitude diagram in the $V$ band for the CVn\,I RR Lyrae stars. 
%%RRab stars 
%%are indicated by blue crosses and RRc stars are indicated by purple triangles. The solid
%%and dashed 
%%lines are the positions of Oosterhoff type I (OoI) and Oosterhoff type II
%%(OoII) Galactic 
%%Globular Clusters from \citet{cr00}.  The location of the majority of the RRab
%%stars between 
%%the OoI and OoII lines indicates that CVn\,I is an Oosterhoff-intermediate
%%object.}
%%\end{figure}
%%
%%\realfigure{xy_s_arc.ps} 
%%%%%%\realfigure{f3.ps} 
%%%%%%{Smoothed 
%%%%%%%X,Y 
%%%%%%map of the galaxy stars in the field of view of the WHT observations, in differential 
%%%%%%R.A. and decl. from the CVn\,I dSph center. The bulk of the
%%%%%%CVn\,I stars is within the black ellipse which has semi-major axis $r$= 6.7 arcmin and ellipticity $e$=0.55. The blue
%%%%%%circle has a radius of $r$ = 7 arcmin. 
 %%%%%%}{f:fig3}
The mean periods of the 89 confirmed RR Lyrae stars in 
B514 are $\langle Pab \rangle \sim$0.58 days and $\langle Pc \rangle \sim$ 0.35 days
for fundamental mode and first-overtone variables, respectively, suggesting a 
possible dominance of Oosterhoff type I.
Figure \ref{f:figpa} shows the $V$-band period-amplitude diagram of the B514 RR Lyrae 
stars along with the Oosterhoff loci defined by the Galactic globular clusters from 
\citet{cle00} (linear relations), and the period-amplitude distributions of 
\emph{bona fide} regular and  evolved RRab stars in M3 (quadratic relations), 
from Cacciari et al. (2005). 

%and the distributions of \emph{bona fide} regular 
%(\emph{solid curve}) and well evolved (\emph{dashed curve}) 
%RRab stars in M3, from Cacciari et al. (2005).
The B514 RR Lyrae stars are  close to the loci of 
Oosterhoff type I systems and regular RRab stars in M3.
In conclusion, B514 appears to be a somewhat borderline OoI cluster, as it seems to follow 
a different rule than what is found in the MW where metal-poor ([Fe/H]$\lesssim-1.7$) GCs containing 
RR Lyrae stars show Oosterhoff type~II properties. 
%However,  this indication is just preliminary and needs further study to be confirmed.   
 However, these results should be taken with caution since B514 could be a peculiar cluster. The entire sample 
of M31 clusters observed in our Cycle 15 program needs to be 
carefully analyzed (see Contreras et al. 2010, in preparation) to reach more firm conclusions 
on the Oosterhoff properties of the M31 globular clusters.  

%Though 
%%Comparatively few RRc variables were identified compared 
%%to RRab stars, since we had greater difficulty in establishing reliable periods for RRc candidates
%%due to aliasing problems, and their numbers 
%%may therefore be underestimated. ({\bf (Why?}).
%%
%%%%%%\begin{figure*}
%%%%%%%%%\includegraphics[scale=.60]{pl_ell_last.ps}
%%%%%%%%%\includegraphics[scale=.90]{pl_ell_last.ps}
%%%%%%\includegraphics[scale=.90]{f4.ps}
%%%%%%\caption{$V,B-V$ CMDs of the Canes Venatici I dwarf spheroidal galaxy obtained from stars
%%%%%%in the whole 16.2 $\times$ 16.2 arcmin$^2$ field covered by the 
%%%%%% WHT observations (Fig. 4{\it a});  and in 3 separate regions 
%%%%%% %%%%% corresponding to the 
%%%%%% black ellipse (Fig. 4{\it b}); the intermediate region between ellipse and
%%%%%% blue circle (Fig. 4{\it c}); and the region outside the blue circle (Fig. 4{\it d}) of Figure~\ref{f:fig3} .
%%%%%%%%
%%%%%%%%
%%%%%%%%
%%%%%%%%obtained
%%%%%% %%%%%%%with the WHT 4.2m telescope in three different annular regions of the galaxy.
%%%%%%%%%Only stars with
%%%%%%%%%$\sigma_{V}$, $\sigma_{B} \leq 0.10$ mag, $\chi \leq$ 0.2, and $\mid SHARP $\mid \leq  0.5$
%%%%%%%%%are displayed. 
%%%%%%Plotted in red are stars of the Galactic globular cluster
%%%%%%M68, after \citet{wa94}.
%%%%%%%%Candidate variable stars are marked as cyan circles, 
 %%%%%%%the RRab and the RRc stars are marked as red and blue circles, respectively, and the potential Anomalous Cepheids 
%%are marked as magenta circles.
%%%%}%%%%gisella${f:fig4}
%%%%\label{f:fig4}
%%%%\end{figure*}

\section{CMD and Distance}
%\begin{figure}
%\includegraphics[clip=true]{cmdpc.ps}
%\realfigure{4panVV-I.eps}
%{B514 CMD, based on our HSTPHOT reduction of 30 WFPC2 images. Bona-fide RR Lyrae
%stars are indicated by filled circles and variable star candidates by open 
%squares.
%}{f:figcmd}
%%%\realfigure{xy_s1.ps} 
%%%{Smoothed X,Y map of the CVn\,I stars in the field of view of the WHT observations.}{f:fig3}
%Figure~\ref{f:figcmd} shows the $V,B-V$ CMDs of B514 
%obtained 
%from the ACS data for stars in four separate regions with increasing distance from the cluster center.
%%the PC ({\it panel a}) and in the other cameras
% % of the WHT field of view: 
%%annular regions with different distance from the galaxy center: $r < 8.1^{\prime}$, roughly corresponding to the
%%total field of the WHT observations,  (Fig. 1{\it a}); 
%%$r < 4.5^{\prime}$, (Fig. 1{\it b}); and $4.5^{\prime} < r < 8.1^{\prime}$, (Fig. 1{\it c}). 
%Only sources with
%%$\sigma_{V}$, $\sigma_{B} \leq X.XX$ mag, $\chi \leq$ X, and shape-defining 
%%parameter $\mid SHARP \mid \leq $ 0X.XX ({\bf RODRIGO or LUCIANA provide the right numbers here if applicable}).
%global quality flag=1 (i.e. best measured stars), crowding $<$0.3, 0.5$<$sharpness$<$0.5,
%$\chi^2<$1.5 for V$>$ 24 mag and $\chi^2<$2.5 for brighter stars are shown in the figure. 
%Confirmed variable stars are plotted as filled red circles, candidate variabels as blue a green filled circles. 
%The photometric data generating the CMDs
%%% in Figure~\ref{f:fig4} 
%%%and the  
%%%time-series data for the 4 confirmed variables, 
%are available in electronic form upon
%request.
%%%%%% from the first author.
%%The solid and dashed lines in Figure~\ref{f:figcmd} are, respectively, the mean ridge lines of the Galactic GCs M68 
%%%({\it solid line}) 
%%and M3
%({\it dashed line}) 
%drawn from the CMD by \citet{wa94} for M68 and \citet{buo94} for M3, shifted in magnitude and color 
%%Superimposed over the CMD of CVn\,I 
%%In  Fig. 4{\it b} we have plotted in red stars of the Galactic globular cluster
%M68, from \citet{wa94}, shifted in magnitude (by $-6.58$  mag) and color (by 
%%$-0.04$ mag) 
%to match the CVn\,I 
%horizontal and red giant branches {\bf (XXXXX Le mettiamo?)}

%%%\begin{figure*}
%%%\includegraphics[scale=.60]{pl_ell_last.ps}
%%%\includegraphics[scale=.90]{pl_ell_last.ps}
%%\includegraphics[scale=.90]{f4.eps}
%%\realfigure{cmd3_paper_last.ps} 
%%{$V,B-V$ CMDs of the Canes Venatici I dwarf spheroidal galaxy obtained
%%with the WHT 4.2m telescope in three different annular regions of the galaxy.
%%Only stars with
%%$\sigma_{V}$, $\sigma_{B} \leq 0.10$ mag, $\chi \leq$ 0.2, and $\mid SHARP \mid \leq $ 0.5
%%are displayed. Plotted in red are stars of the Galactic globular cluster
%%M68, after \citet{wa94}.
%%%%Candidate variable stars are marked as cyan circles, 
%%%%the RRab and the RRc stars are marked as red and blue circles, respectively, and the potential Anomalous Cepheids 
%%%%are marked as magenta circles.
%%}{f:fig3}

%%Gisella%\realfigure{pl_ell_last.ps} 
%%\begin{figure*}
%%%%%\includegraphics[scale=.60]{pl_ell_last.ps}
%%\includegraphics[scale=.90]{pl_ell_last.ps}
%%\caption{$V,B-V$ CMDs of the Canes Venatici I dwarf spheroidal galaxy obtained from stars
%%in the whole 16.2 $\times$ 16.2 arcmin$^2$ field covered by the 
%% WHT observations (Fig. 1{\it a});  and in the 3 separate regions 
%% corresponding to the 
%% black ellipse (Fig. 1{\it b}); the intermediate region between ellipse and
%% blue circle (Fig. 1{\it c}); and the region outside the blue circle (Fig. 1{\it d}) of Figure~\ref{f:fig3} .
%%%%
%%%%
%%%%
%%%%obtained
%%%%with the WHT 4.2m telescope in three different annular regions of the galaxy.
%%%%%Only stars with
%%%%%$\sigma_{V}$, $\sigma_{B} \leq 0.10$ mag, $\chi \leq$ 0.2, and $\mid SHARP \mid \leq $ 0.5
%%%are displayed. 
%%Plotted in red are stars of the Galactic globular cluster
%%M68, after \citet{wa94}.
%%%%Candidate variable stars are marked as cyan circles, 
%%%%the RRab and the RRc stars are marked as red and blue circles, respectively, and the potential Anomalous Cepheids 
%%%%are marked as magenta circles.
%%}%%%%gisella${f:fig4}
%%\label{f:fig4}
%%\end{figure*}

The CMD of B514 (see Figure~1) reaches $V \sim $ 28 mag and is very rich in stars. 
It has well-populated  
horizontal and red giant branches.  The HB stretches across the RR Lyrae 
instability strip, which is entirely
filled by the large number of confirmed and candidate RR Lyrae stars, and extends 
significantly to the blue through a blue tail that reaches $V \sim 27$ mag at $B-V \sim $0.1 mag. 
The red giant branch (RGB) is a prominent feature of the 
%CVn\,I 
CMD, and does not exhibit significant scatter, thus ruling out a metallicity spread in B514.
%
%({\bf Qui va detto che troviamo le variabili RR Lyrae vere fino ad una distanza di 93 arcsec dal centro
%dell'ammasso, questo vuol dire che l'amamsso e' estremamente esteso, quindi si puo' riprendere il discorso che sia una
%galassia.) L'ABBIAMO DETTO PRIMA ... NON SERVE RIPETERE}
%
%%({\bf Questo viene da CVnI, qui ci vanno invece i conteggi tra i vari rami, il tipo di Lee-Zinn etc.}).
%%Its width suggests 
%%the existence of a composite population in CVn\,I, with stars having some spread 
%%in metallicity and$/$or age. 
%%The CMD becomes very crowded below $V$ = 24 mag, but nevertheless shows hints 
%%of a young main 
%%sequence at $B-V \sim$ 0.2 mag, thus providing support for de Jong et al.'s 
%%(2007)
%%%%%\citet{dj07} 
%%earlier suggestion. 
%%From the average luminosity of the HB ($V_{HB} \sim 22.2$ mag),
%%the turnoff of the old stellar population is estimated to lie a few tenths below 
%%the limiting magnitude
%%reached by our photometry, as also shown by the comparison with 
%%%the mean ridge lines of 
%the Galactic globular clusters 
%%M68
%%% ({\it solid line}) 
%%and M3.
% ({\it dashed line}). 
%Contamination by field stars ...... ({\bf Questa va tutta discussa avendo come riferimento
%il CMD del campo esterno}).
%
%%and background galaxies is present in Fig. 4{\it a}.
%%Source Extractor (Sextractor, \citealt{ber96}) was run on the WHT data, and the morphological 
%%parameters of the detected sources were used to discriminate between stars and background galaxies. 
%tWe found that brighter than $V$=24 mag, more than 95\% of the 
%%sources 
%%%displayed in Figure~\ref{f:fig4} 
%%are bona-fide stars. Among them, contaminating 
% %both the left and right panels of Figure~\ref{f:fig3}, 
%with
%%stars from the MW disk dominate for $B-V >$ 1.2 mag, while stars from the 
%%Galactic halo may 
%%contaminate the CVn\,I CMD at bluer colours.
%t%%
%%%The half-light radius of CVn\,I is  $r_h$= $8.5^{\prime} \pm 0.5 ^{\prime}$ (\citealt{zu06}). 
%%Since the field of
%%view covered by our observations does not extend beyond $ \sim 8.9^{\prime}$, we 
% do not have a control field devoid of CVn\,I stars 
%%to discuss the field contamination by MW stars properly. However, synthetic CMDs of the MW field at the 
%%position of CVn\,I show that a large fraction of the bright stars at $V \sim 20$ 
%%mag and $B-V \sim 0.4 - 0.5$ mag in  the galaxy CMD 
%tmay be accounted for by MW halo stars
%%% and background galaxies 
%%(M. Cignoni, private 
%%communication).
% %In order to minimize 
%%Contamination 
%%by field stars 
%%is also minimized in 
%t%and
%%%to take into account the elongated structure of CVn\,I, in 
%%Fig. 4{\it b}, where we have
%%considered only stars within the 
% %black 
%%ellipse to take into account the 
%%elongated structure of CVn\,I.
%%%that are within 4.5 arcmin from the galaxy center. 
%tThe main features of the galaxy CMD, including 
%%the blue plume of a young stellar component, shows up much more clearly in Fig. 
%%4{\it b}. The ble plume becomes increasingly
%%prominent moving outward (see Figs. 4{\it c} and  4{\it d}). 
% %The contamination by the MW disk is also significantly reduced in Fig. 4{\it b}. 
%{\it Risistemare la parte che segue ....
%
%Adopting for the reddening of M68 $E(\bv)=0.07 \pm$0.01 mag (\citealt{wa94}), 
%and for M3 $E(\bv)=0.01 \pm$0.01 mag (\citealt{ha96}), 
%the color shifts
%required to match the B514 HB to those of M68 and M3 thus imply a reddening 
%$E(\bv)=0.03 \pm$0.02 mag
%for B514.
%%
%the 
%$-$0.04 mag color shift
%required to match the CVn\,I and M68 CMDs implies a reddening 
%E(B-V)=0.03$\pm$0.02 mag
%for CVn\,I. 
%This is slightly largerXXXXX than the 0.014 $\pm$ 0.026 mag value derived 
%for the galaxy from the \citet{sc98} 
%maps.
%%%%The width of the RGB suggests 
%%%%the existence of a composite population in CVn\,I, with stars having some spread in metallicity and$/$or age. 
%The RGB of M68 provides an excellent fit to B514I, implying that the cluster
%has 
%%dominant old ($t \sim 13$ Gyr) stellar population with 
%metallicity close 
%to that of M68: ${\rm [Fe/H]}=-2.1$ or $-2.0$ dex on the 
%\citet{zw84} 
%and \citet{cg97} scales, respectively.}
%%%On the other hand, the M3 RGB is by far too red to 
%%%match that of CVn\,I, which excludes any metallicity spread as large as
%%%0.5 dex or larger in CVn\,I, since the metallicity of M3 is ${\rm [Fe/H]}=-1.6$ or $-1.3$ dex on the \citet{zw84} 
%%%and \citet{cg97} scales, respectively. 
%%%Recent spectroscopic analysis of stars in CVn\,I \citep{ib06,ma07b} distinguished 
%%%two separate components in CVn\,I
%of the galaxy, a kinematically hot component 
%%%with $-2.5 < {\rm [Fe/H]} <  -2.0$ dex and 
%%%%%a kinematically 
%%cool component with 
%%%$-2.0 < {\rm [Fe/H]} < -1.5$ dex, respectively, on the \citet{cg97} scale.  
%%%%%The hot, metal poor component 
%%agrees with our results for the main CVn\,I population. 
%%%These results 
%%%%%of \citet{ib06} have been 
%%%were contested by \citet{sg07}, 
%%%who found no evidence for a second metallicity component 
%population 
%%%in CVn\,I, based on a sample of stars three times larger 
%%%than that considered by \citet{ib06} and \citet{ma07b}.   
%%%Using the \citet{ru97} technique (which is consistent with the 
%%%%%%\citet{cg97} 
%%%Carretta \& Gratton 1997 metallicity scale), \citet{sg07} obtained 
%%%${\rm [Fe/H]}=-2.09\pm0.02$ dex, with dispersion $\sigma _{\rm [Fe/H]}$= 0.23 
%%%dex. This metal abundance is 
%%%in good 
%%%agreement with the metallicity we infer from the comparison with M68.
%%%Our CMD and the comparison with M68 and M3 does not provide evidence in favor of two 
%%%separate components with
%%%differences in metallicity as large as claimed by \citet{ib06} and \citet{ma07b} 
%%%in CVn\,I. In order to investigate 
%%%this point further,  
%%%and to possibly disentangle the age and the metallicity effects, we have fitted 
%%%isochrones 
%%%from the PISA 
%%%database\footnote[12]{http://astro.df.unipi.it/SAA/PEL/Z0.html} \citep{car04}
%%%to the CMD of CVn\,I
%%%in Fig. 4{\it a}, varying the metallicity from $Z$=0.0002 to 
%%%$Z$=0.0004 (this upper limit being set by the ACs) and 
%%%the age from 13 to 0.6 Gyr.
%%%Results of the best fit are shown in Figure~\ref{f:fig5}, where we also plot the 
%%%variable stars in different symbols. 
%%\realfigure{fig4.ps}
%%%%\realfigure{f5.ps}
%%%%{Best fit of the CVn\,I CMD in Fig. 4{\it a}, using isochrones from the Pisa dataset 
%%%%with $Z$=0.0002 ([Fe/H]=$-$2.0 dex),
%%%%and 4 age components; 13 Gyr ({\em red line}), 5 Gyr ({\em blue line}), 1.5 Gyr ({\em green line}), and
%%%%0.6 Gyr ({\em black line}). The CVn\,I variable stars are plotted with different symbols: red, RRab stars; blue, RRc stars;
%%%%cyan, candidate variables for which we were not able to derive reliable periods; purple, candidate ACs.
%%%%Typical error bars of the photometry are provided on the left-hand side.}{f:fig5}
%%The RRab and RRc stars are red and blue dots, respectively, cyan circles 
%%are candidate
%%variables for which we were not able to derive reliable periods, most of them lie 
%%on the galaxy HB, hence are very likely RR Lyrae stars. Finally, the candidate ACs are marked 
%%as purple circles. 
%%%The best-fit procedure does not favor significant metallicity spreads among the 
%%%CVn\,I stars. The galaxy CMD and its variable stars 
%%are best reproduced by the superposition of at least 2 and possibly up to 4 subsequent 
%%generations of stars 
%%with roughly the 
%%same metal
%%abundance, $Z$=0.0002 ([Fe/H]=$-$2.0 dex). They include:  a 13 Gyr component 
%%(red isochrone) accounting for the redder RGB, the HB and the large number of RR Lyrae stars; 
%%a 0.6 Gyr component 
%%(black isochrone) producing the bluest part of the blue plume and the ACs; and possibly
%%two intermediate age components: a 
%%5 Gyr population (blue isochrone) 
%%producing the bluer RGB and the fainter portion of the red clump; and a 1.5 Gyr stars 
%%(green isochrone) providing part of the
%%blue plume and the brighter portion of the red clump.
%%%%%%; and, finally, a 0.6 Gyr 
%%%%%%component 
%%%%%%(black isochrone) producing the bluest part of the blue plume and the ACs.
%% A 
%%deeper CMD is needed to
%%fully confirm this interpretation. 
%%%%
%%%%Fig. 1{\it b} shows the CMD only of stars that are within 4 arcmin of the center in order 
%%%%to minimize contamination by field stars, superimposed over the CMD of the Galactic globular cluster
%%%%M68 (from \citep{wa94}).
%%%%
%%\begin{figure}
%%\plotone{cmd3_new.ps}
%%\caption{$V,B-V$ CMD of the Canes Venatici I dwarf spheroidal galaxy obtained
%%with the WHT 
%%4.2m telescope in three different annular regions of the galaxy.  
%%%%The RRab stars are marked as red crosses, the RRc stars are
%%%%marked as blue triangles, and the potential Anomalous Cepheids are marked as purple squares.
%%}
%%\end{figure}
%%
%%
%%the CMD for CVn-I from the WHT and WIRO telescopes superimposed over the CMD for M68.  
%%In Figure 2 we plot only the stars that are within 4.5 arcmin of the center of each object in order 
%%to minimize contamination by field stars.  
%%These CMDs confirm that the dominant population in CVn\,I is old.  
%% The scatter in the red giant branch (RGB) of CVn\,I suggests 
%%the existence of a composite population with stars of different metallicity and/or age in the galaxy.
%of a metallicity dispersion in the galaxy.
%
%Indeed, a recent spectroscopic analysis of the stars in CVn\,I \citep{ib06,ma07} distinguished two separate components 
%of the galaxy, a kinematically hot component with $-2.5 \langle [Fe/H] \langle -2.0$ and a kinematically 
%cool component with $-2.0\langle [Fe/H]\langle -1.5$ on the \citet{cg97} scale. The hot, metal poor component 
%agrees with our results for the main CVn\,I population. The results of \citet{ib06} are contested by \citet{sg07}, 
%who found no evidence for a second population in CVn\,I, but did find evidence for a metallicity scatter.  
%Using the method of \citet{ru97}, \citet{sg07} obtained $[Fe/H]=-2.09\pm0.02$, which is consistent with our 
%inferred metallicity.  Our CMDs do not provide firm evidence for two populations of distinct metallicity in 
%CVn\,I, but the spread in the width of the RGB is consistent with some spread in metallicity and or age.
%In order to discuss this point further we have superposed isochrones to the CMD in Fig. 1{\it a}, see 
%Figure~\ref{f:fig4}. 
%
% 
%
%In this diagram the variable stars have been plotted in different symbols.
%The RRab and RRc stars are plotted 
%in the CMD in Figure 1{\it a} as red and blue dots, respectively, cyan circles are candidate
%variables for which we were not able to derive reliable periods, most of them lie 
%on the galaxy HB, hence are very likely RR Lyrae stars. Finally, candidate ACs are marked as magenta circles.
%
%
%
%%\begin{figure}
%%\plotone{cmd1_paper.ps}
%%\caption{Tracce}
%%\end{figure}

%\section{An Improved Distance Estimate for CVn\,I}
The mean magnitude of the B514 RR Lyrae stars is 
${\rm \langle V\rangle}$ = 25.18 $\pm 0.02$ mag 
(with a dispersion of 0.16 mag among the 81 stars). We adopt an absolute 
magnitude of $\rm{M_{V}}=0.44\pm0.05$ mag for RR Lyrae stars with the metallicity 
$\rm{[Fe/H]}=-1.95\pm0.1$ dex of B514 \citep{clem03}, which is consistent with an  
LMC distance modulus of 18.52. Using the reddening  value 
of $E(\bv)$=0.07$\pm$0.02 estimated from \citet{sc98},  
% inferred from the 
%comparison with M68.
%  We assume
%a reddening for CVn\,I of $\rm{E(B-V)}=0.014 \pm 0.026$ mag \citep{sc98}, with 
%consequent absorption in the 
%$V$ band of 
%about 0.04 mag.  
we find a distance modulus of $\mu_{0}=24.52\pm 0.08$ mag, 
%$\mu_{0}=21.67\pm0.06$ mag, 
which corresponds to a distance of about 800 $\pm$ 30 kpc, in good agreement  
% $d=783.4^{+XXX}_{-XXXX}~\rm{kpc}$.
%$d=216^{+7}_{-5}~\rm{kpc}$.  
with the distance 
%of $XXXX^{+XXXX}_{-XXXX}~\rm{kpc}$  
adopted for this cluster by \citet{gal06}.
%, which is also based on the \citet{sc98} reddening. 
%If we adopt instead the value of $E(B-V)$=0.03 $\pm$ 0.02 mag inferred from the 
%comparison with M68 and M3, 
%we obtain a distance modulus of $\mu_{0}=21.62\pm 0.06$ mag, and in turn a 
%distance of 
%$d=210^{+7}_{-5}~\rm{kpc}$.
%
%{\it To match the CVnI CMD with M68 we had to shift M68 by -0.03 mag in E(B-V),
%since the reddening of M68 is E(B-V)=0.07+/-0.02 mag, the match is obtained
%if the reddening of CVnI is 0.04 mag this is slightly larger than the 0.014 mag value
%(from Schlegel et al.)  you have assumed in Section 5.
%Adopting E(B-V)=0.04 mag reduces the distance modulus of CVnI to 21.58 corresponding to
%D=207 kpc. Within the errors this is still in agreement with previous estimates
%(Zucker et al. and the LBT paper, that both adopt  0.014 mag).
%I suggest you use both reddening values the Section 5.}
%


\section{Conclusions}
We have identified and obtained periods and light curves for 82 RRab stars and 7 RRc 
stars in the globular cluster B514 of the Andromeda galaxy. 
%and identified further XXX candidate variables, very likely RR Lyrae stars.  
%We also identified three potential ACs and 58 additional 
%candidate variable stars that according to their 
%position on the galaxy CMD are very likely RR Lyrae stars.  
The average period of the B514 RRab stars for which we have complete and reliable 
light curves and their location on the period-amplitude diagram 
indicate likely OoI-type characteristics (see right side of Fig. \ref{f:figpa}), 
however the cluster's  low metallicity is more typical of an OoII-type. 
%
%%
%suggest that B514  is a somewhat 
%borderline OoI cluster. 
Thus B514 seems to follow a different rule than what is found in the MW, where 
metal-poor ([Fe/H]$\lesssim-1.7$) GCs containing RR Lyrae stars have Oosterhoff II type.
%These results are obviously not conclusive and the entire sample of Cycle 15 data needs to be 
%carefully analyzed before reaching any definitive conclusion (\cite{contreras09});  
This may suggest that B514 is indeed a somewhat peculiar cluster, as indicated by 
independent evidence of some similarity with peculiar clusters in the MW such 
as $\omega$ Cen, M54 and NGC2419 (\citealt{fed07}). 
Alternatively, we are seeing an indication that the M31 GCs have different RR Lyrae pulsation 
characteristics than that seen in the main body of the MW GCs. 
%however, the possibility that the GCs in M31 are different from those of the MW 
%in terms of RR Lyrae pulsational properties begins shaping out.  
%, and a much stronger statistical sample is needed to either confirm 
%or disproof it. 
 A more detailed analysis will be done  based on the entire sample 
of M31 clusters observed in our Cycle 15 program, and the results will be presented  in a 
forthcoming  paper (Contreras et al. 2010).
%
%A more detailed analysis will be done with the data, and the results will be presented  in a 
%forthcoming  paper (Contreras et  al. 2009).



\bigskip
%%%Acknowledgments
%%We thank 
%Michael Pierce for assistance with the WIRO Prime camera.
\acknowledgments  
We warmly thank the Program Coordinator A. Roman, and the Contact Scientist M. Sirianni, of our HST program for their 
invaluable help with the Phase II and scheduling of the HST observations. This research was partially supported by 
COFIS ASI-INAF I/016/07/0.
HAS and BP thank the Space Telescope Science Institute for support under grant
HST-GO-11081.05-A.
% K.K. greatfully thanks .....
% and the NSF for support under grant AST-0307778. G.C. acknowledges support by PRIN-INAF 2006 (PI G. Clementini).  
M.C. is supported by Proyecto Fondecyt Regular 1071002, by Proyecto Basal PFB-06/2007, 
by FONDAP Centro de Astrof\'{i}sica 15010003, and by a John Simon Guggenheim Memorial Foundation 
Fellowship.


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%%\bibitem[Buonanno et al. (1994)]{buo94} Buonanno, R., Corsi, C.E., Buzzoni, A., Cacciari, C., 
%%Ferraro, F.R., \& Fusi Pecci, F. 1994, \aap, 290, 69 
\bibitem[Brown et al. (2003)]{bro03} Brown, T.M., et al. 2003, \apj, 592, L17 
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ed.s D.W. Kurtz \& K.R. Pollard (San Francisco: ASP), ASP Conf. Ser., 310, 113
\bibitem[Catelan (2009)]{cat09} Catelan, M. 2009, Ap\&SS, 320, 261 %in press (arXiv:astro-ph/0507464) 
\bibitem[Clement et al. (2001)]{cle01} Clement, M.C. et al. 2001, \aj, 122, 2587
\bibitem[Clement \& Rowe (2000)]{cle00} Clement, M.C., \& Rowe, J. 2000, \aj, 120, 2579 
\bibitem[Clementini et al.(2000)]{clem00} Clementini, G., et al. 
%Di Tomaso, S., Di Fabrizio, L., Bragaglia, A., Merighi, R.,
%Tosi, M., Carretta, E., Gratton, R.~G., Ivans, I.I., Kinard, A., Marconi, M., 
%Smith, H.~A.,  Wilheim, R., Woodruff, T. \& Sneden, C. 
2000, \aj, 120, 2054

\bibitem[Clementini et al.(2001)]{clem01} Clementini, G., et al. 2001, \aj, 120, 2579 
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%%\bibitem{} Rich et al. 2005, AJ.129.2670
\bibitem[Schlegel et al.(1998)]{sc98} Schlegel, D.J., Finkbeiner, D.P., \&
Davis, M. 1998, \apj, 500, 525
%%\bibitem[Stetson(1987)]{st87} Stetson, P.B. 1987, \pasp, 99, 191
%%\bibitem[Stetson(1992)]{st92} Stetson, P.B. 1992, in ASP Conf. Ser. 25,
%%Astronomical Data 
%%Analysis Software and Systems I, ed. D.M. Worrall, C. Biemesderfer, \& J.
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\end{thebibliography}


%{\it NIENTE TABLE 1 SECONDO ME (CC).} 


%%  \begin{table*}
%%\tiny
%%  \small
%   \fontsize{6}{6}
%%      \caption[]{Identification and properties of the RR Lyrae stars shown in  Figure~\ref{f:figlc}.}
%%%%	   in the CVn~ I dSph
%%%%	  galaxy}
%%	 \label{t:bootes_var}
%%     $$
%%	 \begin{array}{lcclllccrr}
%%	    \hline
%%	    \hline
%%	   \noalign{\smallskip}
%%	   {\rm Name} &  {\rm \alpha } & {\rm \delta} &  {\rm Type} &~~~~{\rm P} & 
%%	    ~~~{\rm Epoch(max)}  & {\rm \langle V\rangle}  & {\rm \langle I\rangle}  & {\rm A_V}~~ & {\rm A_I}~~ \\
%%	    ~~  &{\rm (2000)}& {\rm (2000)}& & ~{\rm (days)}& (~~$-$2450000) &\tablenotemark{a} & \tablenotemark{a} 
%%	     &{\rm (mag)}  &{\rm (mag)} \\
%%	    \noalign{\smallskip}
%%	    \hline
%%	    \noalign{\smallskip}
%%	    
%%{\rm ~V487} & 00~31~10.45 & +37~54~01.32 & {\rm RRab }    &0.50947 &~~~~3570.8676   & XX.X & XX.X &X.XX&X.XX\\
%%{\rm ~V520} & 00~31~10.01 & +37~54~03.62 & {\rm RRab }    &0.57348 &~~~~4264.355~   & XX.X & XX.X &X.XX&X.XX\\
%%{\rm ~V527} & 00~31~09.57 & +37~53~50.40 & {\rm RRc }	  &0.299723&~~~~3571.041~   & XX.X & XX.X &X.XX&X.XX\\
%%{\rm ~V534} & 00~31~09.34 & +37~53~50.44 & {\rm RRc }	  &0.41012 &~~~~4263.729~   & XX.X & XX.X &X.XX&X.XX\\
%%\hline
%%	    \end{array}
%%	    $$
%\begin{list}{}{}
%Table~1 is presented in its entirety in the electronic edition of the 
%Astrophysical Journal.\\
%%\tablenotetext{a}{${\rm \langle V\rangle}$ and ${\rm \langle I\rangle}$ values are 
%%intensity-averaged mean magnitudes.}
%%\par\noindent
%% A portion is shown here 
%%for guidance regarding its form and content.\\
%%\end{table*}


\begin{figure*}
%\includegraphics[width=16.3cm,clip]{4panVV-I.eps}
%%\includegraphics[width=16.3cm,clip]{cmd_acs_4pan.eps}
%\includegraphics[width=16.3cm,clip]{cmdfigland1.eps}
\includegraphics[width=16.3cm,clip]{f1.ps}
%%\realfigure{4panVV-I.eps}
\caption{$V, V-I$ CMD of B514 in 4 regions with increasing the distance from the cluster 
center which was set at R.A.= 00$^h$ 31$^m$ 09$^s$.83, 
decl.= 37$^{\circ}$ 53$^{\prime}$ 59$^{\prime \prime}$.6  (J2000), based on our reductions of the ACS 
archive photometry.  
% of 30 WFPC2 images. 
Bona-fide RR Lyrae
stars are marked by filled red circles, candidate variable stars by blue and green filled circles (see Section 3).
}
\label{f:figcmd}
\end{figure*}


\begin{figure*}
\centering
%%\includegraphics[width=14.0cm,clip]{mappa_finale1.ps} 
%%\includegraphics[width=11.0cm,clip]{mappa_finale1_small.ps} 
%\includegraphics[width=13.5cm,clip]{mappa_finale1.ps} 
\includegraphics[width=13.5cm,clip]{f2a.ps} 
%%\includegraphics[width=10.5cm,clip]{mappa_finale1_small.ps} 
%%\includegraphics[width=8.5cm,clip]{mappa_finale1_small.ps}
\includegraphics[width=8.5cm,clip]{f2b.ps}
%\realfigure{isto.B514.ps}
\caption{{\it Upper panel:} Location of B514 confirmed (red circles) and candidate (blue and green circles) variable stars 
on a  $3^{\prime}$ 22$^{\prime \prime} \times 3^{\prime}$ 22$^{\prime \prime} $ map of the cluster, corresponding to the field of 
view covered by the ACS observations of HST GO 10565 (see \citealt{gal06}). Also shown are the field of 
view covered by the ACS observations of HST GO 10394 (see \citealt{mck07}; tilted square), and the field of view of our 
WFPC2 observations. The two red circles correspond to radii of $r = 50^{\prime \prime}$ and $r = 100^{\prime \prime}$ from 
the center of B514.
{\it Lower panel:}  Enlargement of the variable stars' map showing a 
$30^{\prime \prime} \times 30^{\prime \prime}$ region centered on the cluster. 
}
\label{f:figisto}
\end{figure*}



\begin{figure*} 
%\includegraphics[width=16.3cm,bb=43 170 570 560,clip]{cdlab.ps}
%\includegraphics[width=16.3cm,bb=43 170 570 560,clip]{cdlc.ps}
%\includegraphics[width=16.3cm,clip]{cdlab.ps}
\includegraphics[width=16.3cm,clip]{f3a.ps}
%\includegraphics[width=16.3cm,clip]{cdlab.ps}
\includegraphics[width=16.3cm,clip]{f3b.ps}
\caption{$V$ (left panels) and $I$ (right panels) light curves of RR Lyrae stars identified in B514.
{\it Two upper rows:} fundamental-mode pulsators: {\it Two lower rows:} first-overtone pulsators. 
Filled and open circles indicate WFPC2 and ACS data, respectively. Typical error of the single data point 
at the magnitude level of the HB is about 0.06 mag. }
\label{f:figlc}
%\end{figure}
\end{figure*}

%\begin{figure}
%\includegraphics[width=16.3cm,clip]{isto.B514.ps} 
%%\realfigure{isto.B514.ps}
%\caption{Period histogram for the confirmed RR Lyrae stars in B514.}
%\label{f:figisto}
%\end{figure}
%
%

\begin{figure}
%\includegraphics[width=16.3cm,clip]{pab514posternew.ps}
\includegraphics[width=16.3cm,clip]{f4.ps}
%\realfigure{pab514posternew.ps}
\caption{Period-amplitude diagram in the $V$ band. RRab variables are shown by 
filled circles, RRc stars by open circles. 
The linear relations show the period-amplitude distributions of 
Galactic Oosterhoff type I and II clusters (\citealt{cle00}).   
The quadratic relations show the \emph{bona fide} regular 
and  evolved RRab stars in M3, from \citet{cac05}, for comparison; 
analogous relations for the RRc stars are not reported 
because of the small number of these stars so far detected in B514.  
}
\label{f:figpa}
\end{figure}


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%%Stellar Candles for the Extragalactic Distance Scale, ed. D. Alloin \& W.Gieren
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%%Irwin, M.,\& 
%%Lewis, G.F. 2007b, \mnras, submitted (astro-ph/0705.4622)
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%\clearpage

%%\realfigure{f1.eps}
%%{$V$ and $B$ light curves of variable stars in CVn\,I.
%%$Top:$ RRab star with $P$=0.63 days.
%%$Middle:$ RRc star with $P$=0.40 days.  $Bottom:$ candidate Anomalous Cepheid 
%%with a possible 
%%period of 1 day.}{f:fig1} 

%\clearpage

%%\realfigure{f2.eps}
%%{Period-amplitude diagram in the $V$ band for the CVn\,I RR Lyrae stars. 
%%RRab stars are indicated by crosses and RRc stars by triangles.  The solid
%%and dashed lines are the positions of OoI and OoII
%%Galactic GCs from \citet{cr00}. 
%%% The location of the majority of the RRab
%stars between the OoI and OoII lines suggests that CVn\,I is an Oosterhoff intermediate object.
%%}{f:fig2}
%%
%%\clearpage

%\realfigure{xy_s_arc1.ps} 
%%\realfigure{f3.eps} 
%%{Smoothed 
%%%X,Y 
%%map of the CVn\,I stars in the field of view of the WHT observations, in 
%%differential 
%%R.A. and DEC (in arcmin) from the  galaxy center which was set at
%%  RA(J2000)= 33$^h$ 28$^m$ 02$^s$,
%\DEC(J2000)=33$^o$ 33$^\prime$ 40$^{\prime\prime}$. North is up and East to the left. 
%%The bulk of the
%%CVn\,I stars is within the %black 
%%ellipse which has semi-major axis $r$= 6.7 
%%arcmin and ellipticity $e$=0.55. The 
%%%blue
%%circle has a radius of $r$ = 7 arcmin. Confirmed RR Lyrae stars are displayed by open circles, candidate ACs
%%  by crosses. One of the ACs lies about half an arcmin outside the map, in the East direction.  
%\}{f:fig3}
%%
%%\clearpage
%%
%%\begin{figure*}
%%%%%\includegraphics[scale=.60]{pl_ell_last.ps}
%%%%%\includegraphics[scale=.90]{pl_ell_last.ps}
  %%\includegraphics[scale=.90]{f4.eps}
%\%%\includegraphics[scale=.90]{cmd4.ps}
%%\includegraphics[scale=.90]{f4.eps}
%%\caption{$V,B-V$ CMDs of the CVn\,I dSph obtained 
%%from stars
%%in the 16.2 $\times$ 16.2 arcmin$^2$ field covered by the 
%% WHT observations (Fig. 4{\it a});  and in 3 separate regions 
%% corresponding to the 
   %black 
%\ ellipse (Fig. 4{\it b}); the intermediate region between ellipse and
%%%blue
%% circle (Fig. 4{\it c}); and the region outside the
%% %blue
%%  circle (Fig. 4{\it 
%%d}) of Figure~\ref{f:fig3}.
%% Confirmed variable stars are plotted in different colors. {\it Red circles}: ab-type RR Lyrae stars;
%%  {\it blue circles}: c-type RR Lyrae stars; {\it green circles}: potential Anomalous Cepheids.
%\%;
%%%{\it green circles}: candidate variable stars for which we were not able to derive reliable periods.
%%The solid and dashed lines are the mean ridge lines of M68 and M3, shifted in magnitude and adjusted in reddening 
%%to fit the galaxy HB.
%%
%%
%%
%%obtained
%%with the WHT 4.2m telescope in three different annular regions of the galaxy.
%%%Only stars with
%%%$\sigma_{V}$, $\sigma_{B} \leq 0.10$ mag, $\chi \leq$ 0.2, and $\mid SHARP \mid \leq $ 0.5
%%%are displayed. 
%%Plotted in red are stars of the Galactic globular cluster
%%M68, after \citet{wa94}.
%%Candidate variable stars are marked as cyan circles, 
%%the RRab and the RRc stars are marked as red and blue circles, respectively, and the potential Anomalous Cepheids 
%%are marked as magenta circles.
%%}%%%%gisella${f:fig4}
%%\label{f:fig4}
%%\end{figure*}

%\\clearpage
%%
%%%%\realfigure{cmd5.ps}
%%\realfigure{f5.eps}
%%{Best fit of the CVn\,I CMD in Fig. 4{\it a}, using isochrones from the Pisa 
%%dataset 
%%with $Z$=0.0002 ([Fe/H]=$-$2.0 dex),
%%  and 4 age components; 13 Gyr ({\em red line}), 5 Gyr ({\em blue line}), 1.5 Gyr 
%\({\em green line}), and
%%0.6 Gyr ({\em black line}). The CVn\,I confirmed variable stars are plotted with 
%%the same symbols as in 
%%Figure~\ref{f:fig4}. 
%different 
%symbols: red, RRab stars; blue, RRc stars;
%%Candidate variables 
%%%for which we were not able to derive reliable periods 
%%are marked
%%  by cyan circles. 
%\Typical error bars of the photometry are provided on the left-hand 
%%side.}{f:fig5}
%%
%%%\realfigure{f5.eps}

%% \begin{figure}
%\plotone{cvnI_ltcurves.eps}
%\caption{$V$ and $B$ light curves of variable stars in CVn\,I.  $Top:$ RRab star.
%$Middle:$ RRc star.  $Bottom:$ Potential anomalous Cepheid.}
%\end{figure}
%
%\begin{figure}
%\plotone{cvn_period_amp.ps}
%\caption{Period-amplitude diagram in the $V$ band for the CVn\,I RR Lyrae stars. 
% RRab stars 
%are indicated by blue crosses and RRc stars are indicated by purple triangles.  The solid
%and dashed 
%lines are the positions of Oosterhoff type I (OoI) and Oosterhoff type II
%(OoII) Galactic 
%Globular Clusters from \citet{cr00}.  The location of the majority of the RRab
%stars between 
%the OoI and OoII lines indicates that CVn\,I is an Oosterhoff intermediate
%object.}
%% \end{figure}
%
%
%\begin{figure}
%\plotone{cmd3_new.ps}
%\caption{$V,B-V$ CMD of the Canes Venatici I dwarf spheroidal galaxy obtained
%with the WHT 
%4.2m telescope in three different annular regions of the galaxy.  
%%%The RRab stars are marked as red crosses, the RRc stars are
%%marked as blue triangles, and the potential Anomalous Cepheids are marked as purple squares.
% }
%\end{figure}
%
%\begin{figure}
%\plotone{cmd1_paper.ps}
%\caption{Tracce}
%\end{figure}
%
%
%%\begin{figure}
%\plotone{cvni_metallicity.ps}
%\caption{The combined CMD for CVn-I from the WIRO and WHT telescopes
%superimposed on the CMD 
%for M68 with only the stars within 4.5 arcmins of the center of each object
%plotted.  Data for M68 from \citet{wa94} shifted by 6.50 mag in $V$. The reddenings of M68 and
%CVn-I are similar.  }
%%\end{figure}

\end{document}

0909.3303.extracted_bib
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