You are an expert at summarizing long articles. Proceed to summarize the following text: 
a small , but growing , number of galactic globular clusters exhibit a star - to - star variation in the relative abundances of the heavy elements . @xmath0 centauri is the most well - known member of this group with its stars spanning a range in metallicity = @xmath6 from [ fe / h ] @xmath3 @xmath22.0 to [ fe / h ] @xmath3 @xmath20.5 ; for certain elements , the abundance ratios with respect to iron , [ x / fe ] , exhibit considerable variations with metallicity ( e.g. , @xcite ) . as the most massive galactic globular cluster and in light of its complex chemical enrichment history , @xmath0 cen is regarded to be the core of a disrupted dwarf galaxy ( e.g. , @xcite ) . m54 is the second most massive galactic globular cluster . it displays a key characteristic shared by @xmath0 centauri but absent in the majority of clusters , namely , a metallicity dispersion @xcite , albeit of smaller amplitude than that found in @xmath0 centauri . that m54 is the nuclear star cluster of the sagittarius dwarf spheroidal galaxy lends further support to the hypothesis that massive globular clusters with metallicity variations may be the nuclei of disrupted dwarf galaxies ( although @xcite argue that the nucleus of sgr likely formed independently of m54 ) . when considering the ensemble of globular clusters with unusual chemical abundance ratios cen and m54 , the other clusters include m15 @xcite , ngc 362 @xcite , ngc 1851 @xcite , ngc 2419 @xcite , ngc 3201 @xcite , ngc 5824 @xcite , ngc 6656 @xcite , ngc 7089 @xcite and terzan 5 @xcite ] ( dispersions in metallicity and/or neutron - capture elements ) , it is clear that these objects are preferentially the more luminous , and therefore the more massive , clusters . @xcite considered globular clusters with an extended horizontal branch ( i.e. , a horizontal branch with extremely blue stars ) which likely signifies the presence of he abundance variations @xcite . they argued that not only are clusters with an extended horizontal branch preferentially more massive , but also when considered together the clusters have different kinematics from other groupings of the galactic globular cluster population . the sample of clusters with extended horizontal branches include @xmath0 cen , m54 and m22 , all of which exhibit metallicity variations . @xcite showed that such clusters had kinematics consistent with accretion and thus likely have a different origin to the bulk of the cluster population . the identification of additional globular clusters with peculiar chemical abundance patterns ( e.g. , star - to - star variations in metallicity ) would advance our understanding of the range and relative frequency of the abundance spread phenomenon in the galactic globular cluster system . additionally , quantifying the number of accreted systems has important consequences for understanding the formation and evolution of our galaxy @xcite . to this end , the most obvious objects to study are the most massive globular clusters with extended horizontal branches . m62 ( ngc 6266 ) is the ninth most luminous cluster @xcite and has an extended blue horizontal branch . in the f439w @xmath2 f555w versus f555w colour magnitude diagram presented by @xcite , the horizontal branch extends down in luminosity to the main sequence turn - off . the extended horizontal branch is also readily identified in dereddened @xmath7 versus @xmath8 and @xmath7 versus @xmath9 diagrams @xcite . m62 ranks fifth in the number of millisecond pulsars @xcite , and there may be a connection between multiple stellar populations and the numbers of millisecond pulsars @xcite . @xcite find that m62 could contain the most rr - lyrae of any galactic globular cluster and is a typical oosterhoff type i system . this cluster lies in the vicinity of the bulge , although proper - motion measurements indicate that it probably belongs to the thick disk @xcite . m62 is highly reddened , @xmath10 ) = 0.47 @xcite , and it is severely affected by differential reddening , @xmath11 @xmath12 0.25 @xcite . the goal of the present paper is to conduct a detailed chemical abundance analysis of m62 based on high - resolution , high signal - to - noise ratio spectra . to our knowledge this is the first such analysis of this cluster and this work therefore represents an essential step towards completing the census and characterisation of the galaxy s most massive globular clusters . six targets were selected from @xcite ( see table [ tab : param ] ) . all were high probability members based on the published radial velocities and were observed with the high dispersion spectrograph ( hds , @xcite ) on the subaru telescope on 2013 july 17 . the exposure times ranged from 16 to 40 minutes per program star . we used the stdyb setting and the 08 slit which resulted in a wavelength coverage from @xmath124100  to @xmath126800at a spectral resolution of @xmath13 . there were approximately four pixels per resolution element . spectra of a telluric standard ( hd 163955 ) and a radial velocity standard ( hd 182572 ) were also taken during this observing run . two additional targets were selected from strmgren photometry obtained by j.a - g and observed using the mike spectrograph @xcite at the magellan - ii telescope on 2012 june 26 . the exposure times were 1 hour for each star . the 07 slit was employed providing a spectral resolution of @xmath14 = 35,000 ( blue ccd ) and @xmath14 = 27,000 ( red ccd ) with a wavelength coverage from @xmath123800  to @xmath129000 . there were approximately four pixels per resolution element . a telluric standard ( hd 170642 ) was also observed .    in figure [ fig : cmd ] , we show the locations of our targets in @xmath15 colour - magnitude diagrams ( cmd ) . the photometry is from @xcite and 2mass @xcite . colour - magnitude diagrams for m62 from @xcite ( left panels ) and 2mass @xcite ( right panels ; taking only objects within a radius of 3.5 and `` aaa '' photometric quality flags ) . the aqua star represents the radial velocity non - member , star a195 , and the red circle represents star a124 , the possible non - member based on chemical abundances . all other program stars are shown as grey circles . in the left panels , the solid line represents the mean rgb ridge line from @xcite . ] @lccrrrrcccccc@ name & ra 2000 & dec . 2000 & @xmath16 & @xmath17 & @xmath18 & rv & @xmath19rv & @xmath20   & @xmath21  & @xmath22  & [ m / h ] & [ fe / h ] + & & & & & & ( km s@xmath23 ) & ( km s@xmath23 ) & ( k ) & ( cm s@xmath24 ) & ( km s@xmath23 ) & dex & dex + ( 1 ) & ( 2 ) & ( 3 ) & ( 4 ) & ( 5 ) & ( 6 ) & ( 7 ) & ( 8) & ( 9 ) & ( 10 ) & ( 11 ) & ( 12 ) & ( 13 ) +   + a5 & 17 01 16.21 & @xmath230 03 31.81 & 9.782 & 8.847 & 8.583 & @xmath275.0 & 0.2 & 3950 & 0.50 & 1.79 & @xmath21.10 & @xmath21.12 + a7 & 17 01 17.50 & @xmath230 03 20.60 & 9.602 & 8.608 & 8.389 & @xmath289.3 & 0.5 & 3925 & 0.20 & 1.89 & @xmath21.10 & @xmath21.15 + a14 & 17 01 17.29 & @xmath230 03 58.69 & 11.476 & 10.710 & 10.529 & @xmath254.2 & 0.2 & 4400 & 1.40 & 1.53 & @xmath21.10 & @xmath21.10 + a27 & 17 01 25.19 & @xmath230 04 09.85 & 11.779 & 11.124 & 10.989 & @xmath269.9 & 0.4 & 4625 & 1.50 & 1.76 & @xmath21.20 & @xmath21.24 + a124 & 17 01 00.28 & @xmath230 07 38.28 & 11.449 & 10.756 & 10.536 & @xmath268.2 & 0.3 & 4450 & 1.00 & 1.64 & @xmath21.20 & @xmath21.19 + a195 & 17 01 12.63 & @xmath230 03 40.78 & 11.988 & 11.318 & 11.157 & @xmath20.1 & 0.4 &  &  &  &  &  +   + c53 & 17 01 15.20 & @xmath230 08 36.50 & 10.101 & 9.246 &  & @xmath273.6 & 0.2 & 4450 & 1.40 & 1.78 & @xmath21.10 & @xmath21.11 + d10 & 17 01 16.80 & @xmath230 08 18.00 & 10.125 & 9.145 &  & @xmath259.0 & 0.2 & 4175 & 0.90 & 1.90 & @xmath21.10 & @xmath21.15 +      the subaru spectra were reduced using iraf . the magellan spectra were reduced using a combination of iraf and the mtools package . in both cases , the approach was similar to that described in @xcite . in figure [ fig : spec ] , we plot a region of the spectra for the program stars . the telluric standards were used to correct regions affected by telluric absorption . star a195 had a signal - to - noise ratio s / n = 40 per pixel near 6000 . excluding this star , the s / n ranged from s / n = 65 per pixel ( stars a14 and a27 ) to s / n = 110 per pixel ( star d10 ) .    /@xmath21/[fe / h ] ) are included . the red spectrum is star a124 , a possible non - member based on the chemical abundances . ]    for the program stars observed with subaru , heliocentric radial velocities were measured by cross - correlating each star against the radial velocity standard , hd 182572 , for which we adopted a valueudry / std / stdnew.dat ] of @xmath2100.35 km s@xmath23 . for the program stars observed with magellan , the radial velocities were determined by measuring the positions of a large number ( several hundred ) of atomic absorption features . the radial velocities are presented in table [ tab : param ] and we note that star a195 is not a radial velocity member . equivalent widths ( ew ) were measured using routines in iraf and daospec @xcite . we note that every line measured using daospec was also measured , and visually inspected , using iraf . for all stars , there was good agreement between the two sets of measurements ; for a given star , the average difference in ews between iraf and daospec was 0.1 m  with a dispersion of 3 m . the line list and ew measurements ( average of iraf and daospec ) are presented in table [ tab : ew ] . [ cols="^,^,^,>,>,>,>,>,>,>,>,^ " , ]      it is now well established that every globular cluster exhibits star - to - star abundance variations for c , n , o , f , na , mg and al ( e.g. , see reviews by @xcite ) . these abundance variations are believed to have been produced via hydrogen - burning at high temperature in asymptotic giant branch ( agb ) stars , fast - rotating massive stars and/or massive binaries ( e.g. , @xcite ) . @xcite and @xcite found that the abundance dispersions for the light elements correlate with various physical parameters . in particular , they noted that the interquartile range ( iqr ) for [ o / fe ] , [ na / fe ] , [ o / na ] and [ mg / al ] exhibits a correlation with the absolute luminosity , i.e. , total mass . within our modest sample , assuming for the purposes of this exercise that the [ o / fe ] limits are detections , we find iqr[o / na ] = 1.11 and iqr[mg / al ] = 0.89 . with @xmath1 = @xmath29.18 @xcite , the iqr values for m62 are consistent with those of other luminous clusters .      in figure [ fig : m62m4m5 ] we plot [ x / fe ] versus atomic number for m62 , m4 and m5 . regarding the @xmath5-process elements , zr , ba and la have ratios of [ x / fe ] @xmath3 + 0.4 . such values differ from the majority of field halo stars of similar metallicity and from the comparable metallicity globular cluster m5 . on the other hand , these abundance ratios in m62 are comparable ( but not identical ) to m4 , a cluster believed to have formed from gas enriched in @xmath5-process material . it is intriguing that both m4 and m62 are inner disk globular clusters of similar metallicity . enhancements in the @xmath5-process elements are also seen in the globular clusters @xmath0 cen and m22 ( e.g. , * ? ? ? * and references therein ) . for elements other than zr , ba and la , the abundance pattern in m62 more closely resembles that of m5 rather than m4 .        at the metallicity of these clusters , published neutron - capture element abundances in inner disk and bulge stars are limited . the @xcite comparison field stars in figure [ fig : field ] are solar neighbourhood objects . since the pioneering work by @xcite on chemical abundances in the bulge , the handful of papers presenting neutron - capture element abundances at or below [ fe / h ] = @xmath21.0 in the inner disk or bulge include @xcite and @xcite . although their sample sizes are modest , some stars are enriched with material produced by @xmath5-process nucleosynthesis . among the bulge and inner disk globular clusters with [ fe / h ] @xmath25 @xmath21.0 , ngc 6522 exhibits enhancements in the @xmath5-process elements @xcite while hp-1 @xcite and ngc 6558 @xcite do not . the abundances of rb and pb offer important diagnostics regarding the nature of the @xmath5-process . due to a branching point at @xmath26kr along the @xmath5-process path , the rb / zr ratio is sensitive to the neutron density at the site of the @xmath5-process . at high neutron density , the [ rb / zr ] ratio is expected to be a factor of @xmath1210 larger than at low neutron density @xcite , although the yields depend on details in the models and nuclear reaction rates @xcite . indeed , large rb abundances have been observed in massive agb stars @xcite . pb and bi are the last stable nuclei along the @xmath5-process path . if the total neutron exposure , or neutron supply per seed nuclei , is sufficiently high , large overabundances of these elements are predicted ( e.g. , * ? ? ? * ; * ? ? ? * ) , and have been observed ( e.g. , * ? ? ? * ; * ? ? ? as already noted , measurements of rb and pb were only possible for the two program stars observed at the magellan telescope . in figure [ fig : rb ] we show observed and synthetic spectra near the 7800  rbi  feature . we measure values of [ rb / fe ] = + 0.09 and + 0.13 for stars c53 and d10 , respectively . as can be seen in figure [ fig : m62m4m5 ] , those values fall closer to m5 ( [ rb / fe ] = 0.00 ) than to m4 ( [ rb / fe ] = + 0.39 ; @xcite ) . @xcite measured [ rb / fe ] in three globular clusters ( ngc 6752 , ngc 1904 and 47 tuc ) and found constant values in each cluster at the [ rb / fe ] @xmath3 0.0 level . the [ rb / zr ] ratios are @xmath20.04 and @xmath20.05 for stars c53 and d10 , respectively , when the zr abundances are shifted on the @xcite scale as described in @xcite . the [ rb / zr ] ratios in m62 lie below those of m4 and m5 , [ rb / zr ] = + 0.17 and + 0.08 , respectively , but above the @xmath0 cen values @xcite . in summary , the low [ rb / fe ] and [ rb / zr ] ratios in m62 offer no support for a weak @xmath5-process contribution ( i.e. , the @xmath5-process in massive stars from the @xmath27ne(@xmath28,@xmath29)@xmath30 mg reaction ) from which the high neutron density would result in considerably higher [ rb / fe ] and [ rb / zr ] ratios than observed . we will revisit the [ rb / zr ] ratio in the context of fast - rotating massive stars later in this subsection .    the sr abundance in m62 , @xmath31[sr / fe]@xmath32 = @xmath20.39 , appears to be unusually low compared to the neighbouring elements , @xmath31[rb / fe]@xmath32 = + 0.11 and @xmath31[y / fe]@xmath32 = + 0.16 . since our analysis only considered one line , sri  4607.33 , we regard the low sr abundance with some caution . indeed , other studies that consider the 4607.33  sri  line in globular cluster giants find [ sr / fe ] ratios that are lower than for the neighbouring elements [ rb / fe ] , [ y / fe ] and [ zr / fe ] ( e.g. , * ? ? ? * yong et al . 2014 , in preparation ) . @xcite investigated non - lte corrections for the 4607.33  sr line , and for @xmath20/@xmath21/[fe / h ] = 4400/2.2/@xmath21.2 , the correction is 0.29 dex . the magnitude and sign of this correction would help to reconcile the sr abundances with those of rb and y. in figure [ fig : m62m4m5 ] we adjust the sr abundance accordingly .    in figure [ fig : pb ] , we plot observed and synthetic spectra near the 4058  pbi  feature . we measure values of [ pb / fe ] @xmath330.09 and [ pb / fe ] = @xmath20.20 for stars c53 and d10 , respectively . for comparison , the average values in m4 and m5 are [ pb / fe ] = + 0.30 and @xmath20.35 , respectively @xcite . thus , the m62 values for [ pb / fe ] lie closer to m5 than to m4 ( see figure [ fig : m62m4m5 ] ) . @xcite argue that the pb / eu ratio offers a good diagnostic of the presence of @xmath5-process enriched material . for m62 , the pb to eu ratios are at the same level as the ( more metal - poor ) `` @xmath4-process standard stars '' in @xcite .    from table [ tab : abun2 ] , all element ratios [ eu / x ] ( for x = la and heavier elements ) are consistent , within @xmath120.2 dex , with the scaled - solar @xmath4-process distribution @xcite , see figure [ fig : eux ] . ( note that while we refer to @xmath5-process and @xmath4-process elements according to their origin in solar system material , those definitions may be incorrect in m62 , e.g. , la and ce in this cluster are likely produced primarily through the @xmath4-process . ) regarding the lighter elements , the first to deviate from the @xmath4-process signature is ba : while the solar @xmath4-process value is [ eu / ba]@xmath34 @xmath12 0.9 dex , m62 exhibits a ratio of @xmath12 0.2 dex . in the same way , all elements lighter than ba depart from the solar system @xmath4-process signature .     for x = rb to pb . the dashed red line represents the scaled - solar @xmath4-process distribution @xcite . ( for sr , we apply a non - lte correction of 0.29 dex , see section 4.2 for details . ) ]    the neutron - capture element abundance ratios of the m62 stars are not consistent with @xmath5-process nucleosynthesis occurring in agb stars of low metallicity . low - mass agb stars of @xmath35 are the main site of the @xmath5-process in the galaxy and typically produce [ hs / ls ] refers to the heavy @xmath5-process elements ( ba , la , etc . ) and @xmath36 refers to the light @xmath5-process elements ( y , zr , etc . ) . ] @xmath37 , [ pb / hs ] @xmath38  dex and [ rb / zr ] @xmath39 at [ fe / h ] @xmath40 ( e.g. , @xcite ; fishlock et al . 2014 , in preparation ) . this is a direct consequence of the operation of the @xmath41c(@xmath28,@xmath29)@xmath42o reaction which is the dominant neutron source for @xmath35 ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? for intermediate - mass agb stars the @xmath27ne(@xmath28,@xmath29)@xmath30 mg reaction is the neutron source and operates during convective thermal pulses . the abundance pattern produced in those stars should be dominated by lighter @xmath5-process elements ( y , rb , sr , zr ) @xcite . at [ fe / h ] @xmath40 , typical abundances in stars @xmath43 are [ hs / ls ] @xmath44 , [ pb / hs ] @xmath45 , and [ rb / zr ] @xmath46 dex ( fishlock et al . 2014 , in preparation ) . fast - rotating massive stars ( which we hereafter refer to interchangeably as `` spin stars '' ) can produce a large amount of @xmath5-process products at low metallicity , where the dominant neutron source is @xmath27ne(@xmath28,@xmath29)@xmath30 mg in the convective he - burning core and in the subsequent convective c - burning shell @xcite . in these stars , @xmath27ne is primary , i.e. , it is not directly produced from the initial cno abundances as in non - rotating massive stars ( see for instance the weak @xmath5-process in massive stars at solar metallicity , e.g. , @xcite ) . the faster the star rotates , the more primary @xmath27ne can be made available in the he core . the most abundant elements from the @xmath5-process in spin stars are sr , y and zr while production for heavier elements up to ba strongly depends on the rotation speed and on nuclear uncertainties , e.g. , on the @xmath28-capture rates on @xmath27ne @xcite and on the @xmath28-capture rates on @xmath47o ( e.g. , @xcite ) . the @xmath5-process in massive stars can not produce elements beyond the ba neutron - magic peak ( n = 82 ) due to basic properties of @xmath27ne as a neutron source ( e.g. , @xcite ) . spin stars have been suggested as the source of the light element abundance variations in globular clusters @xcite . recall that in figure [ fig : ncap ] there was no significant correlation between the abundances of na and the neutron - capture elements . thus , there is no obvious connection between the star - to - star na abundance variation and the enhancement in y , zr and ba abundances in this cluster . @xcite explored the impact of changing the amount of primary @xmath27ne available to make neutrons , from 1 percent ( in mass fraction ) to 0.2 percent , for a 25 m@xmath48  model at [ fe / h ] = @xmath23 . the result of this change was an increase in the [ zr / ba ] ratio from @xmath20.18 to 0.67 . as expected , eu is not efficiently produced by the @xmath5-process regardless of the initial abundance of @xmath27ne . m62 stars exhibits an average [ eu / ba ] = + 0.2 , and this value lies between the @xmath5-process abundance signature of spin stars and the @xmath4-process . this intermediate value may be a consequence of the combination of the @xmath4-process ( which makes eu and some ba ) and the @xmath5-process in spin stars ( producing ba and only a small amount of eu ) . m62 exhibits [ rb / zr ] and [ rb / y ] ratios of @xmath490.4 and @xmath490.1 , respectively . in the models considered by @xcite , reducing the initial @xmath27ne abundance from 1 per cent ( in mass fraction ) to 0.2 percent increases the [ rb / zr ] ratio from @xmath20.86 to @xmath20.57 , and the [ rb / y ] ratio from @xmath20.86 to @xmath20.75 . the predicted [ rb / zr ] ratio is slightly lower than the observations . those predictions were based on a 25 m@xmath48  spin star model . it would be of great interest to explore a larger range of initial masses in order to quantify the final core - collapse supernova yields for the elements from rb to zr . on the other hand , it is difficult to reconcile the average [ rb / y ] observed in m62 with spin star nucleosynthesis . y is efficiently produced at high neutron densities from sr . the dispersion in the [ y / fe ] ratio is consistent with the measurement uncertainties , although there is a hint that the [ y / fe ] ratios cluster around two values , @xmath120.1 and @xmath120.4 . the abundance enhancement at y and zr is a key feature of the lighter element primary process ( lepp ) exhibited by some halo stars at lower metallicities , [ fe / h ] @xmath50 @xmath22 ( e.g. , @xcite ) . while the astrophysical site of the lepp is not clearly understood , a number of scenarios have been proposed , including explosive nucleosynthesis triggered by neutrino - winds in core - collapse supernovae ( e.g. , @xcite ) and the @xmath5-process in fast - rotating massive stars ( e.g. , @xcite ) . while the aforementioned lepp explosive scenarios can not efficiently contribute to elements up to the ba peak , the @xmath5-process in spin stars may potentially produce them .    to summarise , while the abundance ratios for the elements y , zr and ba may be consistent with the @xmath5-process in spin stars , the high [ rb / y ] ratio is difficult to explain . spin - star models at metallicities closer to that of m62 and for a larger range of initial masses would be needed to perform a consistent chemical evolution study , and test the spin stars scenario for this cluster .    in this context , it has been reported that ngc 6522 , a bulge globular cluster , has enhanced sr and y abundances consistent with spin star nucleosynthesis @xcite . in that study , the abundances were derived from the sri6503.99  and yii  6613.73  lines . as noted in their paper , the sriline is weak . we suspect that this yii  line is blended with the fei6613.82  line @xcite , and this fe line has a lower excitation potential and @xmath51 value of 1.011 ev and @xmath25.587 , respectively ( vienna atomic line database , @xcite ) . it would therefore be interesting to re - examine the sr and y abundances in ngc 6522 using additional lines to confirm the sr and y enhancements in that cluster . our analysis reveals no evidence for an intrinsic metallicity dispersion in m62 . as noted in the introduction , the globular clusters with metallicity dispersions are preferentially the more luminous objects and tend to have extended horizontal branches . some , and perhaps all , of these clusters may be the nuclei of accreted dwarf galaxies . based on our results , m62 is a massive globular cluster with an extended horizontal branch that does not harbour a metallicity dispersion . star a124 has lower ratios of the neutron - capture elements when compared to the other program stars . although a124 has stellar parameters and a radial velocity consistent with cluster membership , the besanon model @xcite predicts that some field contamination is likely , @xmath124% . the simplest explanation is that a124 is a field star . the o and na abundances for a124 lie at the lower end of the distribution defined by the cluster stars and are similar to field stars . proper - motion and/or parallax measurements will test this hypothesis . nevertheless , future studies may reveal additional stars in m62 with a range of neutron - capture element abundances . if m62 really hosts two populations of stars , of equal size , with distinct neutron - capture element abundances , then the probability of observing six out of seven program stars from a single population is 6% . in this paper we present a chemical abundance analysis of seven bright giants in m62 , a luminous globular cluster with an extended horizontal branch . we find no evidence for a metallicity dispersion , as seen in other luminous globular clusters with similar horizontal branch morphology . we find star - to - star abundance variations and correlations for o , na and al and the amplitudes of those variations are comparable to those found in the most massive globular clusters . the elements zr , ba and la exhibit enhancements , [ x / fe ] @xmath12 + 0.4 , compared to field stars at the same metallicity . the lack of a significant correlation between the abundances of na and the neutron - capture elements would suggest that the light element variations and enhancement in y , zr and ba are produced in different processes and/or sites .    for the elements heavier than la , the abundances are consistent with the scaled - solar @xmath4-process distribution . on the other hand , y , zr and ba are clearly enhanced when compared to the scaled - solar @xmath4-process distribution . the abundance pattern for these elements is incompatible with the s - process in agb stars or in non - rotating massive stars . on the other hand , while the abundance distribution for these elements could be produced by fast - rotating massive stars , the high [ rb / y ] ratios that we measure do not match existing frms model predictions . one star has neutron - capture element abundance ratios that are distinct from the remaining stars . while this is likely a field halo star , the identification of additional stars in the vicinity of m62 with similar abundance patterns would be of great interest . studies of other luminous globular clusters are necessary to complete the census and characterisation of the most luminous clusters in the milky way . we thank christian johnson for helpful discussions . d.y , a.a.b , g.d.c , a.i.k and j.e.n gratefully acknowledge support from the australian research council ( grants dp0984924 , fs110200016 , ft110100475 and dp120101237 ) . j.a .- g acknowledges support by the chilean ministry for the economy , development , and tourism s programa iniciativa cientfica milenio through grant p07 - 021-f , awarded to the milky way millennium nucleus ; by proyecto fondecyt postdoctoral 3130552 ; by proyecto fondecyt regular 1110326 ; and by proyecto basal pfb-06/2007 . m.p acknowledges support from the ambizione grant of the snsf ( switzerland ) and eurogenesis ( masche ) . funding for the stellar astrophysics centre is provided by the danish national research foundation . the research is supported by the asterisk project ( asteroseismic investigations with song and kepler ) funded by the european research council ( grant agreement no . : 267864 ) .                                    , t. , yee , j.  c. , feltzing , s. , johnson , j.  a. , gould , a. , cohen , j.  g. , asplund , m. , melndez , j. , lucatello , s. , han , c. , thompson , i. , gal - yam , a. , udalski , a. , bennett , d.  p. , bond , i.  a. , kohei , w. , sumi , t. , suzuki , d. , suzuki , k. , takino , s. , tristram , p. , yamai , n. , & yonehara , a. 2013 , , 549 , a147      , r. , shectman , s.  a. , gunnels , s.  m. , mochnacki , s. , & athey , a.  e. 2003 , in society of photo - optical instrumentation engineers ( spie ) conference series , vol . 4841 , society of photo - optical instrumentation engineers ( spie ) conference series , ed . m.  iye & a.  f.  m. moorwood , 16941704    , a. , beard , m. , grres , j. , couder , m. , deboer , r. , falahat , s. , gray , r.  t. , kontos , a. , kratz , k .- l . , leblanc , p.  j. , li , q. , obrien , s. , zkan , n. , pignatari , m. , sonnabend , k. , talwar , r. , tan , w. , uberseder , e. , & wiescher , m. 2013 , , 87 , 045805                                                                                                                                                                  , a. , aparicio , a. , piotto , g. , rosenberg , a. , chaboyer , b. , sarajedini , a. , siegel , m. , anderson , j. , bedin , l.  r. , dotter , a. , hempel , m. , king , i. , majewski , s. , milone , a.  p. , paust , n. , & reid , i.  n. 2009 , , 694 , 1498      , a.  f. , sneden , c. , kraft , r.  p. , wallerstein , g. , norris , j.  e. , da costa , g. , milone , a.  p. , ivans , i.  i. , gonzalez , g. , fulbright , j.  p. , hilker , m. , piotto , g. , zoccali , m. , & stetson , p.  b. 2011 , , 532 , a8                                                    , m.  f. , cutri , r.  m. , stiening , r. , weinberg , m.  d. , schneider , s. , carpenter , j.  m. , beichman , c. , capps , r. , chester , t. , elias , j. , huchra , j. , liebert , j. , lonsdale , c. , monet , d.  g. , price , s. , seitzer , p. , jarrett , t. , kirkpatrick , j.  d. , gizis , j.  e. , howard , e. , evans , t. , fowler , j. , fullmer , l. , hurt , r. , light , r. , kopan , e.  l. , marsh , k.  a. , mccallon , h.  l. , tam , r. , van dyk , s. , & wheelock , s. 2006 , , 131 , 1163
with the exception of terzan 5 , all the galactic globular clusters that possess significant metallicity spreads , such as @xmath0 cen and m22 , are preferentially the more luminous clusters with extended horizontal branches . here 
 we present radial velocities and chemical abundances for seven bright giants in the globular cluster m62 , a previously little - studied cluster . 
 with @xmath1 = @xmath29.18 , m62 is the ninth most luminous galactic globular cluster and has an extended horizontal branch . within our sample , 
 we find ( i ) no evidence for a dispersion in metallicity , [ fe / h ] , beyond the measurement uncertainties , ( ii ) star - to - star abundance variations for c , o , na and al with the usual correlations between these elements as seen in other globular clusters , and ( iii ) a global enrichment for the elements zr , ba and la at the level [ x / fe ] @xmath3 + 0.4 dex . for elements heavier than la , the abundance ratios are consistent with the scaled - solar @xmath4-process distribution . 
 below la , the abundances are anomalous when compared to the scaled - solar @xmath5-process or @xmath4-process distributions . for these elements , 
 the abundance signature in m62 is in agreement with predictions of the @xmath5-process from fast - rotating massive stars , although the high [ rb / y ] ratio we measure may be a challenge to this scenario . 
 [ firstpage ]    stars : abundances  galaxy : abundances  globular clusters : individual : ngc 6266