We present radial velocities , stellar parameters , and detailed abundances of 39 elements derived from high-resolution spectroscopic observations of red giant stars in the luminous , metal-poor globular cluster NGC 5824 .
We observe 26 stars in NGC 5824 using the Michigan/Magellan Fiber System ( M2FS ) and two stars using the Magellan Inamori Kyocera Echelle ( MIKE ) spectrograph .
We derive a mean metallicity of [ Fe/H ] = - 1.94 \pm 0.02 ( statistical ) \pm 0.10 ( systematic ) .
The metallicity dispersion of this sample of stars , 0.08 dex , is in agreement with previous work and does not exceed the expected observational errors .
Previous work suggested an internal metallicity spread only when fainter samples of stars were considered , so we can not exclude the possibility of an intrinsic metallicity dispersion in NGC 5824 .
The M2FS spectra reveal a large internal dispersion in [ Mg/Fe ] , 0.28 dex , which is found in a few other luminous , metal-poor clusters .
[ Mg/Fe ] is correlated with [ O/Fe ] and anti-correlated with [ Na/Fe ] and [ Al/Fe ] .
There is no evidence for internal dispersion among the other \alpha - or Fe-group abundance ratios .
Twenty-five of the 26 stars exhibit a n -capture enrichment pattern dominated by r -process nucleosynthesis ( \langle [ Eu/Fe ] \rangle = + 0.11 \pm 0.12 ; \langle [ Ba/Eu ] \rangle = - 0.66 \pm 0.05 ) .
Only one star shows evidence of substantial s -process enhancement ( [ Ba/Fe ] = + 0.56 \pm 0.12 ; [ Ba/Eu ] = + 0.38 \pm 0.14 ) , but this star does not exhibit other characteristics associated with s -process enhancement via mass-transfer from a binary companion .
The Pb and other heavy elements produced by the s -process suggest a timescale of no more than a few hundred Myr for star formation and chemical enrichment , like the complex globular clusters M2 , M22 , and NGC 5286 .