We report for the first time on the chemical composition of the halo cluster NGC 5897 ( R _ { \odot } =12.5 kpc ) , based on chemical abundance ratios for 27 \alpha - , iron-peak , and neutron-capture elements in seven red giants .
From our high-resolution , high signal-to-noise spectra obtained with the Magellan/MIKE spectrograph , we find a mean iron abundance from the neutral species of [ Fe/H ] = -2.04 \pm 0.01 ( stat . ) \pm 0.15 ( sys .
) , which is more metal-poor than implied by previous photometric and low-resolution spectroscopic studies .
NGC 5897 is \alpha -enhanced ( to 0.34 \pm 0.01 dex ) and shows Fe-peak element ratios typical of other ( metal-poor ) halo globular clusters ( GCs ) with no overall , significant abundance spreads in iron nor in any other heavy element .
Like other GCs , NGC 5897 shows a clear Na-O anti-correlation , where we find a prominent primordial population of stars with enhanced O abundances and \sim Solar Na/Fe ratios , while two stars are Na-rich , providing chemical proof of the presence of multiple populations in this cluster .
Comparison of the heavy element abundances with the Solar-scaled values and the metal poor GC M15 from the literature confirms that NGC 5897 has experienced only little contribution from s -process nucleosynthesis .
One star of the first generation stands out in that it shows very low La and Eu abundances .
Overall , NGC 5897 is a well-behaved GC showing archetypical correlations and element-patterns , with little room for surprises in our data .
We suggest that its lower metallicity could explain the unusually long periods of RR Lyr that were found in NGC 5897 .