Peeking beneath the precision floor – I. Metallicity spreads and multiple elemental dispersions in the globular clusters NGC 288 and NGC 362

The view of globular clusters (GCs) as simple systems continues to unravel, revealing complex objects hosting multiple chemical peculiarities. Using differential abundance analysis, we probe the chemistry Type I GC, NGC 288 and II 362 at 2\% level for first time. We measure 20 elements find measurement uncertainties on order 0.01-0.02 dex in both clusters. smallest are measured Fe clusters, with an average uncertainty $\sim$0.013 dex. Dispersion abundances Na, Al, Ti I, Ni, Y, Zr, Ba Nd recovered 288, none which can be explained by a spread He. This is time, our knowledge, statistically significant $s$-process potential metallicity has been detected 288. In 362, dispersion same addition Co, Cu, Zn, Sr, La, Ce, Eu. Two distinct groups separated 0.3 abundances. Given strong correlations between Al several elements, correlation Mg Si, propose that rich group younger. agrees asymptotic giant branch star (AGB) enrichment generations, if there overlap low- intermediate-mass AGBs. scenario, older population dominated $r$-process $\Delta^{\mathrm{La}}-\Delta^{\mathrm{Eu}}$ ratio $-0.16\pm0.06$. dominance found primordial.