Using the NIRSPEC spectrograph at Keck II , we have obtained infrared echelle spectra covering the 1.5 - 1.8 ~ { } \mu m range for giant stars in the massive bulge globular clusters NGCÂ 6440 and NGCÂ 6441 .
We report the first high dispersion abundance for NGCÂ 6440 , [ Fe/H ] = -0.56 \pm 0.02 and we find [ Fe/H ] = -0.50 \pm 0.02 for the blue HB cluster NGCÂ 6441 .
We measure an average \alpha -enhancement of \approx + 0.3 Â dex in both clusters , consistent with previous measurements of other metal rich bulge clusters , and favoring the scenario of a rapid bulge formation and chemical enrichment .
We also measure very low ^ { 12 } C / ^ { 13 } C isotopic ratios ( \approx 5 \pm 1 ) , suggesting that extra-mixing mechanisms are at work during evolution along the Red Giant Branch also in the high metallicity regime .
We also measure Al abundances , finding average [ Al / Fe ] = 0.45 \pm 0.02 and [ Al / Fe ] = 0.52 \pm 0.02 in NGCÂ 6440 and NGCÂ 6441 , respectively , and some Mg-Al anti-correlation in NGCÂ 6441 .
We also measure radial velocities v _ { r } =–76 \pm 3 km/s and v _ { r } =+14 \pm 3 km/s and velocity dispersions \sigma =9 \pm 2 km/s and \sigma =10 \pm 2 km/s , in NGCÂ 6440 and NGCÂ 6441 , respectively .