Ja. Brown et al., Elemental abundances in five stars in M54, a globular cluster associated with the Sagittarius galaxy, ASTRONOM J, 118(3), 1999, pp. 1245-1251
Chemical abundances in five stars in M54, a globular cluster associated wit
h the Sagittarius dwarf galaxy, have been determined using high-resolution
echelle spectra. We find the cluster to have [Fe/H] = -1.55 and possibly ha
lo-normal abundance patterns, although the [O/Fe] and [alpha/Fe] ratios lie
between solar and the normal halo values. One star shows the combination o
f low oxygen and enhanced Na and Al, symptomatic of deep mixing of ON-cycle
and other proton-capture products; a second star shows a lesser degree of
O depletion unaccompanied by Na and Al excesses. In the cluster Eu is also
enhanced, indicating that about 30% of the Ba in the cluster is due to the
r-process. In general, M54 is similar to globulars of comparable metallicit
y in the inner Galactic halo, despite its clear association with the Sagitt
arius dwarf spheroidal.