  M15 is a globular cluster with a known spread in neutron-capture elements.
This paper presents abundances of neutron-capture elements for 62 stars in M15.
Spectra were obtained with the Michigan/Magellan Fiber System (M2FS)
spectrograph, covering a wavelength range from ~4430-4630 A. Spectral lines
from Fe I, Fe II, Sr I, Zr II, Ba II, La II, Ce II, Nd II, Sm II, Eu II, and Dy
II, were measured, enabling classifications and neutron-capture abundance
patterns for the stars. Of the 62 targets, 44 are found to be highly
Eu-enhanced r-II stars, another 17 are moderately Eu-enhanced r-I stars, and
one star is found to have an s-process signature. The neutron-capture patterns
indicate that the majority of the stars are consistent with enrichment by the
r-process. The 62 target stars are found to show significant star-to-star
spreads in Sr, Zr, Ba, La, Ce, Nd, Sm, Eu, and Dy, but no significant spread in
Fe. The neutron-capture abundances are further found to have slight
correlations with sodium abundances from the literature, unlike what has been
previously found; follow-up studies are needed to verify this result. The
findings in this paper suggest that the Eu-enhanced stars in M15 were enhanced
by the same process, that the nucleosynthetic source of this Eu pollution was
the r-process, and that the r-process source occurred as the first generation
of cluster stars was forming.
