Discovery of s-process enhanced stars in the LAMOST survey
  Here we present the discovery of 895 s-process-rich candidates from 454,180
giant stars observed by the Large Sky Area Multi-Object Fibre Spectroscopic
Telescope (LAMOST) using a data-driven approach. This sample constitutes the
largest number of s-process enhanced stars ever discovered. Our sample includes
187 s-process-rich candidates that are enhanced in both barium and strontium,
49 stars with significant barium enhancement only and 659 stars that show only
a strontium enhancement. Most of the stars in our sample are in the range of
effective temperature and log g typical of red giant branch (RGB) populations,
which is consistent with our observational selection bias towards finding RGB
stars. We estimate that only a small fraction (0.5 per cent) of binary
configurations are favourable for s-process enriched stars. The majority of our
s-process-rich candidates (95 per cent) show strong carbon enhancements,
whereas only five candidates (less than 3 percent) show evidence of sodium
enhancement. Our kinematic analysis reveals that 97 percent of our sample are
disc stars, with the other 3 percent showing velocities consistent with the
Galactic halo. The scaleheight of the disc is estimated to be zh=0.634kpc,
comparable with values in the literature. A comparison with the yields from
asymptotic giant branch (AGB) models suggests that the main neutron source
responsible for the Ba and Sr enhancements is the 13C(alpha,n)16O reaction. We
conclude that the s-process-rich candidates may have received their
overabundances via mass transfer from a previous ABG companion with an initial
mass in the range 1-3Msun.
