Discovery of s-process enhanced stars in the LAMOST survey

Abstract

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.

9 pages, 6 figures

References in corpus (10)

• The Gaia mission
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Evolution and nucleosynthesis of asymptotic giant branch stellar models of low metallicity
• Elemental abundances in the atmosphere of clump giants
• Barium & related stars and their white-dwarf companions I. Giant stars
• Heavy elements in Globular Clusters: the role of AGB stars
• ${}^{22}$Ne and ${}^{23}$Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for ${}^{22}$Ne(p,$\gamma$)${}^{23}$Na

Cited by in corpus (2)

• Chemically peculiar A and F stars with enhanced s-process and iron-peak elements: stellar radiative acceleration at work
• Sr and Ba abundance determinations: comparing machine-learning with star-by-star analyses -- High-resolution re-analysis of suspected LAMOST barium stars