Discovery of s-process enhanced stars in the LAMOST survey

Brodie Norfolk, Andrew Casey, Amanda Karakas, Matthew T. Miles, Alex Kemp, Kevin C Schlaufman, Melissa K. Ness, Anna Ho, John Lattanzio, Alexander P. Ji

Research output: Contribution to journalArticleResearchpeer-review

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 (<3  per cent) show evidence of sodium enhancement. Our kinematic analysis reveals that 97 per cent of our sample are disc stars, with the other 3 per cent showing velocities consistent with the Galactic halo. The scale height of the disc is estimated to be zh=0.634±0.063kpc⁠, comparable with values in the literature. A comparison with yields from asymptotic giant branch (AGB) models suggests that the main neutron source responsible for the Ba and Sr enhancements is the 13C(α,n)16O reaction. We conclude that s-process-rich candidates may have received their overabundances via mass transfer from a previous AGB companion with an initial mass in the range 1−3M⊙⁠.
Original languageEnglish
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume490
Issue number2
DOIs
Publication statusPublished - 22 Oct 2019

Cite this

Norfolk, Brodie ; Casey, Andrew ; Karakas, Amanda ; Miles, Matthew T. ; Kemp, Alex ; Schlaufman, Kevin C ; Ness, Melissa K. ; Ho, Anna ; Lattanzio, John ; Ji, Alexander P. / Discovery of s-process enhanced stars in the LAMOST survey. In: Monthly Notices of the Royal Astronomical Society. 2019 ; Vol. 490, No. 2.
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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 (<3  per cent) show evidence of sodium enhancement. Our kinematic analysis reveals that 97 per cent of our sample are disc stars, with the other 3 per cent showing velocities consistent with the Galactic halo. The scale height of the disc is estimated to be zh=0.634±0.063kpc⁠, comparable with values in the literature. A comparison with yields from asymptotic giant branch (AGB) models suggests that the main neutron source responsible for the Ba and Sr enhancements is the 13C(α,n)16O reaction. We conclude that s-process-rich candidates may have received their overabundances via mass transfer from a previous AGB companion with an initial mass in the range 1−3M⊙⁠.",
author = "Brodie Norfolk and Andrew Casey and Amanda Karakas and Miles, {Matthew T.} and Alex Kemp and Schlaufman, {Kevin C} and Ness, {Melissa K.} and Anna Ho and John Lattanzio and Ji, {Alexander P.}",
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Discovery of s-process enhanced stars in the LAMOST survey. / Norfolk, Brodie; Casey, Andrew; Karakas, Amanda; Miles, Matthew T.; Kemp, Alex; Schlaufman, Kevin C; Ness, Melissa K.; Ho, Anna; Lattanzio, John; Ji, Alexander P.

In: Monthly Notices of the Royal Astronomical Society, Vol. 490, No. 2, 22.10.2019.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Discovery of s-process enhanced stars in the LAMOST survey

AU - Norfolk, Brodie

AU - Casey, Andrew

AU - Karakas, Amanda

AU - Miles, Matthew T.

AU - Kemp, Alex

AU - Schlaufman, Kevin C

AU - Ness, Melissa K.

AU - Ho, Anna

AU - Lattanzio, John

AU - Ji, Alexander P.

PY - 2019/10/22

Y1 - 2019/10/22

N2 - 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 (<3  per cent) show evidence of sodium enhancement. Our kinematic analysis reveals that 97 per cent of our sample are disc stars, with the other 3 per cent showing velocities consistent with the Galactic halo. The scale height of the disc is estimated to be zh=0.634±0.063kpc⁠, comparable with values in the literature. A comparison with yields from asymptotic giant branch (AGB) models suggests that the main neutron source responsible for the Ba and Sr enhancements is the 13C(α,n)16O reaction. We conclude that s-process-rich candidates may have received their overabundances via mass transfer from a previous AGB companion with an initial mass in the range 1−3M⊙⁠.

AB - 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 (<3  per cent) show evidence of sodium enhancement. Our kinematic analysis reveals that 97 per cent of our sample are disc stars, with the other 3 per cent showing velocities consistent with the Galactic halo. The scale height of the disc is estimated to be zh=0.634±0.063kpc⁠, comparable with values in the literature. A comparison with yields from asymptotic giant branch (AGB) models suggests that the main neutron source responsible for the Ba and Sr enhancements is the 13C(α,n)16O reaction. We conclude that s-process-rich candidates may have received their overabundances via mass transfer from a previous AGB companion with an initial mass in the range 1−3M⊙⁠.

U2 - 10.1093/mnras/stz2630

DO - 10.1093/mnras/stz2630

M3 - Article

VL - 490

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

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ER -