TY - JOUR

T1 - Rubidium in Barium stars

AU - Roriz, M. P.

AU - Lugaro, M.

AU - Pereira, C. B.

AU - Drake, N. A.

AU - Junqueira, S.

AU - Sneden, C.

N1 - Publisher Copyright: © 2021 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/3/1

Y1 - 2021/3/1

N2 - Barium (Ba) stars are chemically peculiar stars that display in their atmospheres signatures of the slow neutron-capture (s-process) mechanism that operates within asymptotic giant branch (AGB) stars, an important contributor to the cosmic abundance. The observed chemical peculiarity in these objects is not due to self-enrichment, but to mass transfer between the components of a binary system. The atmospheres of Ba stars are therefore excellent astrophysical laboratories, providing strong constraints for the nucleosynthesis of the s-process in AGB stars. In particular, rubidium (Rb) is a key element for the s-process diagnostic because it is sensitive to the neutron density and hence its abundance points to the main neutron source of the s-process in AGB stars. We present Rb abundances for a large sample of 180 Ba stars from high-resolution spectra (R = 48 000), and we compare the observed [Rb/Zr] ratios with theoretical predictions from s-process models in AGB stars. The target Ba stars in this study display [Rb/Zr] < 0, showing that Rb was not efficiently produced by the activation of the branching points at 85Kr and 86Rb. Model predictions from the Monash and FRUITY datasets of low-mass (≤4 MO) AGB stars are able to cover the Rb abundances observed in the program Ba stars. These observations indicate that the 13C(α,n)16O reaction is the main neutron source of the s-process in the low-mass AGB companions of the observed Ba stars. We have not found in the present study candidate companions for former IR/OH massive AGB stars.

AB - Barium (Ba) stars are chemically peculiar stars that display in their atmospheres signatures of the slow neutron-capture (s-process) mechanism that operates within asymptotic giant branch (AGB) stars, an important contributor to the cosmic abundance. The observed chemical peculiarity in these objects is not due to self-enrichment, but to mass transfer between the components of a binary system. The atmospheres of Ba stars are therefore excellent astrophysical laboratories, providing strong constraints for the nucleosynthesis of the s-process in AGB stars. In particular, rubidium (Rb) is a key element for the s-process diagnostic because it is sensitive to the neutron density and hence its abundance points to the main neutron source of the s-process in AGB stars. We present Rb abundances for a large sample of 180 Ba stars from high-resolution spectra (R = 48 000), and we compare the observed [Rb/Zr] ratios with theoretical predictions from s-process models in AGB stars. The target Ba stars in this study display [Rb/Zr] < 0, showing that Rb was not efficiently produced by the activation of the branching points at 85Kr and 86Rb. Model predictions from the Monash and FRUITY datasets of low-mass (≤4 MO) AGB stars are able to cover the Rb abundances observed in the program Ba stars. These observations indicate that the 13C(α,n)16O reaction is the main neutron source of the s-process in the low-mass AGB companions of the observed Ba stars. We have not found in the present study candidate companions for former IR/OH massive AGB stars.

KW - nuclear reactions, nucleosynthesis, abundances

KW - stars: abundances

KW - stars: chemically peculiar

KW - RED GIANTS

KW - ASYMPTOTIC GIANT BRANCH

KW - HEAVY-ELEMENT ABUNDANCES

KW - BINARY NATURE

KW - NEUTRON-CAPTURE

KW - STELLAR YIELDS

KW - CHEMICAL-COMPOSITION

KW - METAL-POOR

KW - NUCLEOSYNTHESIS

KW - OPEN CLUSTERS

UR - http://www.scopus.com/inward/record.url?scp=85100723904&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/2b0df40d-f69f-3095-9505-4b7477a04447/

U2 - 10.1093/mnras/staa3888

DO - 10.1093/mnras/staa3888

M3 - Article

AN - SCOPUS:85100723904

VL - 501

SP - 5834

EP - 5844

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -