s-process production in rotating massive stars at solar and low metallicities

Frischknecht, Urs and Hirschi, Raphael and Pignatari, Marco and Maeder, André and Meynet, George and Chiappini, Cristina and Thielemann, Friedrich-Karl and Rauscher, Thomas and Georgy, Cyril and Ekström, Sylvia. (2016) s-process production in rotating massive stars at solar and low metallicities. Monthly Notices of the Royal Astronomical Society, 456 (2). pp. 1803-1825.

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Official URL: http://edoc.unibas.ch/53874/

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Rotation was shown to have a strong impact on the structure and light element nucleosynthesis in massive stars. In particular, models including rotation can reproduce the primary nitrogen observed in halo extremely metal poor (EMP) stars. Additional exploratory models showed that rotation may enhance s-process production at low metallicity. Here we present a large grid of massive star models including rotation and a full s-process network to study the impact of rotation on the weak s-process. We explore the possibility of producing significant amounts of elements beyond the strontium peak, which is where the weak s-process usually stops. We used the Geneva stellar evolution code coupled to an enlarged reaction network with 737 nuclear species up to bismuth to calculate 15-40 M ⊙ models at four metallicities (Z = 0.014, 10 -3 , 10 -5 and 10 -7 ) from the main sequence up to the end of oxygen burning. We confirm that rotation-induced mixing between the convective H-shell and He-core enables an important production of primary 14 N and 22 Ne and s-process at low metallicity. At low metallicity, even though the production is still limited by the initial number of iron seeds, rotation enhances the s-process production, even for isotopes heavier than strontium, by increasing the neutron-to-seed ratio. The increase in this ratio is a direct consequence of the primary production of 22 Ne. Despite nuclear uncertainties affecting the s-process production and stellar uncertainties affecting the rotation-induced mixing, our results show a robust production of s-process at low metallicity when rotation is taken into account. Considering models with a distribution of initial rotation rates enables us to reproduce the observed large range of the [Sr/Ba] ratios in (carbon-enhanced and normal) EMP stars.
Faculties and Departments:05 Faculty of Science > Departement Physik > Former Organization Units Physics > Theoretische Physik Astrophysik (Thielemann)
UniBasel Contributors:Thielemann, Friedrich-Karl and Rauscher, Thomas
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Oxford University Press
Note:Publication type according to Uni Basel Research Database: Journal article -- The final publication is available at Oxford University Press, see DOI link.
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Last Modified:20 Feb 2017 10:41
Deposited On:20 Feb 2017 10:40

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