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ABSTRACT Strong metallicity-dependent winds dominate the evolution of core He-burning, classical Wolf–Rayet (cWR) stars, which eject both H and He-fusion products such as $$^{14}$$N, $$^{12}$$C, $$^{16}$$O, $$^{19}$$F, $$^{22}$$Ne, and $$^{23}$$Na during their evolution. The chemical enrichment from cWRs can be significant. cWR stars are also key sources for neutron production relevant for the weak s-process. We calculate stellar models of cWRs at solar metallicity for a range of initial Helium star masses (12–50 $$\rm M_{\odot }$$), adopting recent hydrodynamical wind rates. Stellar wind yields are provided for the entire post-main sequence evolution until core O-exhaustion. While literature has previously considered cWRs as a viable source of the radioisotope $$^{26}$$Al, we confirm that negligible $$^{26}$$Al is ejected by cWRs since it has decayed to $$^{26}$$Mg or proton-captured to $$^{27}$$Al. However, in Paper I, we showed that very massive stars eject substantial quantities of $$^{26}$$Al, among other elements including N, Ne, and Na, already from the zero-age-main-sequence. Here, we examine the production of $$^{19}$$F and find that even with lower mass-loss rates than previous studies, our cWR models still eject substantial amounts of $$^{19}$$F. We provide central neutron densities (N$$_{n}$$) of a 30 $$\rm M_{\odot }$$ cWR compared with a 32 $$\rm M_{\odot }$$ post-VMS WR and confirm that during core He-burning, cWRs produce a significant number of neutrons for the weak s-process via the $$^{22}$$Ne($$\alpha$$,n)$$^{25}$$Mg reaction. Finally, we compare our cWR models with observed [Ne/He], [C/He], and [O/He] ratios of Galactic WC and WO stars.
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Stellar wind yields of very massive stars
Abstract The most massive stars provide an essential source of recycled material for young clusters and galaxies. While very massive stars (VMS, M>100 $$\rm {\rm M}_{\odot }$$) are relatively rare compared to O stars, they lose disproportionately large amounts of mass already from the onset of core H-burning. VMS have optically thick winds with elevated mass-loss rates in comparison to optically thin standard O-star winds. We compute wind yields and ejected masses on the main sequence, and we compare enhanced mass-loss rates to standard ones. We calculate solar metallicity wind yields from MESA stellar evolution models in the range 50 – 500 $$\rm {\rm M}_{\odot }$$, including a large nuclear network of 92 isotopes, investigating not only the CNO-cycle, but also the Ne-Na and Mg-Al cycles. VMS with enhanced winds eject 5-10 times more H-processed elements (N, Ne, Na, Al) on the main sequence in comparison to standard winds, with possible consequences for observed anti-correlations, such as C-N and Na-O, in globular clusters. We find that for VMS 95% of the total wind yields is produced on the main sequence, while only ∼ 5% is supplied by the post-main sequence. This implies that VMS with enhanced winds are the primary source of 26Al, contrasting previous works where classical Wolf-Rayet winds had been suggested to be responsible for Galactic 26Al enrichment. Finally, 200 $$\rm {\rm M}_{\odot }$$ stars eject 100 times more of each heavy element in their winds than 50 $$\rm {\rm M}_{\odot }$$ stars, and even when weighted by an IMF their wind contribution is still an order of magnitude higher than that of 50 $$\rm {\rm M}_{\odot }$$ stars.
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- Award ID(s):
- 1927130
- PAR ID:
- 10464304
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- ISSN:
- 0035-8711
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/mnras/stad2537
