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Contribution of Wolf-Rayet stars to the synthesis of 26Al I. The γ-ray connection

par Meynet, Georges ;Arnould, Marcel ;Paulus, Guy ;Prantzos, Nikos
Référence Astronomy & astrophysics, 320, 2, page (460-468)
Publication Publié, 1997-04

Article révisé par les pairs

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Résumé :

New 26Al yield predictions are derived from Wolf-Rayet (WR) model stars that are able to account better than previous ones for many important observed characteristics (like luminosities, surface chemical compositions, or number statistics) as a result of the adoption of new physical ingredients, and in particular of higher mass loss rates. The updated yields computed for WR stars with initial masses between 25 and 120 M⊙ and metallicities Z = 0.008, 0.020, and 0.040, turn out to be about twice larger than previously reported ones. These WR yields lead to a galactic steady state 26Al production rate of 0.9 ± 0.5 M⊙ My-1. The quoted error bar just takes into account the uncertainties in the IMF slope, the galactic metallicity gradient and the core collapse supernova rate. Thus, WR stars might account for 20 to 70% of the approximate 2 M⊙ of 26Al that are believed to be present in our Galaxy. An even larger 26Al contamination of the Galaxy by WR stars cannot be ruled out, as it appears from an analysis of the impact on the 26Al yields of other sources of uncertainty that affect individual model stars, like the mass loss rate, the mixing procedure, and some key nuclear reaction rates. Each effect considered separately may lead to an additional uncertainty in the WR yields that amounts to a factor of about 2 to 3.