New estimates of the contribution of Wolf-Rayet stellar winds to the Galactic 26Al
ABSTRACT 12 pages, 8 figures.-- arXiv:0409580 astro-ph pre-print supplied.-- Final full-text version of the paper available at: http://dx.doi.org/10.1051/0004-6361:20041757. SIMBAD Objects associated to the paper available at: http://simbad.u-strasbg.fr/simbo.pl?bibcode=2005A%26A...429..613P. We present new yields of 26Al from Wolf-Rayet stellar winds based on rotating stellar models which account well for numerous observed properties of massive stars. We study the impacts on the yields of a change of initial mass, metallicity and initial rotation velocity. We also consider the effects of a change of mass loss rates during the Wolf-Rayet phase. We show that for surface rotation velocities during the core H-burning phase matching to the observed ones, the quantity of 26Al ejected by a star of a given initial mass and metallicity is roughly doubled when the effects of rotation are taken into account. The metallicity dependence of the yield is, on the other hand, very similar to that obtained from non-rotating models. We estimate that at least about 20% to 50% (e.g. ∼0.6-1.4 M_O) of the live 26Al detected in the Milky-Way originates from Wolf-Rayet stellar winds. We show the importance of a good knowledge of the present metallicity gradient and star formation rate in our galaxy for modeling both the variation of the 26Al surface density with the galactocentric distance and the global contribution of the Wolf-Rayet stellar winds to the present galactic mass of 26Al. A. Palacios acknowledges financial support from ESA PRODEX fellowship no 90069. Peer reviewed
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ABSTRACT: A comparative analysis of the various scenarios proposed to explain the 26Al content of the galaxy, as observed through its characterisitc γ-ray line at 1.8 MeV, is presented. We include some sug- gestions about how theoretical yields should be handled, accounting for the influence of the initial metallicity of the corresponding star, which depends not only on its mass but also on its location in the galaxy. A code of chemical evolution of the galaxy is used to derive the temporal evolution of metallicity along the galaxy, the necessary tool to deter mine the initial metallicity of any stellar source of 26Al. The contribution of each scenario (AGB stars, massive stars and classical novae) and its range of uncertainty are described.01/2006;
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ABSTRACT: This is a brief review of the progress made since the seminal contributions to the foundations of the theory of nucleosynthesis by M. Burbidge, G. Burbidge, Fowler and Hoyle, and by Cameron. The reviewed topics are (1) the nuclear physics input to the nucleosynthesis models (nuclear masses, fission, rates of β-decays, neutrino reactions, photoreactions, and nuclear charged particle-induced or neutron-induced reactions), (2) the nuclear physics and astrophysics aspects of the r-process, and (3) the same items for the p-process.EAS Publications Series 12/2007; 32:1 - 59.
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ABSTRACT: Context. Super AGB (SAGB) stars have initial masses ranging between ∼7–11 M and develop efficient hydrogen burning at the base of their convective envelope during their AGB evolution, leading to a substantial production of 26 Al g . Aims. We present the first discussion of the contribution of the SAGB stars to the galactic 26 Al g production, and we estimate the main uncertainties that affect the determination of the 26 Al g yields. Methods. The results of full stellar evolution computations are presented, with special emphasis on the 26 Al g yields from SAGB stars. We also use a postprocessing nucleosynthesis code to quantify the uncertainties associated with the nuclear reaction rates and with the treatment of convection that modifies the thermodynamical conditions at the base of the convective envelope. Results. Hot bottom burning leads to individual SAGB 26 Al g yields that are larger than those from intermediate mass stars, amounting to typical values as high as 5 × 10 −5 M . The overall SAGB contribution remains modest, however, not exceeding ∼0.3 M of the estimated galactic content of 2.8 M . On the other hand, the SAGB 26 Al/ 27 Al ratios always exceed 0.01, which is commensurable with the values measured in some SiC grains considered to originate in C-rich AGB stars. However, the isotopic composition of some other elements, particularly nitrogen, is clearly at variance with the observations. We find that the 26 Al g yields are not affected by the pollution induced by the third dredge-ups, but that they strongly depend on the evolution of the temperature at the base of the convective envelope, the determination of which remains highly dependent on the specific convection model used in the stellar computations. Modifications of T env by ±10% leads to variations in the 26 Al g yields by a factor of 0.2 to 6. In comparison, the nuclear reaction rate uncertainties have less of an impact, altering the yields by less than a factor of 2.Astronomy and Astrophysics 01/2008; 489:395-402. · 4.48 Impact Factor