243 articles – 3643 Notices  [english version]
 HAL : in2p3-00126673, version 1
 arXiv : astro-ph/0610756
 Astronomy and Astrophysics 469 (2007) 265-274
 Is $^6$Li in metal-poor halo stars produced in situ by solar-like flares ?
 (2007)
 The high 6-Li abundances recently measured in metal-poor halo stars are far above the value predicted by Big Bang nucleosynthesis. They cannot be explained by galactic cosmic-ray interactions in the interstellar medium either. Various pre-galactic sources of 6-Li have been proposed in the literature. We study the possibility that the observed 6-Li was produced by repeated solar-like flares on the main sequence of these low-metallicity stars. The time-dependent flaring activity of these objects is estimated from the observed evolution of rotation-induced activity in Pop I dwarf stars. As in solar flares, 6-Li could be mainly created in interactions of flare-accelerated 3-He with stellar atmospheric 4-He, via the reaction 4-He(3-He,p)6-Li. Stellar dilution and destruction of flare-produced 6-Li are evaluated from the evolutionary models of metal-poor stars developed by Richard and co-workers. Stellar depletion should be less important for 6-Li atoms synthesized in flares than for those of protostellar origin. Theoretical frequency distributions of 6-Li/7-Li ratios are calculated using a Monte-Carlo method and compared with the observations. Excellent agreement is found with the measured 6-Li/7-Li distribution, when taking into account the contribution of protostellar 6-Li originating from galactic cosmic-ray nucleosynthesis. We propose as an observational test of the model to seek for a positive correlation between 6-Li/7-Li and stellar rotation velocity. We also show that the amounts of 7-Li, Be and B produced in flares of metal-poor halo stars are negligible as compared with the measured abundances of these species. 6-Li in low-metallicity stars may be a unique evidence of the nuclear processes occuring in stellar flares.
 Thème(s) : Physique/Astrophysique/Cosmologie et astrophysique extra-galactiquePlanète et Univers/Astrophysique
 Lien vers le texte intégral : http://fr.arXiv.org/abs/astro-ph/0610756
 in2p3-00126673, version 1 http://hal.in2p3.fr/in2p3-00126673 oai:hal.in2p3.fr:in2p3-00126673 Contributeur : Dominique Girod <> Soumis le : Jeudi 25 Janvier 2007, 15:45:18 Dernière modification le : Lundi 13 Août 2007, 11:15:42