Oxide grains, enclosed in meteorites, give us very precise information about the stars in which they formed. Grains belonging to group 1 and 2 are characterized by values of 17O/ 16O and 18O/ 16O inconsistent with explosive nucleosynthesis scenarios, and are then believed to form in low mass stars. Nowadays, models of non convective mixing coupled with nuclear burning succeed in reproducing the oxygen isotopic mix found in these ancient solids thanks to the more accurate nuclear physics inputs employed in calculations. However, a large part of oxide grains shows values of the 26Al/ 27Al isotopic ratio too high to be accounted for by the mixing models mentioned above. Recently, [1] demonstrated that the stellar magnetic field might promote the transport of material across the stellar radiative layers. We apply this magnetic mixing model to a 1.2M⊙ AGB star of solar metallicity. It turns out that the oxygen and aluminum isotopic ratios shown by group 1 and 2 grains are perfectly reproduced.
Stellar MHD and Nuclear Physics Coupled Together Solve the Puzzle of Oxide Grain Composition
PALMERINI, SARA;TRIPPELLA, OSCAR;BUSSO, Maurizio Maria;PETRELLI, MAURIZIO;ZUCCHINI, AZZURRA
2017
Abstract
Oxide grains, enclosed in meteorites, give us very precise information about the stars in which they formed. Grains belonging to group 1 and 2 are characterized by values of 17O/ 16O and 18O/ 16O inconsistent with explosive nucleosynthesis scenarios, and are then believed to form in low mass stars. Nowadays, models of non convective mixing coupled with nuclear burning succeed in reproducing the oxygen isotopic mix found in these ancient solids thanks to the more accurate nuclear physics inputs employed in calculations. However, a large part of oxide grains shows values of the 26Al/ 27Al isotopic ratio too high to be accounted for by the mixing models mentioned above. Recently, [1] demonstrated that the stellar magnetic field might promote the transport of material across the stellar radiative layers. We apply this magnetic mixing model to a 1.2M⊙ AGB star of solar metallicity. It turns out that the oxygen and aluminum isotopic ratios shown by group 1 and 2 grains are perfectly reproduced.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
