The s process in rotating low-mass AGB stars. Nucleosynthesis calculations in models matching asteroseismic constraints

den Hartogh, Jacqueline and Hirschi, R. and Lugaro, Maria and Doherty, Carolyn and Battino, U. and Pignatari, Marco (2019) The s process in rotating low-mass AGB stars. Nucleosynthesis calculations in models matching asteroseismic constraints. ASTRONOMY & ASTROPHYSICS, 629. ISSN 0004-6361

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Abstract

Aims: We investigate the s-process during the AGB phase of stellar models whose cores are enforced to rotate at rates consisten with asteroseismology observations of their progenitors and successors Methods: We calculated new 2 M☉, Z = 0.01 models rotating at 0, 125, and 250 km s-1 at the start of mai sequence. An artificial, additional viscosity was added to enhance th transport of angular momentum in order to reduce the core rotation rate to be in agreement with asteroseismology observations. We compare rotation rates of our models with observed rotation rates during the M up to the end of core He burning, and the white dwarf phase. Results: We present nucleosynthesis calculations for these rotating AG models that were enforced to match the asteroseismic constraints o rotation rates of MS, RGB, He-burning, and WD stars. In particular, w calculated one model that matches the upper limit of observed rotatio rates of core He-burning stars and we also included a model that rotate one order of magnitude faster than the upper limit of the observations The s-process production in both of these models is comparable to tha of non-rotating models. Conclusions: Slowing down the cor rotation rate in stars to match the above mentioned asteroseismi constraints reduces the rotationally induced mixing processes to th point that they have no effect on the s-process nucleosynthesis. Thi result is independent of the initial rotation rate of the stella evolution model. However, there are uncertainties remaining in th treatment of rotation in stellar evolution, which need to be reduced i order to confirm our conclusions, including the physical nature of ou approach to reduce the core rotation rates of our models, and magneti processes. This paper is dedicated to the celebration of the 100t birthday of Prof. Dr. Margaret Burbidge, in recognition of th outstanding contributions she has made to nuclear astrophysics

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