Developing a 1D stellar evolution model for rotating massive stars to study evolution of the weak s-process elements in the galaxy

Massive stars create elements heavier than Fe by producing intense neutron fluxes during the He-core and C-shell burning via the ²²Ne(α,n)²⁵Mg reaction (weak s-process). The resulting s-process products are ejected into the interstellar space via core-collapse supernova (CCSN) explosions, enriching heavy elements in the galaxy. Accurate predictions of the s-process nucleosynthesis yields and, further, galactic chemical evolution (GCE) are limited partly due to the uncertain cross sections of the ²²Ne(α,n) and its competitor, ²²Ne(α,γ) reaction. In the first part of our work, we probe the impact of the latest ²²Ne+α reaction rates on the nucleosynthesis and GCE of the s-process elements. We perform nucleosynthesis simulations using MPPNP multi-zone post-processing code [1], following stellar evolution track simulated with MESA [2], and estimate the yields of the s-process elements ejected from the CCSN. Evolution of these elements in the galaxy are then simulated with the OMEGA+ code [3]. We find that when using the two latest rates [4,5], the variations of GCE curves reduce from those calculated by our previous research [6] using other rates. The new GCE curves, however, agree less with observations. These results indicate that the ²²Ne+α rates are still poorly constrained, which can be drastically improved by ongoing underground experiments [7]. In the second part of our work, we added stellar rotation effects to the stellar evolution track used in our simulations to test the sensitivity of the GCE curves to stellar models. The preliminary results with 15 M_⊙ at solar metallicity proved the sensitivity. Thus, we are currently developing a new 1D stellar model for a variety of massive stars.