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After decades, the theoretical study of core-collapse supernova explosions is moving from parameterized, spherically symmetric models to increasingly realistic multidimensional simulations. However, obtaining nucleosynthesis yields based on such multidimensional core-collapse supernova simulations is not straightforward. Frequently, tracer particles are employed. Tracer particles may be tracked in situ during the simulation, but often they are reconstructed in a post-processing step based on the information saved during the hydrodynamic simulation. Reconstruction can be done in a number of ways, and here we compare the approaches of backward and forward integration of the equations of motion to the results based on inline particle trajectories. We find that both methods agree reasonably well with the inline results for isotopes for which a large number of particles contribute. However, for rarer isotopes that are produced only by a small number of particle trajectories, deviations can be large. For our setup, we find that backward integration leads to better agreement with the inline particles by more accurately reproducing the conditions following freeze-out from nuclear statistical equilibrium, because the establishment of nuclear statistical equilibrium erases the need for detailed trajectories at earlier times. Based on our results, if inline tracers are unavailable, we recommend backward reconstruction to the point when nuclear statistical equilibrium was last applied, with an interval between simulation snapshots of at most 1 ms for nucleosynthesis post-processing.

 

We compare the core-collapse evolution of a pair of 15.8M_☉stars with significantly different internal structures, a consequence of the bimodal variability exhibited by massive stars during their late evolutionary stages. The 15.78 and 15.79M_☉progenitors have core masses (masses interior to an entropy of 4k_Bbaryon⁻¹) of 1.47 and 1.78M_☉and compactness parametersξ_1.75of 0.302 and 0.604, respectively. The core-collapse simulations are carried out in 2D to nearly 3 s postbounce and show substantial differences in the times of shock revival and explosion energies. The 15.78M_☉model begins exploding promptly at 120 ms postbounce when a strong density decrement at the Si–Si/O shell interface, not present in the 15.79M_☉progenitor, encounters the stalled shock. The 15.79M_☉model takes 100 ms longer to explode but ultimately produces a more powerful explosion. Both the larger mass accretion rate and the more massive core of the 15.79M_☉model during the first 0.8 s postbounce time result in largerν_e/${\overline{\nu }}_e$luminosities and RMS energies along with a flatter and higher-density heating region. The more-energetic explosion of the 15.79M_☉model resulted in the ejection of twice as much⁵⁶Ni. Most of the ejecta in both models are moderately proton rich, though counterintuitively the highest electron fraction (Y_e= 0.61) ejecta in either model are in the less-energetic 15.78M_☉model, while the lowest electron fraction (Y_e= 0.45) ejecta in either model are in the 15.79M_☉model.

 

For students with visual impairments (VI), the possibility of a future in astronomy, or any science, technology, engineering, and mathematics (STEM) field, seems daunting. In order to bolster astronomy and STEM opportunities for high school students with VI in the United States, we developed the STEM Career Exploration Lab (CEL). Our STEM CEL methodology employs tactile astronomy instruction via 3D printing technologies and unique 3D-printed models, professionals with VI acting as role models, and partnerships with local STEM industries that provide insights into possible career paths. In partnership with the South Carolina Commission for the Blind (SCCB) and the Michigan Bureau of Services for Blind Persons (MBSBP), to date we have held four weeklong CELs (June 2017, June & July 2018, August 2019) and a 3D printer build workshop (September 2018), thus far serving about fifty students with VI. We have also held one professional development workshop for teachers of the visually impaired at the Maryland School for the Blind in October 2021. We gathered pre- and post-intervention data via student surveys, assessments of students' astronomy knowledge, and video recordings of the CEL activities in order to study to what extent the CEL model can enhance the students' attitudes towards, interests in, and capacities to participate in astronomy and STEM careers. Once fully tested and refined, we will make our 3D model files and activities freely available for further use and study. This work serves as a testbed for an expanded CEL program aimed at helping increase the representation of persons with VI in astronomy and STEM fields. This work is supported by a generous Innovative Technology Experiences for Students and Teachers (ITEST) grant from the National Science Foundation.