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1. Comparison of the Core-collapse Evolution of Two Nearly Equal-mass Progenitors

   Bruenn, S; Sieverding, A; Lentz, E; Sukhbold, T; Hix, W; Huk, L; Harris, J; Messer, O; Mezzacappa, A (April 2023, The Astrophysical journal)

   We compare the core-collapse evolution of a pair of 15.8 M☉ 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 15.79 M☉ progenitors have core masses (masses interior to an entropy of 4 kB baryon−1) of 1.47 and 1.78 M☉ and compactness parameters ξ1.75 of 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 15.78 M☉ model begins exploding promptly at 120 ms postbounce when a strong density decrement at the Si– Si/O shell interface, not present in the 15.79 M☉ progenitor, encounters the stalled shock. The 15.79 M☉ 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 15.79 M☉ model during the first 0.8 s postbounce time result in larger νe/n ̄e luminosities and RMS energies along with a flatter and higher-density heating region. The more-energetic explosion of the 15.79 M☉ model resulted in the ejection of twice as much 56Ni. Most of the ejecta in both models are moderately proton rich, though counterintuitively the highest electron fraction (Ye = 0.61) ejecta in either model are in the less-energetic 15.78 M☉ model, while the lowest electron fraction (Ye = 0.45) ejecta in either model are in the 15.79 M☉ model. 

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2. Comparison of the Core-collapse Evolution of Two Nearly Equal-mass Progenitors

   https://doi.org/10.3847/1538-4357/acbb65  

   Bruenn, Stephen W.; Sieverding, Andre; Lentz, Eric J.; Sukhbold, Tuguldur; Hix, W. Raphael; Huk, Leah N.; Harris, J. Austin; Messer, O. E. Bronson; Mezzacappa, Anthony (April 2023, The Astrophysical Journal)

   Abstract 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. 

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3. Isotopic ratios for C, N, Si, Al, and Ti in C-rich presolar grains from massive stars

   https://doi.org/10.1093/mnras/stac2498  

   Schofield, Jordan; Pignatari, Marco; Stancliffe, Richard J; Hoppe, Peter (October 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Certain types of silicon carbide (SiC) grains, e.g. SiC-X grains, and low density (LD) graphites are C-rich presolar grains that are thought to have condensed in the ejecta of core-collapse supernovae (CCSNe). In this work, we compare C, N, Al, Si, and Ti isotopic abundances measured in presolar grains with the predictions of 21 CCSN models. The impact of a range of SN explosion energies is considered, with the high energy models favouring the formation of a C/Si zone enriched in 12C, 28Si, and 44Ti. Eighteen of the 21 models have H ingested into the He-shell and different abundances of H remaining from such H-ingestion. CCSN models with intermediate to low energy (that do not develop a C/Si zone) cannot reproduce the 28Si and 44Ti isotopic abundances in grains without assuming mixing with O-rich CCSN ejecta. The most 28Si-rich grains are reproduced by energetic models when material from the C/Si zone is mixed with surrounding C-rich material, and the observed trends of the 44Ti/48Ti and 49Ti/48Ti ratios are consistent with the C-rich C/Si zone. For the models with H-ingestion, high and intermediate explosion energies allow the production of enough 26Al to reproduce the 26Al/27Al measurements of most SiC-X and LD graphites. In both cases, the highest 26Al/27Al ratio is obtained with H still present at XH ≈ 0.0024 in He-shell material when the SN shock is passing. The existence of H in the former convective He-shell points to late H-ingestion events in the last days before massive stars explode as a supernova. 

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4. Physics-driven Explosions of Stripped High-mass Stars: Synthetic Light Curves and Spectra of Stripped-envelope Supernovae with Broad Light Curves

   https://doi.org/10.3847/1538-4357/ada26d  

   Lu_陆, Jing_晶; Barker, Brandon_L; Goldberg, Jared; Kerzendorf, Wolfgang_E; Modjaz, Maryam; Couch, Sean_M; Shields, Joshua_V; Fullard, Andrew_G (January 2025, The Astrophysical Journal)

   Abstract Stripped-envelope supernovae (SESNe) represent a significant fraction of core-collapse supernovae, arising from massive stars that have shed their hydrogen and, in some cases, helium envelopes. The origins and explosion mechanisms of SESNe remain a topic of active investigation. In this work, we employ radiative-transfer simulations to model the light curves and spectra of a set of explosions of single, solar-metallicity, massive Wolf–Rayet stars with ejecta masses ranging from 4 to 11M_⊙, which were computed from a turbulence-aided and neutrino-driven explosion mechanism. We analyze these synthetic observables to explore the impact of varying ejecta mass and helium content on observable features. We find that the light curve shape of these progenitors with high ejecta masses is consistent with observed SESNe with broad light curves but not the peak luminosities. The commonly used analytic formula based on rising bolometric light curves overestimates the ejecta mass of these high-initial-mass progenitor explosions by a factor of up to 2.6. In contrast, the calibrated method by Haynie et al., which relies on late-time decay tails, reduces uncertainties to an average of 20% within the calibrated ejecta mass range. Spectroscopically, the He i1.083μm line remains prominent even in models with as little as 0.02M_⊙of helium. However, the strength of the optical He ilines is not directly proportional to the helium mass but instead depends on a complex interplay of factors such as the⁵⁶Ni distribution, composition, and radiation field. Thus, producing realistic helium features requires detailed radiative transfer simulations for each new hydrodynamic model. 

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5. Radioactive nuclei in the early Solar system: analysis of the 15 isotopes produced by core-collapse supernovae

   https://doi.org/10.1093/mnras/stab3684  

   Lawson, Thomas V; Pignatari, Marco; Stancliffe, Richard J; den Hartogh, Jacqueline; Jones, Sam; Fryer, Chris L; Gibson, Brad K; Lugaro, Maria (February 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Short-lived radioactive isotopes (SLRs) with half-lives between 0.1 and 100 Myr can be used to probe the origin of the Solar system. In this work, we examine the core-collapse supernovae production of the 15 SLRs produced: 26Al, 36Cl, 41Ca, 53Mn, 60Fe, 92Nb, 97Tc, 98Tc, 107Pd, 126Sn, 129I, 135Cs, 146Sm, 182Hf, and 205Pb. We probe the impact of the uncertainties of the core-collapse explosion mechanism by examining a collection of 62 core-collapse models with initial masses of 15, 20, and 25 M⊙, explosion energies between 3.4 × 1050 and 1.8 × 1052 erg and compact remnant masses between 1.5 and 4.89 M⊙. We identify the impact of both explosion energy and remnant mass on the final yields of the SLRs. Isotopes produced within the innermost regions of the star, such as 92Nb and 97Tc, are the most affected by the remnant mass, 92Nb varying by five orders of magnitude. Isotopes synthesized primarily in explosive C-burning and explosive He-burning, such as 60Fe, are most affected by explosion energies. 60Fe increases by two orders of magnitude from the lowest to the highest explosion energy in the 15 M⊙ model. The final yield of each examined SLR is used to compare to literature models. 

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