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1. Measuring the ¹⁵ O( α , γ ) ¹⁹ Ne Reaction in Type I X-ray Bursts using the GADGET II TPC: Software

   https://doi.org/10.1051/epjconf/202226011034  

   Mahajan, Ruchi; Adams, A.; Allmond, J.; Alvarez Pol, H.; Argo, E.; Ayyad, Y.; Bardayan, D.; Bazin, D.; Budner, T.; Chen, A.; et al (January 2022, EPJ Web of Conferences)

   Liu, W.; Wang, Y.; Guo, B.; Tang, X.; Zeng, S. (Ed.)

   15 O( α , γ ) 19 Ne is regarded as one of the most important thermonuclear reactions in type I X-ray bursts. For studying the properties of the key resonance in this reaction using β decay, the existing Proton Detector component of the Gaseous Detector with Germanium Tagging (GADGET) assembly is being upgraded to operate as a time projection chamber (TPC) at FRIB. This upgrade includes the associated hardware as well as software and this paper mainly focusses on the software upgrade. The full detector set up is simulated using the ATTPCROOTv 2 data analysis framework for 20 Mg and 241 Am. 

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2. The resonances in the $$^{22}$$Ne+$$\alpha $$ fusion reactions

   https://doi.org/10.1140/epja/s10050-023-00917-9  

   Wiescher, M.; deBoer, R. J.; Görres, J. (January 2023, The European Physical Journal A)

   Abstract The interplay and correlation between the $$^{22}$$ 22 Ne $$(\alpha ,\gamma )^{26}$$ ( α , γ ) 26 Mg and the competing $$^{22}$$ 22 Ne $$(\alpha ,n)^{25}$$ ( α , n ) 25 Mg reaction plays an important role for the interpretation of the $$^{22}$$ 22 Ne $$(\alpha ,n)^{25}$$ ( α , n ) 25 Mg reaction as a neutron source in the s - and n -processes. This paper provides a summary and new data on the $$\alpha $$ α -cluster and single-particle structure of the compound nucleus $$^{26}$$ 26 Mg and the impact on the reaction rate of these two competing processes in stellar helium burning environments. 

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3. Seismic Signatures of the ¹² C(α, γ) ¹⁶ O Reaction Rate in White Dwarf Models with Overshooting

   https://doi.org/10.3847/1538-4357/ace620  

   Chidester, Morgan T; Timmes, F X; Farag, Ebraheem (August 2023, The Astrophysical Journal)

   Abstract We consider the combined effects that overshooting and the¹²C(α,γ)¹⁶O reaction rate have on variable white dwarf (WD) stellar models. We find that carbon–oxygen (CO) WD models continue to yield pulsation signatures of the current experimental¹²C(α,γ)¹⁶O reaction rate probability distribution function when overshooting is included in the evolution. These signatures hold because the resonating mantle region, encompassing ≃0.2M_⊙in a typical ≃0.6M_⊙WD model, still undergoes radiative helium burning during the evolution to a WD. Our specific models show two potential low-order adiabatic g-modes,g₂andg₆, that signalize the¹²C(α,γ)¹⁶O reaction rate probability distribution function. Both g-mode signatures induce average relative period shifts of ΔP/P= 0.44% and ΔP/P= 1.33% forg₂andg₆, respectively. We find thatg₆is a trapped mode, and theg₂period signature is inversely proportional to the¹²C(α,γ)¹⁶O reaction rate. Theg₆period signature generally separates the slower and faster reaction rates, and has a maximum relative period shift of ΔP/P= 3.45%. We conclude that low-order g-mode periods from CO WDs may still serve as viable probes for the¹²C(α,γ)¹⁶O reaction rate probability distribution function when overshooting is included in the evolution. 

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4. Impact of the New ⁶⁵ As(p,γ) ⁶⁶ Se Reaction Rate on the Two-proton Sequential Capture of ⁶⁴ Ge, Weak GeAs Cycles, and Type I X-Ray Bursts Such as the Clocked Burster GS 1826−24

   https://doi.org/10.3847/1538-4357/ac4d8b  

   Lam, Yi Hua; Liu, Zi Xin; Heger, Alexander; Lu, Ning; Jacobs, Adam Michael; Johnston, Zac (April 2022, The Astrophysical Journal)

   Abstract We reassess the 65 As(p, γ ) 66 Se reaction rates based on a set of proton thresholds of 66 Se, S p ( 66 Se), estimated from the experimental mirror nuclear masses, theoretical mirror displacement energies, and full p f -model space shell-model calculation. The self-consistent relativistic Hartree–Bogoliubov theory is employed to obtain the mirror displacement energies with much reduced uncertainty, and thus reducing the proton-threshold uncertainty up to 161 keV compared to the AME2020 evaluation. Using the simulation instantiated by the one-dimensional multi-zone hydrodynamic code, K epler , which closely reproduces the observed GS 1826−24 clocked bursts, the present forward and reverse 65 As(p, γ ) 66 Se reaction rates based on a selected S p ( 66 Se) = 2.469 ± 0.054 MeV, and the latest 22 Mg( α ,p) 25 Al, 56 Ni(p, γ ) 57 Cu, 57 Cu(p, γ ) 58 Zn, 55 Ni(p, γ ) 56 Cu, and 64 Ge(p, γ ) 65 As reaction rates, we find that though the GeAs cycles are weakly established in the rapid-proton capture process path, the 65 As(p, γ ) 66 Se reaction still strongly characterizes the burst tail end due to the two-proton sequential capture on 64 Ge, not found by the Cyburt et al. sensitivity study. The 65 As(p, γ ) 66 Se reaction influences the abundances of nuclei A = 64, 68, 72, 76, and 80 up to a factor of 1.4. The new S p ( 66 Se) and the inclusion of the updated 22 Mg( α ,p) 25 Al reaction rate increases the production of 12 C up to a factor of 4.5, which is not observable and could be the main fuel for a superburst. The enhancement of the 12 C mass fraction alleviates the discrepancy in explaining the origin of the superburst. The waiting point status of and two-proton sequential capture on 64 Ge, the weak-cycle feature of GeAs at a region heavier than 64 Ge, and the impact of other possible S p ( 66 Se) are also discussed. 

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5. ²⁰ Ne(α,p) ²³ Na studied to constrain type Ia nucleosynthesis

   https://doi.org/10.1088/1742-6596/2586/1/012110  

   Boomershine, C N; Bardayan, D W; Carmichael, S; Caves, L; Davis, A; deBoer, R J; Gula, A; Howard, K; Kelmar, R; Mitchell, A; et al (September 2023, Journal of Physics: Conference Series)

   Abstract The²⁰Ne(α,p)²³Na reaction rate is important in determining the final abundances of various nuclei produced in type Ia supernovae. Previously, the ground state cross section was calculated from time reversal reaction experiments using detailed balance. The reaction rates extracted from these studies do not consider contributions from the population of excited states, and therefore, are only estimates. A resonance scan, populating both the ground and first excited states, was performed for the²⁰Ne(α,p)²³Na reaction, measuring between 2.9 and 5 MeV center of mass energies at the Nuclear Science Lab at the University of Notre Dame. Data analysis is underway and preliminary results show substantial contribution from the excited state reaction. 

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