كيف تزن التيتانيوم في المستعر الأعظم سريع

الملخص الأصلي

كما كتبه المؤلفون، بالإنجليزية arXiv:2608.17757v1

The thermonuclear $$^{45}$$V($$p,\gamma$$)$$^{46}$$Cr reaction is the primary leakage pathway from the $$^{44}$$Ti--$$^{45}$$V quasi-equilibrium cluster during $$\alpha$$-rich freeze-out in core-collapse supernovae (CCSN), governing the final abundance of the $$\gamma$$-ray-emitting isotope $$^{44}$$Ti. A recent high-resolution $$\gamma$$-ray study [C. Cousins \textit{et al.}, Phys. Rev. Lett. 136, 252701 (2026)] identified ten previously unknown low-spin proton-unbound states in $$^{46}$$Cr, enabling the first experimentally constrained $$^{45}$$V($$p,\gamma$$)$$^{46}$$Cr reaction rate using the AME2020 mass excess, $$\text{ME}(^{46}\text{Cr}) = -29472(11)$$~keV. Here, we adopt the four-fold more precise CSRe mass excess $$\text{ME}(^{46}\text{Cr}) = -29477.2(2.6)$$~keV [M.~Wang \textit{et al.}, Phys. Rev. C \textbf{106}, L051301 (2022)] to recalculate the reaction rate. Including proton capture on the ground and first two excited states of $$^{45}$$V alongside new shell-model proton spectroscopic factors, we reduce mass-related rate uncertainties to a subdominant level. The revised rate is up to 69% higher than that of Cousins \textit{et al.} at $$\alpha$$-rich freeze-out temperatures ($$T \simeq 1.5$$--$$2$$~GK). CCSN nucleosynthesis calculations show this revised rate increases the ejected $$^{44}$$Ti yield by $$\sim$$26% in a $$20\,M_\odot$$ model compared to The \textit{et al.} [ApJ \textbf{504}, 500 (1998)], while causing negligible changes for the SN~1987A trajectory. We demonstrate that $$^{44}$$Ti production sensitivity is dictated by the ejecta electron fraction ($$Y_e$$): the reaction significantly affects proton-rich ejecta ($$Y_e \approx 0.50$$) but has little impact on neutron-rich ejecta ($$Y_e \approx 0.496$$), where lower free-proton abundances suppress reaction flow. This reconciles conflicting results from past sensitivity studies.