星が死ぬと何が起こるのか？新研究が解明に前進（What happens when a star dies? New research gets closer to an answer）

2026-09-08 アルゴンヌ国立研究所（ANL）

This image features the star cluster Trumpler 14, one of the largest gatherings of hot, massive and bright stars in the Milky Way. (Representative Cover Image Source: NASA & ESA, Jesús Maíz Apellániz (Instituto de Astrofisica de Andalucia))

＜関連情報＞

• https://starlust.org/what-happens-when-a-star-dies-new-research-gets-closer-to-an-answer/
• https://journals.aps.org/prl/abstract/10.1103/gbbj-hpqk
• https://journals.aps.org/prl/abstract/10.1103/9zv2-wlkl

不安定な単一核子転送59Cu天体物理学的X線バーストにおけるNiCuサイクルの探査 Single-Nucleon Transfer on Unstable 59Cu Probes the NiCu Cycle in Astrophysical X-Ray Bursts

C. O’Shea, G. Lotay, A. Gade, D. T. Doherty, H. Schatz, J. S. Randhawa, B. A. Brown, D. Weisshaar, J. Pereira et al.
Physical areviw Letters  Published: 6 July, 2026
DOI: https://doi.org/10.1103/gbbj-hpqk

Abstract

Recent models of the rapid proton (⁢) capture process indicate that a competition between the ⁵⁹Cu⁢(,)⁢⁶⁰Zn and ⁵⁹Cu⁢(,)⁢⁵⁶Ni reactions may result in the formation of a nickel-copper (NiCu) cycle that traps the flux of material between ⁵⁶Ni and ⁶⁰Zn. Here, we report the identification of 15 proton-unbound levels in ⁶⁰Zn, populated via ⁵⁹Cu⁢(,) transfer, which govern the rate of the ⁵⁹Cu⁢(,)⁢⁶⁰Zn reaction in XRBs. Precise excitation energies for levels in ⁶⁰Zn were obtained from observed decays, and spectroscopic factors were determined from angle-integrated cross sections. Incorporating these results into stellar-model calculations, we find that with experimentally constrained uncertainties a NiCu cycle in XRBs is indeed possible, though we limit its branching strength to less than 38%. While modest, such a branching has significant impact on the light curve, motivating further studies of the relevant rates. Our calculations also indicate that a significant NiCu cycle leads to an increase in the amount of odd- nuclei in the burst ashes, which may affect Urca cooling processes in neutron star crusts.

45V⁡(p,γ)⁢46Cr反応における共鳴状態の同定と、それらがコア崩壊型超新星における44Ti生成に及ぼす影響 Identification of Resonant States in the 45V⁡(,)⁢46Cr Reaction and Their Influence on the Production of 44Ti in Core-Collapse Supernovae

C. Cousins, G. Lotay, D. T. Doherty, D. Seweryniak, C. Sarma, C. M. Campbell, L. Canete, M. P. Carpenter, W. N. Catford et al.
Physical Review Letters  Published: 23 June, 2026
DOI: https://doi.org/10.1103/9zv2-wlkl

Abstract

The observation of active ⁴⁴Ti in supernova remnants offers the potential to solve one of the most debated questions in modern astrophysics, the exact underlying explosion mechanism of core collapse supernovae (CCSNe). In particular, a comparison between the predicted synthesized yield of 44Ti and the ejected flux is expected to allow for a determination of the mass cut of the star. Unfortunately, such comparisons are currently severely hindered by large uncertainties in the nuclear reactions governing the production and destruction of ⁴⁴Ti. On this note, the astrophysical ⁴⁵V⁡(,)⁢⁴⁶Cr reaction is expected to play a decisive role. We present the first experimental information on resonant states in the ⁴⁵V⁡(,)⁢⁴⁶Cr reaction. Excitation energies have been measured with high precision for ten previously unknown, low-spin, proton-unbound states in ⁴⁶Cr, and spin-parity-assignment constraints have been made using observed -decay patterns and shell-model calculations. We find that an ℓ =1 resonance at 714 keV dominates the ⁴⁵V⁡(,)⁢⁴⁶Cr reaction for the entire temperature range of -rich freezeout. Moreover, the nominal rate is found to be ∼25–50% of previous estimates for >1.2  GK, indicating an increase in ⁴⁴Ti production in CCSNe of ∼20–35%.