DOE OSTI · 3385861
Single-Nucleon Transfer on Unstable 59 Cu Probes the NiCu Cycle in Astrophysical X-Ray Bursts
Abstract
Recent models of the rapid proton (𝑟𝑝) capture process indicate that a competition between the 59 Cu(𝑝,𝛾) 60 Zn and 59 Cu(𝑝,𝛼) 56 Ni reactions may result in the formation of a nickel-copper (NiCu) cycle that traps the flux of material between 56 Ni and 60 Zn . Here, in this work, we report the identification of 15 proton-unbound levels in 60 Zn , populated via 59 Cu(𝑑,𝑛) transfer, which govern the rate of the 59 Cu(𝑝,𝛾) 60 Zn reaction in XRBs. Precise excitation energies for levels in 60 Zn were obtained from observed 𝛾 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-𝐴 nuclei in the burst ashes, which may affect Urca cooling processes in neutron star crusts.
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O’Shea, C. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0009000605079274), Lotay, G. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000229187599), Gade, A. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000188250976), Doherty, D. T. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:000000025006370X), Schatz, H. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000316744859), Randhawa, J. S. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Mississippi State Univ., Starkville, MS (United States)] (ORCID:0000000168603754), Brown, B. A. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000261111906), Weisshaar, D. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000291903971), Pereira, J. [Michigan State Univ., East Lansing, MI (United States)], Gillespie, S. A. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:000000019268518X), Bardayan, D. W. [University of Notre Dame, IN (United States)] (ORCID:000000023185491X), Byrne, S. [Univ. of Massachusetts, Lowell, MA (United States)] (ORCID:0000000229295450), Canete, L. [Univ. of Surrey, Guildford (United Kingdom); Centre National de la Recherche Scientifique (CNRS), Caen (France). Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), Grand Accelerateur National d'Ions Lourds (GANIL)] (ORCID:0000000242296386), Catford, W. N. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000256201181), Cerizza, G. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0009000510639996), Chester, A. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000276257772), Chung-Jung, J. [Michigan State Univ., East Lansing, MI (United States)], Cousins, C. [Univ. of Surrey, Guildford (United Kingdom)], Coil, S. [University of Notre Dame, IN (United States); Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000212404315), Crawford, H. L. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000277654235), Giraud, S. [Michigan State Univ., East Lansing, MI (United States); Univ. Paris-Saclay (France)], Good, E. [Michigan State Univ., East Lansing, MI (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)] (ORCID:0000000177656188), Grauvogel, G. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0009000023601173), Harca, I. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000231824876), Heery, J. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000230239907), Hill, A. [Michigan State Univ., East Lansing, MI (United States)], Jain, R. [Michigan State Univ., East Lansing, MI (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000198591512), Maher, C. [Michigan State Univ., East Lansing, MI (United States)], Montes, F. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000198495555), Müller-Gatermann, C. [Argonne National Laboratory (ANL), Argonne, IL (United States)] (ORCID:0000000291815568), Noji, S. [Michigan State Univ., East Lansing, MI (United States)], Pathirana, N. D. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0009000244514874), Parry, T. [Univ. of Surrey, Guildford (United Kingdom); Michigan State Univ., East Lansing, MI (United States)] (ORCID:000900077568061X), Paxman, C. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000309962276), Rogers, A. M. [Univ. of Massachusetts, Lowell, MA (United States)] (ORCID:0000000297155652), Sebastian, A. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0009000246126146), Sultana, I. [Central Michigan Univ., Mount Pleasant, MI (United States)] (ORCID:0000000254760369), Swartz, J. A. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000259992791), Tsantiri, A. [Michigan State Univ., East Lansing, MI (United States); Univ. of Regina, SK (Canada)] (ORCID:0000000297593476), Uthayakumaar, S. [Michigan State Univ., East Lansing, MI (United States)] (ORCID:0000000231540734), Zegers, R. G. T. [Michigan State Univ., East Lansing, MI (United States)]. 2026-07-06. Single-Nucleon Transfer on Unstable 59 Cu Probes the NiCu Cycle in Astrophysical X-Ray Bursts. https://doi.org/10.1103/gbbj-hpqk
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