Abstract
The presence of a strong shallow heat source of unknown origin in accreting neutron star crusts has been inferred by analyzing x-ray observations of their cooling in quiescence. We model the cooling of KS 1731-260 using realistic crust compositions and nuclear heating and cooling sources from detailed nuclear reaction network calculations. We find that the required strength of the shallow heat source in KS 1731-260 is reduced by more than a factor of 3 compared to previous analysis, a 5σ difference that alleviates the need for exotic solutions. Our analysis also suggests the existence of an impure nuclear pasta layer in the inner crust of KS 1731-260, though future observations will provide more stringent constraints. In addition, we obtain constraints on the dominant surface burning modes of KS 1731-260 over its history.
| Original language | English |
|---|---|
| Article number | 162701 |
| Journal | Physical Review Letters |
| Volume | 135 |
| Issue number | 16 |
| DOIs | |
| State | Published - Oct 17 2025 |
Funding
This work was supported by the National Science Foundation under Awards No. PHY-1430152 (JINA Center for the Evolution of the Elements), No. OISE-1927130 (IReNA), No. PHY-1913554, and No. PHY-2209429, and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0013037. E. F. B. acknowledges support under Grant No. 80NSSC20K0503 from NASA. This was work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.