Abstract
Type I x-ray bursts occur at astrophysical sites where a neutron star accretes H/He-rich matter from a companion star, leading to nuclear burning on the neutron star surface. The only observable is the x-ray burst light curve, which is used as a unique diagnostic of the outer layers of accreting neutron stars such as the accretion rate and fuel composition. In addition to the astrophysical conditions, the main determinant of the shape of the light curve is the nuclear physics involved. Variations within the uncertainty of the 23Al(p,γ)24Si reaction rate lead to significant shifts in simulated x-ray light curves, where the ground state mass of 24Si is currently the dominant source of the reaction rate uncertainty (19 keV). A high-precision mass measurement of 24Si was performed with the LEBIT facility at the National Superconducting Cyclotron Laboratory. The atomic mass excess, 10 753.8(37) keV, is a factor of 5 more precise than previous results. This substantially reduces the uncertainty of the 23Al(p,γ)24Si reaction rate, which is a key part of the rapid proton capture (rp) process powering type I x-ray bursts. The updated rate constrains the onset temperature of the (α,p) process at the 22Mg waiting point to a precision of 9%.
*This material is based upon work supported by the U.S. National Science Foundation through Grants No. PHY-1565546, PHY-2111185 (The Precision Frontier at FRIB: Masses, Radii, Moments, and Fundamental Interactions), PHY-1430152 (Joint Institute for Nuclear Astrophysics -- Center for the Evolution of the Elements), and No. PHY-191355, as well as the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Grants No. DE-FG02-88ER40387, DE-SC0019042, DE-NA0003909, and DE-SC0015927. A.A.V. acknowledges support from NSERC (Canada) under Contract No. SAPPJ2018-00028. Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
