2023/06/16 by Yandow, I. T., Abdullah-Smoot, A., Bollen, G. +12
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Nuclear Experiment (nucl-ex)
paper · doi:10.48550/arxiv.2306.10163
Light curves are the primary observable of type-I x-ray bursts. Computational x-ray burst models must match simulations to observed light curves. Most of the error in simulated curves comes from uncertainties in rp process reaction rates, which can be reduced via precision mass measurements of neutron-deficient isotopes in the rp process path. We perform a precise Penning trap mass measurement of 27P utilizing the ToF-ICR technique. We use this measurement to calculate rp process reaction rates and input these rates into an x-ray burst model to reduce simulated light curve uncertainty. We also use the mass measurement of 27P to validate the Isobaric Multiplet Mass Equation (IMME) for the A=27 T=(3)/(2) isospin quartet which 27P belongs to. The mass excess of 27P was measured to be -670.7(6) keV, a fourteen-fold precision increase over the mass reported in the 2020 Atomic Mass Evaluation (AME2020). X-ray burst light curves were produced with the MESA (Modules for Experiments in Stellar Astrophysics) code using the new mass and associated reaction rates. Changes in the mass of 27P seem to have minimal effect on light curves, even in burster systems tailored to maximize impact. The mass of 27P does not play a significant role in x-ray burst light curves. It is important to understand that more advanced models do not just provide more precise results, but often qualitatively different ones. This result brings us a step closer to extracting stellar parameters from individual x-ray burst observations. The IMME has been validated for the A=27, T=3/2 quartet. The normal quadratic form of the IMME using the latest data yields a reduced χ2 of 2.9. The cubic term required to generate an exact fit to the latest data matches theoretical attempts to predict this term.