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Published August 2019 | Published
Journal Article Open

Akmal-Pandharipande-Ravenhall equation of state for simulations of supernovae, neutron stars, and binary mergers

Abstract

Differences in the equation of state (EOS) of dense matter translate into differences in astrophysical simulations and their multimessenger signatures. Thus, extending the number of EOSs for astrophysical simulations allows us to probe the effect of different aspects of the EOS in astrophysical phenomena. In this work, we construct the EOS of hot and dense matter based on the Akmal, Pandharipande, and Ravenhall (APR) model and thereby extend the open-source SROEOS code which computes EOSs of hot dense matter for Skyrme-type parametrizations of the nuclear forces. Unlike Skrme-type models, in which parameters of the interaction are fit to reproduce the energy density of nuclear matter and/or properties of heavy nuclei, the EOS of APR is obtained from potentials resulting from fits to nucleon-nucleon scattering and properties of light nuclei. In addition, this EOS features a phase transition to a spin-isospin ordered state of nucleons, termed a neutral pion condensate, at supranuclear densities. We show that differences in the effective masses between EOSs have consequences for the properties of nuclei in the subnuclear inhomogeneous phase of matter. We also test the new EOS of APR in spherically symmetric core-collapse of massive stars with 15M⊙ and 40M⊙, respectively. We find that the phase transition in the EOS of APR speeds up the collapse of the star. However, this phase transition does not generate a second shock wave or another neutrino burst as reported for the hadron-to-quark phase transition. The reason for this difference is that the width of the coexistence region and the latent heat in the EOS of APR are substantially smaller than in the quark-to-hadron transition employed earlier, which results in a significantly smaller softening of the high density EOS.

Additional Information

© 2019 American Physical Society. Received 30 January 2019; revised manuscript received 27 May 2019; published 12 August 2019. We acknowledge helpful discussions with J. M. Lattimer. We are grateful to R. B. Wiringa for clarifications concerning the nature of the pion condensation used in the work of APR based on earlier works. A.S.S. was supported in part by the National Science Foundation under Award No. AST-1333520 and CAREER PHY-1151197. C.C., B.M., and M.P. acknowledge research support from US DOE Grant No. DE-FG02-93ER-40756. C.C. also acknowledges travel support from the National Science Foundation under Award No. PHY-1430152 (JINA Center for the Evolution of the Elements). This work benefited from discussions at the 2018 INT-JINA Symposium on "First multi-messenger observation of a neutron star merger and its implications for nuclear physics" supported by the National Science Foundation under Grant No. PHY-1430152 (JINA Center for the Evolution of the Elements) and also from discussions at the 2018 N3AS collaboration meeting of the "Research Hub for Fundamental Symmetries, Neutrinos, and Applications to Nuclear Astrophysics" supported by the National Science Foundation, Grant No. PHY-1630782, and the Heising-Simons Foundation, Grant No. 2017-228.

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Created:
August 19, 2023
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October 18, 2023