Detailed examination of astrophysical constraints on the symmetry energy and the neutron skin of Pb208 with minimal modeling assumptions

Reed Essick, Philippe Landry, Achim Schwenk, and Ingo Tews
Phys. Rev. C 104, 065804 – Published 15 December 2021

Abstract

The symmetry energy and its density dependence are pivotal for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. Recently, PREX-II reported a value of 0.283±0.071 fm for the neutron-skin thickness of Pb208, RskinPb208, implying a symmetry-energy slope parameter L of 106±37 MeV, larger than most ranges obtained from microscopic calculations and other nuclear experiments. We use a nonparametric equation of state representation based on Gaussian processes to constrain the symmetry energy S0, L, and RskinPb208 directly from observations of neutron stars with minimal modeling assumptions. The resulting astrophysical constraints from heavy pulsar masses, LIGO/Virgo, and NICER favor smaller values of the neutron skin and L, as well as negative symmetry incompressibilities. Combining astrophysical data with chiral effective field theory (χEFT) and PREX-II constraints yields S0=33.01.8+2.0 MeV, L=5315+14 MeV, and RskinPb208=0.170.04+0.04 fm. We also examine the consistency of several individual χEFT calculations with astrophysical observations and terrestrial experiments. We find that there is only mild tension between χEFT, astrophysical data, and PREX-II's RskinPb208 measurement (p value =12.3%) and that there is excellent agreement between χEFT, astrophysical data, and other nuclear experiments.

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  • Received 15 July 2021
  • Revised 29 October 2021
  • Accepted 19 November 2021

DOI:https://doi.org/10.1103/PhysRevC.104.065804

©2021 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & AstrophysicsNuclear Physics

Authors & Affiliations

Reed Essick1,2,*, Philippe Landry3,†, Achim Schwenk4,5,6,‡, and Ingo Tews7,§

  • 1Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5, Canada
  • 2Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, Illinois 60637, USA
  • 3Nicholas & Lee Begovich Center for Gravitational-Wave Physics & Astronomy, California State University, Fullerton, 800 N State College Blvd, Fullerton, California 92831, USA
  • 4Technische Universität Darmstadt, Department of Physics, 64289 Darmstadt, Germany
  • 5ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
  • 6Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
  • 7Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • *reed.essick@gmail.com
  • plandry@fullerton.edu
  • schwenk@physik.tu-darmstadt.de
  • §itews@lanl.gov

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Issue

Vol. 104, Iss. 6 — December 2021

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