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Title: NUCLEAR CONSTRAINTS ON PROPERTIES OF NEUTRON STAR CRUSTS

Abstract

The transition density {rho} {sub t} and pressure P{sub t} at the inner edge separating the liquid core from the solid crust of neutron stars are systematically studied using a modified Gogny (MDI) and 51 popular Skyrme interactions within well established dynamical and thermodynamical methods. First of all, it is shown that the widely used parabolic approximation to the full equation of state (EOS) of isospin asymmetric nuclear matter may lead to huge errors in estimating the transition density and pressure, especially for stiffer symmetry energy functionals E {sub sym}({rho}), compared to calculations using the full EOS within both the dynamical and thermodynamical methods mainly because of the energy curvatures involved. Thus, fine details of the EOS of asymmetric nuclear matter are important for locating accurately the inner edge of the neutron star crust. Second, the transition density and pressure decrease roughly linearly with increasing slope parameter L of E {sub sym}({rho}) at normal nuclear matter density using the full EOS within both the dynamical and thermodynamical methods. It is also shown that the thickness, fractional mass, and moment of inertia of the neutron star crust are all very sensitive to the parameter L through the transition density {rho} {submore » t} whether one uses the full EOS or its parabolic approximation. Moreover, it is shown that E {sub sym}({rho}) constrained in the same subsaturation density range as the neutron star crust by the isospin diffusion data in heavy-ion collisions at intermediate energies limits the transition density and pressure to 0.040 fm{sup -3} {<=}{rho} {sub t} {<=} 0.065 fm{sup -3} and 0.01 MeV fm{sup -3} {<=}P{sub t} {<=} 0.26 MeV fm{sup -3}, respectively. These constrained values for the transition density and pressure are significantly lower than their fiducial values currently used in the literature. Furthermore, the mass-radius relation and several other properties closely related to the neutron star crust are studied by using the MDI interaction. It is found that the newly constrained {rho} {sub t} and P{sub t} together with the earlier estimate of {delta}I/I>0.014 for the crustal fraction of the moment of inertia of the Vela pulsar impose a more stringent constraint of R {>=} 4.7 + 4.0M/M {sub sun} km for the radius R and mass M of neutron stars compared to previous studies in the literature.« less

Authors:
; ;  [1]
  1. Institute of Theoretical Physics, Shanghai Jiao Tong University, Shanghai 200240 (China)
Publication Date:
OSTI Identifier:
21307947
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 697; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/697/2/1549; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; APPROXIMATIONS; ASYMMETRY; DENSITY; EQUATIONS OF STATE; FUNCTIONALS; HEAVY ION REACTIONS; ISOSPIN; MASS; MOMENT OF INERTIA; NEUTRON STARS; NEUTRONS; NUCLEAR MATTER; PULSARS; SKYRME POTENTIAL

Citation Formats

Jun, Xu, Liewen, Chen, Hongru, Ma, and Li Baoan. NUCLEAR CONSTRAINTS ON PROPERTIES OF NEUTRON STAR CRUSTS. United States: N. p., 2009. Web. doi:10.1088/0004-637X/697/2/1549; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Jun, Xu, Liewen, Chen, Hongru, Ma, & Li Baoan. NUCLEAR CONSTRAINTS ON PROPERTIES OF NEUTRON STAR CRUSTS. United States. https://doi.org/10.1088/0004-637X/697/2/1549; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)
Jun, Xu, Liewen, Chen, Hongru, Ma, and Li Baoan. 2009. "NUCLEAR CONSTRAINTS ON PROPERTIES OF NEUTRON STAR CRUSTS". United States. https://doi.org/10.1088/0004-637X/697/2/1549; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21307947,
title = {NUCLEAR CONSTRAINTS ON PROPERTIES OF NEUTRON STAR CRUSTS},
author = {Jun, Xu and Liewen, Chen and Hongru, Ma and Li Baoan},
abstractNote = {The transition density {rho} {sub t} and pressure P{sub t} at the inner edge separating the liquid core from the solid crust of neutron stars are systematically studied using a modified Gogny (MDI) and 51 popular Skyrme interactions within well established dynamical and thermodynamical methods. First of all, it is shown that the widely used parabolic approximation to the full equation of state (EOS) of isospin asymmetric nuclear matter may lead to huge errors in estimating the transition density and pressure, especially for stiffer symmetry energy functionals E {sub sym}({rho}), compared to calculations using the full EOS within both the dynamical and thermodynamical methods mainly because of the energy curvatures involved. Thus, fine details of the EOS of asymmetric nuclear matter are important for locating accurately the inner edge of the neutron star crust. Second, the transition density and pressure decrease roughly linearly with increasing slope parameter L of E {sub sym}({rho}) at normal nuclear matter density using the full EOS within both the dynamical and thermodynamical methods. It is also shown that the thickness, fractional mass, and moment of inertia of the neutron star crust are all very sensitive to the parameter L through the transition density {rho} {sub t} whether one uses the full EOS or its parabolic approximation. Moreover, it is shown that E {sub sym}({rho}) constrained in the same subsaturation density range as the neutron star crust by the isospin diffusion data in heavy-ion collisions at intermediate energies limits the transition density and pressure to 0.040 fm{sup -3} {<=}{rho} {sub t} {<=} 0.065 fm{sup -3} and 0.01 MeV fm{sup -3} {<=}P{sub t} {<=} 0.26 MeV fm{sup -3}, respectively. These constrained values for the transition density and pressure are significantly lower than their fiducial values currently used in the literature. Furthermore, the mass-radius relation and several other properties closely related to the neutron star crust are studied by using the MDI interaction. It is found that the newly constrained {rho} {sub t} and P{sub t} together with the earlier estimate of {delta}I/I>0.014 for the crustal fraction of the moment of inertia of the Vela pulsar impose a more stringent constraint of R {>=} 4.7 + 4.0M/M {sub sun} km for the radius R and mass M of neutron stars compared to previous studies in the literature.},
doi = {10.1088/0004-637X/697/2/1549; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
url = {https://www.osti.gov/biblio/21307947}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 697,
place = {United States},
year = {Mon Jun 01 00:00:00 EDT 2009},
month = {Mon Jun 01 00:00:00 EDT 2009}
}