Imprints of the nuclear symmetry energy on the tidal deformability of neutron stars

摘要

Applying an equation of state (EOS) with its symmetric nuclear matter contribution and low-density symmetry energy E-sym(rho) constrained by heavy-ion reaction data, we calculate the dimensionless tidal deformability Lambda of neutron stars in coalescing binary systems. Corresponding to the partially constrained EOS that previously predicted a radius of 11.5 km <= R-1.4 <= 13.6 km for canonical neutron-star configurations, Lambda is found to be in the range of 292 <= Lambda(1.4) <= 680, consistent with the very recent observation of the GW170817 event. We investigate the effect of the high-density behavior of E-sym(rho) on the tidal properties of neutron stars and find that while Lambda depends strongly on the details of the symmetry energy, different trends of E-sym(rho) lead to very similar values of Lambda. In particular, the transition from stiff/soft-to-soft/stiff E-sym(rho) could yield the same Lambda. Thus, measuring Lambda alone may not determine completely the density dependence of the symmetry energy. Coherent analyses of the dense neutron-rich nuclear matter EOS underlying both nuclear laboratory experiments and astrophysical observations are therefore necessary to break this degeneracy and determine precisely the details of the E-sym(rho).