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

Applying an equation of state (EOS) with its symmetric nuclear matter contribution and low-density symmetry energy Esym( ) constrained by heavy-ion reaction data, we calculate the dimensionless tidal deformability Λ 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, Λ is found to be in the range of 292 ≤ Λ 1.4 ≤ 680, consistent with the very recent observation of the GW170817 event. We investigate the effect of the high-density behavior of Esym( ) on the tidal properties of neutron stars and find that while Λ depends strongly on the details of the symmetry energy, different trends of Esym( ) lead to very similar values of Λ. In particular, the transition from stiff/soft-to-soft/stiff Esym( ) could yield the same Λ. Thus, measuring Λ 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 Esym( ).