[Prex] Neutron skins and neutron stars in the multi-messenger era

[Jay Benesch]

https://arxiv.org/abs/1711.06615

Neutron skins and neutron stars in the multi-messenger era
F. J. Fattoyev, J. Piekarewicz, C. J. Horowitz
(Submitted on 17 Nov 2017)

     The historical first detection of a binary neutron star merger by 
the LIGO-Virgo collaboration [B. P. Abbott {\sl et al.} Phys. Rev. Lett. 
119, 161101 (2017)] is providing fundamental new insights into the 
astrophysical site for the r-process and on the nature of dense matter. 
A set of realistic models of the equation of state (EOS) that yield an 
accurate description of the properties of finite nuclei, support neutron 
stars of two solar masses, and provide a Lorentz covariant extrapolation 
to dense nuclear matter are used to confront its predictions against 
tidal polarizabilities extracted from the gravitational-wave data. Given 
the sensitivity of the gravitational-wave signal to the underlying EOS, 
limits on the tidal polarizabilities inferred from the observation 
translate into stringent constraints on the neutron-star radius. Based 
on these constraints, models that predict a stiff symmetry energy, and 
thus large stellar radii, can be ruled out. Indeed, under a particular 
binary-mass scenario, we deduce an upper limit on the radius of a 1.6M⊙ 
neutron star of R1.6⋆<13.25km. Given the sensitivity of the neutron-skin 
thickness of 208Pb to the symmetry energy, albeit at a lower density, we 
infer a corresponding upper limit of R208skin≲0.25fm. However, if the 
upcoming PREX-II experiment measures a significantly thicker skin, this 
may be evidence of a softening of the symmetry energy at high 
densities---likely indicative of a phase transition in the interior of 
neutron stars.

Comments: 	6 pages, 4 figures