Astrophysics equation of state inference with Bayesian chiral effective field theory uncertainties

TL;DR

This paper applies Bayesian chiral effective field theory uncertainties and astrophysical data to infer the neutron star equation of state, constraining the symmetry energy slope parameter with minimal impact from pQCD constraints.

Contribution

It introduces a Bayesian framework incorporating chiral EFT uncertainties and astrophysical constraints to refine neutron star EOS and symmetry energy parameters.

Findings

EOS stiffens at densities above 3 times nuclear saturation density

pQCD constraints have negligible impact on the EOS posteriors

Inferred symmetry energy slope parameter L is between 42.6 and 56.7 MeV

Abstract

We investigate Bayesian chiral effective field theory ($\chi$EFT) uncertainties, which assign a statistical interpretation to equation of state (EOS) distributions near nuclear saturation density, n$_0$, as well as constraints from perturbative quantum chromodynamics (pQCD) to Bayesian EOS inference from LIGO/Virgo, NICER and pulsar mass observations. The tails of the $\chi$EFT uncertainties allow for broader pressure ranges in our priors, but large parts of these are excluded by the astrophysical observations, so that the EOS and the resulting mass-radius posteriors are still very consistent with our earlier work. Within our broad prior ranges, we observe a clear stiffening of the EOS at $n \gtrsim 3 n_0$. Moreover, the impact of the pQCD constraints on the posterior EOS and mass-radius range is negligible due to the astrophysics constraints. Exploiting the strong correlation between pure neutron matter and matter in beta equilibrium, we infer the symmetry energy slope parameter $L$ from astrophysics. For the $68\%$ credible interval, we obtain $L=42.6-52$ MeV and $L=44.2-56.7$ MeV using piecewise-polytrope and speed-of-sound high-density extensions, respectively. The $L$ posterior is mainly driven by the combination of GW170817 LIGO/Virgo and PSR J0740+6620, PSR J0437-4715, and PSR J0614-3329 NICER observations.