Nuclear and hybrid equations of state in light of the low-mass compact star in HESS J1731-347
L. Brodie, Alexander Haber
Abstract
We sample over 500 relativistic mean-field theories constrained by chiral effective-field theory and properties of isospin-symmetric nuclear matter and test them against known stellar structure constraints. This includes a recent mass and radius measurement of a compact object in supernova remnant HESS J1731-347, with an unusually low mass of $M=0.{77}_{\ensuremath{-}0.17}^{+0.20}{M}_{\ensuremath{\bigodot}}$ and a compact radius of $R=10.{4}_{\ensuremath{-}0.78}^{+0.86}$ km. We show that none of the sampled nuclear models meet all constraints at the $68%$ credibility level, but that hybrid equations of state with a quark-matter inner core and nuclear outer core easily can. This indicates a tension between astrophysical constraints and low-energy nuclear theory.