Hybrid stars and the stiffness of the nuclear equation of state in light of the HESS J1731-347 remnant

¹ Department of Theoretical Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
² Department of Physics, Faculty of Science, University of Zagreb, Bijenicˇka cesta 32, 10000 Zagreb, Croatia

^* e-mail: plaskos@physics.auth.gr
^** e-mail: koliogi@physics.auth.gr
^*** e-mail: moustaki@auth.gr

Published online: 8 October 2024

Abstract

The recent observation of the extremely compact neutron star in the HESS J1731-347 remnant has challenged our understanding concerning the nature of dense nuclear matter. In particular, the low radius of the aforementioned compact object favors soft nuclear equations of state. However, the neutron skin thickness of ²⁰⁸Pb extracted from the long-awaited PREX-II experiment favors stiff equations of state which may be associated with larger radii for low mass stellar configurations. In this contribution we present our recent work on the possible reconciliation of the HESS J1731-347 observation in the framework of hybrid stars, under the assumption of a stiff low-density phase which may be favored by the PREX-II results. In addition, we examine the compatibility of the resulting hybrid models with recent constraints based on the observation of PSR J0030+0451, PSR J0952-0607 and GW190814.