Effects of Strong Magnetic Fields on the Equation of State and Mass-Radius Structure of Hyperonic Neutron-Star Matter with Anomalous Magnetic Moments

Abstract

We investigate the effects of strong magnetic fields on the equation of state (EoS) and stellar structure of cold, charge-neutral, $β$-equilibrated hyperonic neutron-star matter within a relativistic mean-field (RMF) framework. The matter sector contains the full baryon octet and leptons, while charged particles are Landau quantized and all baryons are coupled to the magnetic field through their anomalous magnetic moments (AMM). The calculation is performed with the RMF FSU2H hyperonic parameterization and compared for zero field, constant magnetic fields, and density-dependent magnetic-field profiles. We find that strong magnetic fields modify the hyperonic composition through the competing effects of Landau quantization and AMM-induced spin splitting. Landau quantization softens the magnetized hyperonic equation of state. The inclusion of AMM provides an additional magnetic stiffening mechanism in hyperonic matter. The results for the inclusion of the AMM coupling and not are still consistent with observations of $2.00$-$2.02\,M_{\odot}$ neutron stars and small radii. The present work therefore provides a benchmark for assessing the influence of AMM on the composition, magnetization, equation of state, and mass-radius structure of magnetized hyperonic neutron-star matter.