Anisotropic compact stars in Rastall–Rainbow gravity

Abstract

Abstract In this work, we investigate anisotropic effects on the equations of state (EoS) used to describe neutron and quark stars in the framework of Rastall–Rainbow gravity. All our calculations are computed using two different EoS to describe the matter contained within the star: the MIT bag model for quark stars and the IU-FSU parameterisation for the standard hadronic matter. From the values of masses and radii obtained, we can conclude that anisotropic pressure has significant consequences on the structure of compact objects. Specifically, when anisotropy is considered within general relativity, it significantly modifies the maximum stellar mass. On the other hand, when Rastall–Rainbow gravity and anisotropy are simultaneously considered, they provide the best results for the masses and radii of some important astrophysical objects such as the low-mass x-ray binary (LMXB) NGC 6397 and the extremely massive millisecond pulsating source of radio (PSR) J0740 + 6620, for instance. Radii results inferred from the Lead Radius EXperiment (PREX-2) and the compact object in the mass-gap of GW190814 event can also be described for certain values of the Rastall–Rainbow and anisotropy parameters.