We investigate compact stellar configurations in the framework of Formula: see text gravity, where Formula: see text, Formula: see text, and Formula: see text denote the Ricci scalar, Gauss–Bonnet invariant term, and trace of the energy–momentum tensor, respectively. Adopting a linear functional form Formula: see text, we explore the combined influence of higher-order curvature corrections (Formula: see text) and matter–geometry coupling (Formula: see text). Assuming a static, spherically symmetric spacetime with anisotropic matter distribution, we obtain exact and regular solutions to the modified field equations using the Krori–Barua metric ansatz. Model parameters are constrained with observational inputs from the LMXB neutron star 4U 1608-52, characterized by mass Formula: see text and radius Formula: see text. We analyze three representative cases: negative Formula: see text, null Formula: see text corresponding to General Relativity, and positive Formula: see text values of Formula: see text. The resulting solutions satisfy all standard physical requirements, including causality condition, energy conditions and stability criteria. An effective equation of state is constructed via a curve-fitting procedure by optimizing the central sound speed. Employing the Buchdahl compactness limit and a central density Formula: see text, we estimate the maximum mass and radius. Notably, the model predicts a maximum mass up to Formula: see text for Formula: see text, and may be utilized to study the properties of primary mass Formula: see text detected in the gravitational wave event GW230529₁81500. By varying the central density, the model reproduces radii consistent with many observed pulsars and recent gravitational wave events. These results demonstrate that the proposed framework provides stable configurations and offers a consistent extension of General Relativity for probing the internal structure of compact stars.
Bhattacharjee et al. (Tue,) studied this question.