Stellar modeling within regularized 4D Einstein-Gauss-Bonnet gravity in light of current astrophysical constraints

TL;DR

This paper explores how regularized 4D Einstein-Gauss-Bonnet gravity affects the structure of compact stars, comparing predictions with observational data to assess its viability as an extension of General Relativity.

Contribution

It provides the first detailed interior solutions for isotropic compact stars in 4DEGB gravity using realistic equations of state and compares results with astrophysical observations.

Findings

Stars are less compact in 4DEGB gravity compared to GR.

Maximum stellar masses are moderately higher in 4DEGB.

Models are consistent with multi-messenger astrophysical constraints.

Abstract

In this study we obtain interior solutions and investigate structural properties of isotropic compact stars in the framework of four-dimensional regularized Einstein-Gauss-Bonnet (4DEGB) gravity. For stellar matter content, we adopt a widely used quark-matter model that approximates a realistic equation of state (EoS). By numerically integrating the modified Tolman-Oppenheimer-Volkoff equations, we obtain interior solutions for static, spherically symmetric fluid spheres. The resulting sequences are compared directly with the predictions of General Relativity (GR). Our analysis focuses on three diagnostic indicators: (i) the mass-radius profiles under GR and three representative choices of the Gauss-Bonnet coupling; (ii) the stellar compactness factor, $C \equiv M/R$; and (iii) the relation between stellar mass and central energy density. Recent observational studies suggest that the maximum masses inferred from the mass-radius relation may be larger than previously expected. To address this, we include a comparative set of constraints from multi-messenger astrophysical observations, including gravitational-wave event GW190814, as well as X-ray measurements from NICER for PSR~J0740+6620 and PSR~J0030+0451. These data provide stringent, astrophysically grounded tests of the viability of the models discussed here. Our results indicate that compact stars within 4DEGB gravity are systematically less compact and achieve moderately higher maximum masses compared to the GR case. This trend is consistent with recent theoretical analyses of compact stars in higher-curvature gravity theories and with constraints from multi-messenger astrophysics. Together, these findings suggest that regularized Gauss-Bonnet corrections constitute a plausible extension of GR in the strong-field regime.