Implications of the Conformal Constraint on Sound Speed on the Radius of PSR J0952-0607 within Rastall Gravity

TL;DR

This paper explores how the conformal sound speed constraint within Rastall gravity influences the estimated radius of the massive pulsar PSR J0952-0607, aligning theoretical models with observational data.

Contribution

It introduces a model applying the conformal sound speed bound in Rastall gravity to estimate pulsar radii, connecting modified gravity with realistic equations of state.

Findings

Estimated radius of PSR J0952-0607 is approximately 14 km.

The model's mass-radius predictions agree with astrophysical observations.

The approach links Rastall gravity with the MIT bag model for dense matter.

Abstract

It has been shown that the nonminimal coupling between geometry and matter can provide models for massive compact stars that are consistent with the conformal bound on the sound speed, $0\leqslant {c}_{s}^{2}\leqslant {c}^{2}/3$, where the core density approaches a few times the nuclear saturation density. We impose the conformal upper bound on the sound speed on Rastall's field equations of gravity, with Krori-Barua potentials in the presence of an anisotropic fluid as a matter source, to estimate the radius of the most massive pulsar ever observed, PSR J0952-0607. For its measured mass $M = 2.35\pm 0.17\, M_\odot$, we obtain a radius $R=14.087 \pm 1.0186$ km as inferred by the model. We investigate a possible connection between Rastall gravity and the MIT bag model with an equation of state, ${p}_{r}(\rho )\approx {c}_{s}^{2}\left(\rho -{\rho }_{{\rm{s}}}\right)$, in the radial direction, with ${c}_{s}=c/\sqrt{3}$ and a surface density $\rho_\text{s}$ slightly above the nuclear saturation density $\rho_\text{nuc}=2.7\times 10^{14}$ g/cm$^{3}$. The corresponding mass-radius diagram is in agreement with our estimated value of the radius and with astrophysical observations of other pulsars at 68% confidence level.