arXiv subjects

Charul Rathod

Publications and source records attributed to Charul Rathod.

3 recordsLinked to original sources

arXiv2026

Testing selectively enhanced QCD axions couplings as an explanation of the RX J1856.5-3754 hard X-ray excess

We explore the possibility of explaining hard X-ray data obtained from one of the Magnificent Seven (M7) neutron-stars (NSs) employing QCD axion-converted photons. The emission of thermal axions along with neutrinos from the core has been considered. We adopt the nucleon-nucleon bremsstrahlung process as the baseline axion production mechanism and Cooper-pair breaking and formation (PBF) as an additional process. We investigate here whether the selectively enhanced QCD axion coupling model can better explain the hard X-ray excess than the commonly used KSVZ axion model. Our results suggest that meV-mass QCD axions cannot explain the hard X-ray observation within the adopted framework. The enhanced selective model in the micro-eV scale provides closer agreement with the hard X-ray data. We thus conclude that the emission of hard X-rays in the $2-8$ keV range from isolated M7 stars could be explained by QCD axions under an enhanced coupling scenario.

hep-ph↗

arXiv2025

Structural Properties of Magnetized Neutron Stars under f (R, T ) Gravity Framework

The current work investigates the structural properties of neutron stars in the presence of a strong magnetic field within the framework of f(R,T) modified gravity, where the matter-geometry coupling leads to deviations from general relativity at high matter densities. We present here the mass-radius sequences, as well as the mass and pressure distributions for various values of the modified gravity parameter and the central magnetic field. The modified Tolman-Oppenheimer- Volkoff equations are numerically solved using isotropic equations of state, specifically the APR, FPS, and SLy models. Comparing the corresponding results in the context of general relativity suggests that more negative values of the modified gravity parameter result in higher maximum gravitational masses. In contrast, strong central magnetic fields of up to 1018 Gauss cause only a slight decrease in maximum mass without disrupting spherical symmetry. Our findings are in agreement with the observed data from GW170817, PSR and NICER.

gr-qc↗

arXiv2024

Thermal Evolution of Magnetars under f(R, T) Gravity

The present study explores the thermal evolution and emission properties of neutron stars within the framework of modified $f(R, T)$ gravity by solving the coupled energy-balance and heat-transport equations. We compute stellar mass and pressure profiles by solving the Tolman-Oppenheimer-Volkoff equations in both Einstein gravity and modified gravity, employing the APR, FPS, and SLy equations of state, with and without the strong magnetic field. Using these profiles, we assess the red-shifted surface temperature, $T_s^{\infty}$, as well as the photon and neutrino luminosities for each equation of state. We further examine the effects of the magnetic field, the choice of equation of state, and the underlying gravity theory framework on the cooling of neutron stars, particularly those of magnetized neutron stars or magnetars. Our results indicate that $f(R, T)$ gravity, particularly for the APR and SLy equations of state, exhibits improved agreement with the observed $T_s^{\infty}$ and photon luminosities than standard general relativity, regardless of magnetic-field strength. Moreover, it predicts the neutrino luminosities under both gravity models, all the chosen equations of state, and magnetic field configurations.

gr-qc↗