Pratul Manna | Searcharxiv

arXiv2026

Structural quasi-universality in highly magnetized differentially rotating neutron stars

Universal relations among macroscopic properties of neutron stars provide a powerful framework to probe their internal structures while minimizing uncertainties associated with the equation of state (EoS). Although such relations have been extensively studied for uniformly rotating stars, their extension to differentially rotating and strongly magnetized configurations remains largely unexplored. We systematically investigate equilibrium configurations for a wide range of EoSs, rotation profiles, and magnetic field strengths. We establish a generalized quasi-universal relation between the moment of inertia and compactness that remains remarkably insensitive to the underlying EoS across uniformly rotating, differentially rotating, and strongly magnetized configurations. For sequences with fixed angular momentum, the normalized moment of inertia exhibits a quasi-universal dependence on compactness, with deviations primarily due to magnetic field strength and degree of differential rotation. We derive analytic expressions for these dependencies, enabling a unified phenomenological model applicable over a wide range of stellar configurations. As astrophysical applications, we quantify the systematic bias in magnetar luminosity estimates and the rotational kinetic energy of post-merger remnant of GW170817. These results extend quasi-universal relations beyond the standard assumptions of uniform rotation and weak magnetization, providing a robust framework for interpreting observations of highly magnetized and differentially rotating neutron stars, and enabling more reliable constraints on their astrophysical properties.

astro-ph.HE↗

arXiv2025

Improved inspiral-merger-ringdown model for BBHs on elliptical orbits

Gravitational waveforms capturing binary evolution through the early-inspiral phase play a critical role in extracting orbital features that nearly disappear during the late-inspiral and subsequent merger phase due to radiation reaction forces; for instance, the effect of orbital eccentricity. Phenomenological approaches that model compact binary mergers rely heavily on combining inputs from both analytical and numerical approaches to reduce the computational cost of generating templates for data analysis purposes. In a recent work, Chattaraj et al., Phys. Rev. D 106, 124008 (2022) constructed a dominant ($\ell=2$, $|m|=2$) mode model for nonspinning binary black holes (BBHs) on elliptical orbits. The model was constructed in time domain and is fully analytical. The current work is an attempt to improve this model by making a few important changes in our approach. The most significant of those involves identifying initial values of orbital parameters with which the inspiral part of the model is evolved. While the ingredients remain the same as in the previous work, the resulting (new) model, when compared against a set of target waveforms constructed here, produces match values better than 96.5% for systems heavier than $80M_\odot$, while with the old model this limit on the total mass is $115M_\odot$. The updated model is validated against an independent eccentric waveform family (TEOBResumS-Dali) for an initial eccentricity ($e_0$), mass ratio ($q$) and mean anomaly ($l_0$) in the range $0\lesssim e_0\lesssim0.3$, $1\lesssim q\lesssim3$ and $-π\leq l_0\leqπ$, respectively. Further, an alternate model including the effect of higher order modes is also provided. Finally, while our model assumes nonspinning components, we show that it could also be used for systems with component spin vectors (anti-) aligned w.r.t. the orbital angular momentum and small spin magnitudes.

gr-qc↗