arXiv subjects

Uddeepta Deka

Publications and source records attributed to Uddeepta Deka.

4 recordsLinked to original sources

arXiv2025

Probing the spin of compact objects with gravitational microlensing of gravitational waves

Propagating gravitational waves (GWs) can encounter a massive object (lens) whose gravitational radius is comparable to the wavelength of the GWs (wave-optics regime). The resulting `microlensed' signal contains imprints about the properties of the lens. In this work, we compute the GW waveforms microlensed by a rotating compact object in weak-field gravity. Using these waveforms, for the first time, we assess how well the parameters of the rotating lens can be inferred from GW lensing observations. We find that if we allow for naked singular solutions within general relativity or beyond, which in principle can have spins that are not bounded to be extremal, our method can be used to extract the rotating lens parameters using observations of microlensed GWs with future detectors. As a result, we find that the lens parameters for such lenses are well recovered within $90\%$ confidence for signal-to-noise ratio (SNR) 50 and especially well for SNR$=100$ with Einstein Telescope.

gr-qc↗

arXiv2025

Surrogate modeling of gravitational waves microlensed by spherically symmetric potentials

The anticipated observation of the gravitational microlensing of gravitational waves (GWs) promises to shed light on a host of astrophysical and cosmological questions. However, extracting the parameters of the lens from the modulated GWs requires accurate modeling of the lensing amplification factor, accounting for wave-optics effects. Analytic solutions to the lens equation have not been found to date, except for a handful of simplistic lens models. While numerical solutions to this equation have been developed, the time and computational resources required to evaluate the amplification factor numerically make large-scale parameter estimation of the lens (and source) parameters prohibitive. On the other hand, surrogate modeling of GWs has proven to be a powerful tool to accurately, and rapidly, produce GW templates at arbitrary points in parameter space, interpolating from a finite set of available waveforms at discrete parameter values. In this work, we demonstrate that surrogate modeling can also effectively be applied to the evaluation of the time-domain microlensing amplification factor $\widetilde{F}(t)$. We show this by constructing $\widetilde{F}(t)$ for two lens models, viz. point-mass lens, and singular isothermal sphere, which notably includes logarithmic divergence behaviour. We find both surrogates reproduce the original lens models accurately, with mismatches $\lesssim 5 \times 10^{-4}$ across a range of plausible microlensed binary black hole sources observed by the Einstein Telescope. This surrogate is between 5 and $10^3$ times faster than the underlying lensing models, and can be evaluated in about 100 ms. The accuracy and efficiency attained by our surrogate models will enable practical parameter estimation analyses of microlensed GWs.

gr-qc↗

arXiv2024

Probing charge of compact objects with gravitational microlensing of gravitational waves

Gravitational microlensing of gravitational waves (GWs) opens up the exciting possibility of studying the spacetime geometry around the lens. In this work, we investigate the prospects of constraining the `charged' hair of a charged gravitating object from the observation of a GW signal microlensed by the same. The charge can have electromagnetic or modified gravity origin. We compute the analytic form of the lensing potential with charge and construct the lensed waveforms for a range of mass and charge of the charged object, assuming them to be non spinning. Using an approximate likelihood function, we explore how future observations of microlensed GWs can constrain the charge of the lens. We conclude that lensing observations are unlikely to be able to constrain the electromagnetic charge of black holes. However, we might be able to put modest constraints on certain modified gravity models (e.g., the brandworld scenario) or the possibility of the lenses being exotic objects (e.g., naked singularities) .

gr-qc↗

arXiv2019

Radio Pulsar Sub-Populations (I) : The Curious Case of Nulling Pulsars

About 200 radio pulsars have been observed to exhibit nulling episodes - short and long. We find that the nulling fraction of a pulsar does not have any obvious correlation with any of the intrinsic pulsar parameters. It also appears that the phenomenon of nulling may be preferentially experienced by pulsars with emission coming predominantly from the polar cap region, and also having extremely curved magnetic fields.

astro-ph.HE↗