arXiv subjects

Shruti Bhatporia

Publications and source records attributed to Shruti Bhatporia.

7 recordsLinked to original sources

arXiv2026

Understanding constraints on primordial mass black holes made of dark matter using fast radio bursts

In recent decades, a multitude of modified gravity theories have been proposed to address a variety of cosmological and astrophysical problems. While many of these theories remain viable, observational constraints on their parameters are increasingly stringent. Fast Radio Bursts (FRBs), in particular, have emerged as powerful probes of cosmology and fundamental physics. This study investigates the implications of a generic modified gravity theory for gravitational lensing by FRBs. By analyzing the dataset of CHIME/FRBs, we constrain the fraction of dark matter composed of primordial black holes within this theoretical framework. Furthermore, we demonstrate that modified gravity introduces a screening effect on gravitational lensing, analogous to the scattering effect of plasma on light rays.

astro-ph.CO↗

arXiv2025

Fast Radio Bursts as probes of the late-time universe: a new insight on the Hubble tension

Fast Radio Bursts (FRBs) are bright radio transient events, a subset of which have been localized to their host galaxies. Their high dispersion measures offer valuable insights into the ionized plasma along their line of sight, enabling them to serve as probes of cosmological parameters. One of the major challenges in contemporary cosmology is the Hubble tension -- an unresolved discrepancy between two independent methods of determining the Universe's expansion rate, yielding differing values for the Hubble constant. In this study, we analyze a sample of 64 extragalactic, localized FRBs observed by various telescopes, employing Bayesian analysis with distinct likelihood functions. Our findings suggest that FRBs serve as tracers of the Hubble constant in the late-time Universe. Notably, our results exhibit smaller error bars compared to previous studies, and the derived Hubble constant with 1$σ$ error bars no longer overlap with those obtained from early-Universe measurements. These results underscore the continuing tension between early- and late-time measurements of the Hubble constant.

astro-ph.CO↗

arXiv2024

Novel understanding of Cosmological Phenomena using Fast Radio Bursts

Fast radio bursts (FRBs) offer unique probes of diverse cosmological phenomena due to their characteristic properties, including short duration timescale and high dispersion measure. This study investigates two distinct theoretical frameworks: the Gertsenshtein-Zel'dovich (GZ) mechanism for ultra-high-frequency gravitational waves (GWs) and fraction of dark matter in primordial mass black holes. We explore the hypothesis that ultra-high-frequency GWs could be responsible for FRB generation. Consequently, the detection of continuous GWs signal from the vicinity of an FRB by current or future detectors would disfavour merger-based FRB formation models and lend significant credence to the GZ theory, which postulates the existence of high-frequency GWs. Moreover, we examine the effects of modified gravity on the gravitational lensing of FRBs and thereby put constraints on the fraction of primordial mass black holes made up of dark matter. Our analysis suggests that modified gravity introduces a screening effect on lensing, analogous to the scattering effect by plasma on light rays. We further discuss the expected detection rates of FRBs as well as lensed FRBs with upcoming radio telescopes, primarily HIRAX.

astro-ph.CO↗

arXiv2023

A Topological Data Analysis of the CHIME/FRB Catalogues

In this paper, we use Topological Data Analysis (TDA), a mathematical approach for studying data shape, to analyse Fast Radio Bursts (FRBs). Applying the Mapper algorithm, we visualise the topological structure of a large FRB sample. Our findings reveal three distinct FRB populations based on their inferred source properties, and show a robust structure indicating their morphology and energy. We also identify potential non-repeating FRBs that might become repeaters based on proximity in the Mapper graph. This work showcases TDA's promise in unraveling the origin and nature of FRBs.

astro-ph.HE↗

arXiv2023

Gravitational Lensing in Modified Gravity: A case study for Fast Radio Bursts

Over the last few decades, a plethora of modifications to general relativity have been proposed to solve a host of cosmological and astrophysical problems. Many modified gravity models are now ruled out with further astrophysical observations; some theories are still viable, with, at best, bounds on their parameters set by observations to date. More recently, observations of Fast Radio Bursts have proven to be remarkably powerful tools to constrain cosmology and fundamental physics. In this work, we consider a generic modified gravity theory and consider the implications for gravitational lensing with Fast Radio Bursts. We use a set of Fast Radio Burst observations to constrain the fraction of dark matter made up of primordial black holes in such a theory. We further show that modified gravity adds a screening effect on gravitational lensing similar to the case when there is plasma in the path of the light ray acting as a scattering screen.

gr-qc↗

arXiv2022

The Hydrogen Intensity and Real-time Analysis eXperiment: 256-Element Array Status and Overview

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element array to be deployed at the South African Radio Astronomy Observatory (SARAO) Square Kilometer Array (SKA) site in South Africa. Each of the 6m, $f/0.23$ dishes will be instrumented with dual-polarisation feeds operating over a frequency range of 400-800 MHz. Through intensity mapping of the 21 cm emission line of neutral hydrogen, HIRAX will provide a cosmological survey of the distribution of large-scale structure over the redshift range of $0.775 < z < 2.55$ over $\sim$15,000 square degrees of the southern sky. The statistical power of such a survey is sufficient to produce $\sim$7 percent constraints on the dark energy equation of state parameter when combined with measurements from the Planck satellite. Additionally, HIRAX will provide a highly competitive platform for radio transient and HI absorber science while enabling a multitude of cross-correlation studies. In this paper, we describe the science goals of the experiment, overview of the design and status of the sub-components of the telescope system, and describe the expected performance of the initial 256-element array as well as the planned future expansion to the final, 1024-element array.

astro-ph.IM↗

arXiv2017

Implementing and Characterizing Real-time Broadband RFI Excision for the GMRT Wideband Backend

The Giant Metrewave Radio Telescope (GMRT) is being upgraded to increase the receiver sensitivity. This makes the receiver more susceptible to man-made Radio Frequency Interference (RFI). To improve the receiver performance in presence of RFI, real-time RFI excision (filtering) is incorporated in the GMRT wideband backend (GWB). The RFI filtering system is implemented on FPGA and CPU-GPU platforms to detect and remove broadband and narrowband RFI. The RFI is detected using a threshold-based technique where the threshold is computed using Median Absolute Deviation (MAD) estimator. The filtering is carried out by replacing the RFI samples by either noise samples or constant value or threshold. This paper describes the status of the real-time broadband RFI excision system in the wideband receiver chain of the upgraded GMRT (uGMRT). The test methodology for carrying out various tests to demonstrate the performance of broadband RFI excision at the system level and on radio astronomical imaging experiments are also described.

astro-ph.IM↗