Wave Propagation in 1-D Spiral geometry

In this article, we investigate the wave equation in spiral geometry and study the modes of vibrations of a one-dimensional (1-D) string in spiral shape. Here we show that the problem of wave propagation along a spiral can be reduced to Bessel differential equation and hence, very closely related to the problem of radial waves of two-dimensional (2-D) vibrating membrane in circular geometry

Harbingers of Exotic Transients: The Electromagnetic Follow-up of Gravitational-wave Transients & Transient Rates

Gravitational waves (GWs) provide a unique view of the universe. They directly probe the extreme gravity and extreme matter of compact objects like black holes (BHs) and neutron stars (NSs) which is not always possible from traditional electromagnetic (EM) wave astronomy. The cataclysmic coalescence of compact object binaries is one of the loudest individual sources of GWs that can be detected by the Laser Interferometer Gravitational wave Observatory (LIGO) and the Virgo Observatory. If one of the component is a NS, there is a possibility that the merger is bright in the EM spectrum. The relativistic astrophysics could launch a short gamma-ray burst, the radioactivity in the neutron rich ejecta could power a rapidly decaying optical transient called a kilonova. Hence, it is possible to jointly observe the same source via multiple messengers. It is this prospect of multi-messenger astronomy using GWs that is of great interest due to the rich science that can be extracted from such joint observations. In this thesis, I present the details of my work with the LIGO Scientific Collaboration and Virgo Collaboration in the context of multi-messenger astronomy. I also report my work on the time-domain astronomy front in the development of an observing strategy for the Zwicky Transient Facility (ZTF), and characterizing the detection efficiency of the intermediate Palomar Transient Factory (iPTF)

A Bibliography on Marichjhapi Massacre in West Bengal

The Marchjhapi incidents have significant influence in the socio-political environment of West Bengal. The paper deals with the bibliographic approach of the Marichjhapi Massacre in West Bengal. The paper attempt has been made to compile a bibliography on Marichjhapi massacre and Google Scholar was used as the basic tool to retrieve the data significant. Findings of the study indicated that the literature got significant increase from 2001 onwards. The paper is expected to be helpful for the researchers to get access to the relevant documents of the field

A Machine Learning Based Source Property Inference for Compact Binary Mergers

The detection of the binary neutron star (BNS) merger, GW170817, was the first success story of multi-messenger observations of compact binary mergers. The inferred merger rate along with the increased sensitivity of the ground-based gravitational-wave (GW) network in the present LIGO/Virgo, and future LIGO/Virgo/KAGRA observing runs, strongly hints at detection of binaries which could potentially have an electromagnetic (EM) counterpart. A rapid assessment of properties that could lead to a counterpart is essential to aid time-sensitive follow-up operations, especially robotic telescopes. At minimum, the possibility of counterparts require a neutron star (NS). Also, the tidal disruption physics is important to determine the remnant matter post merger, the dynamics of which could result in the counterparts. The main challenge, however, is that the binary system parameters such as masses and spins estimated from the real time, GW template-based searches are often dominated by statistical and systematic errors. Here, we present an approach that uses supervised machine-learning to mitigate such selection effects to report possibility of counterparts based on presence of a NS component, and presence of remnant matter post merger in real time.Comment: accepted in Ap

Predictions for Electromagnetic Counterparts to Neutron Star Mergers Discovered during LIGO-Virgo-KAGRA Observing Runs 4 and 5

We present a comprehensive, configurable open-source framework for estimating the rate of electromagnetic detection of kilonovae (KNe) associated with gravitational wave detections of binary neutron star (BNS) mergers. We simulate the current LIGO-Virgo-KAGRA (LVK) observing run (O4) using up-to-date sensitivity and up-time values as well as the next observing run (O5) using predicted sensitivities. We find the number of discoverable kilonovae during LVK O4 to be ${ 1}_{- 1}^{+ 4}$ or ${ 2 }_{- 2 }^{+ 3 }$, (at 90% confidence) depending on the distribution of NS masses in coalescing binaries, with the number increasing by an order of magnitude during O5 to ${ 19 }_{- 11 }^{+ 24 }$. Regardless of mass model, we predict at most five detectable KNe (at 95% confidence) in O4. We also produce optical and near-infrared light curves that correspond to the physical properties of each merging system. We have collated important information for allocating observing resources and directing search and follow-up observations including distributions of peak magnitudes in several broad bands and timescales for which specific facilities can detect each KN. The framework is easily adaptable, and new simulations can quickly be produced as input information such as merger rates and NS mass distributions are refined. Finally, we compare our suite of simulations to the thus-far completed portion of O4 (as of October 14, 2023), finding a median number of discoverable KNe of 0 and a 95-percentile upper limit of 2, consistent with no detection so far in O4.Comment: 16 pages, 13 figures, MNRAS: Accepted 2023 November 25. Received 2023 November 16; in original form 2023 October 2