Enhancing SPOTLIGHT: A Commensal Survey for Fast Radio Transients with the uGMRT

Abstract

Radio transients are short–duration bursts of radio emission produced by a wide range of astrophysical phenomena, from pulsars and magnetars to the recently discovered class of Fast Radio Bursts (FRBs). Studying these events provides insights into extreme plasma physics, compact object environments, and the large–scale distribution of ionised matter in the Universe. However, detecting such signals is observationally challenging because they are rare, short-lived, and often occur below the sensitivity limits of existing surveys. Therefore, it is essential to improve the sensitivity, field of view, and reliability of transient search systems for advancing time–domain radio astronomy. This thesis focuses on enhancing SPOTLIGHT, a radio transient detection system operating with the Upgraded Giant Metrewave Radio Telescope (uGMRT). Several key components of the system were investigated and improved. First, the impact of radio frequency interference (RFI) on time–domain observations was studied, and a dedicated mitigation framework, called STRIPE, was developed to suppress interference while maintaining compatibility with real-time processing. Second, a multi-beam post-correlation beamforming framework with dynamic beam tiling was validated through simulations and pulsar observations. This study enabled improved sensitivity and uniform sky coverage while supporting future expansion to large beam counts. Next, a real-time simulated FRB injection framework, Arachne, was developed to enable controlled performance testing of the SPOTLIGHT transient detection pipeline. Finally, the timing consistency between beamformed data and triggered interferometric visibilities was verified using pulsar observations, which confirmed that the transient events detected in real time can be accurately localised. Together, these developments improve the robustness, reliability, and scientific capability of the SPOTLIGHT system. The results presented in this thesis advance SPOTLIGHT’s readiness for large-scale transient surveys with the uGMRT and contribute to the broader effort to discover and characterise fast radio transients, particularly FRBs, in the coming years.