Talks

The mechanism of emission of bright radio flashes from Fast Radio Bursts (FRBs) remains an open question to date. From observations, FRBs are of two types - repeaters and one-off events. Some repeaters have been localised to their host galaxy, thereby shedding some light on the possible progenitors. Of these repeaters, FRB121102, FRB190520B and FRB20240114A stand out as the only events for which persistent radio emission associated with the FRBs has been seen. In this talk, I will describe our follow-up observations of the persistent radio source associated with FRB190520B using both the upgraded Giant Metrewave Radio Telescope and the Jansky Very Large Array and present the results in the context of various models that predict the emission and evolution of the persistent source associated with an FRB.

While most FRBs have been one-off events, a minor fraction (7%) repeats; these are known as repeaters. An even smaller fraction is known as hyperactive repeaters, due to the large number of bursts emitted by them over a short amount of time. Currently, only 5 hyperactive repeaters are known: 20121102A, 20190520B, 20201124A, 20220912A, and 20240114A. In this presentation, we will present the study of 167 bursts detected from FRB 20240114A using the GMRT, over a frequency range of 300 to 750 MHz, and on 4 different dates over a period of 6 months, amounting to more than 18 hours of on-source time. In this presentation, we will talk about our analysis, done using scarab (https://github.com/astrogewgaw/scarab), a new package we developed for the same. The detected bursts showed rich spectro-temporal structure, such as band limitation, drifting sub-bursts, and multiple emission components. The properties of the burst showed a wide variation, with widths varying from ~0.2 to ~40 ms, scattering timescales varying from ~0 to ~30 ms, and DMs varying from ~524 pc cm-3 to ~533 pc cm-3. We see non-Poissonian waiting time distributions for the detected bursts, which indicate that the emission process is not inherently random, and may have some long term memory, as has been previously indicated for other FRBs (e.g.: Wang et al. 2024). We also compare the properties and statistics of the detected bursts from FRB 20240114A to other hyperactive repeaters, which allows us to posit that similar emission mechanisms might be responsible for these events.

Giant pulses (GPs) are rare, and extremely energetic bursts of radio emission that can exceed the average pulse energy by factors of 100 or more ( Ershov & Kuzmin 2005). These are intrinsically short timescale phenomena, with individual subpulses having durations as brief as 2 ns (Hankins et al. 2003). Such “nanopulses” exhibit brightness temperatures as high as 1037 K. First revealed in the Crab pulsar (Staelin & Reifenstein 1968), GPs have since been identified in both young and millisecond pulsars (MSPs), typically localized to narrow phase windows and coinciding with high-energy X-ray emission, highlighting their likely origin in regions of strong magnetic field near the light cylinder. However, Giant pulses have been studied in detail in only a handful of MSPs (e.g. PSRs B1937+21 (Cognard et al. 1995), B1821−24 (Romani et al. 2001), and J1823−3021A (Knight et al. 2005))-in part because of the fast pulsar period, large dispersive smearing timescale, and relatively weak signal conspires to make single-pulse observations difficult. Interestingly, GPs have also been observed in slow pulsars lacking strong magnetic fields at the light cylinder, such as PSRs J1752+2359, B1112+50, and B0031−07, suggesting multiple physical channels for GP production. These bursts are often phase-stable and can form short temporal clusters, providing clues about magnetospheric processes and emission geometry. The SPOTLIGHT program—a real-time, commensal survey for pulsars and Fast Radio Bursts (FRBs) using the GMRT—has identified 10s of bright single pulses already within a week of deployment, motivating a systematic statistical study of pulse energy, phase localization, and morphology across both MSPs and normal pulsars. Such efforts allow us to examine correlations with intrinsic pulsar properties like magnetic field strength and spin-down luminosity. We aim to conduct a systematic statistical analysis of bright single pulses across a broader sample of normal pulsars as well as MSPs, focusing on energy distributions, pulse-phase localization, morphology, and variability. This will allow us to characterize the emission physics of these pulses and explore correlations with intrinsic pulsar properties such as spin-down luminosity and magnetic field strength. Notably, a moderate anti-correlation between profile stability and magnetic field strength in MSPs hints that stronger magnetic fields may destabilize pulse shapes, potentially enhancing the occurrence of bright pulses (Ghosh et al. 2025, in preparation). These investigations are especially relevant in the context of recent observations of plasma lensing in systems like PSR B1957+20 (Main et al. 2018), where narrowband amplification and temporal clustering of pulses have drawn parallels with the properties of repeating Fast Radio Bursts (FRBs), such as FRB 121102 (Main et al. 2018). Given the similar spectral and temporal behaviors, studying bright pulses from MSPs may offer a valuable window into the emission mechanisms of FRBs and their propagation through dense, dynamic magneto-ionic environments. Through this effort, we aim to bridge the phenomenology of giant pulses in pulsars with that of coherent bursts from other neutron star populations, including magnetars and FRBs