| Abstract : | Fast Radio Bursts (FRBs), a class of short-duration highly energetic dispersed extragalactic radio signals, have been detected at different radio telescopes. Even though the bursts are mostly one-offs, repeating bursts have been observed from the source of more than 20 FRBs till now. The identification of the repeating nature of an FRB may strongly depend on the instrumental sensitivity.
The uGMRT being significantly sensitive compared to the major FRB discovering telescope (e.g. CHIME and ASKAP), it can probe the inferred scaling of repetition rate with fluence in a possibly unexplored regime. In addition, an instantaneous wide frequency coverage of the uGMRT (250-1460 MHz), provides an unprecedented view of burst spectral and polarisation properties to differentiate between various progenitor models. Using uGMRT we investigate the inherent properties, such as wide-band spectral structure, variation of burst rate with time and frequency, duration of the active-window and scintillation time-scale at different frequencies, temporal-variation of dispersion measure and rotation measure, of some of the repeating FRBs, which in turn will be extremely useful to constrain the origin of the radio emission.
Initially, we have focused on two repeaters FRB121102 and FRB180916 detected at Arecibo and CHIME with a periodicity of 157 days and 16 days respectively. In this presentation, we report results from 60 hours of observations over 550-1460 MHz for FRB121102 and 126 hours of observations over 250-1460 MHz for FRB180916. Using the bursts detected from these observations, we highlight the prospect of wide frequency coverage of uGMRT allowing us to probe the scaling of emission bandwidth of the bursts and its consistency with propagation through turbulent plasma as well as whether the spectral structure could be due to plasma lensing. In addition to limited emission bandwidth, the frequency evolution of downward drifting of sub-pulses is also being explored. |
