Multifrequency Study of FRB 20201124A with the uGMRT

We present results from a monitoring campaign of FRB 20201124A using the uGMRT during its active phase between MJD 59342 and 59362. Simultaneous observations in Band 4 (550–950 MHz) and Band 5 (1060–1460 MHz) provide a uniform view of the source activity. The burst activity exhibits a frequency-dependent evolution, with the last Band-5 burst detected on MJD 59358, while Band-4 activity persisted until MJD 59362. We identified burst pairs in the simultaneously observed Band-4 and Band-5 data, with time separations of 31.8 and 52.3 ms. These separations are comparable to the short-timescale component of the waiting-time distribution, which peaks at ∼60 ms, suggesting that the multiband burst pairs may be associated with the same short-timescale clustering process. Contemporaneous FAST observations detected the Band-5 bursts but revealed no strictly simultaneous counterparts to the corresponding Band-4 bursts. These results suggest frequency-dependent burst occurrence and are consistent with patchy spectral occupancy over the 550–1460 MHz frequency range. The detected bursts exhibit diverse temporal and spectral morphologies. Consecutive bursts were observed with separations of 16.7(2)–291.5(6) ms, revealing short repetition intervals and possible subsecond quasi-periodicity. The waiting-time and energy distributions are bimodal, indicating at least two characteristic emission timescales and energy modes. Burst fluences span 1.7(3)–78(3) Jy ms, and the cumulative fluence distribution is well described by a broken power law. These results provide a simultaneous multifrequency view of FRB 20201124A during its 2021 May active episode and support a picture in which the source exhibits complex frequency-dependent activity and broadband emission behavior.