Multi-Frequency Study of FRB20201124A with the uGMRT

TL;DR

This study presents multi-epoch, multi-frequency observations of the repeating FRB 20201124A, revealing complex burst morphologies, frequency-dependent activity, and potential sub-second periodicity, advancing understanding of FRB emission mechanisms.

Contribution

It provides the first detailed multi-frequency analysis of FRB 20201124A during its active phase, uncovering diverse burst properties and emission behaviors not previously documented.

Findings

Bursts show significant morphological diversity and frequency-dependent activity.

Detection of short intervals and potential sub-second quasi-periodicity.

Burst energy and waiting-time distributions are bimodal, indicating multiple emission modes.

Abstract

We present results from multi-epoch observations of the repeating fast radio burst FRB 20201124A with the upgraded Giant Metrewave Radio Telescope (uGMRT) during its active phase between 8 May and 28 May 2021. The bursts exhibit significant morphological diversity, including multiple sub-bursts, downward frequency drifts, and intrinsic widths ranging from 1.032 - 32.159 ms. Bursts were detected in both Band 4 (550 - 950 MHz) and Band 5 (1060 - 1460 MHz), with the last Band 5 burst occurring on 24 May, while Band 4 activity persisted until 28 May, indicating a frequency-dependent decline. Consecutive bursts were observed with separations of 16.7 - 291.5 ms, revealing short repetition intervals or potential sub-second quasi-periodicity. The waiting-time and energy distributions are bimodal, suggesting at least two distinct emission timescales and energy modes. Burst fluence ranges from 1.72 - 78.47 Jy ms, and the cumulative fluence distribution follows a broken power law. Multi-frequency analysis further shows closely spaced burst pairs across Band 4 and Band 5, with sub-second offsets of 1.08 - 1.15 s, and no strict simultaneity with contemporaneous FAST detections. These findings demonstrate that FRB 20201124A exhibits closely spaced, patchy, multi-frequency emission with frequency-dependent activity, highlighting the complex and dynamic nature of repeating FRBs.