Detection of a bright burst from the repeating FRB 20201124A at 2 GHz

TL;DR

This paper reports the first detection of a bright, high-frequency burst from the repeating FRB 20201124A using a Japanese radio telescope, revealing insights into its luminosity function and the nature of repeating versus one-off FRBs.

Contribution

It presents the first observation of FRB 20201124A at 2 GHz, analyzes its spectral properties, and discusses implications for the luminosity distribution and classification of FRBs.

Findings

Detected a bright burst at 2 GHz with fluence > 189 Jy ms.

Suggested the luminosity function may be broken at lower fluences.

Indicated that repeating FRBs can be as bright as one-off FRBs.

Abstract

We present a detection of a bright burst from FRB 20201124A, which is one of the most active repeating FRBs, based on S-band observations with the 64-m radio telescope at the Usuda Deep Space Center/JAXA. This is the first FRB observed by using a Japanese facility. Our detection at 2 GHz in February 2022 is the highest frequency for this FRB and the fluence of $>$ 189 Jy ms is one of the brightest bursts from this FRB source. We place an upper limit on the spectral index $\alpha$ = -2.14 from the detection of the S band and non-detection of the X band at the same time. We compare an event rate of the detected burst with ones of the previous research, and suggest that the power-law of the luminosity function might be broken at lower fluence, and the fluences of bright FRBs distribute up to over 2 GHz with the power-law against frequency. In addition, we show the energy density of the burst detected in this work was comparable to the bright population of one-off FRBs. We propose that repeating FRBs can be as bright as one-off FRBs, and only their brightest bursts could be detected so some of repeating FRBs intrinsically might have been classified as one-off FRBs.