Non-detection of FAST and Parkes follow-up observation for 27 Parkes discovered FRBs

TL;DR

This study tests whether 27 Parkes-discovered, apparently non-repeating FRBs truly exhibit no repetition by conducting systematic follow-up with the FAST 19-beam receiver and the Parkes Ultra-Wideband Low system. It employs unified observational setups and two statistical models, Poisson and Weibull, to convert non-detections into upper limits on repetition rates, yielding stringent constraints of about $r \in [10^{-3.5}, 10^{-1.9}]\,\mathrm{h^{-1}}$ (Poisson) and $r \in [10^{-3.4}, 10^{-1.5}]\,\mathrm{h^{-1}}$ (Weibull). No repeats were found after $65.3$ hours of follow-up, suggesting these sources belong to a relatively homogeneous population with extremely low intrinsic activity or are genuinely non-repeating on human timescales. The results, enabled by longer integrations and broader bandwidth, tighten previous limits by roughly an order of magnitude and support the existence of an “inactive repeater” population, with important implications for FRB progenitor models and population studies. Future long-term monitoring with highly sensitive instruments like FAST could further tighten these limits or detect rare bursts from these quiet FRBs.

Abstract

To investigate whether apparently non-repeating Fast Radio Bursts (FRBs) are truly one-off transients, we conducted systematic follow-up observations of 27 out of 81 non-repeating FRBs identified in the Parkes Transient Database. Using 59.0 hours of data from the Parkes Ultra-Wideband Low (UWL) receiver and 6.3 hours from the Five-hundred-meter Aperture Spherical Telescope (FAST) 19-beam receiver, we searched for repeated bursts from these sources. No additional bursts were detected from any of the 27 FRBs. Combining these non-detections with prior archival observations, we derived stringent upper limits on their repetition rates above 1 Jy under two statistical models: Poisson process constraints range from $\sim10^{-3.5}$ to $10^{-1.9}\,\mathrm{h^{-1}}$, while Weibull process constraints range from $\sim10^{-3.4}$ to $10^{-1.5}\,\mathrm{h^{-1}}$. These limits are approximately an order of magnitude stricter than those reported in previous studies. By applying consistent observational setups and analytical methodologies across all sources, the derived rate limits converge to a narrow, well-defined range. This suggests that these FRBs form a relatively homogeneous population with extremely low intrinsic activity rates.

Figures (4)

• Figure 1: Limits of Poisson repeating rate $r_{\rm scaled}$ of 27 FRBs. The error bars represent 90% confidence intervals, calculated using the method from possionconfidence to provide improved accuracy for low Poisson event rates.
• Figure 2: Limits of Weibull repeating rate of 27 FRBs. The error bars represent 90% confidence intervals from the posterior probability distribution of $\text{log}\,r$.
• Figure 3: Limits of Poisson repeating rate $r_{\rm scaled}$ of 27 published FRBs from Parkes (26 apparently non-repeating FRBs and the repeating FRB 20180301A). The error bars represent 90% confidence intervals, calculated using the method from possionconfidence to provide improved accuracy for low Poisson event rates.
• Figure 4: The PDF and CDF comparssion of the rate limit from this work and Parkes previous work.