A 4200-h HyperFlash and ÉCLAT campaign on the hyperactive FRB: constraining energetics with the most brilliant bursts

Hyperactive repeaters provide a unique window into the evolving environments and energy budgets of fast radio burst (FRB) sources, though they may not be representative of the FRB population in general. High-cadence observations are key to capturing the rarest and most energetic bursts, which occur only once per hundreds to thousands of hours. Here, we present an unprecedented 4200-h observing campaign targeting FRB 20240114A as part of the HyperFlash and ÉCLAT FRB monitoring programs. Over 806 d, we detected 178 high-energy ($\sim 10^{40-42}$ erg) bursts with HyperFlash, which together amount to $4.4 \times 10^{42}$ erg of released radio energy (assuming isotropic emission and 1-GHz emission bandwidth). The cumulative energy of the HyperFlash bursts is about twice that of $\sim 11{\,}000$ lower-energy bursts detected with FAST, emphasizing the significant role that the highest-energy bursts play in depleting the central engine’s stored energy. In fact, the single most brilliant burst from our sample, which we term the STROOP, contributes roughly $1/3$ of all the energy we measure, and is at the maximum energy seen in studies of both repeating and apparently one-off FRBs alike. We also find a break in the burst energy distribution at $\sim 2\times 10^{40}$ erg and a linear dispersion measure (DM) increase of $+0.96 \pm 0.06$ pc cm$^{-3}$ over a period of 318 days. We discuss these findings in the context of a magnetar source model and highlight comparisons with the energetics of intermediate and giant X-ray/$\gamma$-ray flares from Galactic sources.