Subjects:High Energy Astrophysical Phenomena (astro-ph.HE)
The repeating fast radio burst (FRB) source FRB 20200120E is exceptional because of its proximity (d=3.6Mpc) and association with a globular cluster. Here we report60bursts detected with the 100-m Effelsberg telescope at 1.4 GHz. We observe large variations in the burst rate, and report the first FRB 20200120E `burst storm', where the source suddenly became active and 53 bursts occurred within only 40 minutes. We find no strict periodicity in the burst arrival times during the storm, nor any evidence for periodicity in the source's activity between observations. The burst storm shows a steep burst energy distribution (power-law indexα=2.39±0.12) and a bi-modal wait-time distribution, with log-normal means of 0.94+0.07−0.06s and 23.61+3.06−2.71s. We attribute these peaks in the wait-time distribution to a characteristic event timescale and pseudo-Poisson burst rate, respectively. The secondary wait-time peak at∼1s is∼50×longer than the∼30ms timescale seen for both FRB 20121102A and FRB 20201124A -- potentially indicating a larger emission region, or slower burst propagation through this region. At the same time, FRB 20200120E shows, on average, order-of-magnitude lower burst durations and luminosities compared with FRB 20121102A and FRB 20201124A. Lastly, in contrast to FRB 20121102A, which has observed dispersion measure (DM) variations ofΔDM>1pc cm−3on month-to-year timescales, we determine that the DM of FRB 20200120E has remained stable (ΔDM<0.15pc cm−3) between measurements separated by>10months. Overall, the observational characteristics of FRB 20200120E deviate quantitatively from other active repeaters, but it is unclear whether it is qualitatively a different type of source.
