An international research team led by Professor LI Di and Dr. WANG Pei of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) captured an extreme episode of cosmic explosions from Fast Radio Burst (FRB) 121102, using the Five-hundred-meter Spherical Aperture Telescope (FAST). A total of 1,652 independent bursts were detected within 47 days as of August 29, 2019 (UT).
It is the largest FRB event set to date, more than the number reported in the other combined publications. This set of bursts allows to determine, for the first time, the characteristic energy and the energy distribution of any FRB, thus giving light on the central motor that feeds the FRB.
These results were published in Nature on October 13, 2021.
FRBs were first detected in 2007. These cosmic explosions can be up to a thousandth of a second, producing a year of total solar energy production. The origin of the FRBs is still unknown. Although even aliens have been considered in models for FRB, the observations clearly favor natural causes. Recent focuses include exotic stars of hypermagnetized neutrons, black holes, and cosmic strings remaining from the Big Bang.
Scientists have found that a small fraction of FRBs are repeated. This phenomenon facilitates follow-up studies, including the location and identification of FRB host galaxies.
FRB 121102 is the first known repeater and the first well-located FRB. Scientists have identified its origin in a dwarf galaxy. In addition, this FRB is clearly associated with a persistent radio source. Both clues are crucial to solving the FRB’s cosmic mystery. The behavior of FRB 121102 is difficult to predict and is commonly described as “seasonal.”
While testing the FAST FRB backend during the start-up phase, the team noticed that the FRB 121102 acted with frequent bright pulses. Between August 29 and October 29, 2019, 1,652 independent explosions were detected in a total of 59.5 hours. Although the burst rate varied during the series, 122 bursts were seen during rush hour, corresponding to the highest event rate ever observed for any FRB.
This high cadence facilitates a statistical study of these bursts of FRB. The researchers found a clear energy characteristic of E.0= 4.8 × 1037 erg, below which the burst generation became less efficient. The explosion energy distribution can be adequately described as bimodal, i.e. a log-normal function for low E bursts and a Lorentz function for high E bursts, which implies that the Weaker FRB impulses may be stochastic in nature and the strongest involve a relationship between two independent quantities.
“The total energy of this set of bursts already adds 3.8% of what has of a magnet and did not find any periodicity between 1 ms and 1000 s, both serious restrictions of the possibility that FRB 121102 comes of an isolated compact object, ”Dr. WANG said.
More than six new FRBs have been discovered through the Commensal Radio Astronomy FAST Survey (CRAFTS, https://crafts.bao.ac.cn/), including a new repeater similar to 121102. “As the world’s largest antenna, the sensitivity of FAST proves to be conducive to revealing the complexities of cosmic transients, including FRBs, ”Professor LI said.
This project has been part of a long collaboration since the commissioning phase of the FAST telescope. Major partner institutions include Normal University of Guizhou, the University of Nevada Las Vegas, Cornell University, the Max-Planck Institute for Radio Astronomy, the University of West Virginia, CSIRO, the University of California Berkeley and the University of Nanjing. .
Reference: “A bimodal explosion energy distribution from a fast explosion source” by D. Li, P. Wang, WW Zhu, B. Zhang, XX Zhang, R. Duan, YK Zhang, Y. Feng, NY Tang, S Chatterjee, JM Cordes, M. Cruces, S. Dai, V. Gajjar, G. Hobbs, C. Jin, M. Kramer, DR Lorimer, CC Miao, CH Niu, JR Niu, ZC Pan, L. Qian, L Spitler, D. Werthimer, GQ Zhang, FY Wang, XY Xie, YL Yue, L. Zhang, QJ Zhi and Y. Zhu, October 13, 2021, Nature.
DOI: 10.1038 / s41586-021-03878-5