FRB 180916

Periodicity

Prior to the publication of the study in Nature, only two types of FRBs had been observed: non-repeaters and repeaters. Non-repeaters are 'one-off' FRBs, possibly associated with catastrophic stellar events. In contrast, repeaters are not one-off, but instead manifest recurring unpredictable, sporadic, and irregular radiation bursts; their sources are less well understood. FRB 180916 seems to represent a third and new type of FRB that may be termed periodic repeater. The radiation activity of FRB 180916 repeats over a period of 16.35 +/-0.18 days. Broadly, FRB 180916 emits a burst of radiation for approximately four days followed by an inactive period of about 12 days, then the cycle repeats. Additional follow-up studies of the repeating FRB by the Swift XRT and UVOT instruments were reported on 4 February 2020; by the Sardinia Radio Telescope (SRT) and Medicina Northern Cross Radio Telescope (MNC), on 17 February 2020; and, by the Galileo telescope in Asiago, also on 17 February 2020. Further observations were made by the Chandra X-ray Observatory on 3 and 18 December, 2019, with no significant x-ray emissions detected at the FRB 180916 location, or from the host galaxy SDSS J015800.28+654253.0. On 6 April 2020, follow-up studies by the Global MASTER-Net were reported on The Astronomer's Telegram and, on 4 June 2020, further follow-up studies were reported with the Giant Metrewave Radio Telescope (uGMRT). On 7 June 2020, astronomers from Jodrell Bank Observatory reported possible evidence that FRB 121102 exhibits the same radio burst behavior ("radio bursts observed in a window lasting approximately 90 days followed by a silent period of 67 days") every 157 days, suggesting that the bursts may be associated with "the orbital motion of a massive star, a neutron star or a black hole". This behavior is nearly "10 times longer than the 16-day periodicity" exhibited by FRB 180916. In March 2021, another burst from the FRB was reported. On 25 August 2021, further observations were reported.