Fast radio bursts (FRBs) are millisecond radio pulses detected from cosmological distances. A large number of models invoke extragalactic magnetars as the sources of these mysterious events. Magnetars are rotating neutron stars with extremely high magnetic fields. They can sporadically emit short bright X-ray/soft Gamma-ray bursts. However, most magnetars are galactic sources and the brightest radio pulses ever detected from magnetars would be undetectable from an extragalactic distance as for FRBs. Moreover, none of the short bursts from magnetars has been simultaneously detected in both radio and X-ray bands. The hard link between FRBs and magnetars was missing until an FRB like event (FRB 200428) was detected from a galactic magnetar soft-gamma repeater (SGR) J1935+2154 and a hard X-ray burst associated with it. We monitored SGR J1935+2154 with FAST and did not detect any radio pulse associated with hard X-ray bursts in the same active period. These zero detections placed a fluence upper limit eight orders of magnitude deeper than the fluence of FRB 200428. Our results indicate that although magnetars can be the source of FRBs, the FRB and magnetar burst associations are very rare.

BIO
Dr. Lin Lin is a faculty member in the Department of Astronomy of Beijing Normal University (BNU). She received her PhD in astrophysics from NAOC in 2011. She used to work as a research assistant or post-doc at University of Alabama in Huntsville (US), Sabanci University (Turkey), University of Paris 7 (France). Her research interests include magnetars, fast radio bursts, gamma-ray bursts, etc.