Context. The radio emission from magnetars is poorly understood and poorlycharacterized observationally, in particular for what concerns single pulsesand sporadic events. The interest in it was boosted by the detection in 2020 ofan extremely bright ms radio signal from the Galactic magnetar designated SoftGamma Repeater (SGR) SGR J1935+2154, which occurred almost simultaneously witha typical magnetar short burst of X-rays. As of now, this event remains theGalactic radio pulse that is the most reminiscent of fast radio bursts (FRBs)and the only one with a sound association with a known progenitor. Aims. We aimto constrain the rate of impulsive radio events from magnetars, by means of anintensive monitoring using a high-sensitivity radio telescope. Methods. Weperformed a long-term campaign on seven Galactic magnetars (plus one candidate)using the Northern Cross transit radio telescope (in Medicina, Italy) searchingfor short timescales and dispersed radio pulses. Results. We obtained nodetections in more than 560 hours of observation, setting an upper limit at 95%confidence level of <52 yr$^{-1}$ on the rate of events with energy >10$^{28}$erg, which is consistent with limits in literature. Furthermore, under someassumptions on the magnetars properties and energetic behavior, we found thatour upper limits point towards the fact that the entire population of FRBsobserved cannot be explained by radio bursts emitted by magnetars.
The Northern Cross Fast Radio Burst project: V. Search for transient radio emission from Galactic magnetars
P. Esposito;
In corso di stampa
Abstract
Context. The radio emission from magnetars is poorly understood and poorlycharacterized observationally, in particular for what concerns single pulsesand sporadic events. The interest in it was boosted by the detection in 2020 ofan extremely bright ms radio signal from the Galactic magnetar designated SoftGamma Repeater (SGR) SGR J1935+2154, which occurred almost simultaneously witha typical magnetar short burst of X-rays. As of now, this event remains theGalactic radio pulse that is the most reminiscent of fast radio bursts (FRBs)and the only one with a sound association with a known progenitor. Aims. We aimto constrain the rate of impulsive radio events from magnetars, by means of anintensive monitoring using a high-sensitivity radio telescope. Methods. Weperformed a long-term campaign on seven Galactic magnetars (plus one candidate)using the Northern Cross transit radio telescope (in Medicina, Italy) searchingfor short timescales and dispersed radio pulses. Results. We obtained nodetections in more than 560 hours of observation, setting an upper limit at 95%confidence level of <52 yr$^{-1}$ on the rate of events with energy >10$^{28}$erg, which is consistent with limits in literature. Furthermore, under someassumptions on the magnetars properties and energetic behavior, we found thatour upper limits point towards the fact that the entire population of FRBsobserved cannot be explained by radio bursts emitted by magnetars.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
