FRB$-$SRB$-$XRB: Geometric and Relativistic Beaming Constraints of Fast Radio Bursts from the Galactic Magnetar SGR J1935+2154

Understand

The detection of a fast radio burst (FRB), FRB 200428, coincident with an X-ray burst (XRB) from the Galactic magnetar soft gamma repeater (SGR) SGR J1935+2154 suggests that magnetars can produce FRBs.

• Many XRBs have been detected from the source, but very few were found to be associated with bursty radio emission.
• Meanwhile, a number of weaker radio bursts have been detected from the source, which could in principle be slow radio bursts (SRBs): FRBs detected at viewing angles outside the FRB jet cone.
• In this paper, we use these X-ray and radio observations to constrain the geometric and relativistic beaming factors of FRBs under two hypotheses.