Physical Constraints On Fast Radio Burst

Understand

Fast Radio Bursts (FRBs) are isolated, $\ms$ radio pulses with dispersion measure (DM) of order $10^3\DMunit$.

• Galactic candidates for the DM of high latitude bursts detected at $\GHz$ frequencies are easily dismissed.
• DM from bursts emitted in stellar coronas are limited by free-free absorption and those from HII regions are bounded by the nondetection of associated free-free emission at radio wavelengths.
• Thus, if astronomical, FRBs are probably extra-galactic.