Unveiling the Spectro-temporal Behavior of Repeating Fast Radio Bursts at High Radio Frequencies

Fast radio bursts (FRBs) are transient pulses of radio emission that have observed temporal widths ranging from microseconds to milliseconds and fluences between ~0.01-1,000 Jy ms. To date, multiple radio bursts have been detected from 22 out of 137 sources, which apparently distinguishes them from the so-far non-repeating FRB population. The radio bursts from repeating FRBs display a wide variety of complex time-frequency structures that encode valuable information about the source's local environment, underlying emission mechanism(s), and the intervening media along the line of sight. In particular, their bursts are often narrowband and sometimes display peculiar spectral behavior, such as bursts with subpulses that drift downwards in frequency with time (the "sad trombone" effect). Simultaneous, broadband multifrequency observations of repeating FRBs are therefore crucial for quantifying their emission behavior and distinguishing between intrinsic and extrinsic effects.