FRB 121102 , the only repeating fast radio burst ( FRB ) known to date , was discovered at 1.4 GHz and shortly after the discovery of its repeating nature , detected up to 2.4 GHz ( 34 ; 31 ) .
Here we present three bursts detected with the 100-m Effelsberg radio telescope at 4.85 GHz .
All three bursts exhibited frequency structure on broad and narrow frequency scales .
Using an autocorrelation function analysis , we measured a characteristic bandwidth of the small-scale structure of 6.4 \pm 1.6 MHz , which is consistent with the diffractive scintillation bandwidth for this line of sight through the Galactic interstellar medium ( ISM ) predicted by the NE2001 model ( 5 ) .
These were the only detections in a campaign totaling 22 hours in 10 observing epochs spanning five months .
The observed burst detection rate within this observation was inconsistent with a Poisson process with a constant average occurrence rate ; three bursts arrived in the final 0.3 hr of a 2 hr observation on 2016 August 20 .
We therefore observed a change in the rate of detectable bursts during this observation , and we argue that boosting by diffractive interstellar scintillations may have played a role in the detectability .
Understanding whether changes in the detection rate of bursts from FRB 121102 observed at other radio frequencies and epochs are also a product of propagation effects , such as scintillation boosting by the Galactic ISM or plasma lensing in the host galaxy ( 8 ) , or an intrinsic property of the burst emission will require further observations .