We report the discovery of a highly dispersed fast radio burst , FRB 181123 , from an analysis of \sim 1500 hr of drift-scan survey data taken using the Five-hundred-meter Aperture Spherical radio Telescope ( FAST ) .
The pulse has three distinct emission components , which vary with frequency across our 1.0–1.5 GHz observing band .
We measure the peak flux density to be > 0.065 Jy and the corresponding fluence > 0.2 Jy ms. Based on the observed dispersion measure of 1812 cm ^ { -3 } pc , we infer a redshift of \sim 1.9 .
From this , we estimate the peak luminosity and isotropic energy to be \lesssim 2 \times 10 ^ { 43 } erg s ^ { -1 } and \lesssim 2 \times 10 ^ { 40 } erg , respectively .
With only one FRB from the survey detected so far , our constraints on the event rate are limited .
We derive a 95 % confidence lower limit for the event rate of 900 FRBs per day for FRBs with fluences > 0.025 Jy ms. We performed follow-up observations of the source with FAST for four hours and have not found a repeated burst .
We discuss the implications of this discovery for our understanding of the physical mechanisms of FRBs .