Since January 2017 , the Commensal Real-time ASKAP Fast Transients survey ( CRAFT ) has been utilising commissioning antennas of the Australian SKA Pathfinder ( ASKAP ) to survey for fast radio bursts ( FRBs ) in fly ’ s eye mode .
This is the first extensive astronomical survey using phased array feeds ( PAFs ) .
A total of 23 FRBs have been reported — here , we present a calculation of the sensitivity and total exposure of the survey that detected the first 20 of these bursts , using the pulsars B1641-45 ( J1644-4559 ) and B0833-45 ( J0835-4510 , i.e .
Vela ) as calibrators .
The design of the survey allows us to benchmark effects due to PAF beamshape , antenna-dependent system noise , radio-frequency interference , and fluctuations during commissioning on timescales from one hour to a year .
Observation time , solid-angle , and search efficiency are calculated as a function of FRB fluence threshold .
Using this metric , effective survey exposures and sensitivities are calculated as a function of the source counts distribution .
Statistical ‘ stat ’ and systematics ‘ sys ’ effects are treated separately .
The implied FRB rate is significantly lower than the 37 sky ^ { -1 } day ^ { -1 } calculated using nominal exposures and sensitivities for this same sample by \citet craft_nature .
At the Euclidean power-law index of -1.5 , the rate is 12.7 _ { -2.2 } ^ { +3.3 } { ( sys ) } \pm 3.6 { ( stat ) } sky ^ { -1 } day ^ { -1 } above a threshold of 56.6 \pm 6.3 { ( sys ) } Jy ms , while for the best-fit index for this sample of -2.2 , it is 20.7 _ { -1.7 } ^ { +2.1 } { ( sys ) } \pm 5.8 { ( stat ) } sky ^ { -1 } day ^ { -1 } above a threshold of 40.4 \pm 1.2 { ( sys ) } Jy ms .
This strongly suggests that these calculations be performed for other FRB-hunting experiments , allowing meaningful comparisons to be made between them .