As a backend to the first station of the Long Wavelength Array ( LWA1 ) the Prototype All Sky Imager ( PASI ) has been imaging the sky > -26 ^ { \circ } declination during 34 Gamma Ray Bursts ( GRBs ) between January 2012 and May 2013 .
Using this data we were able to put the most stringent limits to date on prompt low frequency emission from GRBs .
While our limits depend on the zenith angle of the observed GRB , we estimate a 1 \sigma RMS sensitivity of 68 , 65 and 70 Jy for 5 second integrations at 37.9 , 52.0 , and 74.0 MHz at zenith .
These limits are relevant for pulses \geq 5 s and are limited by dispersion smearing .
For pulses of length 5 s we are limited to dispersion measures ( DM s ) \leq 220 , 570 , and 1,600 pc cm ^ { -3 } for the frequencies above .
For pulses lasting longer than 5s , the DM limits increase linearly with the duration of the pulse .
We also report two interesting transients , which are , as of yet , of unknown origin , and are not coincident with any known GRBs .
For general transients , we give rate density limits of \leq 7.5 \times 10 ^ { -3 } , 2.9 \times 10 ^ { -2 } , and 1.4 \times 10 ^ { -2 } yr ^ { -1 } deg ^ { -2 } with pulse energy densities > 1.3 \times 10 ^ { -22 } , 1.1 \times 10 ^ { -22 } , and 1.4 \times 10 ^ { -22 } J m ^ { -2 } Hz ^ { -1 } and pulse widths of 5 s at the frequencies given above .