We present single-epoch radio afterglow observations of 24 long-duration gamma-ray burst ( GRB ) on a timescale of \gtrsim 100 d after the burst .
These observations trace the afterglow evolution when the blastwave has decelerated to mildly- or non-relativistic velocities and has roughly isotropized .
We infer beaming-independent kinetic energies using the Sedov-Taylor self-similar solution , and find a median value for the sample of detected bursts of about 7 \times 10 ^ { 51 } erg , with a 90 \% confidence range of 1.1 \times 10 ^ { 50 } -3.3 \times 10 ^ { 53 } erg .
Both the median and 90 \% confidence range are somewhat larger than the results of multi-wavelength , multi-epoch afterglow modeling ( including large beaming corrections ) , and the distribution of beaming-corrected \gamma -ray energies .
This is due to bursts in our sample with only a single-frequency observation for which we can only determine an upper bound on the peak of the synchrotron spectrum .
This limitation leads to a wider range of allowed energies than for bursts with a well-measured spectral peak .
Our study indicates that single-epoch centimeter-band observations covering the spectral peak on a timescale of \delta t \sim 1 yr can provide a robust estimate of the total kinetic energy distribution with a small investment of telescope time .
The substantial increase in bandwidth of the EVLA ( up to 8 GHz simultaneously with full coverage at 1 - 40 GHz ) will provide the opportunity to estimate the kinetic energy distribution of GRBs with only a few hours of data per burst .