We report on a VLA survey for late-time radio emission from 59 supernovae ( SNe ) of Type I b/c , which have been associated with long-duration gamma-ray bursts ( GRBs ) .
An “ off-axis ” GRB burst ( i.e .
whose relativistic jet points away from us ) is expected to have late-time radio emission even in the absence of significant prompt gamma-ray emission .
From our sample , we detected only SN 2003gk with an 8.4-GHz flux density of 2260 \pm 130 \mu Jy .
Our subsequent VLBI observations of SN 2003gk , at an age of \sim 8 yr , allowed us to determine its radius to be ( 2.4 \pm 0.4 ) \times 10 ^ { 17 } cm , or 94 \pm 15 light days .
This radius rules out relativistic expansion as expected for an off-axis GRB jet , and instead suggests an expansion speed of \sim 10 \ > 000 km s ^ { -1 } typical for non-relativistic core-collapse supernovae .
We attribute the late-onset radio emission to interaction of the ejecta with a dense shell caused by episodic mass-loss from the progenitor .

In addition , we present new calculations for the expected radio lightcurves from GRB jets at various angles to the line of sight , and compare these to our observed limits on the flux densities of the remainder of our SN sample .
From this comparison we can say that only a fraction of broadlined Type I b/c SNe have a radio-bright jet similar to those seen for GRB afterglows at cosmological distances .
However , we also find that for a reasonable range of parameters , as might be representative of the actual population of GRB events rather than the detected bright ones , the radio emission from the GRB jets can be quite faint , and that at present , radio observations do not place strong constraints on off-axis GRB jets .