Is there a mildly relativistic jet in SN2007gr

SN2007gr was an ordinary type Ic supernova, with a hint of asymmetric explosion seen in the optical polarization spectrum. This type of SNe is occasionally associated with long duration gamma-ray bursts which generate ultra-relativistic jets; no relativistic outflows have yet been found by direct imaging in SNe Ib/c explosions. High resolution very long baseline interferometry (VLBI) data and simultaneous total radio flux density measurements indicated that SN2007gr has expanded mildly relativistically. We performed late time Westerbork Synthesis Radio Telescope (WSRT) observations to measure the level of the underlying extended emission. Comparison of the VLBI and the background-subtracted WSRT and independent VLA data indicate an at least partially resolved source with an average expansion velocity of >
0.4c, although the VLBI data could be consistent with a fainter source with an expansion velocity of ∼0.2c as well.