PTF12gzk - A Rapidly Declining, High-Velocity Type Ic Radio Supernova
  Only a few cases of type Ic supernovae (SNe) with high-velocity ejecta have
been discovered and studied. Here we present our analysis of radio and X-ray
observations of a Type Ic SN, PTF12gzk. The radio emission rapidly declined
less than 10 days after explosion, suggesting SN ejecta expanding at high
velocity (~0.3c). The radio data also indicate that the density of the
circumstellar material (CSM) around the supernova is lower by a factor of ~10
than the CSM around normal Type Ic SNe. Our observations of this rapidly
declining radio SN at a distance of 58 Mpc demonstrates the potential to detect
many additional radio SNe, given the new capabilities of the VLA (improved
sensitivity and dynamic scheduling), that are currently missed, leading to a
biased view of radio SNe Ic. Early optical discovery followed by rapid radio
observations would provide a full description of the ejecta velocity
distribution and CSM densities around stripped massive star explosions, as well
as strong clues about the nature of their progenitor stars.
