A Search For Relativistic Explosions in a Sample of ZTF BL-Ic SNe

Long duration gamma-ray bursts (GRBs) are a rare subclass of stripped-envelope core-collapse supernovae (SNe) that launch collimated relativistic outflows (jets). All supernovae associated with long-duration GRBs are of the broad-lined Type Ic spectroscopic class, but the fraction of broad-lined SNe Ic harboring low-luminosity GRBs remains largely unconstrained. Some SNe should be accompanied by off-axis GRB jets that initially remain invisible, but then emerge as strong radio sources as the jets spread laterally. However, this critical prediction of the jet model for GRBs has yet to be verified observationally. Here we present radio (Jansky Very Large Array) and X-ray (Chandra, Swift/XRT) observations of broad-lined Type Ic supernovae discovered in the first 3 years of operations of the Zwicky Transient Facility, in order to search for evidence of relativistic ejecta and/or central engine activity. Most of the SNe in our sample exclude radio emission observationally similar to that of the radio-loud, relativistic SN 1998bw. Many events in our sample also exclude off-axis jets similar to GRB 031203 and GRB 030329, but we cannot rule out the entire parameter space of off-axis models. We place limits on the fraction of broad-lined SNe Ic that harbor relativistic jets, and discuss implications on GRB progenitor models.