Constraints on the environment and energetics of the Broad-Line Ic SN2014ad from deep radio and X-ray observations.

Broad-line type Ic Supernovae (BL-Ic SNe) are characterized by high ejecta velocity (greater than or similar to 10(4) km s(-1)) and are sometimes associated with the relativistic jets typical of long duration (greater than or similar to 2 s) Gamma-Ray Bursts. The reason why a small fraction of BL-Ic SNe harbor relativistic jets is not known. Here we present deep X-ray and radio observations of the BL-Ic SN 2014ad extending from 13 to 930 days post explosion. SN 2014ad was not detected at either frequency and has no observational evidence of a GRB counterpart. The proximity of SN 2014ad (d similar to 26 Mpc) enables very deep constraints on the progenitor mass-loss rate (M)over dot and on the total energy of the fast ejecta E. We consider two synchrotron emission scenarios for a wind-like circumstellar medium (CSM): (i) uncollimated nonrelativistic ejecta, and (ii) off-axis relativistic jet. Within the first scenario our observations are consistent with GRB-less BL-Ic SNe characterized by a modest energy budget of their fast ejecta (E less than or similar to 10(45) erg), like SNe 2002ap and 2010ay. For jetted explosions, we cannot rule out a GRB with E less than or similar to 10(51) erg (beam-corrected) with a narrow opening angle (theta(j) similar to 5 degrees) observed moderately off-axis (theta(obs) greater than or similar to 30 degrees) and expanding in a very low CSM density ((M)over dot less than or similar to 10(-6) M-circle dot yr(-1)). Our study shows that off-axis low-energy jets expanding in a low-density medium cannot be ruled out even in the most nearby BL-Ic SNe with extensive deep observations, and might be a common feature of BL-Ic SNe.