Broad-line Type Ic supernova SN 2014ad

We present optical and ultraviolet photometry and low-resolution optical spectroscopy of the broad-line Type Ic supernova SN 2014ad in the galaxy PGC 37625 (Mrk 1309), covering the evolution of the supernova during -5 to +87 d with respect to the date of maximum in the B band. A late-phase spectrum obtained at +340 d is also presented. With an absolute V-band magnitude at peak of M_V =-18.86 ± 0.23 mag, SN 2014ad is fainter than supernovae associated with gamma ray bursts (GRBs), and brighter than most of the normal and broadline Type Ic supernovae without an associated GRB. The spectral evolution indicates that the expansion velocity of the ejecta, as measured using the Si II line, is as high as ~33 500 km s^-1 around maximum, while during the post-maximum phase it settles at ~15 000 km s^-1. The expansion velocity of SN 2014ad is higher than that of all other well-observed broad-line Type Ic supernovae except for the GRB-associated SN 2010bh. The explosion parameters, determined by applying Arnett's analytical light-curve model to the observed bolometric lightcurve, indicate that it was an energetic explosion with a kinetic energy of ~(1 ± 0.3) × 10⁵² erg and a total ejected mass of ~(3.3 ± 0.8)M_⊙, and that ~0.24 M_⊙ of ⁵⁶Ni was synthesized in the explosion. The metallicity of the host galaxy near the supernova region is estimated to be ~0.5 Z_⊙.