Since the first discovery of a broad-lined type Ic supernova (SN) with a long-duration gamma-ray burst (GRB) in 1998, fewer than fifty GRB-supernovae (SNe) have been discovered. The intermediate-luminosity Swift GRB 161219B and its associated supernova SN 2016jca, which occurred at a redshift of z = 0.1475, represents only the seventh GRB-SN to have been discovered within 1 Gpc, and hence provides an excellent opportunity to investigate the observational and physical properties of these very elusive and rare type of SN. As such, we present optical to near-infrared photometry and optical spectroscopy of GRB 161219B and SN 2016jca, spanning the first three months since its discovery. GRB 161219B exploded in the disk of an edge-on spiral galaxy at a projected distance of 3.4 kpc from the galactic centre. GRB 161219B itself is an outlier in the E - E plane, while SN 2016jca had a rest-frame, peak absolute V-band magnitude of M = - 19.0 ± 0.1, which it reached after 12.3 ± 0.7 rest-frame days. We find that the bolometric properties of SN 2016jca are inconsistent with being powered solely by a magnetar central engine, and demonstrate that it was likely powered exclusively by energy deposited by the radioactive decay of nickel and cobalt into their daughter products, which were nucleosynthesised when its progenitor underwent core collapse. We find that 0.22 ± 0.08M of nickel is required to reproducethe peak luminosity of SN 2016jca, and we constrain an ejecta mass of 5.8 ± 0.3M and a kinetic energy of 5.1 ± 0.8 × 10 erg. Finally, we report on a chromatic, pre-maximum bump in the g-band light curve, and discuss its possible origin.© ESO, 2017.
L.I., C.T., Z.C., A.d.U.P. and D.A.K. acknowledge support from the Spanish research project AYA 2014-58381-P. C.T. and A.d.U.P. furthermore acknowledge support from Ramon y Cajal fellowships RyC-2012-09984 and RyC-2012-09975. D.A.K. and Z.C. acknowledge support from Juan de la Cierva Incorporacion fellowships IJCI-2015-26153 and IJCI-2014-21669. R.S.R. is supported by a 2016 BBVA Foundation Grant for Researchers and Cultural Creators. T.-W. Chen and T. Kruhler acknowledge the support through the Sofia Kovalevskaja Award to P. Schady from the Alexander von Humboldt Foundation of Germany. D.M. acknowledges support from the Instrument center for Danish Astrophysics (IDA).