Multiwavelength Analysis of the Supernova-associated Low-luminosity GRB 171205A

Multiwavelength properties of the nearby supernova (SN)-associated low-luminosity GRB 171205A are investigated in depth to constrain its physical origin synthetically. The pulse width is found to be correlated with energy with a power-law index of ‑0.24 ± 0.07, which is consistent with the indices of other SN-associated gamma-ray bursts (SN/GRBs) but larger than those of long GRBs. By analyzing the overall light curve of its prompt gamma rays and X-ray plateaus simultaneously, we infer that the early X-rays together with the gamma-rays should reflect the activities of the central engine, while the late X-rays may be dominated by the interaction of external shocks with circumburst material. In addition, we find that the host radio flux and offset of GRB 171205A are similar to those of other nearby low-luminosity GRBs. We adopt nine SN/GRBs with measured offset to build a relation between peak luminosity (L _γ,p ) and spectral lag (τ) as L _γ,p ∝ τ ^{‑1.91±0.33}. The peak luminosity and the projected physical offset of 12 SN/GRBs and 10 kilonova-associated GRBs are found to be moderately correlated, suggesting their different progenitors. The multiwavelength afterglow fitted with a top-hat jet model indicates that the jet half-opening angle and the viewing angle of GRB 171205A are ∼34.°4 and 41.°8, respectively, which implies that the off-axis emissions are dominated by the peripheral cocoon rather than the jet core.