2026ApJ...997..338K

It is known that there is an association between long gamma-ray bursts and supernovae (SNe), and study of these SNe is important for exploring the death of massive stars. Here, we investigate GRB 171205A/SN 2017iuk (at redshift z = 0.0368) by fitting multiband light curves and modeling the SN 2017iuk spectra with SYNAPPS. The light curve of GRB 171205A/SN 2017iuk shows a long plateau, not only in X-rays but also in optical bands. This plateau may be from the late-time contribution of a magnetar central engine. We use a magnetar spindown model, ⁵⁶Ni model, and cooling model to fit the multiband light curves. The best-fitting results reveal the total SN ejected mass ${M}_{{\rm{ej}}}=4.6{0}_{-0.70}^{+1.20}\,{M}_{\odot }$, Ni mass ${M}_{{\rm{Ni}}}=0.3{1}_{-0.03}^{+0.05}\,{M}_{\odot }$, and total kinetic energy E_K ≈ 3.14 × 10⁵² erg, consistent with the average values inferred for other gamma-ray burst-SNe. The best-fitting photospheric velocities are 14,700 and 11,400 km s^–1, and the photospheric temperatures are 9900 and 11,800 K, at +7.2 and +13.2 days (respectively). From our light curves and spectral analysis, we suggest that the central engine of GRB 171205A/SN 2017iuk is likely to be a magnetar, with initial spin period ${P}_{0}=70.6{1}_{-0.97}^{+0.62}\,{\rm{ms}}$ and surface magnetic field at the pole ${B}_{{\rm{p}}}=3.8{4}_{-0.61}^{+0.33}\times 1{0}^{15}\,{\rm{G}}$.