GRB 171205A/SN 2017iuk: Is the Central Engine a Magnetar?

Abstract 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, 56 Ni model, and cooling model to fit the multiband light curves. The best-fitting results reveal the total SN ejected mass M ej = 4.6 0 − 0.70 + 1.20 M ⊙ , Ni mass M Ni = 0.3 1 − 0.03 + 0.05 M ⊙ , and total kinetic energy E K ≈ 3.14 × 10 52 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 ms and surface magnetic field at the pole B p = 3.8 4 − 0.61 + 0.33 × 1 0 15 G .