Application of the Magnetar Engine to an Intermediate-Luminosity Gamma-Ray Burst Associated with the Supernova GRB 201015A/SN 201015A

We present optical photometry for the afterglow of GRB 201015A, which can be classified as a medium-luminosity gamma-ray burst (Lγ,iso≈2.55×1049ergs−1 ) and the associated underlying supernova SN 201015A. A millisecond magnetar engine has been widely suggested to exist in gamma-ray burst (GRB) phenomena. In this paper, we study the effects of the magnetar engine on GRB 201015A/SN 201015A by light curve analysis. We use a smooth broken power-law plus magnetar spin-down model to fit the X-ray and optical light curves of GRB 201015A/SN 201015A. The best-fitting results reveal that the magnetar initial spin period and surface magnetic field at the pole are constrained to be P0=16.80−0.47+0.24ms and Bp=0.80−0.32+0.34×1015G, respectively, and the SN ejected a total mass of Mej=2.55−0.37+1.12M⊙ and an ejecta velocity of vej = 30,000−2500+4800kms−1, inferring a kinetic energy of ESN,K≈1.37×1052erg. From our analysis, we find that the central engine of GRB 201015A/SN 201015A may well be a magnetar, and the emission from a magnetar central engine can be solely responsible for powering SN 201015A.