Superluminous Supernova SN 2018ibb: Circumstellar Shell and Spectral Effects

The observational effects of the circumstellar gas around the superluminous supernova SN 2018ibb are investigated. The narrow Fe II absorption lines are reproduced in the model of a fragmented cold dense shell between the forward and reverse shocks. The unusual selective absorption in the [O I] emission doublet is explained by the scattering of radiation in the Si II doublet lines in the supernova envelope. It is shown that the [O III] emission doublet at \(t_{\mathrm{max}}+565\) days can be radiated by the supernova envelope, with the asymmetry of the [O III] doublet being explained by the formation of dust in the supernova. Supernova–circumstellar gas interaction modeling in combination with observational data leads to an estimate of the circumstellar shell mass (\({\sim}0.14 M_{\odot}\)).