2021MNRAS.504.2014C

I explore a phenomenon of the circumstellar H α and H β absorption lines in the spectrum of the luminous type IIL SN 2008fq taken on day 6.8 after the discovery. The absorption is identified with the radiatively accelerated pre-shock wind up to ∼800 km s^–1. The required initial luminosity is attributed to earlier circumstellar interaction with the confined dense shell of ∼0.08 M_☉. Modelling of a similar luminous type IIL SN 1998S based on the same approach results in a comparable shell mass of ∼0.1 M_☉. The larger mass of more than 1 dex for the confined dense shells of both SNe IIL compared to that of type IIP supernovae is attributed to the larger progenitor mass of type IIL supernovae.