Confined massive circumstellar shell in type IIL SN 2008fq

Abstract

I explore a phenomenon of the circumstellar H alpha and H beta absorption lines in the spectrum of luminous type IIL SN 2008fq taken on day 6.8 after the discovery. The absorpion is identified with the radiatively accelerated preshock wind up to ~800 km/s. The required initial luminosity is attributed to the earlier circumstellar interaction with the confined dense shell of ~0.08 Msun. The modelling of similar luminous type IIL SN 1998S based on the same approach results in the comparable shell mass of ~0.1 Msun. More than 1 dex larger mass of the confined dense shell of both SNe IIL compared to that of type IIP supernovae is attributed to the larger progenitor mass of type IIL supernovae.