Confined massive circumstellar shell in type IIL SN 2008fq

TL;DR

This paper investigates the circumstellar environment of type IIL supernovae, revealing a massive, confined shell around SN 2008fq through spectral analysis, which differs significantly from type IIP supernovae.

Contribution

It introduces a model linking spectral absorption features to a massive, confined circumstellar shell in type IIL supernovae, highlighting differences from type IIP supernovae.

Findings

Detection of radiatively accelerated preshock wind up to ~800 km/s.

Identification of a dense shell of ~0.08 Msun around SN 2008fq.

Comparison showing larger shell mass in type IIL than in type IIP supernovae.

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.