Supernova 2008J: early time observations of a heavily reddened SN 2002ic-like transient

TL;DR

This paper presents early observations of supernova 2008J, showing it as a Type Ia supernova interacting with circumstellar material, with detailed spectral analysis revealing properties of the surrounding environment and the supernova's intrinsic features.

Contribution

It provides the first near-infrared spectrum of a 2002ic-like supernova and offers detailed analysis of its circumstellar interaction and spectral characteristics.

Findings

SN 2008J is heavily reddened with A_V~1.9 mag.

Spectral features resemble SN 2002ic and 1991T-like events.

Circumstellar material shows wind velocity of ~50 km/s.

Abstract

We provide additional observational evidence that some Type Ia supernovae (SNe Ia) show signatures of circumstellar interaction (CSI) with hydrogen-rich material. Early phase optical and near-infrared (NIR) light curves and spectroscopy of SN 2008J obtained by the Carnegie Supernova Project are studied and compared to those of SNe 2002ic and 2005gj. Our NIR spectrum is the first obtained for a 2002ic-like object extending up to 2.2 $\mu$m. A published high-resolution spectrum is used to provide insight on the circumstellar material (CSM). SN 2008J is found to be affected by $A_V\sim$ 1.9 mag of extinction and to closely resemble SN 2002ic. Spectral and color comparison to SNe 2002ic and 2005gj suggests $R_V$ $<$ 3.1. Spectral decomposition reveals the underlying SN emission matches a 1991T-like event and, since SN 2008J is as luminous as SN 2005gj ($V_{\rm max}$ $=$ $-$20.3 mag), we conclude that their CSI emissions are similarly robust. The high-resolution spectrum reveals narrow emission lines produced from un-shocked gas characterized by a wind velocity of $\sim$ 50 km s$^{-1}$. We conclude that SN 2008J best matches an explosion of a SN Ia that interacts with its CSM.