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

¹ The Oskar Klein Centre, Department of AstronomyStockholm University, AlbaNova, 10691 Stockholm, Sweden
e-mail: ftadd@astro.su.se
² Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
³ Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena, Chile
⁴ Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA, USA
⁵ INAF – Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ Departamento de Astronomia, Universidad de Chile, Casilla 36D, Santiago, Chile
⁷ Argelander Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53111 Bonn, Germany
⁸ Kavli Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan
⁹ N. Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warszawa, Poland
¹⁰ The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
¹¹ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
¹² Department of Physics and Astronomy, Texas A&M University, College Station, TX 77845, USA
¹³ The Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX 77845, USA

Received: 25 July 2012
Accepted: 21 August 2012

Abstract

Aims. We provide additional observational evidence that some Type Ia supernovae (SNe Ia) show signatures of circumstellar interaction (CSI) with hydrogen-rich material.

Methods. 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 μm. A published high-resolution spectrum is used to provide insight on the circumstellar material (CSM).

Results. SN 2008J is found to be affected by A_V ~ 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_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 ~50 km s^-1. We conclude that SN 2008J best matches an explosion of a SN Ia that interacts with its CSM.