Observational Characteristics and Possible Asphericity of Over-Luminous Type Ia Supernovae

Abstract

A few Type Ia supernovae (SNe Ia) have been suggested to be an explosion of a super-Chandrasekhar-mass white dwarf (WD) to account for their large luminosities, requiring a large amount of 56Ni. However, the candidate over-luminous SNe Ia 2003fg, 2006gz, and (moderately over-luminous) SN 1991T, have very different observational features: the characteristic time-scale and velocity are very different. We examine if and how the diversity can be explained, by 1D spherical radiation transport calculations covering a wide range of model parameters (e.g., WD mass). The observations of SN 2006gz are naturally explained by the super-Chandrasekhar-mass model. SN 1991T represents a marginal case, which may either be a Chandrasekhar or a super-Chandrasekhar-mass WD explosion. On the other hand, the low velocity and short time-scale seen in SN 2003fg indicate that the ejecta mass is smaller than the Chandrasekhar-mass, which is an apparent contradiction to the large luminosity. We suggest that the problem is solved if the progenitor WD, and thus the SN explosion, is aspherical. This may reflect a rapid rotation of the progenitor star, likely a consequence of the super-Chandrasekhar-mass WD progenitor. The observed differences between SNe 2003fg and 2006gz may be attributed to different viewing orientations.

12 pages, 8 figures, 1 table. Accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (9)

• The Luminous and Carbon-Rich Supernova 2006gz: A Double Degenerate Merger?
• Asphericity in Supernova Explosions from Late-Time Spectroscopy
• The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?
• A three-dimensional deflagration model for Type Ia supernovae confronted with observations
• Double-peaked Oxygen Lines Are not Rare in Nebular Spectra of Core-Collapse Supernovae
• The evolution of the peculiar Type Ia supernova SN 2005hk over 400 days
• Abundance stratification in Type Ia Supernovae - II: The rapidly declining, spectroscopically normal SN 2004eo
• Light curves for off-centre ignition models of type Ia supernovae
• Multi-Dimensional Simulations for Early Phase Spectra of Aspherical Hypernovae: SN 1998bw and Off-Axis Hypernovae

Cited by in corpus (2)

• CfA3: 185 Type Ia Supernova Light Curves from the CfA
• On the progenitors of super-Chandrasekhar mass type Ia supernovae