| SN 2005df | |
| Event Type: | Supernova |
| Class: | Type Ia |
| Start Time: | August 4, 2005 (UTC) |
| Gal: | l = 274.49°, b = −41.2° |
| Distance: | 12.59± |
| Redshift: | 0.0043 |
| Notes: | First supernovae observed in NGC 1559 since 1986; brightest of 2005. |
| Peak: | 12.3 |
SN 2005df was a Type Ia supernova in the barred spiral galaxy NGC 1559, which is located in the southern constellation of Reticulum. The event was discovered in Australia by Robert Evans on the early morning of August 5, 2005 with a 13.8 magnitude, and was confirmed by A. Gilmore on August 6. The supernova was classified as Type Ia by M. Salvo and associates. It was positioned at an offset of east and north of the galaxy's nucleus, reaching a maximum brightness of 12.3 on August 18. The supernova luminosity appeared unreddened by dust from its host galaxy.
The progenitor was a carbon-oxygen white dwarf close to the Chandrasekhar limit, making a merger scenario unlikely. Modelling of the explosion shows a low central density for a hydrogen accretion scenario, suggesting the donating companion was a helium star or a tidally-disrupted white dwarf. Alternatively, the progenitor may have undergone some form of central mixing.