SN 2005df

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^[3] with a 13.8 magnitude,^[2] and was confirmed by A. Gilmore on August 6.^[7] The supernova was classified as Type Ia by M. Salvo and associates.^[8][5] It was positioned at an offset of 15.0″ east and 40.0″ north of the galaxy's nucleus,^[2] reaching a maximum brightness of 12.3 on August 18.^[7] The supernova luminosity appeared unreddened by dust from its host galaxy.^[9]

SN 2005df

SN 2005df is visible as the bright star just above the galaxy at center[1]
Event type	Supernova
Type Ia[2]
Date	August 4, 2005[2] (UTC)
Constellation	Reticulum
Right ascension	04h 17m 37.85s[3]
Declination	−62° 46′ 09.5″[3]
Epoch	J2000
Galactic coordinates	l = 274.49°, b = −41.2°[2]
Distance	12.59 ± 0.20 Mpc (41.06 ± 0.65 Mly)[4]
Redshift	0.0043[2]
Host	NGC 1559[2]
Progenitor type	white dwarf[5]
Notable features	First supernovae observed in NGC 1559 since 1986; brightest of 2005.[6]
Peak apparent magnitude	12.3[7]

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.^[5]