 Light curves for SN 2005gj in fourphotometric bands, plotted from data published by Prietoet al. (2007)[1] | |
| Event type | Supernova  |
|---|---|
| Ia/IIn "hybrid" | |
| Date | September 27, 2005 |
| Constellation | Cetus |
| Epoch | J2000.0 |
| Distance | 864 millionlight years (265 millionparsecs) |
| Redshift | 0.0592, 0.0595, 0.0596, 0.06, 0.0621 |
| Progenitor | White dwarf |
| Notable features | Proposed "quark nova". |
| Other designations | SN 2005gj, SDSS-II SN 4524 |
SN 2005gj was asupernova located approximately 864 millionlight years (265 millionparsecs) away from Earth. It was discovered on September 27, 2005, by theSloan Digital Sky Survey and theNearby Supernova Factory.[3][4] 2005gj was noted because it had qualities of bothType Ia andType IIn supernovae, and becausehydrogenemission lines were found in its spectrum (seehydrogen spectral series).[4] These hydrogen lines, which were found on the spectrum atredshift z=0.0613, are thought to be indicative of interactions with a circumstellar medium (CSM; a donut-shaped,nebula-like ring of matter around a star) by the supernova's ejected matter orwhite dwarf progenitor.[5] Such emission lines are extremely rare in Type Ia supernovae – only one other Type Ia,SN 2002ic, has been observed to exhibit the same properties.[6][7] However, 2005gj's CSM interaction was much stronger and more clearly observed than 2002ic's. The mass-loss history 2005gj's hydrogen lines suggest has been cited as evidence thatluminous blue variable (LBV)hypergiants can be progenitors of thermonuclear supernovae.[8]
2005gj was also noted for its overluminosity. With alight curve that maximised 14–47 days after the initial observation,[5] it was three times more luminous thanSN 1991T (which was, at the time of its 1991 discovery, the brightest Ia supernova on record), 1.5 times more luminous thanSN 2002ic,[5] and close to 100 times more luminous than previously thought possible.[9] Scientists Denis Leahy and Rachid Ouyed from theUniversity of Calgary contend that the incidence of aquark nova, a very luminous process involving the degeneration ofneutrons into their constituentquarks, could explain the unusual magnitude of the luminosity.[10]
