SN 2002bj
Supernova
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SN 2002bj was the explosion of a star in the galaxy NGC 1821, located in the constellation Lepus.[3] The explosion was discovered by Jack Newton in scans of images produced by Tim Puckett. (It was independently discovered by the Lick/Tenagra Observatory as part of their combined supernova search program.) Initially it had an apparent magnitude of about 14.7[4] and was categorized as a Type IIn supernova.[5] However, in 2008 Dovi Poznanski discovered that the spectrum more closely resembled a Type Ia supernova. Further, the energy output was much lower than a typical supernova and the luminosity dropped at a dramatic pace.[6]
Light curves in four photometric bands for SN 2002bj, plotted from data published by Poznanski et al.[1] | |
| Event type | Supernova, variable star  |
|---|---|
| SN.IIn | |
| Constellation | Lepus |
| Right ascension | 05h 11m 46.41s[2] |
| Declination | −15° 08′ 10.8″[2] |
| Epoch | J2000 |
| Other designations | SN 2002bj, AAVSO 0507-15 |
A team consisting of Poznanski, Joshua Bloom, Alex Filippenko and others concluded that it was a new category of exploding star. This system is believed to consist of a binary pair of white dwarf stars, with helium being transferred from one dwarf to the other. The accreted helium exploded in a thermonuclear reaction on the surface of the more massive white dwarf, resulting in the observed outburst.[6] In this sense, it was akin to a nova explosion, although the magnitude of the explosion was a thousand times greater.[3] In 2007 Lars Bildsten et al. had predicted this category of explosion would occur in AM Canum Venaticorum star binary systems.[7]
NGC 1821 is an irregular galaxy categorized as type IB(s)m. It is apparent magnitude 14.5 and has a redshift of 0.012029. This galaxy is located about 48 megaparsecs from the Earth.[8]