An Unusually Fast-Evolving Supernova

TL;DR

This paper reports on SN2002bj, a supernova with an unusually rapid light curve and unique spectral features, suggesting a new class of helium detonation progenitors on white dwarfs.

Contribution

It introduces SN2002bj as a potential example of helium detonation supernovae, expanding the understanding of supernova diversity.

Findings

SN2002bj has a very rapid rise and decline in brightness.

Its spectrum shows helium and intermediate-mass elements, but no hydrogen or iron-peak elements.

It may represent a new class of helium detonation supernovae.

Abstract

Analyses of supernovae (SNe) have revealed two main types of progenitors: exploding white dwarfs and collapsing massive stars. We present SN2002bj, which stands out as different from any SN reported to date. Its light curve rises and declines very rapidly, yet reaches a peak intrinsic brightness greater than -18 mag. A spectrum obtained 7 days after discovery shows the presence of helium and intermediate-mass elements, yet no clear hydrogen or iron-peak elements. The spectrum only barely resembles that of a Type Ia supernova, with added carbon and helium. Its properties suggest that SN2002bj may be representative of a class of progenitors that previously has been only hypothesized: a helium detonation on a white dwarf, ejecting a small envelope of material. New surveys should find many such objects, despite their scarcity.