We present ultraviolet, optical, and near-infrared photometry as well as optical spectra of the peculiar supernova (SN) ∼2008ha. SN2008ha had a very low peak luminosity, reaching onlyMV = -14.2mag, and low line velocities of only ∼2000km s-1 near maximum brightness, indicating a very small kinetic energy per unit mass of ejecta. Spectroscopically, SN2008ha is a member of the SN2002cx-like class of SNe, a peculiar subclass of SNeIa; however, SN2008ha is the most extreme member, being significantly fainter and having lower line velocities than the typical member, which is already 2mag fainter and has line velocities ∼5000km s-1 smaller (near maximum brightness) than a normal SNIa. SN2008ha had a remarkably short rise time of only 10 days, significantly shorter than either SN2002cx-like objects (∼15 days) or normal SNeIa (19.5 days). The bolometric light curve of SN2008ha indicates that SN2008ha peaked at L peak = (9.5±1.4) × 1040 erg s-1, making SN2008ha perhaps the least luminous SN ever observed. From its peak luminosity and rise time, we infer that SN2008ha generated (3.0±0.9) × 10-3 M ⊙ of 56Ni, had a kinetic energy of 2 × 1048 erg, and ejected 0.15M ⊙ of material. The host galaxy of SN2008ha has a luminosity, star formation rate, and metallicity similar to those of the Largemagellanic Cloud. We classify three new (and one potential) members of the SN2002cx-like class, expanding the sample to 14 (and one potential) members. The host-galaxy morphology distribution of the class is consistent with that of SNeIa, Ib, Ic, and II. Several models for generating low-luminosity SNe can explain the observations of SN2008ha; however, if a single model is to describe all SN2002cx-like objects, deflagration of carbon-oxygen white dwarfs, with SN2008ha being a partial deflagration and not unbinding the progenitor star, is preferred. The rate of SN2008ha-like events is 10% of the SNIa rate, and in the upcoming era of transient surveys, several thousand similar objects may be discovered, suggesting that SN2008ha may be the tip of a low-luminosity transient iceberg.
- General supernovae
- Individual (UGC 12682) supernovae
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science