SN 2008ha: An extremely low luminosity and exceptionally low energy supernova

Ryan J. Foley, Ryan Chornock, Alexei V. Filippenko, Mohan Ganeshalingam, Robert P. Kirshner, Weidong Li, S. Bradley Cenko, Peter J. Challis, Andrew S. Friedman, Maryam Modjaz, Jeffrey M. Silverman, W. Michael Wood-Vasey

    Research output: Contribution to journalArticle

    Abstract

    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.

    Original languageEnglish (US)
    Pages (from-to)376-391
    Number of pages16
    JournalAstronomical Journal
    Volume138
    Issue number2
    DOIs
    StatePublished - 2009

    Keywords

    • Galaxies
    • General supernovae
    • Individual
    • Individual (UGC 12682) supernovae

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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    Foley, R. J., Chornock, R., Filippenko, A. V., Ganeshalingam, M., Kirshner, R. P., Li, W., Cenko, S. B., Challis, P. J., Friedman, A. S., Modjaz, M., Silverman, J. M., & Wood-Vasey, W. M. (2009). SN 2008ha: An extremely low luminosity and exceptionally low energy supernova. Astronomical Journal, 138(2), 376-391. https://doi.org/10.1088/0004-6256/138/2/376