SN2008jb: A "lost" core-collapse supernova in a star-forming dwarf galaxy at ∼10Mpc

J. L. Prieto, J. C. Lee, A. J. Drake, R. McNaught, G. Garradd, J. F. Beacom, Edward C Beshore, M. Catelan, S. G. Djorgovski, G. Pojmanski, K. Z. Stanek, D. M. Szczygieł

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Abstract

We present the discovery and follow-up observations of SN2008jb, a core-collapse supernova in the southern dwarf irregular galaxy ESO 302-14 (MB = -15.3mag) at 9.6Mpc. This nearby transient was missed by galaxy-targeted surveys and was only found in archival optical images obtained by the Catalina Real-time Transient Survey and the All-Sky Automated Survey. The well-sampled archival photometry shows that SN2008jb was detected shortly after explosion and reached a bright optical maximum, V max ≃ 13.6mag (M V, max ≃ -16.5). The shape of the light curve shows a plateau of 100days, followed by a drop of 1.4mag in the V band to a slow decline with an approximate 56Co decay slope. The late-time light curve is consistent with 0.04 ± 0.01 M ω of 56Ni synthesized in the explosion. A spectrum of the supernova obtained two years after explosion shows a broad, boxy Hα emission line, which is unusual for normal TypeII-Plateau supernovae at late times. We detect the supernova in archival Spitzer and WISE images obtained 8-14 months after explosion, which show clear signs of warm (600-700 K) dust emission. The dwarf irregular host galaxy, ESO 302-14, has a low gas-phase oxygen abundance, 12 + log(O/H) = 8.2 (1/5 Z ω), similar to those of the Small Magellanic Cloud and the hosts of long gamma-ray bursts and luminous core-collapse supernovae. This metallicity is one of the lowest among local (≲ 10Mpc) supernova hosts. We study the host environment using GALEX far-UV, R-band, and Hα images and find that the supernova occurred in a large star formation complex. The morphology of the Hα emission appears as a large shell (R ≃ 350pc) surrounding the FUV and optical emission. Using the Hα-to-FUV ratio and FUV and R-band luminosities, we estimate an age of 9Myr and a total mass of 2 × 105 M ω for the star formation complex, assuming a single-age starburst. These properties are consistent with the expanding Hα supershells observed in many well-studied nearby dwarf galaxies, which are tell-tale signs of feedback from the cumulative effect of massive star winds and supernovae. The age estimated for the star-forming region where SN2008jb exploded suggests a relatively high-mass progenitor star with an initial mass M 20 M ω and warrants further study. We discuss the implications of these findings in the study of core-collapse supernova progenitors.

Original languageEnglish (US)
Article number70
JournalAstrophysical Journal
Volume745
Issue number1
DOIs
Publication statusPublished - Jan 20 2012

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Keywords

  • galaxies: dwarf
  • supernovae: general
  • supernovae: individual (SN 2008jb)

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Prieto, J. L., Lee, J. C., Drake, A. J., McNaught, R., Garradd, G., Beacom, J. F., ... Szczygieł, D. M. (2012). SN2008jb: A "lost" core-collapse supernova in a star-forming dwarf galaxy at ∼10Mpc. Astrophysical Journal, 745(1), [70]. https://doi.org/10.1088/0004-637X/745/1/70