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, E. Beshore, M. Catelan, S. G. Djorgovski, G. Pojmanski, K. Z. Stanek, D. M. Szczygieł

Research output: Contribution to journalArticle

15 Scopus citations

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
StatePublished - Jan 20 2012

Keywords

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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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