Prieto, J. L. and Lee, J. C. and Drake, A. J. and McNaught, R. and Garradd, G. and Beacom, J. F. and Beshore, E. and Catelan, M. and Djorgovski, S. G. and Pojmanski, G. and Stanek, K. Z. and Szczygieł, D. M. (2012) SN 2008jb: A "Lost" Core-collapse Supernova in a Star-forming Dwarf Galaxy at ~10 Mpc. Astrophysical Journal, 145 (1). p. 70. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120405-154548859
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We present the discovery and follow-up observations of SN 2008jb, a core-collapse supernova in the southern dwarf irregular galaxy ESO 302–14 (M_B = –15.3 mag) at 9.6 Mpc. 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 SN 2008jb was detected shortly after explosion and reached a bright optical maximum, V_max ≃ 13.6 mag (M_(V, max) ≃ –16.5). The shape of the light curve shows a plateau of ~100 days, followed by a drop of ~1.4 mag in the V band to a slow decline with an approximate ^(56)Co decay slope. The late-time light curve is consistent with 0.04 ± 0.01 M_☉ of ^(56)Ni 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 Type II-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_☉), 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 (≲10 Mpc) 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 ≃ 350 pc) surrounding the FUV and optical emission. Using the Hα-to-FUV ratio and FUV and R-band luminosities, we estimate an age of ~9 Myr and a total mass of ~2 × 10^5 M_☉ 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 SN 2008jb exploded suggests a relatively high-mass progenitor star with an initial mass M ~ 20 M_☉ and warrants further study. We discuss the implications of these findings in the study of core-collapse supernova progenitors.
|Additional Information:||© 2012 American Astronomical Society. Received 2011 July 23; accepted 2011 October 10; published 2011 December 29. We thank John Mulchaey for obtaining one of the Magellan images presented in this work; Chris Kochanek for detailed comments; Rupali Chandar, Crystal Martin, and Linda Watson for discussions; and Chris Burns for providing his image subtraction code. We also thank the anonymous referee for a careful reading of the manuscript. We are indebted to the staff of Las Campanas Observatory for their assistance. J.L.P. acknowledges support from NASA through Hubble Fellowship Grant HF-51261.01-A awarded by STScI, which is operated by AURA, Inc. for NASA, under contract NAS 5-2655. J.F.B. is supported by the National Science Foundation CAREER Grant PHY-0547102. G.P. is supported by the Polish MNiSW Grant N203 007 31/1328. K.S.Z. and D.M.S. are supported in part by NSF Grant AST-0908816. Support for M.C. is provided by the Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica Milenio through grant P07-021-F, awarded to The Milky Way Millenium Nucleus; by Proyecto Basal PFB-06/2007; by FONDAP Centro de Astrofísica 15010003; and by proyecto FONDECYT Regular #1110326. The CRTS is supported in part by the NSF Grant AST-0909182. This research has made extensive use of the NASA/IPAC Extragalactic Database (NED) which is operated by the JPL, Caltech, under contract with NASA. This paper includes data gathered with the 6.5 m Magellan telescope at Las Campanas Observatory, Chile.|
|Subject Keywords:||galaxies: dwarf; supernovae: general; supernovae: individual (SN 2008jb)|
|Official Citation:||SN 2008jb: A "Lost" Core-collapse Supernova in a Star-forming Dwarf Galaxy at ~10 Mpc J. L. Prieto et al. 2012 ApJ 745 70|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||12 Apr 2012 21:23|
|Last Modified:||26 Dec 2012 15:02|
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