SN 2008jb: A 'LOST' CORE-COLLAPSE SUPERNOVA IN A STAR-FORMING DWARF GALAXY AT {approx}10 Mpc
- Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- California Institute of Technology, 1200 E. California Blvd., CA 91225 (United States)
- Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia)
- Department of Physics, The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210 (United States)
- Department of Planetary Sciences, Lunar and Planetary Laboratory, The University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721 (United States)
- Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Av. Vicuna Mackena 4860, 782-0436 Macul, Santiago (Chile)
- Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warsaw (Poland)
- Department of Astronomy, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States)
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{sub 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{sub max} {approx_equal} 13.6 mag (M{sub V,max} {approx_equal} -16.5). The shape of the light curve shows a plateau of {approx}100 days, followed by a drop of {approx}1.4 mag in the V band to a slow decline with an approximate {sup 56}Co decay slope. The late-time light curve is consistent with 0.04 {+-} 0.01 M{sub Sun} of {sup 56}Ni synthesized in the explosion. A spectrum of the supernova obtained two years after explosion shows a broad, boxy H{alpha} 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 ({approx}1/5 Z{sub Sun }), 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 ({approx}< 10 Mpc) supernova hosts. We study the host environment using GALEX far-UV, R-band, and H{alpha} images and find that the supernova occurred in a large star formation complex. The morphology of the H{alpha} emission appears as a large shell (R {approx_equal} 350 pc) surrounding the FUV and optical emission. Using the H{alpha}-to-FUV ratio and FUV and R-band luminosities, we estimate an age of {approx}9 Myr and a total mass of {approx}2 Multiplication-Sign 10{sup 5} M{sub Sun} for the star formation complex, assuming a single-age starburst. These properties are consistent with the expanding H{alpha} 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 {approx} 20 M{sub Sun} and warrants further study. We discuss the implications of these findings in the study of core-collapse supernova progenitors.
- OSTI ID:
- 22011968
- Journal Information:
- Astrophysical Journal, Vol. 745, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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