Gerardy, Christopher L. and Meikle, W. P. S. and Kotak, Rubina and Höflich, Peter and Farrah, Duncan and Filippenko, Alexei V. and Foley, Ryan J. and Lundqvist, Peter and Mattila, Seppo and Pozzo, Monica and Sollerman, Jesper and Van Dyk, Schuyler D. and Wheeler, J. Craig (2007) Signatures of delayed detonation, asymmetry, and electron capture in the mid-infrared spectra of supernovae 2003hv and 2005df. Astrophysical Journal, 661 (2). pp. 995-1012. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:GERapj07
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We present mid-infrared (5.2-15.2 μm) spectra of the Type Ia supernovae (SNe Ia) 2003hv and 2005df observed with the Spitzer Space Telescope. These are the first observed mid-infrared spectra of thermonuclear supernovae, and show strong emission from fine-structure lines of Ni, Co, S, and Ar. The detection of Ni emission in SN 2005df 135 days after the explosion provides direct observational evidence of high-density nuclear burning forming a significant amount of stable Ni in a SN Ia. The SN 2005df Ar lines also exhibit a two-pronged emission profile, implying that the Ar emission deviates significantly from spherical symmetry. The spectrum of SN 2003hv also shows signs of asymmetry, exhibiting blueshifted [Co III], which matches the blueshift of [Fe II ] lines in nearly coeval near-infrared spectra. Finally, local thermodynamic equilibrium abundance estimates for the yield of radioactive ^(56)Ni give M^(56)Ni ≈ 0.5 M⊙, for SN 2003hv, but only M^(56)Ni ≈ 0.13-0.22 M⊙ for the apparently subluminous SN 2005df, supporting the notion that the luminosity of SNe Ia is primarily a function of the radioactive ^(56)Ni yield. The observed emission-line profiles in the SN 2005df spectrum indicate a chemically stratified ejecta structure, which matches the predictions of delayed detonation (DD) models, but is entirely incompatible with current three-dimensional deflagration models. Furthermore, the degree that this layering persists to the innermost regions of the supernova is difficult to explain even in a DD scenario, where the innermost ejecta are still the product of deflagration burning. Thus, while these results are roughly consistent with a delayed detonation, it is clear that a key piece of physics is still missing from our understanding of the earliest phases of SN Ia explosions.
|Additional Information:||© 2007 The American Astronomical Society. Received 2006 September 22; accepted 2007 February 2. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Financial support for the research is provided by NASA Spitzer grant GO-20256. C. L. G. is grateful for UK PPARC grant PPA/G/S/2003/00040. J. C. W. is supported through NSF grant AST 04-06740. S. M. acknowledges financial support from the European Heads of Research Councils and European Science Foundation EURYI Awards scheme.|
|Subject Keywords:||supernovae: general; supernovae: individual (SN 2003hv, SN 2005df)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||09 Jul 2009 18:14|
|Last Modified:||26 Dec 2012 10:54|
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