Signatures of delayed detonation, asymmetry, and electron capture in the mid-infrared spectra of supernovae 2003hv and 2005df

Christopher L. Gerardy, W. P.S. Meikle, Rubina Kotak, Peter Höflich, Duncan Farrah, Alexei V. Filippenko, Ryan J. Foley, Peter Lundqvist, Seppo Mattila, Monica Pozzo, Jesper Sollerman, Schuyler D. Van Dyk, J. Craig Wheeler

Research output: Contribution to journalArticlepeer-review


We present mid-infrared (5.2-15.2 μm) spectra of the Type la supernovae (SNe la) 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 56Ni give M56NiNi ≈ 0.5 M, for SN 2003hv, but only M56Ni ≈ 0.13-0.22 M for the apparently subluminous SN 2005df, supporting the notion that the luminosity of SNe la is primarily a function of the radioactive 56Ni 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.

Original languageEnglish (US)
Pages (from-to)995-1012
Number of pages18
JournalAstrophysical Journal
Issue number2 I
StatePublished - Jun 1 2007


  • Supernovae: general
  • Supernovae: individual (SN 2003hv, SN 2005df)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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