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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 Hoeflich
; Duncan Farrah
; Alexei V. Filippenko
; Ryan J. Foley
; Peter Lundqvist
; Seppo Mattila
; Monica Pozzo
; Jesper Sollerman
; Schuyler D. Van Dyk
; J. Craig Wheeler
; | | Date: |
5 Feb 2007 | | Abstract: | We present the first mid-infrared (5.2-15.2 micron) spectra of Type Ia supernovae (SNe 2003hv and 2005df). 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 Type Ia supernova. The observed emission line profiles in the SN 2005df spectrum indicate a chemically stratified ejecta structure. 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 NIR spectra. Finally, local thermodynamic equilibrium abundance estimates for the yield of radioactive 56Ni give ~0.5 Msun, for SN 2003hv, but only ~0.13-0.22 Msun for the apparently subluminous SN 2005df, supporting the notion that the luminosity of SNe Ia is primarily a function of the radioactive 56Ni yield.
The chemically stratified ejecta structure observed in SN 2005df 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. | | Source: | arXiv, astro-ph/0702117 | | Services: | Forum | Review | PDF | Favorites | |
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