Signatures of Delayed Detonation, Asymmetry, and Electron Capture in the Mid-Infrared Spectra of Supernovae 2003hv and 2005df

June 2007 • 2007ApJ...661..995G

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

Abstract • 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 ⁵⁶Ni give M_⁵⁶Ni~0.5 M_solar, for SN 2003hv, but only M_⁵⁶Ni~0.13-0.22 M_solar 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 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.

Links

• PREPRINT http://arxiv.org/abs/astro-ph/0702117
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2007ApJ...661..995G
• ELECTR https://doi.org/10.1086%2F516728
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2007ApJ...661..995G
• PDF https://stacks.iop.org/0004-637X/661/995/pdf
• DATA https://irsa.ipac.caltech.edu/bibdata/2007/G/2007ApJ...661..995G.html
• SPIRES http://inspirehep.net/search?p=find+eprint+astro-ph/0702117