Other
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...9e..19g&link_type=abstract
Supernovae: One Millennium After SN1006, 26th meeting of the IAU, Joint Discussion 9, 17-18 August 2006, Prague, Czech Republic,
Other
Scientific paper
Infrared spectroscopy is a powerful new tool which is yielding unique new insights into the physics of thermonuclear (Type Ia) supernovae. Photospheric era near-infrared (NIR) specta are less hampered by line-blending than optical spectra, allowing for the direct measurement of the kinematic distribution of chemical species in the ejecta. Results indicate a highly layered chemical structure and are roughly in line with the predictions of Delayed-Detonation (DD) models of SNe Ia. Late-time (200 d+) NIR spectra of SNe Ia are dominated by relatively strong but optically thin [Fe II] lines, which can trace out the global distribution of radioactive ejecta. Preliminary results suggest that many (perhaps most) SNe Ia show bulk offsets in the [Fe II] features of up to ~2500 km/s. Such shifts in the kinematic distribution of radioactive ejecta might be the signature of off-center detonations. Late time NIR spectra also show that at least some SNe Ia exhibit boxy [Fe II] line profiles, indicative of a central hole in the radioactive ejecta. Such profiles can be explained as the result of high-density nuclear burning creating stable Ni and Fe in the earliest burning phases. This interpretation is supported by the discovery of significant emission from stable Ni in mid-IR spectra obtained by the MISC collaboration with the Spitzer Space Telescope. The appearance of such boxy Fe profiles likely requires a small but non-zero magnetic field in the ejecta, which may also help to explain the appearance of apparent axisymmetric emission from Ar lines in the mid-IR spectrum of SN 2005df. Near and Mid-IR spectra generally suggest little large-scale mixing in the ejecta, in apparent contradiction of the predictions of 3D deflagration models. This presents a problem not only for pure deflagrations, but also for DD models, and suggests either that a fundamental effect is missing from deflagration models, or that something other than deflagration burning is pre-expanding the white dwarf prior to a detonation.
Gerardy Christopher L.
Hoeflich Peter Alexander
Kotak Rubina
Meikle Peter S. W.
Motohara Ken-taro
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