Abstract
We present near-infrared (NIR) spectra for Type la supernovae at epochs of 13 to 338 d after maximum blue light. Some contemporary optical spectra are also shown. All the NIR spectra exhibit considerable structure throughout the J, H and K bands. In particular, they exhibit a flux 'deficit' in the J band which persists as late as 175 d. This is responsible for the well-known red J-H colour. To identify the emission features and test the 56Ni hypothesis for the explosion and subsequent light curve, we compare the NIR and optical nebular-phase data with a simple non-LTE nebular spectral model. We find that many of the spectral features are due to iron-group elements, and that the J-band deficit is due to a lack of emission lines from species that dominate the rest of the IR/optical spectrum. Nevertheless, some emission is unaccounted for, possibly due to inaccuracies in the cobalt atomic data. For some supernovae, blueshifts of 1000-3000 km s-1 are seen in infrared and optical features at 3 months. We suggest that this is due to clumping in the ejecta. The evolution of the cobalt/iron mass ratio indicates that 56Co-decay dominates the abundances of these elements. The absolute masses of iron-group elements which we derive support the basic thermonuclear explosion scenario for Type la supernovae. A core-collapse origin is less consistent with our data.
Original language | English (US) |
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Pages (from-to) | 663-679 |
Number of pages | 17 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 290 |
Issue number | 4 |
DOIs | |
State | Published - 1997 |
Keywords
- Infrared: stars
- Stars: general
- Supernovae: general
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science