Infrared and optical spectroscopy of Type Ia supernovae in the nebular phase

E. J C Bowers, W. P S Meikle, T. R. Geballe, N. A. Walton, Philip A Pinto, V. S. Dhillon, S. B. Howell, M. K. Harrop-Allin

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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 languageEnglish (US)
Pages (from-to)663-679
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume290
Issue number4
Publication statusPublished - 1997

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Keywords

  • Infrared: stars
  • Stars: general
  • Supernovae: general

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Bowers, E. J. C., Meikle, W. P. S., Geballe, T. R., Walton, N. A., Pinto, P. A., Dhillon, V. S., ... Harrop-Allin, M. K. (1997). Infrared and optical spectroscopy of Type Ia supernovae in the nebular phase. Monthly Notices of the Royal Astronomical Society, 290(4), 663-679.