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, P. A. Pinto, V. S. Dhillon, S. B. Howell, M. K. Harrop-Allin

Research output: Contribution to journalArticle

59 Scopus citations

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
DOIs
StatePublished - Jan 1 1997

Keywords

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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Bowers, E. J. C., Meikle, W. P. S., Geballe, T. R., Walton, N. A., Pinto, P. A., Dhillon, V. S., Howell, S. B., & 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. https://doi.org/10.1093/mnras/290.4.663