The light of the supernova outburst. III. External excitation of the expanding gas shell.
Abstract
The fluorescence-reverberation model for late spectra of Type I supernovae (SN I) has been extended to identify and describe the time evolution of all the major lines in the spectra. Forbidden-line emission is shown to be a highly significant component of late SN I spectra. A unified picture of SN I optical behavior from the earliest times on is offered. The model includes three related sources of optical light: (1) the expanding gas shell, which dominates the early spectra by its blackbody continuum emission (with a few absorption lines) but rapidly decays, (2) the fluorescent circumstellar medium that gives rise to the strong long-lasting lines of He II, and (3) the protracted reexcitation of the cooled outermost layer of the gas shell by the distant fluorescent decay, to produce forbidden lines. More than 95% of all the spectra from UV to near-IR is thus naturally explained by intensities, time course, and variable Doppler shifts and widths. No energy source is needed beyond the prompt explosion (which must include a UV or soft X-ray pulse of 10 to the 52nd ergs total energy).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1978
- DOI:
- 10.1086/155994
- Bibcode:
- 1978ApJ...220.1087A
- Keywords:
-
- Fluorescence;
- Gas Expansion;
- Light Emission;
- Stellar Models;
- Stellar Spectra;
- Supernovae;
- Doppler Effect;
- Forbidden Transitions;
- Line Spectra;
- Spectral Line Width;
- Astrophysics;
- Forbidden Lines:Supernovae;
- Spectra:Supernovae;
- Supernovae: Outbursts