Computer Science
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aipc..937..339d&link_type=abstract
SUPERNOVA 1987A: 20 YEARS AFTER: Supernovae and Gamma-Ray Bursters. AIP Conference Proceedings, Volume 937, pp. 339-343 (2007).
Computer Science
Supernovae, Spectroscopy And Spectrophotometry, Radiative Transfer, Scattering, Supernova Remnants
Scientific paper
Using the non-LTE model atmosphere code CMFGEN, augmented with a treatment of time-dependent terms in the statistical and radiative equilibrium equations, we investigate potential time-dependence effects during the first week after the explosion for a Type II supernova. Starting at 1.7 days after explosion, we evolve the SN ejecta over 5.1 days. Compared to an equivalent steady-state model at 6.8 days, the time-dependent model shows a systematic over-ionization above the photosphere, with helium partially- or fully-ionized. In the steady-state model, helium recombines to its neutral state at and above the photosphere. Correspondingly, while the continuum and nearly all line features are unaffected by the presence of time-dependent terms in the radiative transfer treatment, helium lines are predicted stronger and broader, by a factor of a few. Given that hydrogen is fully ionized in the ejecta in both models at such early times, we conclude that such time-dependence effects are not associated with the energy gain stemming from hydrogen recombination, and are thus not tied to Type II SN and their late time evolution. Time-dependence effects can, thus, arise exclusively from the slow recombination rate compared to the SN expansion rate, and we surmise that they operate in all SN ejecta, whatever their type, with a magnitude that remains to be determined.
Dessart Luc
Hillier Desmond John
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