Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...441..821l&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 441, no. 2, p. 821-829
Astronomy and Astrophysics
Astrophysics
12
Emission Spectra, Helium, Line Spectra, Stellar Envelopes, Stellar Models, Supernova 1987A, Data Reduction, Gamma Rays, Light Curve, Photoionization, Spectrum Analysis
Scientific paper
We model the evolution of the He I lines, especially He I 1.083 micrometers and He I 2.058 micrometers, from the envelope of SN 1987A during the first 3 yr after the explosion. The He I metastable 23S and 21S states are populated by fast electrons resulting from energy deposition by gamma rays and depopulated by electron collisions and two-photon decay. The 2.058 micrometer line is excited mainly by nonthermal electrons at all times. The 1.083 micrometer line is excited mainly by thermal electron impact for t less than or approximately = 450 days and by recombination afterward. We can fit the observed evolution of He I 2.058 micrometers with a model in which approximately 3 solar mass of nearly pure helium and approximately 11 solar mass of hydrogen mixed with primordial helium occupy the volume emitting most of the light (v less than or approximately = 2500 km/s). For t less than or approximately = 450 days, trace carbon in the inner part of the helium suppresses the He I 2.058 micrometer line by photoabsorbing He I lambda 584 and depopulating the 21 P0 state. The observed 1.08 micrometer line is a blend of He I 1.083 micrometers and (S I) 1.082 micrometers. We estimate that He I 1.083 micrometers contributes 40% of the observed flux for t less than or approximately = 550 days and approximately 60% thereafter.
Li Hongwei
McCray Richard
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