The Evolution of Ultraviolet Emission Lines From Circumstellar Material Surrounding SN 1987A
Kirshner, Robert P.
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CitationSonneborn, George, Claes Fransson, Peter Lundqvist, Angelo Cassatella, Roberto Gilmozzi, Robert P. Kirshner, Nino Panagia, and Willem Wamsteker. 1997. “The Evolution of Ultraviolet Emission Lines From Circumstellar Material Surrounding SN 1987A.” The Astrophysical Journal 477 (2): 848–64. https://doi.org/10.1086/303720.
AbstractThe presence of narrow high-temperature emission lines from nitrogen-rich gas close to SN 1987A has been a principal observational constraint on the evolutionary status of the supernova's progenitor. A new analysis of the complete 5 year set of low- and high-resolution IUE ultraviolet spectra of SN 1987A (1987.2-1992.3) provides fluxes for the N V lambda 1240, N IV] lambda 1486, He II lambda 1640, O III] lambda 1665, N III] lambda 1751, and C III] lambda 1908 lines with significantly reduced random and systematic errors and reveals significant short-term fluctuations in the light curves. The N V N IV], and N III] lines turn on sequentially over 15-20 days and show a progression from high to low ionization potential, implying an ionization gradient in the emitting region. The line emission turns on suddenly at 83+/-4 days after the explosion, as defined by N IV]. The N III] line reaches peak luminosity at 399+/-15 days. A ring radius of (6.24+/-0.20)x10(17) cm and inclination of 41 degrees.0+/-3 degrees.9 is derived from these times, assuming a circular ring. The probable role of resonant scattering in the N V light curve introduces systematic errors that leads us to exclude this line from the timing analysis. A new nebular analysis yields improved CNO abundance ratios of N/C=6.1+/-1.1 and N/O=1.7+/-0.5, confirming the nitrogen enrichment found in our previous paper. From the late-time behavior of the light curves we find that the emission originates from progressively lower density gas and that the emitting region has a multicomponent density structure. We estimate the emitting mass near maximum (similar to 400 days) to be similar to 4.7x10(-2) M., assuming a filling factor of unity and an electron density of 2.6x10(4) cm(-3). These results are discussed in the context of current models for the emission and hydrodynamics of the ring.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41399821
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