Computer Science
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........83l&link_type=abstract
Thesis (PH.D.)--NEW YORK UNIVERSITY, 1992.Source: Dissertation Abstracts International, Volume: 53-03, Section: B, page: 1414.
Computer Science
Scientific paper
About 163,000 years ago, the core of blue supergiant star Sanduleak-69^circ202 in the Large Magellanic Cloud collapsed and the star exploded to become SN1987A, the neutrinos and photons from which were detected on February 23, 1987. The HeI(1.0830 μm) line was observed in SN1987A early as a P-Cygni profile. The recombination of He^+ ions produced by fast electron impact is mainly responsible for populating the helium metastable states, the abundances of which are calculated. The line profile of the transition HeI(2 ^3S-2^3P^0) is constructed. In comparison with the observed spectrum at 135 days, 10% of the energy released by the radioactive species in SN1987A is deposited in the He gas. The detection of CO and SiO provides the first evidence of molecular formation in supernova ejecta. I explore the molecular formation and destruction mechanisms in SN1987A to determine the molecular abundances. The CO masses are derived using the first overtone emission band at 2.3 μm observed during the first year. It is found that the Deltav = 2 line of CO in SN1987A is optically thick at early times and that the vibrational level populations fall out of thermal equilibrium at later times. A careful interpretation of the observational data allowing departure from LTE and allowing optical depth effects yields the order of 10 ^{-3}M_odot of CO in SN1987A. The mixed chemistry is inefficient in producing CO and fails to account for the observed abundances of CO by three orders of magnitude whereas the unmixed chemistry predicts the order of 10^{ -2}M_odot of CO. Thus the CO masses implied from the observations can be reproduced by assuming that the regions without microscopic mixing occupy 10% of the ejecta. The chemistry predicts that SiO is substantially more abundant than that derived from its fundamental band assuming LTE. As for CO, departures from LTE and optical depth effects may have led to a severe underestimate of the SiO abundance. In the first year, a weak feature at 1.334 μm is tentatively attributed to the fundamental band of SiS, whose mass in SN1987A is predicted as about 10^{-7}M_ odot..
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