HEAD Division Meeting 1999, April 1999
Session 36. SNRs and Isolated NS
Oral, Thursday, April 15, 1999, 8:30am-10:01am, Colonial Room

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[36.02] A Radioactivity Frontier for Supernova Chemistry

Donald D. Clayton (Clemson U.), Weihong Liu (ORNL)

Supernova radioactivity dominates light curves, gamma rays and high excitation. We show that the chemistry of dust condensation is also dominated by radioactivity. Dust normally is either C or oxides depending on whether C or O has greater abundance. Compton electrons dissociate the CO molecule in about one month, however, maintaining free atomic carbon at decreasing temperature. Our chemical model of SN1987A shows that linear C chains establish a near equilibrium between formation and destruction even when O > C. Isomerization to ringed carbon above n=24 atoms greatly reduces oxidation rates for them, enabling those rare seeds to grow to micron size during expansion time. In gas having C = O their abundances per C atom at 500d decline with C-atom number n as n-2/3 from N24/N(C) = 10-20 at n=24. The abundances are less if C < O, but final graphite sizes are not. Maximum number is near n=1015. Most carbon mass is in the largest graphite spheres, having mass fraction X=10-5 relative to C. This is comparable to the C mass fraction of micrometer SN graphite grains found in meteorites. The radiogenic 44Ca from 44Ti decay after C condensation establishes their supernova source. Their total opacity suffices to shift emission lines in 87A blueward after 500d and also emits significant infrared luminosity. Parallel kinetic rates determine trace isotopes in the meteoritic SN graphites. The chemistry is kinetic rather than thermal equilibrium and is made possible by radiodeactivation of the CO trap for C. The ejected CO mass is an inverse measure of the ejected {56}Ni mass. A new chemical astronomy of supernova solids depends in these ways on the SN radioactivity.

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