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Hot Plasmas in Supernova Remnants

Published online by Cambridge University Press:  30 March 2016

F. D. Kahn
F. D. Kahn*
Affiliation:
Department of Astronomy, University of Manchester

Extract

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Supernovae occur in highly evolved, massive stars and typically release 1051 to 1052 erg. Their light curves show that the stellar radius is about one A.U. at the time of the explosion. The typical energy density in the star is about 1011 or 1012erg cm-3 when the blast reaches the stellar surface. Much of the energy is present in thermal form. Since the density of the material is high, thermal equilibrium is attained rapidiy between the radiation field and the thermal motions. The temperature in the interior of the star becomes about 106K, and most of the energy is present in the form of radiation.

At this time the star has a large optical depth, of order 107. Therefore the effective diffusion speed for radiation is very low, about 3000 cm s-1. But the effective sound speed is large, of order 109 cm s-1, and the large input of energy has destroyed the gravitational equilibrium. So the star begins violently to expand, and the pressure of the stored radiation field does work in producing mass motion of the material. Only a small fraction of the radiant energy is released from the exploded star. The photosphere, in this phase, lies in the region where the gas changes from being ionized to non-ionized, so that the photo-spheric temperature remains low, of order 104K. There is little chance of observing any high-temperature phenomena at this stage in the evolution of a supernova.

Type
Joint Discussion
Information
Highlights of Astronomy , Volume 5: Highlights of Astronomy. As presented at the XVIIth General Assembly of the IAU, 1979 , 1980 , pp. 365 - 374
Copyright
Copyright © Cambridge University Press 1980

References

Comments and References

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The definition of the various phases in the development of a remnant is discussed by Woltjer, (op. cit.).Google Scholar
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The simple approximation to their calculated Л(Т) comes from Kahn, F.D., Astron. Astrophys. 50, 145, 1976.Google Scholar
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