Stellar Collapse and Supernova Explosions

Abstract

18.1 Introduction and Warning No treatment of compact objects would be complete without some discussion of supernovae. As we have already described in Sections 9.1 and 10.1, it came as no surprise to some when the Crab and Vela pulsars were discovered in supernova remnants. Ever since Baade and Zwicky (1934) had shown that the gravitational energy released by the collapse of an evolved stellar core to a neutron star would be more than adequate to power observed supernova outbursts, many researchers regarded collapse and supernova explosions to be events intimately associated with neutron star (and, possibly, black hole) formation. There is by now a wealth of " circumstantial " evidence linking the birth of neutron stars to collapse and supernova explosions. Evolutionary calculations of nonrotating stars with masses in the range 10 5 M/M, 5 70 all exhibit the development of an unstable core, containing roughly lSM, of iron, wluch undergoes dynamical collapse.' Optical, radio, and X-ray observations of the expanding gas comprising " Type 11 " supernova remnants are nicely accounted for by assuming that these massive stars are disrupted following an explosion within the core.2 For example, explosive nucleosynthesis in a massive star can explain the abundances of elements between oxygen and iron peak elements3 as well as the neutron-rich (" r-process ") elements. The element abundances in the 'Amett (1977a); Barkat (1977); Weaver, Zimmerman, and Woosley (1978). *Supernovae are divided into two types by observers. We shall only be concerned in this chapter with Type I1 supemovae, which are believed to result from collapse of massive stars M 2 8Mo. Type 1 supernovae are currently believed to result from the complete explosion of the degenerate core of a star of mass 4 5 M 5 8M,, leaving essentially no remnant. 'Amett (1978); Weaver and Woosley (1980).