Massive stars as thermonuclear reactors and their explosions following core collapse

TL;DR

This paper reviews nuclear reactions in stars, their role in stellar evolution and supernova explosions, and discusses observational signatures of supernovae and their circumstellar environments.

Contribution

It provides a comprehensive overview of stellar nucleosynthesis, core-collapse processes, and the observational aspects of supernovae and their surrounding media.

Findings

Neutrino signals from supernovae can be predicted.

Circumstellar medium influences supernova ejecta dynamics.

Nuclear reaction rates determine stellar evolution stages.

Abstract

Nuclear reactions transform atomic nuclei inside stars. This is the process of stellar nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars are reviewed. How stars manage to burn their fuel so slowly most of the time are also considered. Stellar thermonuclear reactions involving protons in hydrostatic burning are discussed first. Then I discuss triple alpha reactions in the helium burning stage. Carbon and oxygen survive in red giant stars because of the nuclear structure of oxygen and neon. Further nuclear burning of carbon, neon, oxygen and silicon in quiescent conditions are discussed next. In the subsequent core-collapse phase, neutronization due to electron capture from the top of the Fermi sea in a degenerate core takes place. The expected signal of neutrinos from a nearby supernova is calculated. The supernova often explodes inside a dense circumstellar medium, which is established due to the progenitor star losing its outermost envelope in a stellar wind or mass transfer in a binary system. The nature of the circumstellar medium and the ejecta of the supernova and their dynamics are revealed by observations in the optical, IR, radio, and X-ray bands, and I discuss some of these observations and their interpretations.