The Hubble constant, supernova light curves and spectra, and radiation transport

As luminous events that can be physically modeled, supernovae provide an attractive route to the value of the Hubble constant. The modeling involves radiation transport through matter undergoing homologous expansion with velocity gradient on the order of 10−6 s−1. For supernovae of type Ia, which are thermonuclear disruptions of mass accreting or coalescing carbon–oxygen white dwarfs, one wants to be able to calculate the light curve (luminosity in some optical passband versus time), which is powered by the radioactivity decay chain Ni56→Co56→Fe56. For all kinds of supernovae, including those of types II, Ib, and Ic, which result from the gravitational collapse of the cores of massive stars, the goal is to accurately calculate the emergent ultraviolet–optical–infrared spectra, as a function of time. Local-thermodynamic-equilibrium (LTE) light-curve calculations for type Ia supernovae by Höflich and co-workers, and our spectrum calculations based on a fully relativistic non-LTE radiative transfer code, are described. The associated radiative transport needs are discussed.