White dwarf model atmospheres

Due to the extremes of temperatures/densities in their outer layers, white dwarfs serve as excellent probes of physical conditions which cannot be recreated in Earth-based laboratories. For white dwarfs (and all types of stars), these conditions are revealed by obtaining spectroscopic measurements, in essence the amount of light emitted by the star at each wavelength. To understand these complicated spectra, astronomers must construct models taking into account the constituent physics and all relevant atomic/molecular data.

In the most cases, the effective temperature, surface gravity, and chemical composition can be used to uniquely define an atmospheric model, thus serving as inputs to the model codes. The calculated spectra can then be compared with the observed spectra with refinements made to the inputs until a match is found.

I mostly work with the Koester white dwarf model atmospheres, which are versatile enough to be able to model a wide range of white dwarfs types. Within my own research, I have put these models to use for the analysis of:

• metal-rich white dwarfs
• ultra-massive white dwarfs that have survived double white merger
• extremely low mass white dwarfs
• ultracool white dwarfs
• shrapnel from white dwarf supernovae