Improved spectral line treatment and stellar atmospheric modelling for ChromaStarPy

Abstract

ChromaStarPy is a stellar atmosphere and spectrum modeling code written in python designed to give good approximations of stellar spectra, whilst being easily accessible to students at a wide range of levels. We present several projects including: 1) Incorporating a more accurate interpolation of temperature-dependent partition functions; 2) Fitting more realistic limb darkening curves to surface intensity distributions; and 3) Using a new model atom treatment for spectral lines. The new limb darkening curves are based on least-square fitting of linear and quadratic limb darkening laws to the surface intensity distribution separately at each wavelength, and for the Johnson-Bessel filters. In doing so more accurate limb darkening coefficients (LDCs) are produced. The improved partition function treatment is based on fitting a cubic interpolation function to the variation with temperature and produces smooth variations of number densities of elements in each ionization stage with depth. The new model atom treatment allows us to improve the treatment of natural line broadening, producing line profiles that are closer to the observed line width.