The Lightweaver Framework for Nonlocal Thermal Equilibrium Radiative Transfer in Python

Abstract

Abstract Tools for computing detailed optically thick spectral line profiles out of local thermodynamic equilibrium have always been focused on speed, due to the large computational effort involved. With the Lightweaver framework, we have produced a more flexible, modular toolkit for building custom tools in a high-level language, Python, without sacrificing speed against the current state of the art. The goal of providing a more flexible method for constructing these complex simulations is to decrease the barrier to entry and allow more rapid exploration of the field. In this paper we present an overview of the theory of optically thick nonlocal thermodynamic equilibrium radiative transfer, the numerical methods implemented in Lightweaver including the problems of time-dependent populations and charge-conservation, as well as an overview of the components most users will interact with, to demonstrate their flexibility.