Spectral analysis of the secondary in the AA Dor system with PHOENIX/3D
Final Report Abstract
In this project we have created 3D radiative transfer models of the cool companion star in the close binary system AA Dor. The main component, a white dwarf with an effective temperature of 42 000 K, strongly irradiates the very low-mass companion, which causes its atmosphere to massively heat up on the day side, while the night side remains very cool (the rotation of the companion is synchronized with the orbital period by tidal forces). A number of PHOENIX/1D models with and without external irradiation were patched together into a 3D structure, resulting in ”1.5D models”. The resulting hydrostatic structures are used to run irradiated PHOENIX/3D models. With the PHOENIX/1D models, a slight atmosphere expansion due to local heating was found. Both 1.5D and 3D models were able to reproduce different observer perspectives. Limits for the 1.5D models were found near the terminator regions where 1D models fail to process the irradiation under low incident angles due to a lack of horizontal interactions. However, the 3D models are able to account for this and thus, transmission features at the limb of the nightside were found.
