Speaker
Description
Spatially resolved observations have shown that AGB stars are frequently accompanied by spiral dust rings. These observed structures have been reproduced with hydrodynamical (HD) models by introducing a secondary star into the system. However, for almost all of the observed AGB stars with spiral structures we are lacking constrained binary parameters such as the secondary mass, inclination, position angle, etc. Previous spectral studies on these type of stars have been performed but usually assume spherical symmetry. This overlooks the asymmetry in the abundance profiles caused by the binary and does not address the spiral structure surrounding these stars.
We perform detailed 3D radiative transfer on full 3D HD models and fit the resulting spectra to spatially resolved ALMA observations of CO, 13CO, SiC, ans SiS spectral lines. As the spiral is computed self-consistently in the HD model, the spatially integrated spectral lines give us limits on the inclination and position angle of the system. Moreover, by fitting the spectral data of different spatially resolved subregions we can get a full 3D map of the molecular abundance. The presence or absence of certain molecules indicates the UV emission of the secondary, strongly constraining the type (main sequence, red/white dwarf) and mass of the secondary. We will show the results of this highly in-depth radiative transfer modelling on the binary AGB-star AFGL 3068.