A Spiral Goes Viral: Observations and Modeling of the Circumstellar Envelope around R Sculptoris

Paper in proceeding, 2015

The complex circumstellar envelope (CSE) around the carbon-rich asymptotic giant branch (AGB) star R Sculptoris has been observed with ALMA, revealing a remarkable and up to now unique geometry, consisting of a thin, spherically symmetric detached shell enclosing a spiral structure. By comparing ALMA data in three different spectral bands - covering different excitation states of the CO molecule - the gas structure and mass-loss evolution of this object can be analyzed. A morphological comparison between molecular line data (ALMA) and dust images (Herschel/PACS) gives hints to the spatial distribution of both constituents of the circumstellar envelope, as well as interaction processes between the different media. Dust continuum radiative transfer modeling of the detached shell around R Scl allows us to constrain the dust parameters and delivers spectral energy distributions comparable to observations.