A HIFI View of Circumstellar H_2O Emission from the S-type AGB Star χ Cyg

摘要

Accurate modelling of sensitive, and spectrally resolved, observations of H_2O emisison lines is important for understanding the physics and chemistry of circumstellar envelopes around AGB stars. We present detailed non-local, non-LTE models of H_2O emission lines observed towards the S-type AGB star χ Cyg with the HIFI instrument onboard Herschel. The models demonstrate the ability to constrain important physical and chemical parameters in the inner CSE close to the central star, emphasizing the importance of high-quality data from HIFI combined with detailed radiative transfer models.