PACS spectroscopy of OH/IR stars

TL;DR

This paper presents initial modeling of PACS spectral data for the OH/IR star V669 Cas, highlighting the importance of combined dust and gas radiative transfer modeling to understand molecular emission lines.

Contribution

First modeling effort of PACS spectral scans for an OH/IR star using combined dust and gas radiative transfer techniques.

Findings

Water emission lines are highly sensitive to dust-to-gas ratio.

Consistent dust and gas modeling is essential for accurate interpretation.

PACS provides unprecedented spectral resolution for studying AGB star envelopes.

Abstract

Observations of high-excitation molecular emission lines can greatly increase our understanding of AGB winds, as they trace the innermost regions of the circumstellar envelope. The PACS spectrometer on-board the Herschel Space Telescope, provides for the first time the spectral resolution and sensitivity necessary to trace these lines. We report on the first modelling efforts of a PACS spectral scan for the OH/IR star V669 Cas. Central to our methodology is the consistent treatment of both dust and gas by using a line radiative transfer and a continuum radiative transfer code conjointly. Water emission lines are found to be extremely sensitive to the dust-to-gas ratio, emphasizing the need of consistent modelling for dust and gas.