The detached dust shells of AQ Andromedae, U Antliae, and TT Cygni

摘要

Detached circumstellar dust shells are detected around three carbon variables using Herschel-PACS.Two of them are already known on the basis of their thermalCOemission and two are visible as extensions in IRAS imagingdata. By model fits to the new data sets, physical sizes, expansiontimescales, dust temperatures, and more are deduced. A comparison withexisting molecular COmaterial shows a high degree of correlationfor TTCyg and UAnt but a few distinct differenceswith other observables are also found.Key words: stars: AGB and post-AGB - stars: carbon - stars: evolution - stars: mass-loss - infrared: stars