Extended far-UV emission surrounding asymptotic giant branch stars as seen by GALEX

Abstract

Aims. Our goal is to study the long-term mass-loss rate characteristics of asymptotic giant branch (AGB) stars through wind-wind and wind-interstellar medium interaction. Methods. Far-ultraviolet (FUV) images from the GALEX survey are used to investigate extended UV emission associated with AGB stars. Results. FUV emission was found towards eight objects. The emission displays different shapes and sizes; interaction regions were identified, often with infrared counterparts, but no equivalent near-ultraviolet (NUV) emission was found in most cases. Conclusions. The FUV emission is likely attributed to shock-excited molecular hydrogen, considering the lack of NUV emission and the large space velocities of the objects, and makes it possible to trace old structures that are too faint to be observed, for instance, in the infrared.