The mass-loss characteristics of AGB stars An observational view

Abstract

AbstractThe massive outflows of gas and dust which characterize giant stars on the Asymptotic Giant Branch (AGB), build cool circumstellar envelopes readily observed at infrared (IR) and sub-millimeter wavelengths. The observations will give the amount of matter lost by the star, the wind velocity (in the case of spectral line observations), and, when the spatial resolution is sufficient, the wind evolution over time. To gain detailed insight into the mass-loss process, we study the nearby (closer than 1 kpc) stars. Through these investigations we aim to determine the best constrained wind properties available. By combining this with theoretical results, mass-loss estimates for more distant sources can also be significantly improved. ALMA has opened up new opportunities to study the winds of AGB stars. The DEATHSTAR project (www.astro.uu.se/deathstar) has mapped the circumstellar CO emission from so far ∼50 nearby M- and C-type AGB stars. The data will initially be used to give a definitive mass-loss prescription for the sample sources, but the large-bandwidth observations opens for many different legacy projects. The current status and results are presented.