The Nearby Evolved Stars Survey

Low-to intermediate-mass stars (0.8-8 M⊙) evolve into asymptotic giant branch (AGB) stars, and are the major contributors to the chemical enrichment of the ISM in our Galaxy. Ongoing work in the AGB star community has made great progress in understanding these objects via modeling but comparative studies of the circumstellar environments of large samples of AGB stars have started only recently. These objects are known to have high mass-loss rates and studies of this mass loss provides an insight on the chemical evolution of the Galaxy, the evolution into planetary nebulae and further evolution into white dwarfs.

The Nearby Evolved Stars Survey (NESS) is a multi-telescope project targeting a volume limited sample of AGB stars (up to a distance of 3 kpc) in order to derive the dust and gas return rates from such objects in the Solar Neighbourhood, and also to constrain the physics underlying these processes. In this talk, I will present initial NESS results, derived from observations conducted with APEX and the IRAM 30m telescope, supplemented by archival data from other single-dish telescopes. Our analysis comprises of 445 stars as part of this collaboration. We observed the CO (1–0), CO (2–1), and CO (3–2) spectral lines, which serve as important tracers for regions of varying temperatures within the envelope, providing constraints into its structure. In this discussion, I will explore the statistical distributions of the derived stellar parameters and present preliminary constraints on the mass-loss rates of the observed objects. The findings from this study demonstrate how the statistical analysis of a stellar population confirms and extends our understanding of its contribution to the cosmic cycle of matter.