English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We present submillimeter observations of rotational transitions of carbonmonoxide from J = 2 -> 1 up to 7 -> 6 for a sample of Asymptotic Giant Branchstars and red supergiants. It is the first time that the high transitions J = 6-> 5 and 7 -> 6 are included in such a study. With line radiative transfercalculations, we aim to determine the mass-loss history of these stars byfitting the CO line intensities. We find that the observed line intensities ofthe high transitions, including the J = 4 -> 3 transition, are significantlylower than the predicted values. We conclude that the physical structure of theoutflow of Asymptotic Giant Branch stars is more complex than previouslythought. In order to understand the observed line intensities and profiles, aphysical structure with a variable mass-loss rate and/or a gradient instochastic gas velocity is required. A case study of the AGB star WX Psc isperformed. We find that the CO line strengths may be explained by variations inmass-loss on time scales similar to those observed in the separated arc-likestructures observed around post-AGB stars. In addition, a gradient in thestochastic velocity may play a role. Until this has been sorted out fully, anymass loss determinations based upon single CO lines will remain suspect.

Mass loss and rotational CO emission from Asymptotic Giant Branch stars