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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

CONTEXT: Asymptotic giant branch (AGB) stars are in one of the latestevolutionary stages of low to intermediate-mass stars. Their vigorous mass losshas a significant effect on the stellar evolution, and is a significant sourceof heavy elements and dust grains for the interstellar medium. The mass-lossrate can be well traced by carbon monoxide (CO) line emission.  AIMS: We present new Herschel HIFI and IRAM 30m telescope CO line data for asample of 53 galactic AGB stars. The lines cover a fairly large range ofexcitation energy from the $J=1\to0$ line to the $J=9\to8$ line, and even the$J=14\to13$ line in a few cases. We perform radiative transfer modelling for 38of these sources to estimate their mass-loss rates.  METHODS: We used a radiative transfer code based on the Monte Carlo method tomodel the CO line emission. We assume spherically symmetric circumstellarenvelopes that are formed by a constant mass-loss rate through a smoothlyaccelerating wind.  RESULTS: We find models that are consistent across a broad range of CO linesfor most of the stars in our sample, i.e., a large number of the circumstellarenvelopes can be described with a constant mass-loss rate. We also find that anaccelerating wind is required to fit, in particular, the higher-J lines andthat a velocity law will have a significant effect on the model lineintensities. The results cover a wide range of mass-loss rates ($\sim 10^{-8}$to $2\times 10^{-5}~\mathrm{M}_\odot~\mathrm{ yr}^{-1}$) and gas expansionvelocities (2 to $21.5$ km s$^{-1}$), and include M-, S-, and C-type AGB stars.Our results generally agree with those of earlier studies, although we tend tofind slightly lower mass-loss rates by about 40%, on average. We also present"bonus" lines detected during our CO observations.

New observations and models of circumstellar CO line emission of AGB stars in the Herschel SUCCESS programme