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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

An extensive radiative transfer analysis of circumstellar SiO `thermal' radioline emission from a large sample of M-type AGB stars has been performed. Thesample contains 18 irregulars of type Lb (IRV), 7 and 34 semiregulars of typeSRa and SRb (SRV), respectively, and 12 Miras. New observational material,which contains data in several SiO rotational lines in the ground vibrationalstate, is presented for the IRV/SRVs. The detection rate was about 60%. SiOfractional abundances have been determined through radiative transfermodelling. The abundance distribution of the IRV/SRV sample has a median valueof 8E-6. The high mass loss rate Miras have a bimodal abundance distribution, alow abundance group (on average 4E-7) and a high abundance group (on average7E-6). The derived SiO abundances are in all cases well below the abundanceexpected from stellar atmosphere chemistry, on average by a factor of ten. Inaddition, there is a trend of decreasing SiO abundance with increasing massloss rate. This is interpreted in terms of depletion of SiO molecules by theformation of silicate grains in the circumstellar envelopes, with an efficiencywhich increases with the mass loss rate. The SiO and CO radio line profilesdiffer in shape. In general, the dominating part of the SiO profiles arenarrower than the CO profiles, but they have low-intensity wings which coverthe full velocity range of the CO profile. This is interpreted (as has beendone also by others) as due to the influence of gas acceleration in the regionwhich produces a significant fraction of the SiO line emission. Finally, anumber of sources which have peculiar CO line profiles are discussed from thepoint of view of their SiO line properties.Comment: 25 pages, 13 figures, A&A in pres

“Thermal” SiO radio line emission towards M-type AGB stars: A probe of circumstellar dust formation and dynamics