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

Context. AGB stars go through a process of strong mass-loss that involvespulsations of the atmosphere, which extends to a region where the conditionsare adequate for dust grains to form. Radiation pressure acts on these grainswhich, coupled to the gas, drive a massive outflow. The details of this processare not clear, including which molecules are involved in the condensation ofdust grains.  Aims. To study the role of the SiO molecule in the process of dust formationand mass-loss in M-type AGB stars.  Methods. Using the IRAM NOEMA interferometer we observed the $^{28}$SiO and$^{29}$SiO $J=3-2$, $v=0$ emission from the inner circumstellar envelope of theevolved stars IK Tau and IRC+10011. We computed azimuthally averaged emissionprofiles to compare the observations to models using a molecular excitation andray-tracing code for SiO thermal emission.  Results. We observed circular symmetry in the emission distribution. We alsofound that the source diameter varies only marginally with radial velocity,which is not the expected behavior for envelopes expanding at an almostconstant velocity. The adopted density, velocity, and abundance laws, togetherwith the mass-loss rate, which best fit the observations, give us informationon the chemical behavior of the SiO molecule and its role in the dust formationprocess.  Conclusions. The results indicate that there is a strong coupling between thedepletion of gas phase SiO and gas acceleration in the inner envelope. Thiscould be explained by the condensation of SiO into dust grains.

Interferometric observations of SiO thermal emission in the inner wind of M-type AGB stars IK Tauri and IRC+10011