Radio and IR interferometry of SiO maser stars

TL;DR

This paper combines radio and infrared interferometry to study the atmospheres and dust regions of SiO maser stars, revealing new insights into their structure, variability, and the physical processes driving maser emissions.

Contribution

It presents new combined infrared and radio interferometric observations of AGB stars, offering detailed insights into their atmospheric structure and maser emission regions.

Findings

Infrared and radio interferometry reveal the atmospheric and dust structures of AGB stars.

Monitoring high-frequency SiO maser emission shows erratic variability and deviations from symmetry.

Preliminary ALMA images are anticipated from ongoing observations.

Abstract

Radio and infrared interferometry of SiO maser stars provide complementary information on the atmosphere and circumstellar environment at comparable spatial resolution. Here, we present the latest results on the atmospheric structure and the dust condensation region of AGB stars based on our recent infrared spectro-interferometric observations, which represent the environment of SiO masers. We discuss, as an example, new results from simultaneous VLTI and VLBA observations of the Mira variable AGB star R Cnc, including VLTI near- and mid-infrared interferometry, as well as VLBA observations of the SiO maser emission toward this source. We present preliminary results from a monitoring campaign of high-frequency SiO maser emission toward evolved stars obtained with the APEX telescope, which also serves as a precursor of ALMA images of the SiO emitting region. We speculate that large-scale long-period chaotic motion in the extended molecular atmosphere may be the physical reason for observed deviations from point symmetry of atmospheric molecular layers, and for the observed erratic variability of high-frequency SiO maser emission