Speaker
Description
Circumstellar shells are a key manifestation of the mass-loss processes of evolved stars in the radio band. These faint and compact ring-like structures---from planetary nebulae around low- and intermediate-mass stars to the ejecta surrounding the more massive Luminous Blue Variables and Wolf-Rayets---are the result of the interplay between stellar winds and eruptions and the surrounding ISM. Therefore, the detection and analysis of these shells is crucial to understanding stellar evolution and feedback at Galactic scales. Until now, however, systematic, large-scale searches for ring-like structures in the radio have been hampered by the limited resolution and sensitivity of past continuum surveys.
In this context, the advent of SKA precursors has opened a new window for discovery, rapidly overcoming these limitations. Instruments such as ASKAP and MeerKAT now survey vast areas of the sky with unprecedented sensitivities (tens of $\mu$Jy beam$^{-1}$) and angular resolutions approaching those of optical and infrared surveys. These enhanced imaging capabilities are paving the way for a new era in the study of evolved stars at radio wavelengths, enabling both more accurate characterisation of known objects and the discovery of previously undetected populations.
This talk will review recent discoveries of circumstellar ring-like structures made with SKA precursors, with a focus on the outcomes of a dedicated search for low-angular diameter radio rings using MeerKAT data from the SARAO MeerKAT Galactic Plane Survey and the Galactic Centre mosaic. This work has unveiled over 160 new radio rings of uncertain nature. This unexplored sample holds strong potential for the discovery of large number of evolved star candidates. I will describe the sample's general properties and the results of an initial multiwavelength assessment, which has allowed to identify a subset of the rings as potential mass-loss relics around new Luminous Blue Variable candidates. Finally, I will discuss detection prospects as SKA precursor capabilities continue to expand, and how this work and future follow-ups will contribute to a more complete census of evolved stars in the Milky Way.
| Topics | Cradle of Life & Our Galaxy |
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