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05-02-2021
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EVN Seminar (Friday 5 at 15:00): Distance of optically-obscured evolved stars

Submitter: Benito Marcote on behalf of the EVN Seminars O.C.
Description: A new edition of the EVN Online Seminars will take place on Friday February 5 at 15:00.

Sandra Etoka will be our speaker, and her talk would be focused on how masers can be used to measure the distance of evolved stars, where the optical emission is typically obscured and thus Gaia cannot provide parallaxes.


For a summary of the talk:

As intermediate-mass stars head towards their final fate, they pass through the red-giant stage where they experience an increase of mass loss. This induces the creation of a circumstellar envelope of dust and gas. By the very end of this evolutionary stage, the amount of dust in the circumstellar envelope of a good fraction of these evolved stars is such that it blocks optical radiation, turning them into so-called OH/IR stars. These precursors of planetary nebulae are commonly observed throughout the Galaxy and are also observed in the Magellanic Clouds. Since optically thick, measurements of their distances using optical parallaxes as e.g. delivered by GAIA, is not possible. This issue can be circumvented thanks to maser emission. As their name gives it away, the physical conditions turn out to be ideal for a strong (1612-MHz) OH maser emission to be produced in the outer layers of the radially-expanding spherical circumstellar envelope of OH/IR stars. I will present how, combining single-dish monitoring and interferometric mapping of this OH maser emission, the "phase-lag method" allows us to measure their distance.

Please join via Zoom (Room ID: 885 4531 2932) or via YouTube (where the seminar will be streamed in real-time and stored for later views). For further information on the EVN Seminars, please look at the EVN website.
Copyright: JIVE
 
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