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/

Zendy Plus

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

Zendy Tools

Zendy Open

The main-line OH masers around 4 AGB stars have been observed with the NRAOVery Long Baseline Array (VLBA) at 8 epochs over a period of 2.5 years. Using aphase referencing technique, the position of the most compact maser spot ofeach star was monitored with respect to two extragalactic reference sources.For U Her and W Hya, we observe the most blue-shifted maser spot, while for RCas and S CrB we only detect a compact red-shifted maser spot. We managed todetermine an accurate proper motion and parallax for U Her, R Cas and S CrB,while additional motion of the compact blue-shifted maser of W Hya is shown topossibly be related to the stellar pulsation. The motion and radio position arecompared with the stellar trajectory and absolute optical position determinedby the Hipparcos satellite. For U Her and W Hya, the most blue-shifted maser isconsistent with the amplified stellar image. The new distances are comparedwith several published P--L relations, and in this respect the VLBI distancesseem an improvement upon the Hipparcos distances.Comment: 13 pages, 12 figures; accepted by A&

VLBI astrometry of circumstellar OH masers: Proper motions and parallaxes of four AGB stars