EX008
VLBI Astrometry of HD 179821: Supergiant or Post-AGB Star?
HD 179821 is an enigmatic evolved star with detached cool dust shell. It possesses properties of both a post-AGB star and a supergiant. By now, there is no evidence that can distinctly define its nature and evolution status. The two hypotheses are based on an undermined distance, 1 kpc for post-AGB star or 6 kpc for supergiant. We propose multi-epoch phase-referencing EVN observations of 1.6 GHz OH maser emission toward HD 179821, in order to measure its parallax with an uncertainty of 0.05 mas. VLBI astrometry of OH masers around HD 179821 would help us: (1) determine an accurate distance to answer the question: whether HD 179821 is a supergiant or a post-AGB star? (2) study the 3-dimensional kinematics of circumstellar using OH masers as probes. (3) verify Gaia parallaxes of evolved stars.
Observation pages at the EVN archive:
Context for this dataThis data is part of the archive of VLBI data maintained by JIVE on behalf of the EVN, a network of radio telescopes located primarily in Europe and Asia, with additional antennas in South Africa. The EVN archive itself has the DOI https://doi.org/10.17616/R3Z197