What the study found
VLBI and Gaia DR3 astrometric measurements for 43 Galactic long period variable stars were generally consistent within uncertainties for about half the sample. Gaia DR3 parallaxes tended to be slightly smaller than the VLBI values, and the two methods showed different uncertainty behavior.
Why the authors say this matters
The study suggests that VLBI and Gaia astrometry are complementary for measuring distances and motions of long period variable stars. The authors conclude that VLBI is more effective for stars with parallaxes below about 2 mas, which correspond to distances beyond 500 pc.
What the researchers tested
The researchers compared astrometric measurements from very long baseline interferometry, a radio technique that uses widely separated telescopes to measure positions very precisely, with Gaia DR3 measurements for 43 Galactic long period variable stars. They examined both parallaxes and proper motions.
What worked and what didn't
Parallaxes from the two methods matched within uncertainties for about half the sample, but Gaia DR3 values were generally slightly smaller than VLBI values. VLBI parallax errors increased as parallax increased, while Gaia DR3 errors stayed nearly constant; as a result, VLBI performed better for parallaxes below about 2 mas.
Proper motions showed general agreement, with a 2-sigma dispersion of about 13 km s−1, which the abstract says is consistent with typical asymptotic giant branch outflow velocities. The dispersion of parallax residuals was slightly larger for sources with pulsation periods around one year.
What to keep in mind
The abstract does not give details on the size or causes of the Gaia-VLBI offset beyond noting that it matches previously reported systematic offsets. It also does not describe any limitations beyond the sample size and the observed dependence on pulsation period.
Key points
- VLBI and Gaia DR3 parallaxes were generally consistent within uncertainties for about half of 43 Galactic long period variable stars.
- Gaia DR3 parallaxes tended to be slightly smaller than VLBI parallaxes.
- VLBI parallax errors increased with increasing parallax, while Gaia DR3 errors stayed nearly constant.
- VLBI was more effective for parallaxes smaller than about 2 mas, or distances beyond 500 pc.
- Proper motions agreed generally, with a 2-sigma dispersion of about 13 km s−1.
- Parallax residuals were slightly more dispersed for stars with pulsation periods around one year.
Disclosure
- Research title:
- VLBI and Gaia agree on many long-period variable star distances
- Authors:
- Akiharu Nakagawa, Tomoharu Kurayama, Hiroshi Sudou, Gábor Orosz
- Institutions:
- Kagoshima University, Teikyo University of Science, Teikyo University, Sendai National College of Technology, Joint Institute for VLBI ERIC
- Publication date:
- 2026-03-30
- OpenAlex record:
- View
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