Astrometry

Evaluating the Impact of Optical Axis Stability on Exoplanet Detection

We evaluated how optical-axis stability affects microarcsecond-level angular-distance measurements for exoplanet astrometry, finding a 68 mas stability requirement.

Dong-Jie Tan, Jia-Cheng Liu, Zi Zhu, Niu Liu

Evaluating the Impact of Optical Axis Stability on Exoplanet Detection

Comparison of multifrequency positions of extragalactic sources from ICRF3 and Gaia EDR3

Comparison of ICRF3 and Gaia EDR3 positions and the influence of radio source structure.

Niu Liu, Sébastien B. Lambert, Patrick Charlot, Zi Zhu, Jia-Cheng Liu, Nan Jiang, Xiao-Sheng Wan, Cheng-Yu Ding

Parsec-scale alignments of radio–optical offsets with jets in AGNs from multifrequency geodetic VLBI, Gaia EDR3, and the MOJAVE program

Multiwavelength VLBI–Gaia astrometry reveals alignments between radio–optical offsets and parsec-scale AGN jets, consistent with a core–jet scenario.

Sébastien Lambert, Niu Liu, E. F. Arias, C. Barache, J. Souchay, F. Taris, Jia-Cheng Liu, Zi Zhu

Parsec-scale alignments of radio–optical offsets with jets in AGNs from multifrequency geodetic VLBI, Gaia EDR3, and the MOJAVE program

Is there an interest in bringing Gaia-CRF into VLBI data reduction?

An exploratory study of using Gaia-CRF2 in VLBI data reduction examines how celestial-frame constraints affect source positions, Earth orientation parameters, and the terrestrial reference frame.

Niu Liu, Sébastien Lambert, Zi Zhu, Jia-Cheng Liu

Is there an interest in bringing Gaia-CRF into VLBI data reduction?

The Galactic Aberration and Its Impact on Astronomical Reference Frames

Review of Galactic aberration (~5 μas/yr) and its consequences for ICRF/Gaia frames and EOP (~1 μas/yr precession corrections).

Jia-Cheng Liu, Niu Liu

The Galactic Aberration and Its Impact on Astronomical Reference Frames

Revisiting astrometric parameters of quasars in Gaia-CRF2

Quality analysis of Gaia-CRF2 quasar astrometry using visibility periods and correlation coefficients; quasars with 13–16 visibility periods yield the most reliable parameters.

Cheng-Yu Ding, Zi Zhu, Jia-Cheng Liu, Niu Liu

Revisiting astrometric parameters of quasars in Gaia-CRF2

Systematics and accuracy of VLBI astrometry: A comparison with Gaia Data Release 2

ICRF3 vs Gaia DR2: S/X agrees at ~30 μas globally; K and X/Ka show zonal systematics, notably a >200 μas Z-glide in X/Ka.

Niu Liu, Sébastien B. Lambert, Zi Zhu, Jia-Cheng Liu

Systematics and accuracy of VLBI astrometry: A comparison with Gaia Data Release 2