The five largest satellites of Uranus: astrometric observations spread over 29 years at the Pico dos Dias Observatory

TL;DR

This study provides a comprehensive astrometric dataset of Uranus's five largest satellites over 29 years, improving orbital models and understanding of the Uranian system through reanalyzed observations and Gaia EDR3 reference stars.

Contribution

It offers an extensive, reanalyzed astrometric dataset spanning nearly three decades, utilizing Gaia EDR3 stars for higher accuracy and larger data coverage than previous works.

Findings

Detected a possible offset in the Uranian system barycenter position.

Achieved high-precision satellite positions with average errors around 50 milliarcseconds.

Results can enhance dynamical models of Uranus's satellites and orbit.

Abstract

We present the astrometry of the five largest satellites of Uranus from observations spread over almost three decades with photographic plates and CCDs (mainly), taken at the Pico dos Dias Observatory - Brazil. All positions presented here are obtained from the reanalysis of measurements and images used in previous publications. Reference stars are those from the Gaia Early Data Release 3 (Gaia EDR3) allowing, in addition to a higher accuracy, a larger number of positions of the largest satellites as compared to our previous works. From 1982 to 1987, positions were obtained from photographic plates. From 1989 to 2011, CCDs were used. On average, we obtained $\Delta\alpha{\rm cos}\delta=-11~(\pm52)$ milli-arcseconds and $\Delta\delta=-14~(\pm43)$ milli-arcseconds for the differences in the sense observation minus ephemerides (DE435$+$ura111). Comparisons with different ephemerides (DE440, INPOP21a, INPOP19a and NOE-7-2013-MAIN) and results from stellar occultations indicate a possible offset in the (Solar System) barycentric position of the Uranian system barycenter. Overall, our results are useful to improve dynamical models of the Uranian largest satellites as well as the orbit of Uranus.