Determining the Orientation Parameters of the ICRS/UCAC2 System Using the Kharkov Catalog of Absolute Stellar Proper Motions

TL;DR

This paper determines the orientation parameters of the ICRS/UCAC2 system by analyzing proper motions from the Kharkov XPM catalog, comparing positions over decades, and using galaxies to set the zero point, resulting in residual rotation estimates.

Contribution

It introduces a new method for calibrating the ICRS/UCAC2 system's orientation using the Kharkov XPM catalog and extragalactic sources, refining the residual rotation parameters.

Findings

Residual rotation vector components: (-0.06, 0.17, -0.84) mas/yr.

Zero point of proper motions established with 1.45 million galaxies.

Residual rotation parameters determined with about 1 million faint UCAC2 stars.

Abstract

The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their positions in the 2MASS and USNO--A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about 17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45 million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: \omega_{x,y,z}=(-0.06,0.17,-0.84)+/-(0.15,0.14,0.14) mas yr^{-1}. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R_{UCAC2}>16^m and J>14^m.7,for which the color and magnitude equation effects are negligible.