UrHip Proper Motion Catalog

TL;DR

The UrHip catalog combines Hipparcos and URAT1 data to significantly improve proper motion accuracy for over 67,000 stars in the northern hemisphere and identifies potential binary systems through astrometric analysis.

Contribution

This work presents a new proper motion catalog that enhances accuracy and detects binary candidates by combining data from Hipparcos and URAT1, with a longer baseline than previous catalogs.

Findings

Proper motions improved by a factor of ~3.

Identification of stars with large proper motion discrepancies.

Potential binary candidates detected through astrometric differences.

Abstract

Proper motions are computed and collected in a catalog using the Hipparcos positions (epoch 1991.25) and URAT1 positions (epoch 2012.3 to 2014.6). The goal is to obtain a significant improvement on the proper motion accuracy of single stars in the northern hemisphere, and to identify new astrometric binaries perturbed by orbital motion. For binaries and multiple systems, the longer baseline of Tycho2 (~ 100 yr) makes it more reliable despite its larger formal uncertainties. The resulting proper motions obtained for 67,340 stars have a consequent gain in accuracy by a factor of ~ 3 compared to Hipparcos. Comparison between UrHip and Hipparcos shows that they are reasonably close, but also reveals stars with large discrepant proper motions, a fraction of which are potential binary candidates.