Speckle Interferometry of 25 Gaia Two-Parameter Potential Binaries

TL;DR

This study used speckle interferometry to observe 25 Gaia two-parameter stars, identifying companions and analyzing Gaia's measurement errors, highlighting limitations and potential improvements in future data releases.

Contribution

First application of speckle interferometry to Gaia two-parameter stars revealing companions and assessing Gaia's measurement discrepancies.

Findings

Identified companions for all seven stars without Gaia companions within 5".

Found close agreement in separations for 13 stars with known Gaia companions.

Detected discrepancies in position angles and separations for some stars.

Abstract

Gaia two-parameter (G2P) stars have cumulative errors in parallax and proper motion so great that only their mean positions were reported in DR3. One potential cause of these high errors is another star as indicated by two intensity peaks in the scans. Speckle interferometry astrometric measurements of 25 G2P stars with high multi-peak percentages were obtained with the 1.5m telescope at Mt. Wilson Observatory. Of the 25 observed G2P stars, seven had no reported Gaia companions within 5.0". We found nearby companions for all seven. The 18 other G2P stars had known Gaia companions within 2.0". Of these, 13 had separations that agreed closely with the speckle measurements but with some discrepancy in position angles, three stars did not agree in either separation or position angle and no companion was detected for the remaining two. Although some of these issues may be resolved in DR4 or DR5, others may be inherent limitations of Gaia capabilities that speckle interferometry observations may be able to fill.