Speckle Interferometry at SOAR in 2021

Abstract The speckle interferometry program at the 4.1 m Southern Astrophysical Research Telescope (SOAR), which started in 2008, now has accumulated over 30,300 individual observations of 12,700 distinct targets. Its main goal is to monitor orbital motion close binaries, including members high-order hierarchies and low-mass dwarfs solar neighborhood. results from 2021 are published here, totaling 2623 measurements 2123 resolved pairs nonresolutions 763 median measured separation 0.?21, 75 were closer than 30 mas. calibration scale orientation based on 103 wide with well-modeled motion. These calibrators compared latest Gaia data release, minor (0.5%) systematic errors rectified, resulting accurate relative positions typical order 1 Using these new measurements, orbits 282 binaries determined here (54 first determinations 228 corrections). We for time 50 pairs, subsystems known binaries. A list 94 likely spurious unresolved SOAR (mostly Hipparcos binaries) also given.