Speckle Interferometry at SOAR in 2021

TL;DR

This paper reports on speckle interferometry observations at SOAR in 2021, providing high-precision measurements of binary star systems, including new discoveries, orbit determinations, and calibration improvements aligned with Gaia data.

Contribution

It presents the 2021 speckle interferometry results, including 2,623 measurements, new binary discoveries, orbit calculations, and calibration enhancements using Gaia data.

Findings

Resolved 50 new binary pairs for the first time.

Determined or refined orbits for 282 binaries.

Achieved typical measurement errors of about 1 milliarcsecond.

Abstract

The speckle interferometry program at the the 4.1 m Southern Astrophysical Research Telescope (SOAR), started in 2008, now accumulated over 30,300 individual observations of 12,700 distinct targets. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and low-mass dwarfs in the solar neighborhood. The results from 2021 are published here, totaling 2,623 measurements of 2,123 resolved pairs and non-resolutions of 763 targets. The median measured separation is 0.21", and 75 pairs were closer than 30 mas. The calibration of scale and orientation is based on the observations of 103 wide pairs with well-modeled motion. These calibrators are compared to the latest Gaia data release, and minor (0.5%) systematic errors were rectified, resulting in accurate relative positions with typical errors on the order of 1 mas. Using these new measurements, orbits of 282 binaries are determined here (54 first determinations and 228 corrections). We resolved for the first time 50 new pairs, including subsystems in known binaries. A list of 94 likely spurious pairs unresolved at SOAR (mostly close Hipparcos binaries) is also given.