Characterizing TESS-Identified Quadruple and Higher Order Eclipsing Binaries: I. Speckle Imaging with DSSI and HRCam

TL;DR

This study uses speckle imaging to analyze quadruple and higher order eclipsing binaries identified by TESS, revealing their multiplicity, resolving some into separate sources, and providing data to better understand their system architectures.

Contribution

First comprehensive speckle imaging follow-up of TESS-identified quadruple and higher order eclipsing binaries, improving characterization of their multiplicity and system configurations.

Findings

Nearly 60% of observed systems are partly resolved into two sources.

Resolved systems show inflated Gaia parallax errors and large RUWE.

Some unresolved systems have upper limits on separation, indicating tight configurations.

Abstract

NASA's TESS mission has unveiled a plethora of eclipsing binaries (EBs), among them hundreds of triples and higher order, hierarchical systems. These complex targets require follow-up observations to enable full characterization of system architectures and identify the most compact multiples expected to undergo the most dramatic dynamical evolution. We report first results from a long-term effort to perform such follow-up, focusing here on multi-band speckle imaging of a majority, 57, of the sample of 97 quadruple and higher order eclipsing binaries (Q+EBs) identified via TESS light curves by V. B. Kostov et al. (2022). Diffraction-limited imaging with the Differential Speckle Survey Instrument (DSSI) on the ARC 3.5-meter telescope and HRCam on the SOAR 4.1-m telescope reveals nearly 60% of the 57 to resolve into two sources separated by $\geq$ 0.03 arcseconds. For these partly resolved systems, we report derived characteristics (e.g., relative position angle, angular separation, and magnitude differences in multiple passbands) from the speckle imaging. We find those Q+EBs partly resolved with 4-m class telescopes to have significantly inflated Gaia parallax errors and large Gaia RUWE, particularly for systems with separations comparable to Gaia's resolution limit (~0.6 arcseconds). For unresolved systems we report upper limits on angular and linear projected separations. We find two partly resolved Q+EBs with wide linear separations having eclipse timing variations that are therefore candidates of higher than quadruple multiplicity. Finally, we demonstrate how speckle imaging of resolved Q+EBs during an eclipse can clarify which speckle-resolved Q+EB subsystem is associated with a particular set of TESS eclipses.